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• Synthesis of a helical boron-doped PAH by post-functionalization of 3,9-diboraperylene. Mützel, Carina; Shoyama, Kazutaka; Krause, Ana-Maria; Würthner, Frank. In Org. Chem. Front., 11(10), pp. 2747–2755. 2024.
  • [ Abstract ]
  • [ BibTeX ]
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  We present herein the post-functionalization of doubly boron-doped polycyclic aromatic hydrocarbons (PAHs) by various aryl substituents, namely the syntheses of a series of (2,8,)3,9-aryl-substituted 3,9-diboraperylenes via boron-substitution of (2,8-diaryl-)3,9-dihydroxy-3,9-diboraperylenes. These new boron-doped PAHs exhibit two reversible reductions with a remarkably facile first reduction between E = −1.04 and −1.13 V vs. Fc+/Fc. Friedel–Crafts cyclization of the 2-isopropenylnaphthyl-substituted derivative afforded a helical boron-doped polycyclic aromatic hydrocarbon that is endowed with a low LUMO level, high absorption coefficients and fluorescence (ΦF = 0.73), combined with a one-dimensional π–π stacking interaction in the solid state.

  @article{D4QO00421C, abstract = {We present herein the post-functionalization of doubly boron-doped polycyclic aromatic hydrocarbons (PAHs) by various aryl substituents, namely the syntheses of a series of (2,8,)3,9-aryl-substituted 3,9-diboraperylenes via boron-substitution of (2,8-diaryl-)3,9-dihydroxy-3,9-diboraperylenes. These new boron-doped PAHs exhibit two reversible reductions with a remarkably facile first reduction between E = −1.04 and −1.13 V vs. Fc+/Fc. Friedel–Crafts cyclization of the 2-isopropenylnaphthyl-substituted derivative afforded a helical boron-doped polycyclic aromatic hydrocarbon that is endowed with a low LUMO level, high absorption coefficients and fluorescence (ΦF = 0.73), combined with a one-dimensional π–π stacking interaction in the solid state.}, author = {Mützel, Carina and Shoyama, Kazutaka and Krause, Ana-Maria and Würthner, Frank}, journal = {Org. Chem. Front.}, keywords = {myown}, number = 10, pages = {2747-2755}, publisher = {The Royal Society of Chemistry}, title = {Synthesis of a helical boron-doped PAH by post-functionalization of 3{,}9-diboraperylene}, volume = 11, year = 2024 }

  %0 Journal Article %1 D4QO00421C %A Mützel, Carina %A Shoyama, Kazutaka %A Krause, Ana-Maria %A Würthner, Frank %D 2024 %I The Royal Society of Chemistry %J Org. Chem. Front. %N 10 %P 2747-2755 %R 10.1039/D4QO00421C %T Synthesis of a helical boron-doped PAH by post-functionalization of 3,9-diboraperylene %U http://dx.doi.org/10.1039/D4QO00421C %V 11 %X We present herein the post-functionalization of doubly boron-doped polycyclic aromatic hydrocarbons (PAHs) by various aryl substituents, namely the syntheses of a series of (2,8,)3,9-aryl-substituted 3,9-diboraperylenes via boron-substitution of (2,8-diaryl-)3,9-dihydroxy-3,9-diboraperylenes. These new boron-doped PAHs exhibit two reversible reductions with a remarkably facile first reduction between E = −1.04 and −1.13 V vs. Fc+/Fc. Friedel–Crafts cyclization of the 2-isopropenylnaphthyl-substituted derivative afforded a helical boron-doped polycyclic aromatic hydrocarbon that is endowed with a low LUMO level, high absorption coefficients and fluorescence (ΦF = 0.73), combined with a one-dimensional π–π stacking interaction in the solid state.
• Polarized, color-selective and semi-transparent organic photodiode of aligned merocyanine H-aggregates. Schembri, Tim; Kolb, Leonhard; Stolte, Matthias; Würthner, Frank. In J. Mater. Chem. C, 12(14), pp. 4948–4953. 2024.
  • [ Abstract ]
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  Highly anisotropic thin films of H-type coupled dipolar merocyanines with large dichroic ratios of over 50 were deposited by solution shearing. These layers were incorporated into simultaneously color- and polarization-selective organic photodiodes. Using a transparent non-fullerene acceptor, polarization-sensitive planar-heterojunction devices with an average visible transmittance of 93% were obtained.

  @article{D4TC00678J, abstract = {Highly anisotropic thin films of H-type coupled dipolar merocyanines with large dichroic ratios of over 50 were deposited by solution shearing. These layers were incorporated into simultaneously color- and polarization-selective organic photodiodes. Using a transparent non-fullerene acceptor{,} polarization-sensitive planar-heterojunction devices with an average visible transmittance of 93% were obtained.}, author = {Schembri, Tim and Kolb, Leonhard and Stolte, Matthias and Würthner, Frank}, journal = {J. Mater. Chem. C}, keywords = {myown}, number = 14, pages = {4948-4953}, publisher = {The Royal Society of Chemistry}, title = {Polarized{,} color-selective and semi-transparent organic photodiode of aligned merocyanine H-aggregates}, volume = 12, year = 2024 }

  %0 Journal Article %1 D4TC00678J %A Schembri, Tim %A Kolb, Leonhard %A Stolte, Matthias %A Würthner, Frank %D 2024 %I The Royal Society of Chemistry %J J. Mater. Chem. C %N 14 %P 4948-4953 %R 10.1039/D4TC00678J %T Polarized, color-selective and semi-transparent organic photodiode of aligned merocyanine H-aggregates %U http://dx.doi.org/10.1039/D4TC00678J %V 12 %X Highly anisotropic thin films of H-type coupled dipolar merocyanines with large dichroic ratios of over 50 were deposited by solution shearing. These layers were incorporated into simultaneously color- and polarization-selective organic photodiodes. Using a transparent non-fullerene acceptor, polarization-sensitive planar-heterojunction devices with an average visible transmittance of 93% were obtained.
• A Terrylene Bisimide based Universal Host for Aromatic Guests to Derive Contact Surface‐Dependent Dispersion Energies. Rühe, Jessica; Rajeevan, Megha; Shoyama, Kazutaka; Swathi, Rotti Srinivasamurthy; Würthner, Frank. In Angew. Chem. Int. Ed., 63(17). 2024.
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  π–π interactions are among the most important intermolecular interactions in supramolecular systems. Here we determine experimentally a universal parameter for their strength that is simply based on the size of the interacting contact surfaces. Toward this goal we designed a new cyclophane based on terrylene bisimide (TBI) π-walls connected by para-xylylene spacer units. With its extended π-surface this cyclophane proved to be an excellent and universal host for the complexation of π-conjugated guests, including small and large polycyclic aromatic hydrocarbons (PAHs) as well as dye molecules. The observed binding constants range up to 108 M−1 and show a linear dependence on the 2D area size of the guest molecules. This correlation can be used for the prediction of binding constants and for the design of new host–guest systems based on the herewith derived universal Gibbs interaction energy parameter of 0.31 kJ/molÅ2 in chloroform.

  @article{R_he_2024, abstract = {π–π interactions are among the most important intermolecular interactions in supramolecular systems. Here we determine experimentally a universal parameter for their strength that is simply based on the size of the interacting contact surfaces. Toward this goal we designed a new cyclophane based on terrylene bisimide (TBI) π-walls connected by para-xylylene spacer units. With its extended π-surface this cyclophane proved to be an excellent and universal host for the complexation of π-conjugated guests, including small and large polycyclic aromatic hydrocarbons (PAHs) as well as dye molecules. The observed binding constants range up to 108 M−1 and show a linear dependence on the 2D area size of the guest molecules. This correlation can be used for the prediction of binding constants and for the design of new host–guest systems based on the herewith derived universal Gibbs interaction energy parameter of 0.31 kJ/molÅ2 in chloroform.}, author = {Rühe, Jessica and Rajeevan, Megha and Shoyama, Kazutaka and Swathi, Rotti Srinivasamurthy and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {03}, number = 17, publisher = {Wiley}, title = {A Terrylene Bisimide based Universal Host for Aromatic Guests to Derive Contact Surface‐Dependent Dispersion Energies}, volume = 63, year = 2024 }

  %0 Journal Article %1 R_he_2024 %A Rühe, Jessica %A Rajeevan, Megha %A Shoyama, Kazutaka %A Swathi, Rotti Srinivasamurthy %A Würthner, Frank %D 2024 %I Wiley %J Angew. Chem. Int. Ed. %N 17 %R 10.1002/anie.202318451 %T A Terrylene Bisimide based Universal Host for Aromatic Guests to Derive Contact Surface‐Dependent Dispersion Energies %U http://dx.doi.org/10.1002/anie.202318451 %V 63 %X π–π interactions are among the most important intermolecular interactions in supramolecular systems. Here we determine experimentally a universal parameter for their strength that is simply based on the size of the interacting contact surfaces. Toward this goal we designed a new cyclophane based on terrylene bisimide (TBI) π-walls connected by para-xylylene spacer units. With its extended π-surface this cyclophane proved to be an excellent and universal host for the complexation of π-conjugated guests, including small and large polycyclic aromatic hydrocarbons (PAHs) as well as dye molecules. The observed binding constants range up to 108 M−1 and show a linear dependence on the 2D area size of the guest molecules. This correlation can be used for the prediction of binding constants and for the design of new host–guest systems based on the herewith derived universal Gibbs interaction energy parameter of 0.31 kJ/molÅ2 in chloroform.
• High Sensitivity and Ultra‐Broad‐Range NH3 Sensor Arrays by Precise Control of Step Defects on The Surface of Cl2‐NDI Single Crystals. Lu, Bin; Stolte, Matthias; Liu, Dong; Zhang, Xiaojing; Zhao, Lihui; Tian, Liehao; Frisbie, C. Daniel; Würthner, Frank; Tao, Xutang; He, Tao. In Adv. Sci. 2024.
  • [ Abstract ]
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  Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface-to-volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade-off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n-type single crystal. Step edges, serving as adsorption sites with electron-deficient properties, are well-defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap-like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two-terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb–to–% level detection range and a convenient linear relation between sheet conductance and semi-log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing.

  @article{Lu_2024, abstract = {Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface-to-volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade-off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n-type single crystal. Step edges, serving as adsorption sites with electron-deficient properties, are well-defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap-like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two-terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb–to–% level detection range and a convenient linear relation between sheet conductance and semi-log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing.}, author = {Lu, Bin and Stolte, Matthias and Liu, Dong and Zhang, Xiaojing and Zhao, Lihui and Tian, Liehao and Frisbie, C. Daniel and Würthner, Frank and Tao, Xutang and He, Tao}, journal = {Adv. Sci.}, keywords = {myown}, month = {02}, publisher = {Wiley}, title = {High Sensitivity and Ultra‐Broad‐Range NH3 Sensor Arrays by Precise Control of Step Defects on The Surface of Cl2‐NDI Single Crystals}, year = 2024 }

  %0 Journal Article %1 Lu_2024 %A Lu, Bin %A Stolte, Matthias %A Liu, Dong %A Zhang, Xiaojing %A Zhao, Lihui %A Tian, Liehao %A Frisbie, C. Daniel %A Würthner, Frank %A Tao, Xutang %A He, Tao %D 2024 %I Wiley %J Adv. Sci. %R 10.1002/advs.202308036 %T High Sensitivity and Ultra‐Broad‐Range NH3 Sensor Arrays by Precise Control of Step Defects on The Surface of Cl2‐NDI Single Crystals %U http://dx.doi.org/10.1002/advs.202308036 %X Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface-to-volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade-off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n-type single crystal. Step edges, serving as adsorption sites with electron-deficient properties, are well-defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap-like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two-terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb–to–% level detection range and a convenient linear relation between sheet conductance and semi-log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing.
• A Water-Stable Boronate Ester Cage. Kirchner, Philipp H.; Schramm, Louis; Ivanova, Svetlana; Shoyama, Kazutaka; Würthner, Frank; Beuerle, Florian. In J. Am. Chem. Soc., 146(8), pp. 5305–5315. 2024.
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  The reversible condensation of catechols and boronic acids to boronate esters is a paradigm reaction in dynamic covalent chemistry. However, facile backward hydrolysis is detrimental for stability and has so far prevented applications for boronate-based materials. Here, we introduce cubic boronate ester cages 6 derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding, dynamic exchange at the Lewis acidic boron sites is feasible only under acid or base catalysis but fully prevented at neutral conditions. For the first time, boronate ester cages 6 tolerate substantial amounts of water or alcohols both in solution and solid state. The unprecedented applicability of these materials under ambient and aqueous conditions is showcased by efficient encapsulation and on-demand release of β-carotene dyes and heterogeneous water oxidation catalysis after the encapsulation of ruthenium catalysts.

  @article{Kirchner_2024, abstract = {The reversible condensation of catechols and boronic acids to boronate esters is a paradigm reaction in dynamic covalent chemistry. However, facile backward hydrolysis is detrimental for stability and has so far prevented applications for boronate-based materials. Here, we introduce cubic boronate ester cages 6 derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding, dynamic exchange at the Lewis acidic boron sites is feasible only under acid or base catalysis but fully prevented at neutral conditions. For the first time, boronate ester cages 6 tolerate substantial amounts of water or alcohols both in solution and solid state. The unprecedented applicability of these materials under ambient and aqueous conditions is showcased by efficient encapsulation and on-demand release of β-carotene dyes and heterogeneous water oxidation catalysis after the encapsulation of ruthenium catalysts.}, author = {Kirchner, Philipp H. and Schramm, Louis and Ivanova, Svetlana and Shoyama, Kazutaka and Würthner, Frank and Beuerle, Florian}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {02}, number = 8, pages = {5305–5315}, publisher = {American Chemical Society (ACS)}, title = {A Water-Stable Boronate Ester Cage}, volume = 146, year = 2024 }

  %0 Journal Article %1 Kirchner_2024 %A Kirchner, Philipp H. %A Schramm, Louis %A Ivanova, Svetlana %A Shoyama, Kazutaka %A Würthner, Frank %A Beuerle, Florian %D 2024 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 8 %P 5305–5315 %R 10.1021/jacs.3c12002 %T A Water-Stable Boronate Ester Cage %U http://dx.doi.org/10.1021/jacs.3c12002 %V 146 %X The reversible condensation of catechols and boronic acids to boronate esters is a paradigm reaction in dynamic covalent chemistry. However, facile backward hydrolysis is detrimental for stability and has so far prevented applications for boronate-based materials. Here, we introduce cubic boronate ester cages 6 derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding, dynamic exchange at the Lewis acidic boron sites is feasible only under acid or base catalysis but fully prevented at neutral conditions. For the first time, boronate ester cages 6 tolerate substantial amounts of water or alcohols both in solution and solid state. The unprecedented applicability of these materials under ambient and aqueous conditions is showcased by efficient encapsulation and on-demand release of β-carotene dyes and heterogeneous water oxidation catalysis after the encapsulation of ruthenium catalysts.
• Bioinspired Water Preorganization in Confined Space for Efficient Water Oxidation Catalysis in Metallosupramolecular Ruthenium Architectures. Noll, Niklas; Würthner, Frank. In Acc. Chem. Res., 57(10), pp. 1538–1549. 2024.
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  CONSPECTUS: Nature has established a sustainable way to maintain aerobic life on earth by inventing one of the most sophisticated biological processes, namely, natural photosynthesis, which delivers us with organic matter and molecular oxygen derived from the two abundant resources sunlight and water. The thermodynamically demanding photosynthetic water splitting is catalyzed by the oxygen-evolving complex in photosystem II (OEC-PSII), which comprises a distorted tetramanganese−calcium cluster (CaMn4O5) as catalytic core. As an ubiquitous concept for fine-tuning and regulating the reactivity of the active site of metalloenzymes, the surrounding protein domain creates a sophisticated environment that promotes substrate preorganization through secondary, noncovalent interactions such as hydrogen bonding or electrostatic interactions. Based on the high-resolution X-ray structure of PSII, several water channels were identified near the active site, which are filled with extensive hydrogen-bonding networks of preorganized water molecules, connecting the OEC with the protein surface. As an integral part of the outer coordination sphere of natural metalloenzymes, these channels control the substrate and product delivery, carefully regulate the proton flow by promoting pivotal proton-coupled electron transfer processes, and simultaneously stabilize short-lived oxidized intermediates, thus highlighting the importance of an ordered water network for the remarkable efficiency of the natural OEC. Transferring this concept from nature to the engineering of artificial metal catalysts for fuel production has fostered the fascinating field of metallosupramolecular chemistry by generating defined cavities that conceptually mimic enzymatic pockets. However, the application of supramolecular approaches to generate artificial water oxidation catalysts remained scarce prior to our initial reports, since such molecular design strategies for efficient activation of substrate water molecules in confined nanoenvironments were lacking. In this Account, we describe our research efforts on combining the state-of-the art Ru(bda) catalytic framework with structurally programmed ditopic ligands to guide the water oxidation process in defined metallosupramolecular assemblies in spatial proximity. We will elucidate the governing factors that control the quality of hydrogen-bonding water networks in multinuclear cavities of varying sizes and geometries to obtain high-performance, state-of-the-art water oxidation catalysts. Pushing the boundaries of artificial catalyst design, embedding a single catalytic Ru center into a well-defined molecular pocket enabled sophisticated water preorganization in front of the active site through an encoded basic recognition site, resulting in high catalytic rates comparable to those of the natural counterpart OEC-PSII. To fully explore their potential for solar fuel devices, the suitability of our metallosupramolecular assemblies was demonstrated under (electro)chemical and photocatalytic water oxidation conditions. In addition, testing the limits of structural diversity allowed the fabrication of self-assembled linear coordination oligomers as novel photocatalytic materials and long-range ordered covalent organic framework (COF) materials as recyclable and long-term stable solid-state materials for future applications.

  @article{Noll_2024, abstract = {CONSPECTUS: Nature has established a sustainable way to maintain aerobic life on earth by inventing one of the most sophisticated biological processes, namely, natural photosynthesis, which delivers us with organic matter and molecular oxygen derived from the two abundant resources sunlight and water. The thermodynamically demanding photosynthetic water splitting is catalyzed by the oxygen-evolving complex in photosystem II (OEC-PSII), which comprises a distorted tetramanganese−calcium cluster (CaMn4O5) as catalytic core. As an ubiquitous concept for fine-tuning and regulating the reactivity of the active site of metalloenzymes, the surrounding protein domain creates a sophisticated environment that promotes substrate preorganization through secondary, noncovalent interactions such as hydrogen bonding or electrostatic interactions. Based on the high-resolution X-ray structure of PSII, several water channels were identified near the active site, which are filled with extensive hydrogen-bonding networks of preorganized water molecules, connecting the OEC with the protein surface. As an integral part of the outer coordination sphere of natural metalloenzymes, these channels control the substrate and product delivery, carefully regulate the proton flow by promoting pivotal proton-coupled electron transfer processes, and simultaneously stabilize short-lived oxidized intermediates, thus highlighting the importance of an ordered water network for the remarkable efficiency of the natural OEC. Transferring this concept from nature to the engineering of artificial metal catalysts for fuel production has fostered the fascinating field of metallosupramolecular chemistry by generating defined cavities that conceptually mimic enzymatic pockets. However, the application of supramolecular approaches to generate artificial water oxidation catalysts remained scarce prior to our initial reports, since such molecular design strategies for efficient activation of substrate water molecules in confined nanoenvironments were lacking. In this Account, we describe our research efforts on combining the state-of-the art Ru(bda) catalytic framework with structurally programmed ditopic ligands to guide the water oxidation process in defined metallosupramolecular assemblies in spatial proximity. We will elucidate the governing factors that control the quality of hydrogen-bonding water networks in multinuclear cavities of varying sizes and geometries to obtain high-performance, state-of-the-art water oxidation catalysts. Pushing the boundaries of artificial catalyst design, embedding a single catalytic Ru center into a well-defined molecular pocket enabled sophisticated water preorganization in front of the active site through an encoded basic recognition site, resulting in high catalytic rates comparable to those of the natural counterpart OEC-PSII. To fully explore their potential for solar fuel devices, the suitability of our metallosupramolecular assemblies was demonstrated under (electro)chemical and photocatalytic water oxidation conditions. In addition, testing the limits of structural diversity allowed the fabrication of self-assembled linear coordination oligomers as novel photocatalytic materials and long-range ordered covalent organic framework (COF) materials as recyclable and long-term stable solid-state materials for future applications.}, author = {Noll, Niklas and Würthner, Frank}, journal = {Acc. Chem. Res.}, keywords = {myown}, month = {05}, number = 10, pages = {1538–1549}, publisher = {American Chemical Society (ACS)}, title = {Bioinspired Water Preorganization in Confined Space for Efficient Water Oxidation Catalysis in Metallosupramolecular Ruthenium Architectures}, volume = 57, year = 2024 }

  %0 Journal Article %1 Noll_2024 %A Noll, Niklas %A Würthner, Frank %D 2024 %I American Chemical Society (ACS) %J Acc. Chem. Res. %N 10 %P 1538–1549 %R 10.1021/acs.accounts.4c00148 %T Bioinspired Water Preorganization in Confined Space for Efficient Water Oxidation Catalysis in Metallosupramolecular Ruthenium Architectures %U http://dx.doi.org/10.1021/acs.accounts.4c00148 %V 57 %X CONSPECTUS: Nature has established a sustainable way to maintain aerobic life on earth by inventing one of the most sophisticated biological processes, namely, natural photosynthesis, which delivers us with organic matter and molecular oxygen derived from the two abundant resources sunlight and water. The thermodynamically demanding photosynthetic water splitting is catalyzed by the oxygen-evolving complex in photosystem II (OEC-PSII), which comprises a distorted tetramanganese−calcium cluster (CaMn4O5) as catalytic core. As an ubiquitous concept for fine-tuning and regulating the reactivity of the active site of metalloenzymes, the surrounding protein domain creates a sophisticated environment that promotes substrate preorganization through secondary, noncovalent interactions such as hydrogen bonding or electrostatic interactions. Based on the high-resolution X-ray structure of PSII, several water channels were identified near the active site, which are filled with extensive hydrogen-bonding networks of preorganized water molecules, connecting the OEC with the protein surface. As an integral part of the outer coordination sphere of natural metalloenzymes, these channels control the substrate and product delivery, carefully regulate the proton flow by promoting pivotal proton-coupled electron transfer processes, and simultaneously stabilize short-lived oxidized intermediates, thus highlighting the importance of an ordered water network for the remarkable efficiency of the natural OEC. Transferring this concept from nature to the engineering of artificial metal catalysts for fuel production has fostered the fascinating field of metallosupramolecular chemistry by generating defined cavities that conceptually mimic enzymatic pockets. However, the application of supramolecular approaches to generate artificial water oxidation catalysts remained scarce prior to our initial reports, since such molecular design strategies for efficient activation of substrate water molecules in confined nanoenvironments were lacking. In this Account, we describe our research efforts on combining the state-of-the art Ru(bda) catalytic framework with structurally programmed ditopic ligands to guide the water oxidation process in defined metallosupramolecular assemblies in spatial proximity. We will elucidate the governing factors that control the quality of hydrogen-bonding water networks in multinuclear cavities of varying sizes and geometries to obtain high-performance, state-of-the-art water oxidation catalysts. Pushing the boundaries of artificial catalyst design, embedding a single catalytic Ru center into a well-defined molecular pocket enabled sophisticated water preorganization in front of the active site through an encoded basic recognition site, resulting in high catalytic rates comparable to those of the natural counterpart OEC-PSII. To fully explore their potential for solar fuel devices, the suitability of our metallosupramolecular assemblies was demonstrated under (electro)chemical and photocatalytic water oxidation conditions. In addition, testing the limits of structural diversity allowed the fabrication of self-assembled linear coordination oligomers as novel photocatalytic materials and long-range ordered covalent organic framework (COF) materials as recyclable and long-term stable solid-state materials for future applications.
• Diboraperylene Diborinic Acid Self‐Assembly on Ag(111)—Kagome Flat Band Localized States Imaged by Scanning Tunneling Microscopy and Spectroscopy. Pan, Wun‐Chang; Mützel, Carina; Haldar, Soumyajyoti; Hohmann, Hendrik; Heinze, Stefan; Farrell, Jeffrey M.; Thomale, Ronny; Bode, Matthias; Würthner, Frank; Qi, Jing. In Angew. Chem. Int. Ed., 63(15). 2024.
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  Replacement of sp2-hybridized carbon in polycyclic aromatic hydrocarbons (PAHs) by boron affords electron-deficient π-scaffolds due to the vacant pz-orbital of three-coordinate boron with the potential for pronounced electronic interactions with electron-rich metal surfaces. Using a diboraperylene diborinic acid derivative as precursor and a controlled on-surface non-covalent synthesis approach, we report on a self-assembled chiral supramolecular kagome network on an Ag(111) surface stabilized by intermolecular hydrogen-bonding interactions at low temperature. Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal a flat band at ca. 0.33 eV above the Fermi level which is localized at the molecule center, in good agreement with tight-binding model calculations of flat bands characteristic for kagome lattices.

  @article{Pan_2024, abstract = {Replacement of sp2-hybridized carbon in polycyclic aromatic hydrocarbons (PAHs) by boron affords electron-deficient π-scaffolds due to the vacant pz-orbital of three-coordinate boron with the potential for pronounced electronic interactions with electron-rich metal surfaces. Using a diboraperylene diborinic acid derivative as precursor and a controlled on-surface non-covalent synthesis approach, we report on a self-assembled chiral supramolecular kagome network on an Ag(111) surface stabilized by intermolecular hydrogen-bonding interactions at low temperature. Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal a flat band at ca. 0.33 eV above the Fermi level which is localized at the molecule center, in good agreement with tight-binding model calculations of flat bands characteristic for kagome lattices.}, author = {Pan, Wun‐Chang and Mützel, Carina and Haldar, Soumyajyoti and Hohmann, Hendrik and Heinze, Stefan and Farrell, Jeffrey M. and Thomale, Ronny and Bode, Matthias and Würthner, Frank and Qi, Jing}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {02}, number = 15, publisher = {Wiley}, title = {Diboraperylene Diborinic Acid Self‐Assembly on Ag(111)—Kagome Flat Band Localized States Imaged by Scanning Tunneling Microscopy and Spectroscopy}, volume = 63, year = 2024 }

  %0 Journal Article %1 Pan_2024 %A Pan, Wun‐Chang %A Mützel, Carina %A Haldar, Soumyajyoti %A Hohmann, Hendrik %A Heinze, Stefan %A Farrell, Jeffrey M. %A Thomale, Ronny %A Bode, Matthias %A Würthner, Frank %A Qi, Jing %D 2024 %I Wiley %J Angew. Chem. Int. Ed. %N 15 %R 10.1002/anie.202400313 %T Diboraperylene Diborinic Acid Self‐Assembly on Ag(111)—Kagome Flat Band Localized States Imaged by Scanning Tunneling Microscopy and Spectroscopy %U http://dx.doi.org/10.1002/anie.202400313 %V 63 %X Replacement of sp2-hybridized carbon in polycyclic aromatic hydrocarbons (PAHs) by boron affords electron-deficient π-scaffolds due to the vacant pz-orbital of three-coordinate boron with the potential for pronounced electronic interactions with electron-rich metal surfaces. Using a diboraperylene diborinic acid derivative as precursor and a controlled on-surface non-covalent synthesis approach, we report on a self-assembled chiral supramolecular kagome network on an Ag(111) surface stabilized by intermolecular hydrogen-bonding interactions at low temperature. Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal a flat band at ca. 0.33 eV above the Fermi level which is localized at the molecule center, in good agreement with tight-binding model calculations of flat bands characteristic for kagome lattices.
• Isothermal Phase Transitions in Liquid Crystals Driven by Dynamic Covalent Chemistry. Martínez, Daniel; Schlossarek, Tim; Würthner, Frank; Soberats, Bartolome. In Angew. Chem. Int. Ed., 63(26). 2024.
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  The dynamic nature of calamitic liquid crystals is exploited to perform isothermal phase transitions driven by dynamic covalent chemistry. For this purpose, nematic (N) arrays based on aldehyde 1 were treated with different amines (A–E) in an on-surface process, which resulted in different isothermal phase transitions. These phase transformations were caused by in situ imination reactions and are dependent on the nature of the added amine. Transitions from the N to crystal (1A, 1E), isotropic (1B), and smectic (Sm) (1C, 1D) phases were achieved, while the resulting materials feature thermotropic liquid crystal behavior. A sequential trans- formation from the N 1 to the Sm 1C and then to the N 1B was achieved by coupling an imination to a transimination processes and adjusting the temperature. All of these processes were well characterized by micro- scopic, spectroscopic, and X-ray techniques, unlocking not only the constitutional but also the structural aspects of the phase transitions. This work provides new insights into designing constitutionally and structurally adaptable liquid crystal systems, paving the way toward the conception of programable evolutive pathways and adaptive materials.

  @article{Mart_nez_2024, abstract = {The dynamic nature of calamitic liquid crystals is exploited to perform isothermal phase transitions driven by dynamic covalent chemistry. For this purpose, nematic (N) arrays based on aldehyde 1 were treated with different amines (A–E) in an on-surface process, which resulted in different isothermal phase transitions. These phase transformations were caused by in situ imination reactions and are dependent on the nature of the added amine. Transitions from the N to crystal (1A, 1E), isotropic (1B), and smectic (Sm) (1C, 1D) phases were achieved, while the resulting materials feature thermotropic liquid crystal behavior. A sequential trans- formation from the N 1 to the Sm 1C and then to the N 1B was achieved by coupling an imination to a transimination processes and adjusting the temperature. All of these processes were well characterized by micro- scopic, spectroscopic, and X-ray techniques, unlocking not only the constitutional but also the structural aspects of the phase transitions. This work provides new insights into designing constitutionally and structurally adaptable liquid crystal systems, paving the way toward the conception of programable evolutive pathways and adaptive materials.}, author = {Martínez, Daniel and Schlossarek, Tim and Würthner, Frank and Soberats, Bartolome}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {05}, number = 26, publisher = {Wiley}, title = {Isothermal Phase Transitions in Liquid Crystals Driven by Dynamic Covalent Chemistry}, volume = 63, year = 2024 }

  %0 Journal Article %1 Mart_nez_2024 %A Martínez, Daniel %A Schlossarek, Tim %A Würthner, Frank %A Soberats, Bartolome %D 2024 %I Wiley %J Angew. Chem. Int. Ed. %N 26 %R 10.1002/anie.202403910 %T Isothermal Phase Transitions in Liquid Crystals Driven by Dynamic Covalent Chemistry %U http://dx.doi.org/10.1002/anie.202403910 %V 63 %X The dynamic nature of calamitic liquid crystals is exploited to perform isothermal phase transitions driven by dynamic covalent chemistry. For this purpose, nematic (N) arrays based on aldehyde 1 were treated with different amines (A–E) in an on-surface process, which resulted in different isothermal phase transitions. These phase transformations were caused by in situ imination reactions and are dependent on the nature of the added amine. Transitions from the N to crystal (1A, 1E), isotropic (1B), and smectic (Sm) (1C, 1D) phases were achieved, while the resulting materials feature thermotropic liquid crystal behavior. A sequential trans- formation from the N 1 to the Sm 1C and then to the N 1B was achieved by coupling an imination to a transimination processes and adjusting the temperature. All of these processes were well characterized by micro- scopic, spectroscopic, and X-ray techniques, unlocking not only the constitutional but also the structural aspects of the phase transitions. This work provides new insights into designing constitutionally and structurally adaptable liquid crystal systems, paving the way toward the conception of programable evolutive pathways and adaptive materials.
• Panchromatic light-harvesting antenna by supramolecular exciton band engineering for heteromeric dye foldamer. Schulz, Alexander; Fröhlich, Rebecca; Jayachandran, Ajay; Schneider, Franziska; Stolte, Matthias; Brixner, Tobias; Würthner, Frank. In Chem, pp. 2887–2900. 2024.
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  Natural photosystems accomplish panchromatic light absorption by different chromophores that are non-covalently embedded in protein matrices and mostly lack close dye-dye interactions. In this article, we introduce a light-harvesting (LH) system established by four different merocyanine dyes that are co-facially stacked by dipole-dipole interactions and a peptide-like backbone in a folded heteromer architecture to afford a panchromatic absorption band consisting of several strongly coupled exciton states. This exciton manifold allows for ultrafast and efficient energy transport in the artificial antenna. Furthermore, due to the tight stacking of the dyes in their folded state, non-radiative processes are slowed down, thereby increasing the lifetime of the excited state and the fluorescence quantum yield from <3% for the individual dyes up to 38% for the folda-heteromer. Together with the panchromatic absorption, this leads to a substantial improvement of the fluorescence brightness upon broadband excitation in comparison with its constituent chromophores.

  @article{Schulz_2024, abstract = {Natural photosystems accomplish panchromatic light absorption by different chromophores that are non-covalently embedded in protein matrices and mostly lack close dye-dye interactions. In this article, we introduce a light-harvesting (LH) system established by four different merocyanine dyes that are co-facially stacked by dipole-dipole interactions and a peptide-like backbone in a folded heteromer architecture to afford a panchromatic absorption band consisting of several strongly coupled exciton states. This exciton manifold allows for ultrafast and efficient energy transport in the artificial antenna. Furthermore, due to the tight stacking of the dyes in their folded state, non-radiative processes are slowed down, thereby increasing the lifetime of the excited state and the fluorescence quantum yield from <3% for the individual dyes up to 38% for the folda-heteromer. Together with the panchromatic absorption, this leads to a substantial improvement of the fluorescence brightness upon broadband excitation in comparison with its constituent chromophores.}, author = {Schulz, Alexander and Fröhlich, Rebecca and Jayachandran, Ajay and Schneider, Franziska and Stolte, Matthias and Brixner, Tobias and Würthner, Frank}, journal = {Chem}, keywords = {myown}, month = {06}, pages = {2887-2900}, publisher = {Elsevier BV}, title = {Panchromatic light-harvesting antenna by supramolecular exciton band engineering for heteromeric dye foldamer}, year = 2024 }

  %0 Journal Article %1 Schulz_2024 %A Schulz, Alexander %A Fröhlich, Rebecca %A Jayachandran, Ajay %A Schneider, Franziska %A Stolte, Matthias %A Brixner, Tobias %A Würthner, Frank %D 2024 %I Elsevier BV %J Chem %P 2887-2900 %R 10.1016/j.chempr.2024.05.023 %T Panchromatic light-harvesting antenna by supramolecular exciton band engineering for heteromeric dye foldamer %U http://dx.doi.org/10.1016/j.chempr.2024.05.023 %X Natural photosystems accomplish panchromatic light absorption by different chromophores that are non-covalently embedded in protein matrices and mostly lack close dye-dye interactions. In this article, we introduce a light-harvesting (LH) system established by four different merocyanine dyes that are co-facially stacked by dipole-dipole interactions and a peptide-like backbone in a folded heteromer architecture to afford a panchromatic absorption band consisting of several strongly coupled exciton states. This exciton manifold allows for ultrafast and efficient energy transport in the artificial antenna. Furthermore, due to the tight stacking of the dyes in their folded state, non-radiative processes are slowed down, thereby increasing the lifetime of the excited state and the fluorescence quantum yield from <3% for the individual dyes up to 38% for the folda-heteromer. Together with the panchromatic absorption, this leads to a substantial improvement of the fluorescence brightness upon broadband excitation in comparison with its constituent chromophores.
• Sequential Synthesis and Secondary Structure Analysis of Two Classes of Perylene Bisimide Oligomers. Teichmann, Ben; Liu, Bin; Hirsch, Marcel; Dubey, Rajeev K.; Würthner, Frank. In Org. Lett., 26(26), pp. 5544–5548. 2024.
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  An iterative step-by-step synthetic approach is employed to form perylene bisimide (PBI) oligomers of defined sizes by connecting the PBI units through their imide positions via a benzyl linker. The versatility of this approach was showcased by its successful implementation on two different PBI building blocks to achieve two separate series of oligomers (up to the pentamer) with modulated conformations: one with an open random coil oligomer and one with an H-type foldamer architecture.

  @article{Teichmann_2024, abstract = {An iterative step-by-step synthetic approach is employed to form perylene bisimide (PBI) oligomers of defined sizes by connecting the PBI units through their imide positions via a benzyl linker. The versatility of this approach was showcased by its successful implementation on two different PBI building blocks to achieve two separate series of oligomers (up to the pentamer) with modulated conformations: one with an open random coil oligomer and one with an H-type foldamer architecture.}, author = {Teichmann, Ben and Liu, Bin and Hirsch, Marcel and Dubey, Rajeev K. and Würthner, Frank}, journal = {Org. Lett.}, keywords = {myown}, month = {06}, number = 26, pages = {5544–5548}, publisher = {American Chemical Society (ACS)}, title = {Sequential Synthesis and Secondary Structure Analysis of Two Classes of Perylene Bisimide Oligomers}, volume = 26, year = 2024 }

  %0 Journal Article %1 Teichmann_2024 %A Teichmann, Ben %A Liu, Bin %A Hirsch, Marcel %A Dubey, Rajeev K. %A Würthner, Frank %D 2024 %I American Chemical Society (ACS) %J Org. Lett. %N 26 %P 5544–5548 %R 10.1021/acs.orglett.4c01928 %T Sequential Synthesis and Secondary Structure Analysis of Two Classes of Perylene Bisimide Oligomers %U http://dx.doi.org/10.1021/acs.orglett.4c01928 %V 26 %X An iterative step-by-step synthetic approach is employed to form perylene bisimide (PBI) oligomers of defined sizes by connecting the PBI units through their imide positions via a benzyl linker. The versatility of this approach was showcased by its successful implementation on two different PBI building blocks to achieve two separate series of oligomers (up to the pentamer) with modulated conformations: one with an open random coil oligomer and one with an H-type foldamer architecture.
• Dynamics of reduced perylene bisimide cyclophane redox species by ultrafast spectroelectrochemistry. Fröhlich, Rebecca; Rühe, Jessica; Moos, Michael; Kontschak, Laura; Ehrmann, Patrik; Würthner, Frank; Lambert, Christoph; Brixner, Tobias. In J. Chem. Phys., 160(23). 2024.
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  Charged molecules play essential roles in many natural and artificial functional processes, ranging from photosynthesis to photovoltaics to chemical reactions and more. It is often difficult to identify the optical dynamic properties of relevant redox species because they cannot be easily prepared, their spectra overlap, or they evolve on a femtosecond timescale. Here, we address these challenges by combining spec- troelectrochemistry, ultrafast transient absorption spectroscopy, and suitable data analysis. We illustrate the method with the various redox species of a cyclophane composed of two perylene bisimide subunits. While singular-value decomposition is a well-established tool in the analysis of time-dependent spectra of a single molecular species, we here use it additionally to separate transient maps of individual redox species. This is relevant because at any specific applied electrochemical potential, several redox species coexist in the ensemble, and our pro- cedure allows disentangling their spectroscopic response. In the second step, global analysis is then employed to retrieve the excited-state lifetimes and decay-associated difference spectra. Our approach is generally suitable for unraveling ultrafast dynamics in materials featuring charge-transfer processes.

  @article{Fr_hlich_2024, abstract = {Charged molecules play essential roles in many natural and artificial functional processes, ranging from photosynthesis to photovoltaics to chemical reactions and more. It is often difficult to identify the optical dynamic properties of relevant redox species because they cannot be easily prepared, their spectra overlap, or they evolve on a femtosecond timescale. Here, we address these challenges by combining spec- troelectrochemistry, ultrafast transient absorption spectroscopy, and suitable data analysis. We illustrate the method with the various redox species of a cyclophane composed of two perylene bisimide subunits. While singular-value decomposition is a well-established tool in the analysis of time-dependent spectra of a single molecular species, we here use it additionally to separate transient maps of individual redox species. This is relevant because at any specific applied electrochemical potential, several redox species coexist in the ensemble, and our pro- cedure allows disentangling their spectroscopic response. In the second step, global analysis is then employed to retrieve the excited-state lifetimes and decay-associated difference spectra. Our approach is generally suitable for unraveling ultrafast dynamics in materials featuring charge-transfer processes.}, author = {Fröhlich, Rebecca and Rühe, Jessica and Moos, Michael and Kontschak, Laura and Ehrmann, Patrik and Würthner, Frank and Lambert, Christoph and Brixner, Tobias}, journal = {J. Chem. Phys.}, keywords = {myown}, month = {06}, number = 23, publisher = {AIP Publishing}, title = {Dynamics of reduced perylene bisimide cyclophane redox species by ultrafast spectroelectrochemistry}, volume = 160, year = 2024 }

  %0 Journal Article %1 Fr_hlich_2024 %A Fröhlich, Rebecca %A Rühe, Jessica %A Moos, Michael %A Kontschak, Laura %A Ehrmann, Patrik %A Würthner, Frank %A Lambert, Christoph %A Brixner, Tobias %D 2024 %I AIP Publishing %J J. Chem. Phys. %N 23 %R 10.1063/5.0210490 %T Dynamics of reduced perylene bisimide cyclophane redox species by ultrafast spectroelectrochemistry %U http://dx.doi.org/10.1063/5.0210490 %V 160 %X Charged molecules play essential roles in many natural and artificial functional processes, ranging from photosynthesis to photovoltaics to chemical reactions and more. It is often difficult to identify the optical dynamic properties of relevant redox species because they cannot be easily prepared, their spectra overlap, or they evolve on a femtosecond timescale. Here, we address these challenges by combining spec- troelectrochemistry, ultrafast transient absorption spectroscopy, and suitable data analysis. We illustrate the method with the various redox species of a cyclophane composed of two perylene bisimide subunits. While singular-value decomposition is a well-established tool in the analysis of time-dependent spectra of a single molecular species, we here use it additionally to separate transient maps of individual redox species. This is relevant because at any specific applied electrochemical potential, several redox species coexist in the ensemble, and our pro- cedure allows disentangling their spectroscopic response. In the second step, global analysis is then employed to retrieve the excited-state lifetimes and decay-associated difference spectra. Our approach is generally suitable for unraveling ultrafast dynamics in materials featuring charge-transfer processes.
• A Monodisperse, End‐Capped Ru(bda) Oligomer with Outstanding Performance in Heterogeneous Electrochemical Water Oxidation. Schneider, Tilman; Seebauer, Florian; Beuerle, Florian; Würthner, Frank. In Adv. Mater. Technol., 9(11). 2024.
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  Water oxidation catalysis is a key step for sustainable fuel production by water splitting into hydrogen and oxygen. The synthesis of a novel coordination oligomer based on four Ru(bda) (bda = 2,2′-bipyridine-6,6′-dicarboxylate) centers, three 4,4′-bipyridine (4,4′-bpy) linkers, and two 4-picoline (4-pic) end caps is reported. The monodispersity of this tetranuclear compound is characterized by NMR techniques. Heterogeneous electrochemical water oxidation after immobilization on multi-walled carbon nanotubes (MWCNTs) shows catalytic performance unprecedented for this compound class, with a turnover frequency (TOF) of 133 s−1 and a turnover number (TON) of 4.89 × 106, at a current density of 43.8 mA cm−2 and a potential of 1.45 V versus normal hydrogen electrode (NHE).

  @article{Schneider_2024, abstract = {Water oxidation catalysis is a key step for sustainable fuel production by water splitting into hydrogen and oxygen. The synthesis of a novel coordination oligomer based on four Ru(bda) (bda = 2,2′-bipyridine-6,6′-dicarboxylate) centers, three 4,4′-bipyridine (4,4′-bpy) linkers, and two 4-picoline (4-pic) end caps is reported. The monodispersity of this tetranuclear compound is characterized by NMR techniques. Heterogeneous electrochemical water oxidation after immobilization on multi-walled carbon nanotubes (MWCNTs) shows catalytic performance unprecedented for this compound class, with a turnover frequency (TOF) of 133 s−1 and a turnover number (TON) of 4.89 × 106, at a current density of 43.8 mA cm−2 and a potential of 1.45 V versus normal hydrogen electrode (NHE).}, author = {Schneider, Tilman and Seebauer, Florian and Beuerle, Florian and Würthner, Frank}, journal = {Adv. Mater. Technol.}, keywords = {myown}, month = {01}, number = 11, publisher = {Wiley}, title = {A Monodisperse, End‐Capped Ru(bda) Oligomer with Outstanding Performance in Heterogeneous Electrochemical Water Oxidation}, volume = 9, year = 2024 }

  %0 Journal Article %1 Schneider_2024 %A Schneider, Tilman %A Seebauer, Florian %A Beuerle, Florian %A Würthner, Frank %D 2024 %I Wiley %J Adv. Mater. Technol. %N 11 %R 10.1002/admt.202301721 %T A Monodisperse, End‐Capped Ru(bda) Oligomer with Outstanding Performance in Heterogeneous Electrochemical Water Oxidation %U http://dx.doi.org/10.1002/admt.202301721 %V 9 %X Water oxidation catalysis is a key step for sustainable fuel production by water splitting into hydrogen and oxygen. The synthesis of a novel coordination oligomer based on four Ru(bda) (bda = 2,2′-bipyridine-6,6′-dicarboxylate) centers, three 4,4′-bipyridine (4,4′-bpy) linkers, and two 4-picoline (4-pic) end caps is reported. The monodispersity of this tetranuclear compound is characterized by NMR techniques. Heterogeneous electrochemical water oxidation after immobilization on multi-walled carbon nanotubes (MWCNTs) shows catalytic performance unprecedented for this compound class, with a turnover frequency (TOF) of 133 s−1 and a turnover number (TON) of 4.89 × 106, at a current density of 43.8 mA cm−2 and a potential of 1.45 V versus normal hydrogen electrode (NHE).
• Room‐Temperature Near‐Infrared Phosphorescence from C64 Nanographene Tetraimide by π‐Stacking Complexation with Platinum Porphyrin. Niyas, M. A.; Garain, Swadhin; Shoyama, Kazutaka; Würthner, Frank. In Angew. Chem. Int. Ed. 2024.
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  Near-Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to negligible spin–orbit coupling and a low energy gap leading to fast non-radiative transitions. Here, we show a supramolecular host–guest strategy to harvest the energy from the low-lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X-ray analysis confirmed the 1 : 2 stoichiometric binding of a Pt(II) porphyrin on the two π-surfaces of 1. While the free 1 does not show emission in the NIR, the host–guest complex solution shows NIR phosphorescence at 77 K. Further, between 860–1100 nm, room temperature NIR phosphorescence (λmax=900 nm, τavg=142 μs) was observed for a solid-state sample drop-casted from a preformed complex in solution. Theoretical calculations reveal a non-zero spin–orbit coupling between isoenergetic S1 and T3 of π-stacked [1 ⋅ Pt(II) porphyrin] complex. External heavy-atom-induced spin–orbit coupling along with rigidification and protection from oxygen in the solid-state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1.

  @article{Niyas_2024, abstract = {Near-Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to negligible spin–orbit coupling and a low energy gap leading to fast non-radiative transitions. Here, we show a supramolecular host–guest strategy to harvest the energy from the low-lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X-ray analysis confirmed the 1 : 2 stoichiometric binding of a Pt(II) porphyrin on the two π-surfaces of 1. While the free 1 does not show emission in the NIR, the host–guest complex solution shows NIR phosphorescence at 77 K. Further, between 860–1100 nm, room temperature NIR phosphorescence (λmax=900 nm, τavg=142 μs) was observed for a solid-state sample drop-casted from a preformed complex in solution. Theoretical calculations reveal a non-zero spin–orbit coupling between isoenergetic S1 and T3 of π-stacked [1 ⋅ Pt(II) porphyrin] complex. External heavy-atom-induced spin–orbit coupling along with rigidification and protection from oxygen in the solid-state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1.}, author = {Niyas, M. A. and Garain, Swadhin and Shoyama, Kazutaka and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {06}, publisher = {Wiley}, title = {Room‐Temperature Near‐Infrared Phosphorescence from C64 Nanographene Tetraimide by π‐Stacking Complexation with Platinum Porphyrin}, year = 2024 }

  %0 Journal Article %1 Niyas_2024 %A Niyas, M. A. %A Garain, Swadhin %A Shoyama, Kazutaka %A Würthner, Frank %D 2024 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202406353 %T Room‐Temperature Near‐Infrared Phosphorescence from C64 Nanographene Tetraimide by π‐Stacking Complexation with Platinum Porphyrin %U http://dx.doi.org/10.1002/anie.202406353 %X Near-Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to negligible spin–orbit coupling and a low energy gap leading to fast non-radiative transitions. Here, we show a supramolecular host–guest strategy to harvest the energy from the low-lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X-ray analysis confirmed the 1 : 2 stoichiometric binding of a Pt(II) porphyrin on the two π-surfaces of 1. While the free 1 does not show emission in the NIR, the host–guest complex solution shows NIR phosphorescence at 77 K. Further, between 860–1100 nm, room temperature NIR phosphorescence (λmax=900 nm, τavg=142 μs) was observed for a solid-state sample drop-casted from a preformed complex in solution. Theoretical calculations reveal a non-zero spin–orbit coupling between isoenergetic S1 and T3 of π-stacked [1 ⋅ Pt(II) porphyrin] complex. External heavy-atom-induced spin–orbit coupling along with rigidification and protection from oxygen in the solid-state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1.
• The Delayed Box: Biphenyl Bisimide Cyclophane, a Supramolecular Nano-environment for the Efficient Generation of Delayed Fluorescence. Garain, Swadhin; Shoyama, Kazutaka; Ginder, Lea-Marleen; Sárosi, Menyhárt; Würthner, Frank. In J. Am. Chem. Soc., 146(31), pp. 22056–22063. 2024.
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  Activating delayed fluorescence emission in a dilute solution via a non-covalent approach is a formidable challenge. In this report, we propose a strategy for efficient delayed fluorescence generation in dilute solution using a non-covalent approach via supramolecularly engineered cyclophane-based nanoenvironments that provide sufficient binding strength to π-conjugated guests and that can stabilize triplet excitons by reducing vibrational dissipation and lowering the singlet–triplet energy gap for efficient delayed fluorescence emission. Toward this goal, a novel biphenyl bisimide-derived cyclophane is introduced as an electron-deficient and efficient triplet-generating host. Upon encapsulation of various carbazole-derived guests inside the nanocavity of this cyclophane, emissive charge transfer (CT) states close to the triplet energy level of the biphenyl bisimide are generated. The experimental results of host–guest studies manifest high association constants up to 104 M–1 as the prerequisite for inclusion complex formation, the generation of emissive CT states, and triplet-state stabilization in a diluted solution state. By means of different carbazole guest molecules, we could realize tunable delayed fluorescence emission in this carbazole-encapsulated biphenyl bisimide cyclophane in methylcyclohexane/carbon tetrachloride solutions with a quantum yield (QY) of up to 15.6%. Crystal structure analyses and solid-state photophysical studies validate the conclusions from our solution studies and provide insights into the delayed fluorescence emission mechanism.

  @article{Garain_2024, abstract = {Activating delayed fluorescence emission in a dilute solution via a non-covalent approach is a formidable challenge. In this report, we propose a strategy for efficient delayed fluorescence generation in dilute solution using a non-covalent approach via supramolecularly engineered cyclophane-based nanoenvironments that provide sufficient binding strength to π-conjugated guests and that can stabilize triplet excitons by reducing vibrational dissipation and lowering the singlet–triplet energy gap for efficient delayed fluorescence emission. Toward this goal, a novel biphenyl bisimide-derived cyclophane is introduced as an electron-deficient and efficient triplet-generating host. Upon encapsulation of various carbazole-derived guests inside the nanocavity of this cyclophane, emissive charge transfer (CT) states close to the triplet energy level of the biphenyl bisimide are generated. The experimental results of host–guest studies manifest high association constants up to 104 M–1 as the prerequisite for inclusion complex formation, the generation of emissive CT states, and triplet-state stabilization in a diluted solution state. By means of different carbazole guest molecules, we could realize tunable delayed fluorescence emission in this carbazole-encapsulated biphenyl bisimide cyclophane in methylcyclohexane/carbon tetrachloride solutions with a quantum yield (QY) of up to 15.6%. Crystal structure analyses and solid-state photophysical studies validate the conclusions from our solution studies and provide insights into the delayed fluorescence emission mechanism.}, author = {Garain, Swadhin and Shoyama, Kazutaka and Ginder, Lea-Marleen and Sárosi, Menyhárt and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {07}, number = 31, pages = {22056–22063}, publisher = {American Chemical Society (ACS)}, title = {The Delayed Box: Biphenyl Bisimide Cyclophane, a Supramolecular Nano-environment for the Efficient Generation of Delayed Fluorescence}, volume = 146, year = 2024 }

  %0 Journal Article %1 Garain_2024 %A Garain, Swadhin %A Shoyama, Kazutaka %A Ginder, Lea-Marleen %A Sárosi, Menyhárt %A Würthner, Frank %D 2024 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 31 %P 22056–22063 %R 10.1021/jacs.4c07730 %T The Delayed Box: Biphenyl Bisimide Cyclophane, a Supramolecular Nano-environment for the Efficient Generation of Delayed Fluorescence %U http://dx.doi.org/10.1021/jacs.4c07730 %V 146 %X Activating delayed fluorescence emission in a dilute solution via a non-covalent approach is a formidable challenge. In this report, we propose a strategy for efficient delayed fluorescence generation in dilute solution using a non-covalent approach via supramolecularly engineered cyclophane-based nanoenvironments that provide sufficient binding strength to π-conjugated guests and that can stabilize triplet excitons by reducing vibrational dissipation and lowering the singlet–triplet energy gap for efficient delayed fluorescence emission. Toward this goal, a novel biphenyl bisimide-derived cyclophane is introduced as an electron-deficient and efficient triplet-generating host. Upon encapsulation of various carbazole-derived guests inside the nanocavity of this cyclophane, emissive charge transfer (CT) states close to the triplet energy level of the biphenyl bisimide are generated. The experimental results of host–guest studies manifest high association constants up to 104 M–1 as the prerequisite for inclusion complex formation, the generation of emissive CT states, and triplet-state stabilization in a diluted solution state. By means of different carbazole guest molecules, we could realize tunable delayed fluorescence emission in this carbazole-encapsulated biphenyl bisimide cyclophane in methylcyclohexane/carbon tetrachloride solutions with a quantum yield (QY) of up to 15.6%. Crystal structure analyses and solid-state photophysical studies validate the conclusions from our solution studies and provide insights into the delayed fluorescence emission mechanism.
• A highly fluorescent bora[6]helicene exhibiting circularly polarized light emission. Schnitzlein, Matthias; Shoyama, Kazutaka; Würthner, Frank. In Chem. Sci., 15(8), pp. 2984–2989. 2024.
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  Heteroatom-doped helicenes have attracted great research interest due to their inherent chirality enabling fascinating new applications. Herein we present our successful synthesis of 19c-boratribenzo[gh,jk,mn][6]helicene, the hitherto longest and first configurationally stable pristine bora[n]helicene. It displays intense orange fluorescence and circularly polarized light (CPL) emission with a high quantum yield of up to 84%. X-ray single crystal analysis reveals a highly twisted, helical shape and intriguing intermolecular stacking. Complexation with a size-complemental aza[4]helicene yielded an unprecedented hetero-chiral π–π-stacked helicene dimer.

  @article{D3SC05171D, abstract = {Heteroatom-doped helicenes have attracted great research interest due to their inherent chirality enabling fascinating new applications. Herein we present our successful synthesis of 19c-boratribenzo[gh{,}jk{,}mn][6]helicene{,} the hitherto longest and first configurationally stable pristine bora[n]helicene. It displays intense orange fluorescence and circularly polarized light (CPL) emission with a high quantum yield of up to 84%. X-ray single crystal analysis reveals a highly twisted{,} helical shape and intriguing intermolecular stacking. Complexation with a size-complemental aza[4]helicene yielded an unprecedented hetero-chiral π–π-stacked helicene dimer.}, author = {Schnitzlein, Matthias and Shoyama, Kazutaka and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 8, pages = {2984-2989}, publisher = {The Royal Society of Chemistry}, title = {A highly fluorescent bora[6]helicene exhibiting circularly polarized light emission}, volume = 15, year = 2024 }

  %0 Journal Article %1 D3SC05171D %A Schnitzlein, Matthias %A Shoyama, Kazutaka %A Würthner, Frank %D 2024 %I The Royal Society of Chemistry %J Chem. Sci. %N 8 %P 2984-2989 %R 10.1039/D3SC05171D %T A highly fluorescent bora[6]helicene exhibiting circularly polarized light emission %U http://dx.doi.org/10.1039/D3SC05171D %V 15 %X Heteroatom-doped helicenes have attracted great research interest due to their inherent chirality enabling fascinating new applications. Herein we present our successful synthesis of 19c-boratribenzo[gh,jk,mn][6]helicene, the hitherto longest and first configurationally stable pristine bora[n]helicene. It displays intense orange fluorescence and circularly polarized light (CPL) emission with a high quantum yield of up to 84%. X-ray single crystal analysis reveals a highly twisted, helical shape and intriguing intermolecular stacking. Complexation with a size-complemental aza[4]helicene yielded an unprecedented hetero-chiral π–π-stacked helicene dimer.
• Mutual induced fit transition structure stabilization of corannulene’s bowl-to-bowl inversion in a perylene bisimide cyclophane. Weh, Manuel; Kroeger, Asja A.; Anhalt, Olga; Karton, Amir; Würthner, Frank. In Chem. Sci., 15(2), pp. 609–617. 2024.
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  Corannulene is known to undergo a fast bowl-to-bowl inversion at r.t. via a planar transition structure (TS). Herein we present the catalysis of this process within a perylene bisimide (PBI) cyclophane composed of chirally twisted, non-planar chromophores, linked by para-xylylene spacers. Variable temperature NMR studies reveal that the bowl-to-bowl inversion is significantly accelerated within the cyclophane template despite the structural non-complementarity between the binding site of the host and the TS of the guest. The observed acceleration corresponds to a decrease in the bowl-to-bowl inversion barrier of 11.6 kJ mol−1 compared to the uncatalyzed process. Comparative binding studies for corannulene (20 π-electrons) and other planar polycyclic aromatic hydrocarbons (PAHs) with 14 to 24 π-electrons were applied to rationalize this barrier reduction. They revealed high binding constants that reach, in tetrachloromethane as a solvent, the picomolar range for the largest guest coronene. Computational models corroborate these experimental results and suggest that both TS stabilization and ground state destabilization contribute to the observed catalytic effect. Hereby, we find a “mutual induced fit” between host and guest in the TS complex, such that mutual geometric adaptation of the energetically favored planar TS and curved π-systems of the host results in an unprecedented non-planar TS of corannulene. Concomitant partial planarization of the PBI units optimizes noncovalent TS stabilization by π–π stacking interactions. This observation of a “mutual induced fit” in the TS of a host–guest complex was further validated experimentally by single crystal X-ray analysis of a host–guest complex with coronene as a qualitative transition state analogue.

  @article{D3SC05341E, abstract = {Corannulene is known to undergo a fast bowl-to-bowl inversion at r.t. via a planar transition structure (TS). Herein we present the catalysis of this process within a perylene bisimide (PBI) cyclophane composed of chirally twisted{,} non-planar chromophores{,} linked by para-xylylene spacers. Variable temperature NMR studies reveal that the bowl-to-bowl inversion is significantly accelerated within the cyclophane template despite the structural non-complementarity between the binding site of the host and the TS of the guest. The observed acceleration corresponds to a decrease in the bowl-to-bowl inversion barrier of 11.6 kJ mol−1 compared to the uncatalyzed process. Comparative binding studies for corannulene (20 π-electrons) and other planar polycyclic aromatic hydrocarbons (PAHs) with 14 to 24 π-electrons were applied to rationalize this barrier reduction. They revealed high binding constants that reach{,} in tetrachloromethane as a solvent{,} the picomolar range for the largest guest coronene. Computational models corroborate these experimental results and suggest that both TS stabilization and ground state destabilization contribute to the observed catalytic effect. Hereby{,} we find a “mutual induced fit” between host and guest in the TS complex{,} such that mutual geometric adaptation of the energetically favored planar TS and curved π-systems of the host results in an unprecedented non-planar TS of corannulene. Concomitant partial planarization of the PBI units optimizes noncovalent TS stabilization by π–π stacking interactions. This observation of a “mutual induced fit” in the TS of a host–guest complex was further validated experimentally by single crystal X-ray analysis of a host–guest complex with coronene as a qualitative transition state analogue.}, author = {Weh, Manuel and Kroeger, Asja A. and Anhalt, Olga and Karton, Amir and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 2, pages = {609-617}, title = {Mutual induced fit transition structure stabilization of corannulene's bowl-to-bowl inversion in a perylene bisimide cyclophane}, volume = 15, year = 2024 }

  %0 Journal Article %1 D3SC05341E %A Weh, Manuel %A Kroeger, Asja A. %A Anhalt, Olga %A Karton, Amir %A Würthner, Frank %D 2024 %J Chem. Sci. %N 2 %P 609-617 %R 10.1039/D3SC05341E %T Mutual induced fit transition structure stabilization of corannulene's bowl-to-bowl inversion in a perylene bisimide cyclophane %U http://dx.doi.org/10.1039/D3SC05341E %V 15 %X Corannulene is known to undergo a fast bowl-to-bowl inversion at r.t. via a planar transition structure (TS). Herein we present the catalysis of this process within a perylene bisimide (PBI) cyclophane composed of chirally twisted, non-planar chromophores, linked by para-xylylene spacers. Variable temperature NMR studies reveal that the bowl-to-bowl inversion is significantly accelerated within the cyclophane template despite the structural non-complementarity between the binding site of the host and the TS of the guest. The observed acceleration corresponds to a decrease in the bowl-to-bowl inversion barrier of 11.6 kJ mol−1 compared to the uncatalyzed process. Comparative binding studies for corannulene (20 π-electrons) and other planar polycyclic aromatic hydrocarbons (PAHs) with 14 to 24 π-electrons were applied to rationalize this barrier reduction. They revealed high binding constants that reach, in tetrachloromethane as a solvent, the picomolar range for the largest guest coronene. Computational models corroborate these experimental results and suggest that both TS stabilization and ground state destabilization contribute to the observed catalytic effect. Hereby, we find a “mutual induced fit” between host and guest in the TS complex, such that mutual geometric adaptation of the energetically favored planar TS and curved π-systems of the host results in an unprecedented non-planar TS of corannulene. Concomitant partial planarization of the PBI units optimizes noncovalent TS stabilization by π–π stacking interactions. This observation of a “mutual induced fit” in the TS of a host–guest complex was further validated experimentally by single crystal X-ray analysis of a host–guest complex with coronene as a qualitative transition state analogue.
• Cooperative Binding and Chirogenesis in an Expanded Perylene Bisimide Cyclophane. Sukumaran, Divya P.; Shoyama, Kazutaka; Dubey, Rajeev K.; Würthner, Frank. In J. Am. Chem. Soc., 146(31), pp. 22077–22084. 2024.
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  The encapsulation of more than one guest molecule into a synthetic cavity is a highly desirable yet a highly challenging task to achieve for neutral supramolecular hosts in organic media. Herein, we report a neutral perylene bisimide cyclophane, which has a tailored chiral cavity with an interchromophoric distance of 11.2 Å, capable of binding two aromatic guests in a π-stacked fashion. Detailed host–guest binding studies with a series of aromatic guests revealed that the encapsulation of the second guest in this cyclophane is notably more favored than the first one. Accordingly, for the encapsulation of the coronene dimer, a cooperativity factor (α) as high as 485 was observed, which is remarkably high for neutral host–guest systems. Furthermore, a successful chirality transfer, from the chiral host to encapsulated coronenes, resulted in a chiral charge-transfer (CT) complex and the rare observation of circularly polarized emission originating from the CT state for a noncovalent donor–acceptor assembly in solution. The involvement of the CT state also afforded an enhancement in the luminescence dissymmetry factor (glum) value due to its relatively large magnetic transition dipole moment. The 1:2 binding pattern and chirality-transfer were unambiguously verified by single-crystal X-ray diffraction analysis of the host–guest superstructures.

  @article{Sukumaran_2024, abstract = {The encapsulation of more than one guest molecule into a synthetic cavity is a highly desirable yet a highly challenging task to achieve for neutral supramolecular hosts in organic media. Herein, we report a neutral perylene bisimide cyclophane, which has a tailored chiral cavity with an interchromophoric distance of 11.2 Å, capable of binding two aromatic guests in a π-stacked fashion. Detailed host–guest binding studies with a series of aromatic guests revealed that the encapsulation of the second guest in this cyclophane is notably more favored than the first one. Accordingly, for the encapsulation of the coronene dimer, a cooperativity factor (α) as high as 485 was observed, which is remarkably high for neutral host–guest systems. Furthermore, a successful chirality transfer, from the chiral host to encapsulated coronenes, resulted in a chiral charge-transfer (CT) complex and the rare observation of circularly polarized emission originating from the CT state for a noncovalent donor–acceptor assembly in solution. The involvement of the CT state also afforded an enhancement in the luminescence dissymmetry factor (glum) value due to its relatively large magnetic transition dipole moment. The 1:2 binding pattern and chirality-transfer were unambiguously verified by single-crystal X-ray diffraction analysis of the host–guest superstructures.}, author = {Sukumaran, Divya P. and Shoyama, Kazutaka and Dubey, Rajeev K. and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {07}, number = 31, pages = {22077–22084}, publisher = {American Chemical Society (ACS)}, title = {Cooperative Binding and Chirogenesis in an Expanded Perylene Bisimide Cyclophane}, volume = 146, year = 2024 }

  %0 Journal Article %1 Sukumaran_2024 %A Sukumaran, Divya P. %A Shoyama, Kazutaka %A Dubey, Rajeev K. %A Würthner, Frank %D 2024 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 31 %P 22077–22084 %R 10.1021/jacs.4c08073 %T Cooperative Binding and Chirogenesis in an Expanded Perylene Bisimide Cyclophane %U http://dx.doi.org/10.1021/jacs.4c08073 %V 146 %X The encapsulation of more than one guest molecule into a synthetic cavity is a highly desirable yet a highly challenging task to achieve for neutral supramolecular hosts in organic media. Herein, we report a neutral perylene bisimide cyclophane, which has a tailored chiral cavity with an interchromophoric distance of 11.2 Å, capable of binding two aromatic guests in a π-stacked fashion. Detailed host–guest binding studies with a series of aromatic guests revealed that the encapsulation of the second guest in this cyclophane is notably more favored than the first one. Accordingly, for the encapsulation of the coronene dimer, a cooperativity factor (α) as high as 485 was observed, which is remarkably high for neutral host–guest systems. Furthermore, a successful chirality transfer, from the chiral host to encapsulated coronenes, resulted in a chiral charge-transfer (CT) complex and the rare observation of circularly polarized emission originating from the CT state for a noncovalent donor–acceptor assembly in solution. The involvement of the CT state also afforded an enhancement in the luminescence dissymmetry factor (glum) value due to its relatively large magnetic transition dipole moment. The 1:2 binding pattern and chirality-transfer were unambiguously verified by single-crystal X-ray diffraction analysis of the host–guest superstructures.

• Concentration-, Temperature- and Solvent-Dependent Self-Assembly: Merocyanine Dimerization as a Showcase Example for Obtaining Reliable Thermodynamic Data. Vonhausen, Yvonne; Würthner, Frank. In Chemistry - A European Journal, 29(37). 2023.
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  Mathematical models for the concentration-, temperature- and solvent-dependent analysis of self-assembly equilibria are derived for the most simple case of dimer formation, to highlight the assumptions these models and the thus determined thermodynamic parameters are based on. The three models were applied to UV/Vis absorption data for the dimerization of a highly dipolar merocyanine dye in 1,4-dioxane. Isothermal titration calorimetry (ITC) dilution experiments were performed as an independent reference technique. While the concentration-dependent analysis is according to our studies the most reliable method, also the less time-consuming temperature-dependent evaluation can give accurate results in the present example, despite small thermochromic effects. In contrast, the strong negative solvatochromism of the merocyanine tampers with the results from the solvent-dependent evaluation. Even though the studies presented in this work are limited to the monomer-dimer equilibrium of a dipolar dye, the basic principles can be transferred to other chromophores and different self-assembly models, including those for supramolecular polymerization.

  @article{Vonhausen_2023, abstract = {Mathematical models for the concentration-, temperature- and solvent-dependent analysis of self-assembly equilibria are derived for the most simple case of dimer formation, to highlight the assumptions these models and the thus determined thermodynamic parameters are based on. The three models were applied to UV/Vis absorption data for the dimerization of a highly dipolar merocyanine dye in 1,4-dioxane. Isothermal titration calorimetry (ITC) dilution experiments were performed as an independent reference technique. While the concentration-dependent analysis is according to our studies the most reliable method, also the less time-consuming temperature-dependent evaluation can give accurate results in the present example, despite small thermochromic effects. In contrast, the strong negative solvatochromism of the merocyanine tampers with the results from the solvent-dependent evaluation. Even though the studies presented in this work are limited to the monomer-dimer equilibrium of a dipolar dye, the basic principles can be transferred to other chromophores and different self-assembly models, including those for supramolecular polymerization.}, author = {Vonhausen, Yvonne and Würthner, Frank}, journal = {Chemistry - A European Journal}, keywords = {myown}, month = {05}, number = 37, publisher = {Wiley}, title = {Concentration-, Temperature- and Solvent-Dependent Self-Assembly: Merocyanine Dimerization as a Showcase Example for Obtaining Reliable Thermodynamic Data}, volume = 29, year = 2023 }

  %0 Journal Article %1 Vonhausen_2023 %A Vonhausen, Yvonne %A Würthner, Frank %D 2023 %I Wiley %J Chemistry - A European Journal %N 37 %R 10.1002/chem.202300359 %T Concentration-, Temperature- and Solvent-Dependent Self-Assembly: Merocyanine Dimerization as a Showcase Example for Obtaining Reliable Thermodynamic Data %U https://doi.org/10.1002%2Fchem.202300359 %V 29 %X Mathematical models for the concentration-, temperature- and solvent-dependent analysis of self-assembly equilibria are derived for the most simple case of dimer formation, to highlight the assumptions these models and the thus determined thermodynamic parameters are based on. The three models were applied to UV/Vis absorption data for the dimerization of a highly dipolar merocyanine dye in 1,4-dioxane. Isothermal titration calorimetry (ITC) dilution experiments were performed as an independent reference technique. While the concentration-dependent analysis is according to our studies the most reliable method, also the less time-consuming temperature-dependent evaluation can give accurate results in the present example, despite small thermochromic effects. In contrast, the strong negative solvatochromism of the merocyanine tampers with the results from the solvent-dependent evaluation. Even though the studies presented in this work are limited to the monomer-dimer equilibrium of a dipolar dye, the basic principles can be transferred to other chromophores and different self-assembly models, including those for supramolecular polymerization.
• Naphthalimide-Fused Subphthalocyanines: Electron-Deficient Materials Prepared by Cascade Annulation. Labella, Jorge; Shoyama, Kazutaka; Guzman, David; Schembri, Tim; Stolte, Matthias; Torres, Tomas; Würthner, Frank. In ACS Materials Letters, pp. 543–548. 2023.
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  Imide-fused porphyrinoids are becoming key components in the area of molecular materials. Herein we report the synthesis of naphthalimide (NMI)-annulated subphthalocyanines (SubPcs) designed as an NIR-absorbing n-type organic semiconductor. Two different synthetic pathways could be applied for the preparation of NMI-fused SubPcs. The first consists of a [3 + 2] annulation between SubPc boronic ester and dibromo-NMI. This annulation, which involves the first CH activation reaction of a SubPc derivative reported so far, is totally regioselective to the β-position. Density functional theory (DFT) indicated that such position is favored both kinetically and thermodynamically. On the other hand, the second method relies on a cyclotrimerization of NMI-fused phthalonitrile. Electrochemical measurements and DFT calculations revealed that these NMI-fused SubPcs have low-lying LUMO energy levels suitable for electron charge transport. The N-alkyl substituted derivative (NMI-SubPc 2) was successfully applied as an nonfullerene acceptor (NFA) in combination with donor polymer PM6 in bulk-heterojunction (BHJ) organic solar cells (OSCs) with a highest power conversion efficiency (PCE) of 7.0%. This value is comparable to the record PCE of SubPc derivatives in BHJ-OSCs. Our results open a new vista in the preparation of π-extended contracted porphyrinoids and substantiate the potential of this new class of strong-absorbing electron-acceptor materials for applications in optoelectronic devices.

  @article{Labella_2023, abstract = {Imide-fused porphyrinoids are becoming key components in the area of molecular materials. Herein we report the synthesis of naphthalimide (NMI)-annulated subphthalocyanines (SubPcs) designed as an NIR-absorbing n-type organic semiconductor. Two different synthetic pathways could be applied for the preparation of NMI-fused SubPcs. The first consists of a [3 + 2] annulation between SubPc boronic ester and dibromo-NMI. This annulation, which involves the first CH activation reaction of a SubPc derivative reported so far, is totally regioselective to the β-position. Density functional theory (DFT) indicated that such position is favored both kinetically and thermodynamically. On the other hand, the second method relies on a cyclotrimerization of NMI-fused phthalonitrile. Electrochemical measurements and DFT calculations revealed that these NMI-fused SubPcs have low-lying LUMO energy levels suitable for electron charge transport. The N-alkyl substituted derivative (NMI-SubPc 2) was successfully applied as an nonfullerene acceptor (NFA) in combination with donor polymer PM6 in bulk-heterojunction (BHJ) organic solar cells (OSCs) with a highest power conversion efficiency (PCE) of 7.0%. This value is comparable to the record PCE of SubPc derivatives in BHJ-OSCs. Our results open a new vista in the preparation of π-extended contracted porphyrinoids and substantiate the potential of this new class of strong-absorbing electron-acceptor materials for applications in optoelectronic devices.}, author = {Labella, Jorge and Shoyama, Kazutaka and Guzman, David and Schembri, Tim and Stolte, Matthias and Torres, Tomas and Würthner, Frank}, journal = {ACS Materials Letters}, keywords = {myown}, month = {01}, pages = {543–548}, publisher = {American Chemical Society ({ACS})}, title = {Naphthalimide-Fused Subphthalocyanines: Electron-Deficient Materials Prepared by Cascade Annulation}, year = 2023 }

  %0 Journal Article %1 Labella_2023 %A Labella, Jorge %A Shoyama, Kazutaka %A Guzman, David %A Schembri, Tim %A Stolte, Matthias %A Torres, Tomas %A Würthner, Frank %D 2023 %I American Chemical Society (ACS) %J ACS Materials Letters %P 543--548 %R 10.1021/acsmaterialslett.2c01132 %T Naphthalimide-Fused Subphthalocyanines: Electron-Deficient Materials Prepared by Cascade Annulation %U https://doi.org/10.1021%2Facsmaterialslett.2c01132 %X Imide-fused porphyrinoids are becoming key components in the area of molecular materials. Herein we report the synthesis of naphthalimide (NMI)-annulated subphthalocyanines (SubPcs) designed as an NIR-absorbing n-type organic semiconductor. Two different synthetic pathways could be applied for the preparation of NMI-fused SubPcs. The first consists of a [3 + 2] annulation between SubPc boronic ester and dibromo-NMI. This annulation, which involves the first CH activation reaction of a SubPc derivative reported so far, is totally regioselective to the β-position. Density functional theory (DFT) indicated that such position is favored both kinetically and thermodynamically. On the other hand, the second method relies on a cyclotrimerization of NMI-fused phthalonitrile. Electrochemical measurements and DFT calculations revealed that these NMI-fused SubPcs have low-lying LUMO energy levels suitable for electron charge transport. The N-alkyl substituted derivative (NMI-SubPc 2) was successfully applied as an nonfullerene acceptor (NFA) in combination with donor polymer PM6 in bulk-heterojunction (BHJ) organic solar cells (OSCs) with a highest power conversion efficiency (PCE) of 7.0%. This value is comparable to the record PCE of SubPc derivatives in BHJ-OSCs. Our results open a new vista in the preparation of π-extended contracted porphyrinoids and substantiate the potential of this new class of strong-absorbing electron-acceptor materials for applications in optoelectronic devices.
• Folding-Induced Promotion of Proton-Coupled Electron Transfers via Proximal Base for Light-Driven Water Oxidation. Noll, Niklas; Groß, Tobias; Shoyama, Kazutaka; Beuerle, Florian; Würthner, Frank. In Angew. Chem. Int. Ed., 62(7). 2023.
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  Proton-coupled electron-transfer (PCET) processes play a key role in biocatalytic energy conversion and storage, for example, photosynthesis or nitrogen fixation. Here, we report a series of bipyridine-containing di- to tetranuclear Ru(bda) macrocycles 2 C–4 C (bda: 2,2′-bipyridine-6,6′-dicarboxylate) to promote O−O bond formation. In photocatalytic water oxidation under neutral conditions, all complexes 2 C–4 C prevail in a folded conformation that support the water nucleophilic attack (WNA) pathway with remarkable turnover frequencies of up to 15.5 s−1 per Ru unit respectively. Single-crystal X-ray analysis revealed an increased tendency for intramolecular π-π stacking and preorganization of the proximal bases close to the active centers for the larger macrocycles. H/D kinetic isotope effect studies and electrochemical data demonstrate the key role of the proximal bipyridines as proton acceptors in lowering the activation barrier for the crucial nucleophilic attack of H2O in the WNA mechanism.

  @article{Noll_2023, abstract = {Proton-coupled electron-transfer (PCET) processes play a key role in biocatalytic energy conversion and storage, for example, photosynthesis or nitrogen fixation. Here, we report a series of bipyridine-containing di- to tetranuclear Ru(bda) macrocycles 2 C–4 C (bda: 2,2′-bipyridine-6,6′-dicarboxylate) to promote O−O bond formation. In photocatalytic water oxidation under neutral conditions, all complexes 2 C–4 C prevail in a folded conformation that support the water nucleophilic attack (WNA) pathway with remarkable turnover frequencies of up to 15.5 s−1 per Ru unit respectively. Single-crystal X-ray analysis revealed an increased tendency for intramolecular π-π stacking and preorganization of the proximal bases close to the active centers for the larger macrocycles. H/D kinetic isotope effect studies and electrochemical data demonstrate the key role of the proximal bipyridines as proton acceptors in lowering the activation barrier for the crucial nucleophilic attack of H2O in the WNA mechanism.}, author = {Noll, Niklas and Groß, Tobias and Shoyama, Kazutaka and Beuerle, Florian and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {01}, number = 7, publisher = {Wiley}, title = {Folding-Induced Promotion of Proton-Coupled Electron Transfers via Proximal Base for Light-Driven Water Oxidation}, volume = 62, year = 2023 }

  %0 Journal Article %1 Noll_2023 %A Noll, Niklas %A Groß, Tobias %A Shoyama, Kazutaka %A Beuerle, Florian %A Würthner, Frank %D 2023 %I Wiley %J Angew. Chem. Int. Ed. %N 7 %R 10.1002/anie.202217745 %T Folding-Induced Promotion of Proton-Coupled Electron Transfers via Proximal Base for Light-Driven Water Oxidation %U https://doi.org/10.1002%2Fanie.202217745 %V 62 %X Proton-coupled electron-transfer (PCET) processes play a key role in biocatalytic energy conversion and storage, for example, photosynthesis or nitrogen fixation. Here, we report a series of bipyridine-containing di- to tetranuclear Ru(bda) macrocycles 2 C–4 C (bda: 2,2′-bipyridine-6,6′-dicarboxylate) to promote O−O bond formation. In photocatalytic water oxidation under neutral conditions, all complexes 2 C–4 C prevail in a folded conformation that support the water nucleophilic attack (WNA) pathway with remarkable turnover frequencies of up to 15.5 s−1 per Ru unit respectively. Single-crystal X-ray analysis revealed an increased tendency for intramolecular π-π stacking and preorganization of the proximal bases close to the active centers for the larger macrocycles. H/D kinetic isotope effect studies and electrochemical data demonstrate the key role of the proximal bipyridines as proton acceptors in lowering the activation barrier for the crucial nucleophilic attack of H2O in the WNA mechanism.
• π-Extended benzo[1,2:4,5]di[7]annulene bis(dicarboximide)s – a new class of non-alternant polycyclic aromatic dicarboximides. Spengler, Jonas; Zhu, Chongwei; Shoyama, Kazutaka; Würthner, Frank. In Chem. Sci., 14(39), pp. 10861–10866. 2023.
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  Aromatic dicarboximides are a class of molecules represented by the well-known rylene bis(dicarboximide)s, in particular perylene or naphthalene bis(dicarboximide)s, which show pronounced optoelectronic properties and are applied as color pigments, fluorescent dyes and organic semiconductors. Herein we extend the family of aromatic bis(dicarboximide)s and report the synthesis of the first series of non-alternant aromatic dicarboximides by twofold Pd-catalyzed [5 + 2] annulation. Characterization by UV/vis spectroscopy and cyclic voltammetry (CV) measurements give insight into the optoelectronic characteristics of the hitherto unexplored substance class of heptagon-containing imides. Theoretical studies by nucleus independent chemical shift (NICS) XY-scans and anisotropy of the induced current density (ACID) plots demonstrate the influence of both the non-alternant carbon framework and the imide moieties on aromaticity of the synthesized bisimides.

  @article{D3SC04015A, abstract = {Aromatic dicarboximides are a class of molecules represented by the well-known rylene bis(dicarboximide)s, in particular perylene or naphthalene bis(dicarboximide)s, which show pronounced optoelectronic properties and are applied as color pigments, fluorescent dyes and organic semiconductors. Herein we extend the family of aromatic bis(dicarboximide)s and report the synthesis of the first series of non-alternant aromatic dicarboximides by twofold Pd-catalyzed [5 + 2] annulation. Characterization by UV/vis spectroscopy and cyclic voltammetry (CV) measurements give insight into the optoelectronic characteristics of the hitherto unexplored substance class of heptagon-containing imides. Theoretical studies by nucleus independent chemical shift (NICS) XY-scans and anisotropy of the induced current density (ACID) plots demonstrate the influence of both the non-alternant carbon framework and the imide moieties on aromaticity of the synthesized bisimides.}, author = {Spengler, Jonas and Zhu, Chongwei and Shoyama, Kazutaka and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 39, pages = {10861-10866}, title = {π-Extended benzo[1,2:4,5]di[7]annulene bis(dicarboximide)s – a new class of non-alternant polycyclic aromatic dicarboximides}, volume = 14, year = 2023 }

  %0 Journal Article %1 D3SC04015A %A Spengler, Jonas %A Zhu, Chongwei %A Shoyama, Kazutaka %A Würthner, Frank %D 2023 %J Chem. Sci. %N 39 %P 10861-10866 %R 10.1039/D3SC04015A %T π-Extended benzo[1,2:4,5]di[7]annulene bis(dicarboximide)s – a new class of non-alternant polycyclic aromatic dicarboximides %U http://dx.doi.org/10.1039/D3SC04015A %V 14 %X Aromatic dicarboximides are a class of molecules represented by the well-known rylene bis(dicarboximide)s, in particular perylene or naphthalene bis(dicarboximide)s, which show pronounced optoelectronic properties and are applied as color pigments, fluorescent dyes and organic semiconductors. Herein we extend the family of aromatic bis(dicarboximide)s and report the synthesis of the first series of non-alternant aromatic dicarboximides by twofold Pd-catalyzed [5 + 2] annulation. Characterization by UV/vis spectroscopy and cyclic voltammetry (CV) measurements give insight into the optoelectronic characteristics of the hitherto unexplored substance class of heptagon-containing imides. Theoretical studies by nucleus independent chemical shift (NICS) XY-scans and anisotropy of the induced current density (ACID) plots demonstrate the influence of both the non-alternant carbon framework and the imide moieties on aromaticity of the synthesized bisimides.
• Nitrogen-doped polycyclic aromatic hydrocarbons by a one-pot Suzuki coupling/intramolecular SNAr reaction. Tian, Xiaoqi; Shoyama, Kazutaka; Würthner, Frank. In Chem. Sci., 14(2), pp. 284–290. 2023.
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  We report a new method for the synthesis of nitrogen-doped (N-doped) polycyclic aromatic hydrocarbons (PAHs) by a Suzuki coupling/intramolecular SNAr cascade reaction. A one- or two-fold [3 + 3] naphtho-annulation of halogenated aniline was conducted under Suzuki–Miyaura cross-coupling conditions to yield a series of fully fused N-doped PAHs. In contrast to reported methods to synthesize pyridinic or pyrrolic nitrogen-doped PAHs, our method enables preparation of PAHs doped with graphitic nitrogen, for which few reports are known in the literature. The crystal structure as well as absorption, fluorescence and electrochemical properties of these N-doped PAHs were investigated, which demonstrated the capability of N-doping to adjust optical and electronic properties and alter the LUMO energy level.

  @article{D2SC05409D, abstract = {We report a new method for the synthesis of nitrogen-doped (N-doped) polycyclic aromatic hydrocarbons (PAHs) by a Suzuki coupling/intramolecular SNAr cascade reaction. A one- or two-fold [3 + 3] naphtho-annulation of halogenated aniline was conducted under Suzuki–Miyaura cross-coupling conditions to yield a series of fully fused N-doped PAHs. In contrast to reported methods to synthesize pyridinic or pyrrolic nitrogen-doped PAHs{,} our method enables preparation of PAHs doped with graphitic nitrogen{,} for which few reports are known in the literature. The crystal structure as well as absorption{,} fluorescence and electrochemical properties of these N-doped PAHs were investigated{,} which demonstrated the capability of N-doping to adjust optical and electronic properties and alter the LUMO energy level.}, author = {Tian, Xiaoqi and Shoyama, Kazutaka and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 2, pages = {284-290}, title = {Nitrogen-doped polycyclic aromatic hydrocarbons by a one-pot Suzuki coupling/intramolecular SNAr reaction}, volume = 14, year = 2023 }

  %0 Journal Article %1 D2SC05409D %A Tian, Xiaoqi %A Shoyama, Kazutaka %A Würthner, Frank %D 2023 %J Chem. Sci. %N 2 %P 284-290 %R 10.1039/D2SC05409D %T Nitrogen-doped polycyclic aromatic hydrocarbons by a one-pot Suzuki coupling/intramolecular SNAr reaction %U http://dx.doi.org/10.1039/D2SC05409D %V 14 %X We report a new method for the synthesis of nitrogen-doped (N-doped) polycyclic aromatic hydrocarbons (PAHs) by a Suzuki coupling/intramolecular SNAr cascade reaction. A one- or two-fold [3 + 3] naphtho-annulation of halogenated aniline was conducted under Suzuki–Miyaura cross-coupling conditions to yield a series of fully fused N-doped PAHs. In contrast to reported methods to synthesize pyridinic or pyrrolic nitrogen-doped PAHs, our method enables preparation of PAHs doped with graphitic nitrogen, for which few reports are known in the literature. The crystal structure as well as absorption, fluorescence and electrochemical properties of these N-doped PAHs were investigated, which demonstrated the capability of N-doping to adjust optical and electronic properties and alter the LUMO energy level.
• Single-Molecule Ultrafast Fluorescence-Detected Pump-Probe Microscopy. Fersch, Daniel; Maly, Pavel; Rühe, Jessica; Lisinetskii, Victor; Hensen, Matthias; Würthner, Frank; Brixner, Tobias. In The Journal of Physical Chemistry Letters, 14(21), pp. 4923–4932. 2023.
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  We introduce fluorescence-detected pump–probe microscopy by combining a wavelength-tunable ultrafast laser with a confocal scanning fluorescence microscope, enabling access to the femtosecond time scale on the micrometer spatial scale. In addition, we obtain spectral information from Fourier transformation over excitation pulse-pair time delays. We demonstrate this new approach on a model system of a terrylene bisimide (TBI) dye embedded in a PMMA matrix and acquire the linear excitation spectrum as well as time-dependent pump–probe spectra simultaneously. We then push the technique toward single TBI molecules and analyze the statistical distribution of their excitation spectra. Furthermore, we demonstrate the ultrafast transient evolution of several individual molecules, highlighting their different behavior in contrast to the ensemble due to their individual local environment. By correlating the linear and nonlinear spectra, we assess the effect of the molecular environment on the excited-state energy.

  @article{Fersch_2023, abstract = {We introduce fluorescence-detected pump–probe microscopy by combining a wavelength-tunable ultrafast laser with a confocal scanning fluorescence microscope, enabling access to the femtosecond time scale on the micrometer spatial scale. In addition, we obtain spectral information from Fourier transformation over excitation pulse-pair time delays. We demonstrate this new approach on a model system of a terrylene bisimide (TBI) dye embedded in a PMMA matrix and acquire the linear excitation spectrum as well as time-dependent pump–probe spectra simultaneously. We then push the technique toward single TBI molecules and analyze the statistical distribution of their excitation spectra. Furthermore, we demonstrate the ultrafast transient evolution of several individual molecules, highlighting their different behavior in contrast to the ensemble due to their individual local environment. By correlating the linear and nonlinear spectra, we assess the effect of the molecular environment on the excited-state energy.}, author = {Fersch, Daniel and Maly, Pavel and Rühe, Jessica and Lisinetskii, Victor and Hensen, Matthias and Würthner, Frank and Brixner, Tobias}, journal = {The Journal of Physical Chemistry Letters}, keywords = {myown}, month = {05}, number = 21, pages = {4923–4932}, publisher = {American Chemical Society (ACS)}, title = {Single-Molecule Ultrafast Fluorescence-Detected Pump-Probe Microscopy}, volume = 14, year = 2023 }

  %0 Journal Article %1 Fersch_2023 %A Fersch, Daniel %A Maly, Pavel %A Rühe, Jessica %A Lisinetskii, Victor %A Hensen, Matthias %A Würthner, Frank %A Brixner, Tobias %D 2023 %I American Chemical Society (ACS) %J The Journal of Physical Chemistry Letters %N 21 %P 4923--4932 %R 10.1021/acs.jpclett.3c00839 %T Single-Molecule Ultrafast Fluorescence-Detected Pump-Probe Microscopy %U https://doi.org/10.1021%2Facs.jpclett.3c00839 %V 14 %X We introduce fluorescence-detected pump–probe microscopy by combining a wavelength-tunable ultrafast laser with a confocal scanning fluorescence microscope, enabling access to the femtosecond time scale on the micrometer spatial scale. In addition, we obtain spectral information from Fourier transformation over excitation pulse-pair time delays. We demonstrate this new approach on a model system of a terrylene bisimide (TBI) dye embedded in a PMMA matrix and acquire the linear excitation spectrum as well as time-dependent pump–probe spectra simultaneously. We then push the technique toward single TBI molecules and analyze the statistical distribution of their excitation spectra. Furthermore, we demonstrate the ultrafast transient evolution of several individual molecules, highlighting their different behavior in contrast to the ensemble due to their individual local environment. By correlating the linear and nonlinear spectra, we assess the effect of the molecular environment on the excited-state energy.
• Intersystem crossing of perylene bisimide neutral, radical anion, and dianion derivatives compared via ultrafast spectroelectrochemistry. Heitmüller, Julia; Fröhlich, Rebecca; Renner, Rebecca; Würthner, Frank; Brixner, Tobias. In Phys. Chem. Chem. Phys., 25(26), pp. 17214–17229. 2023.
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  Perylene bisimides are widely studied due to their various applications. Most research is carried out on neutral molecules but charged species are essential in the context of organic electronics and photovoltaics. In this study, we carry out ultrafast transient absorption spectroelectrochemistry and coherent two-dimensional electronic spectroelectrochemistry on three different neutral perylene bisimide derivatives as well as their singly and doubly reduced species. We compare an unsubstituted, flat parent perylene bisimide with two twisted ones that introduce spin–orbit coupling, leading to enhanced intersystem crossing. The internal conversion from higher excited states to the lowest electronically excited state occurs in the picosecond regime with lifetimes significantly shorter for the charged species compared to the neutral ones. Coherent oscillations of the transients for the flat dianion of parent perylene bisimide indicate the occurrence of Fermi resonance. The corresponding vibrational coupling and the superposition of the participating vibrational modes may lead to an enhanced charge separation and triplet formation.

  @article{D2CP05602J, abstract = {Perylene bisimides are widely studied due to their various applications. Most research is carried out on neutral molecules but charged species are essential in the context of organic electronics and photovoltaics. In this study, we carry out ultrafast transient absorption spectroelectrochemistry and coherent two-dimensional electronic spectroelectrochemistry on three different neutral perylene bisimide derivatives as well as their singly and doubly reduced species. We compare an unsubstituted, flat parent perylene bisimide with two twisted ones that introduce spin–orbit coupling, leading to enhanced intersystem crossing. The internal conversion from higher excited states to the lowest electronically excited state occurs in the picosecond regime with lifetimes significantly shorter for the charged species compared to the neutral ones. Coherent oscillations of the transients for the flat dianion of parent perylene bisimide indicate the occurrence of Fermi resonance. The corresponding vibrational coupling and the superposition of the participating vibrational modes may lead to an enhanced charge separation and triplet formation.}, author = {Heitmüller, Julia and Fröhlich, Rebecca and Renner, Rebecca and Würthner, Frank and Brixner, Tobias}, journal = {Phys. Chem. Chem. Phys.}, keywords = {myown}, number = 26, pages = {17214-17229}, title = {Intersystem crossing of perylene bisimide neutral, radical anion, and dianion derivatives compared via ultrafast spectroelectrochemistry}, volume = 25, year = 2023 }

  %0 Journal Article %1 D2CP05602J %A Heitmüller, Julia %A Fröhlich, Rebecca %A Renner, Rebecca %A Würthner, Frank %A Brixner, Tobias %D 2023 %J Phys. Chem. Chem. Phys. %N 26 %P 17214-17229 %R 10.1039/D2CP05602J %T Intersystem crossing of perylene bisimide neutral, radical anion, and dianion derivatives compared via ultrafast spectroelectrochemistry %U http://dx.doi.org/10.1039/D2CP05602J %V 25 %X Perylene bisimides are widely studied due to their various applications. Most research is carried out on neutral molecules but charged species are essential in the context of organic electronics and photovoltaics. In this study, we carry out ultrafast transient absorption spectroelectrochemistry and coherent two-dimensional electronic spectroelectrochemistry on three different neutral perylene bisimide derivatives as well as their singly and doubly reduced species. We compare an unsubstituted, flat parent perylene bisimide with two twisted ones that introduce spin–orbit coupling, leading to enhanced intersystem crossing. The internal conversion from higher excited states to the lowest electronically excited state occurs in the picosecond regime with lifetimes significantly shorter for the charged species compared to the neutral ones. Coherent oscillations of the transients for the flat dianion of parent perylene bisimide indicate the occurrence of Fermi resonance. The corresponding vibrational coupling and the superposition of the participating vibrational modes may lead to an enhanced charge separation and triplet formation.
• C64 Nanographene Tetraimide - A Receptor for Phthalocyanines with Subnanomolar Affinity. Niyas, M. A.; Shoyama, Kazutaka; Würthner, Frank. In Angew. Chem. Int. Ed., 62(25). 2023.
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  Phthalocyanines are extensively used by the dye and pigment industry and in photovoltaic and photodynamic therapy research due to their intense absorption of visible light, outstanding stability, and versatility. As pigments, the unsubstituted phthalocyanines are insoluble owing to strong intermolecular π-π-stacking interactions, which causes limitations for the solution chemistry for both free base and metalated phthalocyanines. Here we show a supramolecular host–guest strategy to dissolve phthalocyanines into solution. C64 nanographene tetraimide (1) binds two free base/zinc/copper phthalocyanines in a 1 : 2 stoichiometry to solubilize phthalocyanines as evidenced by 1H NMR spectroscopy, UV/Vis absorption and single-crystal X-ray analysis. Binding studies using a tetra-tert-butyl-substituted soluble phthalocyanine revealed binding affinities of up to 109 M−1 in tetrachloromethane, relating to a Gibbs free energy of −52 kJ mol−1. Energy decomposition analysis revealed that complexes between 1 and phthalocyanines are stabilized by dispersion interactions followed by electrostatics as well as significant charge-transfer interactions.

  @article{Niyas_2023, abstract = {Phthalocyanines are extensively used by the dye and pigment industry and in photovoltaic and photodynamic therapy research due to their intense absorption of visible light, outstanding stability, and versatility. As pigments, the unsubstituted phthalocyanines are insoluble owing to strong intermolecular π-π-stacking interactions, which causes limitations for the solution chemistry for both free base and metalated phthalocyanines. Here we show a supramolecular host–guest strategy to dissolve phthalocyanines into solution. C64 nanographene tetraimide (1) binds two free base/zinc/copper phthalocyanines in a 1 : 2 stoichiometry to solubilize phthalocyanines as evidenced by 1H NMR spectroscopy, UV/Vis absorption and single-crystal X-ray analysis. Binding studies using a tetra-tert-butyl-substituted soluble phthalocyanine revealed binding affinities of up to 109 M−1 in tetrachloromethane, relating to a Gibbs free energy of −52 kJ mol−1. Energy decomposition analysis revealed that complexes between 1 and phthalocyanines are stabilized by dispersion interactions followed by electrostatics as well as significant charge-transfer interactions.}, author = {Niyas, M. A. and Shoyama, Kazutaka and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {05}, number = 25, publisher = {Wiley}, title = {C64 Nanographene Tetraimide - A Receptor for Phthalocyanines with Subnanomolar Affinity}, volume = 62, year = 2023 }

  %0 Journal Article %1 Niyas_2023 %A Niyas, M. A. %A Shoyama, Kazutaka %A Würthner, Frank %D 2023 %I Wiley %J Angew. Chem. Int. Ed. %N 25 %R 10.1002/anie.202302032 %T C64 Nanographene Tetraimide - A Receptor for Phthalocyanines with Subnanomolar Affinity %U https://doi.org/10.1002%2Fanie.202302032 %V 62 %X Phthalocyanines are extensively used by the dye and pigment industry and in photovoltaic and photodynamic therapy research due to their intense absorption of visible light, outstanding stability, and versatility. As pigments, the unsubstituted phthalocyanines are insoluble owing to strong intermolecular π-π-stacking interactions, which causes limitations for the solution chemistry for both free base and metalated phthalocyanines. Here we show a supramolecular host–guest strategy to dissolve phthalocyanines into solution. C64 nanographene tetraimide (1) binds two free base/zinc/copper phthalocyanines in a 1 : 2 stoichiometry to solubilize phthalocyanines as evidenced by 1H NMR spectroscopy, UV/Vis absorption and single-crystal X-ray analysis. Binding studies using a tetra-tert-butyl-substituted soluble phthalocyanine revealed binding affinities of up to 109 M−1 in tetrachloromethane, relating to a Gibbs free energy of −52 kJ mol−1. Energy decomposition analysis revealed that complexes between 1 and phthalocyanines are stabilized by dispersion interactions followed by electrostatics as well as significant charge-transfer interactions.
• Water-Soluble Cationic Perylene Diimide Dyes as Stable Photocatalysts for H2O2 Evolution. Gryszel, Maciej; Schlossarek, Tim; Würthner, Frank; Natali, Mirco; Glowacki, Eric Daniel. In ChemPhotoChem. 2023.
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  Photocatalytic generation of hydrogen peroxide, H2O2, has gained increasing attention in recent years, with applications ranging from solar energy conversion to biophysical research. While semiconducting solid-state materials are normally regarded as the workhorse for photogeneration of H2O2, an intriguing alternative for on-demand H2O2 is the use of photocatalytic organic dyes. Herein we report the use of water-soluble dyes based on perylene diimide molecules which behave as true molecular catalysts for the light-induced conversion of dissolved oxygen to hydrogen peroxide. In particular, we address how to obtain visible-light photocatalysts which are stable with respect to aggregation and photochemical degradation. We report on the factors affecting efficiency and stability, including variable electron donors, oxygen partial pressure, pH, and molecular catalyst structure. The result is a perylene diimide derivative with unprecedented peroxide evolution performance using a broad range of organic donor molecules and operating in a wide pH range.

  @article{Gryszel_2023, abstract = {Photocatalytic generation of hydrogen peroxide, H2O2, has gained increasing attention in recent years, with applications ranging from solar energy conversion to biophysical research. While semiconducting solid-state materials are normally regarded as the workhorse for photogeneration of H2O2, an intriguing alternative for on-demand H2O2 is the use of photocatalytic organic dyes. Herein we report the use of water-soluble dyes based on perylene diimide molecules which behave as true molecular catalysts for the light-induced conversion of dissolved oxygen to hydrogen peroxide. In particular, we address how to obtain visible-light photocatalysts which are stable with respect to aggregation and photochemical degradation. We report on the factors affecting efficiency and stability, including variable electron donors, oxygen partial pressure, pH, and molecular catalyst structure. The result is a perylene diimide derivative with unprecedented peroxide evolution performance using a broad range of organic donor molecules and operating in a wide pH range.}, author = {Gryszel, Maciej and Schlossarek, Tim and Würthner, Frank and Natali, Mirco and Glowacki, Eric Daniel}, journal = {ChemPhotoChem}, keywords = {myown}, month = {06}, publisher = {Wiley}, title = {Water-Soluble Cationic Perylene Diimide Dyes as Stable Photocatalysts for H2O2 Evolution}, year = 2023 }

  %0 Journal Article %1 Gryszel_2023 %A Gryszel, Maciej %A Schlossarek, Tim %A Würthner, Frank %A Natali, Mirco %A Glowacki, Eric Daniel %D 2023 %I Wiley %J ChemPhotoChem %R 10.1002/cptc.202300070 %T Water-Soluble Cationic Perylene Diimide Dyes as Stable Photocatalysts for H2O2 Evolution %U https://doi.org/10.1002%2Fcptc.202300070 %X Photocatalytic generation of hydrogen peroxide, H2O2, has gained increasing attention in recent years, with applications ranging from solar energy conversion to biophysical research. While semiconducting solid-state materials are normally regarded as the workhorse for photogeneration of H2O2, an intriguing alternative for on-demand H2O2 is the use of photocatalytic organic dyes. Herein we report the use of water-soluble dyes based on perylene diimide molecules which behave as true molecular catalysts for the light-induced conversion of dissolved oxygen to hydrogen peroxide. In particular, we address how to obtain visible-light photocatalysts which are stable with respect to aggregation and photochemical degradation. We report on the factors affecting efficiency and stability, including variable electron donors, oxygen partial pressure, pH, and molecular catalyst structure. The result is a perylene diimide derivative with unprecedented peroxide evolution performance using a broad range of organic donor molecules and operating in a wide pH range.
• Playing Lego with perylene dyes. Dubey, Rajeev K.; Würthner, Frank. In Nat. Chem., 15(6), pp. 884–884. 2023.
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  @article{Dubey_2023, author = {Dubey, Rajeev K. and Würthner, Frank}, journal = {Nat. Chem.}, keywords = {myown}, month = {06}, number = 6, pages = {884–884}, publisher = {Springer Science and Business Media LLC}, title = {Playing Lego with perylene dyes}, volume = 15, year = 2023 }

  %0 Journal Article %1 Dubey_2023 %A Dubey, Rajeev K. %A Würthner, Frank %D 2023 %I Springer Science and Business Media LLC %J Nat. Chem. %N 6 %P 884--884 %R 10.1038/s41557-023-01202-4 %T Playing Lego with perylene dyes %U https://doi.org/10.1038%2Fs41557-023-01202-4 %V 15
• Preferential molecular recognition of heterochiral guests within a cyclophane receptor. Weh, Manuel; Shoyama, Kazutaka; Würthner, Frank. In Nature Communications, 14(1). 2023.
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  The discrimination of enantiomers by natural receptors is a well-established phenomenon. In contrast the number of synthetic receptors with the capability for enantioselective molecular recognition of chiral substrates is scarce and for chiral cyclophanes indicative for a preferential binding of homochiral guests. Here we introduce a cyclophane composed of two homochiral core-twisted perylene bisimide (PBI) units connected by p-xylylene spacers and demonstrate its preference for the complexation of [5]helicene of opposite helicity compared to the PBI units of the host. The pronounced enantio-differentiation of this molecular receptor for heterochiral guests can be utilized for the enrichment of the P-PBI-M-helicene-P-PBI epimeric bimolecular complex. Our experimental results are supported by DFT calculations, which reveal that the sterically demanding bay substituents attached to the PBI chromophores disturb the helical shape match of the perylene core and homochiral substrates and thereby enforce the formation of syndiotactic host-guest complex structures. Hence, the most efficient substrate binding is observed for those aromatic guests, e. g. perylene, [4]helicene, phenanthrene and biphenyl, that can easily adapt in non-planar axially chiral conformations due to their inherent conformational flexibility. In all cases the induced chirality for the guest is opposed to those of the embedding PBI units, leading to heterochiral host-guest structures.

  @article{Weh_2023, abstract = {The discrimination of enantiomers by natural receptors is a well-established phenomenon. In contrast the number of synthetic receptors with the capability for enantioselective molecular recognition of chiral substrates is scarce and for chiral cyclophanes indicative for a preferential binding of homochiral guests. Here we introduce a cyclophane composed of two homochiral core-twisted perylene bisimide (PBI) units connected by p-xylylene spacers and demonstrate its preference for the complexation of [5]helicene of opposite helicity compared to the PBI units of the host. The pronounced enantio-differentiation of this molecular receptor for heterochiral guests can be utilized for the enrichment of the P-PBI-M-helicene-P-PBI epimeric bimolecular complex. Our experimental results are supported by DFT calculations, which reveal that the sterically demanding bay substituents attached to the PBI chromophores disturb the helical shape match of the perylene core and homochiral substrates and thereby enforce the formation of syndiotactic host-guest complex structures. Hence, the most efficient substrate binding is observed for those aromatic guests, e. g. perylene, [4]helicene, phenanthrene and biphenyl, that can easily adapt in non-planar axially chiral conformations due to their inherent conformational flexibility. In all cases the induced chirality for the guest is opposed to those of the embedding PBI units, leading to heterochiral host-guest structures.}, author = {Weh, Manuel and Shoyama, Kazutaka and Würthner, Frank}, journal = {Nature Communications}, keywords = {myown}, month = {01}, number = 1, publisher = {Springer Science and Business Media {LLC}}, title = {Preferential molecular recognition of heterochiral guests within a cyclophane receptor}, volume = 14, year = 2023 }

  %0 Journal Article %1 Weh_2023 %A Weh, Manuel %A Shoyama, Kazutaka %A Würthner, Frank %D 2023 %I Springer Science and Business Media LLC %J Nature Communications %N 1 %R 10.1038/s41467-023-35851-3 %T Preferential molecular recognition of heterochiral guests within a cyclophane receptor %U https://doi.org/10.1038%2Fs41467-023-35851-3 %V 14 %X The discrimination of enantiomers by natural receptors is a well-established phenomenon. In contrast the number of synthetic receptors with the capability for enantioselective molecular recognition of chiral substrates is scarce and for chiral cyclophanes indicative for a preferential binding of homochiral guests. Here we introduce a cyclophane composed of two homochiral core-twisted perylene bisimide (PBI) units connected by p-xylylene spacers and demonstrate its preference for the complexation of [5]helicene of opposite helicity compared to the PBI units of the host. The pronounced enantio-differentiation of this molecular receptor for heterochiral guests can be utilized for the enrichment of the P-PBI-M-helicene-P-PBI epimeric bimolecular complex. Our experimental results are supported by DFT calculations, which reveal that the sterically demanding bay substituents attached to the PBI chromophores disturb the helical shape match of the perylene core and homochiral substrates and thereby enforce the formation of syndiotactic host-guest complex structures. Hence, the most efficient substrate binding is observed for those aromatic guests, e. g. perylene, [4]helicene, phenanthrene and biphenyl, that can easily adapt in non-planar axially chiral conformations due to their inherent conformational flexibility. In all cases the induced chirality for the guest is opposed to those of the embedding PBI units, leading to heterochiral host-guest structures.
• Anomalous deep-red luminescence of perylene black analogues with strong $\pi$-$\pi$ interactions. Tang, Ningning; Zhou, Jiadong; Wang, Liangxuan; Stolte, Matthias; Xie, Guojing; Wen, Xinbo; Liu, Linlin; W\"urthner, Frank; Gierschner, Johannes; Xie, Zengqi. In Nat. Commun., 14(1), p. 1922. 2023.
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  Perylene bisimide (PBI) dyes are known as red, maroon and black pigments, whose colors depend on the close $\pi$−$\pi$ stacking arrangement. However, contrary to the luminescent monomers, deep-red and black PBI pigments are commonly non- or only weakly fluorescent due to (multiple) quenching pathways. Here, we introduce N-alkoxybenzyl substituted PBIs that contain close $\pi$ stacking arrangement (exhibiting d$\pi$−$\pi$ ≈ 3.5\thinspace\AA, and longitudinal and transversal displacements of 3.1\thinspace\AA and 1.3\thinspace\AA); however, they afford deep-red emitters with solid-state fluorescence quantum yields ($\Phi$F) of up to 60\%. Systematic photophysical and computational studies in solution and in the solid state reveal a sensitive interconversion of the PBI-centred locally excited state and a charge transfer state, which depends on the dihedral angle ($\theta$) between the benzyl and alkoxy groups. This effectively controls the emission process, and enables high $\Phi$F by circumventing the common quenching pathways commonly observed for perylene black analogues.

  @article{Tang2023, abstract = {Perylene bisimide (PBI) dyes are known as red, maroon and black pigments, whose colors depend on the close $\pi$−$\pi$ stacking arrangement. However, contrary to the luminescent monomers, deep-red and black PBI pigments are commonly non- or only weakly fluorescent due to (multiple) quenching pathways. Here, we introduce N-alkoxybenzyl substituted PBIs that contain close $\pi$ stacking arrangement (exhibiting d$\pi$−$\pi$ ≈ 3.5{\thinspace}{\AA}, and longitudinal and transversal displacements of 3.1{\thinspace}{\AA} and 1.3{\thinspace}{\AA}); however, they afford deep-red emitters with solid-state fluorescence quantum yields ($\Phi$F) of up to 60{\%}. Systematic photophysical and computational studies in solution and in the solid state reveal a sensitive interconversion of the PBI-centred locally excited state and a charge transfer state, which depends on the dihedral angle ($\theta$) between the benzyl and alkoxy groups. This effectively controls the emission process, and enables high $\Phi$F by circumventing the common quenching pathways commonly observed for perylene black analogues.}, author = {Tang, Ningning and Zhou, Jiadong and Wang, Liangxuan and Stolte, Matthias and Xie, Guojing and Wen, Xinbo and Liu, Linlin and W{\"u}rthner, Frank and Gierschner, Johannes and Xie, Zengqi}, journal = {Nat. Commun.}, keywords = {myown}, month = {04}, number = 1, pages = 1922, title = {Anomalous deep-red luminescence of perylene black analogues with strong $\pi$-$\pi$ interactions}, volume = 14, year = 2023 }

  %0 Journal Article %1 Tang2023 %A Tang, Ningning %A Zhou, Jiadong %A Wang, Liangxuan %A Stolte, Matthias %A Xie, Guojing %A Wen, Xinbo %A Liu, Linlin %A W\"urthner, Frank %A Gierschner, Johannes %A Xie, Zengqi %D 2023 %J Nat. Commun. %N 1 %P 1922 %R 10.1038/s41467-023-37171-y %T Anomalous deep-red luminescence of perylene black analogues with strong $\pi$-$\pi$ interactions %U https://doi.org/10.1038/s41467-023-37171-y %V 14 %X Perylene bisimide (PBI) dyes are known as red, maroon and black pigments, whose colors depend on the close $\pi$−$\pi$ stacking arrangement. However, contrary to the luminescent monomers, deep-red and black PBI pigments are commonly non- or only weakly fluorescent due to (multiple) quenching pathways. Here, we introduce N-alkoxybenzyl substituted PBIs that contain close $\pi$ stacking arrangement (exhibiting d$\pi$−$\pi$ ≈ 3.5\thinspace\AA, and longitudinal and transversal displacements of 3.1\thinspace\AA and 1.3\thinspace\AA); however, they afford deep-red emitters with solid-state fluorescence quantum yields ($\Phi$F) of up to 60\%. Systematic photophysical and computational studies in solution and in the solid state reveal a sensitive interconversion of the PBI-centred locally excited state and a charge transfer state, which depends on the dihedral angle ($\theta$) between the benzyl and alkoxy groups. This effectively controls the emission process, and enables high $\Phi$F by circumventing the common quenching pathways commonly observed for perylene black analogues.
• Donor–acceptor complex formation by social self-sorting of polycyclic aromatic hydrocarbons and perylene bisimides. Soldner, Simon; Anhalt, Olga; Sárosi, Menyhárt B.; Stolte, Matthias; Würthner, Frank. In Chem. Commun., 59(78), pp. 11656–11659. 2023.
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  Self-assembly versus complexation with polycyclic aromatic hydrocarbon (PAH) guest molecules is studied for a series of perylene bisimides (PBIs). Bulky imide substituents at the PBI guide their self-assembly into dimer aggregates with null-type exciton coupling. Host–guest titration experiments with perylene and triphenylene PAHs afford 1 : 1 and 1 : 2 complexes whose properties are studied by single crystal X-ray analysis and UV/Vis and fluorescence spectroscopy.

  @article{D3CC03704E, abstract = {Self-assembly versus complexation with polycyclic aromatic hydrocarbon (PAH) guest molecules is studied for a series of perylene bisimides (PBIs). Bulky imide substituents at the PBI guide their self-assembly into dimer aggregates with null-type exciton coupling. Host–guest titration experiments with perylene and triphenylene PAHs afford 1 : 1 and 1 : 2 complexes whose properties are studied by single crystal X-ray analysis and UV/Vis and fluorescence spectroscopy.}, author = {Soldner, Simon and Anhalt, Olga and Sárosi, Menyhárt B. and Stolte, Matthias and Würthner, Frank}, journal = {Chem. Commun.}, keywords = {myown}, number = 78, pages = {11656-11659}, title = {Donor–acceptor complex formation by social self-sorting of polycyclic aromatic hydrocarbons and perylene bisimides}, volume = 59, year = 2023 }

  %0 Journal Article %1 D3CC03704E %A Soldner, Simon %A Anhalt, Olga %A Sárosi, Menyhárt B. %A Stolte, Matthias %A Würthner, Frank %D 2023 %J Chem. Commun. %N 78 %P 11656-11659 %R 10.1039/D3CC03704E %T Donor–acceptor complex formation by social self-sorting of polycyclic aromatic hydrocarbons and perylene bisimides %U http://dx.doi.org/10.1039/D3CC03704E %V 59 %X Self-assembly versus complexation with polycyclic aromatic hydrocarbon (PAH) guest molecules is studied for a series of perylene bisimides (PBIs). Bulky imide substituents at the PBI guide their self-assembly into dimer aggregates with null-type exciton coupling. Host–guest titration experiments with perylene and triphenylene PAHs afford 1 : 1 and 1 : 2 complexes whose properties are studied by single crystal X-ray analysis and UV/Vis and fluorescence spectroscopy.
• Naphthalimide-Annulated [n]Helicenes: Red Circularly Polarized Light Emitters. Tian, Xiaoqi; Shoyama, Kazutaka; Mahlmeister, Bernhard; Brust, Felix; Stolte, Matthias; Würthner, Frank. In J. Am. Chem. Soc. 2023.
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  Two [n]heliceno-bis(naphthalimides) 1 and 2 (n = 5 and 6, respectively) where two electron-accepting naphthalimide moieties are attached at both ends of helicene core were synthesized by effective two-step strategy, and their enantiomers could be resolved by chiral stationary-phase high-performance liquid chromatography (HPLC). The single-crystal X-ray diffraction analysis of enantiopure fractions of 1 and 2 confirmed their helical structure, and together with experimental and calculated circular dichroism (CD) spectra, the absolute configuration was unambiguously assigned. Both 1 and 2 exhibit high molar extinction coefficients for the S0–S1 transition and high fluorescence quantum yields (73% for 1 and 69% for 2), both being outstanding for helicene derivatives. The red circularly polarized luminescence (CPL) emission up to 615 nm for 2 with CPL brightness (BCPL) up to 66.5 M–1 cm–1 demonstrates its potential for applications in chiral optoelectronics. Time-dependent density functional theory (TD-DFT) calculations unambiguously showed that the large transition magnetic dipole moment |m| of 2 is responsible for its high absorbance dissymmetry (gabs) and luminescence dissymmetry (glum) factor.

  @article{Tian_2023, abstract = {Two [n]heliceno-bis(naphthalimides) 1 and 2 (n = 5 and 6, respectively) where two electron-accepting naphthalimide moieties are attached at both ends of helicene core were synthesized by effective two-step strategy, and their enantiomers could be resolved by chiral stationary-phase high-performance liquid chromatography (HPLC). The single-crystal X-ray diffraction analysis of enantiopure fractions of 1 and 2 confirmed their helical structure, and together with experimental and calculated circular dichroism (CD) spectra, the absolute configuration was unambiguously assigned. Both 1 and 2 exhibit high molar extinction coefficients for the S0–S1 transition and high fluorescence quantum yields (73% for 1 and 69% for 2), both being outstanding for helicene derivatives. The red circularly polarized luminescence (CPL) emission up to 615 nm for 2 with CPL brightness (BCPL) up to 66.5 M–1 cm–1 demonstrates its potential for applications in chiral optoelectronics. Time-dependent density functional theory (TD-DFT) calculations unambiguously showed that the large transition magnetic dipole moment |m| of 2 is responsible for its high absorbance dissymmetry (gabs) and luminescence dissymmetry (glum) factor.}, author = {Tian, Xiaoqi and Shoyama, Kazutaka and Mahlmeister, Bernhard and Brust, Felix and Stolte, Matthias and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {04}, publisher = {American Chemical Society (ACS)}, title = {Naphthalimide-Annulated [n]Helicenes: Red Circularly Polarized Light Emitters}, year = 2023 }

  %0 Journal Article %1 Tian_2023 %A Tian, Xiaoqi %A Shoyama, Kazutaka %A Mahlmeister, Bernhard %A Brust, Felix %A Stolte, Matthias %A Würthner, Frank %D 2023 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %R 10.1021/jacs.3c03441 %T Naphthalimide-Annulated [n]Helicenes: Red Circularly Polarized Light Emitters %U https://doi.org/10.1021%2Fjacs.3c03441 %X Two [n]heliceno-bis(naphthalimides) 1 and 2 (n = 5 and 6, respectively) where two electron-accepting naphthalimide moieties are attached at both ends of helicene core were synthesized by effective two-step strategy, and their enantiomers could be resolved by chiral stationary-phase high-performance liquid chromatography (HPLC). The single-crystal X-ray diffraction analysis of enantiopure fractions of 1 and 2 confirmed their helical structure, and together with experimental and calculated circular dichroism (CD) spectra, the absolute configuration was unambiguously assigned. Both 1 and 2 exhibit high molar extinction coefficients for the S0–S1 transition and high fluorescence quantum yields (73% for 1 and 69% for 2), both being outstanding for helicene derivatives. The red circularly polarized luminescence (CPL) emission up to 615 nm for 2 with CPL brightness (BCPL) up to 66.5 M–1 cm–1 demonstrates its potential for applications in chiral optoelectronics. Time-dependent density functional theory (TD-DFT) calculations unambiguously showed that the large transition magnetic dipole moment |m| of 2 is responsible for its high absorbance dissymmetry (gabs) and luminescence dissymmetry (glum) factor.
• Controlling the Supramolecular Polymerization of Squaraine Dyes by a Molecular Chaperone Analogue. Kleine-Kleffmann, Lara; Stepanenko, Vladimir; Shoyama, Kazutaka; Wehner, Marius; Würthner, Frank. In J. Am. Chem. Soc. 2023.
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  Molecular chaperones are proteins that assist in the (un)folding and (dis)assembly of other macromolecular structures toward their biologically functional state in a non-covalent manner. Transferring this concept from nature to artificial self-assembly processes, here, we show a new strategy to control supramolecular polymerization via a chaperone-like two-component system. A new kinetic trapping method was developed that enables efficient retardation of the spontaneous self-assembly of a squaraine dye monomer. The suppression of supramolecular polymerization could be regulated with a cofactor, which precisely initiates self-assembly. The presented system was investigated and characterized by ultraviolet–visible, Fourier transform infrared, and nuclear magnetic resonance spectroscopy, atomic force microscopy, isothermal titration calorimetry, and single-crystal X-ray diffraction. With these results, living supramolecular polymerization and block copolymer fabrication could be realized, demonstrating a new possibility for effective control over supramolecular polymerization processes.

  @article{Kleine_Kleffmann_2023, abstract = {Molecular chaperones are proteins that assist in the (un)folding and (dis)assembly of other macromolecular structures toward their biologically functional state in a non-covalent manner. Transferring this concept from nature to artificial self-assembly processes, here, we show a new strategy to control supramolecular polymerization via a chaperone-like two-component system. A new kinetic trapping method was developed that enables efficient retardation of the spontaneous self-assembly of a squaraine dye monomer. The suppression of supramolecular polymerization could be regulated with a cofactor, which precisely initiates self-assembly. The presented system was investigated and characterized by ultraviolet–visible, Fourier transform infrared, and nuclear magnetic resonance spectroscopy, atomic force microscopy, isothermal titration calorimetry, and single-crystal X-ray diffraction. With these results, living supramolecular polymerization and block copolymer fabrication could be realized, demonstrating a new possibility for effective control over supramolecular polymerization processes.}, author = {Kleine-Kleffmann, Lara and Stepanenko, Vladimir and Shoyama, Kazutaka and Wehner, Marius and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {04}, publisher = {American Chemical Society ({ACS})}, title = {Controlling the Supramolecular Polymerization of Squaraine Dyes by a Molecular Chaperone Analogue}, year = 2023 }

  %0 Journal Article %1 Kleine_Kleffmann_2023 %A Kleine-Kleffmann, Lara %A Stepanenko, Vladimir %A Shoyama, Kazutaka %A Wehner, Marius %A Würthner, Frank %D 2023 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %R 10.1021/jacs.3c01002 %T Controlling the Supramolecular Polymerization of Squaraine Dyes by a Molecular Chaperone Analogue %U https://doi.org/10.1021%2Fjacs.3c01002 %X Molecular chaperones are proteins that assist in the (un)folding and (dis)assembly of other macromolecular structures toward their biologically functional state in a non-covalent manner. Transferring this concept from nature to artificial self-assembly processes, here, we show a new strategy to control supramolecular polymerization via a chaperone-like two-component system. A new kinetic trapping method was developed that enables efficient retardation of the spontaneous self-assembly of a squaraine dye monomer. The suppression of supramolecular polymerization could be regulated with a cofactor, which precisely initiates self-assembly. The presented system was investigated and characterized by ultraviolet–visible, Fourier transform infrared, and nuclear magnetic resonance spectroscopy, atomic force microscopy, isothermal titration calorimetry, and single-crystal X-ray diffraction. With these results, living supramolecular polymerization and block copolymer fabrication could be realized, demonstrating a new possibility for effective control over supramolecular polymerization processes.
• π-π Catalysis Made Asymmetric-Enantiomerization Catalysis Mediated by the Chiral π-System of a Perylene Bisimide Cyclophane. Weh, Manuel; Kroeger, Asja A.; Shoyama, Kazutaka; Grüne, Matthias; Karton, Amir; Würthner, Frank. In Angew. Chem. Int. Ed., 62(19). 2023.
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  Enzymes actuate catalysis through a combination of transition state stabilization and ground state destabilization, inducing enantioselectivity through chiral binding sites. Here, we present a supramolecular model system which employs these basic principles to catalyze the enantiomerization of [5]helicene. Catalysis is hereby mediated not through a network of functional groups but through π-π catalysis exerted from the curved aromatic framework of a chiral perylene bisimide (PBI) cyclophane offering a binding pocket that is intricately complementary with the enantiomerization transition structure. Although transition state stabilization originates simply from dispersion and electrostatic interactions, enantiomerization kinetics are accelerated by a factor of ca. 700 at 295 K. Comparison with the meso-congener of the catalytically active cyclophane shows that upon configurational inversion in only one PBI moiety the catalytic effect is lost, highlighting the importance of precise transition structure recognition in supramolecular enzyme mimics.

  @article{Weh_2023, abstract = {Enzymes actuate catalysis through a combination of transition state stabilization and ground state destabilization, inducing enantioselectivity through chiral binding sites. Here, we present a supramolecular model system which employs these basic principles to catalyze the enantiomerization of [5]helicene. Catalysis is hereby mediated not through a network of functional groups but through π-π catalysis exerted from the curved aromatic framework of a chiral perylene bisimide (PBI) cyclophane offering a binding pocket that is intricately complementary with the enantiomerization transition structure. Although transition state stabilization originates simply from dispersion and electrostatic interactions, enantiomerization kinetics are accelerated by a factor of ca. 700 at 295 K. Comparison with the meso-congener of the catalytically active cyclophane shows that upon configurational inversion in only one PBI moiety the catalytic effect is lost, highlighting the importance of precise transition structure recognition in supramolecular enzyme mimics.}, author = {Weh, Manuel and Kroeger, Asja A. and Shoyama, Kazutaka and Grüne, Matthias and Karton, Amir and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {04}, number = 19, publisher = {Wiley}, title = {π-π Catalysis Made Asymmetric-Enantiomerization Catalysis Mediated by the Chiral π-System of a Perylene Bisimide Cyclophane}, volume = 62, year = 2023 }

  %0 Journal Article %1 Weh_2023 %A Weh, Manuel %A Kroeger, Asja A. %A Shoyama, Kazutaka %A Grüne, Matthias %A Karton, Amir %A Würthner, Frank %D 2023 %I Wiley %J Angew. Chem. Int. Ed. %N 19 %R 10.1002/anie.202301301 %T π-π Catalysis Made Asymmetric-Enantiomerization Catalysis Mediated by the Chiral π-System of a Perylene Bisimide Cyclophane %U https://doi.org/10.1002%2Fanie.202301301 %V 62 %X Enzymes actuate catalysis through a combination of transition state stabilization and ground state destabilization, inducing enantioselectivity through chiral binding sites. Here, we present a supramolecular model system which employs these basic principles to catalyze the enantiomerization of [5]helicene. Catalysis is hereby mediated not through a network of functional groups but through π-π catalysis exerted from the curved aromatic framework of a chiral perylene bisimide (PBI) cyclophane offering a binding pocket that is intricately complementary with the enantiomerization transition structure. Although transition state stabilization originates simply from dispersion and electrostatic interactions, enantiomerization kinetics are accelerated by a factor of ca. 700 at 295 K. Comparison with the meso-congener of the catalytically active cyclophane shows that upon configurational inversion in only one PBI moiety the catalytic effect is lost, highlighting the importance of precise transition structure recognition in supramolecular enzyme mimics.
• Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds. Malone, Ryan J.; Spengler, Jonas; Carmichael, Rachael A.; Ngo, Khoa; Würthner, Frank; Chalifoux, Wesley A. In Org. Lett., 25(1), pp. 226–230. 2023.
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  Achiral and chiral isomers of dipyrenoheteroles were synthesized via alkyne benzannulation. The electronic properties of these compounds were examined using cyclic voltammetry and differential pulse voltammetry. The enantiomers of the chiral isomers were separated, and their optical properties were examined in circular dichroism and circularly polarized luminescence studies. The chiral isomers exhibited a large bathochromic shift, relative to the achiral isomer, in both absorbance and fluorescence, resulting from decreased symmetry, rather than a change in the size of the backbone.

  @article{Malone_2023, abstract = {Achiral and chiral isomers of dipyrenoheteroles were synthesized via alkyne benzannulation. The electronic properties of these compounds were examined using cyclic voltammetry and differential pulse voltammetry. The enantiomers of the chiral isomers were separated, and their optical properties were examined in circular dichroism and circularly polarized luminescence studies. The chiral isomers exhibited a large bathochromic shift, relative to the achiral isomer, in both absorbance and fluorescence, resulting from decreased symmetry, rather than a change in the size of the backbone.}, author = {Malone, Ryan J. and Spengler, Jonas and Carmichael, Rachael A. and Ngo, Khoa and Würthner, Frank and Chalifoux, Wesley A.}, journal = {Org. Lett.}, keywords = {myown}, month = {01}, number = 1, pages = {226–230}, publisher = {American Chemical Society ({ACS})}, title = {Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds}, volume = 25, year = 2023 }

  %0 Journal Article %1 Malone_2023 %A Malone, Ryan J. %A Spengler, Jonas %A Carmichael, Rachael A. %A Ngo, Khoa %A Würthner, Frank %A Chalifoux, Wesley A. %D 2023 %I American Chemical Society (ACS) %J Org. Lett. %N 1 %P 226--230 %R 10.1021/acs.orglett.2c04071 %T Synthesis and Properties of Achiral and Chiral Dipyrenoheteroles and Related Compounds %U https://doi.org/10.1021%2Facs.orglett.2c04071 %V 25 %X Achiral and chiral isomers of dipyrenoheteroles were synthesized via alkyne benzannulation. The electronic properties of these compounds were examined using cyclic voltammetry and differential pulse voltammetry. The enantiomers of the chiral isomers were separated, and their optical properties were examined in circular dichroism and circularly polarized luminescence studies. The chiral isomers exhibited a large bathochromic shift, relative to the achiral isomer, in both absorbance and fluorescence, resulting from decreased symmetry, rather than a change in the size of the backbone.
• Growth of Merocyanine Dye J‐Aggregate Nanosheets by Living Supramolecular Polymerization. Kleine‐Kleffmann, Lara; Schulz, Alexander; Stepanenko, Vladimir; Würthner, Frank. In Angew. Chem. Int. Ed. 2023.
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  @article{Kleine_Kleffmann_2023, author = {Kleine‐Kleffmann, Lara and Schulz, Alexander and Stepanenko, Vladimir and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = 11, title = {Growth of Merocyanine Dye J‐Aggregate Nanosheets by Living Supramolecular Polymerization}, year = 2023 }

  %0 Journal Article %1 Kleine_Kleffmann_2023 %A Kleine‐Kleffmann, Lara %A Schulz, Alexander %A Stepanenko, Vladimir %A Würthner, Frank %D 2023 %J Angew. Chem. Int. Ed. %R 10.1002/anie.202314667 %T Growth of Merocyanine Dye J‐Aggregate Nanosheets by Living Supramolecular Polymerization %U http://dx.doi.org/10.1002/anie.202314667
• Unveiling the intersystem crossing dynamics in N-annulated perylene bisimides. Sunny, Jeswin; Sebastian, Ebin; Sujilkumar, Suvarna; Würthner, Frank; Engels, Bernd; Hariharan, Mahesh. In Phys. Chem. Chem. Phys., p. -. 2023.
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  The efficient population of the triplet excited states in heavy metal-free organic chromophores has been one of the long-standing research problems to molecular photochemists. The negligible spin–orbit coupling matrix elements in the purely organic chromophores and the large singlet–triplet energy gap (ΔES–T) pose a hurdle for ultrafast intersystem crossing (ISC). Herein we report the unprecedented population of triplet manifold in a series of nitrogen-annulated perylene bisimide chromophores (NPBI and Br-NPBI). NPBI is found to have a moderate fluorescence quantum yield (Φf = 68 ± 5%), whereas Br-NPBI showcased a low fluorescence quantum yield (Φf = 2.0 ± 0.6%) in toluene. The femtosecond transient absorption measurements of Br-NPBI revealed ultrafast ISC (kISC = 1.97 × 1010 s−1) from the initially populated singlet excited state to the long-lived triplet excited states. The triplet quantum yields (ΦT = 95.2 ± 4.6% for Br-NPBI, ΦT = 18.7 ± 2.3% for NPBI) calculated from nanosecond transient absorption spectroscopy measurements showed the enhancement in triplet population upon bromine substitution. The quantum chemical calculations revealed the explicit role of nitrogen annulation in tuning the excited state energy levels to favor the ISC. The near degeneracy between the singlet and triplet excited states observed in NPBI and Br-NPBI (ΔES–T = −0.01 eV for NPBI, ΔES–T = 0.03 eV for Br-NPBI) facilitates the spin flipping in the molecules. Nitrogen annulation emerges as a design strategy to open up the ISC pathway and the rate of which can be further enhanced by the substitution of a heavier element.

  @article{D3CP03888B, abstract = {The efficient population of the triplet excited states in heavy metal-free organic chromophores has been one of the long-standing research problems to molecular photochemists. The negligible spin–orbit coupling matrix elements in the purely organic chromophores and the large singlet–triplet energy gap (ΔES–T) pose a hurdle for ultrafast intersystem crossing (ISC). Herein we report the unprecedented population of triplet manifold in a series of nitrogen-annulated perylene bisimide chromophores (NPBI and Br-NPBI). NPBI is found to have a moderate fluorescence quantum yield (Φf = 68 ± 5%), whereas Br-NPBI showcased a low fluorescence quantum yield (Φf = 2.0 ± 0.6%) in toluene. The femtosecond transient absorption measurements of Br-NPBI revealed ultrafast ISC (kISC = 1.97 × 1010 s−1) from the initially populated singlet excited state to the long-lived triplet excited states. The triplet quantum yields (ΦT = 95.2 ± 4.6% for Br-NPBI, ΦT = 18.7 ± 2.3% for NPBI) calculated from nanosecond transient absorption spectroscopy measurements showed the enhancement in triplet population upon bromine substitution. The quantum chemical calculations revealed the explicit role of nitrogen annulation in tuning the excited state energy levels to favor the ISC. The near degeneracy between the singlet and triplet excited states observed in NPBI and Br-NPBI (ΔES–T = −0.01 eV for NPBI{,} ΔES–T = 0.03 eV for Br-NPBI) facilitates the spin flipping in the molecules. Nitrogen annulation emerges as a design strategy to open up the ISC pathway and the rate of which can be further enhanced by the substitution of a heavier element.}, author = {Sunny, Jeswin and Sebastian, Ebin and Sujilkumar, Suvarna and Würthner, Frank and Engels, Bernd and Hariharan, Mahesh}, journal = {Phys. Chem. Chem. Phys.}, keywords = {myown}, pages = {-}, title = {Unveiling the intersystem crossing dynamics in N-annulated perylene bisimides}, year = 2023 }

  %0 Journal Article %1 D3CP03888B %A Sunny, Jeswin %A Sebastian, Ebin %A Sujilkumar, Suvarna %A Würthner, Frank %A Engels, Bernd %A Hariharan, Mahesh %D 2023 %J Phys. Chem. Chem. Phys. %P - %R 10.1039/D3CP03888B %T Unveiling the intersystem crossing dynamics in N-annulated perylene bisimides %U http://dx.doi.org/10.1039/D3CP03888B %X The efficient population of the triplet excited states in heavy metal-free organic chromophores has been one of the long-standing research problems to molecular photochemists. The negligible spin–orbit coupling matrix elements in the purely organic chromophores and the large singlet–triplet energy gap (ΔES–T) pose a hurdle for ultrafast intersystem crossing (ISC). Herein we report the unprecedented population of triplet manifold in a series of nitrogen-annulated perylene bisimide chromophores (NPBI and Br-NPBI). NPBI is found to have a moderate fluorescence quantum yield (Φf = 68 ± 5%), whereas Br-NPBI showcased a low fluorescence quantum yield (Φf = 2.0 ± 0.6%) in toluene. The femtosecond transient absorption measurements of Br-NPBI revealed ultrafast ISC (kISC = 1.97 × 1010 s−1) from the initially populated singlet excited state to the long-lived triplet excited states. The triplet quantum yields (ΦT = 95.2 ± 4.6% for Br-NPBI, ΦT = 18.7 ± 2.3% for NPBI) calculated from nanosecond transient absorption spectroscopy measurements showed the enhancement in triplet population upon bromine substitution. The quantum chemical calculations revealed the explicit role of nitrogen annulation in tuning the excited state energy levels to favor the ISC. The near degeneracy between the singlet and triplet excited states observed in NPBI and Br-NPBI (ΔES–T = −0.01 eV for NPBI, ΔES–T = 0.03 eV for Br-NPBI) facilitates the spin flipping in the molecules. Nitrogen annulation emerges as a design strategy to open up the ISC pathway and the rate of which can be further enhanced by the substitution of a heavier element.
• Chiroptical Properties of Planar Benzobisthiazole-Bridged Squaraine Dimers. Freytag, Emely; Kreimendahl, Lasse; Holzapfel, Marco; Petersen, Jens; Lackinger, Heiko; Stolte, Matthias; Würthner, Frank; Mitric, Roland; Lambert, Christoph. In J. Org. Chem., 88(15), pp. 10777–10788. 2023.
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  Five chiral squaraine dimers were synthesized by fusing chiral indolenine semisquaraines with three different benzobisthiazole bridges. The thereby created squaraine dimers show a strong splitting of the lowest energy absorption bands caused by exciton coupling. The intensities of the two exciton transitions and the energetic splitting depend on the angle of the two squaraine moieties within the chromophore dimer. The electric circular dichroism spectra of the dimers show intense Cotton effects whose sign depends on the used squaraine chromophores. Sizable anisotropies gabs of up to 2.6 × 10–3 could be obtained. TD-DFT calculations were used to partition the rotational strength into the three Rosenfeld terms where the electric-magnetic coupling turned out to be the dominant contribution while the exciton chirality term is much smaller. This is because the chromophore dimers are essentially planar but the angle between the electric transition dipole moment of one squaraine and the magnetic transition dipole moment of the other squaraine strongly deviates from 90°, which makes the dot product between the two moment vectors and, thus, the rotational strength substantial.

  @article{Freytag_2023, abstract = {Five chiral squaraine dimers were synthesized by fusing chiral indolenine semisquaraines with three different benzobisthiazole bridges. The thereby created squaraine dimers show a strong splitting of the lowest energy absorption bands caused by exciton coupling. The intensities of the two exciton transitions and the energetic splitting depend on the angle of the two squaraine moieties within the chromophore dimer. The electric circular dichroism spectra of the dimers show intense Cotton effects whose sign depends on the used squaraine chromophores. Sizable anisotropies gabs of up to 2.6 × 10–3 could be obtained. TD-DFT calculations were used to partition the rotational strength into the three Rosenfeld terms where the electric-magnetic coupling turned out to be the dominant contribution while the exciton chirality term is much smaller. This is because the chromophore dimers are essentially planar but the angle between the electric transition dipole moment of one squaraine and the magnetic transition dipole moment of the other squaraine strongly deviates from 90°, which makes the dot product between the two moment vectors and, thus, the rotational strength substantial.}, author = {Freytag, Emely and Kreimendahl, Lasse and Holzapfel, Marco and Petersen, Jens and Lackinger, Heiko and Stolte, Matthias and Würthner, Frank and Mitric, Roland and Lambert, Christoph}, journal = {J. Org. Chem.}, keywords = {myown}, month = {07}, number = 15, pages = {10777–10788}, title = {Chiroptical Properties of Planar Benzobisthiazole-Bridged Squaraine Dimers}, volume = 88, year = 2023 }

  %0 Journal Article %1 Freytag_2023 %A Freytag, Emely %A Kreimendahl, Lasse %A Holzapfel, Marco %A Petersen, Jens %A Lackinger, Heiko %A Stolte, Matthias %A Würthner, Frank %A Mitric, Roland %A Lambert, Christoph %D 2023 %J J. Org. Chem. %N 15 %P 10777--10788 %R 10.1021/acs.joc.3c00821 %T Chiroptical Properties of Planar Benzobisthiazole-Bridged Squaraine Dimers %U https://doi.org/10.1021%2Facs.joc.3c00821 %V 88 %X Five chiral squaraine dimers were synthesized by fusing chiral indolenine semisquaraines with three different benzobisthiazole bridges. The thereby created squaraine dimers show a strong splitting of the lowest energy absorption bands caused by exciton coupling. The intensities of the two exciton transitions and the energetic splitting depend on the angle of the two squaraine moieties within the chromophore dimer. The electric circular dichroism spectra of the dimers show intense Cotton effects whose sign depends on the used squaraine chromophores. Sizable anisotropies gabs of up to 2.6 × 10–3 could be obtained. TD-DFT calculations were used to partition the rotational strength into the three Rosenfeld terms where the electric-magnetic coupling turned out to be the dominant contribution while the exciton chirality term is much smaller. This is because the chromophore dimers are essentially planar but the angle between the electric transition dipole moment of one squaraine and the magnetic transition dipole moment of the other squaraine strongly deviates from 90°, which makes the dot product between the two moment vectors and, thus, the rotational strength substantial.
• Enantiopure J-Aggregate of Quaterrylene Bisimides for Strong Chiroptical NIR-Response. Mahlmeister, Bernhard; Schembri, Tim; Stepanenko, Vladimir; Shoyama, Kazutaka; Stolte, Matthias; Würthner, Frank. In J. Am. Chem. Soc., 145(24), pp. 13302–13311. 2023.
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  Chiral polycyclic aromatic hydrocarbons can be tailored for next-generation photonic materials by carefully designing their molecular as well as supramolecular architectures. Hence, excitonic coupling can boost the chiroptical response in extended aggregates but is still challenging to achieve by pure self-assembly. Whereas most reports on these potential materials cover the UV and visible spectral range, systems in the near infrared (NIR) are underdeveloped. We report a new quaterrylene bisimide derivative with a conformationally stable twisted π-backbone enabled by the sterical congestion of a fourfold bay-arylation. Rendering the π-subplanes accessible by small imide substituents allows for a slip-stacked chiral arrangement by kinetic self-assembly in low polarity solvents. The well dispersed solid-state aggregate reveals a sharp optical signature of strong J-type excitonic coupling in both absorption (897 nm) and emission (912 nm) far in the NIR region and reaches absorption dissymmetry factors up to 1.1 × 10–2. The structural elucidation was achieved by atomic force microscopy and single-crystal X-ray analysis which we combined to derive a structural model of a fourfold stranded enantiopure superhelix. We could deduce that the role of phenyl substituents is not only granting stable axial chirality but also guiding the chromophore into a chiral supramolecular arrangement needed for strong excitonic chirality.

  @article{Mahlmeister_2023, abstract = {Chiral polycyclic aromatic hydrocarbons can be tailored for next-generation photonic materials by carefully designing their molecular as well as supramolecular architectures. Hence, excitonic coupling can boost the chiroptical response in extended aggregates but is still challenging to achieve by pure self-assembly. Whereas most reports on these potential materials cover the UV and visible spectral range, systems in the near infrared (NIR) are underdeveloped. We report a new quaterrylene bisimide derivative with a conformationally stable twisted π-backbone enabled by the sterical congestion of a fourfold bay-arylation. Rendering the π-subplanes accessible by small imide substituents allows for a slip-stacked chiral arrangement by kinetic self-assembly in low polarity solvents. The well dispersed solid-state aggregate reveals a sharp optical signature of strong J-type excitonic coupling in both absorption (897 nm) and emission (912 nm) far in the NIR region and reaches absorption dissymmetry factors up to 1.1 × 10–2. The structural elucidation was achieved by atomic force microscopy and single-crystal X-ray analysis which we combined to derive a structural model of a fourfold stranded enantiopure superhelix. We could deduce that the role of phenyl substituents is not only granting stable axial chirality but also guiding the chromophore into a chiral supramolecular arrangement needed for strong excitonic chirality.}, author = {Mahlmeister, Bernhard and Schembri, Tim and Stepanenko, Vladimir and Shoyama, Kazutaka and Stolte, Matthias and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {06}, number = 24, pages = {13302–13311}, publisher = {American Chemical Society (ACS)}, title = {Enantiopure J-Aggregate of Quaterrylene Bisimides for Strong Chiroptical NIR-Response}, volume = 145, year = 2023 }

  %0 Journal Article %1 Mahlmeister_2023 %A Mahlmeister, Bernhard %A Schembri, Tim %A Stepanenko, Vladimir %A Shoyama, Kazutaka %A Stolte, Matthias %A Würthner, Frank %D 2023 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 24 %P 13302--13311 %R 10.1021/jacs.3c03367 %T Enantiopure J-Aggregate of Quaterrylene Bisimides for Strong Chiroptical NIR-Response %U https://doi.org/10.1021%2Fjacs.3c03367 %V 145 %X Chiral polycyclic aromatic hydrocarbons can be tailored for next-generation photonic materials by carefully designing their molecular as well as supramolecular architectures. Hence, excitonic coupling can boost the chiroptical response in extended aggregates but is still challenging to achieve by pure self-assembly. Whereas most reports on these potential materials cover the UV and visible spectral range, systems in the near infrared (NIR) are underdeveloped. We report a new quaterrylene bisimide derivative with a conformationally stable twisted π-backbone enabled by the sterical congestion of a fourfold bay-arylation. Rendering the π-subplanes accessible by small imide substituents allows for a slip-stacked chiral arrangement by kinetic self-assembly in low polarity solvents. The well dispersed solid-state aggregate reveals a sharp optical signature of strong J-type excitonic coupling in both absorption (897 nm) and emission (912 nm) far in the NIR region and reaches absorption dissymmetry factors up to 1.1 × 10–2. The structural elucidation was achieved by atomic force microscopy and single-crystal X-ray analysis which we combined to derive a structural model of a fourfold stranded enantiopure superhelix. We could deduce that the role of phenyl substituents is not only granting stable axial chirality but also guiding the chromophore into a chiral supramolecular arrangement needed for strong excitonic chirality.

• 12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon. Mützel, Carina; Farrell, Jeffrey M.; Shoyama, Kazutaka; Würthner, Frank. In Angew. Chem. Int. Ed. 2022.
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  Herein we devise and execute a new synthesis of a pristine boron-doped nanographene. Our target boron-doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B-doping arrangement. Our synthesis of this target, a doubly B-doped hexabenzopentacene (B2-HBP), employs six net C H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr3/AlCl3/2,6-dichloropyridine- mediated C H borylation steps. As predicted by our calculations, B2-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B2-HBP possesses a very low LUMO level, showing two reversible reductions at 1.00 V and 1.17 V vs. Fc+/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B-doped polycyclic aromatic hydrocarbons.

  @article{Muetzel_2022, abstract = {Herein we devise and execute a new synthesis of a pristine boron-doped nanographene. Our target boron-doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B-doping arrangement. Our synthesis of this target, a doubly B-doped hexabenzopentacene (B2-HBP), employs six net C H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr3/AlCl3/2,6-dichloropyridine- mediated C H borylation steps. As predicted by our calculations, B2-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B2-HBP possesses a very low LUMO level, showing two reversible reductions at 1.00 V and 1.17 V vs. Fc+/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B-doped polycyclic aromatic hydrocarbons.}, author = {Mützel, Carina and Farrell, Jeffrey M. and Shoyama, Kazutaka and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {01}, publisher = {Wiley}, title = {12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon}, year = 2022 }

  %0 Journal Article %1 Muetzel_2022 %A Mützel, Carina %A Farrell, Jeffrey M. %A Shoyama, Kazutaka %A Würthner, Frank %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202115746 %T 12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon %U https://doi.org/10.1002%2Fanie.202115746 %X Herein we devise and execute a new synthesis of a pristine boron-doped nanographene. Our target boron-doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B-doping arrangement. Our synthesis of this target, a doubly B-doped hexabenzopentacene (B2-HBP), employs six net C H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr3/AlCl3/2,6-dichloropyridine- mediated C H borylation steps. As predicted by our calculations, B2-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B2-HBP possesses a very low LUMO level, showing two reversible reductions at 1.00 V and 1.17 V vs. Fc+/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B-doped polycyclic aromatic hydrocarbons.
• Self-Assembly of a Zinc Bacteriochlorophyll-d Analog with a Lipophilic Tertiary Amide Group in the 17-Substituent. Shoji, Sunao; Stepanenko, Vladimir; Würthner, Frank; Tamiaki, Hitoshi. In Bull. Chem. Soc. Jpn., 95(7), pp. 1083–1085. 2022.
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  Self-assembled aggregates of bacteriochlorophyll(BChl)-c/d/e pigments play key roles in major light-harvesting antenna systems of photosynthetic green bacteria. Herein, we report the self-assembly of a lipophilic zinc BChl-d model with an N,N-didodecylamide in the 17-substituent. The present model formed two types of J-aggregates, which formed under kinetic and thermodynamic controls.

  @article{Shoji_2022, abstract = {Self-assembled aggregates of bacteriochlorophyll(BChl)-c/d/e pigments play key roles in major light-harvesting antenna systems of photosynthetic green bacteria. Herein, we report the self-assembly of a lipophilic zinc BChl-d model with an N,N-didodecylamide in the 17-substituent. The present model formed two types of J-aggregates, which formed under kinetic and thermodynamic controls.}, author = {Shoji, Sunao and Stepanenko, Vladimir and Würthner, Frank and Tamiaki, Hitoshi}, journal = {Bull. Chem. Soc. Jpn.}, keywords = {myown}, month = {07}, number = 7, pages = {1083–1085}, publisher = {The Chemical Society of Japan}, title = {Self-Assembly of a Zinc Bacteriochlorophyll-d Analog with a Lipophilic Tertiary Amide Group in the 17-Substituent}, volume = 95, year = 2022 }

  %0 Journal Article %1 Shoji_2022 %A Shoji, Sunao %A Stepanenko, Vladimir %A Würthner, Frank %A Tamiaki, Hitoshi %D 2022 %I The Chemical Society of Japan %J Bull. Chem. Soc. Jpn. %N 7 %P 1083--1085 %R 10.1246/bcsj.20220128 %T Self-Assembly of a Zinc Bacteriochlorophyll-d Analog with a Lipophilic Tertiary Amide Group in the 17-Substituent %U https://doi.org/10.1246%2Fbcsj.20220128 %V 95 %X Self-assembled aggregates of bacteriochlorophyll(BChl)-c/d/e pigments play key roles in major light-harvesting antenna systems of photosynthetic green bacteria. Herein, we report the self-assembly of a lipophilic zinc BChl-d model with an N,N-didodecylamide in the 17-substituent. The present model formed two types of J-aggregates, which formed under kinetic and thermodynamic controls.
• Excited states and spin–orbit coupling in chalcogen substituted perylene diimides and their radical anions. Mentzel, Paul; Holzapfel, Marco; Schmiedel, Alexander; Krummenacher, Ivo; Braunschweig, Holger; Wodyński, Artur; Kaupp, Martin; Würthner, Frank; Lambert, Christoph. In Phys. Chem. Chem. Phys., 24(42), pp. 26254–26268. 2022.
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  While spin–orbit coupling does not play a decisive role in the photophysics of unsubstituted perylene diimides (PDI), this changes dramatically when two phenylselenyl or phenyltelluryl substituents were attached to the PDI bay positions. In the series of PhO-, PhS-, PhSe-, and PhTe-substituted PDIs we observed strongly decreasing fluorescence quantum yield as a consequence of strongly increasing intersystem crossing (ISC) rate, measured by transient absorption spectroscopy with fs- and ns-time resolution as well as by broadband fluorescence upconversion. Time-dependent density functional calculations suggest increasing spin–orbit coupling due to the internal heavy-atom effect as the reason for fast ISC. In case of the selenium PDI derivative we found significant singlet oxygen sensitization via the PDI triplet state. The corresponding radical anions of the chalcogen substituted PDIs were also prepared and investigated by optical and EPR spectroscopy. Here, the increasing SOC results in an increase of the g-tensor anisotropy, and of the isotropic g-value in solution, albeit quasirelativistic density functional calculations show only a relatively small fraction of the spin density to be located on the chalcogen atom.

  @article{D2CP02723B, abstract = {While spin–orbit coupling does not play a decisive role in the photophysics of unsubstituted perylene diimides (PDI), this changes dramatically when two phenylselenyl or phenyltelluryl substituents were attached to the PDI bay positions. In the series of PhO-, PhS-, PhSe-, and PhTe-substituted PDIs we observed strongly decreasing fluorescence quantum yield as a consequence of strongly increasing intersystem crossing (ISC) rate, measured by transient absorption spectroscopy with fs- and ns-time resolution as well as by broadband fluorescence upconversion. Time-dependent density functional calculations suggest increasing spin–orbit coupling due to the internal heavy-atom effect as the reason for fast ISC. In case of the selenium PDI derivative we found significant singlet oxygen sensitization via the PDI triplet state. The corresponding radical anions of the chalcogen substituted PDIs were also prepared and investigated by optical and EPR spectroscopy. Here, the increasing SOC results in an increase of the g-tensor anisotropy, and of the isotropic g-value in solution, albeit quasirelativistic density functional calculations show only a relatively small fraction of the spin density to be located on the chalcogen atom.}, author = {Mentzel, Paul and Holzapfel, Marco and Schmiedel, Alexander and Krummenacher, Ivo and Braunschweig, Holger and Wodyński, Artur and Kaupp, Martin and Würthner, Frank and Lambert, Christoph}, journal = {Phys. Chem. Chem. Phys.}, keywords = {myown}, number = 42, pages = {26254-26268}, publisher = {The Royal Society of Chemistry}, title = {Excited states and spin–orbit coupling in chalcogen substituted perylene diimides and their radical anions}, volume = 24, year = 2022 }

  %0 Journal Article %1 D2CP02723B %A Mentzel, Paul %A Holzapfel, Marco %A Schmiedel, Alexander %A Krummenacher, Ivo %A Braunschweig, Holger %A Wodyński, Artur %A Kaupp, Martin %A Würthner, Frank %A Lambert, Christoph %D 2022 %I The Royal Society of Chemistry %J Phys. Chem. Chem. Phys. %N 42 %P 26254-26268 %R 10.1039/D2CP02723B %T Excited states and spin–orbit coupling in chalcogen substituted perylene diimides and their radical anions %U http://dx.doi.org/10.1039/D2CP02723B %V 24 %X While spin–orbit coupling does not play a decisive role in the photophysics of unsubstituted perylene diimides (PDI), this changes dramatically when two phenylselenyl or phenyltelluryl substituents were attached to the PDI bay positions. In the series of PhO-, PhS-, PhSe-, and PhTe-substituted PDIs we observed strongly decreasing fluorescence quantum yield as a consequence of strongly increasing intersystem crossing (ISC) rate, measured by transient absorption spectroscopy with fs- and ns-time resolution as well as by broadband fluorescence upconversion. Time-dependent density functional calculations suggest increasing spin–orbit coupling due to the internal heavy-atom effect as the reason for fast ISC. In case of the selenium PDI derivative we found significant singlet oxygen sensitization via the PDI triplet state. The corresponding radical anions of the chalcogen substituted PDIs were also prepared and investigated by optical and EPR spectroscopy. Here, the increasing SOC results in an increase of the g-tensor anisotropy, and of the isotropic g-value in solution, albeit quasirelativistic density functional calculations show only a relatively small fraction of the spin density to be located on the chalcogen atom.
• Intramolecular Energy and Solvent-Dependent Chirality Transfer within a BINOL-Perylene Hetero-Cyclophane. Ouyang, Guanghui; Rühe, Jessica; Zhang, Yang; Lin, Mei-Jin; Liu, Minghua; Würthner, Frank. In Angew. Chem. Int. Ed., 61(31). 2022.
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  Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay-substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well-defined geometry, we report a chiral PBI hetero-cyclophane (BBI-PBI) that shows intramolecular energy and solvent-regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80–98 %) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI.

  @article{Ouyang_2022, abstract = {Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay-substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well-defined geometry, we report a chiral PBI hetero-cyclophane (BBI-PBI) that shows intramolecular energy and solvent-regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80–98 %) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI.}, author = {Ouyang, Guanghui and Rühe, Jessica and Zhang, Yang and Lin, Mei-Jin and Liu, Minghua and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {06}, number = 31, publisher = {Wiley}, title = {Intramolecular Energy and Solvent-Dependent Chirality Transfer within a BINOL-Perylene Hetero-Cyclophane}, volume = 61, year = 2022 }

  %0 Journal Article %1 Ouyang_2022 %A Ouyang, Guanghui %A Rühe, Jessica %A Zhang, Yang %A Lin, Mei-Jin %A Liu, Minghua %A Würthner, Frank %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %N 31 %R 10.1002/anie.202206706 %T Intramolecular Energy and Solvent-Dependent Chirality Transfer within a BINOL-Perylene Hetero-Cyclophane %U https://doi.org/10.1002%2Fanie.202206706 %V 61 %X Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay-substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well-defined geometry, we report a chiral PBI hetero-cyclophane (BBI-PBI) that shows intramolecular energy and solvent-regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80–98 %) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI.
• Activating Organic Phosphorescence via Heavy Metal-π Interaction Induced Intersystem Crossing. Sun, Meng-Jia; Anhalt, Olga; Sárosi, Menyhárt B.; Stolte, Matthias; Würthner, Frank. In Adv. Mater., 34(51), p. 2207331. 2022.
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  Heavy-atom-containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface-bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid-state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)2) as a triplet sensitizer and electron-deficient 1,4,5,8-naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room-temperature phosphorescence confined in the low-lying, long-lived triplet state of NDIs with photoluminescence (PL) quantum yield (ΦPL) exceeding 25% and a phosphorescence lifetime (τPh) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin–orbital coupling between the constituents.

  @article{Sun_2022, abstract = {Heavy-atom-containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface-bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid-state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)2) as a triplet sensitizer and electron-deficient 1,4,5,8-naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room-temperature phosphorescence confined in the low-lying, long-lived triplet state of NDIs with photoluminescence (PL) quantum yield (ΦPL) exceeding 25% and a phosphorescence lifetime (τPh) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin–orbital coupling between the constituents.}, author = {Sun, Meng-Jia and Anhalt, Olga and Sárosi, Menyhárt B. and Stolte, Matthias and Würthner, Frank}, journal = {Adv. Mater.}, keywords = {myown}, month = 11, number = 51, pages = 2207331, publisher = {Wiley}, title = {Activating Organic Phosphorescence via Heavy Metal-π Interaction Induced Intersystem Crossing}, volume = 34, year = 2022 }

  %0 Journal Article %1 Sun_2022 %A Sun, Meng-Jia %A Anhalt, Olga %A Sárosi, Menyhárt B. %A Stolte, Matthias %A Würthner, Frank %D 2022 %I Wiley %J Adv. Mater. %N 51 %P 2207331 %R 10.1002/adma.202207331 %T Activating Organic Phosphorescence via Heavy Metal-π Interaction Induced Intersystem Crossing %U https://doi.org/10.1002%2Fadma.202207331 %V 34 %X Heavy-atom-containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface-bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid-state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)2) as a triplet sensitizer and electron-deficient 1,4,5,8-naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room-temperature phosphorescence confined in the low-lying, long-lived triplet state of NDIs with photoluminescence (PL) quantum yield (ΦPL) exceeding 25% and a phosphorescence lifetime (τPh) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin–orbital coupling between the constituents.
• Axially chiral bay-tetraarylated perylene bisimide dyes as non-fullerene acceptors in organic solar cells. Mahlmeister, Bernhard; Renner, Rebecca; Anhalt, Olga; Stolte, Matthias; Würthner, Frank. In J. Mater. Chem. C, 10(7), pp. 2581–2591. 2022.
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  A series of twisted perylene bisimide (PBI) dyes bearing different imide substituents as well as various aryl substituents in 1,6,7,12 bay positions inducing conformationally stable axial chirality are investigated as non-fullerene acceptors (NFAs) in organic solar cells (OSCs). In a comprehensive study, both imide and aryl substituent variations are tested within a simple inverted bulk heterojunction (BHJ) architecture with donor polymer PCE-10. The results are rationalized by single crystal structure analyses revealing the importance of the sterical demand imparted by the substituents in both positions on the packing arrangements. Comparative studies of racemic and enantiopure samples of these axially chiral dyes showed that the OSC performance is only affected by the enantiopurity if the chromophore is not well shielded. In that case, intimate π–π-stacking is disfavored for enantiopure compounds, thereby improving the OSC efficiency significantly by up to 24%. For a more shielded PBI bearing bulky 2,6-diisopropylphenyl (Dipp) substituents at imide and 2-naphthyl at bay positions, a maximum power conversion efficiency (PCEmax) of 4.3% is achieved even for the racemate.

  @article{D1TC04116A, abstract = {A series of twisted perylene bisimide (PBI) dyes bearing different imide substituents as well as various aryl substituents in 1{,}6{,}7{,}12 bay positions inducing conformationally stable axial chirality are investigated as non-fullerene acceptors (NFAs) in organic solar cells (OSCs). In a comprehensive study{,} both imide and aryl substituent variations are tested within a simple inverted bulk heterojunction (BHJ) architecture with donor polymer PCE-10. The results are rationalized by single crystal structure analyses revealing the importance of the sterical demand imparted by the substituents in both positions on the packing arrangements. Comparative studies of racemic and enantiopure samples of these axially chiral dyes showed that the OSC performance is only affected by the enantiopurity if the chromophore is not well shielded. In that case{,} intimate π–π-stacking is disfavored for enantiopure compounds{,} thereby improving the OSC efficiency significantly by up to 24%. For a more shielded PBI bearing bulky 2{,}6-diisopropylphenyl (Dipp) substituents at imide and 2-naphthyl at bay positions{,} a maximum power conversion efficiency (PCEmax) of 4.3% is achieved even for the racemate.}, author = {Mahlmeister, Bernhard and Renner, Rebecca and Anhalt, Olga and Stolte, Matthias and Würthner, Frank}, journal = {J. Mater. Chem. C}, keywords = {myown}, number = 7, pages = {2581-2591}, publisher = {The Royal Society of Chemistry}, title = {Axially chiral bay-tetraarylated perylene bisimide dyes as non-fullerene acceptors in organic solar cells}, volume = 10, year = 2022 }

  %0 Journal Article %1 D1TC04116A %A Mahlmeister, Bernhard %A Renner, Rebecca %A Anhalt, Olga %A Stolte, Matthias %A Würthner, Frank %D 2022 %I The Royal Society of Chemistry %J J. Mater. Chem. C %N 7 %P 2581-2591 %R 10.1039/D1TC04116A %T Axially chiral bay-tetraarylated perylene bisimide dyes as non-fullerene acceptors in organic solar cells %U http://dx.doi.org/10.1039/D1TC04116A %V 10 %X A series of twisted perylene bisimide (PBI) dyes bearing different imide substituents as well as various aryl substituents in 1,6,7,12 bay positions inducing conformationally stable axial chirality are investigated as non-fullerene acceptors (NFAs) in organic solar cells (OSCs). In a comprehensive study, both imide and aryl substituent variations are tested within a simple inverted bulk heterojunction (BHJ) architecture with donor polymer PCE-10. The results are rationalized by single crystal structure analyses revealing the importance of the sterical demand imparted by the substituents in both positions on the packing arrangements. Comparative studies of racemic and enantiopure samples of these axially chiral dyes showed that the OSC performance is only affected by the enantiopurity if the chromophore is not well shielded. In that case, intimate π–π-stacking is disfavored for enantiopure compounds, thereby improving the OSC efficiency significantly by up to 24%. For a more shielded PBI bearing bulky 2,6-diisopropylphenyl (Dipp) substituents at imide and 2-naphthyl at bay positions, a maximum power conversion efficiency (PCEmax) of 4.3% is achieved even for the racemate.
• Peptide Backbone Directed Self-Assembly of Merocyanine Oligomers into Duplex Structures. Liu, Bin; Vonhausen, Yvonne; Schulz, Alexander; Höbartner, Claudia; Würthner, Frank. In Angew. Chem. Int. Ed., 61(21). 2022.
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  The pseudopeptide backbone provided by N-(2-aminoethyl)-glycine oligomers with attached nucleobases has been widely utilized in peptide nucleic acids (PNAs) as DNA mimics. Here we demonstrate the suitability of this backbone for the formation of structurally defined dye stacks. Toward this goal a series of peptide merocyanine (PMC) dye oligomers connected to a N-(2-aminoethyl)-glycine backbone were prepared through peptide synthesis. Our concentration-, temperature- and solvent-dependent UV/Vis absorption studies show that under the control of dipole–dipole interactions, smaller-sized oligomers consisting of one, two or three dyes self-assemble into defined duplex structures containing two up to six chromophores. In contrast, upon further extension of the oligomer, the chosen peptide backbone cannot direct the formation of a defined duplex architecture anymore due to intramolecular aggregation between the dyes. For all aggregate species a moderate aggregation-induced emission enhancement is observed.

  @article{Liu_2022, abstract = {The pseudopeptide backbone provided by N-(2-aminoethyl)-glycine oligomers with attached nucleobases has been widely utilized in peptide nucleic acids (PNAs) as DNA mimics. Here we demonstrate the suitability of this backbone for the formation of structurally defined dye stacks. Toward this goal a series of peptide merocyanine (PMC) dye oligomers connected to a N-(2-aminoethyl)-glycine backbone were prepared through peptide synthesis. Our concentration-, temperature- and solvent-dependent UV/Vis absorption studies show that under the control of dipole–dipole interactions, smaller-sized oligomers consisting of one, two or three dyes self-assemble into defined duplex structures containing two up to six chromophores. In contrast, upon further extension of the oligomer, the chosen peptide backbone cannot direct the formation of a defined duplex architecture anymore due to intramolecular aggregation between the dyes. For all aggregate species a moderate aggregation-induced emission enhancement is observed.}, author = {Liu, Bin and Vonhausen, Yvonne and Schulz, Alexander and Höbartner, Claudia and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {03}, number = 21, publisher = {Wiley}, title = {Peptide Backbone Directed Self-Assembly of Merocyanine Oligomers into Duplex Structures}, volume = 61, year = 2022 }

  %0 Journal Article %1 Liu_2022 %A Liu, Bin %A Vonhausen, Yvonne %A Schulz, Alexander %A Höbartner, Claudia %A Würthner, Frank %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %N 21 %R 10.1002/anie.202200120 %T Peptide Backbone Directed Self-Assembly of Merocyanine Oligomers into Duplex Structures %U https://doi.org/10.1002%2Fanie.202200120 %V 61 %X The pseudopeptide backbone provided by N-(2-aminoethyl)-glycine oligomers with attached nucleobases has been widely utilized in peptide nucleic acids (PNAs) as DNA mimics. Here we demonstrate the suitability of this backbone for the formation of structurally defined dye stacks. Toward this goal a series of peptide merocyanine (PMC) dye oligomers connected to a N-(2-aminoethyl)-glycine backbone were prepared through peptide synthesis. Our concentration-, temperature- and solvent-dependent UV/Vis absorption studies show that under the control of dipole–dipole interactions, smaller-sized oligomers consisting of one, two or three dyes self-assemble into defined duplex structures containing two up to six chromophores. In contrast, upon further extension of the oligomer, the chosen peptide backbone cannot direct the formation of a defined duplex architecture anymore due to intramolecular aggregation between the dyes. For all aggregate species a moderate aggregation-induced emission enhancement is observed.
• Phenol-Functionalized Perylene Bisimides as Amine-Free Electron Transporting Interlayers for Stable Nonfullerene Organic Solar Cells. Wen, Xinbo; Zhang, Yu; Xie, Guojing; Rausch, Rodger; Tang, Ningning; Zheng, Nan; Liu, Linlin; Würthner, Frank; Xie, Zengqi. In Adv. Funct. Mater., 32(17), p. 2111706. 2022.
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  A new type of cathode interlayer composed of 2,6-di-tert-butyl-phenol-functionalized perylene bisimide (PBI-2P) is successfully applied as an electron transporting layer for fused-ring nonfullerene organic solar cells (OSCs). The stable contact between these novel electron transporting layers and the representative nonfullerene acceptor Y6 greatly enhances the device stability compared to conventional amine-group containing cathode interlayers. Moreover, the easily formed biradical species in the interlayers yields rather good thickness tolerance of the PBI-2P layer in photovoltaic devices. The OSCs based on the PBI-2P interlayer show a power conversion efficiency up to 17.20% and good stability compared to amino-group functionalized interlayers. The findings demonstrate a promising design principle for cathode interlayer engineering based on pigment chromophores equipped with the 2,6-di-tert-butylphenoxy groups that are prone to form the respective ultrastable butylphenoxy radicals for stable nonfullerene OSCs.

  @article{Wen_2022, abstract = {A new type of cathode interlayer composed of 2,6-di-tert-butyl-phenol-functionalized perylene bisimide (PBI-2P) is successfully applied as an electron transporting layer for fused-ring nonfullerene organic solar cells (OSCs). The stable contact between these novel electron transporting layers and the representative nonfullerene acceptor Y6 greatly enhances the device stability compared to conventional amine-group containing cathode interlayers. Moreover, the easily formed biradical species in the interlayers yields rather good thickness tolerance of the PBI-2P layer in photovoltaic devices. The OSCs based on the PBI-2P interlayer show a power conversion efficiency up to 17.20% and good stability compared to amino-group functionalized interlayers. The findings demonstrate a promising design principle for cathode interlayer engineering based on pigment chromophores equipped with the 2,6-di-tert-butylphenoxy groups that are prone to form the respective ultrastable butylphenoxy radicals for stable nonfullerene OSCs.}, author = {Wen, Xinbo and Zhang, Yu and Xie, Guojing and Rausch, Rodger and Tang, Ningning and Zheng, Nan and Liu, Linlin and Würthner, Frank and Xie, Zengqi}, journal = {Adv. Funct. Mater.}, keywords = {myown}, month = {01}, number = 17, pages = 2111706, publisher = {Wiley}, title = {Phenol-Functionalized Perylene Bisimides as Amine-Free Electron Transporting Interlayers for Stable Nonfullerene Organic Solar Cells}, volume = 32, year = 2022 }

  %0 Journal Article %1 Wen_2022 %A Wen, Xinbo %A Zhang, Yu %A Xie, Guojing %A Rausch, Rodger %A Tang, Ningning %A Zheng, Nan %A Liu, Linlin %A Würthner, Frank %A Xie, Zengqi %D 2022 %I Wiley %J Adv. Funct. Mater. %N 17 %P 2111706 %R 10.1002/adfm.202111706 %T Phenol-Functionalized Perylene Bisimides as Amine-Free Electron Transporting Interlayers for Stable Nonfullerene Organic Solar Cells %U https://doi.org/10.1002%2Fadfm.202111706 %V 32 %X A new type of cathode interlayer composed of 2,6-di-tert-butyl-phenol-functionalized perylene bisimide (PBI-2P) is successfully applied as an electron transporting layer for fused-ring nonfullerene organic solar cells (OSCs). The stable contact between these novel electron transporting layers and the representative nonfullerene acceptor Y6 greatly enhances the device stability compared to conventional amine-group containing cathode interlayers. Moreover, the easily formed biradical species in the interlayers yields rather good thickness tolerance of the PBI-2P layer in photovoltaic devices. The OSCs based on the PBI-2P interlayer show a power conversion efficiency up to 17.20% and good stability compared to amino-group functionalized interlayers. The findings demonstrate a promising design principle for cathode interlayer engineering based on pigment chromophores equipped with the 2,6-di-tert-butylphenoxy groups that are prone to form the respective ultrastable butylphenoxy radicals for stable nonfullerene OSCs.
• Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides. Mahlmeister, Bernhard; Mahl, Magnus; Reichelt, Helmut; Shoyama, Kazutaka; Stolte, Matthias; Würthner, Frank. In J. Am. Chem. Soc., 144(23), pp. 10507–10514. 2022.
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  Graphene nanoribbons (GNRs) have the potential for next-generation functional devices. So far, GNRs with defined stereochemistry are rarely reported in literature and their optical response is usually bound to the ultraviolet or visible spectral region, while covering the near-infrared (NIR) regime is still challenging. Herein, we report two novel quaterrylene bisimides with either one- or twofold-twisted π-backbones enabled by the steric congestion of a fourfold bay arylation leading to an end-to-end twist of up to 76°. The strong interlocking effect of the π-stacked aryl substituents introduces a rigidification of the chromophore unambiguously proven by single-crystal X-ray analysis. This leads to unexpectedly strong NIR emissions at 862 and 903 nm with quantum yields of 1.5 and 0.9%, respectively, further ensuring high solubility as well as resolvable and highly stable atropo-enantiomers. Circular dichroism spectroscopy of these enantiopure chiral compounds reveals a strong Cotton effect Δε of up to 67 M–1 cm–1 centered far in the NIR region at 849 nm.

  @article{Mahlmeister_2022, abstract = {Graphene nanoribbons (GNRs) have the potential for next-generation functional devices. So far, GNRs with defined stereochemistry are rarely reported in literature and their optical response is usually bound to the ultraviolet or visible spectral region, while covering the near-infrared (NIR) regime is still challenging. Herein, we report two novel quaterrylene bisimides with either one- or twofold-twisted π-backbones enabled by the steric congestion of a fourfold bay arylation leading to an end-to-end twist of up to 76°. The strong interlocking effect of the π-stacked aryl substituents introduces a rigidification of the chromophore unambiguously proven by single-crystal X-ray analysis. This leads to unexpectedly strong NIR emissions at 862 and 903 nm with quantum yields of 1.5 and 0.9%, respectively, further ensuring high solubility as well as resolvable and highly stable atropo-enantiomers. Circular dichroism spectroscopy of these enantiopure chiral compounds reveals a strong Cotton effect Δε of up to 67 M–1 cm–1 centered far in the NIR region at 849 nm.}, author = {Mahlmeister, Bernhard and Mahl, Magnus and Reichelt, Helmut and Shoyama, Kazutaka and Stolte, Matthias and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {06}, number = 23, pages = {10507–10514}, publisher = {American Chemical Society (ACS)}, title = {Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides}, volume = 144, year = 2022 }

  %0 Journal Article %1 Mahlmeister_2022 %A Mahlmeister, Bernhard %A Mahl, Magnus %A Reichelt, Helmut %A Shoyama, Kazutaka %A Stolte, Matthias %A Würthner, Frank %D 2022 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 23 %P 10507--10514 %R 10.1021/jacs.2c02947 %T Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides %U https://doi.org/10.1021%2Fjacs.2c02947 %V 144 %X Graphene nanoribbons (GNRs) have the potential for next-generation functional devices. So far, GNRs with defined stereochemistry are rarely reported in literature and their optical response is usually bound to the ultraviolet or visible spectral region, while covering the near-infrared (NIR) regime is still challenging. Herein, we report two novel quaterrylene bisimides with either one- or twofold-twisted π-backbones enabled by the steric congestion of a fourfold bay arylation leading to an end-to-end twist of up to 76°. The strong interlocking effect of the π-stacked aryl substituents introduces a rigidification of the chromophore unambiguously proven by single-crystal X-ray analysis. This leads to unexpectedly strong NIR emissions at 862 and 903 nm with quantum yields of 1.5 and 0.9%, respectively, further ensuring high solubility as well as resolvable and highly stable atropo-enantiomers. Circular dichroism spectroscopy of these enantiopure chiral compounds reveals a strong Cotton effect Δε of up to 67 M–1 cm–1 centered far in the NIR region at 849 nm.
• Supramolecularly Engineered Bulk-Heterojunction Solar Cells with Self-Assembled Non-Fullerene Nanographene Tetraimide Acceptors. Menekse, Kaan; Mahl, Magnus; Albert, Julius; Niyas, M. A.; Shoyama, Kazutaka; Stolte, Matthias; Würthner, Frank. In Solar RRL, 7(2), p. 2200895. 2022.
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  A series of novel imide-functionalized C64 nanographenes is investigated as acceptor components in organic solar cells (OSCs) in combination with donor polymer PM6. These electron-poor molecules either prevail as a monomer or self-assemble into dimers in the OSC active layer depending on the chosen imide substituents. This allows for the controlled stacking of electron-poor and electron-rich π–scaffolds to establish a novel class of non-fullerene acceptor materials to tailor the bulk-heterojunction morphology of the OSCs. The best performance is observed for derivatives that are able to self-assemble into dimers, reaching power conversion efficiencies of up to 7.1%.

  @article{Menekse_2022, abstract = {A series of novel imide-functionalized C64 nanographenes is investigated as acceptor components in organic solar cells (OSCs) in combination with donor polymer PM6. These electron-poor molecules either prevail as a monomer or self-assemble into dimers in the OSC active layer depending on the chosen imide substituents. This allows for the controlled stacking of electron-poor and electron-rich π–scaffolds to establish a novel class of non-fullerene acceptor materials to tailor the bulk-heterojunction morphology of the OSCs. The best performance is observed for derivatives that are able to self-assemble into dimers, reaching power conversion efficiencies of up to 7.1%.}, author = {Menekse, Kaan and Mahl, Magnus and Albert, Julius and Niyas, M. A. and Shoyama, Kazutaka and Stolte, Matthias and Würthner, Frank}, journal = {Solar RRL}, keywords = {myown}, month = 12, number = 2, pages = 2200895, publisher = {Wiley}, title = {Supramolecularly Engineered Bulk-Heterojunction Solar Cells with Self-Assembled Non-Fullerene Nanographene Tetraimide Acceptors}, volume = 7, year = 2022 }

  %0 Journal Article %1 Menekse_2022 %A Menekse, Kaan %A Mahl, Magnus %A Albert, Julius %A Niyas, M. A. %A Shoyama, Kazutaka %A Stolte, Matthias %A Würthner, Frank %D 2022 %I Wiley %J Solar RRL %N 2 %P 2200895 %R 10.1002/solr.202200895 %T Supramolecularly Engineered Bulk-Heterojunction Solar Cells with Self-Assembled Non-Fullerene Nanographene Tetraimide Acceptors %U https://doi.org/10.1002%2Fsolr.202200895 %V 7 %X A series of novel imide-functionalized C64 nanographenes is investigated as acceptor components in organic solar cells (OSCs) in combination with donor polymer PM6. These electron-poor molecules either prevail as a monomer or self-assemble into dimers in the OSC active layer depending on the chosen imide substituents. This allows for the controlled stacking of electron-poor and electron-rich π–scaffolds to establish a novel class of non-fullerene acceptor materials to tailor the bulk-heterojunction morphology of the OSCs. The best performance is observed for derivatives that are able to self-assemble into dimers, reaching power conversion efficiencies of up to 7.1%.
• Energy transfer in supramolecular calix[4]arene-Perylene bisimide dye light harvesting building blocks: Resolving loss processes with simultaneous target analysis. van Stokkum, Ivo H.M.; Wohlmuth, Catharina; Würthner, Frank; Williams, René M. In Journal of Photochemistry and Photobiology, 12, p. 100154. 2022.
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  By the application of simultaneous target analysis of multiple femtosecond transient absorption data sets we have identified two loss channels within multi-chromophoric light harvesting arrays. Perylene bisimide-calix[4]arene arrays composed of up to three different types of perylene bisimide (PBI) chromophores, orange (o), red (r), and green (g) PBIs (named after their colors as solids), have previously been studied by transient absorption spectroscopy (Hippius et al., J. Phys. Chem C 112:2476, 2008) and here we present a simultaneous target analysis of those data matrices. A covalent system containing the red chromophore (r) and calix[4]arene (c), the rc system, shows extensive spectral evolution that can be described with four excited states (r1*→r2*→r3*→r4*→ground state). In the Perylene Orange calix[4]arene system (oc), a radical pair (ocRP) can be formed by photoinduced electron transfer (Hippius et al., J. Phys. Chem C 111:13988, 2007). In a simultaneous target analysis of the multichromophoric systems ocr, rcocr and ocrco the properties of rc and oc are integrated, and excitation energy transfer (EET) from o* to r* occurs. In addition, we demonstrate that the final Species Associated Difference Spectrum (SADS) also contains o bleach features that indicate an excitonic interaction, for ocr, rcocr and ocrco. In a simultaneous target analysis of rcg and gcrcg the properties of rc are integrated, and next to EET to g* we can resolve the formation of a new rcgRP that is formed from r1* or r2*, and represents a loss of 7 and 12%, respectively. In a simultaneous target analysis of ocrcg the properties of ocr and rcg are integrated, arriving at a consistent picture with an energy transfer quantum yield of formation of the excited state of the green PBI (g*) of 80%.

  @article{van_Stokkum_2022, abstract = {By the application of simultaneous target analysis of multiple femtosecond transient absorption data sets we have identified two loss channels within multi-chromophoric light harvesting arrays. Perylene bisimide-calix[4]arene arrays composed of up to three different types of perylene bisimide (PBI) chromophores, orange (o), red (r), and green (g) PBIs (named after their colors as solids), have previously been studied by transient absorption spectroscopy (Hippius et al., J. Phys. Chem C 112:2476, 2008) and here we present a simultaneous target analysis of those data matrices. A covalent system containing the red chromophore (r) and calix[4]arene (c), the rc system, shows extensive spectral evolution that can be described with four excited states (r1*→r2*→r3*→r4*→ground state). In the Perylene Orange calix[4]arene system (oc), a radical pair (ocRP) can be formed by photoinduced electron transfer (Hippius et al., J. Phys. Chem C 111:13988, 2007). In a simultaneous target analysis of the multichromophoric systems ocr, rcocr and ocrco the properties of rc and oc are integrated, and excitation energy transfer (EET) from o* to r* occurs. In addition, we demonstrate that the final Species Associated Difference Spectrum (SADS) also contains o bleach features that indicate an excitonic interaction, for ocr, rcocr and ocrco. In a simultaneous target analysis of rcg and gcrcg the properties of rc are integrated, and next to EET to g* we can resolve the formation of a new rcgRP that is formed from r1* or r2*, and represents a loss of 7 and 12%, respectively. In a simultaneous target analysis of ocrcg the properties of ocr and rcg are integrated, arriving at a consistent picture with an energy transfer quantum yield of formation of the excited state of the green PBI (g*) of 80%.}, author = {van Stokkum, Ivo H.M. and Wohlmuth, Catharina and Würthner, Frank and Williams, René M.}, journal = {Journal of Photochemistry and Photobiology}, keywords = {myown}, month = 12, pages = 100154, publisher = {Elsevier}, title = {Energy transfer in supramolecular calix[4]arene-Perylene bisimide dye light harvesting building blocks: Resolving loss processes with simultaneous target analysis}, volume = 12, year = 2022 }

  %0 Journal Article %1 van_Stokkum_2022 %A van Stokkum, Ivo H.M. %A Wohlmuth, Catharina %A Würthner, Frank %A Williams, René M. %D 2022 %I Elsevier %J Journal of Photochemistry and Photobiology %P 100154 %R 10.1016/j.jpap.2022.100154 %T Energy transfer in supramolecular calix[4]arene-Perylene bisimide dye light harvesting building blocks: Resolving loss processes with simultaneous target analysis %U https://doi.org/10.1016%2Fj.jpap.2022.100154 %V 12 %X By the application of simultaneous target analysis of multiple femtosecond transient absorption data sets we have identified two loss channels within multi-chromophoric light harvesting arrays. Perylene bisimide-calix[4]arene arrays composed of up to three different types of perylene bisimide (PBI) chromophores, orange (o), red (r), and green (g) PBIs (named after their colors as solids), have previously been studied by transient absorption spectroscopy (Hippius et al., J. Phys. Chem C 112:2476, 2008) and here we present a simultaneous target analysis of those data matrices. A covalent system containing the red chromophore (r) and calix[4]arene (c), the rc system, shows extensive spectral evolution that can be described with four excited states (r1*→r2*→r3*→r4*→ground state). In the Perylene Orange calix[4]arene system (oc), a radical pair (ocRP) can be formed by photoinduced electron transfer (Hippius et al., J. Phys. Chem C 111:13988, 2007). In a simultaneous target analysis of the multichromophoric systems ocr, rcocr and ocrco the properties of rc and oc are integrated, and excitation energy transfer (EET) from o* to r* occurs. In addition, we demonstrate that the final Species Associated Difference Spectrum (SADS) also contains o bleach features that indicate an excitonic interaction, for ocr, rcocr and ocrco. In a simultaneous target analysis of rcg and gcrcg the properties of rc are integrated, and next to EET to g* we can resolve the formation of a new rcgRP that is formed from r1* or r2*, and represents a loss of 7 and 12%, respectively. In a simultaneous target analysis of ocrcg the properties of ocr and rcg are integrated, arriving at a consistent picture with an energy transfer quantum yield of formation of the excited state of the green PBI (g*) of 80%.
• Multilayer stacks of polycyclic aromatic hydrocarbons. Mahl, Magnus; Niyas, M. A.; Shoyama, Kazutaka; Würthner, Frank. In Nature Chemistry, 14(4), pp. 457–462. 2022.
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  Polycyclic aromatic hydrocarbons (PAHs) show promise for applications in functional devices such as organic photovoltaics and field-effect transistors, but, although nanometre-sized PAHs—often referred to as nanographenes—have been well inves- tigated as single-layer molecules, their multilayer counterparts remain rather unexplored. Here we show the assembly of a C64 nanographene derivative (comprising a planar core decorated with four meta-terphenyl–imide moieties at its periphery) into multilayer stacks with smaller PAHs ranging from naphthalene to ovalene and hexabenzocoronene. The functionalized C64 nanographene serves as a ditopic host that can accommodate a smaller PAH on either side of its planar core, in cavities delim- ited by its bulky imide substituents. Bilayers and trilayers (that is, complexes with 1:1 and 1:2 host:guest ratios, respectively) were observed in solution, and dimers of these complexes as well as multilayer compounds were isolated in the solid state. Quantum-chemical calculations indicate that dispersion forces are the main stabilizing factor for these complexes.

  @article{Mahl_2022, abstract = {Polycyclic aromatic hydrocarbons (PAHs) show promise for applications in functional devices such as organic photovoltaics and field-effect transistors, but, although nanometre-sized PAHs—often referred to as nanographenes—have been well inves- tigated as single-layer molecules, their multilayer counterparts remain rather unexplored. Here we show the assembly of a C64 nanographene derivative (comprising a planar core decorated with four meta-terphenyl–imide moieties at its periphery) into multilayer stacks with smaller PAHs ranging from naphthalene to ovalene and hexabenzocoronene. The functionalized C64 nanographene serves as a ditopic host that can accommodate a smaller PAH on either side of its planar core, in cavities delim- ited by its bulky imide substituents. Bilayers and trilayers (that is, complexes with 1:1 and 1:2 host:guest ratios, respectively) were observed in solution, and dimers of these complexes as well as multilayer compounds were isolated in the solid state. Quantum-chemical calculations indicate that dispersion forces are the main stabilizing factor for these complexes.}, author = {Mahl, Magnus and Niyas, M. A. and Shoyama, Kazutaka and Würthner, Frank}, journal = {Nature Chemistry}, keywords = {myown}, month = {02}, number = 4, pages = {457–462}, publisher = {Springer Science and Business Media {LLC}}, title = {Multilayer stacks of polycyclic aromatic hydrocarbons}, volume = 14, year = 2022 }

  %0 Journal Article %1 Mahl_2022 %A Mahl, Magnus %A Niyas, M. A. %A Shoyama, Kazutaka %A Würthner, Frank %D 2022 %I Springer Science and Business Media LLC %J Nature Chemistry %N 4 %P 457--462 %R 10.1038/s41557-021-00861-5 %T Multilayer stacks of polycyclic aromatic hydrocarbons %U https://doi.org/10.1038%2Fs41557-021-00861-5 %V 14 %X Polycyclic aromatic hydrocarbons (PAHs) show promise for applications in functional devices such as organic photovoltaics and field-effect transistors, but, although nanometre-sized PAHs—often referred to as nanographenes—have been well inves- tigated as single-layer molecules, their multilayer counterparts remain rather unexplored. Here we show the assembly of a C64 nanographene derivative (comprising a planar core decorated with four meta-terphenyl–imide moieties at its periphery) into multilayer stacks with smaller PAHs ranging from naphthalene to ovalene and hexabenzocoronene. The functionalized C64 nanographene serves as a ditopic host that can accommodate a smaller PAH on either side of its planar core, in cavities delim- ited by its bulky imide substituents. Bilayers and trilayers (that is, complexes with 1:1 and 1:2 host:guest ratios, respectively) were observed in solution, and dimers of these complexes as well as multilayer compounds were isolated in the solid state. Quantum-chemical calculations indicate that dispersion forces are the main stabilizing factor for these complexes.
• Photon-Correlation Studies on Multichromophore Macrocycles of Perylene Dyes. Müller, Ulrich; Spenst, Peter; Kagerer, Philipp; Stolte, Matthias; Würthner, Frank; Pflaum, Jens. In Adv. Opt. Mater., 10(14), p. 2200234. 2022.
  • [ Abstract ]
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  Organic dyes offer unique properties for their application as room temperature single photon emitters. By means of photon-correlation, the emission characteristics of macrocyclic para-xylylene linked perylene bisimide (PBI) trimers and tetramers dispersed in polymethyl methacrylate matrices are analyzed. The optical data indicate that, despite of the strong emission enhancement of PBI trimers and tetramers according to their larger number of chromophores, the photon-correlation statistics still obeys that of single photon emitters. Moreover, driving PBI trimers and tetramers at higher excitation powers, saturated emission behavior for monomers is found while macrocycle emission is still far-off saturation but shows enhanced fluctuations. This observation is attributed to fast singlet–singlet annihilation, i.e., faster than the radiative lifetime of the excited S1 state, and the enlarged number of conformational arrangements of multichromophores in the polymeric host. Finally, embedding trimeric PBI macrocycles in active organic light-emitting diode matrices, electrically driven bright fluorescence together with an indication for antibunching at room temperature can be detected. This, so far, has only been observed for phosphorescent emitters that feature much longer lifetimes of the excited states and, thus, smaller radiative recombination rates. The results are discussed in the context of possible effects on the g(2) behavior of molecular emitters.

  @article{M_ller_2022, abstract = {Organic dyes offer unique properties for their application as room temperature single photon emitters. By means of photon-correlation, the emission characteristics of macrocyclic para-xylylene linked perylene bisimide (PBI) trimers and tetramers dispersed in polymethyl methacrylate matrices are analyzed. The optical data indicate that, despite of the strong emission enhancement of PBI trimers and tetramers according to their larger number of chromophores, the photon-correlation statistics still obeys that of single photon emitters. Moreover, driving PBI trimers and tetramers at higher excitation powers, saturated emission behavior for monomers is found while macrocycle emission is still far-off saturation but shows enhanced fluctuations. This observation is attributed to fast singlet–singlet annihilation, i.e., faster than the radiative lifetime of the excited S1 state, and the enlarged number of conformational arrangements of multichromophores in the polymeric host. Finally, embedding trimeric PBI macrocycles in active organic light-emitting diode matrices, electrically driven bright fluorescence together with an indication for antibunching at room temperature can be detected. This, so far, has only been observed for phosphorescent emitters that feature much longer lifetimes of the excited states and, thus, smaller radiative recombination rates. The results are discussed in the context of possible effects on the g(2) behavior of molecular emitters.}, author = {Müller, Ulrich and Spenst, Peter and Kagerer, Philipp and Stolte, Matthias and Würthner, Frank and Pflaum, Jens}, journal = {Adv. Opt. Mater.}, keywords = {myown}, month = {05}, number = 14, pages = 2200234, publisher = {Wiley}, title = {Photon-Correlation Studies on Multichromophore Macrocycles of Perylene Dyes}, volume = 10, year = 2022 }

  %0 Journal Article %1 M_ller_2022 %A Müller, Ulrich %A Spenst, Peter %A Kagerer, Philipp %A Stolte, Matthias %A Würthner, Frank %A Pflaum, Jens %D 2022 %I Wiley %J Adv. Opt. Mater. %N 14 %P 2200234 %R 10.1002/adom.202200234 %T Photon-Correlation Studies on Multichromophore Macrocycles of Perylene Dyes %U https://doi.org/10.1002%2Fadom.202200234 %V 10 %X Organic dyes offer unique properties for their application as room temperature single photon emitters. By means of photon-correlation, the emission characteristics of macrocyclic para-xylylene linked perylene bisimide (PBI) trimers and tetramers dispersed in polymethyl methacrylate matrices are analyzed. The optical data indicate that, despite of the strong emission enhancement of PBI trimers and tetramers according to their larger number of chromophores, the photon-correlation statistics still obeys that of single photon emitters. Moreover, driving PBI trimers and tetramers at higher excitation powers, saturated emission behavior for monomers is found while macrocycle emission is still far-off saturation but shows enhanced fluctuations. This observation is attributed to fast singlet–singlet annihilation, i.e., faster than the radiative lifetime of the excited S1 state, and the enlarged number of conformational arrangements of multichromophores in the polymeric host. Finally, embedding trimeric PBI macrocycles in active organic light-emitting diode matrices, electrically driven bright fluorescence together with an indication for antibunching at room temperature can be detected. This, so far, has only been observed for phosphorescent emitters that feature much longer lifetimes of the excited states and, thus, smaller radiative recombination rates. The results are discussed in the context of possible effects on the g(2) behavior of molecular emitters.
• Real-time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda-dimer by Ultrafast Time-Domain Raman Spectroscopy. Hong, Yongseok; Kim, Woojae; Kim, Taeyeon; Kaufmann, Christina; Kim, Hyungjun; Würthner, Frank; Kim, Dongho. In Angew. Chem. Int. Ed. 2022.
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  In π-conjugated organic photovoltaic materials, an excimer state has been generally regarded as a trap state which hinders efficient excitation energy transport. But despite wide investigations of the excimer for overcoming the undesirable energy loss, the understanding of the relationship between the structure of the excimer in stacked organic compounds and its properties remains elusive. Here, we present the landscape of structural dynamics from the excimer formation to its relaxation in a co-facially stacked archetypical perylene bisimide folda-dimer using ultrafast time-domain Raman spectroscopy. We directly captured vibrational snapshots illustrating the ultrafast structural evolution triggering the excimer formation along the interchromophore coordinate on the complex excited-state potential surfaces and following evolution into a relaxed excimer state. Not only does this work showcase the ultrafast structural dynamics necessary for the excimer formation and control of excimer characteristics but also provides important criteria for designing the π-conjugated organic molecules.

  @article{Hong_2022, abstract = {In π-conjugated organic photovoltaic materials, an excimer state has been generally regarded as a trap state which hinders efficient excitation energy transport. But despite wide investigations of the excimer for overcoming the undesirable energy loss, the understanding of the relationship between the structure of the excimer in stacked organic compounds and its properties remains elusive. Here, we present the landscape of structural dynamics from the excimer formation to its relaxation in a co-facially stacked archetypical perylene bisimide folda-dimer using ultrafast time-domain Raman spectroscopy. We directly captured vibrational snapshots illustrating the ultrafast structural evolution triggering the excimer formation along the interchromophore coordinate on the complex excited-state potential surfaces and following evolution into a relaxed excimer state. Not only does this work showcase the ultrafast structural dynamics necessary for the excimer formation and control of excimer characteristics but also provides important criteria for designing the π-conjugated organic molecules.}, author = {Hong, Yongseok and Kim, Woojae and Kim, Taeyeon and Kaufmann, Christina and Kim, Hyungjun and Würthner, Frank and Kim, Dongho}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {02}, publisher = {Wiley}, title = {Real-time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda-dimer by Ultrafast Time-Domain Raman Spectroscopy}, year = 2022 }

  %0 Journal Article %1 Hong_2022 %A Hong, Yongseok %A Kim, Woojae %A Kim, Taeyeon %A Kaufmann, Christina %A Kim, Hyungjun %A Würthner, Frank %A Kim, Dongho %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202114474 %T Real-time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda-dimer by Ultrafast Time-Domain Raman Spectroscopy %U https://doi.org/10.1002%2Fanie.202114474 %X In π-conjugated organic photovoltaic materials, an excimer state has been generally regarded as a trap state which hinders efficient excitation energy transport. But despite wide investigations of the excimer for overcoming the undesirable energy loss, the understanding of the relationship between the structure of the excimer in stacked organic compounds and its properties remains elusive. Here, we present the landscape of structural dynamics from the excimer formation to its relaxation in a co-facially stacked archetypical perylene bisimide folda-dimer using ultrafast time-domain Raman spectroscopy. We directly captured vibrational snapshots illustrating the ultrafast structural evolution triggering the excimer formation along the interchromophore coordinate on the complex excited-state potential surfaces and following evolution into a relaxed excimer state. Not only does this work showcase the ultrafast structural dynamics necessary for the excimer formation and control of excimer characteristics but also provides important criteria for designing the π-conjugated organic molecules.
• Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP). Wu, Zhu; Roldao, Juan Carlos; Rauch, Florian; Friedrich, Alexandra; Ferger, Matthias; Würthner, Frank; Gierschner, Johannes; Marder, Todd B. In Angew. Chem. Int. Ed., 61(15). 2022.
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  Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)3 does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.

  @article{Wu_2022, abstract = {Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)3 does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.}, author = {Wu, Zhu and Roldao, Juan Carlos and Rauch, Florian and Friedrich, Alexandra and Ferger, Matthias and Würthner, Frank and Gierschner, Johannes and Marder, Todd B.}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {02}, number = 15, publisher = {Wiley}, title = {Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP)}, volume = 61, year = 2022 }

  %0 Journal Article %1 Wu_2022 %A Wu, Zhu %A Roldao, Juan Carlos %A Rauch, Florian %A Friedrich, Alexandra %A Ferger, Matthias %A Würthner, Frank %A Gierschner, Johannes %A Marder, Todd B. %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %N 15 %R 10.1002/anie.202200599 %T Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP) %U https://doi.org/10.1002%2Fanie.202200599 %V 61 %X Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)3 does not luminesce in the solid state when irradiated at 250–400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.
• Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature. Wu, Zhu; Dinkelbach, Fabian; Kerner, Florian; Friedrich, Alexandra; Ji, Lei; Stepanenko, Vladimir; Würthner, Frank; Marian, Christel M.; Marder, Todd B. In Chem. Eur. J., 28(30). 2022.
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  Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T1M state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T1A state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.

  @article{Wu_2022, abstract = {Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T1M state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T1A state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.}, author = {Wu, Zhu and Dinkelbach, Fabian and Kerner, Florian and Friedrich, Alexandra and Ji, Lei and Stepanenko, Vladimir and Würthner, Frank and Marian, Christel M. and Marder, Todd B.}, journal = {Chem. Eur. J.}, keywords = {myown}, month = {04}, number = 30, publisher = {Wiley}, title = {Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature}, volume = 28, year = 2022 }

  %0 Journal Article %1 Wu_2022 %A Wu, Zhu %A Dinkelbach, Fabian %A Kerner, Florian %A Friedrich, Alexandra %A Ji, Lei %A Stepanenko, Vladimir %A Würthner, Frank %A Marian, Christel M. %A Marder, Todd B. %D 2022 %I Wiley %J Chem. Eur. J. %N 30 %R 10.1002/chem.202200525 %T Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature %U https://doi.org/10.1002%2Fchem.202200525 %V 28 %X Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T1M state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T1A state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.
• Macrocyclic Donor-Acceptor Dyads Composed of Oligothiophene Half-Cycles and Perylene Bisimides. Bold, Kevin; Stolte, Matthias; Shoyama, Kazutaka; Krause, Ana-Maria; Schmiedel, Alexander; Holzapfel, Marco; Lambert, Christoph; Würthner, Frank. In Chem. Eur. J., 28(30). 2022.
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  A series of donor-acceptor (D−A) macrocyclic dyads consisting of an electron-poor perylene bisimide (PBI) π-scaffold bridged with electron-rich α-oligothiophenes bearing four, five, six and seven thiophene units between the two phenyl-imide substituents has been synthesized and characterized by steady-state UV/Vis absorption and fluorescence spectroscopy, cyclic and differential pulse voltammetry as well as transient absorption spectroscopy. Tying the oligothiophene strands in a conformationally fixed macrocyclic arrangement leads to a more rigid π-scaffold with vibronic fine structure in the respective absorption spectra. Electrochemical analysis disclosed charged state properties in solution which are strongly dependent on the degree of rigidification within the individual macrocycle. Investigation of the excited state dynamics revealed an oligothiophene bridge size-dependent fast charge transfer process for the macrocyclic dyads upon PBI subunit excitation.

  @article{Bold_2022, abstract = {A series of donor-acceptor (D−A) macrocyclic dyads consisting of an electron-poor perylene bisimide (PBI) π-scaffold bridged with electron-rich α-oligothiophenes bearing four, five, six and seven thiophene units between the two phenyl-imide substituents has been synthesized and characterized by steady-state UV/Vis absorption and fluorescence spectroscopy, cyclic and differential pulse voltammetry as well as transient absorption spectroscopy. Tying the oligothiophene strands in a conformationally fixed macrocyclic arrangement leads to a more rigid π-scaffold with vibronic fine structure in the respective absorption spectra. Electrochemical analysis disclosed charged state properties in solution which are strongly dependent on the degree of rigidification within the individual macrocycle. Investigation of the excited state dynamics revealed an oligothiophene bridge size-dependent fast charge transfer process for the macrocyclic dyads upon PBI subunit excitation.}, author = {Bold, Kevin and Stolte, Matthias and Shoyama, Kazutaka and Krause, Ana-Maria and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Würthner, Frank}, journal = {Chem. Eur. J.}, keywords = {myown}, month = {04}, number = 30, publisher = {Wiley}, title = {Macrocyclic Donor-Acceptor Dyads Composed of Oligothiophene Half-Cycles and Perylene Bisimides}, volume = 28, year = 2022 }

  %0 Journal Article %1 Bold_2022 %A Bold, Kevin %A Stolte, Matthias %A Shoyama, Kazutaka %A Krause, Ana-Maria %A Schmiedel, Alexander %A Holzapfel, Marco %A Lambert, Christoph %A Würthner, Frank %D 2022 %I Wiley %J Chem. Eur. J. %N 30 %R 10.1002/chem.202200355 %T Macrocyclic Donor-Acceptor Dyads Composed of Oligothiophene Half-Cycles and Perylene Bisimides %U https://doi.org/10.1002%2Fchem.202200355 %V 28 %X A series of donor-acceptor (D−A) macrocyclic dyads consisting of an electron-poor perylene bisimide (PBI) π-scaffold bridged with electron-rich α-oligothiophenes bearing four, five, six and seven thiophene units between the two phenyl-imide substituents has been synthesized and characterized by steady-state UV/Vis absorption and fluorescence spectroscopy, cyclic and differential pulse voltammetry as well as transient absorption spectroscopy. Tying the oligothiophene strands in a conformationally fixed macrocyclic arrangement leads to a more rigid π-scaffold with vibronic fine structure in the respective absorption spectra. Electrochemical analysis disclosed charged state properties in solution which are strongly dependent on the degree of rigidification within the individual macrocycle. Investigation of the excited state dynamics revealed an oligothiophene bridge size-dependent fast charge transfer process for the macrocyclic dyads upon PBI subunit excitation.
• Boron-Locked Starazine - A Soluble and Fluorescent Analogue of Starphene. Feng, Yi; Zhou, Jiadong; Qiu, Honglin; Schnitzlein, Matthias; Hu, Jingtao; Liu, Linlin; Würthner, Frank; Xie, Zengqi. In Chem. Eur. J., 28(29). 2022.
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  A starlike heterocyclic molecule containing an electron-deficient nonaaza-core structure and three peripheral isoquinolines locked by three tetracoordinate borons, namely isoquinoline-nona-starazine (QNSA), is synthesized by using readily available reactants through a rather straightforward approach. This new heteroatom-rich QNSA possesses a quasi-planar π-backbone structure, and bears phenyl substituents on borons which protrude on both sides of the π-backbones endowing it with good solubility in common organic solvents. Contrasting to its starphene analogue, QNSA shows intense fluorescence with a quantum yield (PLQY) of up to 62 % in dilute solution.

  @article{Feng_2022, abstract = {A starlike heterocyclic molecule containing an electron-deficient nonaaza-core structure and three peripheral isoquinolines locked by three tetracoordinate borons, namely isoquinoline-nona-starazine (QNSA), is synthesized by using readily available reactants through a rather straightforward approach. This new heteroatom-rich QNSA possesses a quasi-planar π-backbone structure, and bears phenyl substituents on borons which protrude on both sides of the π-backbones endowing it with good solubility in common organic solvents. Contrasting to its starphene analogue, QNSA shows intense fluorescence with a quantum yield (PLQY) of up to 62 % in dilute solution.}, author = {Feng, Yi and Zhou, Jiadong and Qiu, Honglin and Schnitzlein, Matthias and Hu, Jingtao and Liu, Linlin and Würthner, Frank and Xie, Zengqi}, journal = {Chem. Eur. J.}, keywords = {myown}, month = {04}, number = 29, publisher = {Wiley}, title = {Boron-Locked Starazine - A Soluble and Fluorescent Analogue of Starphene}, volume = 28, year = 2022 }

  %0 Journal Article %1 Feng_2022 %A Feng, Yi %A Zhou, Jiadong %A Qiu, Honglin %A Schnitzlein, Matthias %A Hu, Jingtao %A Liu, Linlin %A Würthner, Frank %A Xie, Zengqi %D 2022 %I Wiley %J Chem. Eur. J. %N 29 %R 10.1002/chem.202200770 %T Boron-Locked Starazine - A Soluble and Fluorescent Analogue of Starphene %U https://doi.org/10.1002%2Fchem.202200770 %V 28 %X A starlike heterocyclic molecule containing an electron-deficient nonaaza-core structure and three peripheral isoquinolines locked by three tetracoordinate borons, namely isoquinoline-nona-starazine (QNSA), is synthesized by using readily available reactants through a rather straightforward approach. This new heteroatom-rich QNSA possesses a quasi-planar π-backbone structure, and bears phenyl substituents on borons which protrude on both sides of the π-backbones endowing it with good solubility in common organic solvents. Contrasting to its starphene analogue, QNSA shows intense fluorescence with a quantum yield (PLQY) of up to 62 % in dilute solution.
• Supramolecular p/n-heterojunction of C60-functionalized bis(merocyanine) quadruple stack: A model system for charge carrier separation and recombination in organic solar cells. Bialas, David; Fennel, Franziska; Noll, Niklas; Holzapfel, Marco; Schmiedel, Alexander; Lambert, Christoph; Würthner, Frank. In Nat. Sci., 2(2). 2022.
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  Supramolecular photosystems can afford important insights into elementary processes in molecular materials. Here, a bis(merocyanine)-C60 conjugate composed of two covalently tethered electron-donating merocyanine chromophores and two appended fullerene electron acceptor units is investigated. Concentration-dependent UV/Vis studies in nonpolar solvents revealed a bimolecular association (dimerization) process, resulting in the formation of an H-coupled merocyanine dye aggregate. The aggregate structure was confirmed by 2D NMR spectroscopy proving the presence of a well-defined quadruple dye stack surrounded by four loosely connected fullerenes, which mimics the donor–acceptor interface in bulk heterojunction (BHJ) solar cells. Due to the interdigitation of the dyes in the quadruple stack motif, even at low concentrations, fully aggregated species prevail in nonpolar solvents, which enabled us to elucidate the photophysics of this supramolecular p/n-heterojunction in dilute solution by femtosecond time-resolved transient absorption spectroscopy. The observed photophysical processes include a favorably fast photoinduced electron transfer from the electron-donating dye stack to the electron-accepting fullerene moieties, a slower geminate charge carrier recombination of the generated electron and hole in the supramolecular p/n-heterojunction as well as the formation of fullerene triplet states. While the geminate recombination of charge carriers is supposed to be less competitive in BHJ photovoltaic materials due to the possibility of fast electron migration within fullerene domains in thin films, intersystem crossing into the triplet manifold appears as a more critical undesired process. These insights from spectroscopy may help to tailor improved photovoltaic materials, thereby demonstrating the value of fundamental studies on elementary photophysical processes in molecular aggregates.

  @article{Bialas_2022, abstract = {Supramolecular photosystems can afford important insights into elementary processes in molecular materials. Here, a bis(merocyanine)-C60 conjugate composed of two covalently tethered electron-donating merocyanine chromophores and two appended fullerene electron acceptor units is investigated. Concentration-dependent UV/Vis studies in nonpolar solvents revealed a bimolecular association (dimerization) process, resulting in the formation of an H-coupled merocyanine dye aggregate. The aggregate structure was confirmed by 2D NMR spectroscopy proving the presence of a well-defined quadruple dye stack surrounded by four loosely connected fullerenes, which mimics the donor–acceptor interface in bulk heterojunction (BHJ) solar cells. Due to the interdigitation of the dyes in the quadruple stack motif, even at low concentrations, fully aggregated species prevail in nonpolar solvents, which enabled us to elucidate the photophysics of this supramolecular p/n-heterojunction in dilute solution by femtosecond time-resolved transient absorption spectroscopy. The observed photophysical processes include a favorably fast photoinduced electron transfer from the electron-donating dye stack to the electron-accepting fullerene moieties, a slower geminate charge carrier recombination of the generated electron and hole in the supramolecular p/n-heterojunction as well as the formation of fullerene triplet states. While the geminate recombination of charge carriers is supposed to be less competitive in BHJ photovoltaic materials due to the possibility of fast electron migration within fullerene domains in thin films, intersystem crossing into the triplet manifold appears as a more critical undesired process. These insights from spectroscopy may help to tailor improved photovoltaic materials, thereby demonstrating the value of fundamental studies on elementary photophysical processes in molecular aggregates.}, author = {Bialas, David and Fennel, Franziska and Noll, Niklas and Holzapfel, Marco and Schmiedel, Alexander and Lambert, Christoph and Würthner, Frank}, journal = {Nat. Sci.}, keywords = {myown}, month = {03}, number = 2, publisher = {Wiley}, title = {Supramolecular p/n-heterojunction of C60-functionalized bis(merocyanine) quadruple stack: A model system for charge carrier separation and recombination in organic solar cells}, volume = 2, year = 2022 }

  %0 Journal Article %1 Bialas_2022 %A Bialas, David %A Fennel, Franziska %A Noll, Niklas %A Holzapfel, Marco %A Schmiedel, Alexander %A Lambert, Christoph %A Würthner, Frank %D 2022 %I Wiley %J Nat. Sci. %N 2 %R 10.1002/ntls.20210430 %T Supramolecular p/n-heterojunction of C60-functionalized bis(merocyanine) quadruple stack: A model system for charge carrier separation and recombination in organic solar cells %U https://doi.org/10.1002%2Fntls.20210430 %V 2 %X Supramolecular photosystems can afford important insights into elementary processes in molecular materials. Here, a bis(merocyanine)-C60 conjugate composed of two covalently tethered electron-donating merocyanine chromophores and two appended fullerene electron acceptor units is investigated. Concentration-dependent UV/Vis studies in nonpolar solvents revealed a bimolecular association (dimerization) process, resulting in the formation of an H-coupled merocyanine dye aggregate. The aggregate structure was confirmed by 2D NMR spectroscopy proving the presence of a well-defined quadruple dye stack surrounded by four loosely connected fullerenes, which mimics the donor–acceptor interface in bulk heterojunction (BHJ) solar cells. Due to the interdigitation of the dyes in the quadruple stack motif, even at low concentrations, fully aggregated species prevail in nonpolar solvents, which enabled us to elucidate the photophysics of this supramolecular p/n-heterojunction in dilute solution by femtosecond time-resolved transient absorption spectroscopy. The observed photophysical processes include a favorably fast photoinduced electron transfer from the electron-donating dye stack to the electron-accepting fullerene moieties, a slower geminate charge carrier recombination of the generated electron and hole in the supramolecular p/n-heterojunction as well as the formation of fullerene triplet states. While the geminate recombination of charge carriers is supposed to be less competitive in BHJ photovoltaic materials due to the possibility of fast electron migration within fullerene domains in thin films, intersystem crossing into the triplet manifold appears as a more critical undesired process. These insights from spectroscopy may help to tailor improved photovoltaic materials, thereby demonstrating the value of fundamental studies on elementary photophysical processes in molecular aggregates.
• Enantioselective Recognition of Helicenes by a Tailored Chiral Benzo[ghi]perylene Trisimide pi-Scaffold. Teichmann, Ben; Krause, Ana-Maria; Lin, Mei-Jin; Würthner, Frank. In Angew. Chem. Int. Ed., 61(15). 2022.
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  Enantioselective molecular recognition of chiral molecules that lack specific interaction sites for hydrogen bonding or Lewis acid–base interactions remains challenging. Here we introduce the concept of tailored chiral π-surfaces toward the maximization of shape complementarity. As we demonstrate for helicenes it is indeed possible by pure van-der-Waals interactions (π–π interactions and CH–π interactions) to accomplish enantioselective binding. This is shown for a novel benzo[ghi]perylene trisimide (BPTI) receptor whose π-scaffold is contorted into a chiral plane by functionalization with 1,1′-bi-2-naphthol (BINOL). Complexation experiments of enantiopure (P)-BPTI with (P)- and (M)-[6]helicene afforded binding constants of 10 700 M−1 and 550 M−1, respectively, thereby demonstrating the pronounced enantiodifferentiation by the homochiral π-scaffold of the BPTI host. The enantioselective recognition is even observable by the naked eye due to a specific exciplex-type emission originating from the interacting homochiral π-scaffolds of electron-rich [6]helicene and electron-poor BPTI.

  @article{Teichmann_2022, abstract = {Enantioselective molecular recognition of chiral molecules that lack specific interaction sites for hydrogen bonding or Lewis acid–base interactions remains challenging. Here we introduce the concept of tailored chiral π-surfaces toward the maximization of shape complementarity. As we demonstrate for helicenes it is indeed possible by pure van-der-Waals interactions (π–π interactions and CH–π interactions) to accomplish enantioselective binding. This is shown for a novel benzo[ghi]perylene trisimide (BPTI) receptor whose π-scaffold is contorted into a chiral plane by functionalization with 1,1′-bi-2-naphthol (BINOL). Complexation experiments of enantiopure (P)-BPTI with (P)- and (M)-[6]helicene afforded binding constants of 10 700 M−1 and 550 M−1, respectively, thereby demonstrating the pronounced enantiodifferentiation by the homochiral π-scaffold of the BPTI host. The enantioselective recognition is even observable by the naked eye due to a specific exciplex-type emission originating from the interacting homochiral π-scaffolds of electron-rich [6]helicene and electron-poor BPTI.}, author = {Teichmann, Ben and Krause, Ana-Maria and Lin, Mei-Jin and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {02}, number = 15, publisher = {Wiley}, title = {Enantioselective Recognition of Helicenes by a Tailored Chiral Benzo[ghi]perylene Trisimide pi-Scaffold}, volume = 61, year = 2022 }

  %0 Journal Article %1 Teichmann_2022 %A Teichmann, Ben %A Krause, Ana-Maria %A Lin, Mei-Jin %A Würthner, Frank %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %N 15 %R 10.1002/anie.202117625 %T Enantioselective Recognition of Helicenes by a Tailored Chiral Benzo[ghi]perylene Trisimide pi-Scaffold %U https://doi.org/10.1002%2Fanie.202117625 %V 61 %X Enantioselective molecular recognition of chiral molecules that lack specific interaction sites for hydrogen bonding or Lewis acid–base interactions remains challenging. Here we introduce the concept of tailored chiral π-surfaces toward the maximization of shape complementarity. As we demonstrate for helicenes it is indeed possible by pure van-der-Waals interactions (π–π interactions and CH–π interactions) to accomplish enantioselective binding. This is shown for a novel benzo[ghi]perylene trisimide (BPTI) receptor whose π-scaffold is contorted into a chiral plane by functionalization with 1,1′-bi-2-naphthol (BINOL). Complexation experiments of enantiopure (P)-BPTI with (P)- and (M)-[6]helicene afforded binding constants of 10 700 M−1 and 550 M−1, respectively, thereby demonstrating the pronounced enantiodifferentiation by the homochiral π-scaffold of the BPTI host. The enantioselective recognition is even observable by the naked eye due to a specific exciplex-type emission originating from the interacting homochiral π-scaffolds of electron-rich [6]helicene and electron-poor BPTI.
• Fluorescence Enhancement by Supramolecular Sequestration of a C54-Nanographene Trisimide by Hexabenzocoronene. Pigulski, Bartłomiej; Shoyama, Kazutaka; Sun, Meng-Jia; Würthner, Frank. In J. Am. Chem. Soc., 144(13), pp. 5718–5722. 2022.
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  A supramolecular trilayer nanographene complex consisting of a newly synthesized D3h-symmetric C 54-nanographene trisimide (NTI 1) and two hexabenzocoronenes (HBC) has been obtained by self-assembly. This 1:2 complex is structurally well- defined according to UV/vis and single crystal X-ray studies and exhibits high thermodynamic stability even in polar halogenated solvents. Complexation of NTI 1 by two HBC molecules protects the NTI 1 π-surface efficiently from oxygen quenching, thereby leading to a sequestration-induced fluorescence enhancement under ambient conditions.

  @article{Pigulski_2022, abstract = {A supramolecular trilayer nanographene complex consisting of a newly synthesized D3h-symmetric C 54-nanographene trisimide (NTI 1) and two hexabenzocoronenes (HBC) has been obtained by self-assembly. This 1:2 complex is structurally well- defined according to UV/vis and single crystal X-ray studies and exhibits high thermodynamic stability even in polar halogenated solvents. Complexation of NTI 1 by two HBC molecules protects the NTI 1 π-surface efficiently from oxygen quenching, thereby leading to a sequestration-induced fluorescence enhancement under ambient conditions.}, author = {Pigulski, Bartłomiej and Shoyama, Kazutaka and Sun, Meng-Jia and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {03}, number = 13, pages = {5718–5722}, publisher = {American Chemical Society (ACS)}, title = {Fluorescence Enhancement by Supramolecular Sequestration of a C54-Nanographene Trisimide by Hexabenzocoronene}, volume = 144, year = 2022 }

  %0 Journal Article %1 Pigulski_2022 %A Pigulski, Bartłomiej %A Shoyama, Kazutaka %A Sun, Meng-Jia %A Würthner, Frank %D 2022 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 13 %P 5718--5722 %R 10.1021/jacs.2c00142 %T Fluorescence Enhancement by Supramolecular Sequestration of a C54-Nanographene Trisimide by Hexabenzocoronene %U https://doi.org/10.1021%2Fjacs.2c00142 %V 144 %X A supramolecular trilayer nanographene complex consisting of a newly synthesized D3h-symmetric C 54-nanographene trisimide (NTI 1) and two hexabenzocoronenes (HBC) has been obtained by self-assembly. This 1:2 complex is structurally well- defined according to UV/vis and single crystal X-ray studies and exhibits high thermodynamic stability even in polar halogenated solvents. Complexation of NTI 1 by two HBC molecules protects the NTI 1 π-surface efficiently from oxygen quenching, thereby leading to a sequestration-induced fluorescence enhancement under ambient conditions.
• Organic Light-Emitting Diodes Based on Silandiol-Bay-Bridged Perylene Bisimides. Brust, Felix; Nagler, Oliver; Shoyama, Kazutaka; Stolte, Matthias; Würthner, Frank. In Adv. Optical Mater., 11(5). 2022.
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  Perylene bisimides (PBIs) are among the best fluorophores but have to be enwrapped for optoelectronic applications by large and heavy substituents to prevent their ππ-stacking, which is known to accelerate non-radiative decay processes in the solid state. Here, light-weight di-tert-butylsilyl groups are introduced to bridge 1,12-dihydroxy and 1,6,7,12-tetrahydroxy PBIs to afford sublimable dyes for vacuum-processed optoelectronic devices. For both new compounds, this substitution provides a twisted and shielded perylene π-core whose, via OSiObridges, rigid structure affords well-resolved absorption and emission spectra with strong fluorescence in solution, as well as in the solid state. The usefulness of these dyes for vacuum-processed optoelectronic devices is demonstrated in organic light-emitting diodes (OLEDs) that show monomer-like emission spectra and high maximum external quantum efficiency (EQEmax) values of up to 3.1% for the doubly silicon-bridged PBI.

  @article{Brust_2022, abstract = {Perylene bisimides (PBIs) are among the best fluorophores but have to be enwrapped for optoelectronic applications by large and heavy substituents to prevent their ππ-stacking, which is known to accelerate non-radiative decay processes in the solid state. Here, light-weight di-tert-butylsilyl groups are introduced to bridge 1,12-dihydroxy and 1,6,7,12-tetrahydroxy PBIs to afford sublimable dyes for vacuum-processed optoelectronic devices. For both new compounds, this substitution provides a twisted and shielded perylene π-core whose, via OSiObridges, rigid structure affords well-resolved absorption and emission spectra with strong fluorescence in solution, as well as in the solid state. The usefulness of these dyes for vacuum-processed optoelectronic devices is demonstrated in organic light-emitting diodes (OLEDs) that show monomer-like emission spectra and high maximum external quantum efficiency (EQEmax) values of up to 3.1% for the doubly silicon-bridged PBI.}, author = {Brust, Felix and Nagler, Oliver and Shoyama, Kazutaka and Stolte, Matthias and Würthner, Frank}, journal = {Adv. Optical Mater.}, keywords = {myown}, month = 12, number = 5, publisher = {Wiley}, title = {Organic Light-Emitting Diodes Based on Silandiol-Bay-Bridged Perylene Bisimides}, volume = 11, year = 2022 }

  %0 Journal Article %1 Brust_2022 %A Brust, Felix %A Nagler, Oliver %A Shoyama, Kazutaka %A Stolte, Matthias %A Würthner, Frank %D 2022 %I Wiley %J Adv. Optical Mater. %N 5 %R 10.1002/adom.202202676 %T Organic Light-Emitting Diodes Based on Silandiol-Bay-Bridged Perylene Bisimides %U https://doi.org/10.1002%2Fadom.202202676 %V 11 %X Perylene bisimides (PBIs) are among the best fluorophores but have to be enwrapped for optoelectronic applications by large and heavy substituents to prevent their ππ-stacking, which is known to accelerate non-radiative decay processes in the solid state. Here, light-weight di-tert-butylsilyl groups are introduced to bridge 1,12-dihydroxy and 1,6,7,12-tetrahydroxy PBIs to afford sublimable dyes for vacuum-processed optoelectronic devices. For both new compounds, this substitution provides a twisted and shielded perylene π-core whose, via OSiObridges, rigid structure affords well-resolved absorption and emission spectra with strong fluorescence in solution, as well as in the solid state. The usefulness of these dyes for vacuum-processed optoelectronic devices is demonstrated in organic light-emitting diodes (OLEDs) that show monomer-like emission spectra and high maximum external quantum efficiency (EQEmax) values of up to 3.1% for the doubly silicon-bridged PBI.
• Tuning Exciton Coupling of Merocyanine Nucleoside Dimers by RNA, DNA and GNA Double Helix Conformations. Dietzsch, Julia; Bialas, David; Bandorf, Johannes; Würthner, Frank; Höbartner, Claudia. In Angew. Chem. Int. Ed. 2022.
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  Exciton coupling between two or more chromophores in a specific environment is a key mechanism associated with color tuning and modulation of absorption energies. This concept is well exemplified by natural photosynthetic proteins, and can also be achieved in synthetic nucleic acid nanostructures. Here we report the coupling of barbituric acid merocyanine (BAM) nucleoside analogues and show that exciton coupling can be tuned by the double helix conformation. BAM is a nucleobase mimic that was incorporated in the phosphodiester backbone of RNA, DNA and GNA oligonucleotides. Duplexes with different backbone constitutions and geometries afforded different mutual dye arrangements, leading to distinct optical signatures due to competing modes of chromophore organization via electrostatic, dipolar, π–π-stacking and hydrogen-bonding interactions. The realized supramolecular motifs include hydrogenbonded BAM–adenine base pairs and antiparallel as well as rotationally stacked BAM dimer aggregates with distinct absorption, CD and fluorescence properties.

  @article{Dietzsch_2022, abstract = {Exciton coupling between two or more chromophores in a specific environment is a key mechanism associated with color tuning and modulation of absorption energies. This concept is well exemplified by natural photosynthetic proteins, and can also be achieved in synthetic nucleic acid nanostructures. Here we report the coupling of barbituric acid merocyanine (BAM) nucleoside analogues and show that exciton coupling can be tuned by the double helix conformation. BAM is a nucleobase mimic that was incorporated in the phosphodiester backbone of RNA, DNA and GNA oligonucleotides. Duplexes with different backbone constitutions and geometries afforded different mutual dye arrangements, leading to distinct optical signatures due to competing modes of chromophore organization via electrostatic, dipolar, π–π-stacking and hydrogen-bonding interactions. The realized supramolecular motifs include hydrogenbonded BAM–adenine base pairs and antiparallel as well as rotationally stacked BAM dimer aggregates with distinct absorption, CD and fluorescence properties.}, author = {Dietzsch, Julia and Bialas, David and Bandorf, Johannes and Würthner, Frank and Höbartner, Claudia}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {01}, publisher = {Wiley}, title = {Tuning Exciton Coupling of Merocyanine Nucleoside Dimers by RNA, DNA and GNA Double Helix Conformations}, year = 2022 }

  %0 Journal Article %1 Dietzsch_2022 %A Dietzsch, Julia %A Bialas, David %A Bandorf, Johannes %A Würthner, Frank %A Höbartner, Claudia %D 2022 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202116783 %T Tuning Exciton Coupling of Merocyanine Nucleoside Dimers by RNA, DNA and GNA Double Helix Conformations %U https://doi.org/10.1002%2Fanie.202116783 %X Exciton coupling between two or more chromophores in a specific environment is a key mechanism associated with color tuning and modulation of absorption energies. This concept is well exemplified by natural photosynthetic proteins, and can also be achieved in synthetic nucleic acid nanostructures. Here we report the coupling of barbituric acid merocyanine (BAM) nucleoside analogues and show that exciton coupling can be tuned by the double helix conformation. BAM is a nucleobase mimic that was incorporated in the phosphodiester backbone of RNA, DNA and GNA oligonucleotides. Duplexes with different backbone constitutions and geometries afforded different mutual dye arrangements, leading to distinct optical signatures due to competing modes of chromophore organization via electrostatic, dipolar, π–π-stacking and hydrogen-bonding interactions. The realized supramolecular motifs include hydrogenbonded BAM–adenine base pairs and antiparallel as well as rotationally stacked BAM dimer aggregates with distinct absorption, CD and fluorescence properties.
• Ultrafast Intersystem Crossing in Selenium-Annulated Perylene Bisimide. Sivanarayanan, Jibin; Sebastian, Ebin; Vinod, Kavya; Würthner, Frank; Hariharan, Mahesh. In J. Phys. Chem. C., 126(31), pp. 13319–13326. 2022.
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  An intersystem crossing (ISC), the non-radiative transition between two electronic states with different spin multiplicities, is ubiquitous and imperative in molecular photochemistry. The manifestation of a triplet manifold in π-conjugated chromophoric materials has a crucial role in enhancing the efficiency of photofunctional devices. Herein, we explore the triplet-state population in a series of chalcogen-annulated perylene bisimides (O-PBI, S-PBI, and Se-PBI), where the selenium-annulated PBI (Se-PBI) exhibits a near-quantitative triplet quantum yield ( = 94 ± 1%). Annulation of Se in the PBI core results in a drastic decrease in the fluorescence quantum yield ( = 1.5 ± 0.2%) compared to the bare PBI ( = 97.0 ± 1%), indicating the possibility of an efficient non-radiative decay pathway in the Se-PBI motif. Femtosecond and nanosecond transient absorption measurements unambiguously confirmed the ultrafast triplet population in Se-PBI with an ISC rate constant of = 2.39 × 1010 s–1 and the triplet-state decay to the ground state with a time constant of 3.78 μs. A theoretically calculated spin–orbit coupling constant (VSOC) of 122.4 cm–1 employing the SA-CASSCF/NEVPT2 method has rationalized the excited-state dynamics of Se-PBI. By virtue of the poor SOC between the singlet and triplet states, we observed a partial triplet population in S-PBI, whereas ISC is negligible in O-PBI. We demonstrate an increase in the spin–orbit coupling constant ( ≪ < ) and rate constant of ISC ( ≪ < ) across the series of chalcogen-annulated PBIs (O-PBI, S-PBI, and Se-PBI). The heavier chalcogenide PBI (Se-PBI) thus adds to the array of potential organic photoactive materials for the design of efficient solar energy conversion devices.

  @article{Sivanarayanan_2022, abstract = {An intersystem crossing (ISC), the non-radiative transition between two electronic states with different spin multiplicities, is ubiquitous and imperative in molecular photochemistry. The manifestation of a triplet manifold in π-conjugated chromophoric materials has a crucial role in enhancing the efficiency of photofunctional devices. Herein, we explore the triplet-state population in a series of chalcogen-annulated perylene bisimides (O-PBI, S-PBI, and Se-PBI), where the selenium-annulated PBI (Se-PBI) exhibits a near-quantitative triplet quantum yield ( = 94 ± 1%). Annulation of Se in the PBI core results in a drastic decrease in the fluorescence quantum yield ( = 1.5 ± 0.2%) compared to the bare PBI ( = 97.0 ± 1%), indicating the possibility of an efficient non-radiative decay pathway in the Se-PBI motif. Femtosecond and nanosecond transient absorption measurements unambiguously confirmed the ultrafast triplet population in Se-PBI with an ISC rate constant of = 2.39 × 1010 s–1 and the triplet-state decay to the ground state with a time constant of 3.78 μs. A theoretically calculated spin–orbit coupling constant (VSOC) of 122.4 cm–1 employing the SA-CASSCF/NEVPT2 method has rationalized the excited-state dynamics of Se-PBI. By virtue of the poor SOC between the singlet and triplet states, we observed a partial triplet population in S-PBI, whereas ISC is negligible in O-PBI. We demonstrate an increase in the spin–orbit coupling constant ( ≪ < ) and rate constant of ISC ( ≪ < ) across the series of chalcogen-annulated PBIs (O-PBI, S-PBI, and Se-PBI). The heavier chalcogenide PBI (Se-PBI) thus adds to the array of potential organic photoactive materials for the design of efficient solar energy conversion devices.}, author = {Sivanarayanan, Jibin and Sebastian, Ebin and Vinod, Kavya and Würthner, Frank and Hariharan, Mahesh}, journal = {J. Phys. Chem. C.}, keywords = {myown}, month = {07}, number = 31, pages = {13319–13326}, publisher = {American Chemical Society (ACS)}, title = {Ultrafast Intersystem Crossing in Selenium-Annulated Perylene Bisimide}, volume = 126, year = 2022 }

  %0 Journal Article %1 Sivanarayanan_2022 %A Sivanarayanan, Jibin %A Sebastian, Ebin %A Vinod, Kavya %A Würthner, Frank %A Hariharan, Mahesh %D 2022 %I American Chemical Society (ACS) %J J. Phys. Chem. C. %N 31 %P 13319--13326 %R 10.1021/acs.jpcc.2c03847 %T Ultrafast Intersystem Crossing in Selenium-Annulated Perylene Bisimide %U https://doi.org/10.1021%2Facs.jpcc.2c03847 %V 126 %X An intersystem crossing (ISC), the non-radiative transition between two electronic states with different spin multiplicities, is ubiquitous and imperative in molecular photochemistry. The manifestation of a triplet manifold in π-conjugated chromophoric materials has a crucial role in enhancing the efficiency of photofunctional devices. Herein, we explore the triplet-state population in a series of chalcogen-annulated perylene bisimides (O-PBI, S-PBI, and Se-PBI), where the selenium-annulated PBI (Se-PBI) exhibits a near-quantitative triplet quantum yield ( = 94 ± 1%). Annulation of Se in the PBI core results in a drastic decrease in the fluorescence quantum yield ( = 1.5 ± 0.2%) compared to the bare PBI ( = 97.0 ± 1%), indicating the possibility of an efficient non-radiative decay pathway in the Se-PBI motif. Femtosecond and nanosecond transient absorption measurements unambiguously confirmed the ultrafast triplet population in Se-PBI with an ISC rate constant of = 2.39 × 1010 s–1 and the triplet-state decay to the ground state with a time constant of 3.78 μs. A theoretically calculated spin–orbit coupling constant (VSOC) of 122.4 cm–1 employing the SA-CASSCF/NEVPT2 method has rationalized the excited-state dynamics of Se-PBI. By virtue of the poor SOC between the singlet and triplet states, we observed a partial triplet population in S-PBI, whereas ISC is negligible in O-PBI. We demonstrate an increase in the spin–orbit coupling constant ( ≪ < ) and rate constant of ISC ( ≪ < ) across the series of chalcogen-annulated PBIs (O-PBI, S-PBI, and Se-PBI). The heavier chalcogenide PBI (Se-PBI) thus adds to the array of potential organic photoactive materials for the design of efficient solar energy conversion devices.
• Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity. Hong, Yongseok; Schlosser, Felix; Kim, Woojae; Würthner, Frank; Kim, Dongho. In J. Am. Chem. Soc., 144(34), pp. 15539–15548. 2022.
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  Perylene bisimides (PBIs) have received great attention in their applicability to optoelectronics. Especially, symmetry-breaking charge separation (SB-CS) in PBIs has been investigated to mimic the efficient light capturing and charge generation in natural light-harvesting systems. However, unlike ultrafast CS dynamics in donor–acceptor heterojunction materials, ultrafast SB-CS in a stacked homodimer has still been challenging due to excimer formation in the absence of rigidifying surroundings such as a special pair in the natural systems. Herein, we present the detailed mechanism of ultrafast photoinduced SB-CS occurring in a 1,7-bis(N-pyrrolidinyl) PBI dimer within a cyclophane. Through narrow-band and broad-band transient absorption spectroscopy, we demonstrate that ultrafast SB-CS in the dimer is enabled by the combination of (1) vibrationally coherent charge-transfer resonance-enhanced excimer formation and (2) breakdown of adiabaticity (formation of SB-CS diabats) in the excimer state via structural and solvent fluctuation. Quantum chemical calculations also underpin that the participation of strong electron-donating substituents in overall vibrational modes plays a crucial role in triggering the ultrafast SB-CS. Therefore, our work provides an alternative route to facilitate ultrafast SB-CS in PBIs and thereby establishes a novel strategy for the design of optoelectronic materials.

  @article{Hong_2022, abstract = {Perylene bisimides (PBIs) have received great attention in their applicability to optoelectronics. Especially, symmetry-breaking charge separation (SB-CS) in PBIs has been investigated to mimic the efficient light capturing and charge generation in natural light-harvesting systems. However, unlike ultrafast CS dynamics in donor–acceptor heterojunction materials, ultrafast SB-CS in a stacked homodimer has still been challenging due to excimer formation in the absence of rigidifying surroundings such as a special pair in the natural systems. Herein, we present the detailed mechanism of ultrafast photoinduced SB-CS occurring in a 1,7-bis(N-pyrrolidinyl) PBI dimer within a cyclophane. Through narrow-band and broad-band transient absorption spectroscopy, we demonstrate that ultrafast SB-CS in the dimer is enabled by the combination of (1) vibrationally coherent charge-transfer resonance-enhanced excimer formation and (2) breakdown of adiabaticity (formation of SB-CS diabats) in the excimer state via structural and solvent fluctuation. Quantum chemical calculations also underpin that the participation of strong electron-donating substituents in overall vibrational modes plays a crucial role in triggering the ultrafast SB-CS. Therefore, our work provides an alternative route to facilitate ultrafast SB-CS in PBIs and thereby establishes a novel strategy for the design of optoelectronic materials.}, author = {Hong, Yongseok and Schlosser, Felix and Kim, Woojae and Würthner, Frank and Kim, Dongho}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {08}, number = 34, pages = {15539–15548}, publisher = {American Chemical Society ({ACS})}, title = {Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity}, volume = 144, year = 2022 }

  %0 Journal Article %1 Hong_2022 %A Hong, Yongseok %A Schlosser, Felix %A Kim, Woojae %A Würthner, Frank %A Kim, Dongho %D 2022 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 34 %P 15539--15548 %R 10.1021/jacs.2c03916 %T Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity %U https://doi.org/10.1021%2Fjacs.2c03916 %V 144 %X Perylene bisimides (PBIs) have received great attention in their applicability to optoelectronics. Especially, symmetry-breaking charge separation (SB-CS) in PBIs has been investigated to mimic the efficient light capturing and charge generation in natural light-harvesting systems. However, unlike ultrafast CS dynamics in donor–acceptor heterojunction materials, ultrafast SB-CS in a stacked homodimer has still been challenging due to excimer formation in the absence of rigidifying surroundings such as a special pair in the natural systems. Herein, we present the detailed mechanism of ultrafast photoinduced SB-CS occurring in a 1,7-bis(N-pyrrolidinyl) PBI dimer within a cyclophane. Through narrow-band and broad-band transient absorption spectroscopy, we demonstrate that ultrafast SB-CS in the dimer is enabled by the combination of (1) vibrationally coherent charge-transfer resonance-enhanced excimer formation and (2) breakdown of adiabaticity (formation of SB-CS diabats) in the excimer state via structural and solvent fluctuation. Quantum chemical calculations also underpin that the participation of strong electron-donating substituents in overall vibrational modes plays a crucial role in triggering the ultrafast SB-CS. Therefore, our work provides an alternative route to facilitate ultrafast SB-CS in PBIs and thereby establishes a novel strategy for the design of optoelectronic materials.
• A Covalent Organic Framework for Cooperative Water Oxidation. Karak, Suvendu; Stepanenko, Vladimir; Addicoat, Matthew A.; Kessler, Philipp; Moser, Simon; Beuerle, Florian; Würthner, Frank. In J. Am. Chem. Soc., 144(38), pp. 17661–17670. 2022.
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  The future of water-derived hydrogen as the “sustainable energy source” straightaway bets on the success of the sluggish oxygen-generating half-reaction. The endeavor to emulate the natural photosystem II for efficient water oxidation has been extended across the spectrum of organic and inorganic combinations. However, the achievement has so far been restricted to homogeneous catalysts rather than their pristine heterogeneous forms. The poor structural understanding and control over the mechanistic pathway often impede the overall development. Herein, we have synthesized a highly crystalline covalent organic framework (COF) for chemical and photochemical water oxidation. The interpenetrated structure assures the catalyst stability, as the catalyst’s performance remains unaltered after several cycles. This COF exhibits the highest ever accomplished catalytic activity for such an organometallic crystalline solid-state material where the rate of oxygen evolution is as high as ∼26,000 μmol L–1 s–1 (second-order rate constant k ≈ 1650 μmol L s–1 g–2). The catalyst also proves its exceptional activity (k ≈ 1600 μmol L s–1 g–2) during light-driven water oxidation under very dilute conditions. The cooperative interaction between metal centers in the crystalline network offers 20–30-fold superior activity during chemical as well as photocatalytic water oxidation as compared to its amorphous polymeric counterpart.

  @article{Karak_2022, abstract = {The future of water-derived hydrogen as the “sustainable energy source” straightaway bets on the success of the sluggish oxygen-generating half-reaction. The endeavor to emulate the natural photosystem II for efficient water oxidation has been extended across the spectrum of organic and inorganic combinations. However, the achievement has so far been restricted to homogeneous catalysts rather than their pristine heterogeneous forms. The poor structural understanding and control over the mechanistic pathway often impede the overall development. Herein, we have synthesized a highly crystalline covalent organic framework (COF) for chemical and photochemical water oxidation. The interpenetrated structure assures the catalyst stability, as the catalyst’s performance remains unaltered after several cycles. This COF exhibits the highest ever accomplished catalytic activity for such an organometallic crystalline solid-state material where the rate of oxygen evolution is as high as ∼26,000 μmol L–1 s–1 (second-order rate constant k ≈ 1650 μmol L s–1 g–2). The catalyst also proves its exceptional activity (k ≈ 1600 μmol L s–1 g–2) during light-driven water oxidation under very dilute conditions. The cooperative interaction between metal centers in the crystalline network offers 20–30-fold superior activity during chemical as well as photocatalytic water oxidation as compared to its amorphous polymeric counterpart.}, author = {Karak, Suvendu and Stepanenko, Vladimir and Addicoat, Matthew A. and Kessler, Philipp and Moser, Simon and Beuerle, Florian and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {09}, number = 38, pages = {17661–17670}, publisher = {American Chemical Society ({ACS})}, title = {A Covalent Organic Framework for Cooperative Water Oxidation}, volume = 144, year = 2022 }

  %0 Journal Article %1 Karak_2022 %A Karak, Suvendu %A Stepanenko, Vladimir %A Addicoat, Matthew A. %A Kessler, Philipp %A Moser, Simon %A Beuerle, Florian %A Würthner, Frank %D 2022 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 38 %P 17661--17670 %R 10.1021/jacs.2c07282 %T A Covalent Organic Framework for Cooperative Water Oxidation %U https://doi.org/10.1021%2Fjacs.2c07282 %V 144 %X The future of water-derived hydrogen as the “sustainable energy source” straightaway bets on the success of the sluggish oxygen-generating half-reaction. The endeavor to emulate the natural photosystem II for efficient water oxidation has been extended across the spectrum of organic and inorganic combinations. However, the achievement has so far been restricted to homogeneous catalysts rather than their pristine heterogeneous forms. The poor structural understanding and control over the mechanistic pathway often impede the overall development. Herein, we have synthesized a highly crystalline covalent organic framework (COF) for chemical and photochemical water oxidation. The interpenetrated structure assures the catalyst stability, as the catalyst’s performance remains unaltered after several cycles. This COF exhibits the highest ever accomplished catalytic activity for such an organometallic crystalline solid-state material where the rate of oxygen evolution is as high as ∼26,000 μmol L–1 s–1 (second-order rate constant k ≈ 1650 μmol L s–1 g–2). The catalyst also proves its exceptional activity (k ≈ 1600 μmol L s–1 g–2) during light-driven water oxidation under very dilute conditions. The cooperative interaction between metal centers in the crystalline network offers 20–30-fold superior activity during chemical as well as photocatalytic water oxidation as compared to its amorphous polymeric counterpart.
• Axially chiral indolenine derived chromophore dimers and their chiroptical absorption and emission properties. Freytag, Emely; Holzapfel, Marco; Swain, Asim; Bringmann, Gerhard; Stolte, Matthias; Würthner, Frank; Lambert, Christoph. In Chem. Sci., 13(41), pp. 12229–12238. 2022.
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  Yamamoto homocoupling of two chiral oxindoles led to the atropo-diastereoselective formation of an axially chiral oxindole dimer. This building block served as the starting material for the syntheses of axially chiral squaraine and merocyanine chromophore dimers. These dimers show pronounced chiroptical properties, this is, outstandingly high ECD signals (Δε up to ca. 1500 M−1 cm−1) as a couplet with positive Cotton effect for the P-configuration around the biaryl axis and a negative Cotton effect for the M-configuration. All investigated dimers also exhibit pronounced circularly polarised emission with anisotropy values of ca. 10−3 cgs. Time-dependent density functional calculations were used to analyse the three contributions (local one electron, electric–magnetic coupling, and exciton coupling) to the rotational strength applying the Rosenfeld equation to excitonically coupled chromophores. While the exciton coupling term proves to be the dominant one, the electric–magnetic coupling possesses the same sign and adds significantly to the total rotational strength owing to a favourable geometric arrangement of the two chromophores within the dimer.

  @article{D2SC04600H, abstract = {Yamamoto homocoupling of two chiral oxindoles led to the atropo-diastereoselective formation of an axially chiral oxindole dimer. This building block served as the starting material for the syntheses of axially chiral squaraine and merocyanine chromophore dimers. These dimers show pronounced chiroptical properties{,} this is{,} outstandingly high ECD signals (Δε up to ca. 1500 M−1 cm−1) as a couplet with positive Cotton effect for the P-configuration around the biaryl axis and a negative Cotton effect for the M-configuration. All investigated dimers also exhibit pronounced circularly polarised emission with anisotropy values of ca. 10−3 cgs. Time-dependent density functional calculations were used to analyse the three contributions (local one electron{,} electric–magnetic coupling{,} and exciton coupling) to the rotational strength applying the Rosenfeld equation to excitonically coupled chromophores. While the exciton coupling term proves to be the dominant one{,} the electric–magnetic coupling possesses the same sign and adds significantly to the total rotational strength owing to a favourable geometric arrangement of the two chromophores within the dimer.}, author = {Freytag, Emely and Holzapfel, Marco and Swain, Asim and Bringmann, Gerhard and Stolte, Matthias and Würthner, Frank and Lambert, Christoph}, journal = {Chem. Sci.}, keywords = {myown}, number = 41, pages = {12229-12238}, publisher = {The Royal Society of Chemistry}, title = {Axially chiral indolenine derived chromophore dimers and their chiroptical absorption and emission properties}, volume = 13, year = 2022 }

  %0 Journal Article %1 D2SC04600H %A Freytag, Emely %A Holzapfel, Marco %A Swain, Asim %A Bringmann, Gerhard %A Stolte, Matthias %A Würthner, Frank %A Lambert, Christoph %D 2022 %I The Royal Society of Chemistry %J Chem. Sci. %N 41 %P 12229-12238 %R 10.1039/D2SC04600H %T Axially chiral indolenine derived chromophore dimers and their chiroptical absorption and emission properties %U http://dx.doi.org/10.1039/D2SC04600H %V 13 %X Yamamoto homocoupling of two chiral oxindoles led to the atropo-diastereoselective formation of an axially chiral oxindole dimer. This building block served as the starting material for the syntheses of axially chiral squaraine and merocyanine chromophore dimers. These dimers show pronounced chiroptical properties, this is, outstandingly high ECD signals (Δε up to ca. 1500 M−1 cm−1) as a couplet with positive Cotton effect for the P-configuration around the biaryl axis and a negative Cotton effect for the M-configuration. All investigated dimers also exhibit pronounced circularly polarised emission with anisotropy values of ca. 10−3 cgs. Time-dependent density functional calculations were used to analyse the three contributions (local one electron, electric–magnetic coupling, and exciton coupling) to the rotational strength applying the Rosenfeld equation to excitonically coupled chromophores. While the exciton coupling term proves to be the dominant one, the electric–magnetic coupling possesses the same sign and adds significantly to the total rotational strength owing to a favourable geometric arrangement of the two chromophores within the dimer.
• Enzyme-like water preorganization in a synthetic molecular cleft for homogeneous water oxidation catalysis. Noll, Niklas; Krause, Ana-Maria; Beuerle, Florian; Würthner, Frank. In Nature Catalysis, 5(10), pp. 867–877. 2022.
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  Inspired by the proficiency of natural enzymes, mimicking of nanoenvironments for precise substrate preorganization is a promising strategy in catalyst design. However, artificial examples of enzyme-like activation of H2O molecules for the challenging oxidative water splitting reaction are hardly explored. Here, we introduce a mononuclear Ru(bda) complex (M1, bda = 2,2′-bipyridine-6,6′-dicarboxylate) equipped with a bipyridine-functionalized ligand to preorganize H2O molecules in front of the metal centre as in enzymatic clefts. The confined pocket of M1 accelerates chemically driven water oxidation at pH 1 by facilitating a water nucleophilic attack pathway with a remarkable turnover frequency of 140 s−1 that is comparable to the oxygen-evolving complex of photosystem II. Single crystal X-ray analysis of M1 under catalytic conditions allowed the observation of a seventh H2O ligand directly coordinated to a RuIII centre. Another H2O substrate is preorganized via a well-defined hydrogen-bonding network for the crucial O–O bond formation by nucleophilic attack.

  @article{Noll_2022, abstract = {Inspired by the proficiency of natural enzymes, mimicking of nanoenvironments for precise substrate preorganization is a promising strategy in catalyst design. However, artificial examples of enzyme-like activation of H2O molecules for the challenging oxidative water splitting reaction are hardly explored. Here, we introduce a mononuclear Ru(bda) complex (M1, bda = 2,2′-bipyridine-6,6′-dicarboxylate) equipped with a bipyridine-functionalized ligand to preorganize H2O molecules in front of the metal centre as in enzymatic clefts. The confined pocket of M1 accelerates chemically driven water oxidation at pH 1 by facilitating a water nucleophilic attack pathway with a remarkable turnover frequency of 140 s−1 that is comparable to the oxygen-evolving complex of photosystem II. Single crystal X-ray analysis of M1 under catalytic conditions allowed the observation of a seventh H2O ligand directly coordinated to a RuIII centre. Another H2O substrate is preorganized via a well-defined hydrogen-bonding network for the crucial O–O bond formation by nucleophilic attack.}, author = {Noll, Niklas and Krause, Ana-Maria and Beuerle, Florian and Würthner, Frank}, journal = {Nature Catalysis}, keywords = {myown}, month = 10, number = 10, pages = {867–877}, publisher = {Springer Science and Business Media {LLC}}, title = {Enzyme-like water preorganization in a synthetic molecular cleft for homogeneous water oxidation catalysis}, volume = 5, year = 2022 }

  %0 Journal Article %1 Noll_2022 %A Noll, Niklas %A Krause, Ana-Maria %A Beuerle, Florian %A Würthner, Frank %D 2022 %I Springer Science and Business Media LLC %J Nature Catalysis %N 10 %P 867--877 %R 10.1038/s41929-022-00843-x %T Enzyme-like water preorganization in a synthetic molecular cleft for homogeneous water oxidation catalysis %U https://doi.org/10.1038%2Fs41929-022-00843-x %V 5 %X Inspired by the proficiency of natural enzymes, mimicking of nanoenvironments for precise substrate preorganization is a promising strategy in catalyst design. However, artificial examples of enzyme-like activation of H2O molecules for the challenging oxidative water splitting reaction are hardly explored. Here, we introduce a mononuclear Ru(bda) complex (M1, bda = 2,2′-bipyridine-6,6′-dicarboxylate) equipped with a bipyridine-functionalized ligand to preorganize H2O molecules in front of the metal centre as in enzymatic clefts. The confined pocket of M1 accelerates chemically driven water oxidation at pH 1 by facilitating a water nucleophilic attack pathway with a remarkable turnover frequency of 140 s−1 that is comparable to the oxygen-evolving complex of photosystem II. Single crystal X-ray analysis of M1 under catalytic conditions allowed the observation of a seventh H2O ligand directly coordinated to a RuIII centre. Another H2O substrate is preorganized via a well-defined hydrogen-bonding network for the crucial O–O bond formation by nucleophilic attack.
• Supramolecular Substructure of C60-Embedded Schwarzite. Zhu, Chongwei; Shoyama, Kazutaka; Niyas, M. A.; Würthner, Frank. In J. Am. Chem. Soc., 144(36), pp. 16282–16286. 2022.
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  Herein we present a new concept of carbon allotrope, namely, fullerene-embedded schwarzite. We isolated crystals of fullerene embedded in 4 equiv of a negatively curved polycyclic aromatic hydrocarbon (PAH), 1, which could be viewed as a substructure of the hypothetical fullerene–schwarzite complex. On the basis of crystal structure, the stability of the complex (C60⊂(1)4) was studied by theoretical methods (ALMO-EDA), showing that the noncovalent interactions driven by dispersion forces is key for stabilizing the complex, which was further supported by noncovalent interactions (NCI) plots and Hirshfeld-surface analyses. Our findings of C60⊂(1)4 provide a perspective toward the development of novel sp2-carbon allotropes comprising multiple components.

  @article{Zhu_2022, abstract = {Herein we present a new concept of carbon allotrope, namely, fullerene-embedded schwarzite. We isolated crystals of fullerene embedded in 4 equiv of a negatively curved polycyclic aromatic hydrocarbon (PAH), 1, which could be viewed as a substructure of the hypothetical fullerene–schwarzite complex. On the basis of crystal structure, the stability of the complex (C60⊂(1)4) was studied by theoretical methods (ALMO-EDA), showing that the noncovalent interactions driven by dispersion forces is key for stabilizing the complex, which was further supported by noncovalent interactions (NCI) plots and Hirshfeld-surface analyses. Our findings of C60⊂(1)4 provide a perspective toward the development of novel sp2-carbon allotropes comprising multiple components.}, author = {Zhu, Chongwei and Shoyama, Kazutaka and Niyas, M. A. and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {08}, number = 36, pages = {16282–16286}, publisher = {American Chemical Society ({ACS})}, title = {Supramolecular Substructure of C60-Embedded Schwarzite}, volume = 144, year = 2022 }

  %0 Journal Article %1 Zhu_2022 %A Zhu, Chongwei %A Shoyama, Kazutaka %A Niyas, M. A. %A Würthner, Frank %D 2022 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 36 %P 16282--16286 %R 10.1021/jacs.2c06933 %T Supramolecular Substructure of C60-Embedded Schwarzite %U https://doi.org/10.1021%2Fjacs.2c06933 %V 144 %X Herein we present a new concept of carbon allotrope, namely, fullerene-embedded schwarzite. We isolated crystals of fullerene embedded in 4 equiv of a negatively curved polycyclic aromatic hydrocarbon (PAH), 1, which could be viewed as a substructure of the hypothetical fullerene–schwarzite complex. On the basis of crystal structure, the stability of the complex (C60⊂(1)4) was studied by theoretical methods (ALMO-EDA), showing that the noncovalent interactions driven by dispersion forces is key for stabilizing the complex, which was further supported by noncovalent interactions (NCI) plots and Hirshfeld-surface analyses. Our findings of C60⊂(1)4 provide a perspective toward the development of novel sp2-carbon allotropes comprising multiple components.
• Excited states and spin–orbit coupling in chalcogen substituted perylene diimides and their radical anions. Mentzel, Paul; Holzapfel, Marco; Schmiedel, Alexander; Krummenacher, Ivo; Braunschweig, Holger; Wodyński, Artur; Kaupp, Martin; Würthner, Frank; Lambert, Christoph. In Phys. Chem. Chem. Phys., 24(42), pp. 26254–26268. 2022.
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  While spin–orbit coupling does not play a decisive role in the photophysics of unsubstituted perylene diimides (PDI), this changes dramatically when two phenylselenyl or phenyltelluryl substituents were attached to the PDI bay positions. In the series of PhO-, PhS-, PhSe-, and PhTe-substituted PDIs we observed strongly decreasing fluorescence quantum yield as a consequence of strongly increasing intersystem crossing (ISC) rate, measured by transient absorption spectroscopy with fs- and ns-time resolution as well as by broadband fluorescence upconversion. Time-dependent density functional calculations suggest increasing spin–orbit coupling due to the internal heavy-atom effect as the reason for fast ISC. In case of the selenium PDI derivative we found significant singlet oxygen sensitization via the PDI triplet state. The corresponding radical anions of the chalcogen substituted PDIs were also prepared and investigated by optical and EPR spectroscopy. Here, the increasing SOC results in an increase of the g-tensor anisotropy, and of the isotropic g-value in solution, albeit quasirelativistic density functional calculations show only a relatively small fraction of the spin density to be located on the chalcogen atom.

  @article{D2CP02723B, abstract = {While spin–orbit coupling does not play a decisive role in the photophysics of unsubstituted perylene diimides (PDI), this changes dramatically when two phenylselenyl or phenyltelluryl substituents were attached to the PDI bay positions. In the series of PhO-, PhS-, PhSe-, and PhTe-substituted PDIs we observed strongly decreasing fluorescence quantum yield as a consequence of strongly increasing intersystem crossing (ISC) rate, measured by transient absorption spectroscopy with fs- and ns-time resolution as well as by broadband fluorescence upconversion. Time-dependent density functional calculations suggest increasing spin–orbit coupling due to the internal heavy-atom effect as the reason for fast ISC. In case of the selenium PDI derivative we found significant singlet oxygen sensitization via the PDI triplet state. The corresponding radical anions of the chalcogen substituted PDIs were also prepared and investigated by optical and EPR spectroscopy. Here, the increasing SOC results in an increase of the g-tensor anisotropy, and of the isotropic g-value in solution, albeit quasirelativistic density functional calculations show only a relatively small fraction of the spin density to be located on the chalcogen atom.}, author = {Mentzel, Paul and Holzapfel, Marco and Schmiedel, Alexander and Krummenacher, Ivo and Braunschweig, Holger and Wodyński, Artur and Kaupp, Martin and Würthner, Frank and Lambert, Christoph}, journal = {Phys. Chem. Chem. Phys.}, keywords = {myown}, number = 42, pages = {26254-26268}, publisher = {The Royal Society of Chemistry}, title = {Excited states and spin–orbit coupling in chalcogen substituted perylene diimides and their radical anions}, volume = 24, year = 2022 }

  %0 Journal Article %1 D2CP02723B %A Mentzel, Paul %A Holzapfel, Marco %A Schmiedel, Alexander %A Krummenacher, Ivo %A Braunschweig, Holger %A Wodyński, Artur %A Kaupp, Martin %A Würthner, Frank %A Lambert, Christoph %D 2022 %I The Royal Society of Chemistry %J Phys. Chem. Chem. Phys. %N 42 %P 26254-26268 %R 10.1039/D2CP02723B %T Excited states and spin–orbit coupling in chalcogen substituted perylene diimides and their radical anions %U http://dx.doi.org/10.1039/D2CP02723B %V 24 %X While spin–orbit coupling does not play a decisive role in the photophysics of unsubstituted perylene diimides (PDI), this changes dramatically when two phenylselenyl or phenyltelluryl substituents were attached to the PDI bay positions. In the series of PhO-, PhS-, PhSe-, and PhTe-substituted PDIs we observed strongly decreasing fluorescence quantum yield as a consequence of strongly increasing intersystem crossing (ISC) rate, measured by transient absorption spectroscopy with fs- and ns-time resolution as well as by broadband fluorescence upconversion. Time-dependent density functional calculations suggest increasing spin–orbit coupling due to the internal heavy-atom effect as the reason for fast ISC. In case of the selenium PDI derivative we found significant singlet oxygen sensitization via the PDI triplet state. The corresponding radical anions of the chalcogen substituted PDIs were also prepared and investigated by optical and EPR spectroscopy. Here, the increasing SOC results in an increase of the g-tensor anisotropy, and of the isotropic g-value in solution, albeit quasirelativistic density functional calculations show only a relatively small fraction of the spin density to be located on the chalcogen atom.
• Yellow Light-Emitting Highly Soluble Perylene Bisimide Dyes by Acetalization of Bay-Hydroxy Groups. Nagler, Oliver; Krause, Ana-Maria; Shoyama, Kazutaka; Stolte, Matthias; Dubey, Rajeev K.; Liu, Linlin; Xie, Zengqi; Würthner, Frank. In Org. Lett., 24(37), pp. 6839–6844. 2022.
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  A new class of perylene bisimide (PBI) derivatives is introduced by bridging 1,12- and 1,6,7,12-hydroxy functionalized bay positions with oxygen–carbon–oxygen linker(s). This functionalization rigidifies the inherently twisted bay-substituted perylene core to afford dyes of high stability and solubility that are characterized by vibronically well-resolved absorption and fluorescence spectra and intense yellow emission with quantum yields close to 100%.

  @article{Nagler_2022, abstract = {A new class of perylene bisimide (PBI) derivatives is introduced by bridging 1,12- and 1,6,7,12-hydroxy functionalized bay positions with oxygen–carbon–oxygen linker(s). This functionalization rigidifies the inherently twisted bay-substituted perylene core to afford dyes of high stability and solubility that are characterized by vibronically well-resolved absorption and fluorescence spectra and intense yellow emission with quantum yields close to 100%.}, author = {Nagler, Oliver and Krause, Ana-Maria and Shoyama, Kazutaka and Stolte, Matthias and Dubey, Rajeev K. and Liu, Linlin and Xie, Zengqi and Würthner, Frank}, journal = {Org. Lett.}, keywords = {myown}, month = {09}, number = 37, pages = {6839–6844}, publisher = {American Chemical Society ({ACS})}, title = {Yellow Light-Emitting Highly Soluble Perylene Bisimide Dyes by Acetalization of Bay-Hydroxy Groups}, volume = 24, year = 2022 }

  %0 Journal Article %1 Nagler_2022 %A Nagler, Oliver %A Krause, Ana-Maria %A Shoyama, Kazutaka %A Stolte, Matthias %A Dubey, Rajeev K. %A Liu, Linlin %A Xie, Zengqi %A Würthner, Frank %D 2022 %I American Chemical Society (ACS) %J Org. Lett. %N 37 %P 6839--6844 %R 10.1021/acs.orglett.2c02764 %T Yellow Light-Emitting Highly Soluble Perylene Bisimide Dyes by Acetalization of Bay-Hydroxy Groups %U https://doi.org/10.1021%2Facs.orglett.2c02764 %V 24 %X A new class of perylene bisimide (PBI) derivatives is introduced by bridging 1,12- and 1,6,7,12-hydroxy functionalized bay positions with oxygen–carbon–oxygen linker(s). This functionalization rigidifies the inherently twisted bay-substituted perylene core to afford dyes of high stability and solubility that are characterized by vibronically well-resolved absorption and fluorescence spectra and intense yellow emission with quantum yields close to 100%.
• Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling. Hong, Yongseok; Rudolf, Maximilian; Kim, Munnyon; Kim, Juno; Schembri, Tim; Krause, Ana-Maria; Shoyama, Kazutaka; Bialas, David; Röhr, Merle I. S.; Joo, Taiha; Kim, Hyungjun; Kim, Dongho; Würthner, Frank. In Nat. Commun., 13. 2022.
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  Dye arrays from dimers up to larger oligomers constitute the functional units of natural light harvesting systems as well as organic photonic and photovoltaic materials. Whilst in the past decades many photophysical studies were devoted to molecular dimers for deriving structure-property relationship to unravel the design principles for ideal optoelectronic materials, they fail to accomplish the subsequent processes of charge carrier generation or the detachment of two triplet species in singlet fission (SF). Here, we present a slip-stacked perylene bisimide trimer, which constitutes a bridge between hitherto studied dimer and solid-state materials, to investigate SF mechanisms. This work showcases multiple pathways towards the multiexciton state through direct or excimer-mediated mechanisms by depending upon interchromophoric interaction. These results suggest the comprehensive role of the exciton coupling, exciton delocalization, and excimer state to facilitate the SF process. In this regard, our observations expand the fundamental understanding the structure-property relationship in dye arrays.

  @article{hong2022steering, abstract = {Dye arrays from dimers up to larger oligomers constitute the functional units of natural light harvesting systems as well as organic photonic and photovoltaic materials. Whilst in the past decades many photophysical studies were devoted to molecular dimers for deriving structure-property relationship to unravel the design principles for ideal optoelectronic materials, they fail to accomplish the subsequent processes of charge carrier generation or the detachment of two triplet species in singlet fission (SF). Here, we present a slip-stacked perylene bisimide trimer, which constitutes a bridge between hitherto studied dimer and solid-state materials, to investigate SF mechanisms. This work showcases multiple pathways towards the multiexciton state through direct or excimer-mediated mechanisms by depending upon interchromophoric interaction. These results suggest the comprehensive role of the exciton coupling, exciton delocalization, and excimer state to facilitate the SF process. In this regard, our observations expand the fundamental understanding the structure-property relationship in dye arrays.}, author = {Hong, Yongseok and Rudolf, Maximilian and Kim, Munnyon and Kim, Juno and Schembri, Tim and Krause, Ana-Maria and Shoyama, Kazutaka and Bialas, David and Röhr, Merle I. S. and Joo, Taiha and Kim, Hyungjun and Kim, Dongho and Würthner, Frank}, journal = {Nat. Commun.}, keywords = {myown}, month = {08}, title = {Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling}, volume = 13, year = 2022 }

  %0 Journal Article %1 hong2022steering %A Hong, Yongseok %A Rudolf, Maximilian %A Kim, Munnyon %A Kim, Juno %A Schembri, Tim %A Krause, Ana-Maria %A Shoyama, Kazutaka %A Bialas, David %A Röhr, Merle I. S. %A Joo, Taiha %A Kim, Hyungjun %A Kim, Dongho %A Würthner, Frank %D 2022 %J Nat. Commun. %R 10.1038/s41467-022-31958-1 %T Steering the multiexciton generation in slip-stacked perylene dye array via exciton coupling %U https://www.nature.com/articles/s41467-022-31958-1 %V 13 %X Dye arrays from dimers up to larger oligomers constitute the functional units of natural light harvesting systems as well as organic photonic and photovoltaic materials. Whilst in the past decades many photophysical studies were devoted to molecular dimers for deriving structure-property relationship to unravel the design principles for ideal optoelectronic materials, they fail to accomplish the subsequent processes of charge carrier generation or the detachment of two triplet species in singlet fission (SF). Here, we present a slip-stacked perylene bisimide trimer, which constitutes a bridge between hitherto studied dimer and solid-state materials, to investigate SF mechanisms. This work showcases multiple pathways towards the multiexciton state through direct or excimer-mediated mechanisms by depending upon interchromophoric interaction. These results suggest the comprehensive role of the exciton coupling, exciton delocalization, and excimer state to facilitate the SF process. In this regard, our observations expand the fundamental understanding the structure-property relationship in dye arrays.
• Wavelength and Polarization Sensitive Synaptic Phototransistor Based on Organic n-type Semiconductor/Supramolecular J-Aggregate Heterostructure. Kim, Jin Hong; Stolte, Matthias; Würthner, Frank. In ACS Nano, 16(11), pp. 19523–19532. 2022.
  • [ Abstract ]
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  Human retina- and brain-inspired optoelectronic synapses, which integrate light detection and signal memory functions for data processing, have significant interest because of their potential applications for artificial vision technology. In nature, many animals such as mantis shrimp use polarized light information as well as scalar information including wavelength and intensity; however, a spectropolarimetric organic optoelectronic synapse has been seldom investigated. Herein, we report an organic synaptic phototransistor, consisting of a charge trapping liquid-crystalline perylene bisimide J-aggregate and a charge transporting crystalline dichlorinated naphthalene diimide, that can detect both wavelength and polarization information. The device shows persistent positive and negative photocurrents under low and high voltage conditions, respectively. Furthermore, the aligned organic heterostructure in the thin-film enables linearly polarized light to be absorbed with a dichroic ratio of 1.4 and 3.7 under transverse polarized blue and red light illumination, respectively. These features allow polarized light sensitive postsynaptic functions in the device. Consequently, a simple polarization imaging sensor array is successfully demonstrated using photonic synapses, which suggests that a supramolecular material is an important candidate for the development of spectropolarimetric neuromorphic vision systems.

  @article{Kim_2022, abstract = {Human retina- and brain-inspired optoelectronic synapses, which integrate light detection and signal memory functions for data processing, have significant interest because of their potential applications for artificial vision technology. In nature, many animals such as mantis shrimp use polarized light information as well as scalar information including wavelength and intensity; however, a spectropolarimetric organic optoelectronic synapse has been seldom investigated. Herein, we report an organic synaptic phototransistor, consisting of a charge trapping liquid-crystalline perylene bisimide J-aggregate and a charge transporting crystalline dichlorinated naphthalene diimide, that can detect both wavelength and polarization information. The device shows persistent positive and negative photocurrents under low and high voltage conditions, respectively. Furthermore, the aligned organic heterostructure in the thin-film enables linearly polarized light to be absorbed with a dichroic ratio of 1.4 and 3.7 under transverse polarized blue and red light illumination, respectively. These features allow polarized light sensitive postsynaptic functions in the device. Consequently, a simple polarization imaging sensor array is successfully demonstrated using photonic synapses, which suggests that a supramolecular material is an important candidate for the development of spectropolarimetric neuromorphic vision systems.}, author = {Kim, Jin Hong and Stolte, Matthias and Würthner, Frank}, journal = {ACS Nano}, keywords = {myown}, month = 11, number = 11, pages = {19523–19532}, publisher = {American Chemical Society (ACS)}, title = {Wavelength and Polarization Sensitive Synaptic Phototransistor Based on Organic n-type Semiconductor/Supramolecular J-Aggregate Heterostructure}, volume = 16, year = 2022 }

  %0 Journal Article %1 Kim_2022 %A Kim, Jin Hong %A Stolte, Matthias %A Würthner, Frank %D 2022 %I American Chemical Society (ACS) %J ACS Nano %N 11 %P 19523--19532 %R 10.1021/acsnano.2c09747 %T Wavelength and Polarization Sensitive Synaptic Phototransistor Based on Organic n-type Semiconductor/Supramolecular J-Aggregate Heterostructure %U https://doi.org/10.1021%2Facsnano.2c09747 %V 16 %X Human retina- and brain-inspired optoelectronic synapses, which integrate light detection and signal memory functions for data processing, have significant interest because of their potential applications for artificial vision technology. In nature, many animals such as mantis shrimp use polarized light information as well as scalar information including wavelength and intensity; however, a spectropolarimetric organic optoelectronic synapse has been seldom investigated. Herein, we report an organic synaptic phototransistor, consisting of a charge trapping liquid-crystalline perylene bisimide J-aggregate and a charge transporting crystalline dichlorinated naphthalene diimide, that can detect both wavelength and polarization information. The device shows persistent positive and negative photocurrents under low and high voltage conditions, respectively. Furthermore, the aligned organic heterostructure in the thin-film enables linearly polarized light to be absorbed with a dichroic ratio of 1.4 and 3.7 under transverse polarized blue and red light illumination, respectively. These features allow polarized light sensitive postsynaptic functions in the device. Consequently, a simple polarization imaging sensor array is successfully demonstrated using photonic synapses, which suggests that a supramolecular material is an important candidate for the development of spectropolarimetric neuromorphic vision systems.
• pi-Extended Pleiadienes by [5+2] Annulation of 1-Boraphenalenes and ortho-Dihaloarenes. Schnitzlein, Matthias; Zhu, Chongwei; Shoyama, Kazutaka; Würthner, Frank. In Chemistry - A European Journal. 2022.
  • [ Abstract ]
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  Palladium-catalyzed [5+2] annulation of 1-boraphenalenes with ortho-dihaloarenes afforded negatively curved π-extended pleiadienes. Two benzo[1,2-i:4,5-i’]dipleiadienes (BDPs) featuring a seven-six-seven-membered ring arrangement were synthesized and investigated. Their crystal structure revealed a unique packing arrangement and theoretical calculations were employed to shed light onto the dynamic behavior of the BDP moiety and its aromaticity. Further, a naphthalene-fused pleiadiene was stitched together by oxidative cyclodehydrogenation to yield an additional five-membered ring. This formal azulene moiety led to distinct changes in optical and redox properties and increased perturbation of the aromatic system.

  @article{Schnitzlein_2022, abstract = {Palladium-catalyzed [5+2] annulation of 1-boraphenalenes with ortho-dihaloarenes afforded negatively curved π-extended pleiadienes. Two benzo[1,2-i:4,5-i’]dipleiadienes (BDPs) featuring a seven-six-seven-membered ring arrangement were synthesized and investigated. Their crystal structure revealed a unique packing arrangement and theoretical calculations were employed to shed light onto the dynamic behavior of the BDP moiety and its aromaticity. Further, a naphthalene-fused pleiadiene was stitched together by oxidative cyclodehydrogenation to yield an additional five-membered ring. This formal azulene moiety led to distinct changes in optical and redox properties and increased perturbation of the aromatic system.}, author = {Schnitzlein, Matthias and Zhu, Chongwei and Shoyama, Kazutaka and Würthner, Frank}, journal = {Chemistry - A European Journal}, keywords = {myown}, month = {08}, publisher = {Wiley}, title = {pi-Extended Pleiadienes by [5+2] Annulation of 1-Boraphenalenes and ortho-Dihaloarenes}, year = 2022 }

  %0 Journal Article %1 Schnitzlein_2022 %A Schnitzlein, Matthias %A Zhu, Chongwei %A Shoyama, Kazutaka %A Würthner, Frank %D 2022 %I Wiley %J Chemistry - A European Journal %R 10.1002/chem.202202053 %T pi-Extended Pleiadienes by [5+2] Annulation of 1-Boraphenalenes and ortho-Dihaloarenes %U https://doi.org/10.1002%2Fchem.202202053 %X Palladium-catalyzed [5+2] annulation of 1-boraphenalenes with ortho-dihaloarenes afforded negatively curved π-extended pleiadienes. Two benzo[1,2-i:4,5-i’]dipleiadienes (BDPs) featuring a seven-six-seven-membered ring arrangement were synthesized and investigated. Their crystal structure revealed a unique packing arrangement and theoretical calculations were employed to shed light onto the dynamic behavior of the BDP moiety and its aromaticity. Further, a naphthalene-fused pleiadiene was stitched together by oxidative cyclodehydrogenation to yield an additional five-membered ring. This formal azulene moiety led to distinct changes in optical and redox properties and increased perturbation of the aromatic system.
• Self-assembled Ru(bda) Coordination Oligomers as Efficient Catalysts for Visible Light-Driven Water Oxidation in Pure Water. Schlossarek, Tim; Stepanenko, Vladimir; Beuerle, Florian; Würthner, Frank. In Angewandte Chemie International Edition, 61(52). 2022.
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  Water-soluble multinuclear complexes based on ruthenium 2,2′-bipyridine-6,6′-dicarboxylate (bda) and ditopic bipyridine linker units are investigated in three-component visible light-driven water oxidation catalysis. Systematic studies revealed a strong enhancement of the catalytic efficiency in the absence of organic co-solvents and with increasing oligomer length. In-depth kinetic and morphological investigations suggest that the enhanced performance is induced by the self-assembly of linear Ru(bda) oligomers into aggregated superstructures. The obtained turnover frequencies (up to 14.9 s−1) and turnover numbers (more than 1000) per ruthenium center are the highest reported so far for Ru(bda)-based photocatalytic water oxidation systems.

  @article{Schlossarek_2022, abstract = {Water-soluble multinuclear complexes based on ruthenium 2,2′-bipyridine-6,6′-dicarboxylate (bda) and ditopic bipyridine linker units are investigated in three-component visible light-driven water oxidation catalysis. Systematic studies revealed a strong enhancement of the catalytic efficiency in the absence of organic co-solvents and with increasing oligomer length. In-depth kinetic and morphological investigations suggest that the enhanced performance is induced by the self-assembly of linear Ru(bda) oligomers into aggregated superstructures. The obtained turnover frequencies (up to 14.9 s−1) and turnover numbers (more than 1000) per ruthenium center are the highest reported so far for Ru(bda)-based photocatalytic water oxidation systems.}, author = {Schlossarek, Tim and Stepanenko, Vladimir and Beuerle, Florian and Würthner, Frank}, journal = {Angewandte Chemie International Edition}, keywords = {myown}, month = 11, number = 52, publisher = {Wiley}, title = {Self-assembled Ru(bda) Coordination Oligomers as Efficient Catalysts for Visible Light-Driven Water Oxidation in Pure Water}, volume = 61, year = 2022 }

  %0 Journal Article %1 Schlossarek_2022 %A Schlossarek, Tim %A Stepanenko, Vladimir %A Beuerle, Florian %A Würthner, Frank %D 2022 %I Wiley %J Angewandte Chemie International Edition %N 52 %R 10.1002/anie.202211445 %T Self-assembled Ru(bda) Coordination Oligomers as Efficient Catalysts for Visible Light-Driven Water Oxidation in Pure Water %U https://doi.org/10.1002%2Fanie.202211445 %V 61 %X Water-soluble multinuclear complexes based on ruthenium 2,2′-bipyridine-6,6′-dicarboxylate (bda) and ditopic bipyridine linker units are investigated in three-component visible light-driven water oxidation catalysis. Systematic studies revealed a strong enhancement of the catalytic efficiency in the absence of organic co-solvents and with increasing oligomer length. In-depth kinetic and morphological investigations suggest that the enhanced performance is induced by the self-assembly of linear Ru(bda) oligomers into aggregated superstructures. The obtained turnover frequencies (up to 14.9 s−1) and turnover numbers (more than 1000) per ruthenium center are the highest reported so far for Ru(bda)-based photocatalytic water oxidation systems.
• Substituent-dependent absorption and fluorescence properties of perylene bisimide radical anions and dianions. Renner, Rebecca; Stolte, Matthias; Heitmüller, Julia; Brixner, Tobias; Lambert, Christoph; Würthner, Frank. In Mater. Horiz., 9(1), pp. 350–359. 2022.

  Original data of the UV-Vis-NIR and fluorescence spectra: DOI 10.5281/zenodo.5849111
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  Perylene-3,4:9,10-bis(dicarboximides) (PBIs) rank among the most important functional dyes and organic semiconductors, but only recently have their radical anions and dianions attracted interest for a variety of applications. Here, we systematically elucidate the functional properties (redox, absorption, and emission) of five PBI anions and dianions bearing different bay-substituents attached to the chromophore core. Cyclic voltammetry measurements reveal the influence of the substituents ranging from electron-withdrawing cyano to electron-donating phenoxy groups on the oxidation and reduction potentials that relate to the HOMO and LUMO levels ranging from −7.07 eV to −6.05 eV and −5.01 eV to −4.05 eV, respectively. Spectroelectrochemical studies reveal a significant number of intense absorption bands in the NIR-spectral range (750–1400 nm) for the radical anions, whereas the dianionic species are characterized by similar spectra to those for the neutral dyes, however being bathochromically shifted and with increased molar extinction coefficients of approximately 100 000 M−1 cm−1. The increase of the transition dipole moment is up to 56% and accompanied by an almost cyanine-like red-shifted (by 300 nm) absorption spectrum for the most electron-poor tetracyanotetrachloro PBI. Whilst the outstanding fluorescence properties of the neutral PBIs are lost for the radical anions, an appreciable near-infrared (NIR) fluorescence with a quantum yield of up to 18% is revealed for the dianions by utilizing a custom-built flow-cell spectroelectrochemistry setup. Time-dependent density functional theory calculations help to assign the absorption bands to the respective electronic transitions.

  @article{D1MH01019K, abstract = {Perylene-3,4:9,10-bis(dicarboximides) (PBIs) rank among the most important functional dyes and organic semiconductors, but only recently have their radical anions and dianions attracted interest for a variety of applications. Here, we systematically elucidate the functional properties (redox, absorption, and emission) of five PBI anions and dianions bearing different bay-substituents attached to the chromophore core. Cyclic voltammetry measurements reveal the influence of the substituents ranging from electron-withdrawing cyano to electron-donating phenoxy groups on the oxidation and reduction potentials that relate to the HOMO and LUMO levels ranging from −7.07 eV to −6.05 eV and −5.01 eV to −4.05 eV, respectively. Spectroelectrochemical studies reveal a significant number of intense absorption bands in the NIR-spectral range (750–1400 nm) for the radical anions, whereas the dianionic species are characterized by similar spectra to those for the neutral dyes, however being bathochromically shifted and with increased molar extinction coefficients of approximately 100 000 M−1 cm−1. The increase of the transition dipole moment is up to 56% and accompanied by an almost cyanine-like red-shifted (by 300 nm) absorption spectrum for the most electron-poor tetracyanotetrachloro PBI. Whilst the outstanding fluorescence properties of the neutral PBIs are lost for the radical anions, an appreciable near-infrared (NIR) fluorescence with a quantum yield of up to 18% is revealed for the dianions by utilizing a custom-built flow-cell spectroelectrochemistry setup. Time-dependent density functional theory calculations help to assign the absorption bands to the respective electronic transitions.}, author = {Renner, Rebecca and Stolte, Matthias and Heitmüller, Julia and Brixner, Tobias and Lambert, Christoph and Würthner, Frank}, journal = {Mater. Horiz.}, keywords = {myown}, note = {Original data of the UV-Vis-NIR and fluorescence spectra: DOI 10.5281/zenodo.5849111}, number = 1, pages = {350-359}, publisher = {The Royal Society of Chemistry}, title = {Substituent-dependent absorption and fluorescence properties of perylene bisimide radical anions and dianions}, volume = 9, year = 2022 }

  %0 Journal Article %1 D1MH01019K %A Renner, Rebecca %A Stolte, Matthias %A Heitmüller, Julia %A Brixner, Tobias %A Lambert, Christoph %A Würthner, Frank %D 2022 %I The Royal Society of Chemistry %J Mater. Horiz. %N 1 %P 350-359 %R 10.1039/D1MH01019K %T Substituent-dependent absorption and fluorescence properties of perylene bisimide radical anions and dianions %U http://dx.doi.org/10.1039/D1MH01019K %V 9 %X Perylene-3,4:9,10-bis(dicarboximides) (PBIs) rank among the most important functional dyes and organic semiconductors, but only recently have their radical anions and dianions attracted interest for a variety of applications. Here, we systematically elucidate the functional properties (redox, absorption, and emission) of five PBI anions and dianions bearing different bay-substituents attached to the chromophore core. Cyclic voltammetry measurements reveal the influence of the substituents ranging from electron-withdrawing cyano to electron-donating phenoxy groups on the oxidation and reduction potentials that relate to the HOMO and LUMO levels ranging from −7.07 eV to −6.05 eV and −5.01 eV to −4.05 eV, respectively. Spectroelectrochemical studies reveal a significant number of intense absorption bands in the NIR-spectral range (750–1400 nm) for the radical anions, whereas the dianionic species are characterized by similar spectra to those for the neutral dyes, however being bathochromically shifted and with increased molar extinction coefficients of approximately 100 000 M−1 cm−1. The increase of the transition dipole moment is up to 56% and accompanied by an almost cyanine-like red-shifted (by 300 nm) absorption spectrum for the most electron-poor tetracyanotetrachloro PBI. Whilst the outstanding fluorescence properties of the neutral PBIs are lost for the radical anions, an appreciable near-infrared (NIR) fluorescence with a quantum yield of up to 18% is revealed for the dianions by utilizing a custom-built flow-cell spectroelectrochemistry setup. Time-dependent density functional theory calculations help to assign the absorption bands to the respective electronic transitions.

• Structure-Activity Relationship for Di- up to Tetranuclear Macrocyclic Ruthenium Catalysts in Homogeneous Water Oxidation. Schindler, Dorothee; Meza-Chincha, Ana-Lucia; Roth, Maximilian; Würthner, Frank. In Chemistry – A European Journal, 27(68), pp. 16938–16946. 2021.
  • [ Abstract ]
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  Two di- and tetranuclear Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylate) macrocyclic complexes were synthesized and their catalytic activities in chemical and photochemical water oxidation investigated in a comparative manner to our previously reported trinuclear congener. Our studies have shown that the catalytic activities of this homologous series of multinuclear Ru(bda) macrocycles in homogeneous water oxidation are dependent on their size, exhibiting highest efficiencies for the largest tetranuclear catalyst. The turnover frequencies (TOFs) have increased from di- to tetranuclear macrocycles not only per catalyst molecule but more importantly also per Ru unit with TOF of 6 s−1 to 8.7 s−1 and 10.5 s−1 in chemical and 0.6 s−1 to 3.3 s−1 and 5.8 s−1 in photochemical water oxidation per Ru unit, respectively. Thus, for the first time, a clear structure–activity relationship could be established for this novel class of macrocyclic water oxidation catalysts.

  @article{Schindler_2021, abstract = {Two di- and tetranuclear Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylate) macrocyclic complexes were synthesized and their catalytic activities in chemical and photochemical water oxidation investigated in a comparative manner to our previously reported trinuclear congener. Our studies have shown that the catalytic activities of this homologous series of multinuclear Ru(bda) macrocycles in homogeneous water oxidation are dependent on their size, exhibiting highest efficiencies for the largest tetranuclear catalyst. The turnover frequencies (TOFs) have increased from di- to tetranuclear macrocycles not only per catalyst molecule but more importantly also per Ru unit with TOF of 6 s−1 to 8.7 s−1 and 10.5 s−1 in chemical and 0.6 s−1 to 3.3 s−1 and 5.8 s−1 in photochemical water oxidation per Ru unit, respectively. Thus, for the first time, a clear structure–activity relationship could be established for this novel class of macrocyclic water oxidation catalysts.}, author = {Schindler, Dorothee and Meza-Chincha, Ana-Lucia and Roth, Maximilian and Würthner, Frank}, journal = {Chemistry – A European Journal}, keywords = {myown}, month = {05}, number = 68, pages = {16938–16946}, publisher = {Wiley}, title = {Structure-Activity Relationship for Di- up to Tetranuclear Macrocyclic Ruthenium Catalysts in Homogeneous Water Oxidation}, volume = 27, year = 2021 }

  %0 Journal Article %1 Schindler_2021 %A Schindler, Dorothee %A Meza-Chincha, Ana-Lucia %A Roth, Maximilian %A Würthner, Frank %D 2021 %I Wiley %J Chemistry – A European Journal %N 68 %P 16938--16946 %R 10.1002/chem.202100549 %T Structure-Activity Relationship for Di- up to Tetranuclear Macrocyclic Ruthenium Catalysts in Homogeneous Water Oxidation %U https://doi.org/10.1002%2Fchem.202100549 %V 27 %X Two di- and tetranuclear Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylate) macrocyclic complexes were synthesized and their catalytic activities in chemical and photochemical water oxidation investigated in a comparative manner to our previously reported trinuclear congener. Our studies have shown that the catalytic activities of this homologous series of multinuclear Ru(bda) macrocycles in homogeneous water oxidation are dependent on their size, exhibiting highest efficiencies for the largest tetranuclear catalyst. The turnover frequencies (TOFs) have increased from di- to tetranuclear macrocycles not only per catalyst molecule but more importantly also per Ru unit with TOF of 6 s−1 to 8.7 s−1 and 10.5 s−1 in chemical and 0.6 s−1 to 3.3 s−1 and 5.8 s−1 in photochemical water oxidation per Ru unit, respectively. Thus, for the first time, a clear structure–activity relationship could be established for this novel class of macrocyclic water oxidation catalysts.
• Polymorphism in Squaraine Dye Aggregates by Self-Assembly Pathway Differentiation: Panchromatic Tubular Dye Nanorods versus J-Aggregate Nanosheets. Shen, Chia-An; Bialas, David; Hecht, Markus; Stepanenko, Vladimir; Sugiyasu, Kazunori; Würthner, Frank. In Angew. Chem. Int. Ed., 60(21), pp. 11949–11958. 2021.
  • [ Abstract ]
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  A bis(squaraine) dye equipped with alkyl and oligoethyleneglycol chains was synthesized by connecting two dicyanomethylene substituted squaraine dyes with a phenylene spacer unit. The aggregation behavior of this bis(squaraine) was investigated in non‐polar toluene/tetrachloroethane (98:2) solvent mixture, which revealed competing cooperative self‐assembly pathways into two supramolecular polymorphs with entirely different packing structures and UV/Vis/NIR absorption properties. The self‐assembly pathway can be controlled by the cooling rate from a heated solution of the monomers. For both polymorphs, quasi‐equilibrium conditions between monomers and the respective aggregates can be established to derive thermodynamic parameters and insights into the self‐assembly mechanisms. AFM measurements revealed a nanosheet structure with a height of 2 nm for the thermodynamically more stable polymorph and a tubular nanorod structure with a helical pitch of 13 nm and a diameter of 5 nm for the kinetically favored polymorph. Together with wide angle X‐ray scattering measurements, packing models were derived: the thermodynamic polymorph consists of brick‐work type nanosheets that exhibit red‐shifted absorption bands as typical for J‐aggregates, while the nanorod polymorph consists of eight supramolecular polymer strands of the bis(squaraine) intertwined to form a chimney‐type tubular structure. The absorption of this aggregate covers a large spectral range from 550 to 875 nm, which cannot be rationalized by the conventional exciton theory. By applying the Essential States Model and considering intermolecular charge transfer, the aggregate spectrum was adequately reproduced, revealing that the broad absorption spectrum is due to pronounced donor‐acceptor overlap within the bis(squaraine) nanorods. The latter is also responsible for the pronounced bathochromic shift observed for the nanosheet structure as a result of the slip‐stacked arranged squaraine chromophores.

  @article{Shen_2021, abstract = {A bis(squaraine) dye equipped with alkyl and oligoethyleneglycol chains was synthesized by connecting two dicyanomethylene substituted squaraine dyes with a phenylene spacer unit. The aggregation behavior of this bis(squaraine) was investigated in non‐polar toluene/tetrachloroethane (98:2) solvent mixture, which revealed competing cooperative self‐assembly pathways into two supramolecular polymorphs with entirely different packing structures and UV/Vis/NIR absorption properties. The self‐assembly pathway can be controlled by the cooling rate from a heated solution of the monomers. For both polymorphs, quasi‐equilibrium conditions between monomers and the respective aggregates can be established to derive thermodynamic parameters and insights into the self‐assembly mechanisms. AFM measurements revealed a nanosheet structure with a height of 2 nm for the thermodynamically more stable polymorph and a tubular nanorod structure with a helical pitch of 13 nm and a diameter of 5 nm for the kinetically favored polymorph. Together with wide angle X‐ray scattering measurements, packing models were derived: the thermodynamic polymorph consists of brick‐work type nanosheets that exhibit red‐shifted absorption bands as typical for J‐aggregates, while the nanorod polymorph consists of eight supramolecular polymer strands of the bis(squaraine) intertwined to form a chimney‐type tubular structure. The absorption of this aggregate covers a large spectral range from 550 to 875 nm, which cannot be rationalized by the conventional exciton theory. By applying the Essential States Model and considering intermolecular charge transfer, the aggregate spectrum was adequately reproduced, revealing that the broad absorption spectrum is due to pronounced donor‐acceptor overlap within the bis(squaraine) nanorods. The latter is also responsible for the pronounced bathochromic shift observed for the nanosheet structure as a result of the slip‐stacked arranged squaraine chromophores.}, author = {Shen, Chia-An and Bialas, David and Hecht, Markus and Stepanenko, Vladimir and Sugiyasu, Kazunori and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {05}, number = 21, pages = {11949–11958}, publisher = {Wiley}, title = {Polymorphism in Squaraine Dye Aggregates by Self-Assembly Pathway Differentiation: Panchromatic Tubular Dye Nanorods versus J-Aggregate Nanosheets}, volume = 60, year = 2021 }

  %0 Journal Article %1 Shen_2021 %A Shen, Chia-An %A Bialas, David %A Hecht, Markus %A Stepanenko, Vladimir %A Sugiyasu, Kazunori %A Würthner, Frank %D 2021 %I Wiley %J Angew. Chem. Int. Ed. %N 21 %P 11949--11958 %R 10.1002/anie.202102183 %T Polymorphism in Squaraine Dye Aggregates by Self-Assembly Pathway Differentiation: Panchromatic Tubular Dye Nanorods versus J-Aggregate Nanosheets %U https://doi.org/10.1002%2Fanie.202102183 %V 60 %X A bis(squaraine) dye equipped with alkyl and oligoethyleneglycol chains was synthesized by connecting two dicyanomethylene substituted squaraine dyes with a phenylene spacer unit. The aggregation behavior of this bis(squaraine) was investigated in non‐polar toluene/tetrachloroethane (98:2) solvent mixture, which revealed competing cooperative self‐assembly pathways into two supramolecular polymorphs with entirely different packing structures and UV/Vis/NIR absorption properties. The self‐assembly pathway can be controlled by the cooling rate from a heated solution of the monomers. For both polymorphs, quasi‐equilibrium conditions between monomers and the respective aggregates can be established to derive thermodynamic parameters and insights into the self‐assembly mechanisms. AFM measurements revealed a nanosheet structure with a height of 2 nm for the thermodynamically more stable polymorph and a tubular nanorod structure with a helical pitch of 13 nm and a diameter of 5 nm for the kinetically favored polymorph. Together with wide angle X‐ray scattering measurements, packing models were derived: the thermodynamic polymorph consists of brick‐work type nanosheets that exhibit red‐shifted absorption bands as typical for J‐aggregates, while the nanorod polymorph consists of eight supramolecular polymer strands of the bis(squaraine) intertwined to form a chimney‐type tubular structure. The absorption of this aggregate covers a large spectral range from 550 to 875 nm, which cannot be rationalized by the conventional exciton theory. By applying the Essential States Model and considering intermolecular charge transfer, the aggregate spectrum was adequately reproduced, revealing that the broad absorption spectrum is due to pronounced donor‐acceptor overlap within the bis(squaraine) nanorods. The latter is also responsible for the pronounced bathochromic shift observed for the nanosheet structure as a result of the slip‐stacked arranged squaraine chromophores.
• Site-specific chemical doping reveals electron atmospheres at the surfaces of organic semiconductor crystals. He, Tao; Stolte, Matthias; Wang, Yan; Renner, Rebecca; Ruden, P. Paul; Würthner, Frank; Frisbie, C. Daniel. In Nature Materials, 20(11), pp. 1532–1538. 2021.
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  Chemical doping controls the electronic properties of organic semiconductors, but so far, doping protocols and mechanisms are less developed than in conventional semiconductors. Here we describe a unique, site-specific, n-type surface doping mecha- nism for single crystals of two benchmark organic semiconductors that produces dramatic improvement in electron transport and provides unprecedented evidence for doping-induced space charge. The surface doping chemistry specifically targets crys- tallographic step edges, which are known electron traps, simultaneously passivating the traps and releasing itinerant elec- trons. The effect on electron transport is profound: field-effect electron mobility increases by as much as a factor of ten, and its temperature-dependent behaviour switches from thermally activated to band-like. Our findings suggest new site-specific strategies to dope organic semiconductors that differ from the conventional redox chemistry of randomly distributed substi- tutional impurities. Critically, they also verify the presence of doping-induced electron atmospheres, confirming long-standing expectations for organic systems from conventional solid-state theory.

  @article{He_2021, abstract = {Chemical doping controls the electronic properties of organic semiconductors, but so far, doping protocols and mechanisms are less developed than in conventional semiconductors. Here we describe a unique, site-specific, n-type surface doping mecha- nism for single crystals of two benchmark organic semiconductors that produces dramatic improvement in electron transport and provides unprecedented evidence for doping-induced space charge. The surface doping chemistry specifically targets crys- tallographic step edges, which are known electron traps, simultaneously passivating the traps and releasing itinerant elec- trons. The effect on electron transport is profound: field-effect electron mobility increases by as much as a factor of ten, and its temperature-dependent behaviour switches from thermally activated to band-like. Our findings suggest new site-specific strategies to dope organic semiconductors that differ from the conventional redox chemistry of randomly distributed substi- tutional impurities. Critically, they also verify the presence of doping-induced electron atmospheres, confirming long-standing expectations for organic systems from conventional solid-state theory.}, author = {He, Tao and Stolte, Matthias and Wang, Yan and Renner, Rebecca and Ruden, P. Paul and Würthner, Frank and Frisbie, C. Daniel}, journal = {Nature Materials}, keywords = {myown}, month = {08}, number = 11, pages = {1532–1538}, publisher = {Springer Science and Business Media {LLC}}, title = {Site-specific chemical doping reveals electron atmospheres at the surfaces of organic semiconductor crystals}, volume = 20, year = 2021 }

  %0 Journal Article %1 He_2021 %A He, Tao %A Stolte, Matthias %A Wang, Yan %A Renner, Rebecca %A Ruden, P. Paul %A Würthner, Frank %A Frisbie, C. Daniel %D 2021 %I Springer Science and Business Media LLC %J Nature Materials %N 11 %P 1532--1538 %R 10.1038/s41563-021-01079-z %T Site-specific chemical doping reveals electron atmospheres at the surfaces of organic semiconductor crystals %U https://doi.org/10.1038%2Fs41563-021-01079-z %V 20 %X Chemical doping controls the electronic properties of organic semiconductors, but so far, doping protocols and mechanisms are less developed than in conventional semiconductors. Here we describe a unique, site-specific, n-type surface doping mecha- nism for single crystals of two benchmark organic semiconductors that produces dramatic improvement in electron transport and provides unprecedented evidence for doping-induced space charge. The surface doping chemistry specifically targets crys- tallographic step edges, which are known electron traps, simultaneously passivating the traps and releasing itinerant elec- trons. The effect on electron transport is profound: field-effect electron mobility increases by as much as a factor of ten, and its temperature-dependent behaviour switches from thermally activated to band-like. Our findings suggest new site-specific strategies to dope organic semiconductors that differ from the conventional redox chemistry of randomly distributed substi- tutional impurities. Critically, they also verify the presence of doping-induced electron atmospheres, confirming long-standing expectations for organic systems from conventional solid-state theory.
• Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates. Kang, Seongsoo; Kim, Taeyeon; Hong, Yongseok; Würthner, Frank; Kim, Dongho. In J. Am. Chem. Soc., 143(26), pp. 9825–9833. 2021.
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  Herein, the ultrafast photoinduced dynamics and vibrational coherences for two perylenebisimide (PBI) H-aggregates showcase the formation of the excimer state and the delocalized radical anion state in the excited state, respectively. Using femtosecond transient absorption (fs-TA) and time-resolved impulsive stimulated Raman scattering (TR-ISRS) measurements, we unveiled excited-state dynamics of PBI H-aggregates in two aspects: (1) the intermolecular interactions between PBI units in H-aggregates induce the formation of new excited states, excimer and delocalized radical anion states, and (2) the intermolecular out-of-plane along the aggregate axis and the PBI core C═C stretch Raman modes can be a crucial indicator to understand the coherent exciton dynamics in H-aggregates. Notably, those excited-state Raman modes showed stationary peak positions during the excited-state dynamics. TR-ISRS analysis provides insights into the excited-state vibrational coherences concerning the formation of the excimer and charge-delocalized state in each aggregate system.

  @article{Kang_2021, abstract = {Herein, the ultrafast photoinduced dynamics and vibrational coherences for two perylenebisimide (PBI) H-aggregates showcase the formation of the excimer state and the delocalized radical anion state in the excited state, respectively. Using femtosecond transient absorption (fs-TA) and time-resolved impulsive stimulated Raman scattering (TR-ISRS) measurements, we unveiled excited-state dynamics of PBI H-aggregates in two aspects: (1) the intermolecular interactions between PBI units in H-aggregates induce the formation of new excited states, excimer and delocalized radical anion states, and (2) the intermolecular out-of-plane along the aggregate axis and the PBI core C═C stretch Raman modes can be a crucial indicator to understand the coherent exciton dynamics in H-aggregates. Notably, those excited-state Raman modes showed stationary peak positions during the excited-state dynamics. TR-ISRS analysis provides insights into the excited-state vibrational coherences concerning the formation of the excimer and charge-delocalized state in each aggregate system.}, author = {Kang, Seongsoo and Kim, Taeyeon and Hong, Yongseok and Würthner, Frank and Kim, Dongho}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {06}, number = 26, pages = {9825–9833}, publisher = {American Chemical Society ({ACS})}, title = {Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates}, volume = 143, year = 2021 }

  %0 Journal Article %1 Kang_2021 %A Kang, Seongsoo %A Kim, Taeyeon %A Hong, Yongseok %A Würthner, Frank %A Kim, Dongho %D 2021 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 26 %P 9825--9833 %R 10.1021/jacs.1c03276 %T Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates %U https://doi.org/10.1021%2Fjacs.1c03276 %V 143 %X Herein, the ultrafast photoinduced dynamics and vibrational coherences for two perylenebisimide (PBI) H-aggregates showcase the formation of the excimer state and the delocalized radical anion state in the excited state, respectively. Using femtosecond transient absorption (fs-TA) and time-resolved impulsive stimulated Raman scattering (TR-ISRS) measurements, we unveiled excited-state dynamics of PBI H-aggregates in two aspects: (1) the intermolecular interactions between PBI units in H-aggregates induce the formation of new excited states, excimer and delocalized radical anion states, and (2) the intermolecular out-of-plane along the aggregate axis and the PBI core C═C stretch Raman modes can be a crucial indicator to understand the coherent exciton dynamics in H-aggregates. Notably, those excited-state Raman modes showed stationary peak positions during the excited-state dynamics. TR-ISRS analysis provides insights into the excited-state vibrational coherences concerning the formation of the excimer and charge-delocalized state in each aggregate system.
• Solvent Effects in Supramolecular Chemistry: Linear Free Energy Relationships for Common Intermolecular Interactions. Würthner, Frank. In J. Org. Chem, 87(3), pp. 1602–1615. 2021.
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  The proper choice of solvent is of major importance for all studies in supramolecular chemistry, including molecular recognition in host−guest systems, intramolecular folding, self-assembly, and supramolecular polymerization. In this Perspective, the usefulness of linear free energy relationships (LFERs) is highlighted to unravel the effect of solvents on coordinate bonding (e.g., cation- crown ether), hydrogen bonding, halogen bonding, dipolar aggregation, and π−π- stacking. For all of these intermolecular interactions widely applied in supramolecular systems, LFER relationships between the Gibbs binding energies and common solvent polarity scales including ET(30), π*, α or β based on solvatochromic dyes, scales derived from binding processes such as Gutmann donor and acceptor numbers or hydrogen bond donor and acceptor scales, or physical functions like the Kirkwood−Onsager or the Liptay−Onsager functions could be demonstrated. These relationships can now be applied toward a better understanding of the prevailing intermolecular forces for supramolecular interactions. They further enable a rational selection of the most suitable solvent for the preparation of self-assembled materials and the estimation of binding constants without the need for time-consuming comprehensive investigations of solvents.

  @article{W_rthner_2021, abstract = {The proper choice of solvent is of major importance for all studies in supramolecular chemistry, including molecular recognition in host−guest systems, intramolecular folding, self-assembly, and supramolecular polymerization. In this Perspective, the usefulness of linear free energy relationships (LFERs) is highlighted to unravel the effect of solvents on coordinate bonding (e.g., cation- crown ether), hydrogen bonding, halogen bonding, dipolar aggregation, and π−π- stacking. For all of these intermolecular interactions widely applied in supramolecular systems, LFER relationships between the Gibbs binding energies and common solvent polarity scales including ET(30), π*, α or β based on solvatochromic dyes, scales derived from binding processes such as Gutmann donor and acceptor numbers or hydrogen bond donor and acceptor scales, or physical functions like the Kirkwood−Onsager or the Liptay−Onsager functions could be demonstrated. These relationships can now be applied toward a better understanding of the prevailing intermolecular forces for supramolecular interactions. They further enable a rational selection of the most suitable solvent for the preparation of self-assembled materials and the estimation of binding constants without the need for time-consuming comprehensive investigations of solvents.}, author = {Würthner, Frank}, journal = {J. Org. Chem}, keywords = {myown}, month = {05}, number = 3, pages = {1602–1615}, publisher = {American Chemical Society ({ACS})}, title = {Solvent Effects in Supramolecular Chemistry: Linear Free Energy Relationships for Common Intermolecular Interactions}, volume = 87, year = 2021 }

  %0 Journal Article %1 W_rthner_2021 %A Würthner, Frank %D 2021 %I American Chemical Society (ACS) %J J. Org. Chem %N 3 %P 1602--1615 %R 10.1021/acs.joc.1c00625 %T Solvent Effects in Supramolecular Chemistry: Linear Free Energy Relationships for Common Intermolecular Interactions %U https://doi.org/10.1021%2Facs.joc.1c00625 %V 87 %X The proper choice of solvent is of major importance for all studies in supramolecular chemistry, including molecular recognition in host−guest systems, intramolecular folding, self-assembly, and supramolecular polymerization. In this Perspective, the usefulness of linear free energy relationships (LFERs) is highlighted to unravel the effect of solvents on coordinate bonding (e.g., cation- crown ether), hydrogen bonding, halogen bonding, dipolar aggregation, and π−π- stacking. For all of these intermolecular interactions widely applied in supramolecular systems, LFER relationships between the Gibbs binding energies and common solvent polarity scales including ET(30), π*, α or β based on solvatochromic dyes, scales derived from binding processes such as Gutmann donor and acceptor numbers or hydrogen bond donor and acceptor scales, or physical functions like the Kirkwood−Onsager or the Liptay−Onsager functions could be demonstrated. These relationships can now be applied toward a better understanding of the prevailing intermolecular forces for supramolecular interactions. They further enable a rational selection of the most suitable solvent for the preparation of self-assembled materials and the estimation of binding constants without the need for time-consuming comprehensive investigations of solvents.
• Nitronyl Nitroxide Bifunctionalized Electron-Poor Chromophores: Synthesis of Stable Dye Biradicals by Lewis Acid Promoted Desilylation. Rausch, Rodger; Krause, Ana-Maria; Krummenacher, Ivo; Braunschweig, Holger; Würthner, Frank. In J. Org. Chem., 86(3), pp. 2447–2457. 2021.
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  Open shell organic molecules bearing π-cores are of great interest for optical, electronic, and magnetic applications but frequently suffer fast decomposition or lack synthetic accessibility. In this regard, nitronyl nitroxides are promising candidates for stable (bi-)radicals due to their high degree of spin delocalization along the O–N–C–N–O pentad unit. Unfortunately, they are limited to electron-rich systems so far. To overcome this limitation, we developed a synthetic procedure for the twofold spin decoration of electron-poor chromophores (Ered = −1158 mV) with nitronyl nitroxide radical moieties via selective deprotection/oxidation of the respective silylated precursors with boron fluoride and subsequent quenching with tetraethyl orthosilicate. Nitronyl nitroxide biradicals PBI–NN, IIn–NN, PhDPP–NN, ThDPP–NN, and FuDPP–NN bridged by perylene bisimide (PBI), isoindigo (IIn), and diketopyrrolopyrrole (DPP) pigment colorants were finally obtained as bench stable compounds after periodate oxidation with yields of 60–81%. The absorption spectral signatures of the chromophores remain preserved in the open shell state and match the ones of the pristine parent compounds, which allowed an a priori prediction of their optical properties. Consequently, we achieved twofold spin labeling while keeping the intrinsic properties of the electron deficient chromophores intact.

  @article{Rausch_2021, abstract = {Open shell organic molecules bearing π-cores are of great interest for optical, electronic, and magnetic applications but frequently suffer fast decomposition or lack synthetic accessibility. In this regard, nitronyl nitroxides are promising candidates for stable (bi-)radicals due to their high degree of spin delocalization along the O–N–C–N–O pentad unit. Unfortunately, they are limited to electron-rich systems so far. To overcome this limitation, we developed a synthetic procedure for the twofold spin decoration of electron-poor chromophores (Ered = −1158 mV) with nitronyl nitroxide radical moieties via selective deprotection/oxidation of the respective silylated precursors with boron fluoride and subsequent quenching with tetraethyl orthosilicate. Nitronyl nitroxide biradicals PBI–NN, IIn–NN, PhDPP–NN, ThDPP–NN, and FuDPP–NN bridged by perylene bisimide (PBI), isoindigo (IIn), and diketopyrrolopyrrole (DPP) pigment colorants were finally obtained as bench stable compounds after periodate oxidation with yields of 60–81%. The absorption spectral signatures of the chromophores remain preserved in the open shell state and match the ones of the pristine parent compounds, which allowed an a priori prediction of their optical properties. Consequently, we achieved twofold spin labeling while keeping the intrinsic properties of the electron deficient chromophores intact.}, author = {Rausch, Rodger and Krause, Ana-Maria and Krummenacher, Ivo and Braunschweig, Holger and Würthner, Frank}, journal = {J. Org. Chem.}, keywords = {myown}, month = {01}, number = 3, pages = {2447–2457}, publisher = {American Chemical Society ({ACS})}, title = {Nitronyl Nitroxide Bifunctionalized Electron-Poor Chromophores: Synthesis of Stable Dye Biradicals by Lewis Acid Promoted Desilylation}, volume = 86, year = 2021 }

  %0 Journal Article %1 Rausch_2021 %A Rausch, Rodger %A Krause, Ana-Maria %A Krummenacher, Ivo %A Braunschweig, Holger %A Würthner, Frank %D 2021 %I American Chemical Society (ACS) %J J. Org. Chem. %N 3 %P 2447--2457 %R 10.1021/acs.joc.0c02613 %T Nitronyl Nitroxide Bifunctionalized Electron-Poor Chromophores: Synthesis of Stable Dye Biradicals by Lewis Acid Promoted Desilylation %U https://doi.org/10.1021%2Facs.joc.0c02613 %V 86 %X Open shell organic molecules bearing π-cores are of great interest for optical, electronic, and magnetic applications but frequently suffer fast decomposition or lack synthetic accessibility. In this regard, nitronyl nitroxides are promising candidates for stable (bi-)radicals due to their high degree of spin delocalization along the O–N–C–N–O pentad unit. Unfortunately, they are limited to electron-rich systems so far. To overcome this limitation, we developed a synthetic procedure for the twofold spin decoration of electron-poor chromophores (Ered = −1158 mV) with nitronyl nitroxide radical moieties via selective deprotection/oxidation of the respective silylated precursors with boron fluoride and subsequent quenching with tetraethyl orthosilicate. Nitronyl nitroxide biradicals PBI–NN, IIn–NN, PhDPP–NN, ThDPP–NN, and FuDPP–NN bridged by perylene bisimide (PBI), isoindigo (IIn), and diketopyrrolopyrrole (DPP) pigment colorants were finally obtained as bench stable compounds after periodate oxidation with yields of 60–81%. The absorption spectral signatures of the chromophores remain preserved in the open shell state and match the ones of the pristine parent compounds, which allowed an a priori prediction of their optical properties. Consequently, we achieved twofold spin labeling while keeping the intrinsic properties of the electron deficient chromophores intact.
• Reversible fluorescence modulation through the photoisomerization of an azobenzene-bridged perylene bisimide cyclophane. Ouyang, Guanghui; Bialas, David; Würthner, Frank. In Org. Chem. Front., 8(7), pp. 1424–1430. 2021.
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  A new type of perylene bisimide (PBI) cyclophane in which two PBI chromophores were linked via an azobenzene (Azo) bridge was designed and synthesized. It was found that the integration of electron-donating azobenzene and electron-deficient PBI in a well-defined cyclophane enables the regulation of the fluorescence lifetime and quantum yield of the PBI units. With the aid of a high efficiency trans → cis transformation of the azobenzene moiety, the PBI–PBI chromophore distance can be effectively controlled as revealed by exciton coupling and density functional theory (DFT) computation, leading to additional non-radiative decay pathways and a pronounced fluorescence quenching due to cooperative adjustments of PBI–PBI and PBI–Azo interactions. Reversible fluorescence intensity switching for at least five cycles was successfully achieved with alternate UV and visible light irradiation. These well-controlled fluorescence modulation and photoswitching behaviours not only provide insights into interchromophoric interactions but also contribute to the development of stimuli-responsive luminescent macrocycles.

  @article{D0QO01635G, abstract = {A new type of perylene bisimide (PBI) cyclophane in which two PBI chromophores were linked via an azobenzene (Azo) bridge was designed and synthesized. It was found that the integration of electron-donating azobenzene and electron-deficient PBI in a well-defined cyclophane enables the regulation of the fluorescence lifetime and quantum yield of the PBI units. With the aid of a high efficiency trans → cis transformation of the azobenzene moiety{,} the PBI–PBI chromophore distance can be effectively controlled as revealed by exciton coupling and density functional theory (DFT) computation{,} leading to additional non-radiative decay pathways and a pronounced fluorescence quenching due to cooperative adjustments of PBI–PBI and PBI–Azo interactions. Reversible fluorescence intensity switching for at least five cycles was successfully achieved with alternate UV and visible light irradiation. These well-controlled fluorescence modulation and photoswitching behaviours not only provide insights into interchromophoric interactions but also contribute to the development of stimuli-responsive luminescent macrocycles.}, author = {Ouyang, Guanghui and Bialas, David and Würthner, Frank}, journal = {Org. Chem. Front.}, keywords = {myown}, number = 7, pages = {1424-1430}, publisher = {The Royal Society of Chemistry}, title = {Reversible fluorescence modulation through the photoisomerization of an azobenzene-bridged perylene bisimide cyclophane}, volume = 8, year = 2021 }

  %0 Journal Article %1 D0QO01635G %A Ouyang, Guanghui %A Bialas, David %A Würthner, Frank %D 2021 %I The Royal Society of Chemistry %J Org. Chem. Front. %N 7 %P 1424-1430 %R 10.1039/D0QO01635G %T Reversible fluorescence modulation through the photoisomerization of an azobenzene-bridged perylene bisimide cyclophane %U http://dx.doi.org/10.1039/D0QO01635G %V 8 %X A new type of perylene bisimide (PBI) cyclophane in which two PBI chromophores were linked via an azobenzene (Azo) bridge was designed and synthesized. It was found that the integration of electron-donating azobenzene and electron-deficient PBI in a well-defined cyclophane enables the regulation of the fluorescence lifetime and quantum yield of the PBI units. With the aid of a high efficiency trans → cis transformation of the azobenzene moiety, the PBI–PBI chromophore distance can be effectively controlled as revealed by exciton coupling and density functional theory (DFT) computation, leading to additional non-radiative decay pathways and a pronounced fluorescence quenching due to cooperative adjustments of PBI–PBI and PBI–Azo interactions. Reversible fluorescence intensity switching for at least five cycles was successfully achieved with alternate UV and visible light irradiation. These well-controlled fluorescence modulation and photoswitching behaviours not only provide insights into interchromophoric interactions but also contribute to the development of stimuli-responsive luminescent macrocycles.
• PAHs Containing both Heptagon and Pentagon: Corannulene Extension by [5+2] Annulation. Schnitzlein, Matthias; Mützel, Carina; Shoyama, Kazutaka; Farrell, Jeffrey M.; Würthner, Frank. In Eur. J. Org. Chem., 2022(5). 2021.
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  Utilizing Pd-catalyzed [5+2] annulation a series of heptagon-extended corannulenes could be synthesized from a borinic acid precursor furnished by C−H borylation strategy. Single-crystal X-ray analysis revealed the presence of two conformational enantiomers crystallizing in a racemic mixture. Through their embedded five- and seven-membered rings these polycyclic aromatic hydrocarbons (PAHs) exhibit both negative and positive curvature and UV/Vis/NIR absorption spectroscopy as well as cyclic voltammetry experiments provided insights into the influence of larger flanking aromatic systems and electron-donating substituents encompassing the heptagonal ring. Through [5+2] annulation of acenaphthylene an azulene-containing PAH with intriguing optoelectronical properties including a very small bandgap and absorption over the whole visible spectrum could be obtained. Theoretical calculations were employed to elucidate the long-wavelength absorption and aromaticity.

  @article{Schnitzlein_2021, abstract = {Utilizing Pd-catalyzed [5+2] annulation a series of heptagon-extended corannulenes could be synthesized from a borinic acid precursor furnished by C−H borylation strategy. Single-crystal X-ray analysis revealed the presence of two conformational enantiomers crystallizing in a racemic mixture. Through their embedded five- and seven-membered rings these polycyclic aromatic hydrocarbons (PAHs) exhibit both negative and positive curvature and UV/Vis/NIR absorption spectroscopy as well as cyclic voltammetry experiments provided insights into the influence of larger flanking aromatic systems and electron-donating substituents encompassing the heptagonal ring. Through [5+2] annulation of acenaphthylene an azulene-containing PAH with intriguing optoelectronical properties including a very small bandgap and absorption over the whole visible spectrum could be obtained. Theoretical calculations were employed to elucidate the long-wavelength absorption and aromaticity.}, author = {Schnitzlein, Matthias and Mützel, Carina and Shoyama, Kazutaka and Farrell, Jeffrey M. and Würthner, Frank}, journal = {Eur. J. Org. Chem.}, keywords = {myown}, month = 12, number = 5, publisher = {Wiley}, title = {PAHs Containing both Heptagon and Pentagon: Corannulene Extension by [5+2] Annulation}, volume = 2022, year = 2021 }

  %0 Journal Article %1 Schnitzlein_2021 %A Schnitzlein, Matthias %A Mützel, Carina %A Shoyama, Kazutaka %A Farrell, Jeffrey M. %A Würthner, Frank %D 2021 %I Wiley %J Eur. J. Org. Chem. %N 5 %R 10.1002/ejoc.202101273 %T PAHs Containing both Heptagon and Pentagon: Corannulene Extension by [5+2] Annulation %U https://doi.org/10.1002%2Fejoc.202101273 %V 2022 %X Utilizing Pd-catalyzed [5+2] annulation a series of heptagon-extended corannulenes could be synthesized from a borinic acid precursor furnished by C−H borylation strategy. Single-crystal X-ray analysis revealed the presence of two conformational enantiomers crystallizing in a racemic mixture. Through their embedded five- and seven-membered rings these polycyclic aromatic hydrocarbons (PAHs) exhibit both negative and positive curvature and UV/Vis/NIR absorption spectroscopy as well as cyclic voltammetry experiments provided insights into the influence of larger flanking aromatic systems and electron-donating substituents encompassing the heptagonal ring. Through [5+2] annulation of acenaphthylene an azulene-containing PAH with intriguing optoelectronical properties including a very small bandgap and absorption over the whole visible spectrum could be obtained. Theoretical calculations were employed to elucidate the long-wavelength absorption and aromaticity.
• Macrocyclic Donor-Acceptor Dyads Composed of a Perylene Bisimide Surrounded by Oligothiophene Bridges. Bold, Kevin; Stolte, Matthias; Shoyama, Kazutaka; Holzapfel, Marco; Schmiedel, Alexander; Lambert, Christoph; Würthner, Frank. In Angewandte Chemie International Edition. 2021.
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  Two macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) have been synthesized via a platinum-mediated cross coupling strategy. The crystal structure of the double bridged PBI reveals all syn- arranged thiophene units which completely enclose the planar PBI chromophore via a 12-membered ring. The target structures were characterized by steady-state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor-acceptor dyads show ultrafast Förster Resonance Energy Transfer (FRET) and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent.

  @article{Bold_2021, abstract = {Two macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) have been synthesized via a platinum-mediated cross coupling strategy. The crystal structure of the double bridged PBI reveals all syn- arranged thiophene units which completely enclose the planar PBI chromophore via a 12-membered ring. The target structures were characterized by steady-state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor-acceptor dyads show ultrafast Förster Resonance Energy Transfer (FRET) and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent.}, author = {Bold, Kevin and Stolte, Matthias and Shoyama, Kazutaka and Holzapfel, Marco and Schmiedel, Alexander and Lambert, Christoph and Würthner, Frank}, journal = {Angewandte Chemie International Edition}, keywords = {myown}, month = 10, publisher = {Wiley}, title = {Macrocyclic Donor-Acceptor Dyads Composed of a Perylene Bisimide Surrounded by Oligothiophene Bridges}, year = 2021 }

  %0 Journal Article %1 Bold_2021 %A Bold, Kevin %A Stolte, Matthias %A Shoyama, Kazutaka %A Holzapfel, Marco %A Schmiedel, Alexander %A Lambert, Christoph %A Würthner, Frank %D 2021 %I Wiley %J Angewandte Chemie International Edition %R 10.1002/anie.202113598 %T Macrocyclic Donor-Acceptor Dyads Composed of a Perylene Bisimide Surrounded by Oligothiophene Bridges %U https://doi.org/10.1002%2Fanie.202113598 %X Two macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) have been synthesized via a platinum-mediated cross coupling strategy. The crystal structure of the double bridged PBI reveals all syn- arranged thiophene units which completely enclose the planar PBI chromophore via a 12-membered ring. The target structures were characterized by steady-state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor-acceptor dyads show ultrafast Förster Resonance Energy Transfer (FRET) and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent.
• Two-step anti-cooperative self-assembly process into defined π-stacked dye oligomers: insights into aggregation-induced enhanced emission. Vonhausen, Yvonne; Lohr, Andreas; Stolte, Matthias; Würthner, Frank. In Chem. Sci., 12(37), pp. 12302–12314. 2021.
  • [ Abstract ]
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  Aggregation-induced emission enhancement (AIEE) phenomena received great popularity during the last decade but in most cases insights into the packing structure – fluorescence properties remained scarce. Here, an almost non-fluorescent merocyanine dye was equipped with large solubilizing substituents, which allowed the investigation of it's aggregation behaviour in unpolar solvents over a large concentration range (10−2 to 10−7 M). In depth analysis of the self-assembly process by concentration-dependent UV/Vis spectroscopy at different temperatures revealed a two-step anti-cooperative aggregation mechanism. In the first step a co-facially stacked dimer is formed driven by dipole–dipole interactions. In a second step these dimers self-assemble to give an oligomer stack consisting of about ten dyes. Concentration- and temperature-dependent UV/Vis spectroscopy provided insight into the thermodynamic parameters and allowed to identify conditions where either the monomer, the dimer or the decamer prevails. The centrosymmetric dimer structure could be proven by 2D NMR spectroscopy. For the larger decamer atomic force microscopy (AFM), diffusion ordered spectroscopy (DOSY) and vapour pressure osmometric (VPO) measurements consistently indicated that it is of small and defined size. Fluorescence, circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy provided insights into the photofunctional properties of the dye aggregates. Starting from an essentially non-fluorescent monomer (ΦFl = 0.23%) a strong AIEE effect with excimer-type fluorescence (large Stokes shift, increased fluorescence lifetime) is observed upon formation of the dimer (ΦFl = 2.3%) and decamer (ΦFl = 4.5%) stack. This increase in fluorescence is accompanied for both aggregates by an aggregation-induced CPL enhancement with a strong increase of the glum from ∼0.001 for the dimer up to ∼0.011 for the higher aggregate. Analysis of the radiative and non-radiative decay rates corroborates the interpretation that the AIEE effect originates from a pronounced decrease of the non-radiative rate due to π–π-stacking induced rigidification that outmatches the effect of the reduced radiative rate that originates from the H-type exciton coupling in the co-facially stacked dyes.

  @article{D1SC03813C, abstract = {Aggregation-induced emission enhancement (AIEE) phenomena received great popularity during the last decade but in most cases insights into the packing structure – fluorescence properties remained scarce. Here{,} an almost non-fluorescent merocyanine dye was equipped with large solubilizing substituents{,} which allowed the investigation of it{'}s aggregation behaviour in unpolar solvents over a large concentration range (10−2 to 10−7 M). In depth analysis of the self-assembly process by concentration-dependent UV/Vis spectroscopy at different temperatures revealed a two-step anti-cooperative aggregation mechanism. In the first step a co-facially stacked dimer is formed driven by dipole–dipole interactions. In a second step these dimers self-assemble to give an oligomer stack consisting of about ten dyes. Concentration- and temperature-dependent UV/Vis spectroscopy provided insight into the thermodynamic parameters and allowed to identify conditions where either the monomer{,} the dimer or the decamer prevails. The centrosymmetric dimer structure could be proven by 2D NMR spectroscopy. For the larger decamer atomic force microscopy (AFM){,} diffusion ordered spectroscopy (DOSY) and vapour pressure osmometric (VPO) measurements consistently indicated that it is of small and defined size. Fluorescence{,} circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy provided insights into the photofunctional properties of the dye aggregates. Starting from an essentially non-fluorescent monomer (ΦFl = 0.23%) a strong AIEE effect with excimer-type fluorescence (large Stokes shift{,} increased fluorescence lifetime) is observed upon formation of the dimer (ΦFl = 2.3%) and decamer (ΦFl = 4.5%) stack. This increase in fluorescence is accompanied for both aggregates by an aggregation-induced CPL enhancement with a strong increase of the glum from ∼0.001 for the dimer up to ∼0.011 for the higher aggregate. Analysis of the radiative and non-radiative decay rates corroborates the interpretation that the AIEE effect originates from a pronounced decrease of the non-radiative rate due to π–π-stacking induced rigidification that outmatches the effect of the reduced radiative rate that originates from the H-type exciton coupling in the co-facially stacked dyes.}, author = {Vonhausen, Yvonne and Lohr, Andreas and Stolte, Matthias and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 37, pages = {12302-12314}, publisher = {The Royal Society of Chemistry}, title = {Two-step anti-cooperative self-assembly process into defined π-stacked dye oligomers: insights into aggregation-induced enhanced emission}, volume = 12, year = 2021 }

  %0 Journal Article %1 D1SC03813C %A Vonhausen, Yvonne %A Lohr, Andreas %A Stolte, Matthias %A Würthner, Frank %D 2021 %I The Royal Society of Chemistry %J Chem. Sci. %N 37 %P 12302-12314 %R 10.1039/D1SC03813C %T Two-step anti-cooperative self-assembly process into defined π-stacked dye oligomers: insights into aggregation-induced enhanced emission %U http://dx.doi.org/10.1039/D1SC03813C %V 12 %X Aggregation-induced emission enhancement (AIEE) phenomena received great popularity during the last decade but in most cases insights into the packing structure – fluorescence properties remained scarce. Here, an almost non-fluorescent merocyanine dye was equipped with large solubilizing substituents, which allowed the investigation of it's aggregation behaviour in unpolar solvents over a large concentration range (10−2 to 10−7 M). In depth analysis of the self-assembly process by concentration-dependent UV/Vis spectroscopy at different temperatures revealed a two-step anti-cooperative aggregation mechanism. In the first step a co-facially stacked dimer is formed driven by dipole–dipole interactions. In a second step these dimers self-assemble to give an oligomer stack consisting of about ten dyes. Concentration- and temperature-dependent UV/Vis spectroscopy provided insight into the thermodynamic parameters and allowed to identify conditions where either the monomer, the dimer or the decamer prevails. The centrosymmetric dimer structure could be proven by 2D NMR spectroscopy. For the larger decamer atomic force microscopy (AFM), diffusion ordered spectroscopy (DOSY) and vapour pressure osmometric (VPO) measurements consistently indicated that it is of small and defined size. Fluorescence, circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy provided insights into the photofunctional properties of the dye aggregates. Starting from an essentially non-fluorescent monomer (ΦFl = 0.23%) a strong AIEE effect with excimer-type fluorescence (large Stokes shift, increased fluorescence lifetime) is observed upon formation of the dimer (ΦFl = 2.3%) and decamer (ΦFl = 4.5%) stack. This increase in fluorescence is accompanied for both aggregates by an aggregation-induced CPL enhancement with a strong increase of the glum from ∼0.001 for the dimer up to ∼0.011 for the higher aggregate. Analysis of the radiative and non-radiative decay rates corroborates the interpretation that the AIEE effect originates from a pronounced decrease of the non-radiative rate due to π–π-stacking induced rigidification that outmatches the effect of the reduced radiative rate that originates from the H-type exciton coupling in the co-facially stacked dyes.
• An Efficient Narrowband Near-Infrared at 1040nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye. Kim, Jin Hong; Liess, Andreas; Stolte, Matthias; Krause, Ana-Maria; Stepanenko, Vladimir; Zhong, Chuwei; Bialas, David; Spano, Frank; Würthner, Frank. In Adv. Mater., 33(26), p. 2100582. 2021.
  • [ Abstract ]
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  A highly sensitive short-wave infrared (SWIR, λ > 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC61BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3% and a full-width at half-maximum of only 85 nm (815 cm−1) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.

  @article{Kim_2021, abstract = {A highly sensitive short-wave infrared (SWIR, λ > 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC61BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3% and a full-width at half-maximum of only 85 nm (815 cm−1) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.}, author = {Kim, Jin Hong and Liess, Andreas and Stolte, Matthias and Krause, Ana-Maria and Stepanenko, Vladimir and Zhong, Chuwei and Bialas, David and Spano, Frank and Würthner, Frank}, journal = {Adv. Mater.}, keywords = {myown}, month = {05}, number = 26, pages = 2100582, publisher = {Wiley}, title = {An Efficient Narrowband Near-Infrared at 1040nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye}, volume = 33, year = 2021 }

  %0 Journal Article %1 Kim_2021 %A Kim, Jin Hong %A Liess, Andreas %A Stolte, Matthias %A Krause, Ana-Maria %A Stepanenko, Vladimir %A Zhong, Chuwei %A Bialas, David %A Spano, Frank %A Würthner, Frank %D 2021 %I Wiley %J Adv. Mater. %N 26 %P 2100582 %R 10.1002/adma.202100582 %T An Efficient Narrowband Near-Infrared at 1040nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye %U https://doi.org/10.1002%2Fadma.202100582 %V 33 %X A highly sensitive short-wave infrared (SWIR, λ > 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC61BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3% and a full-width at half-maximum of only 85 nm (815 cm−1) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.
• Semitransparent Layers of Social Self-Sorting Merocyanine Dyes for Ultranarrow Bandwidth Organic Photodiodes. Schembri, Tim; Kim, Jin Hong; Liess, Andreas; Stepanenko, Vladimir; Stolte, Matthias; Würthner, Frank. In Advanced Optical Materials, 9(15), p. 2100213. 2021.
  • [ Abstract ]
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  Two dipolar merocyanines consisting of the same π-conjugated chromophore but different alkyl substituents adopt very different packing arrangements in their respective solid state with either H- or J-type exciton coupling, leading to ultranarrow absorption bands at 477 and 750 nm, respectively, due to exchange narrowing. The social self-sorting behavior of these push-pull chromophores in their mixed thin films is evaluated and the impact on morphology as well as opto-electronical properties is determined. The implementation of this well-tuned two-component material with tailored optical features allows to optimize planar heterojunction organic photodiodes with fullerene ​(C60) with either dual or single wavelength selectivity in the blue and NIR spectral range with ultranarrow bandwidths of only 11 nm (200 cm−1) and an external quantum efficiency of up to 18% at 754 nm under 0 V bias. The application of these photodiodes as low-power consuming heart rate monitors is demonstrated by a reflectance-mode photoplethysmography (PPG) sensor.

  @article{Schembri_2021, abstract = {Two dipolar merocyanines consisting of the same π-conjugated chromophore but different alkyl substituents adopt very different packing arrangements in their respective solid state with either H- or J-type exciton coupling, leading to ultranarrow absorption bands at 477 and 750 nm, respectively, due to exchange narrowing. The social self-sorting behavior of these push-pull chromophores in their mixed thin films is evaluated and the impact on morphology as well as opto-electronical properties is determined. The implementation of this well-tuned two-component material with tailored optical features allows to optimize planar heterojunction organic photodiodes with fullerene ​(C60) with either dual or single wavelength selectivity in the blue and NIR spectral range with ultranarrow bandwidths of only 11 nm (200 cm−1) and an external quantum efficiency of up to 18% at 754 nm under 0 V bias. The application of these photodiodes as low-power consuming heart rate monitors is demonstrated by a reflectance-mode photoplethysmography (PPG) sensor.}, author = {Schembri, Tim and Kim, Jin Hong and Liess, Andreas and Stepanenko, Vladimir and Stolte, Matthias and Würthner, Frank}, journal = {Advanced Optical Materials}, keywords = {myown}, month = {05}, number = 15, pages = 2100213, publisher = {Wiley}, title = {Semitransparent Layers of Social Self-Sorting Merocyanine Dyes for Ultranarrow Bandwidth Organic Photodiodes}, volume = 9, year = 2021 }

  %0 Journal Article %1 Schembri_2021 %A Schembri, Tim %A Kim, Jin Hong %A Liess, Andreas %A Stepanenko, Vladimir %A Stolte, Matthias %A Würthner, Frank %D 2021 %I Wiley %J Advanced Optical Materials %N 15 %P 2100213 %R 10.1002/adom.202100213 %T Semitransparent Layers of Social Self-Sorting Merocyanine Dyes for Ultranarrow Bandwidth Organic Photodiodes %U https://doi.org/10.1002%2Fadom.202100213 %V 9 %X Two dipolar merocyanines consisting of the same π-conjugated chromophore but different alkyl substituents adopt very different packing arrangements in their respective solid state with either H- or J-type exciton coupling, leading to ultranarrow absorption bands at 477 and 750 nm, respectively, due to exchange narrowing. The social self-sorting behavior of these push-pull chromophores in their mixed thin films is evaluated and the impact on morphology as well as opto-electronical properties is determined. The implementation of this well-tuned two-component material with tailored optical features allows to optimize planar heterojunction organic photodiodes with fullerene ​(C60) with either dual or single wavelength selectivity in the blue and NIR spectral range with ultranarrow bandwidths of only 11 nm (200 cm−1) and an external quantum efficiency of up to 18% at 754 nm under 0 V bias. The application of these photodiodes as low-power consuming heart rate monitors is demonstrated by a reflectance-mode photoplethysmography (PPG) sensor.
• Unusual Zig-Zag Effect in the Electrochemical Oxidation of Phenyl End-Capped a-Oligothiophenes. Bold, Kevin; Stolte, Matthias; Würthner, Frank. In Organic Materials, 03(02), pp. 119–127. 2021.
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  A series of phenyl end-capped α-oligothiophenes containing four to seven thiophene subunits (4T–7T) was synthesized utilizing palladium-catalyzed cross-coupling reactions. UV/Vis spectroscopic analysis revealed one broad absorption band that shifts bathochromically with increasing number of thiophene units. Structured emission spectra are observed with Stokes shift ν~4000 cm−1 and quantum yields of up to 53%. End-capping of the oligothiophene molecules by phenyl units does not only extend the effective conjugation but also prevents from α–α-homocoupling upon electrochemical oxidation. Accordingly, reversible redox waves are observed in cyclic voltammetry with up to four reversible one-electron processes for the two longer congeners. Analyses of the first two oxidation processes in the framework of multiredox systems provide insight into the stabilization or destabilization of polaronic and bipolaronic states. An unusual zig-zag trend for the first (and to a lesser extend second) oxidation process could be explained by the sterical encumbrance of solubilizing hexyl chains in 5T and 7T molecules which counteract the formation of a fully planar quinoidal oligothiophene backbone.

  @article{Bold_2021, abstract = {A series of phenyl end-capped α-oligothiophenes containing four to seven thiophene subunits (4T–7T) was synthesized utilizing palladium-catalyzed cross-coupling reactions. UV/Vis spectroscopic analysis revealed one broad absorption band that shifts bathochromically with increasing number of thiophene units. Structured emission spectra are observed with Stokes shift ν 4000 cm−1 and quantum yields of up to 53%. End-capping of the oligothiophene molecules by phenyl units does not only extend the effective conjugation but also prevents from α–α-homocoupling upon electrochemical oxidation. Accordingly, reversible redox waves are observed in cyclic voltammetry with up to four reversible one-electron processes for the two longer congeners. Analyses of the first two oxidation processes in the framework of multiredox systems provide insight into the stabilization or destabilization of polaronic and bipolaronic states. An unusual zig-zag trend for the first (and to a lesser extend second) oxidation process could be explained by the sterical encumbrance of solubilizing hexyl chains in 5T and 7T molecules which counteract the formation of a fully planar quinoidal oligothiophene backbone.}, author = {Bold, Kevin and Stolte, Matthias and Würthner, Frank}, journal = {Organic Materials}, keywords = {myown}, month = {04}, number = {02}, pages = {119–127}, publisher = {Georg Thieme Verlag {KG}}, title = {Unusual Zig-Zag Effect in the Electrochemical Oxidation of Phenyl End-Capped a-Oligothiophenes}, volume = {03}, year = 2021 }

  %0 Journal Article %1 Bold_2021 %A Bold, Kevin %A Stolte, Matthias %A Würthner, Frank %D 2021 %I Georg Thieme Verlag KG %J Organic Materials %N 02 %P 119--127 %R 10.1055/s-0041-1726089 %T Unusual Zig-Zag Effect in the Electrochemical Oxidation of Phenyl End-Capped a-Oligothiophenes %U https://doi.org/10.1055%2Fs-0041-1726089 %V 03 %X A series of phenyl end-capped α-oligothiophenes containing four to seven thiophene subunits (4T–7T) was synthesized utilizing palladium-catalyzed cross-coupling reactions. UV/Vis spectroscopic analysis revealed one broad absorption band that shifts bathochromically with increasing number of thiophene units. Structured emission spectra are observed with Stokes shift ν~4000 cm−1 and quantum yields of up to 53%. End-capping of the oligothiophene molecules by phenyl units does not only extend the effective conjugation but also prevents from α–α-homocoupling upon electrochemical oxidation. Accordingly, reversible redox waves are observed in cyclic voltammetry with up to four reversible one-electron processes for the two longer congeners. Analyses of the first two oxidation processes in the framework of multiredox systems provide insight into the stabilization or destabilization of polaronic and bipolaronic states. An unusual zig-zag trend for the first (and to a lesser extend second) oxidation process could be explained by the sterical encumbrance of solubilizing hexyl chains in 5T and 7T molecules which counteract the formation of a fully planar quinoidal oligothiophene backbone.
• Controlling Topography and Crystallinity of Melt Electrowritten Poly(e-Caprolactone) Fibers. Blum, Carina; Weichhold, Jan; Hochleitner, Gernot; Stepanenko, Vladimir; Würthner, Frank; Groll, Jürgen; Jungst, Tomasz. In 3D Printing and Additive Manufact., 8(5), pp. 315–321. 2021.
  • [ Abstract ]
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  Melt electrowriting (MEW) is an aspiring 3D printing technology with an unprecedented resolution among fiber-based printing technologies. It offers the ability to direct-write predefined designs utilizing a jet of molten polymer to fabricate constructs composed of fibers with diameters of only a few micrometers. These dimensions enable unique construct properties. Poly(ɛ-caprolactone) (PCL), a semicrystalline polymer mainly used for biomedical and life science applications, is the most prominent material for MEW and exhibits excellent printing properties. Despite the wealth of melt electrowritten constructs that have been fabricated by MEW, a detailed investigation, especially regarding fiber analysis on a macro- and microlevel is still lacking. Hence, this study systematically examines the influence of process parameters such as spinneret diameter, feeding pressure, and collector velocity on the diameter and particularly the topography of PCL fibers and sheds light on how these parameters affect the mechanical properties and crystallinity. A correlation between the mechanical properties, crystallite size, and roughness of the deposited fiber, depending on the collector velocity and applied feeding pressure, is revealed. These findings are used to print constructs composed of fibers with different microtopography without affecting the fiber diameter and thus the macroscopic assembly of the printed constructs.

  @article{2021, abstract = {Melt electrowriting (MEW) is an aspiring 3D printing technology with an unprecedented resolution among fiber-based printing technologies. It offers the ability to direct-write predefined designs utilizing a jet of molten polymer to fabricate constructs composed of fibers with diameters of only a few micrometers. These dimensions enable unique construct properties. Poly(ɛ-caprolactone) (PCL), a semicrystalline polymer mainly used for biomedical and life science applications, is the most prominent material for MEW and exhibits excellent printing properties. Despite the wealth of melt electrowritten constructs that have been fabricated by MEW, a detailed investigation, especially regarding fiber analysis on a macro- and microlevel is still lacking. Hence, this study systematically examines the influence of process parameters such as spinneret diameter, feeding pressure, and collector velocity on the diameter and particularly the topography of PCL fibers and sheds light on how these parameters affect the mechanical properties and crystallinity. A correlation between the mechanical properties, crystallite size, and roughness of the deposited fiber, depending on the collector velocity and applied feeding pressure, is revealed. These findings are used to print constructs composed of fibers with different microtopography without affecting the fiber diameter and thus the macroscopic assembly of the printed constructs.}, author = {Blum, Carina and Weichhold, Jan and Hochleitner, Gernot and Stepanenko, Vladimir and Würthner, Frank and Groll, Jürgen and Jungst, Tomasz}, journal = {3D Printing and Additive Manufact.}, keywords = {myown}, month = 10, number = 5, pages = {315–321}, publisher = {Mary Ann Liebert Inc}, title = {Controlling Topography and Crystallinity of Melt Electrowritten Poly(e-Caprolactone) Fibers}, volume = 8, year = 2021 }

  %0 Journal Article %1 2021 %A Blum, Carina %A Weichhold, Jan %A Hochleitner, Gernot %A Stepanenko, Vladimir %A Würthner, Frank %A Groll, Jürgen %A Jungst, Tomasz %D 2021 %I Mary Ann Liebert Inc %J 3D Printing and Additive Manufact. %N 5 %P 315--321 %R 10.1089/3dp.2020.0290 %T Controlling Topography and Crystallinity of Melt Electrowritten Poly(e-Caprolactone) Fibers %U https://doi.org/10.1089%2F3dp.2020.0290 %V 8 %X Melt electrowriting (MEW) is an aspiring 3D printing technology with an unprecedented resolution among fiber-based printing technologies. It offers the ability to direct-write predefined designs utilizing a jet of molten polymer to fabricate constructs composed of fibers with diameters of only a few micrometers. These dimensions enable unique construct properties. Poly(ɛ-caprolactone) (PCL), a semicrystalline polymer mainly used for biomedical and life science applications, is the most prominent material for MEW and exhibits excellent printing properties. Despite the wealth of melt electrowritten constructs that have been fabricated by MEW, a detailed investigation, especially regarding fiber analysis on a macro- and microlevel is still lacking. Hence, this study systematically examines the influence of process parameters such as spinneret diameter, feeding pressure, and collector velocity on the diameter and particularly the topography of PCL fibers and sheds light on how these parameters affect the mechanical properties and crystallinity. A correlation between the mechanical properties, crystallite size, and roughness of the deposited fiber, depending on the collector velocity and applied feeding pressure, is revealed. These findings are used to print constructs composed of fibers with different microtopography without affecting the fiber diameter and thus the macroscopic assembly of the printed constructs.
• Slip-Stacked J-Aggregate Materials for Organic Solar Cells and Photodetectors. Kim, Jin Hong; Schembri, Tim; Bialas, David; Stolte, Matthias; Würthner, Frank. In Adv. Mater., p. 2104678. 2021.
  • [ Abstract ]
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  Dye–dye interactions affect the optical and electronic properties in organic semiconductor films of light harvesting and detecting optoelectronic applications. This review elaborates how to tailor these properties of organic semiconductors for organic solar cells (OSCs) and organic photodiodes (OPDs). While these devices rely on similar materials, the demands for their optical properties are rather different, the former requiring a broad absorption spectrum spanning from the UV over visible up to the near-infrared region and the latter an ultra-narrow absorption spectrum at a specific, targeted wavelength. In order to design organic semiconductors satisfying these demands, fundamental insights on the relationship of optical properties are provided depending on molecular packing arrangement and the resultant electronic coupling thereof. Based on recent advancements in the theoretical understanding of intermolecular interactions between slip-stacked dyes, distinguishing classical J-aggregates with predominant long-range Coulomb coupling from charge transfer (CT)-mediated or -coupled J-aggregates, whose red-shifts are primarily governed by short-range orbital interactions, is suggested. Within this framework, the relationship between aggregate structure and functional properties of representative classes of dye aggregates is analyzed for the most advanced OSCs and wavelength-selective OPDs, providing important insights into the rational design of thin-film optoelectronic materials.

  @article{Kim_2021, abstract = {Dye–dye interactions affect the optical and electronic properties in organic semiconductor films of light harvesting and detecting optoelectronic applications. This review elaborates how to tailor these properties of organic semiconductors for organic solar cells (OSCs) and organic photodiodes (OPDs). While these devices rely on similar materials, the demands for their optical properties are rather different, the former requiring a broad absorption spectrum spanning from the UV over visible up to the near-infrared region and the latter an ultra-narrow absorption spectrum at a specific, targeted wavelength. In order to design organic semiconductors satisfying these demands, fundamental insights on the relationship of optical properties are provided depending on molecular packing arrangement and the resultant electronic coupling thereof. Based on recent advancements in the theoretical understanding of intermolecular interactions between slip-stacked dyes, distinguishing classical J-aggregates with predominant long-range Coulomb coupling from charge transfer (CT)-mediated or -coupled J-aggregates, whose red-shifts are primarily governed by short-range orbital interactions, is suggested. Within this framework, the relationship between aggregate structure and functional properties of representative classes of dye aggregates is analyzed for the most advanced OSCs and wavelength-selective OPDs, providing important insights into the rational design of thin-film optoelectronic materials.}, author = {Kim, Jin Hong and Schembri, Tim and Bialas, David and Stolte, Matthias and Würthner, Frank}, journal = {Adv. Mater.}, keywords = {myown}, month = 10, pages = 2104678, publisher = {Wiley}, title = {Slip-Stacked J-Aggregate Materials for Organic Solar Cells and Photodetectors}, year = 2021 }

  %0 Journal Article %1 Kim_2021 %A Kim, Jin Hong %A Schembri, Tim %A Bialas, David %A Stolte, Matthias %A Würthner, Frank %D 2021 %I Wiley %J Adv. Mater. %P 2104678 %R 10.1002/adma.202104678 %T Slip-Stacked J-Aggregate Materials for Organic Solar Cells and Photodetectors %U https://doi.org/10.1002%2Fadma.202104678 %X Dye–dye interactions affect the optical and electronic properties in organic semiconductor films of light harvesting and detecting optoelectronic applications. This review elaborates how to tailor these properties of organic semiconductors for organic solar cells (OSCs) and organic photodiodes (OPDs). While these devices rely on similar materials, the demands for their optical properties are rather different, the former requiring a broad absorption spectrum spanning from the UV over visible up to the near-infrared region and the latter an ultra-narrow absorption spectrum at a specific, targeted wavelength. In order to design organic semiconductors satisfying these demands, fundamental insights on the relationship of optical properties are provided depending on molecular packing arrangement and the resultant electronic coupling thereof. Based on recent advancements in the theoretical understanding of intermolecular interactions between slip-stacked dyes, distinguishing classical J-aggregates with predominant long-range Coulomb coupling from charge transfer (CT)-mediated or -coupled J-aggregates, whose red-shifts are primarily governed by short-range orbital interactions, is suggested. Within this framework, the relationship between aggregate structure and functional properties of representative classes of dye aggregates is analyzed for the most advanced OSCs and wavelength-selective OPDs, providing important insights into the rational design of thin-film optoelectronic materials.
• Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation. Gildemeister, Nora; Ricci, Gaetano; Böhner, Lukas; Neudörfl, Jörg M.; Hertel, Dirk; Würthner, Frank; Negri, Fabrizia; Meerholz, Klaus; Fazzi, Daniele. In J. Mater. Chem. C, 9(33), pp. 10851–10864. 2021.
  • [ Abstract ]
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  Merocyanines consist of electronic donor (D) and acceptor (A) subunits connected via a methine bridge. They are highly polar organic π-conjugated molecules investigated for their self-assembly and optoelectronic properties. The accurate description of their structure–property relationships remains challenging. We report a comprehensive analysis modelling intra- and inter-molecular charge transport parameters for a library of merocyanines featuring different D/A combinations and lateral substituents. We found that constrained DFT correctly assesses the molecular and electronic structure in single crystals. The most effective charge transport pathways were identified and charge carrier mobilities were computed. We analyzed a large variety of single crystals highlighting the impact of alkyl substituents and casting conditions, drawing clear structure vs. charge transport relationships. Our modelling suggests that hole transport is maximized when dipolar molecules are packed in slipped not centrosymmetric pairs, arranged in 2D interconnected architectures. Computed and experimental charge mobilities for single crystals are in good agreement.

  @article{D1TC01511G, abstract = {Merocyanines consist of electronic donor (D) and acceptor (A) subunits connected via a methine bridge. They are highly polar organic π-conjugated molecules investigated for their self-assembly and optoelectronic properties. The accurate description of their structure–property relationships remains challenging. We report a comprehensive analysis modelling intra- and inter-molecular charge transport parameters for a library of merocyanines featuring different D/A combinations and lateral substituents. We found that constrained DFT correctly assesses the molecular and electronic structure in single crystals. The most effective charge transport pathways were identified and charge carrier mobilities were computed. We analyzed a large variety of single crystals highlighting the impact of alkyl substituents and casting conditions, drawing clear structure vs. charge transport relationships. Our modelling suggests that hole transport is maximized when dipolar molecules are packed in slipped not centrosymmetric pairs, arranged in 2D interconnected architectures. Computed and experimental charge mobilities for single crystals are in good agreement.}, author = {Gildemeister, Nora and Ricci, Gaetano and Böhner, Lukas and Neudörfl, Jörg M. and Hertel, Dirk and Würthner, Frank and Negri, Fabrizia and Meerholz, Klaus and Fazzi, Daniele}, journal = {J. Mater. Chem. C}, keywords = {myown}, number = 33, pages = {10851-10864}, publisher = {The Royal Society of Chemistry}, title = {Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation}, volume = 9, year = 2021 }

  %0 Journal Article %1 D1TC01511G %A Gildemeister, Nora %A Ricci, Gaetano %A Böhner, Lukas %A Neudörfl, Jörg M. %A Hertel, Dirk %A Würthner, Frank %A Negri, Fabrizia %A Meerholz, Klaus %A Fazzi, Daniele %D 2021 %I The Royal Society of Chemistry %J J. Mater. Chem. C %N 33 %P 10851-10864 %R 10.1039/D1TC01511G %T Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation %U http://dx.doi.org/10.1039/D1TC01511G %V 9 %X Merocyanines consist of electronic donor (D) and acceptor (A) subunits connected via a methine bridge. They are highly polar organic π-conjugated molecules investigated for their self-assembly and optoelectronic properties. The accurate description of their structure–property relationships remains challenging. We report a comprehensive analysis modelling intra- and inter-molecular charge transport parameters for a library of merocyanines featuring different D/A combinations and lateral substituents. We found that constrained DFT correctly assesses the molecular and electronic structure in single crystals. The most effective charge transport pathways were identified and charge carrier mobilities were computed. We analyzed a large variety of single crystals highlighting the impact of alkyl substituents and casting conditions, drawing clear structure vs. charge transport relationships. Our modelling suggests that hole transport is maximized when dipolar molecules are packed in slipped not centrosymmetric pairs, arranged in 2D interconnected architectures. Computed and experimental charge mobilities for single crystals are in good agreement.
• Switching resonance character within merocyanine stacks and its impact on excited-state dynamics. Kim, Taeyeon; Kang, Seongsoo; Kirchner, Eva; Bialas, David; Kim, Woojae; Würthner, Frank; Kim, Dongho. In Chem, 7(3), pp. 715–725. 2021.
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  @article{Kim_2021, author = {Kim, Taeyeon and Kang, Seongsoo and Kirchner, Eva and Bialas, David and Kim, Woojae and Würthner, Frank and Kim, Dongho}, journal = {Chem}, keywords = {myown}, month = {03}, number = 3, pages = {715–725}, publisher = {Elsevier {BV}}, title = {Switching resonance character within merocyanine stacks and its impact on excited-state dynamics}, volume = 7, year = 2021 }

  %0 Journal Article %1 Kim_2021 %A Kim, Taeyeon %A Kang, Seongsoo %A Kirchner, Eva %A Bialas, David %A Kim, Woojae %A Würthner, Frank %A Kim, Dongho %D 2021 %I Elsevier BV %J Chem %N 3 %P 715--725 %R 10.1016/j.chempr.2020.12.003 %T Switching resonance character within merocyanine stacks and its impact on excited-state dynamics %U https://doi.org/10.1016%2Fj.chempr.2020.12.003 %V 7
• Perspectives in Dye Chemistry: A Rational Approach toward Functional Materials by Understanding the Aggregate State. Bialas, David; Kirchner, Eva; Röhr, Merle I. S.; Würthner, Frank. In J. Am. Chem. Soc., 143(12), pp. 4500–4518. 2021.
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  The past 20 years have witnessed a renaissance of dye chemistry, moving from traditional colorant research toward functional materials. Different from traditional colorant research, the properties of functional materials are governed extensively by intermolecular interactions, thereby entailing significant limitations to the classical approach based on molecular structure–molecular property (color, emission, redox properties, etc.) relationships for the respective dye molecules. However, as discussed in this Perspective, such an approach can be pursued for dye aggregates, and in many cases already well-tailored dimers are sufficient to understand the influence of supramolecular organization on the functional properties of ground and photoexcited states. Illustrative examples will be given for exciton coupling and charge-transfer coupling and how these properties relate to desirable functions such as fluorescence, symmetry-breaking charge separation, and singlet fission in molecular aggregates. While the progress in this research so far mostly originated from studies on well-defined folded and self-assembled structures composed of only two dye molecules, future work will have to advance toward larger oligomers of specific size and geometry. Furthermore, future experimental studies should be guided to a larger extent by theoretical predictions that may be supported by machine learning algorithms and new concepts from artificial intelligence. Beyond already pursued calculations of potential energy landscapes, we suggest the development of theoretical approaches that identify the most desirable dye aggregate structures for a particular property on functional energy landscapes.

  @article{Bialas_2021, abstract = {The past 20 years have witnessed a renaissance of dye chemistry, moving from traditional colorant research toward functional materials. Different from traditional colorant research, the properties of functional materials are governed extensively by intermolecular interactions, thereby entailing significant limitations to the classical approach based on molecular structure–molecular property (color, emission, redox properties, etc.) relationships for the respective dye molecules. However, as discussed in this Perspective, such an approach can be pursued for dye aggregates, and in many cases already well-tailored dimers are sufficient to understand the influence of supramolecular organization on the functional properties of ground and photoexcited states. Illustrative examples will be given for exciton coupling and charge-transfer coupling and how these properties relate to desirable functions such as fluorescence, symmetry-breaking charge separation, and singlet fission in molecular aggregates. While the progress in this research so far mostly originated from studies on well-defined folded and self-assembled structures composed of only two dye molecules, future work will have to advance toward larger oligomers of specific size and geometry. Furthermore, future experimental studies should be guided to a larger extent by theoretical predictions that may be supported by machine learning algorithms and new concepts from artificial intelligence. Beyond already pursued calculations of potential energy landscapes, we suggest the development of theoretical approaches that identify the most desirable dye aggregate structures for a particular property on functional energy landscapes.}, author = {Bialas, David and Kirchner, Eva and Röhr, Merle I. S. and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {03}, number = 12, pages = {4500–4518}, publisher = {American Chemical Society ({ACS})}, title = {Perspectives in Dye Chemistry: A Rational Approach toward Functional Materials by Understanding the Aggregate State}, volume = 143, year = 2021 }

  %0 Journal Article %1 Bialas_2021 %A Bialas, David %A Kirchner, Eva %A Röhr, Merle I. S. %A Würthner, Frank %D 2021 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 12 %P 4500--4518 %R 10.1021/jacs.0c13245 %T Perspectives in Dye Chemistry: A Rational Approach toward Functional Materials by Understanding the Aggregate State %U https://doi.org/10.1021%2Fjacs.0c13245 %V 143 %X The past 20 years have witnessed a renaissance of dye chemistry, moving from traditional colorant research toward functional materials. Different from traditional colorant research, the properties of functional materials are governed extensively by intermolecular interactions, thereby entailing significant limitations to the classical approach based on molecular structure–molecular property (color, emission, redox properties, etc.) relationships for the respective dye molecules. However, as discussed in this Perspective, such an approach can be pursued for dye aggregates, and in many cases already well-tailored dimers are sufficient to understand the influence of supramolecular organization on the functional properties of ground and photoexcited states. Illustrative examples will be given for exciton coupling and charge-transfer coupling and how these properties relate to desirable functions such as fluorescence, symmetry-breaking charge separation, and singlet fission in molecular aggregates. While the progress in this research so far mostly originated from studies on well-defined folded and self-assembled structures composed of only two dye molecules, future work will have to advance toward larger oligomers of specific size and geometry. Furthermore, future experimental studies should be guided to a larger extent by theoretical predictions that may be supported by machine learning algorithms and new concepts from artificial intelligence. Beyond already pursued calculations of potential energy landscapes, we suggest the development of theoretical approaches that identify the most desirable dye aggregate structures for a particular property on functional energy landscapes.
• Folding-induced Fluorescence Enhancement in a Series of Merocyanine Hetero-Folda-Trimers. Schulz, Alexander; Würthner, Frank. In Angew. Chem. Int. Ed., 61(2). 2021.
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  Many dyes suffer from fast non-radiative decaypathways, thereby showing only short-lived excited states andweak photoluminescence. Here we show a pronounced fluo-rescence enhancement for a weakly fluorescent merocyanine(MC) dye by being co-facially stacked to other dyes in hetero-folda-trimer architectures. By means of fluorescence spectros-copy (lifetime, quantum yield) the fluorescence enhancementwas explained by the rigidification of the emitting chromo-phore in the defined foldamer architecture and the presence ofa non-forbidden lowest exciton state in H-coupled hetero-aggregates. This folding-induced fluorescence enhancement(FIFE) for specific sequences ofp-stacked dyes points ata viable strategy toward improved fluorophores that relates tothe approach used by nature in the green fluorescent protein(GFP).

  @article{Schulz_2021, abstract = {Many dyes suffer from fast non-radiative decaypathways, thereby showing only short-lived excited states andweak photoluminescence. Here we show a pronounced fluo-rescence enhancement for a weakly fluorescent merocyanine(MC) dye by being co-facially stacked to other dyes in hetero-folda-trimer architectures. By means of fluorescence spectros-copy (lifetime, quantum yield) the fluorescence enhancementwas explained by the rigidification of the emitting chromo-phore in the defined foldamer architecture and the presence ofa non-forbidden lowest exciton state in H-coupled hetero-aggregates. This folding-induced fluorescence enhancement(FIFE) for specific sequences ofp-stacked dyes points ata viable strategy toward improved fluorophores that relates tothe approach used by nature in the green fluorescent protein(GFP).}, author = {Schulz, Alexander and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = 11, number = 2, publisher = {Wiley}, title = {Folding-induced Fluorescence Enhancement in a Series of Merocyanine Hetero-Folda-Trimers}, volume = 61, year = 2021 }

  %0 Journal Article %1 Schulz_2021 %A Schulz, Alexander %A Würthner, Frank %D 2021 %I Wiley %J Angew. Chem. Int. Ed. %N 2 %R 10.1002/anie.202114667 %T Folding-induced Fluorescence Enhancement in a Series of Merocyanine Hetero-Folda-Trimers %U https://doi.org/10.1002%2Fanie.202114667 %V 61 %X Many dyes suffer from fast non-radiative decaypathways, thereby showing only short-lived excited states andweak photoluminescence. Here we show a pronounced fluo-rescence enhancement for a weakly fluorescent merocyanine(MC) dye by being co-facially stacked to other dyes in hetero-folda-trimer architectures. By means of fluorescence spectros-copy (lifetime, quantum yield) the fluorescence enhancementwas explained by the rigidification of the emitting chromo-phore in the defined foldamer architecture and the presence ofa non-forbidden lowest exciton state in H-coupled hetero-aggregates. This folding-induced fluorescence enhancement(FIFE) for specific sequences ofp-stacked dyes points ata viable strategy toward improved fluorophores that relates tothe approach used by nature in the green fluorescent protein(GFP).
• Merocyanine Dyes with Extended Polymethine Chains by Simple Two-Step Condensation Sequence. Arjona-Esteban, Alhama; Rausch, Anja; Vysotsky, Myroslav O.; Würthner, Frank. In Synthesis, 53(02), pp. 318–325. 2021.
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  We describe a synthetic method for the synthesis of merocyanine dyes containing a bridge with three conjugated double bonds. This method consists of two successive condensation reactions. The first one is made between CH-acidic indane-1,3-dione acceptor units and an appropriate ketone (here acetone or hexan-2-one). The extended acceptor thus obtained is condensed with an aldehyde in the next step. The dyes show high tinctorial strength due to intense absorption bands at wavelengths between 500 and 750 nm.

  @article{arjonaesteban2021merocyanine, abstract = {We describe a synthetic method for the synthesis of merocyanine dyes containing a bridge with three conjugated double bonds. This method consists of two successive condensation reactions. The first one is made between CH-acidic indane-1,3-dione acceptor units and an appropriate ketone (here acetone or hexan-2-one). The extended acceptor thus obtained is condensed with an aldehyde in the next step. The dyes show high tinctorial strength due to intense absorption bands at wavelengths between 500 and 750 nm.}, author = {Arjona-Esteban, Alhama and Rausch, Anja and Vysotsky, Myroslav O. and Würthner, Frank}, journal = {Synthesis}, keywords = {myown}, number = {02}, pages = {318-325–}, title = {Merocyanine Dyes with Extended Polymethine Chains by Simple Two-Step Condensation Sequence}, volume = 53, year = 2021 }

  %0 Journal Article %1 arjonaesteban2021merocyanine %A Arjona-Esteban, Alhama %A Rausch, Anja %A Vysotsky, Myroslav O. %A Würthner, Frank %D 2021 %J Synthesis %N 02 %P 318-325-- %T Merocyanine Dyes with Extended Polymethine Chains by Simple Two-Step Condensation Sequence %V 53 %X We describe a synthetic method for the synthesis of merocyanine dyes containing a bridge with three conjugated double bonds. This method consists of two successive condensation reactions. The first one is made between CH-acidic indane-1,3-dione acceptor units and an appropriate ketone (here acetone or hexan-2-one). The extended acceptor thus obtained is condensed with an aldehyde in the next step. The dyes show high tinctorial strength due to intense absorption bands at wavelengths between 500 and 750 nm.
• Coherent two-dimensional electronic spectroelectrochemistry. Heitmüller, Julia; Eckstein, Klaus; Renner, Rebecca; Stolte, Matthias; Hertel, Tobias; Würthner, Frank; Brixner, Tobias. In Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, p. 119567. 2021.
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  We report the development of a new spectroscopic scheme, coherent two-dimensional (2D) electronic spectroelectrochemistry. Conventional 2D electronic spectroscopy has become well established to investigate molecular energy transfer, charge transfer, or structural dynamics with femtosecond time resolution following electronic excitation, providing frequency resolution for both the excitation and the detection step. Here we combine this method with electrochemistry in a flow cell. Thus we have established access to the dynamics of various oxidized and reduced molecular species in solution. We investigate the photophysics of a tetraphenoxy-substituted perylene bisimide dye and its reduced species as a proof of principle and find substantially different dynamics for the neutral and the twofold reduced compound. The electrochemical flow cell is furthermore applied in conventional transient absorption spectroscopy and photoluminescence spectroscopies as an application in different setups.

  @article{Heitm_ller_2021, abstract = {We report the development of a new spectroscopic scheme, coherent two-dimensional (2D) electronic spectroelectrochemistry. Conventional 2D electronic spectroscopy has become well established to investigate molecular energy transfer, charge transfer, or structural dynamics with femtosecond time resolution following electronic excitation, providing frequency resolution for both the excitation and the detection step. Here we combine this method with electrochemistry in a flow cell. Thus we have established access to the dynamics of various oxidized and reduced molecular species in solution. We investigate the photophysics of a tetraphenoxy-substituted perylene bisimide dye and its reduced species as a proof of principle and find substantially different dynamics for the neutral and the twofold reduced compound. The electrochemical flow cell is furthermore applied in conventional transient absorption spectroscopy and photoluminescence spectroscopies as an application in different setups.}, author = {Heitmüller, Julia and Eckstein, Klaus and Renner, Rebecca and Stolte, Matthias and Hertel, Tobias and Würthner, Frank and Brixner, Tobias}, journal = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy}, keywords = {myown}, month = {02}, pages = 119567, publisher = {Elsevier {BV}}, title = {Coherent two-dimensional electronic spectroelectrochemistry}, year = 2021 }

  %0 Journal Article %1 Heitm_ller_2021 %A Heitmüller, Julia %A Eckstein, Klaus %A Renner, Rebecca %A Stolte, Matthias %A Hertel, Tobias %A Würthner, Frank %A Brixner, Tobias %D 2021 %I Elsevier BV %J Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy %P 119567 %R 10.1016/j.saa.2021.119567 %T Coherent two-dimensional electronic spectroelectrochemistry %U https://doi.org/10.1016%2Fj.saa.2021.119567 %X We report the development of a new spectroscopic scheme, coherent two-dimensional (2D) electronic spectroelectrochemistry. Conventional 2D electronic spectroscopy has become well established to investigate molecular energy transfer, charge transfer, or structural dynamics with femtosecond time resolution following electronic excitation, providing frequency resolution for both the excitation and the detection step. Here we combine this method with electrochemistry in a flow cell. Thus we have established access to the dynamics of various oxidized and reduced molecular species in solution. We investigate the photophysics of a tetraphenoxy-substituted perylene bisimide dye and its reduced species as a proof of principle and find substantially different dynamics for the neutral and the twofold reduced compound. The electrochemical flow cell is furthermore applied in conventional transient absorption spectroscopy and photoluminescence spectroscopies as an application in different setups.
• Surface-Promoted Evolution of Ru-bda Coordination Oligomers Boosts the Efficiency of Water Oxidation Molecular Anodes. Gil-Sepulcre, Marcos; Lindner, Joachim O.; Schindler, Dorothee; Velasco, Lucia; Moonshiram, Dooshaye; Rüdiger, Olaf; DeBeer, Serena; Stepanenko, Vladimir; Solano, Eduardo; Würthner, Frank; Llobet, Antoni. In J. Am. Chem. Soc., 143(30), pp. 11651–11661. 2021.
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  A new Ru oligomer of formula [RuII(bda-κ-N2O2)(4,4′-bpy)]10(4,4′-bpy), 10 (bda is [2,2′-bipyridine]-6,6′-dicarboxylate and 4,4′-bpy is 4,4′-bipyridine), was synthesized and thoroughly characterized with spectroscopic, X-ray, and electrochemical techniques. This oligomer exhibits strong affinity for graphitic materials through CH−π interactions and thus easily anchors on multiwalled carbon nanotubes (CNT), generating the molecular hybrid material 10@CNT. The latter acts as a water oxidation catalyst and converts to a new species, 10′(H2O)2@CNT, during the electrochemical oxygen evolution process involving solvation and ligand reorganization facilitated by the interactions of molecular Ru catalyst and the surface. This heterogeneous system has been shown to be a powerful and robust molecular hybrid anode for electrocatalytic water oxidation into molecular oxygen, achieving current densities in the range of 200 mA/cm2 at pH 7 under an applied potential of 1.45 V vs NHE. The remarkable long-term stability of this hybrid material during turnover is rationalized based on the supramolecular interaction of the catalyst with the graphitic surface.

  @article{Gil_Sepulcre_2021, abstract = {A new Ru oligomer of formula [RuII(bda-κ-N2O2)(4,4′-bpy)]10(4,4′-bpy), 10 (bda is [2,2′-bipyridine]-6,6′-dicarboxylate and 4,4′-bpy is 4,4′-bipyridine), was synthesized and thoroughly characterized with spectroscopic, X-ray, and electrochemical techniques. This oligomer exhibits strong affinity for graphitic materials through CH−π interactions and thus easily anchors on multiwalled carbon nanotubes (CNT), generating the molecular hybrid material 10@CNT. The latter acts as a water oxidation catalyst and converts to a new species, 10′(H2O)2@CNT, during the electrochemical oxygen evolution process involving solvation and ligand reorganization facilitated by the interactions of molecular Ru catalyst and the surface. This heterogeneous system has been shown to be a powerful and robust molecular hybrid anode for electrocatalytic water oxidation into molecular oxygen, achieving current densities in the range of 200 mA/cm2 at pH 7 under an applied potential of 1.45 V vs NHE. The remarkable long-term stability of this hybrid material during turnover is rationalized based on the supramolecular interaction of the catalyst with the graphitic surface.}, author = {Gil-Sepulcre, Marcos and Lindner, Joachim O. and Schindler, Dorothee and Velasco, Lucia and Moonshiram, Dooshaye and Rüdiger, Olaf and DeBeer, Serena and Stepanenko, Vladimir and Solano, Eduardo and Würthner, Frank and Llobet, Antoni}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {07}, number = 30, pages = {11651–11661}, publisher = {American Chemical Society ({ACS})}, title = {Surface-Promoted Evolution of Ru-bda Coordination Oligomers Boosts the Efficiency of Water Oxidation Molecular Anodes}, volume = 143, year = 2021 }

  %0 Journal Article %1 Gil_Sepulcre_2021 %A Gil-Sepulcre, Marcos %A Lindner, Joachim O. %A Schindler, Dorothee %A Velasco, Lucia %A Moonshiram, Dooshaye %A Rüdiger, Olaf %A DeBeer, Serena %A Stepanenko, Vladimir %A Solano, Eduardo %A Würthner, Frank %A Llobet, Antoni %D 2021 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 30 %P 11651--11661 %R 10.1021/jacs.1c04738 %T Surface-Promoted Evolution of Ru-bda Coordination Oligomers Boosts the Efficiency of Water Oxidation Molecular Anodes %U https://doi.org/10.1021%2Fjacs.1c04738 %V 143 %X A new Ru oligomer of formula [RuII(bda-κ-N2O2)(4,4′-bpy)]10(4,4′-bpy), 10 (bda is [2,2′-bipyridine]-6,6′-dicarboxylate and 4,4′-bpy is 4,4′-bipyridine), was synthesized and thoroughly characterized with spectroscopic, X-ray, and electrochemical techniques. This oligomer exhibits strong affinity for graphitic materials through CH−π interactions and thus easily anchors on multiwalled carbon nanotubes (CNT), generating the molecular hybrid material 10@CNT. The latter acts as a water oxidation catalyst and converts to a new species, 10′(H2O)2@CNT, during the electrochemical oxygen evolution process involving solvation and ligand reorganization facilitated by the interactions of molecular Ru catalyst and the surface. This heterogeneous system has been shown to be a powerful and robust molecular hybrid anode for electrocatalytic water oxidation into molecular oxygen, achieving current densities in the range of 200 mA/cm2 at pH 7 under an applied potential of 1.45 V vs NHE. The remarkable long-term stability of this hybrid material during turnover is rationalized based on the supramolecular interaction of the catalyst with the graphitic surface.
• Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation. Gildemeister, Nora; Ricci, Gaetano; Böhner, Lukas; Neudörfl, Jörg M.; Hertel, Dirk; Würthner, Frank; Negri, Fabrizia; Meerholz, Klaus; Fazzi, Daniele. In J. Mater. Chem. C, 9(33), pp. 10851–10864. 2021.
  • [ Abstract ]
  • [ BibTeX ]
  • [ EndNote ]
  • [ DOI ]
  Merocyanines consist of electronic donor (D) and acceptor (A) subunits connected via a methine bridge. They are highly polar organic π-conjugated molecules investigated for their self-assembly and optoelectronic properties. The accurate description of their structure–property relationships remains challenging. We report a comprehensive analysis modelling intra- and inter-molecular charge transport parameters for a library of merocyanines featuring different D/A combinations and lateral substituents. We found that constrained DFT correctly assesses the molecular and electronic structure in single crystals. The most effective charge transport pathways were identified and charge carrier mobilities were computed. We analyzed a large variety of single crystals highlighting the impact of alkyl substituents and casting conditions, drawing clear structure vs. charge transport relationships. Our modelling suggests that hole transport is maximized when dipolar molecules are packed in slipped not centrosymmetric pairs, arranged in 2D interconnected architectures. Computed and experimental charge mobilities for single crystals are in good agreement.

  @article{D1TC01511G, abstract = {Merocyanines consist of electronic donor (D) and acceptor (A) subunits connected via a methine bridge. They are highly polar organic π-conjugated molecules investigated for their self-assembly and optoelectronic properties. The accurate description of their structure–property relationships remains challenging. We report a comprehensive analysis modelling intra- and inter-molecular charge transport parameters for a library of merocyanines featuring different D/A combinations and lateral substituents. We found that constrained DFT correctly assesses the molecular and electronic structure in single crystals. The most effective charge transport pathways were identified and charge carrier mobilities were computed. We analyzed a large variety of single crystals highlighting the impact of alkyl substituents and casting conditions, drawing clear structure vs. charge transport relationships. Our modelling suggests that hole transport is maximized when dipolar molecules are packed in slipped not centrosymmetric pairs, arranged in 2D interconnected architectures. Computed and experimental charge mobilities for single crystals are in good agreement.}, author = {Gildemeister, Nora and Ricci, Gaetano and Böhner, Lukas and Neudörfl, Jörg M. and Hertel, Dirk and Würthner, Frank and Negri, Fabrizia and Meerholz, Klaus and Fazzi, Daniele}, journal = {J. Mater. Chem. C}, keywords = {myown}, number = 33, pages = {10851-10864}, publisher = {The Royal Society of Chemistry}, title = {Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation}, volume = 9, year = 2021 }

  %0 Journal Article %1 D1TC01511G %A Gildemeister, Nora %A Ricci, Gaetano %A Böhner, Lukas %A Neudörfl, Jörg M. %A Hertel, Dirk %A Würthner, Frank %A Negri, Fabrizia %A Meerholz, Klaus %A Fazzi, Daniele %D 2021 %I The Royal Society of Chemistry %J J. Mater. Chem. C %N 33 %P 10851-10864 %R 10.1039/D1TC01511G %T Understanding the structural and charge transport property relationships for a variety of merocyanine single-crystals: a bottom up computational investigation %U http://dx.doi.org/10.1039/D1TC01511G %V 9 %X Merocyanines consist of electronic donor (D) and acceptor (A) subunits connected via a methine bridge. They are highly polar organic π-conjugated molecules investigated for their self-assembly and optoelectronic properties. The accurate description of their structure–property relationships remains challenging. We report a comprehensive analysis modelling intra- and inter-molecular charge transport parameters for a library of merocyanines featuring different D/A combinations and lateral substituents. We found that constrained DFT correctly assesses the molecular and electronic structure in single crystals. The most effective charge transport pathways were identified and charge carrier mobilities were computed. We analyzed a large variety of single crystals highlighting the impact of alkyl substituents and casting conditions, drawing clear structure vs. charge transport relationships. Our modelling suggests that hole transport is maximized when dipolar molecules are packed in slipped not centrosymmetric pairs, arranged in 2D interconnected architectures. Computed and experimental charge mobilities for single crystals are in good agreement.
• Double J-Coupling Strategy for Near Infrared Emitters. Shen, Chia-An; Stolte, Matthias; Kim, Jin Hong; Rausch, Anja; Würthner, Frank. In J. Am. Chem. Soc., 143(31), pp. 11946–11950. 2021.
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  Fluorophores emitting in the near-infrared (NIR) are highly desired for various applications, but increasing nonradiative rates cause severe fluorescence quenching for wavelengths beyond 800 nm. Here, a bis(squaraine) dye is reported that bears two NIR dyes in a head-to-tail chromophore arrangement. This arrangement leads to intramolecular J-type exciton coupling, resulting in an absorption maximum at 961 nm and a fluorescence peak at 971 nm with a quantum yield of 0.33% in chloroform. In less polar toluene, the bis(squaraine) self-assembles into nanofibers, affording another bathochromic shift with an absorption maximum at 1095 nm and a fluorescence peak at 1116 nm originating from intermolecular J-type coupling.

  @article{Shen_2021, abstract = {Fluorophores emitting in the near-infrared (NIR) are highly desired for various applications, but increasing nonradiative rates cause severe fluorescence quenching for wavelengths beyond 800 nm. Here, a bis(squaraine) dye is reported that bears two NIR dyes in a head-to-tail chromophore arrangement. This arrangement leads to intramolecular J-type exciton coupling, resulting in an absorption maximum at 961 nm and a fluorescence peak at 971 nm with a quantum yield of 0.33% in chloroform. In less polar toluene, the bis(squaraine) self-assembles into nanofibers, affording another bathochromic shift with an absorption maximum at 1095 nm and a fluorescence peak at 1116 nm originating from intermolecular J-type coupling.}, author = {Shen, Chia-An and Stolte, Matthias and Kim, Jin Hong and Rausch, Anja and Würthner, Frank}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {07}, number = 31, pages = {11946–11950}, publisher = {American Chemical Society ({ACS})}, title = {Double J-Coupling Strategy for Near Infrared Emitters}, volume = 143, year = 2021 }

  %0 Journal Article %1 Shen_2021 %A Shen, Chia-An %A Stolte, Matthias %A Kim, Jin Hong %A Rausch, Anja %A Würthner, Frank %D 2021 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 31 %P 11946--11950 %R 10.1021/jacs.1c05934 %T Double J-Coupling Strategy for Near Infrared Emitters %U https://doi.org/10.1021%2Fjacs.1c05934 %V 143 %X Fluorophores emitting in the near-infrared (NIR) are highly desired for various applications, but increasing nonradiative rates cause severe fluorescence quenching for wavelengths beyond 800 nm. Here, a bis(squaraine) dye is reported that bears two NIR dyes in a head-to-tail chromophore arrangement. This arrangement leads to intramolecular J-type exciton coupling, resulting in an absorption maximum at 961 nm and a fluorescence peak at 971 nm with a quantum yield of 0.33% in chloroform. In less polar toluene, the bis(squaraine) self-assembles into nanofibers, affording another bathochromic shift with an absorption maximum at 1095 nm and a fluorescence peak at 1116 nm originating from intermolecular J-type coupling.
• Tuning phenoxyl-substituted diketopyrrolopyrroles from quinoidal to biradical ground states through (hetero-)aromatic linkers. Rausch, Rodger; Röhr, Merle I. S.; Schmidt, David; Krummenacher, Ivo; Braunschweig, Holger; Würthner, Frank. In Chem. Sci., 12(2), pp. 793–802. 2021.
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  Strongly fluorescent halochromic 2,6-di-tert-butyl-phenol-functionalised phenyl-, thienyl- and furyl-substituted diketopyrrolopyrrole (DPP) dyes were deprotonated and oxidised to give either phenylene-linked DPP1˙˙ biradical (y0 = 0.75) with a singlet open shell ground state and a thermally populated triplet state (ΔEST = 19 meV; 1.8 kJ mol−1; 0.43 kcal mol−1) or thienylene/furylene-linked DPP2q and DPP3q compounds with closed shell quinoidal ground states. Accordingly, we identified the aromaticity of the conjugated (hetero-)aromatic bridge to be key for modulating the electronic character of these biradicaloid compounds and achieved a spin crossover from closed shell quinones DPP2q and DPP3q to open shell biradical DPP1˙˙ as confirmed by optical and magnetic spectroscopic studies (UV/vis/NIR, NMR, EPR) as well as computational investigations (spin-flip TD-DFT calculations in combination with CASSCF(4,4) and harmonic oscillator model of aromaticity (HOMA) analysis). Spectroelectrochemical studies and comproportionation experiments further prove the reversible formation of mixed-valent radical anions for the DPP2q and DPP3q quinoidal compounds with absorption bands edging into the NIR spectral region.

  @article{D0SC05475E, abstract = {Strongly fluorescent halochromic 2{,}6-di-tert-butyl-phenol-functionalised phenyl-{,} thienyl- and furyl-substituted diketopyrrolopyrrole (DPP) dyes were deprotonated and oxidised to give either phenylene-linked DPP1˙˙ biradical (y0 = 0.75) with a singlet open shell ground state and a thermally populated triplet state (ΔEST = 19 meV; 1.8 kJ mol−1; 0.43 kcal mol−1) or thienylene/furylene-linked DPP2q and DPP3q compounds with closed shell quinoidal ground states. Accordingly{,} we identified the aromaticity of the conjugated (hetero-)aromatic bridge to be key for modulating the electronic character of these biradicaloid compounds and achieved a spin crossover from closed shell quinones DPP2q and DPP3q to open shell biradical DPP1˙˙ as confirmed by optical and magnetic spectroscopic studies (UV/vis/NIR{,} NMR{,} EPR) as well as computational investigations (spin-flip TD-DFT calculations in combination with CASSCF(4{,}4) and harmonic oscillator model of aromaticity (HOMA) analysis). Spectroelectrochemical studies and comproportionation experiments further prove the reversible formation of mixed-valent radical anions for the DPP2q and DPP3q quinoidal compounds with absorption bands edging into the NIR spectral region.}, author = {Rausch, Rodger and Röhr, Merle I. S. and Schmidt, David and Krummenacher, Ivo and Braunschweig, Holger and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 2, pages = {793-802}, publisher = {The Royal Society of Chemistry}, title = {Tuning phenoxyl-substituted diketopyrrolopyrroles from quinoidal to biradical ground states through (hetero-)aromatic linkers}, volume = 12, year = 2021 }

  %0 Journal Article %1 D0SC05475E %A Rausch, Rodger %A Röhr, Merle I. S. %A Schmidt, David %A Krummenacher, Ivo %A Braunschweig, Holger %A Würthner, Frank %D 2021 %I The Royal Society of Chemistry %J Chem. Sci. %N 2 %P 793-802 %R 10.1039/D0SC05475E %T Tuning phenoxyl-substituted diketopyrrolopyrroles from quinoidal to biradical ground states through (hetero-)aromatic linkers %U http://dx.doi.org/10.1039/D0SC05475E %V 12 %X Strongly fluorescent halochromic 2,6-di-tert-butyl-phenol-functionalised phenyl-, thienyl- and furyl-substituted diketopyrrolopyrrole (DPP) dyes were deprotonated and oxidised to give either phenylene-linked DPP1˙˙ biradical (y0 = 0.75) with a singlet open shell ground state and a thermally populated triplet state (ΔEST = 19 meV; 1.8 kJ mol−1; 0.43 kcal mol−1) or thienylene/furylene-linked DPP2q and DPP3q compounds with closed shell quinoidal ground states. Accordingly, we identified the aromaticity of the conjugated (hetero-)aromatic bridge to be key for modulating the electronic character of these biradicaloid compounds and achieved a spin crossover from closed shell quinones DPP2q and DPP3q to open shell biradical DPP1˙˙ as confirmed by optical and magnetic spectroscopic studies (UV/vis/NIR, NMR, EPR) as well as computational investigations (spin-flip TD-DFT calculations in combination with CASSCF(4,4) and harmonic oscillator model of aromaticity (HOMA) analysis). Spectroelectrochemical studies and comproportionation experiments further prove the reversible formation of mixed-valent radical anions for the DPP2q and DPP3q quinoidal compounds with absorption bands edging into the NIR spectral region.
• Deracemization of Carbohelicenes by a Chiral Perylene Bisimide Cyclophane Template Catalyst. Weh, Manuel; Rühe, Jessica; Herbert, Benedikt; Krause, Ana-Maria; Würthner, Frank. In Angew. Chem. Int. Ed., 60(28), pp. 15323–15327. 2021.
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  Deracemization describes the conversion of a racemic mixture of a chiral molecule into an enantioenriched mixture or an enantiopure compound without structural modifications. Herein, we report an inherently chiral perylene bisimide (PBI) cyclophane whose chiral pocket is capable of transforming a racemic mixture of [5]-helicene into an enantioenriched mixture with an enantiomeric excess of 66 %. UV/Vis and fluorescence titration studies reveal this cyclophane host composed of two helically twisted PBI dyes has high binding affinities for the respective homochiral carbohelicene guests, with outstanding binding constants of up to 3.9×1010 m−1 for [4]-helicene. 2D NMR studies and single-crystal X-ray analysis demonstrate that the observed strong and enantioselective binding of homochiral carbohelicenes and the successful template-catalyzed deracemization of [5]-helicene can be explained by the enzyme-like perfect shape complementarity of the macrocyclic supramolecular host.

  @article{Weh_2021, abstract = {Deracemization describes the conversion of a racemic mixture of a chiral molecule into an enantioenriched mixture or an enantiopure compound without structural modifications. Herein, we report an inherently chiral perylene bisimide (PBI) cyclophane whose chiral pocket is capable of transforming a racemic mixture of [5]-helicene into an enantioenriched mixture with an enantiomeric excess of 66 %. UV/Vis and fluorescence titration studies reveal this cyclophane host composed of two helically twisted PBI dyes has high binding affinities for the respective homochiral carbohelicene guests, with outstanding binding constants of up to 3.9×1010 m−1 for [4]-helicene. 2D NMR studies and single-crystal X-ray analysis demonstrate that the observed strong and enantioselective binding of homochiral carbohelicenes and the successful template-catalyzed deracemization of [5]-helicene can be explained by the enzyme-like perfect shape complementarity of the macrocyclic supramolecular host.}, author = {Weh, Manuel and Rühe, Jessica and Herbert, Benedikt and Krause, Ana-Maria and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {06}, number = 28, pages = {15323–15327}, publisher = {Wiley}, title = {Deracemization of Carbohelicenes by a Chiral Perylene Bisimide Cyclophane Template Catalyst}, volume = 60, year = 2021 }

  %0 Journal Article %1 Weh_2021 %A Weh, Manuel %A Rühe, Jessica %A Herbert, Benedikt %A Krause, Ana-Maria %A Würthner, Frank %D 2021 %I Wiley %J Angew. Chem. Int. Ed. %N 28 %P 15323--15327 %R 10.1002/anie.202104591 %T Deracemization of Carbohelicenes by a Chiral Perylene Bisimide Cyclophane Template Catalyst %U https://doi.org/10.1002%2Fanie.202104591 %V 60 %X Deracemization describes the conversion of a racemic mixture of a chiral molecule into an enantioenriched mixture or an enantiopure compound without structural modifications. Herein, we report an inherently chiral perylene bisimide (PBI) cyclophane whose chiral pocket is capable of transforming a racemic mixture of [5]-helicene into an enantioenriched mixture with an enantiomeric excess of 66 %. UV/Vis and fluorescence titration studies reveal this cyclophane host composed of two helically twisted PBI dyes has high binding affinities for the respective homochiral carbohelicene guests, with outstanding binding constants of up to 3.9×1010 m−1 for [4]-helicene. 2D NMR studies and single-crystal X-ray analysis demonstrate that the observed strong and enantioselective binding of homochiral carbohelicenes and the successful template-catalyzed deracemization of [5]-helicene can be explained by the enzyme-like perfect shape complementarity of the macrocyclic supramolecular host.
• Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area. Renner, Rebecca; Mahlmeister, Bernhard; Anhalt, Olga; Stolte, Matthias; Würthner, Frank. In Chemistry A European Journal, 27(46), pp. 11997–12006. 2021.
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  A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol−1 for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol−1. The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.

  @article{Renner_2021, abstract = {A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol−1 for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol−1. The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.}, author = {Renner, Rebecca and Mahlmeister, Bernhard and Anhalt, Olga and Stolte, Matthias and Würthner, Frank}, journal = {Chemistry A European Journal}, keywords = {myown}, month = {07}, number = 46, pages = {11997–12006}, publisher = {Wiley}, title = {Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area}, volume = 27, year = 2021 }

  %0 Journal Article %1 Renner_2021 %A Renner, Rebecca %A Mahlmeister, Bernhard %A Anhalt, Olga %A Stolte, Matthias %A Würthner, Frank %D 2021 %I Wiley %J Chemistry A European Journal %N 46 %P 11997--12006 %R 10.1002/chem.202101877 %T Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area %U https://doi.org/10.1002%2Fchem.202101877 %V 27 %X A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol−1 for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol−1. The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.
• Folding and fluorescence enhancement with strong odd–even effect for a series of merocyanine dye oligomers. Hu, Xiaobo; Schulz, Alexander; Lindner, Joachim O.; Grüne, Matthias; Bialas, David; Würthner, Frank. In Chem. Sci., 12(24), pp. 8342–8352. 2021.
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  A series of merocyanine (MC) oligomers with a varying number of chromophores from two to six has been synthesized via a peptide synthesis strategy. Solvent-dependent UV/vis spectroscopic studies reveal folding processes for the MC oligomers driven by strong dipole–dipole interactions resulting in well-defined π-stacks with antiparallel orientation of the dyes. Whilst even-numbered tetramer 4 and hexamer 6 only show partial folding into dimeric units, odd-numbered trimer 3 and pentamer 5 fold into π-stacks of three and five MC units upon decreasing solvent polarity. In-depth 2D NMR studies provided insight into the supramolecular structure. For trimer 3, an NMR structure could be generated revealing the presence of a well-defined triple π-stack in the folded state. Concomitant with folding, the fluorescence quantum yield is increased for all MC oligomers in comparison to the single chromophore. Based on radiative and non-radiative decay rates, this fluorescence enhancement can be attributed to the rigidification of the chromophores within the π-stacks that affords a pronounced decrease of the non-radiative decay rates. Theoretical investigations for the double and triple dye stacks based on time-dependent density functional theory (TD-DFT) calculations indicate for trimer 3 a pronounced mixing of Frenkel and charge transfer (CT) states. This leads to significant deviations from the predictions obtained by the molecular exciton theory which only accounts for the Coulomb interaction between the transition dipole moments of the chromophores.

  @article{D1SC01678D, abstract = {A series of merocyanine (MC) oligomers with a varying number of chromophores from two to six has been synthesized via a peptide synthesis strategy. Solvent-dependent UV/vis spectroscopic studies reveal folding processes for the MC oligomers driven by strong dipole–dipole interactions resulting in well-defined π-stacks with antiparallel orientation of the dyes. Whilst even-numbered tetramer 4 and hexamer 6 only show partial folding into dimeric units{,} odd-numbered trimer 3 and pentamer 5 fold into π-stacks of three and five MC units upon decreasing solvent polarity. In-depth 2D NMR studies provided insight into the supramolecular structure. For trimer 3{,} an NMR structure could be generated revealing the presence of a well-defined triple π-stack in the folded state. Concomitant with folding{,} the fluorescence quantum yield is increased for all MC oligomers in comparison to the single chromophore. Based on radiative and non-radiative decay rates{,} this fluorescence enhancement can be attributed to the rigidification of the chromophores within the π-stacks that affords a pronounced decrease of the non-radiative decay rates. Theoretical investigations for the double and triple dye stacks based on time-dependent density functional theory (TD-DFT) calculations indicate for trimer 3 a pronounced mixing of Frenkel and charge transfer (CT) states. This leads to significant deviations from the predictions obtained by the molecular exciton theory which only accounts for the Coulomb interaction between the transition dipole moments of the chromophores.}, author = {Hu, Xiaobo and Schulz, Alexander and Lindner, Joachim O. and Grüne, Matthias and Bialas, David and Würthner, Frank}, journal = {Chem. Sci.}, keywords = {myown}, number = 24, pages = {8342-8352}, publisher = {The Royal Society of Chemistry}, title = {Folding and fluorescence enhancement with strong odd–even effect for a series of merocyanine dye oligomers}, volume = 12, year = 2021 }

  %0 Journal Article %1 D1SC01678D %A Hu, Xiaobo %A Schulz, Alexander %A Lindner, Joachim O. %A Grüne, Matthias %A Bialas, David %A Würthner, Frank %D 2021 %I The Royal Society of Chemistry %J Chem. Sci. %N 24 %P 8342-8352 %R 10.1039/D1SC01678D %T Folding and fluorescence enhancement with strong odd–even effect for a series of merocyanine dye oligomers %U http://dx.doi.org/10.1039/D1SC01678D %V 12 %X A series of merocyanine (MC) oligomers with a varying number of chromophores from two to six has been synthesized via a peptide synthesis strategy. Solvent-dependent UV/vis spectroscopic studies reveal folding processes for the MC oligomers driven by strong dipole–dipole interactions resulting in well-defined π-stacks with antiparallel orientation of the dyes. Whilst even-numbered tetramer 4 and hexamer 6 only show partial folding into dimeric units, odd-numbered trimer 3 and pentamer 5 fold into π-stacks of three and five MC units upon decreasing solvent polarity. In-depth 2D NMR studies provided insight into the supramolecular structure. For trimer 3, an NMR structure could be generated revealing the presence of a well-defined triple π-stack in the folded state. Concomitant with folding, the fluorescence quantum yield is increased for all MC oligomers in comparison to the single chromophore. Based on radiative and non-radiative decay rates, this fluorescence enhancement can be attributed to the rigidification of the chromophores within the π-stacks that affords a pronounced decrease of the non-radiative decay rates. Theoretical investigations for the double and triple dye stacks based on time-dependent density functional theory (TD-DFT) calculations indicate for trimer 3 a pronounced mixing of Frenkel and charge transfer (CT) states. This leads to significant deviations from the predictions obtained by the molecular exciton theory which only accounts for the Coulomb interaction between the transition dipole moments of the chromophores.

• Efficient Electronic Coupling in Perylenediimide Multilayered Films on Indium Tin Oxide. Silva, Barbara P. G.; Tosco, Bruna; de Florio, Daniel Z.; Stepanenko, Vladimir; Würthner, Frank; Rey, José Fernando Q.; Brochsztain, Sergio. In J. Phys. Chem. C., 124(10), pp. 5541–5551. 2020.
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  Layer-by-layer thin films with up to 11 layers of N,N′-bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI) were deposited on indium tin oxide (ITO) substrates by the zirconium phosphonate method. Film growth was studied by UV–visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). It was found that the films grow in a linear fashion, with the same amount of dye incorporated in each deposition cycle, and the dye molecules were π-stacked within the films. For a 10-layer film, film thickness was estimated as 20 nm, giving 2 nm per layer. Electrochemical characterization of the films was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV measurements showed that peak currents were proportional to the number of layers, for both the first and second reductions of PPDI. The effect of applied bias on the EIS response was studied in both the impedance (Bode plots) and capacitance (Cole–Cole plots) complex planes. The width of the semicircles in the Cole–Cole plots was proportional to the number of layers when the electrode was biased at −0.6 V, which is within the redox window for PPDI reduction. The pseudocapacitance of the films was obtained from the width of the semicircles, allowing the calculation of electroactive surface coverages and electron-transfer rates. Surface coverages of ca. 1 × 10–10 mol/cm2 per layer were obtained, whereas electron transfer rates decreased with film thickness, from 41 s–1 in a monolayer to 1.3 s–1 in a 10-layer film. The present study shows that compact PPDI films were formed, with efficient electronic coupling between the PPDI units, rendering the films attractive as electron transport layers for organic electronics.

  @article{Silva_2020, abstract = {Layer-by-layer thin films with up to 11 layers of N,N′-bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI) were deposited on indium tin oxide (ITO) substrates by the zirconium phosphonate method. Film growth was studied by UV–visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). It was found that the films grow in a linear fashion, with the same amount of dye incorporated in each deposition cycle, and the dye molecules were π-stacked within the films. For a 10-layer film, film thickness was estimated as 20 nm, giving 2 nm per layer. Electrochemical characterization of the films was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV measurements showed that peak currents were proportional to the number of layers, for both the first and second reductions of PPDI. The effect of applied bias on the EIS response was studied in both the impedance (Bode plots) and capacitance (Cole–Cole plots) complex planes. The width of the semicircles in the Cole–Cole plots was proportional to the number of layers when the electrode was biased at −0.6 V, which is within the redox window for PPDI reduction. The pseudocapacitance of the films was obtained from the width of the semicircles, allowing the calculation of electroactive surface coverages and electron-transfer rates. Surface coverages of ca. 1 × 10–10 mol/cm2 per layer were obtained, whereas electron transfer rates decreased with film thickness, from 41 s–1 in a monolayer to 1.3 s–1 in a 10-layer film. The present study shows that compact PPDI films were formed, with efficient electronic coupling between the PPDI units, rendering the films attractive as electron transport layers for organic electronics.}, author = {Silva, Barbara P. G. and Tosco, Bruna and de Florio, Daniel Z. and Stepanenko, Vladimir and Würthner, Frank and Rey, José Fernando Q. and Brochsztain, Sergio}, journal = {J. Phys. Chem. C.}, keywords = {myown}, month = {02}, number = 10, pages = {5541–5551}, publisher = {American Chemical Society (ACS)}, title = {Efficient Electronic Coupling in Perylenediimide Multilayered Films on Indium Tin Oxide}, volume = 124, year = 2020 }

  %0 Journal Article %1 Silva_2020 %A Silva, Barbara P. G. %A Tosco, Bruna %A de Florio, Daniel Z. %A Stepanenko, Vladimir %A Würthner, Frank %A Rey, José Fernando Q. %A Brochsztain, Sergio %D 2020 %I American Chemical Society (ACS) %J J. Phys. Chem. C. %N 10 %P 5541--5551 %R 10.1021/acs.jpcc.9b11373 %T Efficient Electronic Coupling in Perylenediimide Multilayered Films on Indium Tin Oxide %U https://doi.org/10.1021%2Facs.jpcc.9b11373 %V 124 %X Layer-by-layer thin films with up to 11 layers of N,N′-bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI) were deposited on indium tin oxide (ITO) substrates by the zirconium phosphonate method. Film growth was studied by UV–visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). It was found that the films grow in a linear fashion, with the same amount of dye incorporated in each deposition cycle, and the dye molecules were π-stacked within the films. For a 10-layer film, film thickness was estimated as 20 nm, giving 2 nm per layer. Electrochemical characterization of the films was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV measurements showed that peak currents were proportional to the number of layers, for both the first and second reductions of PPDI. The effect of applied bias on the EIS response was studied in both the impedance (Bode plots) and capacitance (Cole–Cole plots) complex planes. The width of the semicircles in the Cole–Cole plots was proportional to the number of layers when the electrode was biased at −0.6 V, which is within the redox window for PPDI reduction. The pseudocapacitance of the films was obtained from the width of the semicircles, allowing the calculation of electroactive surface coverages and electron-transfer rates. Surface coverages of ca. 1 × 10–10 mol/cm2 per layer were obtained, whereas electron transfer rates decreased with film thickness, from 41 s–1 in a monolayer to 1.3 s–1 in a 10-layer film. The present study shows that compact PPDI films were formed, with efficient electronic coupling between the PPDI units, rendering the films attractive as electron transport layers for organic electronics.
• Tracking Structural Evolution during Symmetry-Breaking Charge Separation in Quadrupolar Perylene Bisimide with Time-Resolved Impulsive Stimulated Raman Spectroscopy. Kim, Woojae; Kim, Taeyeon; Kang, Seongsoo; Hong, Yongseok; Würthner, Frank; Kim, Dongho. In Angew. Chem. Int. Ed., 59(22), pp. 8571–8578. 2020.
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  Elucidating structural roles in photoinduced charge transfer is indispensable, as nuclear rearrangements are simultaneously usually involved in the dynamics. However, it is hard to evaluate whether the structural changes occur or not by using conventional time‐resolved electronic spectroscopy. Here, time‐resolved impulsive stimulated Raman spectroscopy is applied to record the evolution of vibrational snapshots during charge‐separation dynamics of donor–acceptor–donor‐type quadrupolar perylene bisimide in real time. Drastic frequency shifts were observed for several Raman bands with their population kinetics, thus symmetry‐breaking charge separation accompanies significant structural changes, as supported by (TD)‐DFT calculations. A comparison between time‐resolved Raman spectra of the neutral S1 state and the radical anion species shows that the spectral signatures, especially in high‐frequency regions, provide important clues to bond length alternation patterns in the PBI core.

  @article{Kim_2020, abstract = {Elucidating structural roles in photoinduced charge transfer is indispensable, as nuclear rearrangements are simultaneously usually involved in the dynamics. However, it is hard to evaluate whether the structural changes occur or not by using conventional time‐resolved electronic spectroscopy. Here, time‐resolved impulsive stimulated Raman spectroscopy is applied to record the evolution of vibrational snapshots during charge‐separation dynamics of donor–acceptor–donor‐type quadrupolar perylene bisimide in real time. Drastic frequency shifts were observed for several Raman bands with their population kinetics, thus symmetry‐breaking charge separation accompanies significant structural changes, as supported by (TD)‐DFT calculations. A comparison between time‐resolved Raman spectra of the neutral S1 state and the radical anion species shows that the spectral signatures, especially in high‐frequency regions, provide important clues to bond length alternation patterns in the PBI core.}, author = {Kim, Woojae and Kim, Taeyeon and Kang, Seongsoo and Hong, Yongseok and Würthner, Frank and Kim, Dongho}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {04}, number = 22, pages = {8571–8578}, publisher = {Wiley}, title = {Tracking Structural Evolution during Symmetry-Breaking Charge Separation in Quadrupolar Perylene Bisimide with Time-Resolved Impulsive Stimulated Raman Spectroscopy}, volume = 59, year = 2020 }

  %0 Journal Article %1 Kim_2020 %A Kim, Woojae %A Kim, Taeyeon %A Kang, Seongsoo %A Hong, Yongseok %A Würthner, Frank %A Kim, Dongho %D 2020 %I Wiley %J Angew. Chem. Int. Ed. %N 22 %P 8571--8578 %R 10.1002/anie.202002733 %T Tracking Structural Evolution during Symmetry-Breaking Charge Separation in Quadrupolar Perylene Bisimide with Time-Resolved Impulsive Stimulated Raman Spectroscopy %U https://doi.org/10.1002%2Fanie.202002733 %V 59 %X Elucidating structural roles in photoinduced charge transfer is indispensable, as nuclear rearrangements are simultaneously usually involved in the dynamics. However, it is hard to evaluate whether the structural changes occur or not by using conventional time‐resolved electronic spectroscopy. Here, time‐resolved impulsive stimulated Raman spectroscopy is applied to record the evolution of vibrational snapshots during charge‐separation dynamics of donor–acceptor–donor‐type quadrupolar perylene bisimide in real time. Drastic frequency shifts were observed for several Raman bands with their population kinetics, thus symmetry‐breaking charge separation accompanies significant structural changes, as supported by (TD)‐DFT calculations. A comparison between time‐resolved Raman spectra of the neutral S1 state and the radical anion species shows that the spectral signatures, especially in high‐frequency regions, provide important clues to bond length alternation patterns in the PBI core.
• Naphthalene diimide-amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA. Weissenstein, Annike; Vysotsky, Myroslav O; Piantanida, Ivo; Würthner, Frank. In Beilstein J. Org. Chem., 16, pp. 2032–2045. 2020.
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  Two novel unnatural amino acids, prepared by linking a dicationic purple-coloured and fluorescent naphthalene diimide (NDI) at core position to amino acid side chains of variable length, strongly interacted with ds-DNA/RNA by threading intercalation. Different from a reference NDI dye with identical visible range absorbance (520–540 nm) and Stokes shifts in emission (+60 nm, quantum yield > 0.2), only these amino acid–NDI conjugates showed selective fluorimetric response for GC-DNA in respect to AT(U)-polynucleotides. The DNA/RNA binding-induced circular dichroism (ICD) response of NDI at 450–550 nm strongly depended on the length and rigidity of the linker to the amino acid unit, which controls the orientation of the NDI unit inside within the intercalative binding site. The ICD selectivity also depends on the type of polynucleotide, thus the studied NDI dyes act as dual fluorimetric/ICD probes for sensing the difference between here used GC-DNA, AT-DNA and AU-RNA.

  @article{Wei_enstein_2020, abstract = {Two novel unnatural amino acids, prepared by linking a dicationic purple-coloured and fluorescent naphthalene diimide (NDI) at core position to amino acid side chains of variable length, strongly interacted with ds-DNA/RNA by threading intercalation. Different from a reference NDI dye with identical visible range absorbance (520–540 nm) and Stokes shifts in emission (+60 nm, quantum yield > 0.2), only these amino acid–NDI conjugates showed selective fluorimetric response for GC-DNA in respect to AT(U)-polynucleotides. The DNA/RNA binding-induced circular dichroism (ICD) response of NDI at 450–550 nm strongly depended on the length and rigidity of the linker to the amino acid unit, which controls the orientation of the NDI unit inside within the intercalative binding site. The ICD selectivity also depends on the type of polynucleotide, thus the studied NDI dyes act as dual fluorimetric/ICD probes for sensing the difference between here used GC-DNA, AT-DNA and AU-RNA.}, author = {Weissenstein, Annike and Vysotsky, Myroslav O and Piantanida, Ivo and Würthner, Frank}, journal = {Beilstein J. Org. Chem.}, keywords = {myown}, month = {08}, pages = {2032–2045}, publisher = {Beilstein Institut}, title = {Naphthalene diimide-amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA}, volume = 16, year = 2020 }

  %0 Journal Article %1 Wei_enstein_2020 %A Weissenstein, Annike %A Vysotsky, Myroslav O %A Piantanida, Ivo %A Würthner, Frank %D 2020 %I Beilstein Institut %J Beilstein J. Org. Chem. %P 2032--2045 %R 10.3762/bjoc.16.170 %T Naphthalene diimide-amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA %U https://doi.org/10.3762%2Fbjoc.16.170 %V 16 %X Two novel unnatural amino acids, prepared by linking a dicationic purple-coloured and fluorescent naphthalene diimide (NDI) at core position to amino acid side chains of variable length, strongly interacted with ds-DNA/RNA by threading intercalation. Different from a reference NDI dye with identical visible range absorbance (520–540 nm) and Stokes shifts in emission (+60 nm, quantum yield > 0.2), only these amino acid–NDI conjugates showed selective fluorimetric response for GC-DNA in respect to AT(U)-polynucleotides. The DNA/RNA binding-induced circular dichroism (ICD) response of NDI at 450–550 nm strongly depended on the length and rigidity of the linker to the amino acid unit, which controls the orientation of the NDI unit inside within the intercalative binding site. The ICD selectivity also depends on the type of polynucleotide, thus the studied NDI dyes act as dual fluorimetric/ICD probes for sensing the difference between here used GC-DNA, AT-DNA and AU-RNA.
• Efficient Electrochemical Water Oxidation by a Trinuclear Ru(bda) Macrocycle Immobilized on Multi-Walled Carbon Nanotube Electrodes. Schindler, Dorothee; Gil-Sepulcre, Marcos; Lindner, Joachim O.; Stepanenko, Vladimir; Moonshiram, Dooshaye; Llobet, Antoni; Würthner, Frank. In Adv. Energy Mater., 10(43), p. 2002329. 2020.
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  Catalytic water splitting is a viable process for the generation of renewable fuels. Here it is reported for the first time that a trinuclear supramolecular Ru(bda) (bda: 2,2′‐bipyridine‐6,6′‐dicarboxylate) catalyst, anchored on multi‐walled carbon nanotubes and subsequently immobilized on glassy carbon electrodes, shows outstanding performance in heterogeneous water oxidation. Activation of the catalyst on anodes by repetitive cyclic voltammetry (CV) scans results in a catalytic current density of 186 mA cm−2 at a potential of 1.45 V versus NHE. The activated catalyst performs water oxidation at an onset overpotential of 330 mV. The remarkably high stability of the hybrid anode is demonstrated by X‐ray absorption spectroscopy and electrochemically, revealing the absence of any degradation after 1.8 million turnovers. Foot of the wave analysis of CV data of activated electrodes with different concentrations of catalyst indicates a monomolecular water nucleophilic attack mechanism with an apparent rate constant of TOFmax (turnover frequency) of 3200 s−1.

  @article{Schindler_2020, abstract = {Catalytic water splitting is a viable process for the generation of renewable fuels. Here it is reported for the first time that a trinuclear supramolecular Ru(bda) (bda: 2,2′‐bipyridine‐6,6′‐dicarboxylate) catalyst, anchored on multi‐walled carbon nanotubes and subsequently immobilized on glassy carbon electrodes, shows outstanding performance in heterogeneous water oxidation. Activation of the catalyst on anodes by repetitive cyclic voltammetry (CV) scans results in a catalytic current density of 186 mA cm−2 at a potential of 1.45 V versus NHE. The activated catalyst performs water oxidation at an onset overpotential of 330 mV. The remarkably high stability of the hybrid anode is demonstrated by X‐ray absorption spectroscopy and electrochemically, revealing the absence of any degradation after 1.8 million turnovers. Foot of the wave analysis of CV data of activated electrodes with different concentrations of catalyst indicates a monomolecular water nucleophilic attack mechanism with an apparent rate constant of TOFmax (turnover frequency) of 3200 s−1.}, author = {Schindler, Dorothee and Gil-Sepulcre, Marcos and Lindner, Joachim O. and Stepanenko, Vladimir and Moonshiram, Dooshaye and Llobet, Antoni and Würthner, Frank}, journal = {Adv. Energy Mater.}, keywords = {myown}, month = 10, number = 43, pages = 2002329, publisher = {Wiley}, title = {Efficient Electrochemical Water Oxidation by a Trinuclear Ru(bda) Macrocycle Immobilized on Multi-Walled Carbon Nanotube Electrodes}, volume = 10, year = 2020 }

  %0 Journal Article %1 Schindler_2020 %A Schindler, Dorothee %A Gil-Sepulcre, Marcos %A Lindner, Joachim O. %A Stepanenko, Vladimir %A Moonshiram, Dooshaye %A Llobet, Antoni %A Würthner, Frank %D 2020 %I Wiley %J Adv. Energy Mater. %N 43 %P 2002329 %R 10.1002/aenm.202002329 %T Efficient Electrochemical Water Oxidation by a Trinuclear Ru(bda) Macrocycle Immobilized on Multi-Walled Carbon Nanotube Electrodes %U https://doi.org/10.1002%2Faenm.202002329 %V 10 %X Catalytic water splitting is a viable process for the generation of renewable fuels. Here it is reported for the first time that a trinuclear supramolecular Ru(bda) (bda: 2,2′‐bipyridine‐6,6′‐dicarboxylate) catalyst, anchored on multi‐walled carbon nanotubes and subsequently immobilized on glassy carbon electrodes, shows outstanding performance in heterogeneous water oxidation. Activation of the catalyst on anodes by repetitive cyclic voltammetry (CV) scans results in a catalytic current density of 186 mA cm−2 at a potential of 1.45 V versus NHE. The activated catalyst performs water oxidation at an onset overpotential of 330 mV. The remarkably high stability of the hybrid anode is demonstrated by X‐ray absorption spectroscopy and electrochemically, revealing the absence of any degradation after 1.8 million turnovers. Foot of the wave analysis of CV data of activated electrodes with different concentrations of catalyst indicates a monomolecular water nucleophilic attack mechanism with an apparent rate constant of TOFmax (turnover frequency) of 3200 s−1.
• Synthesis of polycyclic aromatic hydrocarbons by palladium-catalysed [3 + 3] annulation. Pigulski, Bartłomiej; Ximenis, Marta; Shoyama, Kazutaka; Würthner, Frank. In Org. Chem. Front., 7(19), pp. 2925–2930. 2020.
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  Here we report a new palladium-catalysed [3 + 3] annulation method for the synthesis of polycyclic aromatic hydrocarbons (PAHs) from two smaller aromatic fragments. The successful application to various perylene derivatives is demonstrated based on optimized reaction conditions for the cross-coupling of 1,8-dibromonaphthalene and 4,5-dibromoacenaphthene with various PAH boronic esters. The reported synthetic protocols could be applied for curved and heteroaromatic substrates as well. The structure and packing arrangements of four products were confirmed by single crystal X-ray diffraction.

  @article{D0QO00968G, abstract = {Here we report a new palladium-catalysed [3 + 3] annulation method for the synthesis of polycyclic aromatic hydrocarbons (PAHs) from two smaller aromatic fragments. The successful application to various perylene derivatives is demonstrated based on optimized reaction conditions for the cross-coupling of 1{,}8-dibromonaphthalene and 4{,}5-dibromoacenaphthene with various PAH boronic esters. The reported synthetic protocols could be applied for curved and heteroaromatic substrates as well. The structure and packing arrangements of four products were confirmed by single crystal X-ray diffraction.}, author = {Pigulski, Bartłomiej and Ximenis, Marta and Shoyama, Kazutaka and Würthner, Frank}, journal = {Org. Chem. Front.}, keywords = {myown}, number = 19, pages = {2925-2930}, publisher = {The Royal Society of Chemistry}, title = {Synthesis of polycyclic aromatic hydrocarbons by palladium-catalysed [3 + 3] annulation}, volume = 7, year = 2020 }

  %0 Journal Article %1 D0QO00968G %A Pigulski, Bartłomiej %A Ximenis, Marta %A Shoyama, Kazutaka %A Würthner, Frank %D 2020 %I The Royal Society of Chemistry %J Org. Chem. Front. %N 19 %P 2925-2930 %R 10.1039/D0QO00968G %T Synthesis of polycyclic aromatic hydrocarbons by palladium-catalysed [3 + 3] annulation %U http://dx.doi.org/10.1039/D0QO00968G %V 7 %X Here we report a new palladium-catalysed [3 + 3] annulation method for the synthesis of polycyclic aromatic hydrocarbons (PAHs) from two smaller aromatic fragments. The successful application to various perylene derivatives is demonstrated based on optimized reaction conditions for the cross-coupling of 1,8-dibromonaphthalene and 4,5-dibromoacenaphthene with various PAH boronic esters. The reported synthetic protocols could be applied for curved and heteroaromatic substrates as well. The structure and packing arrangements of four products were confirmed by single crystal X-ray diffraction.
• Bowl-Shaped Naphthalimide-Annulated Corannulene as Nonfullerene Acceptor in Organic Solar Cells. Menekse, Kaan; Renner, Rebecca; Mahlmeister, Bernhard; Stolte, Matthias; Würthner, Frank. In Organic Materials, 02(03), pp. 229–234. 2020.
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  An electron-poor bowl-shaped naphthalimide-annulated corannulene with branched alkyl residues in the imide position was synthesized by a palladium-catalyzed cross-coupling annulation sequence. This dipolar compound exhibits strong absorption in the visible range along with a low-lying LUMO level at –3.85 eV, enabling n-type charge transport in organic thin-film transistors. Furthermore, we processed inverted bulk-heterojunction solar cells in combination with the two donor polymers PCE–10 and PM6 to achieve open-circuit voltages up to 1.04 V. By using a blend of the self-assembled naphthalimide-annulated corannulene and PCE–10, we were able to obtain a power conversion efficiency of up to 2.1%, which is to the best of our knowledge the highest reported value for a corannulene-based organic solar cell to date.

  @article{menekse2020bowlshaped, abstract = {An electron-poor bowl-shaped naphthalimide-annulated corannulene with branched alkyl residues in the imide position was synthesized by a palladium-catalyzed cross-coupling annulation sequence. This dipolar compound exhibits strong absorption in the visible range along with a low-lying LUMO level at –3.85 eV, enabling n-type charge transport in organic thin-film transistors. Furthermore, we processed inverted bulk-heterojunction solar cells in combination with the two donor polymers PCE–10 and PM6 to achieve open-circuit voltages up to 1.04 V. By using a blend of the self-assembled naphthalimide-annulated corannulene and PCE–10, we were able to obtain a power conversion efficiency of up to 2.1%, which is to the best of our knowledge the highest reported value for a corannulene-based organic solar cell to date.}, author = {Menekse, Kaan and Renner, Rebecca and Mahlmeister, Bernhard and Stolte, Matthias and Würthner, Frank}, journal = {Organic Materials}, keywords = {myown}, number = {03}, pages = {229-234}, title = {Bowl-Shaped Naphthalimide-Annulated Corannulene as Nonfullerene Acceptor in Organic Solar Cells}, volume = {02}, year = 2020 }

  %0 Journal Article %1 menekse2020bowlshaped %A Menekse, Kaan %A Renner, Rebecca %A Mahlmeister, Bernhard %A Stolte, Matthias %A Würthner, Frank %D 2020 %J Organic Materials %N 03 %P 229-234 %R 10.1055/s-0040-1714283 %T Bowl-Shaped Naphthalimide-Annulated Corannulene as Nonfullerene Acceptor in Organic Solar Cells %V 02 %X An electron-poor bowl-shaped naphthalimide-annulated corannulene with branched alkyl residues in the imide position was synthesized by a palladium-catalyzed cross-coupling annulation sequence. This dipolar compound exhibits strong absorption in the visible range along with a low-lying LUMO level at –3.85 eV, enabling n-type charge transport in organic thin-film transistors. Furthermore, we processed inverted bulk-heterojunction solar cells in combination with the two donor polymers PCE–10 and PM6 to achieve open-circuit voltages up to 1.04 V. By using a blend of the self-assembled naphthalimide-annulated corannulene and PCE–10, we were able to obtain a power conversion efficiency of up to 2.1%, which is to the best of our knowledge the highest reported value for a corannulene-based organic solar cell to date.
• Hydrogen bond-rigidified planar squaraine dye and its electronic and organic semiconductor properties. Maeda, Takeshi; Liess, Andreas; Kudzus, Astrid; Krause, Ana-Maria; Stolte, Matthias; Amitani, Hitoshi; Yagi, Shigeyuki; Fujiwara, Hideki; Würthner, Frank. In Chem. Commun., 56(68), pp. 9890–9893. 2020.
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  The one-step reaction of a dicyanovinyl-functionalized squaric acid with Fischer bases afforded C2v symmetric squaraine dyes with rigid planar structures due to intramolecular N–H⋯O hydrogen bonds. Dense molecular packing, decrease of HOMO level, and sufficient thermal stability for sublimation enabled vacuum-processed OTFTs with hole mobility up to 0.32 cm2 V−1 s−1 and current on/off ratio of 106.

  @article{D0CC04306K, abstract = {The one-step reaction of a dicyanovinyl-functionalized squaric acid with Fischer bases afforded C2v symmetric squaraine dyes with rigid planar structures due to intramolecular N–H⋯O hydrogen bonds. Dense molecular packing{,} decrease of HOMO level{,} and sufficient thermal stability for sublimation enabled vacuum-processed OTFTs with hole mobility up to 0.32 cm2 V−1 s−1 and current on/off ratio of 106.}, author = {Maeda, Takeshi and Liess, Andreas and Kudzus, Astrid and Krause, Ana-Maria and Stolte, Matthias and Amitani, Hitoshi and Yagi, Shigeyuki and Fujiwara, Hideki and Würthner, Frank}, journal = {Chem. Commun.}, keywords = {myown}, number = 68, pages = {9890-9893}, publisher = {The Royal Society of Chemistry}, title = {Hydrogen bond-rigidified planar squaraine dye and its electronic and organic semiconductor properties}, volume = 56, year = 2020 }

  %0 Journal Article %1 D0CC04306K %A Maeda, Takeshi %A Liess, Andreas %A Kudzus, Astrid %A Krause, Ana-Maria %A Stolte, Matthias %A Amitani, Hitoshi %A Yagi, Shigeyuki %A Fujiwara, Hideki %A Würthner, Frank %D 2020 %I The Royal Society of Chemistry %J Chem. Commun. %N 68 %P 9890-9893 %R 10.1039/D0CC04306K %T Hydrogen bond-rigidified planar squaraine dye and its electronic and organic semiconductor properties %U http://dx.doi.org/10.1039/D0CC04306K %V 56 %X The one-step reaction of a dicyanovinyl-functionalized squaric acid with Fischer bases afforded C2v symmetric squaraine dyes with rigid planar structures due to intramolecular N–H⋯O hydrogen bonds. Dense molecular packing, decrease of HOMO level, and sufficient thermal stability for sublimation enabled vacuum-processed OTFTs with hole mobility up to 0.32 cm2 V−1 s−1 and current on/off ratio of 106.
• NIR-Absorbing π-Extended Azulene: Non-Alternant Isomer of Terrylene Bisimide. Pigulski, Bart\lomiej; Shoyama, Kazutaka; Würthner, Frank. In Angew. Chem. Int. Ed. 2020.
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  The first planar π‐extended azulene that retains aromaticity of odd‐membered rings was synthesized by [3+3] peri‐annulation of two naphthalene imides at both long‐edge sides of azulene. Using bromination and subsequent nucleophilic substitution by methoxide and morpholine, selective functionalization of the π‐extended azulene was achieved. Whilst these new azulenes can be regarded as isomers of terrylene bisimide they exhibit entirely different properties, which include very narrow optical and electrochemical gaps. DFT, TD‐DFT, as well as nucleus‐independent chemical shift calculations were applied to explain the structural and functional properties of these new π scaffolds. Furthermore, X‐ray crystallography confirmed the planarity of the reported π‐scaffolds and aromaticity of their azulene moiety.

  @article{Pigulski_2020, abstract = {The first planar π‐extended azulene that retains aromaticity of odd‐membered rings was synthesized by [3+3] peri‐annulation of two naphthalene imides at both long‐edge sides of azulene. Using bromination and subsequent nucleophilic substitution by methoxide and morpholine, selective functionalization of the π‐extended azulene was achieved. Whilst these new azulenes can be regarded as isomers of terrylene bisimide they exhibit entirely different properties, which include very narrow optical and electrochemical gaps. DFT, TD‐DFT, as well as nucleus‐independent chemical shift calculations were applied to explain the structural and functional properties of these new π scaffolds. Furthermore, X‐ray crystallography confirmed the planarity of the reported π‐scaffolds and aromaticity of their azulene moiety.}, author = {Pigulski, Bart{\l}omiej and Shoyama, Kazutaka and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {06}, publisher = {Wiley}, title = {NIR-Absorbing π-Extended Azulene: Non-Alternant Isomer of Terrylene Bisimide}, year = 2020 }

  %0 Journal Article %1 Pigulski_2020 %A Pigulski, Bart\lomiej %A Shoyama, Kazutaka %A Würthner, Frank %D 2020 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202005376 %T NIR-Absorbing π-Extended Azulene: Non-Alternant Isomer of Terrylene Bisimide %U https://doi.org/10.1002%2Fanie.202005376 %X The first planar π‐extended azulene that retains aromaticity of odd‐membered rings was synthesized by [3+3] peri‐annulation of two naphthalene imides at both long‐edge sides of azulene. Using bromination and subsequent nucleophilic substitution by methoxide and morpholine, selective functionalization of the π‐extended azulene was achieved. Whilst these new azulenes can be regarded as isomers of terrylene bisimide they exhibit entirely different properties, which include very narrow optical and electrochemical gaps. DFT, TD‐DFT, as well as nucleus‐independent chemical shift calculations were applied to explain the structural and functional properties of these new π scaffolds. Furthermore, X‐ray crystallography confirmed the planarity of the reported π‐scaffolds and aromaticity of their azulene moiety.
• Perylene Bisimide Cyclophanes: Structure–Property Relationships upon Variation of the Cavity Size. Rühe, Jessica; Bialas, David; Spenst, Peter; Krause, Ana-Maria; Würthner, Frank. In Organic Materials, 2, pp. 149–158. 2020.
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  Five cyclophanes composed of two perylene bisimide (PBI)dyes and various CH2–arylene–CH2linker units were synthesized. PM6-D3H4 geometry-optimized structures and a single crystal for one ofthese cyclophanes reveal well-defined distances between the twocoplanar PBI units in these cyclophanes, spanning the range from 5.0 to12.5 Å. UV/vis absorption spectra reveal a redistribution of oscillatorstrength of the vibronic bands due to a H-type exciton coupling even forthe cyclophane with the largest interchromophoric distance. Aquantitative evaluation according to the Kasha–Spano theory affordsexciton coupling strengths ranging from 64 cm�1for the largestcyclophane up to 333 cm�1for the smallest one and a surprisingly goodfit to the cubic interchromophoric distance in the framework of thepoint-dipole approximation. Interchromophoric interaction is alsonoticed influorescence lifetimes that are significantly increased forallfive cyclophanes as expected for H-coupled chromophores due to adecrease of the radiative rate. For the three largest cyclophanes withinterchromophoric distances of>9Å,fluorescence quantum yieldsremain high in chloroform (>88%), whilst for the smaller ones withinterchromophoric distances<6 Å, additional nonradiative pathwayslead to a pronouncedfluorescence quenching.

  @article{ruhe2020perylene, abstract = {Five cyclophanes composed of two perylene bisimide (PBI)dyes and various CH2–arylene–CH2linker units were synthesized. PM6-D3H4 geometry-optimized structures and a single crystal for one ofthese cyclophanes reveal well-defined distances between the twocoplanar PBI units in these cyclophanes, spanning the range from 5.0 to12.5 Å. UV/vis absorption spectra reveal a redistribution of oscillatorstrength of the vibronic bands due to a H-type exciton coupling even forthe cyclophane with the largest interchromophoric distance. Aquantitative evaluation according to the Kasha–Spano theory affordsexciton coupling strengths ranging from 64 cm�1for the largestcyclophane up to 333 cm�1for the smallest one and a surprisingly goodfit to the cubic interchromophoric distance in the framework of thepoint-dipole approximation. Interchromophoric interaction is alsonoticed influorescence lifetimes that are significantly increased forallfive cyclophanes as expected for H-coupled chromophores due to adecrease of the radiative rate. For the three largest cyclophanes withinterchromophoric distances of>9Å,fluorescence quantum yieldsremain high in chloroform (>88%), whilst for the smaller ones withinterchromophoric distances<6 Å, additional nonradiative pathwayslead to a pronouncedfluorescence quenching.}, author = {Rühe, Jessica and Bialas, David and Spenst, Peter and Krause, Ana-Maria and Würthner, Frank}, journal = {Organic Materials}, keywords = {myown}, month = {04}, pages = {149-158}, title = {Perylene Bisimide Cyclophanes: Structure–Property Relationships upon Variation of the Cavity Size}, volume = 2, year = 2020 }

  %0 Journal Article %1 ruhe2020perylene %A Rühe, Jessica %A Bialas, David %A Spenst, Peter %A Krause, Ana-Maria %A Würthner, Frank %D 2020 %J Organic Materials %P 149-158 %R 10.1055/s-0040-1709998 %T Perylene Bisimide Cyclophanes: Structure–Property Relationships upon Variation of the Cavity Size %U https://www.thieme-connect.de/products/ejournals/abstract/10.1055/s-0040-1709998 %V 2 %X Five cyclophanes composed of two perylene bisimide (PBI)dyes and various CH2–arylene–CH2linker units were synthesized. PM6-D3H4 geometry-optimized structures and a single crystal for one ofthese cyclophanes reveal well-defined distances between the twocoplanar PBI units in these cyclophanes, spanning the range from 5.0 to12.5 Å. UV/vis absorption spectra reveal a redistribution of oscillatorstrength of the vibronic bands due to a H-type exciton coupling even forthe cyclophane with the largest interchromophoric distance. Aquantitative evaluation according to the Kasha–Spano theory affordsexciton coupling strengths ranging from 64 cm�1for the largestcyclophane up to 333 cm�1for the smallest one and a surprisingly goodfit to the cubic interchromophoric distance in the framework of thepoint-dipole approximation. Interchromophoric interaction is alsonoticed influorescence lifetimes that are significantly increased forallfive cyclophanes as expected for H-coupled chromophores due to adecrease of the radiative rate. For the three largest cyclophanes withinterchromophoric distances of>9Å,fluorescence quantum yieldsremain high in chloroform (>88%), whilst for the smaller ones withinterchromophoric distances<6 Å, additional nonradiative pathwayslead to a pronouncedfluorescence quenching.
• Trapped Exciton and Large Birefringence in Cl2–NDI Revealed by Optical Spectroscopy. Pinteric, Marko; Roh, Seulki; Uykur, Ece; Hansen, Nis Hauke; Pflaum, Jens; Stolte, Matthias; Würthner, Frank; Dressel, Martin. In The Journal of Physical Chemistry C, 124(32), pp. 17829–17835. 2020.
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  The n-type organic semiconductor, β-phase single crystalline dichloro naphthalene diimide, Cl2–NDI, is investigated in a broad frequency range via optical spectroscopy. The temperature-dependent absorbance spectra reveal the appearance of new molecular vibration modes; several of them exhibit a pronounced splitting and abnormal red shift. In the visible spectral range, we observe a splitting of the J-band upon cooling, which we attributed to self-trapped excitons via coupling between free excitons and molecular vibrations or trapping by disorder induced Lévy states. Additionally, we discover a strong birefringence of these crystals by pronounced polarization beat over a wide frequency range.

  @article{Pinteri__2020, abstract = {The n-type organic semiconductor, β-phase single crystalline dichloro naphthalene diimide, Cl2–NDI, is investigated in a broad frequency range via optical spectroscopy. The temperature-dependent absorbance spectra reveal the appearance of new molecular vibration modes; several of them exhibit a pronounced splitting and abnormal red shift. In the visible spectral range, we observe a splitting of the J-band upon cooling, which we attributed to self-trapped excitons via coupling between free excitons and molecular vibrations or trapping by disorder induced Lévy states. Additionally, we discover a strong birefringence of these crystals by pronounced polarization beat over a wide frequency range.}, author = {Pinteric, Marko and Roh, Seulki and Uykur, Ece and Hansen, Nis Hauke and Pflaum, Jens and Stolte, Matthias and Würthner, Frank and Dressel, Martin}, journal = {The Journal of Physical Chemistry C}, keywords = {myown}, month = {07}, number = 32, pages = {17829–17835}, publisher = {American Chemical Society ({ACS})}, title = {Trapped Exciton and Large Birefringence in Cl2–NDI Revealed by Optical Spectroscopy}, volume = 124, year = 2020 }

  %0 Journal Article %1 Pinteri__2020 %A Pinteric, Marko %A Roh, Seulki %A Uykur, Ece %A Hansen, Nis Hauke %A Pflaum, Jens %A Stolte, Matthias %A Würthner, Frank %A Dressel, Martin %D 2020 %I American Chemical Society (ACS) %J The Journal of Physical Chemistry C %N 32 %P 17829--17835 %R 10.1021/acs.jpcc.0c05165 %T Trapped Exciton and Large Birefringence in Cl2–NDI Revealed by Optical Spectroscopy %U https://doi.org/10.1021%2Facs.jpcc.0c05165 %V 124 %X The n-type organic semiconductor, β-phase single crystalline dichloro naphthalene diimide, Cl2–NDI, is investigated in a broad frequency range via optical spectroscopy. The temperature-dependent absorbance spectra reveal the appearance of new molecular vibration modes; several of them exhibit a pronounced splitting and abnormal red shift. In the visible spectral range, we observe a splitting of the J-band upon cooling, which we attributed to self-trapped excitons via coupling between free excitons and molecular vibrations or trapping by disorder induced Lévy states. Additionally, we discover a strong birefringence of these crystals by pronounced polarization beat over a wide frequency range.
• Nanoscale Columnar Bundles Based on Multistranded Core-Shell Liquid Crystals of Perylene Bisimide J-Aggregate Donor-Acceptor Dyads for Photoconductivity Devices with Enhanced Performance Through Macroscopic Alignment. Hecht, Markus; Schlossarek, Tim; Ghosh, Samrat; Tsutsui, Yusuke; Schmiedel, Alexander; Holzapfel, Marco; Stolte, Matthias; Lambert, Christoph; Seki, Shu; Lehmann, Matthias; Würthner, Frank. In Appl. Nano Mater., 3(10), pp. 10234–10245. 2020.
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  Donor–acceptor dyads consisting of perylene bisimide (PBI) and trialkoxyphenyl–oligothiophene (TAPOT) units are reported that self-assemble into helical four-, six-, and seven-stranded hydrogen-bonded supramolecular polymers in solution and the columnar liquid-crystalline state. It is shown that the number of closely stacked and J-coupled PBI strands can be controlled by the incremental extension of the TAPOT wedge units in the bay position and the thereby tailored steric demand. Narcissistic self-sorting of TAPOT donor and PBI acceptor subunits facilitates the formation of core–shell structures creating individual percolation pathways for one-dimensional (1D) transport of photogenerated charge carriers. Macroscopic alignment of the nanoscale columnar structures by solution shearing enables anisotropic photoconductivity. Thus, selective orientation of the 1D charge-transporting domains parallel and perpendicular to the electrodes gives rise to an up to 90-fold increased photoresponse depending on the alignment quality. The intrinsic charge-separation and -transport properties were investigated by femtosecond transient absorption spectroscopy and flash-photolysis time-resolved microwave conductivity. These studies reveal a rising propensity for charge separation and transport upon increasing the conjugation length of the TAPOT donor and thereby increasing the size of the individual percolation pathways. Contrasting observations for intrinsic and macroscopic photoconductivities demonstrate the importance of processability in device performance.

  @article{Hecht_2020, abstract = {Donor–acceptor dyads consisting of perylene bisimide (PBI) and trialkoxyphenyl–oligothiophene (TAPOT) units are reported that self-assemble into helical four-, six-, and seven-stranded hydrogen-bonded supramolecular polymers in solution and the columnar liquid-crystalline state. It is shown that the number of closely stacked and J-coupled PBI strands can be controlled by the incremental extension of the TAPOT wedge units in the bay position and the thereby tailored steric demand. Narcissistic self-sorting of TAPOT donor and PBI acceptor subunits facilitates the formation of core–shell structures creating individual percolation pathways for one-dimensional (1D) transport of photogenerated charge carriers. Macroscopic alignment of the nanoscale columnar structures by solution shearing enables anisotropic photoconductivity. Thus, selective orientation of the 1D charge-transporting domains parallel and perpendicular to the electrodes gives rise to an up to 90-fold increased photoresponse depending on the alignment quality. The intrinsic charge-separation and -transport properties were investigated by femtosecond transient absorption spectroscopy and flash-photolysis time-resolved microwave conductivity. These studies reveal a rising propensity for charge separation and transport upon increasing the conjugation length of the TAPOT donor and thereby increasing the size of the individual percolation pathways. Contrasting observations for intrinsic and macroscopic photoconductivities demonstrate the importance of processability in device performance.}, author = {Hecht, Markus and Schlossarek, Tim and Ghosh, Samrat and Tsutsui, Yusuke and Schmiedel, Alexander and Holzapfel, Marco and Stolte, Matthias and Lambert, Christoph and Seki, Shu and Lehmann, Matthias and Würthner, Frank}, journal = {Appl. Nano Mater.}, keywords = {myown}, month = {09}, number = 10, pages = {10234–10245}, publisher = {American Chemical Society (ACS)}, title = {Nanoscale Columnar Bundles Based on Multistranded Core-Shell Liquid Crystals of Perylene Bisimide J-Aggregate Donor-Acceptor Dyads for Photoconductivity Devices with Enhanced Performance Through Macroscopic Alignment}, volume = 3, year = 2020 }

  %0 Journal Article %1 Hecht_2020 %A Hecht, Markus %A Schlossarek, Tim %A Ghosh, Samrat %A Tsutsui, Yusuke %A Schmiedel, Alexander %A Holzapfel, Marco %A Stolte, Matthias %A Lambert, Christoph %A Seki, Shu %A Lehmann, Matthias %A Würthner, Frank %D 2020 %I American Chemical Society (ACS) %J Appl. Nano Mater. %N 10 %P 10234--10245 %R 10.1021/acsanm.0c02189 %T Nanoscale Columnar Bundles Based on Multistranded Core-Shell Liquid Crystals of Perylene Bisimide J-Aggregate Donor-Acceptor Dyads for Photoconductivity Devices with Enhanced Performance Through Macroscopic Alignment %U https://doi.org/10.1021%2Facsanm.0c02189 %V 3 %X Donor–acceptor dyads consisting of perylene bisimide (PBI) and trialkoxyphenyl–oligothiophene (TAPOT) units are reported that self-assemble into helical four-, six-, and seven-stranded hydrogen-bonded supramolecular polymers in solution and the columnar liquid-crystalline state. It is shown that the number of closely stacked and J-coupled PBI strands can be controlled by the incremental extension of the TAPOT wedge units in the bay position and the thereby tailored steric demand. Narcissistic self-sorting of TAPOT donor and PBI acceptor subunits facilitates the formation of core–shell structures creating individual percolation pathways for one-dimensional (1D) transport of photogenerated charge carriers. Macroscopic alignment of the nanoscale columnar structures by solution shearing enables anisotropic photoconductivity. Thus, selective orientation of the 1D charge-transporting domains parallel and perpendicular to the electrodes gives rise to an up to 90-fold increased photoresponse depending on the alignment quality. The intrinsic charge-separation and -transport properties were investigated by femtosecond transient absorption spectroscopy and flash-photolysis time-resolved microwave conductivity. These studies reveal a rising propensity for charge separation and transport upon increasing the conjugation length of the TAPOT donor and thereby increasing the size of the individual percolation pathways. Contrasting observations for intrinsic and macroscopic photoconductivities demonstrate the importance of processability in device performance.
• On the photophysical properties of IrIII, PtII, and PdII (phenylpyrazole) (phenyldipyrrin) complexes. Föller, Jelena; Friese, Daniel H.; Riese, Stefan; Kaminski, Jeremy M.; Metz, Simon; Schmidt, David; Würthner, Frank; Lambert, Christoph; Marian, Christel M. In Phys. Chem. Chem. Phys., 22(6), pp. 3217–3233. 2020.
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  The absorption and emission characteristics of (ppz)2(dipy)IrIII, (ppz)(dipy)PtII and (ppz)(dipy)PdII, where ppz stands for phenylpyrazole and dipy for a phenyl meso-substituted dipyrrin ligand, have been investigated by means of combined density functional theory and multireference configuration interaction including scalar relativistic and spin–orbit coupling effects. These results were compared with experimental spectra. The complexes exhibit a high density of low-lying electronically excited states originating from ligand-centered (LC) and metal-to-ligand charge transfer (MLCT) states involving the dipyrrin ligand. In addition, metal-centered (MC) states are found to be low-lying in the Pd complex. In all three cases, the first strong absorption band and the phosphorescence emission band stem from LC excitations on the dipyrrin ligand with small MLCT contributions. The MLCT states show more pronounced relaxation effects than the LC states, with the consequence that the first excited state with predominant singlet multiplicity is of SMLCT/LC type in the heavier Ir and Pt complexes. Substantial spin–orbit coupling between SMLCT/LC and TLC enables fast and efficient intersystem crossing (ISC) and a high triplet quantum yield. Phosphorescence rate constants are rather small in accord with the dominant LC character of the transitions. Out-of-plane distortion promotes nonradiative decay of the excited state population via the MC states thus explaining the lower phosphorescence quantum yield of the Pt complex. The spectral properties of the Pd complex are different in many aspects. Optimization of the S1 state yields a dipyrrin intraligand charge transfer (ILCT) state with highly distorted nuclear arrangement in the butterfly conformers leading to nonradiative deactivation. In contrast, the primarily excited SLC state and the SMLCT/LC state of the twist conformer have nearly equal adiabatic excitation energies. The lack of a driving force toward the SMLCT/LC minimum, the high fluorescence rate constant of the bright SLC state and its moderately efficient ISC to the triplet manifold explain the experimentally observed dual emission of the Pd complex at room temperature.

  @article{C9CP05603C, abstract = {The absorption and emission characteristics of (ppz)2(dipy)IrIII, (ppz)(dipy)PtII and (ppz)(dipy)PdII, where ppz stands for phenylpyrazole and dipy for a phenyl meso-substituted dipyrrin ligand, have been investigated by means of combined density functional theory and multireference configuration interaction including scalar relativistic and spin–orbit coupling effects. These results were compared with experimental spectra. The complexes exhibit a high density of low-lying electronically excited states originating from ligand-centered (LC) and metal-to-ligand charge transfer (MLCT) states involving the dipyrrin ligand. In addition, metal-centered (MC) states are found to be low-lying in the Pd complex. In all three cases, the first strong absorption band and the phosphorescence emission band stem from LC excitations on the dipyrrin ligand with small MLCT contributions. The MLCT states show more pronounced relaxation effects than the LC states, with the consequence that the first excited state with predominant singlet multiplicity is of SMLCT/LC type in the heavier Ir and Pt complexes. Substantial spin–orbit coupling between SMLCT/LC and TLC enables fast and efficient intersystem crossing (ISC) and a high triplet quantum yield. Phosphorescence rate constants are rather small in accord with the dominant LC character of the transitions. Out-of-plane distortion promotes nonradiative decay of the excited state population via the MC states thus explaining the lower phosphorescence quantum yield of the Pt complex. The spectral properties of the Pd complex are different in many aspects. Optimization of the S1 state yields a dipyrrin intraligand charge transfer (ILCT) state with highly distorted nuclear arrangement in the butterfly conformers leading to nonradiative deactivation. In contrast, the primarily excited SLC state and the SMLCT/LC state of the twist conformer have nearly equal adiabatic excitation energies. The lack of a driving force toward the SMLCT/LC minimum, the high fluorescence rate constant of the bright SLC state and its moderately efficient ISC to the triplet manifold explain the experimentally observed dual emission of the Pd complex at room temperature.}, author = {Föller, Jelena and Friese, Daniel H. and Riese, Stefan and Kaminski, Jeremy M. and Metz, Simon and Schmidt, David and Würthner, Frank and Lambert, Christoph and Marian, Christel M.}, journal = {Phys. Chem. Chem. Phys.}, keywords = {myown}, number = 6, pages = {3217-3233}, publisher = {The Royal Society of Chemistry}, title = {On the photophysical properties of IrIII, PtII, and PdII (phenylpyrazole) (phenyldipyrrin) complexes}, volume = 22, year = 2020 }

  %0 Journal Article %1 C9CP05603C %A Föller, Jelena %A Friese, Daniel H. %A Riese, Stefan %A Kaminski, Jeremy M. %A Metz, Simon %A Schmidt, David %A Würthner, Frank %A Lambert, Christoph %A Marian, Christel M. %D 2020 %I The Royal Society of Chemistry %J Phys. Chem. Chem. Phys. %N 6 %P 3217-3233 %R 10.1039/C9CP05603C %T On the photophysical properties of IrIII, PtII, and PdII (phenylpyrazole) (phenyldipyrrin) complexes %U http://dx.doi.org/10.1039/C9CP05603C %V 22 %X The absorption and emission characteristics of (ppz)2(dipy)IrIII, (ppz)(dipy)PtII and (ppz)(dipy)PdII, where ppz stands for phenylpyrazole and dipy for a phenyl meso-substituted dipyrrin ligand, have been investigated by means of combined density functional theory and multireference configuration interaction including scalar relativistic and spin–orbit coupling effects. These results were compared with experimental spectra. The complexes exhibit a high density of low-lying electronically excited states originating from ligand-centered (LC) and metal-to-ligand charge transfer (MLCT) states involving the dipyrrin ligand. In addition, metal-centered (MC) states are found to be low-lying in the Pd complex. In all three cases, the first strong absorption band and the phosphorescence emission band stem from LC excitations on the dipyrrin ligand with small MLCT contributions. The MLCT states show more pronounced relaxation effects than the LC states, with the consequence that the first excited state with predominant singlet multiplicity is of SMLCT/LC type in the heavier Ir and Pt complexes. Substantial spin–orbit coupling between SMLCT/LC and TLC enables fast and efficient intersystem crossing (ISC) and a high triplet quantum yield. Phosphorescence rate constants are rather small in accord with the dominant LC character of the transitions. Out-of-plane distortion promotes nonradiative decay of the excited state population via the MC states thus explaining the lower phosphorescence quantum yield of the Pt complex. The spectral properties of the Pd complex are different in many aspects. Optimization of the S1 state yields a dipyrrin intraligand charge transfer (ILCT) state with highly distorted nuclear arrangement in the butterfly conformers leading to nonradiative deactivation. In contrast, the primarily excited SLC state and the SMLCT/LC state of the twist conformer have nearly equal adiabatic excitation energies. The lack of a driving force toward the SMLCT/LC minimum, the high fluorescence rate constant of the bright SLC state and its moderately efficient ISC to the triplet manifold explain the experimentally observed dual emission of the Pd complex at room temperature.
• Consecutive Charging of a Perylene Bisimide Dye by Multistep Low-Energy Solar-Light-Induced Electron Transfer Towards H 2 Evolution. Xu, Yucheng; Zheng, Jiaxin; Lindner, Joachim O.; Wen, Xinbo; Jiang, Nianqiang; Hu, Zhicheng; Liu, Linlin; Huang, Fei; Würthner, Frank; Xie, Zengqi. In Angew. Chem. Int. Ed., 59(26), pp. 10363–10367. 2020.
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  A photocatalytic system containing a perylene bisimide (PBI) dye as a photosensitizer anchored to titanium dioxide (TiO2) nanoparticles through carboxyl groups was constructed. Under solar‐light irradiation in the presence of sacrificial triethanolamine (TEOA) in neutral and basic conditions (pH 8.5), a reaction cascade is initiated in which the PBI molecule first absorbs green light, giving the formation of a stable radical anion (PBI.−), which in a second step absorbs near‐infrared light, forming a stable PBI dianion (PBI2−). Finally, the dianion absorbs red light and injects an electron into the TiO2 nanoparticle that is coated with platinum co‐catalyst for hydrogen evolution. The hydrogen evolution rates (HERs) are as high as 1216 and 1022 μmol h−1 g−1 with simulated sunlight irradiation in neutral and basic conditions, respectively.

  @article{Xu_2020, abstract = {A photocatalytic system containing a perylene bisimide (PBI) dye as a photosensitizer anchored to titanium dioxide (TiO2) nanoparticles through carboxyl groups was constructed. Under solar‐light irradiation in the presence of sacrificial triethanolamine (TEOA) in neutral and basic conditions (pH 8.5), a reaction cascade is initiated in which the PBI molecule first absorbs green light, giving the formation of a stable radical anion (PBI.−), which in a second step absorbs near‐infrared light, forming a stable PBI dianion (PBI2−). Finally, the dianion absorbs red light and injects an electron into the TiO2 nanoparticle that is coated with platinum co‐catalyst for hydrogen evolution. The hydrogen evolution rates (HERs) are as high as 1216 and 1022 μmol h−1 g−1 with simulated sunlight irradiation in neutral and basic conditions, respectively.}, author = {Xu, Yucheng and Zheng, Jiaxin and Lindner, Joachim O. and Wen, Xinbo and Jiang, Nianqiang and Hu, Zhicheng and Liu, Linlin and Huang, Fei and Würthner, Frank and Xie, Zengqi}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {04}, number = 26, pages = {10363–10367}, publisher = {Wiley}, title = {Consecutive Charging of a Perylene Bisimide Dye by Multistep Low-Energy Solar-Light-Induced Electron Transfer Towards H 2 Evolution}, volume = 59, year = 2020 }

  %0 Journal Article %1 Xu_2020 %A Xu, Yucheng %A Zheng, Jiaxin %A Lindner, Joachim O. %A Wen, Xinbo %A Jiang, Nianqiang %A Hu, Zhicheng %A Liu, Linlin %A Huang, Fei %A Würthner, Frank %A Xie, Zengqi %D 2020 %I Wiley %J Angew. Chem. Int. Ed. %N 26 %P 10363--10367 %R 10.1002/anie.202001231 %T Consecutive Charging of a Perylene Bisimide Dye by Multistep Low-Energy Solar-Light-Induced Electron Transfer Towards H 2 Evolution %U https://doi.org/10.1002%2Fanie.202001231 %V 59 %X A photocatalytic system containing a perylene bisimide (PBI) dye as a photosensitizer anchored to titanium dioxide (TiO2) nanoparticles through carboxyl groups was constructed. Under solar‐light irradiation in the presence of sacrificial triethanolamine (TEOA) in neutral and basic conditions (pH 8.5), a reaction cascade is initiated in which the PBI molecule first absorbs green light, giving the formation of a stable radical anion (PBI.−), which in a second step absorbs near‐infrared light, forming a stable PBI dianion (PBI2−). Finally, the dianion absorbs red light and injects an electron into the TiO2 nanoparticle that is coated with platinum co‐catalyst for hydrogen evolution. The hydrogen evolution rates (HERs) are as high as 1216 and 1022 μmol h−1 g−1 with simulated sunlight irradiation in neutral and basic conditions, respectively.
• Efficient Multiexciton State Generation in Charge-Transfer-Coupled Perylene Bisimide Dimers via Structural Control. Hong, Yongseok; Kim, Juno; Kim, Woojae; Kaufmann, Christina; Kim, Hyungjun; Würthner, Frank; Kim, Dongho. In J. Am. Chem. Soc., 142(17), pp. 7845–7857. 2020.
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  The singlet fission (SF) process is generally defined as the conversion of one singlet exciton (S1) into two triplet excitons (2·T1), which has the potential to overcome thermalization losses in the field of photovoltaic devices. Among the applicable compounds for SF-based photovoltaic devices, perylene bisimide (PBI) is one of the best candidates because of its electronic tunability and photostability. However, the strategy for efficient SF in PBIs remains ambiguous because of numerous competing relaxation pathways in PBI-based molecular materials. In this regard, for the first time, we observed the SF mechanism in PBI dimers by controlling the intrinsic factor (exciton coupling) and the external environment (solvent polarity and viscosity). Time-resolved spectroscopic measurements and quantum chemical simulations reveal that efficient SF occurs through the charge-transfer-assisted mechanism, entailing a large structural fluctuation. Our findings not only highlight the SF mechanism in PBI dimers but also suggest the factors responsible for an efficient SF process, which are important considerations in the design of molecular materials for photovoltaic devices.

  @article{Hong_2020, abstract = {The singlet fission (SF) process is generally defined as the conversion of one singlet exciton (S1) into two triplet excitons (2·T1), which has the potential to overcome thermalization losses in the field of photovoltaic devices. Among the applicable compounds for SF-based photovoltaic devices, perylene bisimide (PBI) is one of the best candidates because of its electronic tunability and photostability. However, the strategy for efficient SF in PBIs remains ambiguous because of numerous competing relaxation pathways in PBI-based molecular materials. In this regard, for the first time, we observed the SF mechanism in PBI dimers by controlling the intrinsic factor (exciton coupling) and the external environment (solvent polarity and viscosity). Time-resolved spectroscopic measurements and quantum chemical simulations reveal that efficient SF occurs through the charge-transfer-assisted mechanism, entailing a large structural fluctuation. Our findings not only highlight the SF mechanism in PBI dimers but also suggest the factors responsible for an efficient SF process, which are important considerations in the design of molecular materials for photovoltaic devices.}, author = {Hong, Yongseok and Kim, Juno and Kim, Woojae and Kaufmann, Christina and Kim, Hyungjun and Würthner, Frank and Kim, Dongho}, journal = {J. Am. Chem. Soc.}, keywords = {myown}, month = {04}, number = 17, pages = {7845–7857}, publisher = {American Chemical Society ({ACS})}, title = {Efficient Multiexciton State Generation in Charge-Transfer-Coupled Perylene Bisimide Dimers via Structural Control}, volume = 142, year = 2020 }

  %0 Journal Article %1 Hong_2020 %A Hong, Yongseok %A Kim, Juno %A Kim, Woojae %A Kaufmann, Christina %A Kim, Hyungjun %A Würthner, Frank %A Kim, Dongho %D 2020 %I American Chemical Society (ACS) %J J. Am. Chem. Soc. %N 17 %P 7845--7857 %R 10.1021/jacs.0c00870 %T Efficient Multiexciton State Generation in Charge-Transfer-Coupled Perylene Bisimide Dimers via Structural Control %U https://doi.org/10.1021%2Fjacs.0c00870 %V 142 %X The singlet fission (SF) process is generally defined as the conversion of one singlet exciton (S1) into two triplet excitons (2·T1), which has the potential to overcome thermalization losses in the field of photovoltaic devices. Among the applicable compounds for SF-based photovoltaic devices, perylene bisimide (PBI) is one of the best candidates because of its electronic tunability and photostability. However, the strategy for efficient SF in PBIs remains ambiguous because of numerous competing relaxation pathways in PBI-based molecular materials. In this regard, for the first time, we observed the SF mechanism in PBI dimers by controlling the intrinsic factor (exciton coupling) and the external environment (solvent polarity and viscosity). Time-resolved spectroscopic measurements and quantum chemical simulations reveal that efficient SF occurs through the charge-transfer-assisted mechanism, entailing a large structural fluctuation. Our findings not only highlight the SF mechanism in PBI dimers but also suggest the factors responsible for an efficient SF process, which are important considerations in the design of molecular materials for photovoltaic devices.
• Self-assembled Möbius strips with controlled helicity. Ouyang, Guanghui; Ji, Lukang; Jiang, Yuqian; Würthner, Frank; Liu, Minghua. In Nat. Commun., 11(1). 2020.
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  Different from molecular level topology, the development of supramolecular topology has been limited due to a lack of reliable synthetic methods. Here we describe a supramolecular strategy of accessing Möbius strip, a fascinating topological object featured with only a single edge and single side. Through bending and cyclization of twisted nanofibers self-assembled from chiral glutamate amphiphiles, supramolecular nano-toroids with various twist numbers were obtained. Electron microscopic techniques could clearly identify the formation of Möbius strips when twist numbers on the toroidal fibers are odd ones. Spectroscopic and morphological analysis indicates that the helicity of the Möbius strips and nano-toroids stems from the molecular chirality of glutamate molecules. Therefore, M- and P-helical Möbius strips could be formed from L- and D-amphiphiles, respectively. Our experimental results and theoretical simulations may advance the prospect of creating chiral topologically complex structures via supramolecular approach.

  @article{Ouyang_2020, abstract = {Different from molecular level topology, the development of supramolecular topology has been limited due to a lack of reliable synthetic methods. Here we describe a supramolecular strategy of accessing Möbius strip, a fascinating topological object featured with only a single edge and single side. Through bending and cyclization of twisted nanofibers self-assembled from chiral glutamate amphiphiles, supramolecular nano-toroids with various twist numbers were obtained. Electron microscopic techniques could clearly identify the formation of Möbius strips when twist numbers on the toroidal fibers are odd ones. Spectroscopic and morphological analysis indicates that the helicity of the Möbius strips and nano-toroids stems from the molecular chirality of glutamate molecules. Therefore, M- and P-helical Möbius strips could be formed from L- and D-amphiphiles, respectively. Our experimental results and theoretical simulations may advance the prospect of creating chiral topologically complex structures via supramolecular approach.}, author = {Ouyang, Guanghui and Ji, Lukang and Jiang, Yuqian and Würthner, Frank and Liu, Minghua}, journal = {Nat. Commun.}, keywords = {myown}, month = 11, number = 1, publisher = {Springer Science and Business Media {LLC}}, title = {Self-assembled Möbius strips with controlled helicity}, volume = 11, year = 2020 }

  %0 Journal Article %1 Ouyang_2020 %A Ouyang, Guanghui %A Ji, Lukang %A Jiang, Yuqian %A Würthner, Frank %A Liu, Minghua %D 2020 %I Springer Science and Business Media LLC %J Nat. Commun. %N 1 %R 10.1038/s41467-020-19683-z %T Self-assembled Möbius strips with controlled helicity %U https://doi.org/10.1038%2Fs41467-020-19683-z %V 11 %X Different from molecular level topology, the development of supramolecular topology has been limited due to a lack of reliable synthetic methods. Here we describe a supramolecular strategy of accessing Möbius strip, a fascinating topological object featured with only a single edge and single side. Through bending and cyclization of twisted nanofibers self-assembled from chiral glutamate amphiphiles, supramolecular nano-toroids with various twist numbers were obtained. Electron microscopic techniques could clearly identify the formation of Möbius strips when twist numbers on the toroidal fibers are odd ones. Spectroscopic and morphological analysis indicates that the helicity of the Möbius strips and nano-toroids stems from the molecular chirality of glutamate molecules. Therefore, M- and P-helical Möbius strips could be formed from L- and D-amphiphiles, respectively. Our experimental results and theoretical simulations may advance the prospect of creating chiral topologically complex structures via supramolecular approach.
• Self-Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra-Bay-Acyloxy Perylene Bisimide. Hecht, Markus; Leowanawat, Pawaret; Gerlach, Tabea; Stepanenko, Vladimir; Stolte, Matthias; Lehmann, Matthias; Würthner, Frank. In Angew. Chem. Int. Ed. 2020.
  • [ Abstract ]
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  A new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self‐assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen‐bond‐directed self‐assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid‐crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo‐ or heterochiral self‐assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self‐sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self‐assemblies proceeds by dissociation via the monomeric state.

  @article{Hecht_2020, abstract = {A new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self‐assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen‐bond‐directed self‐assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid‐crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo‐ or heterochiral self‐assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self‐sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self‐assemblies proceeds by dissociation via the monomeric state.}, author = {Hecht, Markus and Leowanawat, Pawaret and Gerlach, Tabea and Stepanenko, Vladimir and Stolte, Matthias and Lehmann, Matthias and Würthner, Frank}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {08}, publisher = {Wiley}, title = {Self-Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra-Bay-Acyloxy Perylene Bisimide}, year = 2020 }

  %0 Journal Article %1 Hecht_2020 %A Hecht, Markus %A Leowanawat, Pawaret %A Gerlach, Tabea %A Stepanenko, Vladimir %A Stolte, Matthias %A Lehmann, Matthias %A Würthner, Frank %D 2020 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202006744 %T Self-Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra-Bay-Acyloxy Perylene Bisimide %U https://doi.org/10.1002%2Fanie.202006744 %X A new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self‐assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen‐bond‐directed self‐assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid‐crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo‐ or heterochiral self‐assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self‐sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self‐assemblies proceeds by dissociation via the monomeric state.
• Increased Electron Transport and Hole Blocking in an Aqueous Solution Processed Dye-Doped ZnO Cathode Interlayer for High Performance Organic Solar Cells. Luo, Yinqi; Fang, Shaomao; Zheng, Nan; Liu, Linlin; Würthner, Frank; Xie, Zengqi. In ACS Appl. Energy Mater., 3(2), pp. 1694–1701. 2020.
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  In this work, we report high electron transport and hole blocking capability of hybrid photoconductive interlayer materials manufactured from an aqueous solution, which are achieved by doping perylene bisimide dyes into zinc oxide (ZnO) through the formation of ionic bonding between the organic dopants and the inorganic matrix. Benzenesulfonic acid functional groups are introduced to perylene bisimide dye molecules, which enhance the solubility of the dye molecules in water and form ionic bonds with zinc atoms during the fabrication of the hybrid thin films. The ionic bonding assisted molecular dispersion endows the hybrid thin film with full photoconductive properties, which improves electron transport by photoinduced electron transfer from organic dye molecules to the conduction band of ZnO. Especially, the hole blocking ability is also highly increased. Both increased electron transport and hole blocking are benefits to the charge selectivity of the cathode interlayer, which results in a high fill factor in organic solar cells. A power conversion efficiency of up to 15.4% is achieved on the basis of such an aqueous solution processed hybrid interlayer when using PM6:Y6 as the active layer. In addition, the optimized thermal annealing temperature for the fabrication of the hybrid thin film is as low as 150 °C, which is a benefit for the application of such photoconductive materials in flexible devices.

  @article{Luo_2020, abstract = {In this work, we report high electron transport and hole blocking capability of hybrid photoconductive interlayer materials manufactured from an aqueous solution, which are achieved by doping perylene bisimide dyes into zinc oxide (ZnO) through the formation of ionic bonding between the organic dopants and the inorganic matrix. Benzenesulfonic acid functional groups are introduced to perylene bisimide dye molecules, which enhance the solubility of the dye molecules in water and form ionic bonds with zinc atoms during the fabrication of the hybrid thin films. The ionic bonding assisted molecular dispersion endows the hybrid thin film with full photoconductive properties, which improves electron transport by photoinduced electron transfer from organic dye molecules to the conduction band of ZnO. Especially, the hole blocking ability is also highly increased. Both increased electron transport and hole blocking are benefits to the charge selectivity of the cathode interlayer, which results in a high fill factor in organic solar cells. A power conversion efficiency of up to 15.4% is achieved on the basis of such an aqueous solution processed hybrid interlayer when using PM6:Y6 as the active layer. In addition, the optimized thermal annealing temperature for the fabrication of the hybrid thin film is as low as 150 °C, which is a benefit for the application of such photoconductive materials in flexible devices.}, author = {Luo, Yinqi and Fang, Shaomao and Zheng, Nan and Liu, Linlin and Würthner, Frank and Xie, Zengqi}, journal = {ACS Appl. Energy Mater.}, keywords = {myown}, month = {01}, number = 2, pages = {1694–1701}, publisher = {American Chemical Society (ACS)}, title = {Increased Electron Transport and Hole Blocking in an Aqueous Solution Processed Dye-Doped ZnO Cathode Interlayer for High Performance Organic Solar Cells}, volume = 3, year = 2020 }

  %0 Journal Article %1 Luo_2020 %A Luo, Yinqi %A Fang, Shaomao %A Zheng, Nan %A Liu, Linlin %A Würthner, Frank %A Xie, Zengqi %D 2020 %I American Chemical Society (ACS) %J ACS Appl. Energy Mater. %N 2 %P 1694--1701 %R 10.1021/acsaem.9b02176 %T Increased Electron Transport and Hole Blocking in an Aqueous Solution Processed Dye-Doped ZnO Cathode Interlayer for High Performance Organic Solar Cells %U https://doi.org/10.1021%2Facsaem.9b02176 %V 3 %X In this work, we report high electron transport and hole blocking capability of hybrid photoconductive interlayer materials manufactured from an aqueous solution, which are achieved by doping perylene bisimide dyes into zinc oxide (ZnO) through the formation of ionic bonding between the organic dopants and the inorganic matrix. Benzenesulfonic acid functional groups are introduced to perylene bisimide dye molecules, which enhance the solubility of the dye molecules in water and form ionic bonds with zinc atoms during the fabrication of the hybrid thin films. The ionic bonding assisted molecular dispersion endows the hybrid thin film with full photoconductive properties, which improves electron transport by photoinduced electron transfer from organic dye molecules to the conduction band of ZnO. Especially, the hole blocking ability is also highly increased. Both increased electron transport and hole blocking are benefits to the charge selectivity of the cathode interlayer, which results in a high fill factor in organic solar cells. A power conversion efficiency of up to 15.4% is achieved on the basis of such an aqueous solution processed hybrid interlayer when using PM6:Y6 as the active layer. In addition, the optimized thermal annealing temperature for the fabrication of the hybrid thin film is as low as 150 °C, which is a benefit for the application of such photoconductive materials in flexible devices.
• Supramolecular polymerization through kinetic pathway control and living chain growth. Wehner, Marius; Würthner, Frank. In Nature Reviews Chemistry, 4, pp. 38–53. 2020.
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  Supramolecular polymers exhibit fascinating structures, and their properties, and thus applications, depend both on the strength and dynamics of the non-covalent bonds and on the functional properties of the monomeric building blocks. In this Review, we highlight the progress in methods developed to control supramolecular polymerization based on physicochemical insights into the thermodynamics and kinetics of non-covalent interactions. Prerequisites for polymer formation and stability, such as high binding strength (thermodynamics) between complementary receptor units, are briefly discussed, while the main focus is on the kinetic control of pathway selectivity, which in recent years has allowed seed-induced living supramolecular polymerization, chain growth-type supramolecular polymerization and the preparation of specific supramolecular polymer polymorphs and supramolecular block copolymers.

  @article{noauthororeditor, abstract = {Supramolecular polymers exhibit fascinating structures, and their properties, and thus applications, depend both on the strength and dynamics of the non-covalent bonds and on the functional properties of the monomeric building blocks. In this Review, we highlight the progress in methods developed to control supramolecular polymerization based on physicochemical insights into the thermodynamics and kinetics of non-covalent interactions. Prerequisites for polymer formation and stability, such as high binding strength (thermodynamics) between complementary receptor units, are briefly discussed, while the main focus is on the kinetic control of pathway selectivity, which in recent years has allowed seed-induced living supramolecular polymerization, chain growth-type supramolecular polymerization and the preparation of specific supramolecular polymer polymorphs and supramolecular block copolymers.}, author = {Wehner, Marius and Würthner, Frank}, journal = {Nature Reviews Chemistry}, keywords = {myown}, month = {01}, pages = {38-53}, title = {Supramolecular polymerization through kinetic pathway control and living chain growth}, volume = 4, year = 2020 }

  %0 Journal Article %1 noauthororeditor %A Wehner, Marius %A Würthner, Frank %D 2020 %J Nature Reviews Chemistry %P 38-53 %R 10.1038/s41570-019-0153-8 %T Supramolecular polymerization through kinetic pathway control and living chain growth %U https://www.nature.com/articles/s41570-019-0153-8 %V 4 %X Supramolecular polymers exhibit fascinating structures, and their properties, and thus applications, depend both on the strength and dynamics of the non-covalent bonds and on the functional properties of the monomeric building blocks. In this Review, we highlight the progress in methods developed to control supramolecular polymerization based on physicochemical insights into the thermodynamics and kinetics of non-covalent interactions. Prerequisites for polymer formation and stability, such as high binding strength (thermodynamics) between complementary receptor units, are briefly discussed, while the main focus is on the kinetic control of pathway selectivity, which in recent years has allowed seed-induced living supramolecular polymerization, chain growth-type supramolecular polymerization and the preparation of specific supramolecular polymer polymorphs and supramolecular block copolymers.
• Exciton Migration in Multistranded Perylene Bisimide J-Aggregates. Rehhagen, Chris; Stolte, Matthias; Herbst, Stefanie; Hecht, Markus; Lochbrunner, Stefan; Würthner, Frank; Fennel, Franziska. In J. Phys. Chem. Lett., 11(16), pp. 6612–6617. 2020.
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  Exciton migration in self-assembled supramolecular ensembles of dye molecules is controlled by the electronic coupling between adjacent sites, the delocalization of the excitation and thereby by the packing arrangement. Here, we put emphasis on the packing structure and analyze the exciton migration in two perylene bisimide-based J-aggregates composed of almost identical molecular building blocks but forming double-strand versus quadruple-strand slip-stacked supramolecular architectures. Analyzing ultrafast transient absorption spectra in dependence on the exciton density by a kinetic model for exciton–exciton annihilation based on incoherent transfer demonstrates that the migration is quasi one-dimensional. The migration distance is enhanced by a beneficial geometrical structure. We find a factor of more than two between the diffusion lengths of 188 and 77 nm for the double- and quadruple-stranded system. The supramolecular design efficiently influences the exciton mobility and minor structural changes have a pronounced influence on functional properties of dye aggregates.

  @article{Rehhagen_2020, abstract = {Exciton migration in self-assembled supramolecular ensembles of dye molecules is controlled by the electronic coupling between adjacent sites, the delocalization of the excitation and thereby by the packing arrangement. Here, we put emphasis on the packing structure and analyze the exciton migration in two perylene bisimide-based J-aggregates composed of almost identical molecular building blocks but forming double-strand versus quadruple-strand slip-stacked supramolecular architectures. Analyzing ultrafast transient absorption spectra in dependence on the exciton density by a kinetic model for exciton–exciton annihilation based on incoherent transfer demonstrates that the migration is quasi one-dimensional. The migration distance is enhanced by a beneficial geometrical structure. We find a factor of more than two between the diffusion lengths of 188 and 77 nm for the double- and quadruple-stranded system. The supramolecular design efficiently influences the exciton mobility and minor structural changes have a pronounced influence on functional properties of dye aggregates.}, author = {Rehhagen, Chris and Stolte, Matthias and Herbst, Stefanie and Hecht, Markus and Lochbrunner, Stefan and Würthner, Frank and Fennel, Franziska}, journal = {J. Phys. Chem. Lett.}, keywords = {myown}, month = {07}, number = 16, pages = {6612–6617}, publisher = {American Chemical Society ({ACS})}, title = {Exciton Migration in Multistranded Perylene Bisimide J-Aggregates}, volume = 11, year = 2020 }

  %0 Journal Article %1 Rehhagen_2020 %A Rehhagen, Chris %A Stolte, Matthias %A Herbst, Stefanie %A Hecht, Markus %A Lochbrunner, Stefan %A Würthner, Frank %A Fennel, Franziska %D 2020 %I American Chemical Society (ACS) %J J. Phys. Chem. Lett. %N 16 %P 6612--6617 %R 10.1021/acs.jpclett.0c01669 %T Exciton Migration in Multistranded Perylene Bisimide J-Aggregates %U https://doi.org/10.1021%2Facs.jpclett.0c01669 %V 11 %X Exciton migration in self-assembled supramolecular ensembles of dye molecules is controlled by the electronic coupling between adjacent sites, the delocalization of the excitation and thereby by the packing arrangement. Here, we put emphasis on the packing structure and analyze the exciton migration in two perylene bisimide-based J-aggregates composed of almost identical molecular building blocks but forming double-strand versus quadruple-strand slip-stacked supramolecular architectures. Analyzing ultrafast transient absorption spectra in dependence on the exciton density by a kinetic model for exciton–exciton annihilation based on incoherent transfer demonstrates that the migration is quasi one-dimensional. The migration distance is enhanced by a beneficial geometrical structure. We find a factor of more than two between the diffusion lengths of 188 and 77 nm for the double- and quadruple-stranded system. The supramolecular design efficiently influences the exciton mobility and minor structural changes have a pronounced influence on functional properties of dye aggregates.
• Persistent Room Temperature Phosphorescence from Triarylboranes: A Combined Experimental and Theoretical Study. Wu, Zhu; Nitsch, Jörn; Schuster, Julia; Friedrich, Alexandra; Edkins, Katharina; Loebnitz, Marcel; Dinkelbach, Fabian; Stepanenko, Vladimir; Würthner, Frank; Marian, Christel M.; Ji, Lei; Marder, Todd B. In Angew. Chem. Int. Ed. 2020.
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  Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate kisc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions.

  @article{Wu_2020, abstract = {Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate kisc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions.}, author = {Wu, Zhu and Nitsch, Jörn and Schuster, Julia and Friedrich, Alexandra and Edkins, Katharina and Loebnitz, Marcel and Dinkelbach, Fabian and Stepanenko, Vladimir and Würthner, Frank and Marian, Christel M. and Ji, Lei and Marder, Todd B.}, journal = {Angew. Chem. Int. Ed.}, keywords = {myown}, month = {08}, publisher = {Wiley}, title = {Persistent Room Temperature Phosphorescence from Triarylboranes: A Combined Experimental and Theoretical Study}, year = 2020 }

  %0 Journal Article %1 Wu_2020 %A Wu, Zhu %A Nitsch, Jörn %A Schuster, Julia %A Friedrich, Alexandra %A Edkins, Katharina %A Loebnitz, Marcel %A Dinkelbach, Fabian %A Stepanenko, Vladimir %A Würthner, Frank %A Marian, Christel M. %A Ji, Lei %A Marder, Todd B. %D 2020 %I Wiley %J Angew. Chem. Int. Ed. %R 10.1002/anie.202007610 %T Persistent Room Temperature Phosphorescence from Triarylboranes: A Combined Experimental and Theoretical Study %U https://doi.org/10.1002%2Fanie.202007610 %X Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate kisc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions.
• Anion-Coordination-Assisted Assembly of Supramolecular Charge-Transfer Complexes Based on Tris(urea) Ligands. Zhang, Dan; Hou, Le-Kai; Zhang, Qiang; He, Jia-Wei; Feng, Hong-Jian; Würthner, Frank; Yang, Xiao-Juan; Wu, Biao. In Chem. Eur. J., 26(6), pp. 1414–1421. 2020.
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  Charge‐transfer (CT) complexes, formed by noncovalent bonding between electron‐rich (donor, D) and electron‐deficient (acceptor, A) molecules (or moieties) have attracted considerable attention due to their fascinating structures and potential applications. Herein, we demonstrate that anion coordination is a promising strategy to promote CT complex formation between anion‐binding, electron‐rich tris(urea) donor ligands (D) and electron‐deficient viologen cation acceptors (A), which form co‐crystals featuring infinite ⋅⋅⋅DADA⋅⋅⋅ or discrete (circular DADA or three‐decker DAD) π‐stacking interactions. These CT complexes were studied by X‐ray diffraction, UV/Vis spectroscopy, electric conductivity measurements, charge displacement curve (CDC) calculations, and DFT computations.

  @article{Zhang_2020, abstract = {Charge‐transfer (CT) complexes, formed by noncovalent bonding between electron‐rich (donor, D) and electron‐deficient (acceptor, A) molecules (or moieties) have attracted considerable attention due to their fascinating structures and potential applications. Herein, we demonstrate that anion coordination is a promising strategy to promote CT complex formation between anion‐binding, electron‐rich tris(urea) donor ligands (D) and electron‐deficient viologen cation acceptors (A), which form co‐crystals featuring infinite ⋅⋅⋅DADA⋅⋅⋅ or discrete (circular DADA or three‐decker DAD) π‐stacking interactions. These CT complexes were studied by X‐ray diffraction, UV/Vis spectroscopy, electric conductivity measurements, charge displacement curve (CDC) calculations, and DFT computations.}, author = {Zhang, Dan and Hou, Le-Kai and Zhang, Qiang and He, Jia-Wei and Feng, Hong-Jian and Würthner, Frank and Yang, Xiao-Juan and Wu, Biao}, journal = {Chem. Eur. J.}, keywords = {myown}, month = {01}, number = 6, pages = {1414–1421}, publisher = {Wiley}, title = {Anion-Coordination-Assisted Assembly of Supramolecular Charge-Transfer Complexes Based on Tris(urea) Ligands}, volume = 26, year = 2020 }

  %0 Journal Article %1 Zhang_2020 %A Zhang, Dan %A Hou, Le-Kai %A Zhang, Qiang %A He, Jia-Wei %A Feng, Hong-Jian %A Würthner, Frank %A Yang, Xiao-Juan %A Wu, Biao %D 2020 %I Wiley %J Chem. Eur. J. %N 6 %P 1414--1421 %R 10.1002/chem.201905021 %T Anion-Coordination-Assisted Assembly of Supramolecular Charge-Transfer Complexes Based on Tris(urea) Ligands %U https://doi.org/10.1002%2Fchem.201905021 %V 26 %X Charge‐transfer (CT) complexes, formed by noncovalent bonding between electron‐rich (donor, D) and electron‐deficient (acceptor, A) molecules (or moieties) have attracted considerable attention due to their fascinating structures and potential applications. Herein, we demonstrate that anion coordination is a promising strategy to promote CT complex formation between anion‐binding, electron‐rich tris(urea) donor ligands (D) and electron‐deficient viologen cation acceptors (A), which form co‐crystals featuring infinite ⋅⋅⋅DADA⋅⋅⋅ or discrete (circular DADA or three‐decker DAD) π‐stacking interactions. These CT complexes were studied by X‐ray diffraction, UV/Vis spectroscopy, electric conductivity measurements, charge displacement curve (CDC) calculations, and DFT computations.
• Base-Assisted Imidization: A Synthetic Method for the Introduction of Bulky Imide Substituents to Control Packing and Optical Properties of Naphthalene and Perylene Imides. Mahl, Magnus; Shoyama, Kazutaka; Krause, Ana-Maria; Schmidt, David; Würthner, Frank. In Angew. Chem. Int. Ed., 59(32), pp. 13401–13405. 2020.
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  We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho ,ortho‐diaryl‐ and ortho ,ortho‐dialkynylaniline derivatives. This imidization method uses n‐butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single‐crystal X‐ray diffraction analyses reveal dimeric packing motifs for monoimides, while two‐side shielded bisimides crystallize in isolated molecules without close π–π‐interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state.

  @article{Mahl_2020, abstract = {We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho ,ortho‐diaryl‐ and ortho ,ortho‐dialkynylaniline derivatives. This imidization method uses n‐butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single‐crystal X‐ray diffraction analyses reveal dimeric packing motifs for monoimides, while two‐side shielded bisimides crystallize in isolated molecules without close π–π‐interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state.}, author = {Mahl, Magnus and Shoyama, Kazutaka and Krause, Ana-Maria and Schmidt, David and Würthner, Frank}, journal = {Angew. Chem. Int.