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Frank Wurthner - One of the best experts on this subject based on the ideXlab platform.
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stepwise folding and self assembly of a Merocyanine folda pentamer
Journal of the American Chemical Society, 2020Co-Authors: Joachim O Lindner, Frank WurthnerAbstract:Here we report a synthetic protocol toward a Merocyanine (MC) pentamer 1 which represents the first Merocyanine oligomer longer than a dimer. By continuously decreasing the solvent polarity, we demonstrate the stepwise folding from partially folded monomeric and dimeric MC subunits (in chloroform) up to the full pentamer π-stack (in 75% methylcyclohexane/25% chloroform) and a subsequent self-assembly of pentamer 1 into larger aggregates (in 80% methylcyclohexane/20% chloroform). This hierarchical structure formation process became possible due to the predominant dipole-dipole interactions among MC dyes that allowed for a precise modulation of the energy landscape by the solvent polarity. This unprecedented stepwise control of dye assembly via hierarchical dipole-dipole interactions opens the door for a more precise control of dye-dye interactions in artificial multichromophoric ensembles.
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defined Merocyanine dye stacks from a dimer up to an octamer by spacer encoded self assembly approach
Journal of the American Chemical Society, 2019Co-Authors: Eva Kirchner, Matthias Grune, David Bialas, Franziska Fennel, Frank WurthnerAbstract:A series of well-defined chromophore stacks is obtained upon self-assembly of Merocyanine and bis(Merocyanine) dyes in nonpolar solvents. Careful design of the spacer moieties linking the dipolar chromophores within the bis(Merocyanine) dyes allows one to direct the dipole-dipole interaction driven aggregation into stacks of desired size from dimer up to octamer. The spacer-encoded self-assembly process was investigated by UV/vis absorption spectroscopy showing an increase of the hypsochromic shift with increasing stack size. The structure of the largest aggregate comprising eight chromophores was analyzed by 1D and 2D nuclear magnetic resonance spectroscopic studies revealing a perfectly interdigitated centrosymmetric organization of the dipolar dyes and concomitant annihilation of the ground state dipole moment is observed in the UV/vis absorption spectra. This unprecedented series of dye stacks from dimer to octamer enabled a systematic study of the optical absorption properties in dependence of the stack size disclosing that the absorption features can be rationalized by molecular exciton theory. Our results show that the noncovalent synthesis approach based on dipolar aggregation is suitable for the design of well-defined dye aggregates of specific size, allowing in-depth studies to manifest structure-property relationships.
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exciton coupling of Merocyanine dyes from h to j type in the solid state by crystal engineering
Nano Letters, 2017Co-Authors: Andreas Liess, Matthias Stolte, Vladimir Stepanenko, Anamaria Krause, David Bialas, Alhama Arjonaesteban, Frank WurthnerAbstract:A key issue for the application of π-conjugated organic molecules as thin film solid-state materials is the packing structure, which drastically affects optical and electronic properties due to intermolecular coupling. In this regard, Merocyanine dyes usually pack in H-coupled antiparallel arrangements while structures with more interesting J-type coupling have been rarely reported. Here we show that for three highly dipolar Merocyanine dyes, which exhibit the same π-scaffold and accordingly equal properties as monomers in solution, the solid-state packing can be changed by a simple variation of aliphatic substituents to afford narrow and intense absorption bands with huge hypsochromic (H) or bathochromic (J) shifts for their thin films and nanocrystals. Time-dependent density functional theory calculations show that the energetic offset of almost 1 eV magnitude results from distinct packing motifs within the crystal structures that comply with the archetype H- or J-aggregate structures as described by Ka...
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dipole dipole interaction driven self assembly of Merocyanine dyes from dimers to nanoscale objects and supramolecular materials
Accounts of Chemical Research, 2016Co-Authors: Frank WurthnerAbstract:π-Conjugation between heterocyclic donor (D) and acceptor (A) groups via a polymethine chain leads to dyes with dipole moments greater than 10 D. These dipole moments direct the self-assembly of the dyes into antiparallel dimer aggregates, even in dilute solution, with binding strengths that are far beyond those observed for other π-scaffolds whose self-assembly is driven primarily by dispersion forces. The combination of directionality and exceptional binding strength of dipolar interactions between D-π-A dyes indeed resembles the situation of the hydrogen bond. Thus, similar to the latter, dipolar interactions between Merocyanine dyes, a unique class of D-π-A chromophores, can be utilized to construct sophisticated supramolecular architectures of predictable geometry, particularly in low polarity environments. For bis(Merocyanine) dyes it has been demonstrated that the self-assembly pathway is encoded in the tether between the two constituent Merocyanine chromophores. If the tether enables the antiparallel stacking of the two appended dyes, folding takes place, which may be followed by further self-assembly into extended H-aggregate π-stacks at higher concentrations in solvents of low polarity. For tethers that do not support folding, the formation of bimolecular complexes of four Merocyanine units, cyclic oligomers, and supramolecular polymers has been observed. For the former case, that is, formation of a bimolecular stack of four Merocyanine units from tweezer-type molecules, association constants >10(9) M(-1) were measured in chloroform. On the other hand, because only one π-face is utilized in the formation of supramolecular polymers from bis(Merocyanine) dyes, higher hierarchical structures typically originate in which the other π-face is surrounded by an antiparallel π-stacked neighbor molecule. Among the observed self-assembled structures, nanorods in particular have attracted considerable attention because their self-assembly into well-defined H-aggregates falls under kinetic control and is slowed tremendously with decreasing solvent polarity. Co-assembly of achiral and chiral Merocyanine building blocks or two enantiomers of a chiral Merocyanine in different ratios provided insight into "majority rules" and "sergeant-and-soldiers" effects as well as the autocatalytic fiber growth process. With regard to materials applications, it is important to note that the high propensity for dipolar aggregation was disadvantageous for many envisioned applications of these dyes in the area of nonlinear optics. However, this aggregation behavior proved to be advantageous for the recently demonstrated applications of D-π-A dyes, in particular, Merocyanines as p-type organic semiconductors in organic electronics and photovoltaics. Thus, organic transistors with hole mobilities >0.5 cm(2)/(V s) and organic solar cells with power conversion efficiencies >6% could be achieved with Merocyanine-based organic semiconductor molecules.
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combination of cyanine behaviour and giant hyperpolarisability in novel Merocyanine dyes beyond the bond length alternation bla paradigm
Chemistry: A European Journal, 2015Co-Authors: V A Parthasarathy, Matthias Stolte, Frank Wurthner, Frederic Castet, Ravindra Pandey, Sampa Ghosh, Puspendu K Das, Mireille BlancharddesceAbstract:Merocyanine dyes that exhibit antithetic cyanine-like behaviour and giant first-order hyperpolarisability (β) values have been designed. These cyanine-type dyes open up an intriguing route towards molecular-based electro-optic materials as well as new second-harmonic generation dyes for imaging.
Matthias Stolte - One of the best experts on this subject based on the ideXlab platform.
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exciton coupling of Merocyanine dyes from h to j type in the solid state by crystal engineering
Nano Letters, 2017Co-Authors: Andreas Liess, Matthias Stolte, Vladimir Stepanenko, Anamaria Krause, David Bialas, Alhama Arjonaesteban, Frank WurthnerAbstract:A key issue for the application of π-conjugated organic molecules as thin film solid-state materials is the packing structure, which drastically affects optical and electronic properties due to intermolecular coupling. In this regard, Merocyanine dyes usually pack in H-coupled antiparallel arrangements while structures with more interesting J-type coupling have been rarely reported. Here we show that for three highly dipolar Merocyanine dyes, which exhibit the same π-scaffold and accordingly equal properties as monomers in solution, the solid-state packing can be changed by a simple variation of aliphatic substituents to afford narrow and intense absorption bands with huge hypsochromic (H) or bathochromic (J) shifts for their thin films and nanocrystals. Time-dependent density functional theory calculations show that the energetic offset of almost 1 eV magnitude results from distinct packing motifs within the crystal structures that comply with the archetype H- or J-aggregate structures as described by Ka...
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combination of cyanine behaviour and giant hyperpolarisability in novel Merocyanine dyes beyond the bond length alternation bla paradigm
Chemistry: A European Journal, 2015Co-Authors: V A Parthasarathy, Matthias Stolte, Frank Wurthner, Frederic Castet, Ravindra Pandey, Sampa Ghosh, Puspendu K Das, Mireille BlancharddesceAbstract:Merocyanine dyes that exhibit antithetic cyanine-like behaviour and giant first-order hyperpolarisability (β) values have been designed. These cyanine-type dyes open up an intriguing route towards molecular-based electro-optic materials as well as new second-harmonic generation dyes for imaging.
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structure property relationships for exciton and charge reorganization energies of dipolar organic semiconductors a combined valence bond self consistent field and time dependent hartree fock and dft study of Merocyanine dyes
Journal of Physical Chemistry C, 2015Co-Authors: Charlotte Bruckner, Matthias Stolte, Frank Wurthner, Klaus Meerholz, Christof Walter, Benoit Braida, Bernd EngelsAbstract:We present an analysis of the optoelectronic properties of Merocyanine dyes by means of valence bond self-consistent field (VBSCF), time-dependent Hartree-Fock (TD-HF), density functional theory (DFT), and high-level ab initio calculations. The electronic structure of Merocyanines can be described as a superposition of two resonance structures, a neutral one and a zwitterionic one. Calculated valence bond (VB) weights for these resonance structures demonstrate the importance of strong accepting groups when increasing the weight of the zwitterionic structures of different Merocyanines. The dependence of exciton and charge reorganization energies on VB weights’ composition is analyzed, demonstrating that the special case of equal contributions of both structures, the so-called cyanine limit, goes along with minimal exciton and charge reorganization energies. For the latter, it is shown that the external (outer-sphere) reorganization energy plays a crucial role. Furthermore, a careful investigation of the ex...
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nir absorbing Merocyanine dyes for bhj solar cells
Chemistry of Materials, 2014Co-Authors: Andre Zitzlerkunkel, Matthias Stolte, Martin R Lenze, Nils M Kronenberg, Anamaria Krause, Klaus Meerholz, Frank WurthnerAbstract:We have synthesized a series of new, polymethine chain extended Merocyanine dyes 1–4 bearing varied acceptor units and an aminothiophene donor moiety. The optical and electronic properties of these new Merocyanines have been studied in comparison with their corresponding lower homologues 5–8, which contain two methine groups less, by UV–vis and electro-optical absorption (EOA) spectroscopy and cyclic voltammetry. The absorption spectra of π-extended Merocyanines are markedly red-shifted, and their extinction coefficients are significantly increased compared to those of their lower homologues. The photovoltaic characteristics of these dyes have been explored in devices using them as donor and PC61BM fullerene as acceptor materials. Our detailed studies reveal that, despite more favorable absorption properties, the π-extended Merocyanines exhibit lower short-circuit current densities (JSC) as well as decreased open-circuit voltages (VOC) and power conversion efficiencies (PCE) compared with those of their r...
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Cooperative supramolecular polymerization: comparison of different models applied on the self-assembly of bis(Merocyanine) dyes.
Chemistry: A European Journal, 2012Co-Authors: Gustavo Fernández, Matthias Stolte, Vladimir Stepanenko, Frank WurthnerAbstract:Three new molecular building blocks 1 a–c for supramolecular polymerization are described that feature two dipolar Merocyanine dyes tethered by p-xylylene spacers. Concentration- and temperature-dependent UV/Vis spectroscopy in chloroform combined with dynamic light scattering, capillary viscosimetry and atomic force microscopy investigations were applied to elucidate the mechanistic features of the self-assembly of these strongly dipolar dyes. Our detailed studies reveal that the self-assembly is very pronounced for bis(Merocyanines) 1 a,b bearing linear alkyl chains, but completely absent for bis(Merocyanine) 1 c bearing sterically more bulky ethylhexyl substituents. Both temperature- and concentration-dependent UV/Vis data provide unambiguous evidence for a cooperative self-assembly process for bis(Merocyanines) 1 a,b, which was analyzed in detail by the Meijer–Schenning–Van-der-Schoot model (applicable to temperature-dependent data) and by the Goldstein–Stryer model (applicable to concentration-dependent data). By combining both methods all parameters of interest to understand the self-assembly process could be derived, including in particular the nucleus size (8–10 monomeric units), the cooperativity factor (ca. 0.006), and the nucleation and elongation constants of about 103 and 106 M−1 in chloroform at room temperature, respectively.
Klaus Meerholz - One of the best experts on this subject based on the ideXlab platform.
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structure property relationships for exciton and charge reorganization energies of dipolar organic semiconductors a combined valence bond self consistent field and time dependent hartree fock and dft study of Merocyanine dyes
Journal of Physical Chemistry C, 2015Co-Authors: Charlotte Bruckner, Matthias Stolte, Frank Wurthner, Klaus Meerholz, Christof Walter, Benoit Braida, Bernd EngelsAbstract:We present an analysis of the optoelectronic properties of Merocyanine dyes by means of valence bond self-consistent field (VBSCF), time-dependent Hartree-Fock (TD-HF), density functional theory (DFT), and high-level ab initio calculations. The electronic structure of Merocyanines can be described as a superposition of two resonance structures, a neutral one and a zwitterionic one. Calculated valence bond (VB) weights for these resonance structures demonstrate the importance of strong accepting groups when increasing the weight of the zwitterionic structures of different Merocyanines. The dependence of exciton and charge reorganization energies on VB weights’ composition is analyzed, demonstrating that the special case of equal contributions of both structures, the so-called cyanine limit, goes along with minimal exciton and charge reorganization energies. For the latter, it is shown that the external (outer-sphere) reorganization energy plays a crucial role. Furthermore, a careful investigation of the ex...
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nir absorbing Merocyanine dyes for bhj solar cells
Chemistry of Materials, 2014Co-Authors: Andre Zitzlerkunkel, Matthias Stolte, Martin R Lenze, Nils M Kronenberg, Anamaria Krause, Klaus Meerholz, Frank WurthnerAbstract:We have synthesized a series of new, polymethine chain extended Merocyanine dyes 1–4 bearing varied acceptor units and an aminothiophene donor moiety. The optical and electronic properties of these new Merocyanines have been studied in comparison with their corresponding lower homologues 5–8, which contain two methine groups less, by UV–vis and electro-optical absorption (EOA) spectroscopy and cyclic voltammetry. The absorption spectra of π-extended Merocyanines are markedly red-shifted, and their extinction coefficients are significantly increased compared to those of their lower homologues. The photovoltaic characteristics of these dyes have been explored in devices using them as donor and PC61BM fullerene as acceptor materials. Our detailed studies reveal that, despite more favorable absorption properties, the π-extended Merocyanines exhibit lower short-circuit current densities (JSC) as well as decreased open-circuit voltages (VOC) and power conversion efficiencies (PCE) compared with those of their r...
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simple highly efficient vacuum processed bulk heterojunction solar cells based on Merocyanine dyes
Advanced Energy Materials, 2011Co-Authors: Vera Steinmann, Martin R Lenze, Nils M Kronenberg, Klaus Meerholz, Steven M Graf, Dirk Hertel, Hannah Burckstummer, Elena V Tulyakova, Frank WurthnerAbstract:In order to be competitive on the energy market, organic solar cells with higher efficiency are needed. To date, polymer solar cells have retained the lead with efficiencies of up to 8%. However, research on small molecule solar cells has been catching up throughout recent years and is showing similar efficiencies, however, only for more sophisticated multilayer device configurations. In this work, a simple, highly efficient, vacuum-processed small molecule solar cell based on Merocyanine dyes – traditional colorants that can easily be mass-produced and purified – is presented. In the past, Merocyanines have been successfully introduced in solution-processed as well as vacuum-processed devices, demonstrating efficiencies up to 4.9%. Here, further optimization of devices is achieved while keeping the same simple layer stack, ultimately leading to efficiencies beyond the 6% mark. In addition, physical properties such as the charge carrier transport and the cell performance under various light intensities are addressed.
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near infrared absorbing Merocyanine dyes for bulk heterojunction solar cells
Organic Letters, 2010Co-Authors: Hannah Burckstummer, Klaus Meerholz, Nils M Kronenberg, Frank WurthnerAbstract:A series of near-infrared absorbing Merocyanine dyes bearing the strong electron-accepting 2-oxo-5-dicyanomethylene-pyrrolidine unit was synthesized and applied in combination with PC61BM and PC71B...
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tailored Merocyanine dyes for solution processed bhj solar cells
Journal of Materials Chemistry, 2010Co-Authors: Hannah Burckstummer, Matthias Stolte, Nils M Kronenberg, Klaus Meerholz, Marcel Gsanger, Frank WurthnerAbstract:A solution-cast photovoltaic film of a newly designed Merocyanine chromophore blended with PCBM exhibited an appreciably high power conversion efficiency of 2.59%.
Nils M Kronenberg - One of the best experts on this subject based on the ideXlab platform.
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nir absorbing Merocyanine dyes for bhj solar cells
Chemistry of Materials, 2014Co-Authors: Andre Zitzlerkunkel, Matthias Stolte, Martin R Lenze, Nils M Kronenberg, Anamaria Krause, Klaus Meerholz, Frank WurthnerAbstract:We have synthesized a series of new, polymethine chain extended Merocyanine dyes 1–4 bearing varied acceptor units and an aminothiophene donor moiety. The optical and electronic properties of these new Merocyanines have been studied in comparison with their corresponding lower homologues 5–8, which contain two methine groups less, by UV–vis and electro-optical absorption (EOA) spectroscopy and cyclic voltammetry. The absorption spectra of π-extended Merocyanines are markedly red-shifted, and their extinction coefficients are significantly increased compared to those of their lower homologues. The photovoltaic characteristics of these dyes have been explored in devices using them as donor and PC61BM fullerene as acceptor materials. Our detailed studies reveal that, despite more favorable absorption properties, the π-extended Merocyanines exhibit lower short-circuit current densities (JSC) as well as decreased open-circuit voltages (VOC) and power conversion efficiencies (PCE) compared with those of their r...
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simple highly efficient vacuum processed bulk heterojunction solar cells based on Merocyanine dyes
Advanced Energy Materials, 2011Co-Authors: Vera Steinmann, Martin R Lenze, Nils M Kronenberg, Klaus Meerholz, Steven M Graf, Dirk Hertel, Hannah Burckstummer, Elena V Tulyakova, Frank WurthnerAbstract:In order to be competitive on the energy market, organic solar cells with higher efficiency are needed. To date, polymer solar cells have retained the lead with efficiencies of up to 8%. However, research on small molecule solar cells has been catching up throughout recent years and is showing similar efficiencies, however, only for more sophisticated multilayer device configurations. In this work, a simple, highly efficient, vacuum-processed small molecule solar cell based on Merocyanine dyes – traditional colorants that can easily be mass-produced and purified – is presented. In the past, Merocyanines have been successfully introduced in solution-processed as well as vacuum-processed devices, demonstrating efficiencies up to 4.9%. Here, further optimization of devices is achieved while keeping the same simple layer stack, ultimately leading to efficiencies beyond the 6% mark. In addition, physical properties such as the charge carrier transport and the cell performance under various light intensities are addressed.
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near infrared absorbing Merocyanine dyes for bulk heterojunction solar cells
Organic Letters, 2010Co-Authors: Hannah Burckstummer, Klaus Meerholz, Nils M Kronenberg, Frank WurthnerAbstract:A series of near-infrared absorbing Merocyanine dyes bearing the strong electron-accepting 2-oxo-5-dicyanomethylene-pyrrolidine unit was synthesized and applied in combination with PC61BM and PC71B...
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tailored Merocyanine dyes for solution processed bhj solar cells
Journal of Materials Chemistry, 2010Co-Authors: Hannah Burckstummer, Matthias Stolte, Nils M Kronenberg, Klaus Meerholz, Marcel Gsanger, Frank WurthnerAbstract:A solution-cast photovoltaic film of a newly designed Merocyanine chromophore blended with PCBM exhibited an appreciably high power conversion efficiency of 2.59%.
Hannah Burckstummer - One of the best experts on this subject based on the ideXlab platform.
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simple highly efficient vacuum processed bulk heterojunction solar cells based on Merocyanine dyes
Advanced Energy Materials, 2011Co-Authors: Vera Steinmann, Martin R Lenze, Nils M Kronenberg, Klaus Meerholz, Steven M Graf, Dirk Hertel, Hannah Burckstummer, Elena V Tulyakova, Frank WurthnerAbstract:In order to be competitive on the energy market, organic solar cells with higher efficiency are needed. To date, polymer solar cells have retained the lead with efficiencies of up to 8%. However, research on small molecule solar cells has been catching up throughout recent years and is showing similar efficiencies, however, only for more sophisticated multilayer device configurations. In this work, a simple, highly efficient, vacuum-processed small molecule solar cell based on Merocyanine dyes – traditional colorants that can easily be mass-produced and purified – is presented. In the past, Merocyanines have been successfully introduced in solution-processed as well as vacuum-processed devices, demonstrating efficiencies up to 4.9%. Here, further optimization of devices is achieved while keeping the same simple layer stack, ultimately leading to efficiencies beyond the 6% mark. In addition, physical properties such as the charge carrier transport and the cell performance under various light intensities are addressed.
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near infrared absorbing Merocyanine dyes for bulk heterojunction solar cells
Organic Letters, 2010Co-Authors: Hannah Burckstummer, Klaus Meerholz, Nils M Kronenberg, Frank WurthnerAbstract:A series of near-infrared absorbing Merocyanine dyes bearing the strong electron-accepting 2-oxo-5-dicyanomethylene-pyrrolidine unit was synthesized and applied in combination with PC61BM and PC71B...
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tailored Merocyanine dyes for solution processed bhj solar cells
Journal of Materials Chemistry, 2010Co-Authors: Hannah Burckstummer, Matthias Stolte, Nils M Kronenberg, Klaus Meerholz, Marcel Gsanger, Frank WurthnerAbstract:A solution-cast photovoltaic film of a newly designed Merocyanine chromophore blended with PCBM exhibited an appreciably high power conversion efficiency of 2.59%.
