TY  - JOUR
A1  - Kim, Jin Hong
A1  - Liess, Andreas
A1  - Stolte, Matthias
A1  - Krause, Ana-Maria
A1  - Stepanenko, Vladimir
A1  - Zhong, Chuwei
A1  - Bialas, David
A1  - Spano, Frank
A1  - Würthner, Frank
T1  - An Efficient Narrowband Near-Infrared at 1040 nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye
JF  - Advanced Materials
N2  - 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 PC\(_{61}\)BM. 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.
KW  - squaraine dyes
KW  - crystal engineering
KW  - J-aggregates
KW  - near-infrared sensitivity
KW  - organic photodiodes
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256374
VL  - 33
IS  - 26
ER  - 
TY  - JOUR
A1  - Spenst, Peter
A1  - Young, Ryan M.
A1  - Wasielewski, Michael R.
A1  - Würthner, Frank
T1  - Guest and solvent modulated photo-driven charge separation and triplet generation in a perylene bisimide cyclophane
JF  - Chemical Science
N2  - Cofacial positioning of two perylene bisimide (PBI) chromophores at a distance of 6.5 angstrom in a cyclophane structure prohibits the otherwise common excimer formation and directs photoexcited singlet state relaxation towards intramolecular symmetry-breaking charge separation (τ\(_{CS}\) = 161 +/- 4 ps) in polar CH\(_2\)Cl\(_2\), which is thermodynamically favored with a Gibbs free energy of ΔG\(_{CS}\) = -0.32 eV. The charges then recombine slowly in τ\(_{CR}\) = 8.90 +/- 0.06 ns to form the PBI triplet excited state, which can be used subsequently to generate singlet oxygen in 27% quantum yield. This sequence of events is eliminated by dissolving the PBI cyclophane in non-polar toluene, where only excited singlet state decay occurs. In contrast, complexation of electron-rich aromatic hydrocarbons by the host PBI cyclophane followed by photoexcitation of PBI results in ultrafast electron transfer (<10 ps) from the guest to the PBI in CH\(_2\)Cl\(_2\). The rate constants for charge separation and recombination increase as the guest molecules become easier to oxidize, demonstrating that charge separation occurs close to the peak of the Marcus curve and the recombination lies far into the Marcus inverted region.
KW  - photoinduced electron transfer
KW  - Marcus inverted region
KW  - cyclic perylene bisimide
KW  - PBI cyclophane
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191252
VL  - 7
IS  - 8
ER  - 
TY  - JOUR
A1  - Plötz, P.-A.
A1  - Polyutov, S. P.
A1  - Ivanov, S. D.
A1  - Fennel, F.
A1  - Wolter, S.
A1  - Niehaus, T.
A1  - Xie, Z.
A1  - Lochbrunner, S.
A1  - Würthner, Frank
A1  - Kühn, O.
T1  - Biphasic aggregation of a perylene bisimide dye identified by exciton-vibrational spectra
JF  - Physical Chemistry Chemical Physics
N2  - The quantum efficiency of light emission is a crucial parameter of supramolecular aggregates that can be tuned by the molecular design of the monomeric species. Here, we report on a strong variation of the fluorescence quantum yield due to different phases of aggregation for the case of a perylene bisimide dye. In particular, a change of the dominant aggregation character from H- to J-type within the first aggregation steps is found, explaining the observed dramatic change in quantum yield. This behaviour is rationalised by means of a systematic study of the intermolecular potential energy surfaces using the time-dependent density functional based tight-binding (TD-DFTB) method. This provides a correlation between structural changes and a coupling strength and supports the notion of H- type stacked dimers and J-type stack-slipped dimers. The exciton-vibrational level structure is modelled by means of an excitonic dimer model including two effective vibrational modes per monomer. Calculated absorption and fluorescence spectra are found to be in reasonable agreement with experimental ones, thus supporting the conclusion on the aggregation behaviour.
KW  - Potential-energy curves
KW  - Simulations
KW  - Molecular-dynamics
KW  - Systems
KW  - Fluorescence
KW  - Sracking
KW  - Pathway
KW  - Dimers
KW  - State
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187387
VL  - 18
IS  - 36
ER  - 
TY  - JOUR
A1  - Meza-Chincha, Ana-Lucia
A1  - Lindner, Joachim O.
A1  - Schindler, Dorothee
A1  - Schmidt, David
A1  - Krause, Ana-Maria
A1  - Röhr, Merle I. S.
A1  - Mitrić, Roland
A1  - Würthner, Frank
T1  - Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation
N2  - Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites.
KW  - water oxidation
KW  - self-assembly
KW  - solar fuels
KW  - supramolecular materials
KW  - catalysis
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204653
UR  - https://doi.org/10.1039/D0SC01097A
SN  - 2041-6539
ER  - 
TY  - JOUR
A1  - Hoche, Joscha
A1  - Schulz, Alexander
A1  - Dietrich, Lysanne Monika
A1  - Humeniuk, Alexander
A1  - Stolte, Matthias
A1  - Schmidt, David
A1  - Brixner, Tobias
A1  - Würthner, Frank
A1  - Mitric, Roland
T1  - The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes
JF  - Chemical Science
N2  - Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM),i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran   (DCBT).   We   measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law.This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier.
KW  - solvent-dependent fluorescence yield
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198707
UR  - https://doi.org/10.1039/C9SC05012D
VL  - 10
ER  - 
TY  - JOUR
A1  - Gershberg, Jana
A1  - Fennel, Franziska
A1  - Rehm, Thomas H.
A1  - Lochbrunner, Stefan
A1  - Würthner, Frank
T1  - Anti-cooperative supramolecular polymerization: a new K\(_2\)-K model applied to the self-assembly of perylene bisimide dye proceeding via well-defined hydrogen-bonded dimers
JF  - Chemical Science
N2  - A perylene bisimide dye bearing amide functionalities at the imide positions derived from amino acid L-alanine and a dialkoxy-substituted benzyl amine self-assembles into tightly bound dimers by π-π-stacking and hydrogen bonding in chloroform. In less polar or unpolar solvents like toluene and methylcyclohexane, and in their mixtures, these dimers further self-assemble into extended oligomeric aggregates in an anti-cooperative process in which even numbered aggregates are highly favoured. The stepwise transition from dimers into oligomers can not be properly described by conventional K\(_2\)-K model, and thus a new K\(_2\)-K aggregation model has been developed, which interpretes the present anti-cooperative supramolecular polymerization more appropriately. The newly developed K\(_2\)-K model will be useful to describe self-assembly processes of a plethora of other π-conjugated molecules that are characterized by a favored dimer species.
KW  - π–π Stacking
KW  - nucleation elongation
KW  - upramolecular polymerization process
KW  - dimerization
KW  - K2–K model
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191428
VL  - 7
IS  - 3
ER  - 
TY  - INPR
A1  - Stennett, Tom E.
A1  - Bissinger, Philipp
A1  - Griesbeck, Stefanie
A1  - Ullrich, Stefan
A1  - Krummenacher, Ivo
A1  - Auth, Michael
A1  - Sperlich, Andreas
A1  - Stolte, Matthias
A1  - Radacki, Krzysztof
A1  - Yao, Chang-Jiang
A1  - Würthner, Frank
A1  - Steffen, Andreas
A1  - Marder, Todd B.
A1  - Braunschweig, Holger
T1  - Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units
T2  - Angewandte Chemie, International Edition
N2  - In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts.
KW  - boron
KW  - near-IR chromophores
KW  - conjugation
KW  - low-valent compounds
KW  - synthesis
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-180391
N1  - This is the pre-peer reviewed version of the following article: T. E. Stennett, P. Bissinger, S. Griesbeck, S. Ullrich, I. Krummenacher, M. Auth, A. Sperlich, M. Stolte, K. Radacki, C.-J. Yao, F. Wuerthner, A. Steffen, T. B. Marder, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 6449. , which has been published in final form at  https://doi.org/10.1002/anie.201900889. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
ER  - 
TY  - JOUR
A1  - Grande, Vincenzo
A1  - Soberats, Bartolome
A1  - Herbst, Stefanie
A1  - Stepanenko, Vladimir
A1  - Würthner, Frank
T1  - Hydrogen-bonded perylene bisimide J-aggregate aqua material
N2  - A new twelvefold methoxy-triethyleneglycol-jacketed tetraphenoxy-perylene bisimide (MEG-PBI) amphiphile was synthesized that self-assembles into two types of supramolecular aggregates in water: red-coloured aggregates of low order and with weak exciton coupling among the PBIs and blue-coloured strongly coupled J-aggregates consisting of a highly ordered hydrogen-bonded triple helix of PBIs. At room temperature this PBI is miscible with water at any proportions which enables the development of robust dye aggregates in solution, in hydrogel states and in lyotropic liquid crystalline states. In the presence of 60–95 wt% water, self-standing coloured hydrogels exhibit colour changes from red to blue accompanied by a fluorescence light-up in the far-red region upon heating in the range of 30–50 °C. This phenomenon is triggered by an entropically driven temperature-induced hydrogen-bond-directed slipped stacking arrangement of the MEG-PBI chromophores within structurally well-defined J-aggregates. This versatile aqua material is the first example of a stable PBI J-aggregate in water. We anticipate that this study will open a new avenue for the development of biocompatible functional materials based on self-assembled dyes and inspire the construction of other hydrogen-bonded supramolecular materials in the highly competitive solvent water.
KW  - self-assembly
KW  - dyes
KW  - aqua material
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204715
UR  - https://doi.org/10.1039/C8SC02409J
SN  - 2041-6539
VL  - 9
ER  - 
TY  - JOUR
A1  - Farrell, Jeffrey  M.
A1  - Grande, Vincenzo
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - A Highly Warped Heptagon-Containing sp\(^2\) Carbon Scaffold via Vinylnaphthyl π-Extension
JF  - Angewandte Chemie International Edition
N2  - A new strategy is demonstrated for the synthesis of warped, negatively curved, all‐sp\(^2\)‐carbon π‐scaffolds. Multifold C−C coupling reactions are used to transform a polyaromatic borinic acid into a saddle‐shaped polyaromatic hydrocarbon (2 ) bearing two heptagonal rings. Notably, this Schwarzite substructure is synthesized in only two steps from an unfunctionalized alkene. A highly warped structure of 2 was revealed by X‐ray crystallographic studies and pronounced flexibility of this π‐scaffold was ascertained by experimental and computational studies. Compound 2 exhibits excellent solubility, visible range absorption and fluorescence, and readily undergoes two reversible one‐electron oxidations at mild potentials.
KW  - arenes
KW  - carbon
KW  - C-C coupling
KW  - curvature
KW  - polycyclic aromatic hydrocarbons
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206682
VL  - 58
IS  - 46
ER  - 
TY  - JOUR
A1  - Görl, Daniel
A1  - Soberats, Bartolome
A1  - Herbst, Stefanie
A1  - Stepanenko, Vladimir
A1  - Würthner, Frank
T1  - Perylene bisimide hydrogels and lyotropic liquid crystals with temperature-responsive color change
JF  - Chemical Science
N2  - The self-assembly of perylene bisimide (PBI) dyes bearing oligo ethylene glycol (OEG) units in water affords responsive functional nanostructures characterized by their lower critical solution temperature (LCST). Tuning of the LCST is realized by a supramolecular approach that relies on two structurally closely related PBI–OEG molecules. The two PBIs socially co-assemble in water and the resulting nanostructures exhibit a single LCST in between the transition temperatures of the aggregates formed by single components. This permits to precisely tune the transition from a hydrogel to a lyotropic liquid crystal state at temperatures between 26 and 51 °C by adjusting the molar fraction of the two PBIs. Owing to concomitant changes in PBI–PBI interactions this phase transition affords a pronounced color change with “fluorescence-on” response that can be utilized as a smart temperature sensory system.
KW  - perylene bisimide hydrogels
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-162459
VL  - 7
IS  - 11
ER  - 
TY  - JOUR
A1  - Pratihar, Pampa
A1  - Ghosh, Suhrit
A1  - Stepanenko, Vladimir
A1  - Patwardhan, Sameer
A1  - Grozema, Ferdinand C.
A1  - Siebbeles, Laurens D. A.
A1  - Würthner, Frank
T1  - Self-assembly and semiconductivity of an oligothiophene supergelator
N2  - A bis(trialkoxybenzamide)-functionalized quaterthiophene derivative was synthesized and its self-assembly properties in solution were studied. In non-polar solvents such as cyclohexane, this quaterthiophene π-system formed fibril aggregates with an H-type molecular arrangement due to synergistic effect of hydrogen bonding and π-stacking. The self-assembled fibres were found to gelate numerous organic solvents of diverse polarity. The charge transport ability of such elongated fibres of quaterthiophene π-system was explored by the pulse radiolysis time resolved microwave conductivity (PR-TRMC) technique and moderate mobility values were obtained. Furthermore, initial AFM and UV-vis spectroscopic studies of a mixture of our electron-rich quaterthiophene derivative with the electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) revealed a nanoscale segregated assembly of the individual building blocks in the blend.
KW  - Organische Chemie
KW  - charge transport; hydrogen bonding; oligothiophene; organogel; self-assembly
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-67817
ER  - 
TY  - JOUR
A1  - Wolter, Steffen
A1  - Aizezers, Janis
A1  - Fennel, Franziska
A1  - Seidel, Marcus
A1  - Würthner, Frank
A1  - Kühn, Oliver
A1  - Lochbrunner, Stefan
T1  - Size-dependent exciton dynamics in one-dimensional perylene bisimide aggregates
JF  - New Journal of Physics
N2  - The size-dependent exciton dynamics of one-dimensional aggregates of substituted perylene bisimides are studied by ultrafast transient absorption spectroscopy and kinetic Monte-Carlo simulations as a function of the excitation density and the temperature in the range of 25-90 degrees C. For low temperatures, the aggregates can be treated as infinite chains and the dynamics is dominated by diffusion-driven exciton-exciton annihilation. With increasing temperature the aggregates dissociate into small fragments consisting of very few monomers. This scenario is also supported by the time-dependent anisotropy deduced from polarization-dependent experiments.
KW  - rotational diffusion
KW  - spectroscopy
KW  - dyes
KW  - annihilation
KW  - migration
KW  - films
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-135190
VL  - 14
IS  - 105027
ER  - 
TY  - JOUR
A1  - Noll, Niklas
A1  - Krause, Ana-Maria
A1  - Beuerle, Florian
A1  - Würthner, Frank
T1  - Enzyme-like water preorganization in a synthetic molecular cleft for homogeneous water oxidation catalysis
JF  - Nature Catalysis
N2  - Inspired by the proficiency of natural enzymes, mimicking of nanoenvironments for precise substrate preorganisation is a promising strategy in catalyst design. However, artificial examples of enzyme-like activation of H\(_2\)O 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 H\(_2\)O molecules in front of the metal center 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 7th H\(_2\)O ligand directly coordinated to a RuIII center. Via a well-defined hydrogen-bonding network, another H\(_2\)O substrate is preorganized for the crucial O–O bond formation via nucleophilic attack.
KW  - water oxidation
KW  - enzyme
KW  - catalysis
KW  - molecular
KW  - catalyst synthesis
KW  - catalytic mechanisms
KW  - homogeneous catalysis
KW  - photocatalysis
KW  - supramolecular chemistry
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-302897
N1  - This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use (https://www.springernature.com/gp/open-research/policies/accepted-manuscript-terms), but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1038/s41929-022-00843-x
ET  - accepted version
ER  - 
TY  - JOUR
A1  - Hecht, Markus
A1  - Leowanawat, Pawaret
A1  - Gerlach, Tabea
A1  - Stepanenko, Vladimir
A1  - Stolte, Matthias
A1  - Lehmann, Matthias
A1  - Würthner, Frank
T1  - Self‐Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra‐Bay‐Acyloxy Perylene Bisimide
JF  - Angewandte Chemie International Edition
N2  - 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.
KW  - liquid crystals
KW  - noncovalent interactions
KW  - self-assembly
KW  - structure elucidation
KW  - supramolecular chemistry
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224586
VL  - 59
IS  - 39
SP  - 17084
EP  - 17090
ER  - 
TY  - JOUR
A1  - He, Tao
A1  - Stolte, Matthias
A1  - Burschka, Christian
A1  - Hansen, Nis Hauke
A1  - Musiol, Thomas
A1  - Kälblein, Daniel
A1  - Pflaum, Jens
A1  - Tao, Xutang
A1  - Brill, Jochen
A1  - Würthner, Frank
T1  - Single-crystal field-effect transistors of new Cl\(_{2}\)-NDI polymorph processed by sublimation in air
JF  - Nature Communications
N2  - Physical properties of active materials built up from small molecules are dictated by their molecular packing in the solid state. Here we demonstrate for the first time the growth of n-channel single-crystal field-effect transistors and organic thin-film transistors by sublimation of 2,6-dichloro-naphthalene diimide in air. Under these conditions, a new polymorph with two-dimensional brick-wall packing mode (\(\beta\)-phase) is obtained that is distinguished from the previously reported herringbone packing motif obtained from solution (\(\alpha\)-phase). We are able to fabricate single-crystal field-effect transistors with electron mobilities in air of up to 8.6 cm\(^{2}\)V\(^{-1}\)s\(^{-1}\) (\(\alpha\)-phase) and up to 3.5 cm\(^{2}\)V\(^{-1}\)s\(^{-1}\) (\(\beta\)-phase) on n-octadecyltriethoxysilane-modified substrates. On silicon dioxide, thin-film devices based on \(\beta\)-phase can be manufactured in air giving rise to electron mobilities of 0.37 cm\(^{2}\)V\(^{-1}\)s\(^{-1}\). The simple crystal and thin-film growth procedures by sublimation under ambient conditions avoid elaborate substrate modifications and costly vacuum equipment-based fabrication steps.
KW  - thin-film transistors
KW  - carrier transport
KW  - \(\beta\)-phase
KW  - organic semiconductors
KW  - induced phase transition
KW  - charge transport
KW  - materials design
KW  - \(\alpha\)-phase
KW  - mobility
KW  - pentacene
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-149255
VL  - 6
IS  - 5954
ER  - 
TY  - JOUR
A1  - Hong, Yongseok
A1  - Kim, Woojae
A1  - Kim, Taeyeon
A1  - Kaufmann, Christina
A1  - Kim, Hyungjun
A1  - Würthner, Frank
A1  - Kim, Dongho
T1  - Real-time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda-dimer by Ultrafast Time-Domain Raman Spectroscopy
JF  - Angewandte Chemie International Edition
N2  - 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.
KW  - excimer
KW  - vibrational coherence
KW  - time-resolved impulsive stimulated raman spectroscopy
KW  - structural dynamics
KW  - perylene bisimide
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318788
VL  - 61
IS  - 13
ER  - 
TY  - JOUR
A1  - Mützel, Carina
A1  - Farrell, Jeffrey M.
A1  - Shoyama, Kazutaka
A1  - Würthner, Frank
T1  - 12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon
JF  - Angewandte Chemie International Edition
N2  - 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 (B\(_{2}\)-HBP), employs six net C−H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr\(_{3}\)/AlCl\(_{3}\)/2,6-dichloropyridine-mediated C−H borylation steps. As predicted by our calculations, B\(_{2}\)-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B\(_{2}\)-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.
KW  - aromaticity
KW  - polycycles
KW  - pentacene
KW  - near infrared emitter
KW  - boron
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318808
VL  - 61
IS  - 8
ER  - 
TY  - JOUR
A1  - Liu, Bin
A1  - Vonhausen, Yvonne
A1  - Schulz, Alexander
A1  - Höbartner, Claudia
A1  - Würthner, Frank
T1  - Peptide Backbone Directed Self-Assembly of Merocyanine Oligomers into Duplex Structures
JF  - Angewandte Chemie International Edition
N2  - 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.
KW  - dipole-dipole interaction
KW  - peptide backbone
KW  - merocyanine
KW  - dye assembly
KW  - duplex structure
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318797
VL  - 61
IS  - 21
ER  - 
TY  - JOUR
A1  - Ouyang, Guanghui
A1  - Rühe, Jessica
A1  - Zhang, Yang
A1  - Lin, Mei-Jin
A1  - Liu, Minghua
A1  - Würthner, Frank
T1  - Intramolecular Energy and Solvent-Dependent Chirality Transfer within a BINOL-Perylene Hetero-Cyclophane
JF  - Angewandte Chemie International Edition
N2  - 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.
KW  - chirality transfer
KW  - solvent effects
KW  - perylene bisimide
KW  - energy transfer
KW  - cyclophanes
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318818
VL  - 61
IS  - 31
ER  - 
TY  - JOUR
A1  - Sung, Jooyoung
A1  - Kim, Pyosang
A1  - Fimmel, Benjamin
A1  - Würthner, Frank
A1  - Kim, Dongho
T1  - Direct observation of ultrafast coherent exciton dynamics in helical π-stacks of self-assembled perylene bisimides
JF  - Nature Communications
N2  - Ever since the discovery of dye self-assemblies in nature, there have been tremendous efforts to exploit biomimetic supramolecular assemblies for tailored artificial photon processing materials. This feature necessarily has resulted in an increasing demand for understanding exciton dynamics in the dye self-assemblies. In a sharp contrast with pi-type aggregates, however, the detailed observation of exciton dynamics in H-type aggregates has remained challenging. In this study, as we succeed in measuring transient fluorescence from Frenkel state of π-stacked perylene tetracarboxylic acid bisimide dimer and oligomer aggregates, we present an experimental demonstration on Frenkel exciton dynamics of archetypal columnar π-π stacks of dyes. The analysis of the vibronic peak ratio of the transient fluorescence spectra reveals that unlike the simple π-stacked dimer, the photoexcitation energy in the columnar π-stacked oligomer aggregates is initially delocalized over at least three molecular units and moves coherently along the chain in tens of femtoseconds, preceding excimer formation process.
KW  - systems
KW  - molecules
KW  - J-aggregate behavior
KW  - absorption
KW  - spectroscopy
KW  - photoluminescence
KW  - diffusion
KW  - fluorescence
KW  - excimer formation
KW  - organic semiconductors
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148157
VL  - 6
IS  - 8646
ER  -