TY  - JOUR
A1  - Schulz, Alexander
A1  - Würthner, Frank
T1  - Folding-induced fluorescence enhancement in a series of merocyanine hetero-folda-trimers
JF  - Angewandte Chemie International Edition
N2  - Many dyes suffer from fast non-radiative decay pathways, thereby showing only short-lived excited states and weak photoluminescence. Here we show a pronounced fluorescence 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 spectroscopy (lifetime, quantum yield) the fluorescence enhancement was explained by the rigidification of the emitting chromophore in the defined foldamer architecture and the presence of a non-forbidden lowest exciton state in H-coupled hetero-aggregates. This folding-induced fluorescence enhancement (FIFE) for specific sequences of π-stacked dyes points at a viable strategy toward improved fluorophores that relates to the approach used by nature in the green fluorescent protein (GFP).
KW  - organic chemistry
KW  - merocyanines
KW  - aggregation
KW  - dyes/pigments
KW  - fluorescence
KW  - folding
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256582
VL  - 61
IS  - 2
ER  - 
TY  - JOUR
A1  - Bialas, David
A1  - Zitzler-Kunkel, André
A1  - Kirchner, Eva
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - Structural and quantum chemical analysis of exciton coupling in homo- and heteroaggregate stacks of merocyanines
JF  - Nature Communications
N2  - Exciton coupling is of fundamental importance and determines functional properties of organic dyes in (opto-)electronic and photovoltaic devices. Here we show that strong exciton coupling is not limited to the situation of equal chromophores as often assumed. Quadruple dye stacks were obtained from two bis(merocyanine) dyes with same or different chromophores, respectively, which dimerize in less-polar solvents resulting in the respective homo- and heteroaggregates. The structures of the quadruple dye stacks were assigned by NMR techniques and unambiguously confirmed by single-crystal X-ray analysis. The heteroaggregate stack formed from the bis(merocyanine) bearing two different chromophores exhibits remarkably different ultraviolet/vis absorption bands compared with those of the homoaggregate of the bis(merocyanine) comprising two identical chromophores. Quantum chemical analysis based on an extension of Kasha’s exciton theory appropriately describes the absorption properties of both types of stacks revealing strong exciton coupling also between different chromophores within the heteroaggregate.
KW  - exciton coupling
KW  - merocyanines
KW  - quantum chemical analysis
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170200
VL  - 7
ER  -