TY  - JOUR
A1  - Wildervanck, Martijn J.
A1  - Hecht, Reinhard
A1  - Nowak-Król, Agnieszka
T1  - Synthesis and strong solvatochromism of push-pull thienylthiazole boron complexes
JF  - Molecules
N2  - The solvatochromic behavior of two donor-π bridge-acceptor (D-π-A) compounds based on the 2-(3-boryl-2-thienyl)thiazole π-linker and indandione acceptor moiety are investigated. DFT/TD-DFT calculations were performed in combination with steady-state absorption and emission measurements, along with electrochemical studies, to elucidate the effect of two different strongly electron-donating hydrazonyl units on the solvatochromic and fluorescence behavior of these compounds. The Lippert–Mataga equation was used to estimate the change in dipole moments (Δµ) between ground and excited states based on the measured spectroscopic properties in solvents of varying polarity with the data being supported by theoretical studies. The two asymmetrical D-π-A molecules feature strong solvatochromic shifts in fluorescence of up to ~4300 cm\(^{−1}\) and a concomitant change of the emission color from yellow to red. These changes were accompanied by an increase in Stokes shift to reach values as large as ~5700–5800 cm\(^{−1}\). Quantum yields of ca. 0.75 could be observed for the N,N-dimethylhydrazonyl derivative in nonpolar solvents, which gradually decreased along with increasing solvent polarity, as opposed to the consistently reduced values obtained for the N,N-diphenylhydrazonyl derivative of up to ca. 0.20 in nonpolar solvents. These two push–pull molecules are contrasted with a structurally similar acceptor-π bridge-acceptor (A-π-A) compound.
KW  - solvatochromism
KW  - donor–acceptor
KW  - fluorescence
KW  - hydrazone
KW  - Lippert–Mataga plot
KW  - push–pull thienylthiazole
KW  - tetracoordinated boron
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286186
SN  - 1420-3049
VL  - 27
IS  - 17
ER  - 
TY  - JOUR
A1  - Stolte, Matthias
A1  - Hecht, Reinhard
A1  - Xie, Zengqi
A1  - Liu, Linlin
A1  - Kaufmann, Christina
A1  - Kudzus, Astrid
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - Crystal Engineering of 1D Exciton Systems Composed of Single‐ and Double‐Stranded Perylene Bisimide J‐Aggregates
JF  - Advanced Optical Materials
N2  - Single crystals of three at bay area tetraphenoxy‐substituted perylene bisimide dyes are grown by vacuum sublimation. X‐ray analysis reveals the self‐assembly of these highly twisted perylene bisimides (PBIs) in the solid state via imide–imide hydrogen bonding into hydrogen‐bonded PBI chains. The crystallographic insights disclose that the conformation and sterical congestion imparted by the phenoxy substituents can be controlled by ortho‐substituents. Accordingly, whilst sterically less demanding methyl and isopropyl substituents afford double‐stranded PBI chains of complementary P and M atropo‐enantiomers, single hydrogen‐bonded chains of homochiral PBIs are observed for the sterically more demanding ortho‐phenyl substituents. Investigation of the absorption and fluorescence properties of microcrystals and thin films of these PBIs allow for an unambiguous interpretation of these exciton systems. Thus, the J‐aggregates of the double‐stranded crystals exhibit a much larger (negative) exciton coupling than the single‐stranded one, which in contrast has the higher solid‐state fluorescence quantum yield.
KW  - fluorescence
KW  - J‐aggregates
KW  - perylene bisimides
KW  - reabsorption
KW  - single crystal structure
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218221
VL  - 8
IS  - 18
ER  -