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Rational Design of Azothiophenes—Substitution Effects on the Switching Properties
Author(s) -
Heindl Andreas H.,
Wegner Hermann A.
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001148
Subject(s) - isomerization , photoisomerization , intersystem crossing , azobenzene , singlet state , photochemistry , moiety , chemistry , potential energy surface , lone pair , substitution (logic) , rational design , materials science , computational chemistry , molecule , nanotechnology , stereochemistry , organic chemistry , atomic physics , physics , catalysis , computer science , excited state , programming language
A series of substituted azothiophenes was prepared and investigated toward their isomerization behavior. Compared to azobenzene (AB), the presented compounds showed red‐shifted absorption and almost quantitative photoisomerization to their ( Z ) states. Furthermore, it was found that electron‐withdrawing substitution on the phenyl moiety increases, while electron‐donating substitution decreases the thermal half‐lives of the ( Z )‐isomers due to higher or lower stabilization by a lone pair– π interaction. Additionally, computational analysis of the isomerization revealed that a pure singlet state transition state is unlikely in azothiophenes. A pathway via intersystem crossing to a triplet energy surface of lower energy than the singlet surface provided a better fit with experimental data of the ( Z )→( E ) isomerization. The insights gained in this study provide the necessary guidelines to design effective thiophenylazo‐photoswitches for applications in photopharmacology, material sciences, or solar energy harvesting applications.