Molecular distyrylbenzene (DSB) derivatives are one of the most investigated π-conjugated materials with application in sensing, lasing, optical recording and organic electronic devices such as OFETs and OLEDs. Substitution of the distyrylbenzene scaffold, e.g. with electron-donating or withdrawing substituents, allows for fine-tuning of their optical properties and photoreactivities, both in solution and in the bulk. By introduction of steric strain to the central core of the distyrylbenzene axis, aggregation-induced emission (AIE) characteristics can be bestowed upon tetraarylated (E,E)-DSBs or diphenylated (E,E)-tetrastyrylbenzenes to a certain extent. As a consequence, they are non-fluorescent in solution, but highly emissive in cold matrices and upon aggregate-formation in poor solvents or in the crystalline state. However, the six-fold substitution of the central core takes its toll with respect to photostability: In the case of the tetraphenyl-DSBs, prolonged irradiation in solution and in the amorphous state leads to selective formation of tetrahydrobenzo[k]tetraphenes. This unwanted electrocyclization, common to most hexatriene systems, can be suppressed by substitution of the reactive positions with fluorine. Thus irreversible degradation is efficiently suppressed, AIE characteristics are retained and unexpected trans/cis-isomerization is observed.

Sterically overcrowded distyrylbenzenes: Tuning emission properties and photoreactivity

253rd National Meeting (2017)

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