Cyano-Functionalized Diarylethene Derivatives with Aggregation-Induced Emission Enhancement and Piezofluorochromic Behaviours

Abstract

Four donor–acceptor (D-A) type phenothiazine derivatives were designed and synthesized and all of them exhibited an aggregation-induced emission enhancement (AIEE) effect and red-shifted piezofluorochromic (PFC) behaviour. Moreover, it was found that the compound containing a shorter alkyl chain displayed more remarkable PFC properties. This result was probably ascribed to highly twisted conformations which can lead to loose solid molecular packing with cavities and weak interactions. After they were pressed, the planarization of the molecular conformation increased and molecular conjugation degree enhanced, resulting in a red-shift in the photoluminescence spectrum. In addition, optimized geometric structures indicate that the compound with a longer alkyl chain has a more planer geometric structure, which leads to a smaller bathochromic shift upon grinding. In summary, we provide a new path to regulate the PFC behaviours of fluorescent materials by changing the length of their substituted alkyl chain.