AIE-active asymmetric A-π-A′ molecule with mechanoluminescent property

It is of great significance to explore the inherent relationship between organic molecular structure and photoluminescence mechanism. As we known, the push-pull electron groups of organic molecules have an obvious impact on molecular charge transfer. In this work, an asymmetric A-pi-A' molecule architecture was formed by using electron-rich carbazolyl as II-spacer (II) and p-fluorobenzesulfonyl and pyridinyl as acceptor (A) chromophores. The molecule has aggregation-induced emission (AIE) and mechanoluminescent features. Notably, the switching of the excited states from the locally excited state to the twisted intramolecular charge transfer state plays important roles in the AIE properties. Based on single crystal data and DFT calculations, we found that the change of intermolecular charge transfer (CT) to intramolecular charge transfer (ICT) states is the main cause of the mechanoluminescent performance. These results indicate that the molecular structure of A-pi-A' plays an important role in AIE and mechanoluminescence.