Mechanochemical synthesis of carbazole isomer Phosphor with Mechanofluorochromic and AIE Properties

Abstract

Carbazole and its isomer benzindole are widely used as the core backbone of organic phosphorescent materials, while tetraphenylethylene (TPE) is a well-known aggregation-induced emission (AIE) molecule. Although efforts have been made to combine these two molecules into a single compound, reports on the simultaneous realization of AIE and room temperature phosphorescence (RTP) are still rare. In this study, we have synthesized two new carbazole and its isomeric benzindole-substituted tetraphenylethylene derivatives, Cz-TPE and Bd-TPE, by mechanically assisted precursor synthesis. By doping these two molecules in a poly(vinyl alcohol) (PVA) matrix, the as-prepared materials have successfully achieved blue RTP-emitting properties. Detailed analyses of their single-crystal structures reveal significant intermolecular interactions that inhibit intramolecular motions and hinder the non-radiative decay pathway, thus enhancing phosphorescence in the aggregated state. Remarkably, the phosphorescence lifetime of Cz-TPE@PVA reaches 1.25 seconds. In addition to their AIE and phosphorescence properties, Cz-TPE and Bd-TPE show mechanofluorochromic (MFC) behavior. The multifunctional luminescent properties of AIE, RTP and MFC extend the potential of these materials for applications in organic optoelectronics and information technology. To the best of our knowledge, this is the first report on the mechanochemically assisted synthesis of carbazole isomers with simultaneous RTP, MFC and AIE.