Multi-stimuli responsive cyanostilbene derivatives: pH, amine vapor sensing and mechanoluminescence

Abstract

Two multi-stimuli responsive compounds 1 and 2, obtained by the introduction of a carboxyl group to a cyanostilbene skeleton, revealed a fluorescence response to a change in the pH, amine vapors and mechanical stimulus. After scrutinizing their single crystal structures and comparing them with those of reference compounds 3 and 4, the molecules were found to demonstrate face-to-face stacking through multiple π–π interactions to restrain the non-radiative relaxation of the excited state, which led to mechanoluminescence (ML) during the fracturing process of the crystal. The discovery of these novel ML luminogens provides guidance for the design of pure organic ML materials.