Mechanochromism, thermochromism, protonation effect and discrimination of CHCl3 from organic solvents in a Et2N-substituted Salicylaldehyde Schiff base

Abstract

Multi-stimuli-responsive materials, which can show color/fluorescence change in response to external chemical or physical stimuli, have received increasing attention due to the capacities for facile realization of multifunctional sensing. Herein, we presented a Et2N-substituted salicylaldehyde Schiff base compound (DDHAC) with multi-stimuli-responsive behaviors. An investigation of the photophysical properties in solution demonstrated DDHAC was an excited-state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) active molecule. Owing to structural flexibility from salicylaldehyde Schiff base, the compound displayed reversible mechanochromic and thermochromic behavior, which were associated with the crystalline-to-amorphous and crystalline-to-crystalline, respectively. Moreover, the Et2N group endowed DDHAC with the capability that response of protonation. Due to its protonation effect, DDHAC could serve as a unique optical probe for discriminating CHCl3 from organic solvents assisted by UV irradiation. The selectivity was attributed to the interaction of DPPTP with HCl gas from photodecomposition product of chloroform.