Reprecipitation-driven access to solvates and solvent-free crystals: achieving two-solvent-mediated vapochromic luminescence

Abstract

Vapochromic luminescent organic crystals have attracted significant attention in recent years for their potential in environmental monitoring and solvent sensing. Restoring the original emission color after vapor-induced changes typically requires additional stimuli such as heating, vacuum treatment, or prolonged exposure to air. Herein, three types of microcrystals obtained by reprecipitation of an organic luminophore exhibit two-solvent-mediated vapochromic luminescence, in which their emission color can be reversibly modulated by sequential exposure to two distinct organic solvent vapors. Interconversion between a chloroform-including green-emissive crystal and a solvent-free yellow-emissive crystal is achieved by exposure to ethyl acetate and chloroform vapors, respectively. Yellow- and orange-emissive solvent-free crystals that share the same crystal structure but differ in preferred orientation convert to green-emissive crystals upon exposure to chloroform vapor. Notably, both crystals revert to their original states upon exposure to ethyl acetate vapor, indicating retention of the initial crystal memory.