Polymorphism-Dependent and Switchable Emission of Butterfly-Like Bis(diarylmethylene)dihydroanthracenes

Abstract

Organic fluorophores with reversible emission switching behavior are promising materials for applications in sensors, optical recording, security inks, and optoelectronics. A variety of aggregation-induced emission (AIE) luminogens with mechanochromic luminescence has been prepared, and the transformation of efficient bluer-emitting crystals to amorphous powders with redder and weaker emission is proposed to be the cause for such behavior. However, detailed mechanistic understanding from experimental to theoretical is lacking. In this work, we present the design and synthesis of a group of bis(diarylmethylene)dihydroanthracenes with butterfly-like shapes. These molecules exhibit aggregation-induced emission characteristics due to the restriction of intramolecular motion in the aggregated state. They show mechanochromism, because of the transformation between crystal and amorphous states with different colors and efficiencies aided by grinding/heating or solvent fuming processes. By investigation of their ...