Very bright mechanoluminescence and remarkable mechanochromism using a tetraphenylethene derivative with aggregation-induced emission.

Organic materials exhibiting mechanoluminescence (ML) are promising for usage in displays, lighting and sensing. However, the mechanism for ML generation remains unclear, and the light-emitting performance of organic ML materials in the solid state has been severely limited by an aggregation-caused quenching (ACQ) effect. Herein, we present two strongly photoluminescent polymorphs (, C and C) with distinctly different ML activities based on a tetraphenylethene derivative PTA. As an aggregation-induced emission (AIE) emitter, PTA perfectly surmounted the ACQ, making the resultant block-like crystals in the C phase exhibit brilliant green ML under daylight at room temperature. The ML-inactive prism-like crystals C can also have their ML turned on by transitioning toward C with the aid of dichloromethane vapor. Moreover, the C polymorph shows ML and mechanochromism simultaneously and respectively without and with UV irradiation under a force stimulus, thus suggesting a feasible design direction for the development of efficient and multifunctional ML materials.