High-contrast and reversible mechanochromic luminescence of a D–π–A compound with a twisted molecular conformation

Abstract

By integrating a triphenylamino donor (D) and a (2,2-dicyanovinyl)phenyl acceptor (A) with an anthryl π-spacer, a mechanochromic luminescent (ML) D–π–A compound, TPAANDCV, has been constructed. The single crystals of TPAANDCV display efficient green emission with a good fluorescence quantum yield (Φ_F) of 0.35. Upon grinding the crystals, a dramatic emission-colour variation from green to orange-red has been observed, and such a variation can be erased through annealing or solvent-vapour fuming. Moreover, the emission of the ground sample is also bright with a Φ_F value of 0.11. The powder XRD measurements indicate that the emission-colour change upon grinding is caused by a partial conversion of the ordered solid-state structures to an amorphous state. The high-contrast and reversible fluorescent response of TPAANDCV towards mechanical stress, as well as the bright emission of both the unground and ground states, enable TPAANDCV to be a good ML material.