A Highly Reversible Mechanochromic Difluorobenzothiadiazole Dye with Near-Infrared Emission.

A difluorobenzothiadiazole-based fluorescent material with a D-π-A-π-D structure exhibits a reversible mechanofluorochromic characteristic in the solid state. Its red fluorescent emission switches to near-infrared fluorescence upon mechanical stimulation, but recover after fuming the ground solid powder with dichloromethane.