Mechano-Responsive Luminescence via Crystal-to-Crystal Phase Transitions between Chiral and Non-Chiral Space Groups

Herein, a novel mechano-responsive luminescent (MRL) material based on crystal-to-crystal phase transitions between crystals of a chiral and those of a centrosymmetric space group, accompanied by a change of emission properties, is described. Initially, a gold complex containing a biphenyl moiety, which exhibits an achiral structure in solution, afforded an orange-emitting amorphous phase together with a viscous isotropic oil after evaporation of the solvent. Upon pricking, the orange-emitting oil spontaneously crystallized either in a centrosymmetric or in a chiral space group while simultaneously changing the emission properties. Remarkably, grinding the chiral crystals induced a solid-state phase transition to the achiral crystals under concomitant changes of the emission properties.