Mechanochromic Wide-Spectrum Luminescence Based on a Monoboron Complex

A reversible mechanochromic luminescent material based on a simple tetrahedral monoboron complex (B-1) is described. Interestingly, in addition to amorphous powders (P), the compound could exist in three unique crystal states (A, B, and C), showing efficient green-to-red luminescent colors, which is a result of wane and wax of dual emissions of the compound. Surprisingly, one of the emissions increases significantly with increasing temperature, fully offsetting the quenching effect of temperature-assisted internal conversion process. The four states are fully interconvertible through grinding and heating, allowing color writing/painting with a single ink.