A stable tetraphenylethene derivative: aggregation-induced emission, different crystalline polymorphs, and totally different mechanoluminescence properties

Two crystalline polymorphs of TMPE, with the space groups P 2 1 ( c ) and C 2, are cultured from different solvent mixtures and display apparent blue fluorescence with the characteristic of aggregation induced emission (AIE). Excitedly, the P 2 1 ( c ) crystal exhibits easily observed mechanoluminescence (ML), while there is no mechanoluminescence for the C 2 crystal. Careful investigation of their crystal structures and three analogues demonstrates that the special molecule packing of TMPE in the P 2 1 ( c ) crystal accounts for its exciting efficient ML performance, providing some information to understand the structure-property relationship of efficient organic ML materials. Two crystalline polymorphs of TMPE (C p -form and C c -form) exhibit totally different mechanoluminescence properties.