Triphenylamine derivatives: different molecular packing and the corresponding mechanoluminescent or mechanochromism property

Mechanoluminescence (ML), a fantastic phenomenon, has attracted increasing attention. However, to date, enumerable bright ML luminogens have been reported based on AIE building blocks. Herein, a new non-AIE unit of triphenylamine, for the first time, is utilized to construct a bright ML luminogen of TPA-1BA. Regardless of the similar molecular structure of TPA-1BA and its analogues TPA-2BA and TPA-3BA, totally different mechanoluminescent activities were observed. Through the careful analyses of their crystal structures, it is found that the non-centrosymmetric molecular arrangement and high lattice stability under mechanical stimulation should be mainly responsible for the ML property of TPA-1BA.