Solvatochromism and mechanochromism observed in a triphenylamine derivative

A donor–π–acceptor fluorescent dye, 4-[N,N-di(4-phenyl)amino]benzaldehyde 4-chloro­benzoyl hydrazone (TPA-CBH), based on a tri­phenyl­amine derivative (TPA) and 4-chloro­benzoyl hydrazine (CBH) was designed and synthesized. The optical properties of this luminogen were investigated in solutions as well as in the solid states. In the intramolecular charge-transfer (CT) mechanism, TPA-CBH exhibits solvatochromism when dissolved in various polar solvents. Aggregation-induced emission was observed with the changes of tetrahydrofuran/water ratios. In the solid state, mechanochromic fluorescence is observed when the samples are stressed under different conditions. Based on structural analyses and theoretical calculations, it is found that intra- and intermolecular CT processes play a key role in the diversity of fluorescent properties.