A thiophene-substituted cyanostilbene derivative: Understanding the mechanism of its aggregation-induced emission, acidochromism and mechanochromism from the molecular level

In this work, a bibranched cyanostilbene derivative containing thiophene (TS-Th) was simply synthesized and characterized. The intramolecular charge transfer endows TS-Th with nearly 50 nm change from green to orange in solvatochromism. And TS-Th shows weak AIE effect due to the antagonism among hydrogen bond, C[sbnd]H···π interaction and thiophene induced π-π stacking, and its mechanism is proved by single crystal and morphology studies. These intermolecular forces in the solid state are broken by external forces, resulting in mechanochromism changing from orange to yellow, and its mechanism is the damage of stacking. TS-Th shows reversible acidochromism, and its mechanism is that -N(CH3)2 is protonated to increase the band gap turning on fluorescence. These fascinating properties make the application of TS-Th in fluorescent anti-counterfeiting and LED devices further explored. © 2025