LAUSR

Abstract New D-π-A type aminostyrylquinoxaline derivatives (QDMA1, QDMA2, QTPA1 and QTPA2) were synthesized via Knoevenagel condensation reactions. It was found that their ICT (intramolecular charge transfer) emission were red-shifted significantly with increasing the solvent polarities. Interestingly, compound QTPA2 bearing two terminal triphenylamine groups exhibited reversible mechanofluorochromism. The emission of the as-synthesized crystals of QTPA2 was located at 542 nm, and it was red-shifted to 592 nm upon grinding, so the emitting color was changed from yellow to carmine. Meanwhile, the emission could be recovered when the ground powders were fumed with DCM vapor. XRD patterns and DSC curves in different solid states demonstrated that the mechanofluorochromism was due to the transformation between the crystalline and amorphous states. In addition, the protonation of the synthesized aminostyrylquinoxalines by TFA could lead to the colors of the solutions to change into dark green from yellow, accompanied with the quenching of the emission. Furthermore, we also found that the emission of QTPA2 in the film could be quenched significantly and rapidly stimulated by TFA vapor, and the detection limit and the decay time were estimated to be 167 ppb and 0.47 s, respectively. Therefore, the aminostyrylquinoxaline derivatives could be used as sensory materials to detect acids in solutions and in the films by naked eyes.