Thieno[3,2-c]pyran: an ESIPT based fluorescence "turn-on" molecular chemosensor with AIE properties for the selective recognition of Zn(2+)ion

Excited state intramolecular proton transfer (ESIPT) based functionalized thieno[3,2-c]pyranPwas designed and synthesized as a fluorescent turn-on chemosensor for the selective recognition of Zn(2+)ion with a low detection limit (0.67 mu M). Fourier transform infrared spectroscopy (FTIR), NMR, and Job plot studies were used to investigate the binding phenomenon ofPand Zn2+, which was achievedviadeprotonation of the hydroxyl group. Zn(2+)ions undergo interaction with thieno[3,2-c]pyran to afford the complexP-Zn2+, which enhances the weak emissive properties of the chemosensorPup to lambda(em)484 nmviageometrical alteration and termination of the keto to enol oscillation. In addition, thieno[3,2-c]pyranPalso showed higher fluorescence in a solution of 60% water in THF owing to the aggregation-induced emission phenomenon. All of these photophysical properties of chemosensorPand complexP-Zn(2+)are supported by quantum chemical density functional theory (DFT) calculations. The structure ofPwas also confirmed using single X-ray crystallography.