A new fluorescent chemosensor for transition metal cations and on/off molecular switch controlled by pH

A new fluorescent chemosensor with imidazole as ionophore was synthesized by the selective derivation of calixarene, which can effectively recognize Cu2+ and Zn2+ leading to different fluoroscopic behaviors in CH3OH–H2O. This system could be considered as a molecular switch. By modulating the pH of the solution, on–off–on fluorescent switching is carried out upon combinatory addition of acid, base and Cu2+.