Novel Tridentate Bisoxime Chemosensor for Selective Recognition of Cu2+ and Zn2+ with Different Mechanisms

A novel tridentate bisoxime chemosensor HL has been developed as a two-in-one platform for colorimetric recognition of Cu2+ (from blue to green), and fluorescent recognition of Cu2+ (fluorescence quenching) and Zn2+ (fluorescence enhancement) in aqueous solution (CH3OH/H2O, 9:1, v/v). The UV-Vis and fluorescent spectra, IR, NMR, and density functional theory (DFT) calculations indicate that the recognition mechanism for quenching the fluorescence of the HL sensor for Cu2+ is a photoinduced electron transfer process (PET) between the recognition group (phenolic hydroxyl group and Schiff-base group) of the sensor and the signal reporter group (benzene ring), and the enhanced fluorescence recognition mechanism of the HL sensor for Zn2+ is of its hindered PET process.