Selective fluorometric detection of F- and Zn(II) ions by a N, O coordinating sensor and naked eye detection of Cu(II) ions in mixed-aqueous solution

Through click chemistry, salicylaldehyde and fluorene groups have been explored to recognize anions through O-H center dot center dot center dot A- hydrogen-bonding complexation followed by an ESIPT mechanism and cation sensing via CHEF and CHEQ mechanisms for Zn2+ and Cu2+ metal ions respectively. Herein, we demonstrate evidence of the interactions between the O-H bond and F- which were studied by fluorescence spectroscopic, UV-Vis spectroscopic, lifetime spectroscopic, H-1 NMR spectroscopic titrations and theoretical treatment. This sensor could simultaneously detect two biologically important metal ions (Cu2+ and Zn2+) through colorimetric methods in mixed aqueous solution. The 2 : 1 binding stoichiometry ratio of the ligand and metal in the complexes was established by UV-Vis, fluorescence, H-1 NMR and ESI-MS spectroscopy, and their corresponding association constants, K-assoc observed at 8.13 x 10(4) and 5.12 x 106 M-1 corresponds to Zn2+ and Cu2+ metal ions in aqueous buffer-CH3OH (2 : 1, v/v) at pH 7.2. In addition, the electronic structures and photo physical properties of the ligand and complexes were calculated by DFT and time-dependent DFT (TDDFT) methods.