A Zn(II) Coordination Polymer for Fluorescent Turn-Off Selective Sensing of Heavy Metal Cation and Toxic Inorganic Anions

A novel coordination polymer [Zn(atyha)₂]_n (1) (Hatyha = 2-(2-aminothiazole-4-yl)-2- hydroxyiminoacetic acid) was constructed by hydrothermal reaction of Zn²⁺ with Hatyha ligand. CP 1 exhibits a 2D (4,4)-connected topological framework with Schläfli symbol of {4⁴·6²}, where atyha^- anions serve as tridentate ligands, bridging with Zn²⁺ through carboxylate, thiazole and oxime groups. CP 1 displays a strong ligand-based photoluminescence at 390 nm in the solid state, and remains significantly structurally stable in water. Interestingly, it can be utilized as a fluorescent probe for selective and sensitive sensing of Fe³⁺, Cr₂O₇^2- and MnO₄^- through the fluorescent turn-off effect with limit of detection (LOD) of 3.66 × 10^-6, 2.38 × 10^-5 and 2.94 × 10^-6 M, respectively. Moreover, the efficient recyclability for detection of Fe³⁺ and Cr₂O₇^2- is better than that for MnO₄^-. The mechanisms of fluorescent quenching involve reversible overlap of UV-Vis absorption bands of the analytes (Fe³⁺, Cr₂O₇^2- and MnO₄^-) with fluorescence excitation and emission bands for CP 1, respectively.