Three new Zn(ii) coordination polymers for highly selective and sensitive detection of Fe3+

Abstract

Water pollution caused by Fe³⁺ is a severe problem in the modern world. Therefore, quantitative analysis of Fe³⁺ concentration in water is necessary to monitor water quality. In recent years, coordination polymers (CPs) have been proven to be a class of excellent candidates for luminescent sensors. In this work, three CPs, namely, {[Zn₃(L1)₂(H₂O)₃]·0.5H₂O}_n (1), {[Zn₃(L1)₂(dib)_2.5(H₂O)]·0.5H₂O}_n (2), and {[Zn₂(L2)(OH)(H₂O)]·0.5H₂O}_n (3), have been synthesized under hydrothermal conditions (H₃L1 = 5-((2-carboxyphenoxy)methyl)benzene-1,3-dioic acid, H₃L2 = 5-((3-carboxyphenoxy)methyl)benzene-1,3-dioic acid, and dib = 1,4-di(1H-imidazol-1-yl)butane). Compound 1 shows a novel (3,12)-connected 3D framework based on a hexanuclear Zn(II) cluster with the point symbol of {4³}₄{4²⁰·6²⁸·8¹⁸}. Compound 2 reveals a (3,3,4,4)-connected 3D framework with the {6·9²}₂{6⁴·8·10}{6⁴·8·9}{9·11·12} topology. Compound 3 exhibits a (3,6)-connected 2D layer based on a tetranuclear Zn(II) cluster with the {4³}₂{4⁶·6⁶·8³} topology. The luminescence responses of compounds 1–3 towards Fe³⁺ were investigated in aqueous solutions. The results show that compounds 1–3 are good luminescent sensors for detection of Fe³⁺. The low limits of detection (LOD) for Fe³⁺ are 4.07, 1.14, and 40.70 μM, respectively.