Structural diversity, magnetic properties, and luminescence sensing based Ni(ii)/Zn(ii) coordination polymers of the semirigid 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzate ligand†
Abstract
Two two-dimensional Ni(II) or Zn(II)-based coordination polymers, namely [[Ni3(μ4-cpboda)2(μ2-H2O)2(DMF)2(H2O)2]·3DMF·2HCOOH·2H2O]n (1) and [[Zn3(μ4-cpboda)2(μ2-H2O)2(DMF)2(H2O)2]·3DMF·3HCOOH·3H2O]n (2), a three-dimensional Ni(II)-based coordination polymer, namely [[Ni3(μ3-cpboda)2(1,4-bib)5(H2O)2]·DMF]n (3), and a dinuclear Zn(II) complex, namely [Zn (μ2-Hcpboda)(2,2-bipy)(H2O)]2 (4) (H3cpboda = 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid, 2,2-bipy = 2,2-bipyridine, 1,4-bib = 1,4-di(1H-imidazol-1-yl)benzene), were successfully synthesized under solvothermal conditions and characterized via single-crystal X-ray and powder diffraction analyses, elemental analyses (EA), FT-IR spectroscopy, and thermogravimetric analysis (TGA). Complexes 1 and 2 show isomorphism and (3,4,6)-connected 2D sheet structures with the (32·4)2(32·83·9)2(34·4·282·94·103) topology. Complex 3 is a 4,4,7-connected 3D structure with the (42·52·62)2(46·5·614)2(54·6·8) topology. Complex 4 is only a simple dinuclear structure. Magnetization measurements disclose the weak ferromagnetic behavior between Ni(II) ions in the complexes 1 and 3. Fluorescence measurements indicate that 2 and 4 exhibit fast, sensitive, and selective luminescence quenching responses towards Cr2O72−/CrO42− in an aqueous solution. The limit of detection for Cr2O72−/CrO42− ions were estimated to be 0.51 and 0.60 ppm for 2 (0.89 and 1.03 ppm for 4), respectively, which are comparable to those reported for the CP-based fluorescent probes that can simultaneously detect Cr2O72−/CrO42− in aqueous environments. Moreover, 2 and 4 can be easily regenerated after the detection experiments, which is indicative of the excellent recyclability. All these results suggest that complexes 2 and 4 are highly selective and recyclable luminescence sensing materials for the quantitative detection of Cr2O72−/CrO42− anions in aqueous solutions.
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