Inorganic–organic hybrids constructed from heteropolymolybdate anions and copper–organic fragments: syntheses, structures and properties

Abstract

A series of inorganic–organic complexes based on polymolybdate anions and copper–organic subunits, [Cu(H₂O)(bim)₂]{[Cu(Hbim)₂][P₂Mo₅O₂₃]}·2H₂O (1), [Cu(Hbim)₂]{[Cu(bim)(H₂O)₂]₂[Cu(bim)₂]₂[(P₂Mo₅O₂₃)₂]}·20H₂O (2), [Cu(phen)(H₂O)][Cu(bim)₂]₂[P₂Mo₅O₂₃]·H₂O (3) and Mg[Cu(bim)(H₂O)]₂[P₂Mo₅O₂₃]·4H₂O (4) (bim = 2,2′-biimidazole, phen = 1,10-phenanthroline), have been synthesized under hydrothermal conditions and their crystal structures have been determined by single-crystal X-ray diffraction analysis. All of these compounds contain the [P₂Mo₅O₂₃]⁶⁻ polyoxoanions as building units. The structure determination shows that the polyoxoanion of compound 1 is mono-supported by one copper complex subunit. In compound 2, the [P₂Mo₅O₂₃]⁶⁻cluster is supported by two distinct [Cu(bim)(H₂O)₂]²⁺ and [Cu(bim)₂]²⁺ fragments. Compound 3 presents a tri-supported polyoxometalate cluster structure, where each [P₂Mo₅O₂₃]⁶⁻ anion is decorated by two [Cu(bim)₂]²⁺ and one [Cu(phen)(H₂O)]²⁺ cations. In compound 4, the [P₂Mo₅O₂₃]⁶⁻ anion is supported by four symmetry [Cu(bim)(H₂O)]²⁺ units. The cyclic voltammetry results for 1–4 indicate the known fingerprint of the [P₂Mo₅O₂₃]⁶⁻ anion. Although compounds 1–4 contain similar polyoxometalate anions, the mean peak potentials are slightly different, due to their different chemical environments. The magnetic behaviours of 1–4 were also investigated, in the temperature range of 2–300 K.