Controlled assembly of two novel 3D hexad-supporting Keggin-polyoxometalate derivatives: {[Cu(4,4′-bipy)]3[HnXW12O40]}[4,4′-bipy]·2H2O (X = P, n = 0; X = Si, n = 1)

Two novel three-dimensional (3D) hexad-supporting organic-inorganic hybrid compounds based on the Keggin POMs modified by copper(I) transition metal and N-ligand organic moiety, {[Cu(4,4′-bipy)]3[PW12O40]}[4,4′-bipy]·2H2O (1) and {[Cu(4,4′-bipy)]3[HSiW12O40]}[4,4′-bipy]·2H2O (2) (bipy = bipyridine), have been synthesized under hydrothermal conditions by directly using Keggin POMs as starting materials. The two compounds are isomorphous and crystallized in the space group P1¯. They represent an important example of the family of polyanion-supported transition-metal solids, in which POMs covalently link six transitional metal-complex fragments. It is also interesting that the 3D structure constructed by hexad-supporting {[Cu(4,4′-bipy)]3[HnXW12O40]} subunits presents 1D channels in which neutral 4,4′-bipy molecules are located. They exhibit similar redox behavior, undergoing two one-electron reversible redox processes.