Synthesis, structures and electrochemical properties of four organic-inorganic hybrid polyoxometalates constructed from polyoxotungstate clusters and transition metal complexes

Four novel organic-inorganic hybrid compounds [Cu-5(I)(4,4'-bpy)(3)(2,2'-bpy)(4)][BW12O40] center dot H2O (1), [Ni-0.5(2,2'-bpy)(1.25)][Ni(2,2'-bpy)(3)][Ni(2,2'-bpy)(2)(H2O)((SiW11WO40)-W-VI-O-V)] center dot 0.5H(2)O (2), [H(2)bpy](2)[Zn(2,2'-bpy)(3)](2)[Si2W18O62] center dot 1.5-H2O (3) and [Cu-II(2,2'-bpy)(2)](2)[SiW12O40] center dot 2H(2)O (4) (2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, electrochemical measurements and single-crystal X-ray diffraction. Compound ( 1) is a novel [BW12O40](5-) polyoxoanion bisupported by copper(I) coordination cations with mixed 2,2'-bpy and 4,4'-bpy ligands. Compound (2) is constructed from the [(SiW11WO40)-W-VI-O-V](5-) polyoxoanions supported by [Ni(2,2'-bpy)(2)](2+). Compound ( 3) is composed of a novel [Si2W18O62](8-) cluster and [Zn(2,2'-bpy)(3)](2+) complexes, which held together into a three-dimensional (3D) supra-molecular network through hydrogen-bonding interactions. Compound (4) shows a 2D layer framework constructed from a bisupporting Keggin polyoxoanion cluster and [Cu(2,2'-bpy)2](2+) coordination polymer fragments, resulting in 3D networks via supramolecular interactions.