Two organic–inorganic hybrids based on polyoxometalates: synthesis, crystal structure, and characterization

Abstract

Two new Keggin- and Wells-Dawson-type polyoxometalate-based organic–inorganic hybrid copper–organonitrogen complexes have been synthesized under hydrothermal conditions: [CuI(4,4′-bpy)]2[H2SiW12O40] ⋅ 2H2O (4,4′-bpy = 4,4′-bipyridine) (1) and (en =ethylenediamine), and characterized by elemental analysis, IR spectra, TGA, XRD, and single crystal X-ray diffraction. In 1, [Cu(4,4′-bpy)]+ cations form polymeric chains and a weak Cu–O linkage makes the anions situate between two chains, forming an infinite 1-D ladder-chain structure. Such 1-D ladder-chains are further interconnected via hydrogen bonding into a 3-D supramolecular framework. Compound 2 with covalently bonded 3-D structure consists of saturated Wells-Dawson tungstoarsenate polyoxoanions and copper complexes with two types (rigid and flexible) of ligands. The polyoxoanion has the highest connectivity for Wells-Dawson tungstoarsenate polyoxoanion coordination polymers to date. XPS spectra indicate that three W atoms in the Dawson unit were reduced and that there coexist CuI and CuII in 2.