Synthesis and characterization of an organic-inorganic hybrid compound: [WO₃ (2,2′-bipy)] (2,2′-bipy = 2,2′-bipyridine)

The hydrothermal synthesis and characterization of an organic-inorganic hybrid compound [WO₃(2,2′-bipy)] (2,2′-bipy=2,2′-bipyridine) is presented. This compound was characterized by various techniques including Raman and IR spectroscopy, XRD and thermogravimetric analysis. Structural analysis of the compound by Raman and IR data shows that it has a novel tungstate structure with 2,2′-bipy coordinated to tungsten. The X-ray powder diffraction data of the compound are indexed to a monoclinic cell with a = 14.313(4), b = 9.603(2), c = 7.288(2) Å, β = 102.07(2)°. The structure of [WO₃(2,2′-bipy)] adopts a chain-like framework consisting of corner-shared distorted octahedra (WO₄N₂) with 2,2′-bipy acting as a bidentate ligand whose rings fan out from the chain. Upon heating, [WO₃(2,2′-bipy)] retains its structural integrity until 300°C, followed by a gradual loss of 2,2′-bipy which leads to the formation of WO₃ at ca. 475°C. The thermal decomposition is observed to proceed through a transitional intermediate, [W₄O₁₂(2,2′-bipy)], the structure of which is proposed and discussed.