Hydrothermal syntheses, crystal structures and properties of 0-D, 1-D and 2-D organic–inorganic hybrid borotungstates constructed from Keggin-type heteropolyanion [α-BW12O40]5− and transition-metal complexes

Three novel organic–inorganic hybrid borotungstates {[Ni(phen)2(H2O)]2H(α-BW12O40)}·4H2O (1), [CuI(2,2ʹ-bipy)(4,4′-bipy)0.5]2{[CuI(2,2′-bipy)]2CuI(4,4′-bipy)2(α-BW12O40)} (2) and {[CuI(4,4′-bipy)]3H2(α-BW12O40)}·3.5H2O (3) (phen=1,10-phenanthroline, 2,2′-bipy=2,2′-bipyridine, 4,4′-bipy=4,4′-bipyridine) have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, UV spectra, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), single-crystal X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and photoluminescence. The structural analysis reveals that 1 consists of a 0-D bisupporting polyoxometalate cluster where two [Ni(phen)2(H2O)]2+ cations are grafted on the polyoxoanion [α-BW12O40]5– through two terminal oxygen atoms, 2 shows a 1-D infinite chain constructed from [α-BW12O40]5– polyoxoanions and {[CuI(2,2′-bipy)]2CuI(4,4′-bipy)2}3+ cations by means of alternating fashion, and 3 displays an unprecedented 2D extended structure built by [α-BW12O40]5– polyoxoanions and –CuI–4,4′-bipy– linear chains, in which each [α-BW12O40]5– polyoxoanion acts as a tetradentate inorganic ligand and provides three terminal oxygen atom and one two-bridging oxygen atom. The presence of NiII and WVI in 1, CuI ions and WVI in 2 and 3 are identified by XPS spectra. The photoluminescence of 2 and 3 are also investigated.