Hydrothermal syntheses, crystal structures and properties of 0-D, 1-D and 2-D organic–inorganic hybrid borotungstates constructed from Keggin-type heteropolyanion [α-BW 12O 40] 5− and transition-metal complexes

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Three novel organic–inorganic hybrid borotungstates {[Ni(phen) 2(H 2O)] 2H(α-BW 12O 40)}·4H 2O ( 1), [Cu I(2,2'-bipy)(4,4′-bipy) 0.5] 2{[Cu I(2,2′-bipy)] 2Cu I(4,4′-bipy) 2(α-BW 12O 40)} ( 2) and {[Cu I(4,4′-bipy)] 3H 2(α-BW 12O 40)}·3.5H 2O ( 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(H 2O)] 2+ cations are grafted on the polyoxoanion [α-BW 12O 40] 5– through two terminal oxygen atoms, 2 shows a 1-D infinite chain constructed from [α-BW 12O 40] 5– polyoxoanions and {[Cu I(2,2′-bipy)] 2Cu I(4,4′-bipy) 2} 3+ cations by means of alternating fashion, and 3 displays an unprecedented 2D extended structure built by [α-BW 12O 40] 5– polyoxoanions and –Cu I–4,4′-bipy– linear chains, in which each [α-BW 12O 40] 5– polyoxoanion acts as a tetradentate inorganic ligand and provides three terminal oxygen atom and one two-bridging oxygen atom. The presence of Ni II and W VI in 1, Cu I ions and W VI in 2 and 3 are identified by XPS spectra. The photoluminescence of 2 and 3 are also investigated.