Based On Polyoxometalate Synthesis, Characterization And Nature Of The Study

The early transition metals (V, Nb, Ta, Mo, W) in their highest oxidation states are able to form metal-oxygen cluster anions, commonly referred to as polyoxoanions or polyoxometalates (POMs). These species are remarkable for their molecular and electronic structural diversity and their significance in quite diverse disciplines, e.g., catalysis, medicine, and materials science. Although the first POMs were reported over 160 years ago, they continue to display novel structures, and unexpected reactivities and applications. Recently, an intriguing area in this field is the construction of organic-inorganic materials based on POMs. Several successful strategies have been developed to design such materials. One of the promising methods is to connect POMs building units with secondary transition metal complexes acting as inorganic bridging groups via covalent bonds under hydrothermal or solvothermal conditions. The transition metal complexes can dramatically influence the inorganic oxide microstructure, so we can combine the merit of POMs and transition mental complexes to constitute some interesting compounds with unique properties. Many examples have been explored recently, including discrete clusters, one-dimensional chains, two-dimensional networks, and three-dimensional frameworks.We have extended the approach above by introducing a secondary metal cation as an additional structural component in the construction of a coordination complex cation which provides charge-compensation, space-filling and structure-directing roles. Herein, we report the the solvothermal synthesis and crystal structure of eight new compounds based on POMs: [Cu(phen)(H₂O)]₃[(PO₄)₂Mo₅O₁5]·5H₂O (1) HNa[Cu(bpy)(H₂O)]₂[(PO₄)₂Mo₅O₁5]·6H₂O (2) [CuI(bpy)₂]₂{[CuII(bpy)]₂PMoV₃MoVI₉O₄0} (3) H[Cu(bpy)(H₂O)]{[Cu(bpy)]₄(PO₄)₂}{PW₁1CuO₃9}·H₂O (4) {[Cu(phen)₂]₂Cl}[PMo₁2O₄0]·2H₂O (5) {[Cu(phen)₂]₂Cl}[PW₁2O₄0]·H₂O (6) [Cu(phen)(H₂O)2]2[H₂As₂Mo₆O₂6] (7) [Cu(phen)(OH)]₂[MoO₄]·3H₂O (8) (phen=1,10-phenanthroline, bpy=2,2'-bipyridine) These compounds are synthesized under solvothermal technique and characterized by elemental analyses, IR, XPS, EPR, TGA, magnetic susceptibility measurements and single crystal X-ray diffractions.The single crystal X-ray diffraction reveals that the compound 1 is built from a propeller-shaped chain constructed from {(PO4)₂Mo₅O₁5}6- clusters linked through {Cu(phen)(H₂O)}2+ components as blades. Also the compound 2 is based on {(PO4)2Mo5O15}6- polyoxoanion, further connected by {Cu(bpy)(H₂O)}2+ subunits. The compound 3 is built from the reducedα-Keggin polyoxoanion [PMoV3MoVI9O40]6- bicapped by two [CuII(bpy)]2+ through four bridging oxo groups on two opposite [Mo4O4] faces. And 3 shows intense photoluminescent property in the solid state at room temperature. While compound 4 is based on monovacant Keggin anion {PW₁1CuO₃9}5- linked through Cu(bpy)2+ and PO₄3-, generating one-dimensional chain. Magnetism measurement indicates that there exists predominantly antiferromagnetic interaction in 4. Both of compound 5 and 6 are composed of {[Cu(phen)₂]₂Cl} counterions andα-Keggin polyoxoanion {PM12O40}3- (M = Mo, W). The compound 7 is one-dimensional chain based [H₂As₂Mo₆O₂6]4- clusters linked by {Cu(phen)(H₂O)₂}2+ components. And compound 8 consists of two [Cu(phen)]2+ ions bridged by one MoO42- and two OH-.