Synthesis, Crystal Structures And Properties Of Transition Metal Centered Polyoxovanadates And Derivatives Of Rare-Earth Metals

In this paper, we conduct our researches starting from simple metavanadate and precursors of polyoxovanadates（POVs） by combination of transition-metal or rare-metal ions, three kinds of compounds were successfully obtained by systematically tuning reaction conditions with the routine solution methods. All of them are characterized by X-ray single crystal diffraction, spectroscopic properties（IR, UV and XRD）, thermogravimetric analysis（TG）, fluorescence properties, ICP and magnetic properties.1. Four transition-metal Mn or Ni centered POVs were constructed from potassium metavanadate or sodium metavanadate by the routine solution method: K₂H₄[MnV₁₄O₄₀]·22.5H₂O（1）, Na₅H[MnV₁₄O₄₀]·28H₂O（2）, K₂H₅[Ni^ⅢV₁₄O₄₀]·19H₂O（3） and Na₅H₂[Ni^ⅢV₁₄O₄₀]·30H₂O（4）. Compounds 1 and 3 are isostructure. Polyanions of 1-4 contain two monolacunary Lindqvist-type {V₅O18} units and a distorted square-grid Sandwich layer {TMV₄O₂₂}, which are further extended to 2D structure connected by K+ or Na+ cations. Magnetic studies indicate that paramagnetic interaction exist in compound 1 and 2 and antiferromagnetic interaction exists in compound 3 and 4.2. Attempting compound 1 as the starting material, one novel purely inorganic rare-metal derivative of POVs K2{Nd6（H₂O）28[MnV₁₂O₃₈][MnV₁₄O₄₀]（ClO₄）₂}·10H₂O（5） was synthesized conventionally by the routine solution method. This compound shows one-dimensional polymeric structure constructed by hydrated lanthanide cations and two types of heteropoly anions, namely [Mn V₁₄O₄₀]6- and [MnV₁₂O₃₈]^12-.3. By reaction of compound 1 and RE（ClO₄）3·6H₂O, six S-shape ionic-type POVs based on {Mn₂V₂₂O₆₄}: Na[Ln3（H₂O）25][Mn₂V₂₂O₆₄] 23.5H₂ O [Ln = Gd^Ⅲ（6）, Dy^Ⅲ（7）, Er^Ⅲ（8）, Y^Ⅲ（9）] and Na[Ln₃（H₂O）24][Mn₂V₂₂O₆₄] 22.5H₂ O [Ln = Yb^Ⅲ（10）, Lu^Ⅲ（11）] were successfully obtained using routine solution method.