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^?V₁₄O₄₀]·19H₂O?3? and Na₅H₂[Ni^?V₁₄O₄₀]·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^??6?, Dy^??7?, Er^??8?, Y^??9?] and Na[Ln₃?H₂O?24][Mn₂V₂₂O₆₄] 22.5H₂ O [Ln = Yb^??10?, Lu^??11?] were successfully obtained using routine solution method.