The Study Of The Substituted And Sandwiched Structural Compounds Based On Keggin-type Polyoxometalate Building Units

The rare earth- and transition metal-containing polyoxotungstates have attracted great attention not only stems from their intriguing variety of architectures, but also from their potential applications in the fields as diverse as catalysis, medicine, molecular magnetism and material science. In recent years, the synthesis of transition metal-containing polyoxotungstates has become an important research area of the synthesis of polyoxometalates.The aim of this thesis is the synthesis of new polyoxometalate compounds on the basis of lacunary Keggin-type polyoxoanion clusters, which are substituted by various transition metal ions or rare earth ions forming sandwich structure. The study on synthetic conditions and rules for these new compounds, and the exploration of relationships between structures and properties for these new compounds are also carried out.Ten polyoxometalate compounds have been synthesized on the basis of water solution synthesis methods and structurally characterized by elemental analyses, IR, TG, Raman and single crystal X-ray diffractions. The magnetic properties, fluorescent activity and antitumoral activity of these compounds have been studied.1. Four new polyoxometalate compounds on the basis of Keggin-type Gernanotungstate cluster have been synthesized and structurally characterized: A-α-Na₁₄[Na₂(UO₂)₂(GeW₉O₃₄)₂]·48H₂O (1) A-β-Na₁₄[Na₂(UO₂)₂(GeW₉O₃₄)₂]·42H₂O (2) K8[{γ-GeTi₂W₁₀O₃₆(OH)₂}₂(μ-O)₂]·34H₂O (3) K₁₂[α-GeNi₂W₁₀O₃₆]·10H₂O(4)Compounds 1 and 2 are sandwiched structural Germanotungstates, two UO₂²⁺ and two Na⁺ alternately array leading to a central belt of four metal atoms in the sandwich, and the two compounds are isomers each other. Compound 3 is the first compound of dititanium-substituted Keggin-type germanotungstate, which represents dimeric structure accommodating [γ-GeW₁₀O₃₆]^8- units. Compound 4 is a saturated 1:12 Keggin-type germanotungstate in which two WO6 octahedra are substituted by two NiO₆ octahedra.2. Two new polyoxometalate compounds on the basis of Keggin-type Silicatungstate cluster have been synthesized and structurally characterized: A-β-Na₍14[Na₂(UO₂)₂(SiW₉O₃₄)₂]·40H₂O (5) K₁₂[{β-SiCo₂W₁0)O₃₆(OH)₂(H₂O)}₂]·22.5H₂O (6)Compound 5 is isomorphic with compound 2. The structure of compound 6 can be described as a dimer of {β-SiCo₂W₁₀O₃₆(OH)2(H₂O)}^6- subunits related by an inversion center, each subunit is formed by a dilacunary [β-SiW(10)O₃₇]^10- coordinated to two Coâ…¡centers leading to a completeβ-Keggin ion.3. Four polyoxometalate compounds on the basis of Keggin-type tungstoantimonate cluster have been synthesized and structurally characterized: Na₉[{Na(H₂O)₂}₃{Co(H₂O)}₃(α-B-SbW₉O₃₃)₂]·28H₂O(7) [Co₄(H₂O)₁₀(β-B-SbW₉O₃₃)₂]^10- (8), Na₁₀[Sb₂W₂₀Co₂O₇₀(H₂O)₆]·34H₂O (9) Na₆[{Y(H₂O)₇}₄Sb₂ W₂₂O₇₄(OH)₂]·10H₂O(10)Compound 7-10 are sandwich structural tungstoantimonates. In compound 7 three Co²⁺ and three Na⁺ alternately array leading to a central belt of six metal atoms in the sandwich. In compound 8 four Co²⁺ ions occupy the sandwich position. In compound 9, two Co²⁺ and two Wâ…¥occupy sandwich position. In compound 10 four Wâ…¥occupy the sandwich position and the two outer Wâ…¥in the four Wâ…¥coordinate to two Y³⁺ ions, respectively.