两个多钒盖帽的Keggin型多铌钒酸盐衍生物的水热合成与表征

通过水热方法合成了2个由多铌酸盐和过渡金属配合物形成的有机-无机杂化配合物[Cu(TETA)]₄[VNb₁₂(VO)₄O₄₀][OH]·10H₂O(1)和[Cu(TETA)]₄[VNb₁₂(VO)₆O₄₀][OH]₅·5H₂O(2)(TETA=三亚乙基四胺). 化合物1和2的多阴离子分别是由4个{VO₅}帽和6个{VO₅}帽加盖在Keggin型多铌酸盐的方形缺口上形成的, 它们通过多酸阴离子中Nb-O_t (O_t =端氧)与[Cu(TETA)]²⁺配合物的金属中心配位构筑形成三维结构. 价键计算结果表明, Keggin中心的钒为+5价, 帽位的钒为+4价, X射线光电子能谱分析(XPS)结果也证实了这一结论. 通过单晶X射线衍射分析、红外光谱(IR)、粉末X射线衍射(PXRD)、热重(TG)分析和元素分析对这2个化合物的结构和性质进行了表征.

Hydrothermal Syntheses and Characterization of Two Multi-vanadium Capped Keggin Polyoxoniobates Derivatives

Two organic-inorganic hybrid compounds constructed from polyoxoniobates and transition metal coordination complexes, [Cu(TETA)]₄[VNb₁₂(VO)₄O₄₀][OH]·10H₂O(1) and [Cu(TETA)]₄5[VNb₁₂(VO)₆O₄₀][OH]₅·5H₂O(2)(TETA=triethylenetetramine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analyses, IR spectra, X-ray photoelectron spectrum(XPS), powder X-ray diffraction(PXRD), thermogravimetric analysis(TGA) and elemental analyses. Compound 1 is a 3D tetra-capped vanadoniobates and compound 2 is a 3D hexa-capped vanadoniobates which are constructed from heteropolyoxometalates and [Cu(TETA)]²⁺ fragments. The result of bond valence sum calculations indicates that the vanadium centers of VO₄ tetrahedral in｛VNb₁₂｝Keggin unit in compounds 1 and 2 are in oxidation state +Ⅴ whereas the remaining vanadium centers are in oxidation state +Ⅳ. This is in line with the analysis of X-ray photoelectron spectrum.