Ti^Ⅳ取代的Keggin型多金属氧酸盐的合成及其在水溶液中的行为

Synthesis of Ti^Ⅳ-Substituted Keggin-Type Polyoxometalates and the Behavior in the Water Solution

以钛酸异丙酯为Ti源,在酸性条件(pH=2)下合成了一钛取代的钨磷、钨硅多金属氧酸盐.用IR、31PNMR、1HNMR对样品的结构进行了表征,并对样品在水溶液中的存在形态以及在水溶液中的电子光谱和电化学性质进行了研究.结果表明,合成产物不仅具有饱和Keggin结构,而且钨磷酸盐以单体和二聚体混合物的形式存在,其二聚体在水溶液中会水解成为单体;而钨硅酸盐的二聚体在水溶液中却能稳定存在.它们在水溶液中的氧化还原过程包括TiIV的1电子还原和WVI的两步2电子还原,并与溶液的pH有关.

The Tire-substituted tungstophosphate and tungstosilicate were synthesized in acidic condition （ pH = 2 ） using Ti （ OPr^i ） 4as Ti source. The samples were characterized by IR spectroscopy, ^31P NMR and ^1H NMR. The states of the samples in water as well as the UV-vis spectroscopy and redox properties of the samples in the aqueous solution were also investigated. It is demonstrated that the Ti^Ⅳ -substituted compounds are of saturated Keggin structure; and the tungstophosphate samples were a mixture of protonated monomer and anhydride form dimer. The dimer of tungstophosphate can convert into the monomer in the aqueous solution; but the dimer of tungstosilicate is stable under the same condition. Their redox processes in the aqueous solution involve a one-electron reduction of TilVand two steps of two-electron reduction of W^Ⅳ, which are related to pH of the aqueous solution.