有机大阳离子与HnXW12O40·nH2O（X=B，Si，P）多金属氧酸盐的合成及热行为

合成了3种新的多金属氧酸盐(CTMA)5BW12O40·8H2O,(CTMA)4SiW12O40·3H2O,(CTMA)3PW12O40·2H2O,利用元素分析、IR光谱和TG-DTA技术对其进行了表征.IR光谱表明这些化合物不仅含有Keggin型结构,而且存在有机大阳离子的特征吸收峰;TG-DTA曲线显示它们的热行为是一个多步分解过程,首先这些化合物在大约269℃以下脱去水分子,然后它们的无水多金属氧酸盐经历了两步或3步的分解过程,分别脱去CTMA分子及其碎片,并伴随Keggin型结构的塌陷.通过XRD和IR光谱确证其最终分解产物是一个含有WO3与B2O3,SiO2或P2O5的混合物.同时还提出了这些化合物可能的热分解过程.

Synthesis and Thermal Behavior for Polyoxometalates of Large Organic Cation with HnXW12O40 (X=B, Si, P)

Three new polyoxometalates, (CTMA)5BW12O40·8H2O, (CTMA)4SiW12O40·3H2O, (CTMA)3PW12O40·2H2O, were prepared from by elemental analysis, IR spectra and TG-DTA. The 1R spectrum showed the identification of not only the presence of Keggin-type anion of heteropoly acids but also the characteristic functional group of large organic cation in these compounds. The TG/DTA curves indicated that their thermal decomposition was a more-steps process consisting of simultaneous processes involving also Keggin anion. At first,these compounds had a mass loss of water molecules at the temperature below ～269℃, then the thermal decomposition of their anhydrous polyoxometalates had a two or three stages process, which corresponded to CTMA molecules, its fragments and heteropoly oxometallates decomposition. The end-product of thermal decomposition was a mixture of WO3 and B2O3, SiO2 or P2O5, confirmed by X-ray diffraction and IR spectroscopy. And the possible thermal decomposition mechanisms of the complexes are proposed.