中心原子对Keggin结构杂多阴离子的电子结构和催化性质的影响

使用SCC-DV-Xα方法计算了Keggin结构的杂多阴离子(SiMo12O40)^4^-,(GeMo12O40)^4^-, (AsMo12O40)^3^-的电子结构, 并与文献对(PMo12O40)^3^-的计算结果作了对比分析。讨论了中心原子对Keggin结构的杂多阴离子的电子结构和催化性质的影响。结果表明, 中心原子对Keggin结构杂多阴离子的电子云、静电势、总态密度的分布影响不明显; 但中心原子不同, 前线轨道HOMO, LUMO的组成有一定差异。四种阴离子的εLUMO和εFermi的相对大小关系为:(AsMo12O40)^3^->(PMo12-O40)^3^->(GeMo12O40)^4^->(SiMo12O40)^4^-, 其氧化能力和催化活性也具有相同的顺序。(XMO12-O40)^n^-(X=Si, Ge, P)中端氧Ot, 桥氧Ob, Mo以及X都具有催化活性, 在催化反应中都可能成为催化活性中心,而(AsMo12O40)^3^-中仅有As和Ob可作为催化活性中心。

Effects of central atoms on electronic structures and catalytic properties of Keggin-type heteropolyanions

The electronic structures of Keggin-type heteropolyanions (SiMo12O40)^4^-, (GeMo12O40)^4^- and (AsMo12O40)^3^- have been calculated by the SCC-DV-Xα method. According to the comparison among calculating results of the three heteropoly anions and those of (PMo12O40)^3^- which were adapted from the literature, we discussed the influence of the central atoms on the electronic structures and catalytic properties of Keggin structure anions. The results show that the influences of the central atoms on electron cloud, electrostatic potential, total density of states are not clear. But the central atom can affect the components of the frontier orbitals HOMO and LUMO. The relative sequence of energy of LUMO and Fermi level is as follows: (AsMo12-O40)^3^->(PMo12O40)^3^->(GeMo12O40)^4^->(SiMo12O40)^4^-. The sequences of oxidation and catalytic activity are the same as the above. For (XMo12O40)^n^- (X=P, Si, Ge), Ot (terminal oxygen), Ob (bridge oxygen), Ox (central oxygen), Mo and X have the potential to participate in the catalytic reactions, whereas to (AsMo12O40)^3^-, just As and Ob are exclusively active.