六聚同多酸阴离子M_6O_(19)^(n-)(M=Mo,W,n=2;M=Nb,Ta,n=8)电子结构和化学性质的密度泛函理论研究

A DFT Study of the Electronic Structures and Chemical Properties of Hexaoxoanions, M_6O_(19)^(n-) (M=Mo, W, n=2; M=Nb, Ta, n=8)

采用B3LYP方法在LanL2DZ水平上计算了六聚同多阴离子 (M6On-19,M =Mo和W ,n =2 ;M =Nb和Ta ,n =8)的电子结构 ,分析了它们的前线轨道、分子静电势 (MEP) .计算结果表明 ,Nb6O8-19和Ta6O8-19是电子给体 ,而Mo6O2 -19和W6O2 -19则是电子受体 。

The electronic structures, IR frequencies, HOMO-LUMO population of four hexaoxoanions (M 6O n- 19, M=Mo and W, n=2; M=Nb and Ta, n=8) were studied by density functional theory method, B3LYP, at LanL2DZ level. According to the analysis of frontier orbitals and molecule electrostatic potential, these four anions can be classified into two types: Mo 6O 2- 19 and W 6O 2- 19 which are electron acceptors, and Nb 6O 8- 19 and Ta 6O 8- 19 which are electron donors. LUMO orbitals of Mo 6O 2- 19 and W 6O 2- 19 consist of p orbitals of bridge oxygen atom and inner d orbitals of metal atom, whereas Nb 6O 8- 19 and Ta 6O 8- 19 mainly consist of outer s and p orbitals of metal atom. Molecular electrostatic potential further exhibits the existing of electrophilic and nucleophilic sites in these anions. These results account for their different chemical properties such as the coordination ability and stability in aqueous solution.