六聚同多酸阴离子M6O19n-（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

The electronic structures, IR frequencies, HOMO-LUMO population of four hexaoxoanions (M₆O₁₉^n-, 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: Mo₆O₁₉^2- and W₆O₁₉ ^2- which are electron acceptors, and Nb₆O ₁₉^8- and Ta₆O₁₉^8- which are electron donors. LUMO orbitals of Mo₆O₁₉^2- and W₆O₁₉^2- consist of p orbitals of bridge oxygen atom and inner d orbitals of metal atom, whereas Nb₆O ₁₉^8- and Ta₆O₁₉^8- 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.