Based on the density functional theory coupled with a discrete variational method (DFT-DVM), several vanadium-substituted α-Keggin-type heteropolyanion phosphomolybadate clusters [PVnMo12－nO40](3＋n)－ (n＝1～3) and their isomers were modeled. The effects of the vanadium-substitution on the oxidative property of the title species were investigated. The results showed that, the oxidative activity of the mono-vanadium-substituted cluster was the highest among the title species, while the oxidative activities of the di- and tri-vanadium-substituted clusters lied behind, with the former more active than the latter. Combining the calculated results with the available experimental electron reduction potential (ERP) data, it was found that the Fermi energy levels (Ef) of these species changed inversely with their ERP data, that is, the Ef gets higher with increasing the substituted vanadium number (n) of vanadium atoms, the corresponding ERP gets smaller. Further calculations on the tungsten heteropolyanion clusters as the α-Keggin-type [XW12O40]n－ (X＝CoII, FeIII, SiIV, PV) also showed the same relationship of Ef with ERP. Based on theoretical calculations, the new α-Keggin heteropolyanion species [SW12O40]2– was predicted and its Ef value was the smallest one among the tungsten heteropolyanion clusters, thus, it may possess the highest oxidative activity for the cluster series [XW12O40]n－ (X＝CoII, FeIII, SiIV, PV, SVI).

Key words: heteropolyanion, α-Keggin-type, vanadium-substitution effect, oxidative property, density functional theory (DFT)