Electronic and Magnetic Properties of α-Keggin Anions: A DFT Study of [XM12O40]n-, (M = W, Mo; X = AlIII, SiIV, PV, FeIII, CoII, CoIII ) and [SiM11VO40]m- (M = Mo and W)

Calculations based on density functional theory (DFT) have been carried out to investigate the electronic and magnetic properties of the α-Keggin anions mentioned in the title. The atomic populations and the distribution of the electron density computed for the studied clusters support the hypothesis that an oxidized Keggin anion is an XO4n- clathrate inside a neutral M12O36 cage. The energy gap between the band of occupied orbitals, formally delocalized over the oxo ligands, and the unoccupied d-metal orbitals, delocalized over the addenda, has been found to be independent of the central ion. However, substitution of a W or a Mo by V modifies the relative energy of the LUMO and then induces important changes in the redox properties of the cluster. In agreement with the most recent X-ray determination of [CoIIIW12O40]5- and with the simplicity of the 183W NMR and 17O NMR spectra observed for this anion the calculations suggest that [CoIIIW12O40]5- has a slightly distorted Td geometry. For the parent clust...