J. Am. Chem. Soc. 129 (2007) 13270 - 13276

Vanadium oxide clusters, (V₂O₅)_n, have been predicted to possess interesting polyhedral cage structures, which may serve as ideal molecular models for oxide surfaces and catalysts. The electronic properties of these oxide clusters as well as of Nb and Ta oxide clusters were examined via anion photoelectron spectroscopy and theoretical calculations using the TURBOMOLE program package. Very high electron affinities and large HOMO-LUMO gaps are observed for all the vanadium oxide clusters. The HOMO-LUMO gaps of (V₂O₅)_n, all exceeding that of the band gap of the bulk oxide, are found to increase with cluster size from n = 2-4. It has been found that the Nb and Ta oxide species yield similar spectra, both possessing lower electron affinities and larger HOMO-LUMO gaps relative to analogous clusters of vanadium oxide. The calculated electron binding energies and excitation spectra for the global minimum cage structures are in good agreement with the experiment. Interestingly, evidence is also observed for the predicted trend of electron delocalization versus localization in the anionic vanadium oxide clusters. Further insights are provided pertaining to the potential chemical reactivities of the oxide clusters and properties of the bulk oxides.