Molecular Transition Metal Oxides: Ab Initio and Density Functional Electronic Structure Study of Tungsten Oxide Clusters

Abstract

First principles quantum chemical calculations at the HF, MP2, and B3LYP levels of theory, using the LANL2DZ basis set, have been used to explore the potential energy hypersurfaces (PESs) of tungsten(VI) oxide species of molecular dimensions, formulated as WO3, WO42-, WO4H2, WO4Na2, W2O52+, and W2O6. The energetics of all topomers corresponding to global or local minima and saddle points in the potential energy hypersurfaces were computed at the more sophisticated QCISD(T) level. The proton affinity of the WO42- dianion was found to be equal to 1584, 1593, and 1586 kJ mol-1 at the MP2, B3LYP, and QCISD(T) levels of theory. The formation process of W2O6 by dimerization of WO3 species was predicted to be exothermic, the energy of formation being equal to 127.8, 100.3, 107.6, and 109.1 kcal·mol-1 at the HF, MP2, B3LYP, and QCISD(T) levels, respectively. Finally, the computed spectroscopic properties (harmonic vibrational frequencies and corresponding normal modes, electronic transitions and NMR chemical shif...