A theoretical study of molecular titanium oxide clusters: structure, bonding, vibrations and stability

Abstract

First principles quantum chemical calculations at the HF, MP2 and B3LYP levels of theory, using the LANL2DZ basis set, were used to explore the potential energy hypersurfaces (PESs) of ionic titanium(IV) oxide clusters of molecular dimensions, formulated as TiO₃^2-, Ti₂O₃²⁺, Ti₂O₅^2- and Ti₂O₆^4-. The neutral protonated species of the anions were also investigated at the same level of theory. 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 protonation of the anionic metal oxide clusters produces neutral species and the computed proton affinities were in the range 1720–2000 kJ mol^-1. The computed structural, energetic and spectroscopic properties of the clusters are in line with available experimental and theoretical results. The formation processess of the Ti₂O₅^2- dianion from TiO₃^2- and TiO₂ species and the Ti₂O₆^4- tetraanion by dimerization of the TiO₃^2- species are predicted to be exothermic and endothermic, respectively.