Ab initio calculations on bromine oxide and dioxides and their corresponding anions

Neutral bromine oxides and dioxides as well as their corresponding anions have been studied by means of ab initio molecular orbital calculations. To test the importance of static and dynamic correlation in these systems both single-configuration-based methods [MP2, QCISD, and QCISD(T)] and multiconfiguration-based methods (CASSCF and CASMP2) have been used. Equilibrium geometries and harmonic vibrational frequencies have been obtained for BrO and the two bromine dioxide isomers (OBrO and BrOO). For the corresponding anionic species, excellent agreement has been obtained for the predicted geometries at QCISD(T) and CASMP2 levels, while frequencies obtained at QCISD(T) agree to within 10 cm−1 with the available experimental data. An analysis of the charge density shows that the nature of the BrO bond is very different within OBrO and BrOO, and that the BrO charge density is reinforced in OBrO relative to BrO itself.