AB-INITIO STUDY OF BROMINE DIOXIDES OBRO AND BROO

Bromine dioxides OBrO and BrOO are theoretically studied by means of v alence-only ab initio correlated calculations using TZ(2df) basis sets generated for O, Cl, and Br atoms, especially optimized for averaged relativistic effective core potentials (AREP). Equilibrium geometries for these dioxides are obtained using UMP2 and CCSD(T) electron correl ation methods, while harmonic frequencies and dipole moments are compu ted at the UMP2/AREP/TZ(2df) level. The effect of spin contamination o n UMP2 results for geometries and frequencies in these doublet radical s is also discussed. All the analyses dealing with energies are based on CCSD and CCSD(T) calculations. The energetic ordering of both bromi ne dioxides as well as the two possible dissociation channels, Br + O- 2 and BrO + O, are discussed. The nature of the bonding in the energet ically more stable BrOO isomer is also investigated by studying its en ergy surface; a small barrier between 1.2 and 1.7 kcal/mol for this di oxide dissociating into Br + O-2 is predicted.