The bonding character of the cyclic AlSO and GaSO species: ab initio investigations at density functional theory and the electron correlation levels

The structural properties have been predicted for cyclic AlSO and GaSO at DFT, MPn, QCISD(T) and CCSD(T) levels with a 6-311+G* basis. Results indicate that the cyclic AlSO species possesses a 2A″ ground state with a 2A′ excited state higher by 16.2 kcal/mol at CCSD(T)/6-311+G* level, while the cyclic GaSO only has a 2A″ ground state without a 2A′ excited state. Various calculations yield dissociation energies within 4.0 kcal/mol of 65.8 and 52.3 kcal/mol for two ground states, respectively. These two cyclic AlSO and GaSO species in the ground states should be classified as thiosuperoxide. However, they are not as ionic as LiO2, LiSO and are also less ionic than the cyclic AlO2.