Aerobic photolysis of methylcobalamin: structural and electronic properties of the Cbl–O–O–CH3 intermediate

Abstract

Photolysis of methylcobalamin (MeCbl) in the presence of molecular oxygen (O₂) has been investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT). The key step involves the formation of the Cbl–O–O–CH₃ intermediate as a result of triplet O₂ insertion in the Co–C bond in the presence of light. Analysis of low-lying excited states shows that the presence of light is only needed to activate the Co–C bond via the formation of the ligand field (LF) state. The insertion of O₂, as well as the change in the spin state, takes place in the ground state. The analysis of the structural and electronic properties of the Cbl–O–O–CH₃ intermediate is presented and possible decomposition also discussed.