Aerobic photolysis of methylcobalamin: structural and electronic properties of the Cbl-O-O-CH intermediate.

Photolysis of methylcobalamin (MeCbl) in the presence of molecular oxygen (O) 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-CH intermediate as a result of triplet O 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.