The photolysis of the methylcobalamin cofactor (MeCbl) in its base-off form was investigated by considering the extent of spin-orbit coupling (SOC). Triplet Co-C photodissociation pathways previously invoked at the density functional theory level using Landau-Zener theory were further validated with ab initio calculations that combine SOC based on multi-state second order perturbation theory. It was determined that SOC is feasible between singlet and triplet states at elongated Co-C distances, leading to photodissociation from the state having dominant sigma(d(z)(2)) character, by either direct coupling with the lowest singlet states or by crossing with SOC mixed triplets. (C) 2016 AIP Publishing LLC.
展开▼
