Photostability of Hydroxocobalamin: Ultrafast Excited State Dynamics and Computational Studies

Hydroxocobalamin is a potential biocompatible source of photogenerated hydroxyl radicals localized in time and space. The photogeneration of hydroxyl radicals is studied using time-resolved spectroscopy and theoretical simulations. Radicals are only generated for wavelengths <350 nm through a mechanism that involves competition between prompt dissociation and internal conversion. Characterization of the lowest-lying singlet potential energy surface provides insight into the photochemistry of hydroxocobalamin and other cobalamin compounds.