The electronic structure of methylcobalamin (MeCbl), including the cobalt-methyl dissociation and the nature of the low-lying excited states, represents a challenge to theory and experiment. In particular, methods based on density functional theory (DFT) produce widely varying Co-CMe bond dissociation energies, which in most cases fall outside the experimental range of 32-40 kcal/mol, and, depending on the functional, can support any of the existing (and conflicting) interpretations of the S0?S1 electronic transition. Part of the problem is the absence of the reliable ab initio quantum chemistry information that could be used to assess the various DFT calculations and the available experimental data. This talk will attempt to address this unsatisfactory situation by discussing the insights into the cobalt-methyl dissociation and the low-lying excited states of MeCbl provided by the completely renormalized and equation-of-motion coupled-cluster approaches and multi-reference perturbation theory calculations, which will be compared with the DFT and experimental data.

Cobalt-methyl dissociation and electronic transitions in methylcobalamin: Insights from the coupled-cluster, multireference perturbation theory, and density functional theory calculations

245th National Meeting (2013)

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