DFT–SQM force field for cobalt corrinoids

This Letter introduces a systematic development of a quantitative vibrational force field (FF) capable of modeling vibrational spectra of cobalt corrinoids (B12 derivatives). The scaled quantum mechanical (SQM) method is used to refine density functional theory (DFT) based force constants calculated at the B3LYP level of theory. The reliability of the DFT–SQM FF for cobalt corrinoids is tested on a six-coordinate methylcobalamin Im–[CoIII–corrin]–CH3 model. It is shown that the computed frequencies and Raman intensities permit detailed vibrational assignment. This analysis illustrates the utility of DFT–SQM FF in making detailed connections between the structure of cobalt corrinoids and their vibrational spectra.