1H, 13C, and 17O isotropic and anisotropic hyper-fine couplings for the plastosemiquinone anion radical

Hybrid density functional calculations (B3LYP) are performed for the plastosemiquinone anion radical in its free form and in models to simulate its hydrogen bonding environment in alcohol solvents. H-1, C-13 and O-17 isotropic and anisotropic hyperfine couplings are calculated. The effect of hydrogen bonding interactions in the alcohol solvent model is shown to lead to a redistribution of spin density from the oxygen atoms to the carbon atoms of the carbonyl groups. H-1 calculated hyperfine couplings are compared with previous assignments based on ENDOR measurements. A rearrangement of the experimental assignments for the methyl group couplings is indicated and a reinterpretation of the H-1 hydrogen bonding data is presented.