Effect of Hydrogen Bonding on the Spin Density Distribution and Hyperfine Couplings of the p-Benzosemiquinone Anion Radical in Alcohol Solvents: A Hybrid Density Functional Study

Hybrid density functional calculations utilizing the B3LYP functional are used to calculate geometries, spin densities, and isotropic and anisotropic hyperfine couplings for the p -benzosemiquinone anion radical. Hydrogen-bonding interactions with methanol, ethanol, 2-propanol, and water are studied for their effects on the above properties. A redistribution of unpaired electron spin density from the oxygen and ring carbon atom positions to the carbonyl carbon atom position is shown to occur on hydrogen bond formation. Outstanding agreement between calculated and experimental hyperfine couplings is observed.