π electron spin density distributions and g values in semiquinone cations

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Abstract
Intuitive arguments suggest that the approximate linear relation between g and the π electron spin density on the oxygens observed in semiquinone anions must also be applicable to the corresponding cations. This has been substantiated by redetermining the spin density distribution in p‐benzosemiquinone cation and by demonstrating the linear relationship between g and the 1H hyperfine splittings aHOH associated with the hydroxyl protons of the cations. Our estimates of the spin density on the oxygens and QHOH are substantially different from the estimates reported in the literature. The 17O hyperfine splitting aO can be accounted for by using an additional parameter QOOH (∼50 G). Such a parameter was needed to account for the aO of semiquinone anions in hydrogen bonding solvents.