Para-benzoquinone and its semiquinone radical anion

In 1995-96, Scott Boesch provided the first tests of various density functional-based quantum chemical methods for calculating the structures, vibrations, and spin properties of p-benzoquinones and their semiquinone radical anions.(5 -56) Although several DF-based methods give comparably accurate 

Approximate mode descriptions and experimentally measured(65-55, 69-71) and scaled, calculated(54) vibrational frequencies(cm ) of p-benzoquinone (PBQ) and p-benzosemiquinone radical anion (PBSQ). Calculations were done using the B3LYP/6-31G(d) method. Frequencies greater than 1000 cm were scaled by 0.9613 and frequencies 

For p-benzosemiquinone radical anion, the B3LYP-derived vibrational modes are shifted to lower frequencies than in the neutral p-benzoquinone (see 

This work has been extended, primarily by O Malley, to model the effects of non-covalent contacts on hyperfine couplings and to calculate components of the hyperfine tensor.(74-77) O Malley achieves outstanding quantitative agreement between calculation and experiment for some hydrogen-bonding 

Experimental(72, 73) and calculated(56) isotropic hyperfine coupling constants and spin densities for the radical anion of p-benzoquinone. Hyperfine coupling constants were calculated using the B3LYP/(632l41)//6-31G(d) method. 

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