The strong influence of the solvent on the electron spin resonance spectra of semiquinone radical anions I. A theoretical investigation of the hyperfine constants of 1,2- and 1,4-benzosemiquinone by using density functional theory and polarizable continuum solvation models

Abstract

The influence of the solvent medium on the isotropic hyperfine constants of 1,2- and 1,4-benzosemiquinone is investigated by theoretical calculations, using B3LYP density functional theory and electrostatic continuum solvation models. The computed hyperfine constants are highly sensitive to the impact of the solvent field, particularly in the case of 1,2-benzosemiquinone where the relative values are completely rearranged when the dielectric constant of the solvent, ϵ, is increased above unity. Consistency with experimental hyperfine data observed in aprotic as well as protic solvents is obtained by appropriate adjustment of the surface isodensity parameter in the isodensity polarizable continuum model (IPCM) of Foresman et al.