ESR Spectra and structure of radical-anions of fluorinated benzonitrile derivatives

Isotropic ESR spectra have been taken from radical-anions of fluorinated benzonitrile derivatives. Quantum-chemical analysis of the hfi constants has demonstrated that 3-fluoro- and 3,5-difluoro-benzonitrile radical-anions are planar π radical,s while the radical-anions with fluorine atoms in the positions 2 and/or 4 relative to the nitrile group are characterized by non-planar deformation resulting from the interaction between the ground π and the lower excited σ states within the pseudo-Jahn-Teller effect.