Deuterium isotope effect on the e.s.r. Spectrum of annulene radicals: a reappraisal

Abstract

The deuterium isotope effect on the e.s.r. spectrum of the cyclopentadienyl radical is suggested to be the result of deuterium perturbation of the equilibrium between the positional isomers of the Jahn–Teller distorted radical and not of vibrational perturbation of the Hückel resonance integral, β.