Electron Spin Resonance Spectrum of the Radical Anion of 1,3,5-Cycloheptatriene and the Spin Polarization Constant QC′CHH

Abstract

The radical anion of 1,3,5‐cycloheptatriene has been prepared by electrolysis in liquid ammonia. The proton hyperfine structure of its electron spin resonance spectrum was assigned with A(1, 6)=7.64, A(2, 5)=0.59, A(3,4)=4.90, and A(7)=2.16 G. Satisfactory agreement between calculated and observed coupling constants is only obtained if the radical anion is assumed to have a nonplanar boat conformation and if the methylene coupling is assumed to arise primarily from spin polarization by the spin density on adjacent carbon atoms. A value for this spin‐polarization constant is obtained and we find that either Q_C′CH^H=4.33 or −3.09 G. The recent data of Morton are in good agreement with the positive value, but the theoretical calculation by Colpa and de Boer indicate that it should be probably negative in sign.