Novel Organic Ions of High-Spin States VI.: ESR Study on a Monocation of a Prototyoical High-Spin Molecular with a Weak Intramolecular Exchange Interaction, Biphenyl-3,3′-Diylbis (Phenylmethylene)

Abstract

A monocation of biphenyl-3,3′-diylbis(phenylmethylene) (BP-3,3′-BPM) was produced by γ-irradiation of biphenyl-3,3′-diylbis(phenyldiazomethane) (BP-3,3′-BPD) followed by denitrogenation by a visible light photolysis. ESR spectra at 77 K indicated the formation of a spin-quartet cation. However, the ground state of the cation was determined to be spin-doublet from the temperature dependence of the intensity of the quartet ESR signal. The doublet-quartet energy gap of the cation was estimated to be about 24 cm⁻¹. The electronic state and the molecular structure of the cation were discussed by referring to a semiempirical calculation and by comparing with those of the anion.