Novel Organic Ions of High-Spin States

Abstract

Abstract The interrelation between spin alignment and a charged organic molecular field has been investigated. The monoanion (monocation) of m-phenylenbis(phenylmethylene), a ground-state quintet alternant hydrocarbon, was formed at 77 K via the photolysis of the ionized diazo precursor generated via gamma-radiolysis in the frozen solution of 2-methyltetrahydrofu-ran (butyl chloride). Both the ions exhibited similar ESR spectra identified as due to a ground-state quartet with g = 2.003 (2.003), D = +0.1200 (+0.1350, +0.1285) cm−1 and |E|= 0.0045 (0.0040, 0.0055) cm−1 for the anion (cation). The quartet state is consistent with the monoions of the parent quintet molecule with the four singly-occupied orbitals, i.e., the two pi nonbonding molecular orbitals (NBMO) and the two in-plane nonbonding orbitals at the divalent carbon atoms. It was concluded by proton-ENDOR that both the excess electron and the hole occupy one of the two singly occupied pi NBMO, the spins in the in-plane nonbonding orbitals being l...