Electron paramagnetic resonance and theoretical study of dibenzylmercury and diphenylmercury radical cations

Abstract

Radical cations of dibenzylmercury and its p-X derivatives (X = Me, MeS, MeO, Cl) and of diphenylmercury and its p-X derivatives (X = Cl, Et, Me, MeO) have been generated by γ-radiolysis of dilute solutions of the parent compounds in CFCl3 matrices at 77 K. The EPR results for the dibenzylmercury series show all members to be σu-radical cations with singly occupied molecular orbitals approximating to the form (I). The parallel and perpendicular |+½> components of the 199Hg spectrum are almost coincident, giving an intense low-field isotropic line: this shows a substructure typical of an anisotropic doublet coupling, and arises from a single solvent fluorine atom, but is unprecedentedly large for radical-cation superhyperfine couplings in freon matrices. These additional couplings were absent when the experiments were repeated using a CCl4 matrix which confirms the 19F assignment.