Electron Spin Resonance Spectrum of the Chlorodisulfanyl (S2Cl) Radical in Inert Matrices at 4.2°K

Abstract

A new species, the chlorodisulfanyl radical (ClSS), has been produced by photolysis of dichlorodisulfane (Cl₂S₂) in inert matrices at 4.2°K. The identification of ClSS rests on the complete simulation of its well resolved electron spin resonance spectrum. A versatile computer program was developed for this purpose. The method of computation is perfectly general and takes into account the noncoincidence of the principal axes frames of the various tensors in the spin Hamiltonian which, apart from the usual g and A tensors, includes a quadrupole coupling tensor and nuclear Zeeman term. The chlorodisulfanyl radical possesses anisotropic g and hyperfine tensors which have principal axes rotated relative to each other by 10° in the molecular plane. In addition to this, the fact that the chlorodisulfanyl radical has been found to have a quadrupole coupling tensor which is of comparable magnitude to the hyperfine interaction tensor leads to a rather complicated ESR spectrum for the randomly oriented species. Our work shows that the chlorodisulfanyl radical is a ``π radical.'' The anisotropy of the hyperfine coupling tensor can be explained by spin polarization of the $\mathrm{Cl–S}\mathrm{\hspace{0.17em}\sigma }$ bond rather than by contributions from spin density on neighboring sulfur atoms.