An ESR study on electron-capture phosphorus-centered radicals in solid matrixes of alkyl/phenylphosphine sulfides and selenides

A low-temperature ESR study on electron-capture radicals in X-irradiated alkyl/ phenylphosphine chalcogenides is presented. In general, exposure of solid R(3-n)Phn PX derivatives (R = alkyl, Ph = phenyl, X = S, Se, n = 1, 2) to X-rays gave ESR spectra assigned to the corresponding radical anions, in which the unpaired electron is located in an antibonding P-X s* orbital. For two of the compounds studied (Me2PhPSe and MePh2PSe), however, no phosphoranyl radicals could be observed. For methylphenyl-n-propylphosphine selenide, a single-crystal ESR analysis of the s* radical anion is presented, giving detailed information on its electronic and geometric structure. It is found that the unpaired electron resides in a PSe anti-bonding s* orbital, whose direction almost parallels the parent PSe bond. Aspects of radiation damage mechanisms and phosphoranyl radical formation in phosphine chalcogenides are discussed.