ESR single-crystal study of the succinimidyl .pi.-electron radical in x-irradiated succinimide at 26 K

The succinimidyl radical has been identified by ESR spectroscopy in single crystals of x-irradiated succinimide at 26/sup 0/K. The principal values of the hyperfine coupling tensor and the g tensor are 31, 0, and 0 G and 2.0019, 2.0143, and 2.0057, respectively. From these values and the directions of the corresponding principal axes as well as from quantum-mechanical ab initio calculations, it is concluded that the succinimidyl radical has a ..pi..-electron structure. Three additional radicals have been identified in succinimide, one molecular anion and two alkyl radicals. 3 figures, 2 tables.