Electron magnetic resonance study of stable radicals in irradiated D-fructose single crystals

Abstract

The electron paramagnetic resonance (EPR) spectra of irradiated mono and oligosaccharides are very complex because of their multicomponent character. A multivariate statistical method called MLCFA (maximum likelihood common factor analysis) predicts at least four components contributing to the total EPR spectrum of irradiated D-fructose powder at room temperature. To elucidate the nature of the induced paramagnetic defects, we have applied magnetic resonance techniques to irradiated D-fructose single crystals. After X-irradiation the single crystals have been investigated with electron nuclear double resonance (ENDOR) and ENDOR induced EPR (EI-EPR) at 60 K. Two dominant EPR components could be isolated and interpreted in terms of three non-equivalent proton splittings. By comparing the experimental proton hyperfine tensors with the corresponding quantities calculated using density functional theory, a plausible structure for the two detected radicals will be presented.