Electron magnetic resonance and density functional theory study of room temperature X-irradiated β-D-fructose single crystals

Stable free radical formation in fructose single crystals X-irradiated at room temperature was investigated using Q-band electron paramagnetic resonance (EPR) electron nuclear double resonance (ENDOR) and ENDOR Induced EPR (EIE) techniques ENDOR angular variations in the three main crystallographic planes allowed an unambiguous determination of 12 proton HFC tensors From the EIE studies these hyperfine interactions were assigned to six different radical species labeled F1-F6 Two of the radicals (F1 and F2) were studied previously by Vanhaelewyn et al [Vanhaelewyn G C A M Pauwels E Callens F J Waroquier, M Sagstuen E Matthys, P J Phys Chem A 2006 110, 2147] and Tarpan et al [Tarpan M A Vrielinick H De Cooman H Callens F J J Phys Chem A 2009 113 7994] The other four radicals arc reported here for the first time and periodic density functional theory (DFT) calculations were used to aid their structural identification For the radical F3 a C3 carbon centered radical with a carbonyl group at the C4 position is proposed The close similarity in HFC tensors suggests that 14 and F5 originite from the same type of radical stabilized in two slightly different conformations For these radicals a C2 carbon centered radical model with a carbonyl group situated at the C3 position is proposed A rather exotic C2 centered radical model is proposed for F