title: ENDOR and HYSCORE analysis and DFT-assisted identification of the third major stable radical in sucrose single crystals X-irradiated at room temperature.
abstract: Recently, the chemical structure of two of the three major stable radicals (T2 and T3) produced in sucrose single crystals by X-irradiation at room temperature was identified by comparing Density Functional Theory (DFT) calculations of Electron Magnetic Resonance parameters with experimental results [H. De Cooman, E. Pauwels, H. Vrielinck, E. Sagstuen, F. Callens and M. Waroquier, J. Phys. Chem. B, 2008, 112, 7298-7307]. Ambiguities concerning an unusual proton hyperfine coupling (HFC) tensor prevented the identification of the third major stable radical (T1). In the present work, experimental results of continuous wave Electron Nuclear Double Resonance experiments on sucrose single crystals and Hyperfine Sublevel Correlation Spectroscopy experiments on sucrose powder are presented that lift these remaining ambiguities. Using the final set of experimental HFC tensors and employing advanced DFT calculations, the chemical structure of the T1 radical is established: an allylic-type radical with approximately half of the spin density localised on the C2' carbon of the fructose unit, involving glycosidic bond cleavage at the fructose side and a concerted formation of a carbonyl group at the C1' carbon. The electronic structure of the T1 radical is discussed in more detail by means of additional DFT calculations, yielding a better understanding of the peculiar properties of the unusual proton HFC tensor mentioned above.
authors: Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Gent, Belgium.
authors: Hendrik
authors: H
authors: De Cooman
authors: Ewald
authors: E
authors: Pauwels
authors: Henk
authors: H
authors: Vrielinck
authors: Einar
authors: E
authors: Sagstuen
authors: Sabine
authors: S
authors: Van Doorslaer
authors: Freddy
authors: F
authors: Callens
authors: Michel
authors: M
authors: Waroquier
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D006027:Glycosides / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons; D011789:Quantum Theory; D013395:Sucrose / Q000737:chemistry*; D013696:Temperature
chemical_list: D006027:Glycosides; D011522:Protons; D013395:Sucrose