Indirect 1H NMR characterization of H2@C60 nitroxide derivatives and their nuclear spin relaxation

H-1 NMR of two H-2@C-60 nitroxide derivatives has been characterized indirectly by reducing to their corresponding hydroxylamines. Nuclear spin relaxation of the endohedral H-2 and external protons of the H-2@C-60 nitroxide and its corresponding hydroxylamine were measured and analyzed. The observed spectra are consistent with negligible scalar coupling between the unpaired electron and the endo-H-2. An unexpectedly large bimolecular relaxivity induced in the hydroxylamine by the corresponding nitroxide can be explained by rapid hydrogen atom transfer between the two species.