Synthesis and EPR investigation of nitroxyl derivatives of fullerenes C60 and C70

Nitroxide derivatives of C-60 and C-70 were obtained by [3+2] cycloaddition of 4-(4-azidophenyl)-2,2,5,5-tetramethyl-3-oxy-2,5-dihydroimidazol-l-oxyl to fullerenes. The products were isolated by TLC and studied by EPR and optical spectroscopy. Molecular rotation of the adducts was shown to slow down on successive addition of the nitroxides, rotational correlation times depending nearly linearly on the number of the nitroxides added. Investigation of photochemical stability of nitroxide derivatives of C-60 and C-70 in benzene-ethanol medium reveal that the dissolved oxygen quenches efficiently the excitation of nitroxide (lambda = 250-400 nm). In the absence of oxygen photoexcitation converts nitroxides to diamagnetic products, presumably, hydroxylamines formed through the interaction with the solvent.