The addition of several photochemically generated aryl and fluoroalkyl radicals to fullerene C 70 was studied by electron spin resonance and the results were compared with those obtained with C 60 . While simple alkyl radicals afford only three of the five expected RC 70 • regioisomers, the more reactive aryl and fluoroalkyl radicals give rise to four, except for the trifluoromethyl radical which yielded for the first time the ESR spectra of all five expected isomers. Semiempirical MO calculations and density functional theory calculations were carried out for HC 60 • and for the five HC 70 • regioisomers as models for the corresponding alkyl, aryl, and fluoroalkyl analogs in order to describe the unpaired electron distribution in these radical species and as an aid in the assignment of the observed spectra to specific RC 70 • regioisomers.

Photolysis of dialkoxy disulfides ROSSOR (R = Me, Et, i-Pr, t-Bu, i-PrCH2, t-BuCH2) yields the radicals RO•, ROS•, and ROS•O that were identified on the basis of product analysis and spin trapping techniques. It has been shown that only the alkoxy radicals RO•, produced from ROSSOR, add to the sphere of fullerene C60 in steady state conditions to yield the RO−C60 • adducts which can be detected by ESR spectroscopy. The different trend of the hydrogen splitting constants in the RO−C60 • with respect to the corresponding RS−C60 • adducts previously reported has been interpreted as a consequence of the different C−O and C−S bond lengths.

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