A fulleropyrrolidine binitroxide: synthesis, EPR and electrochemical features

The synthesis, electrochemical characterization and EPR study of a fullerop yrrolidine monoadduct, bearing two TEMPO groups differently linked at posit ions 2 and 5 of the pyrrolidine ring, are presented. The exchange interacti on J between the two unpaired nitroxide electrons is of the same order of m agnitude of the N-14 hyperfine coupling (a(N)). EPR investigation in three different solvents showed that J decreases as the temperature increases. Ch emical or electrochemical reduction produces a stable triradical anion that , in the case of chemical reduction, was characterized via EPR spectroscopy . Further chemical reduction produces an unstable species probably correspo nding to a protonated compound. The electrochemical study highlights an int eresting effect of the fullerene moiety on the kinetics of TEMPO-centered e lectrochemical reduction, which was analyzed in the frame of Marcus theory of heterogeneous electron transfer.