Synthesis of fulleropyrrolidine dicarboxylic acid and its scavenging activity to superoxide radicals $$(O_2 ^{\bar \cdot } )$$

Abstract

Photochemical reaction of C60 with iminodiacetic ester (NH(CH2COOR)2, R=Me, Et, t-Bu) produced fulleropyrrolidine derivatives 2 in a 55%–36% yield (based on consumed C60). The reaction activity correlated with the steric hindrance of R groups. The order of the reaction rates decreased from Me to t-Bu (R=Me>Et>t-Bu). Fulleropyrrolidine derivative 2 (R=Me) were hydrolyzed with NaH and methanol in toluene, and then acidified with HCl to result in the corresponding fulleropyrrolidine dicarboxylic acid 3 in a 65% yield (relative to fulleropyrrolidine derivative 2). C60 derivatives 2 and 3 were structurally characterized by 1H NMR, 13C NMR, IR, and elementary analysis, MS. A chemiluminescence technique was applied to study the effects of their scavenging superoxide radicals \((O_2 ^{\bar \cdot } )\) generated by pyrogallol autoxidation. The results show fulleropyrrolidine dicarboxylic acid 3 had scavenging activity and the efficiencies were dependent on their concentrations. At the concentration of 3.0×10−4 mol·L−1, fulleropyrrolidine dicarboxylic acid 3 showed a radical scavenging efficiency of approximately 70%. Finally, the influence of structure factor on the scavenging activity was discussed. The results show that the monoadduct of C60, owing to keeping almost intact double bands in C60 moiety, had obvious scavenging activity for superoxide radicals \((O_2 ^{\bar \cdot } )\).