A procedure for labeling of a fullerene derivative 1-[N',N'-bis(2-chloroethyl)-4-aminophenyl]-N-methyl-fullereno-C60-[1,9-c]pyrrolidine (C60-C13H18N2Cl2) with 125I is reported. The compound was first iodinated with a large excess of iodine monochloride and then radiolabeled by isotopic
exchange with Na125I in a toluene-water two-phase system. The dependence of the radiolabeling yield on the reaction temperature and exchange
time was examined. The radiolabeling yield of the compound was as high as 94% after heating for 2 hours at 130 °C.