The EPR spectra of FC60 and FC70

The EPR spectra of FC60 and four isomers of FC70 are described and discussed. As with HC70, the four isomers of FC70 that are observed are those with fluorine atoms attached to A-, B-, C- or D-type carbon atoms of the C70 molecule. The temperature dependence (1/a) dea/dT of the 19F hyperfine interaction in FC60 and the most abundant isomer of FC70 is approximately twice that observed for the proton hyperfine interaction in HC60 and HC70, and the muon hyperfine interaction in MuC60. The similarity of the temperature dependences in C60 and C70 derivatives indicates that the vibrations responsible for the temperature effect are of the same nature for the two radicals. The magnitude of the temperature-dependence coefficients of the fluoro-derivatives is consistent with a smaller spin density in F(2s) compared to that in the H(1s) orbital of HC60 and HC70.