Proton, muon and 13C hyperfine coupling constants of C60X and C70X (X = H, Mu)

The reaction of H atoms with fullerene C70 has been investigated by identifying the radical products formed by addition of the atom muonium (Mu) to the fullerene in solution. Four of the five possible radical isomers of C70Mu were detected by avoided level-crossing resonance (μLCR) spectroscopy, using a dilute solution of enriched 13C70 in decalin. DFT calculations were used to predict muon and 13C isotropic hyperfine constants as an aid to assigning the observed μLCR signals. Computational methods were benchmarked against previously published experimental data for 13C60Mu in solution. Analysis of the μLCR spectrum resulted in the first experimental determination of 13C hyperfine constants in either C70Mu or C70H. The large number of values confirms predictions that the four radical isomers have extended distributions of unpaired electron spin.