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

Abstract

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.