New EPR signals of endohedral metallofullerenes

Article abstract of DOI:10.1007/BF02496346

The EPR spectra of endohedral metallofullerenes (EMF), La-EMF and Y-EMF, which were free of admixtures of C₆₀ and of other empty fullerenes, were examined. Endohedral metallofullerenes were prepared by extraction of fullerene-containing soots with DMF. New signals with g factors close to those of fullerene radical anions were observed in the EPR spectra of solutions of EMF in DMF and DMSO. At ～20 °C, these signals are observed as a doublet (ΔH_pp ≈ 0.04 mT) and singlet (ΔH_pp ≈ 0.01 mT) in solutions of La-EMF and Y-EMF, respectively. These EPR signals belong to solvated La@C₈₂ and Y@C₈₂ molecules and are characterized by small hyperfine interaction constants a_M due to a substantial decrease in the spin density of the unpaired electron at the metal atom.