New EPR signals of endohedral metallofullerenes

The EPR spectra of endohedral metallofullerenes (EMF), La-EMF and Y-EMF, wh ich were free of admixtures of C-60 and of other empty fullerenes, were exa mined. Endohedral metallofullerenes were prepared by extraction of fulleren e-containing soots with DMF. New signals with g factors close to those of f ullerene radical anions were observed in the EPR spectra of solutions of EM F in DMF and DMSO. At similar to 20 degreesC, these signals are observed as a doublet (DeltaH(pp) approximate to 0.04 mT) and singlet (DeltaH(pp) appr oximate to 0.01 mT) in solutions of La-EMF and Y-EMF, respectively. These E PR signals belong to solvated La@C-82 and Y@C-82 molecules and are characte rized by small hyperfine interaction constants a(M) due to a substantial de crease in the spin density of the unpaired electron at the metal atom.