HIGH-YIELD SYNTHESIS, SEPARATION, AND MASS-SPECTROMETRIC CHARACTERIZATION OF FULLERENES C60 TO C266

The preparation of fullerenes C60 to C266 in very high yield (up to 44% extractable) by a plasma discharge is reported. Almost one-third of the extractable material is composed of giant fullerenes C84 to C200. An extraction scheme for isolating selected molecular weight fractions of fullerenes is described. The extractions were characterized by time-of-flight mass spectrometry and Fourier transform mass spectrometry. We find that a Soxhlet extraction with benzene extracts 50% more soluble fullerenes than benzene reflux. Soxhlet extractions with 1,2,3,5-tetramethylbenzene preferentially extract higher molecular weight fullerenes. Hexane appears to limit the amount of higher fullerenes extracted, giving solutions containing C60 and C70 with only small traces of the higher molecular weight fullerenes. Heptane extraction following the hexane extraction appears to preferentially extract C60, C70, and C84. This solvent scheme is useful in preparing selected molecular weight fractions for subsequent separation by column chromatography.