EXTRACTION OF GIANT FULLERENE MOLECULES, AND THEIR SUBSEQUENT SOLVATION IN LOW BOILING-POINT SOLVENTS

Carbon soot produced by the graphite arc-synthesis method was solvated to varying extents in four different solvents, after previous removal of some fullerenes, particularly C60 and C70, by toluene extraction. The solvents and weight percentages of soot solvated (in parentheses) are: xylenes (3.5), 1,3,5-trimethylbenzene (7.4), 1,2,4-trichlorobenzene (31.1), and 1-methylnaphthalene (22.5). If one accounts for the C2n fullerene molecules, primarily C60 and C70 extracted from virgin soot by toluene, roughly 37% of the virgin carbon soot can be solvated by the use of 1,2,4-trichlorobenzene. A rough value for the enthalpy of solvation difference is determined for C70 and C60, by van't Hoff analysis, to be DELTA-DELTA-H = 5 kcal/mol. This method is suggested as a valuable indicator for the difference of enthalpies of binding of C2n molecules to the soot matrix. After filtration and removal of the solvents used in the extractions, the residues can be redissolved in low-boiling-point solvents such as methylene chloride and toluene, two solvents which dissolved essentially none of the (previously) toluene-extracted starting material. This underscores the importance of the soot matrix in inhibiting solvation of C2n fullerene molecules, and suggests that chromatographic separation of large fullerene molecules can be done with low-boiling-point solvents, and may therefore be feasible.