Solid solvates of C-60, C-70 and C-60-C-70, with aromatic solvents

Differential scanning calorimetry (DSC) was used to study the binary systems C-60-o-xylene, C-70-o-xylene and the ternary system C-60-C-70-o-xylene. Fullerene C-60 formed the solvated crystal C-60*2C(8)H(10) with incongruent melting point T=320K and with enthalpy of decomposition 31 +/- 3 kJ/mol of C-60. Two solvated crystals of C-70 were formed from the o-xylene solution with the incongruent melting points 283 and 369K respectively, and with the decomposition enthalpies 21 and 26 +/- 3 kJ/mol of C-70 respectively. It was found that the second crystal was composed of a C-70*2C(8)H(10) formula unit while the first one incorporated at least one more molecule of o-xylene. Three ternary compositions with the mole ratio of C-60/C-70 = 3:1, 1:1, 1:3 respectively were scanned with DSC. The present study strongly suggested that a new ternary solid phase with decomposition temperature 333 +/- 2K was formed. A simple ternary phase diagram was proposed to account for the DSC data.