Calorimetric Studies of Solvates of C₆₀ and C₇₀ with Aromatic Solvents

Abstract

To improve the understanding of the solution properties of C60 and C70 in aromatic solvents, binary systems of C60 and C70 with benzene, toluene, 1,2- and 1,3-dimethylbenzene, 1,2,4- and 1,3,5-trimethylbenzene, bromobenzene, and 1,2- and 1,3-dichlorobenzene were studied using differential scanning calorimetry, solution calorimetry, and thermogravimetry. Solid solvates with different compositions were identified in many of the systems. The solvates were characterized by composition and by the temperature and the enthalpy of the incongruent melting transition. Enthalpies of solution of C60 in toluene, 1,2-dimethylbenzene, 1,2- and 1,3-dichlorobenzene, and 1,2,4-trimethylbenzene and of C70 in 1,2-dimethylbenzene and in 1,2- and 1,3-dichlorobenzene were determined. The formation−incongruent melting of solid solvates causes maxima in the temperature−solubility curves of fullerenes in aromatic solvents. Trends in solubility behavior of fullerenes were discussed in terms of thermodynamics of solution and solvate formation.