Calorimetric studies of solvates of C-60 and C-70 with aromatic solvents

To improve the understanding of the solution properties of C-60 and C-70 in aromatic solvents, binary systems of C-60 and C-70 with benzene, toluene, 1,2- and 1,3-dimethylbenzene, 1,2,4- and 1,3,5-trimethylbenzene, bromobenze ne, and 1,2- and 1,3-dichlorobenzene were studied using differential scanni ng calorimetry, solution calorimetry, and thermogravimetry. Solid solvates with different compositions were identified in many of the systems. The sol vates were characterized by composition and by the temperature and the enth alpy of the incongruent melting transition. Enthalpies of solution of C-60 in toluene, 1,2-dimethylbenzene 1,2- and 1,3-dichlorobenzene, and 1,2,4-tri methylbenzene and of C-70 in 1,2-dimethylbenzene and in 1,2- and 1,3-dichlo robenzene were determined. The formation-incongruent melting of solid solva tes causes maxima in the temperature-solubility curves of fullerenes in aro matic solvents. Trends in solubility behavior of fullerenes were discussed in terms of thermodynamics of solution and solvate formation.