Some Enthalpies of Solution of C₆₀ and C₇₀. Thermodynamics of the Temperature Dependence of Fullerene Solubility

Abstract

The enthalpy of solution of C60 in toluene, carbon disulfide, decalin, and N,N-diethylaniline and of C70 in CS2 has been measured using an isoperibol solution calorimeter. Exothermic heats of solution are observed in all cases. The heat of solution of C60 in toluene is −8.6 ± 0.7 kJ mol-1; in carbon disulfide it is −20 ± 1 kJ mol-1. In decalin, slow dissolution prevents an accurate determination, but the heat of solution is less than −5 kJ mol-1. In N,N-diethylaniline, a fast exothermic step comparable to that observed in other systems is followed by a much larger heat evolution, implying that a chemical reaction is occurring. The heat of solution of C70 in CS2 is −9 ± 1 kJ mol-1. A thermodynamic theory of the temperature dependence of fullerene solubility is presented. The central idea is that the unusual temperature dependence of the solubilities of fullerenes is caused by the formation of solvated crystals. Conditions are derived under which a temperature maximum of solubility, caused by an incongruent melting point of a solvated crystal, will occur. The calorimetric results suggest that the negative temperature dependence of the solubility of fullerenes may be quite general if the solid phase in equilibrium with the saturated solution is unsolvated fullerene.

Multiparameter solubility model of fullerene C60

“…Fullerene C 60 is known to have low solubility in many organic solvents [1][2][3][4][5][6][7][8][9][10][11][12][13]. Given its unusual cage-like structure a study of the solubility characteristics will yield important physical chemical information on solution thermodynamics.…”

“…The first is that some solvents form solvated crystals with fullerene. The formation of solvated crystals has led to a maximum in the temperature dependency of solubility in several solvents [9][10][11][12][13]. When solvated crystals were formed the crystals were in lower free energy states compared to solid * Tel.…”

Anomalies in the Change of Volumetric Parameters of the Diels–Alder Reaction in Solution

“…However, for large molecules, for example, balls such as fullerene C-60, packing in the crystal has a significantly greater volume of voids (V cryst = 429 cm 3 ·mol −1 ) than in solution (350-400 cm 3 ·mol −1 ) [32]. For the same reason the dissolution of solid fullerene C-60 is exothermic [33].…”

Photophysical investigations and binding strength in supramolecular interaction of a newly designed diporphyrin tweezer with fullerenes C60 and C70 in solution

“…However, in benzonitrile medium, possibility of electron transfer from porphyrin to fullerene is very much feasible due to the increased polarity of the solvent and at the same time, formation of radical ion-pair [24]. In our present investigations, we have determined the rates of charge separation (k singlet CS ) and quantum yields (/ singlet CS ) in an usual manner employed for the intermolecular energy/electron-transfer process and the data are provided in Table 2.…”