Solid state studies of the C-60. 2(CH3)CCl3 solvate

At room temperature, the hexagonal C-60. 2(CH3)CCl3 solvate (a = 10.13(1) Angstrom, c = 10.84(1) Angstrom), made of alternating layers of C-60 and solvent molecules, forms with a negative excess volume, and its desolvation enthalpy is virtually the same as the sublimation enthalpy of the pure solvent. Crystallographic and calorimetric studies vs temperature indicate that hexagonal C-60. 2(CH3)CCl3 changes at 211.7 K (1.3 kJ mol(-1) of solvate) into an intermediate triclinic phase which transforms at 189.7 K (4.1 kJ mol(-1) of solvate) into another triclinic phase. A crystallographic analysis in the series of hexagonal C-60. 2 YCCl3 solvates (Y = H, Cl, Br, CH3) reveals that: (i) the change in the unit-cell volume values is due to a change in axis c whose value depends on the size of Y, (ii) the molar volume of the solvates depends linearly on the molar volume of the solvents. Ageing studies at room temperature show that C-60. 2(CH3)CCl3 loses its solvent molecules within a few days or a few months, depending on storage conditions. (C) 2004 Elsevier Ltd. All rights reserved.