Solid-state studies on a C-60 solvate grown from 1,1,2-trichloroethane

Single and 10-fold-twinned crystals of the C-60 1:1 solvate formed with 1,1 ,2-trichloroethane were examined by means of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry and thermogravimet ry. Solubility of C60 in 1,1,2-trichloroethane was found to be 130 +/- 10 m g per liter of solution in equilibrium with solvate crystals at 296 +/- 2 K . The lattice metrics of the solvate is orthorhombic (a 10.164(3) Angstrom, b = 31.390(6) Angstrom, c = 10.130(4) Angstrom, beta = 90.00(2)degrees), w ith axis c as a twin axis, although the symmetry is monoclinic (space group P2(1)/n). The solvate forms with a negative excess volume (-58 Angstrom (3 ) per formula unit), and its packing coefficient (0.76) is higher than that for close packing of hard spheres. On heating, desolvation into cubic C-60 and TCAN vapor occurs in one step at 436 K (onset) with a related enthalpy , +48 kJ per mole of solvate, close to the sublimation enthalpy for pure so lvent. On aging at room temperature in the dark, no degradation of big (app roximate to1 x 10(-3) mm(3)) solvate crystals into fee C-60 is observed aft er 4 years have elapsed.