Solid-state studies of C 60 solvates formed with chlorodibromomethane

Abstract

At room temperature, the unstable-in-air hexagonal C 60·2HCClBr 2 solvate ( a = 10.154(3) Å, c = 10.150(3) Å at 308 K) forms with a negative excess volume, and slowly transforms upon ageing at room temperature into a stable orthorhombic solvate, C 60·1.5HCClBr 2 ( a = 23.009(5) Å, b = 12.649(6) Å, c = 11.659(5) Å). The lattice expansion and the lattice anisotropy of the C 60·2YCCl 3 (Y = H, CH 3, Br, Cl) and C 60·2HCBr 3 solvates, for which the solvent molecular symmetry is C 3V are compared to the new results obtained for C 60 solvates formed with HCClBr 2 (solvent molecular symmetry C 2V). Results indicate that the van der Waals volume of the solvent molecule fully controls both the unit-cell volumes of the C 60 intercalated halogenomethane solvates and the lattice expansion along the (0 0 1) hexagonal direction, the solvent molecular symmetry being an irrelevant physical parameter in the temperature range studied.