Solid-state studies on single and decagonal crystals of ${\mathrm{C}}_{60}$ grown from 1,2-dichloroethane

By slowly evaporating solutions of fullerene ${\mathrm{C}}_{60}$ in 1,2-dichloroethane at room temperature, crystals of an orthorhombic 1:1 solvate are obtained [$Cmcm,$ ${\mathrm{Cmc}2\mathrm{}}_1,$ or $\mathrm{Ama}2,$ with $a=10.065\mathrm{}\left(9\right)\mathrm{}\AA ,$ $b=31.34\mathrm{}\left(3\right)\mathrm{}\AA ,$ and $c=10.059\mathrm{}\left(8\right)\mathrm{}\AA$ ($C$ setting)]. Unusual decagonal needles with dihedral angles of $\sim 36°$ between adjacent faces also form. They are described in terms of a $10\times$ twinning of these orthorhombic crystals with needle axis (or twin axis [001]) parallel to composition planes in the form $\{1K0\}$ whose orientations do not correspond to rational index $k\hspace{0.5em}\mathrm{}(9<K<\mathrm{}10\mathrm{}).$ This solvate decomposes with a desolvation enthalpy (45 kJ per mole of solvent) close to that of sublimation for pure solvent and it forms with a negative excess volume ($-23{\AA }^3$ per formula unit). Despite a packing coefficient (0.77) higher than that for hard sphere close packing (0.74), it spontaneously decomposes at room temperature. This is related to the solvent adsorption on cubic ${\mathrm{C}}_{60}$ which is shown to be preferred to the solvate formation by about $-10\mathrm{kJ}$ per mole of solvent.