Rotor-stator molecular crystals of fullerenes with cubane

Cubane(1) ( C(8)H(8)) and fullerene(2) ( C(60)) are famous cage molecules with shapes of platonic or archimedean solids. Their remarkable chemical and solid- state properties have induced great scientific interest(3 - 5). Both materials form polymorphic crystals of molecules with variable orientational ordering(6 - 9). The idea of intercalating fullerene with cubane was raised several years ago(10) but no attempts at preparation have been reported. Here we show that C(60) and similarly C(70) form high- symmetry molecular crystals with cubane owing to topological molecular recognition between the convex surface of fullerenes and the concave cubane. Static cubane occupies the octahedral voids of the face- centred- cubic structures and acts as a bearing between the rotating fullerene molecules. The smooth contact of the rotor and stator molecules decreases significantly the temperature of orientational ordering. These materials have great topochemical importance: at elevated temperatures they transform to high- stability covalent derivatives although preserving their crystalline appearance. The size- dependent molecular recognition promises selective formation of related structures with higher fullerenes and/ or substituted cubanes.