Recognition-Control and Host-Guest Interactions in High-Symmetry Cocrystals of Fullerenes with Cubane and Mesitylene

The limited success in the prediction of structure is one of the most serious problems in the engineering of molecular crystals. Here we show that the packing of high-symmetry molecules such as ball-shaped rotating fullerenes, cube-shaped cubane and octahedral-shaped mesitylene dimers give rise to the formation of cubic cocrystals with easily predictable lattice parameters. We present the synthesis and structure determination of Sc3N@C80-Ih cocrystals with cubane (C8H8) and mesitylene (C9H12) and compare the new materials with related C60 and C70 based structures. In this family of materials, most atom-to-atom interactions are averaged out by the symmetry and the crystal structures can be described in terms of classical molecule-to-molecule interactions. Size-dependent homo- and heteromolecular contacts control the stability of the ball-cube and ball-octahedron systems creating several host-guest and recognition-controlled regions. The analysis of the global phase diagrams explains not only the stability of the observed materials, but also the instability of a missing derivative.