posted on 2020-05-21, 15:57authored byGábor Bortel, Éva Kováts, Dávid Földes, Emma Jakab, Gábor Durkó, Sándor Pekker
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.