Structural study of C₆₀ and C₇₀ cubane

Abstract

Abstract Fullerenes and cubane (C 8 H 8 ) form new high‐symmetry heteromolecular crystals and C 60 –cubane and C 70 –cubane are the first members of this family. We present the results of a detailed structural study in a wide temperature range, from 100 K to 470 K. The structure of these compounds is based on the well‐known face centered cubic (fcc) C 60 lattice. In the highest symmetry case freely rotating fullerenes occupy the fcc lattice sites, and cubanes fill the octahedral voids. We found various phase transitions on lowering the temperature. As expected, the free rotation of fullerenes becomes hindered and orientational ordering appears. The orientational transition temperature is exceptionally low, which can be explained by the combination of the high symmetry environment of fullerenes, the perfect match of convex fullerene and concave cubane molecular surfaces and the significantly expanded fullerene lattice. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)