Chemical crystallography of fullerenes

The state-of-the-art in the structural investigations into fullerene derivatives is surveyed. The crystal structures of individual fullerenes and of their derivatives determined experimentally by single-crystal X-ray diffraction are systematised. The results of powder X-ray diffraction and EXAFS spectroscopy are overviewed for those classes of derivatives that have been insufficiently studied by single-crystal X-ray diffraction. Patterns of packing of the fullerene spheres encountered in crystal structures are described and representative examples of the most typical motifs are given. Reasons for the rotational disorder, which often hampers structure determination for fullerene derivatives, and its classification are considered. A model of the "rubber cavity" is introduced, which allows prediction of typical mutual orientations of disordered molecules. The redistribution of bond lengths upon σ- and π-functionalisation of the carbon core is analysed based on the information retrieved from the Cambridge Structural Database. Factors affecting the molecular packing density in crystalline derivatives of fullerenes are discussed in relation to the quality of the diffraction data attainable for them.