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Denitsa Shopova, Martin Panthöfer, Václav Petricek, Martin Jansen

Refinement strategies for fullerene structures: use of local, non-crystallographical point group symmetry

Keywords: Fullerenes, Co-crystals, Refinement strategies, Single crystal structure analysis, X-ray diffraction

The crystal structure of C₇₀·Se₈·CS₂ was determined from single crystal X-ray diffraction data at 100 K. Due to some peculiarities of the space group Pca2₁ and the presence of local centres of symmetry, the crystal structure refinement turned out to be problematic. Instead of stabilizing the refinement procedure by means of a very high number of restraints about direct neighbour distances and -angles, and the shape of the probability density function of the carbon atoms of the fullerene molecules, the molecular structure of the C₇₀ molecules was treated as a rigid body applying a local symmetry restraint in a local coordinate framework, and the TLS-formalism, using the JANA2000 program.
The crystal structure may be derived from the NiAs structure type, with the fullerene molecules forming a highly distorted hexagonal closed packing. In order to enable lone-pair-p-interactions between the fullerene and the chalcogene molecules, the Se₈-rings are shifted from the centres of the octahedral voids towards the triangular faces.

Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0044-2968
Volume: 222, 10/2007
Pages: 546 - 550

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