Bond Orders and Atomic Properties of the Highly Deformed Halogenated Fullerenes C60F18 and C60Cl30 Derived from their Charge Densities

• Published in: Chemistry : a European journal 2007-01, Vol.13 (7), p.1910-1920
• Main Authors: Hübschle, Christian B., Scheins, Stephan, Weber, Manuela, Luger, Peter, Wagner, Armin, Koritsánszky, Tibor, Troyanov, Sergey I., Boltalina, Olga V., Goldt, Il'ya V.
• Format: Article
• Language: English
• Subjects: bond order; charge density; fullerenes; halogens; topological analysis
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200601616

The experimental charge densities of the halogenated C60 fullerenes C60F18 and C60Cl30 were determined from high‐resolution X‐ray data sets measured with conventional MoKα radiation at 20 K for C60Cl30 and with synchrotron radiation at 92 K for the fluorine compound. Bond topological and atomic properties were analyzed by using Bader's AIM theory. For the different CC bonds, which vary in lengths between 1.35 and 1.70 Å bond orders n between n=2 and significantly below n=1 were calculated from the bond topological properties at the bond critical points (BCP's). The low bond orders are seen for 5/6 bonds with each contributing carbon carrying a halogen atom. By integration over Bader's zero flux basins in the electron density gradient vector field atomic properties were also obtained. In contrast to free C60, in which all carbon atoms have a uniform volume of 11 Å3 and zero charge, atomic volumes vary roughly between 5 and 10 Å3 in the halogenated compounds. Almost zero atomic charges are also found in the Cl derivative but a charge separation up to ±0.8 e exists between C and F in C60F18 due to the higher fluorine electronegativity, which is also seen in the electrostatic potential for which the electronegativity difference between carbon and fluorine, and the addition to one hemisphere of the fullerene cage leads to a strong potential gradient along the C60F18 molecule. From the summation over all atomic volumes it follows that the halogen addition does not only lead to a dramatic distortion of the C60 cage but also to a significant shrinkage of its volume. Experimental charge densities of the halogenated fullerenes C60F18 and C60Cl30 were obtained from high‐resolution X‐ray data sets. Bond topological and atomic properties for the highly deformed C60 cages (for example, the “drum” shaped C60Cl30 molecule shown here) were derived.