Structure, stability, and thermochemistry of the fullerene derivatives C(64)X(6) (X = H, F, Cl)

The geometrical structures, electronic properties, and stabilities of the unconventional fullerene derivatives C(64)X(6) (X = H, F, Cl) have been systematically studied by the first-principle calculations based on the density functional theory. The fullerene derivatives 1911(2)-C(64)X(6) generated from the pineapple-shaped C(64)X(4) are predicted to possess the lowest energies. The other two X atoms are added to the carbon atoms with the highest local strain assessed by the pyramidalization angles. The calculations of the nucleus-independent chemical shifts suggest that the aromaticity of C(64)X(6) affects the stability order of the derivative isomers. To address why C(64)H(6) was not observed in the experimental study of Wang et al. (J. Am. Chem. Soc. 2006, 128, 6605) and if the halogenated derivatives C(64)X(6) (X = F, Cl) can be synthesized, thermochemical analysis of the reaction C(64)X(4) + X(2) --> C(64)X(6) was also performed. The results indicate that the formation of C(64)H(6) and C(64)Cl(6) is not favored at high temperatures. The former may be a reason why C(64)H(6) was not found in the experiment. In sharp contrast, the Gibbs free energy change to form C(64)F(6) is found to be -23.29 kcal/mol at 2000 K, suggesting that this compound may be formed and detected in experiments. The NMR and IR spectra of 1911(2)-C(64)F(6) are sequentially calculated and presented to facilitate future experimental identification.