The evolutions of the structure stability, vibrational frequency, frontier orbital, and electronegativity of the unconventional exohedral fullerenes C 64X 4 (X = H, F, Cl, Br, and I): A density functional study

Abstract

The density functional theory is employed to analyze the evolutions of the structural and electronic properties of the unconventional carbon halogen molecules C 64X 4 (X = F, Cl, Br, and I). It is found that the evolutions of the bond dissociation energies, the energy gaps, and the maximal frequencies all decrease with the increased atomic number of X, indicating that the stabilities should decrease from C 64F 4 to C 64I 4. C 64X 4 (X = F and Br) could be isolated and synthesized due to the successful isolation of C 64Cl 4 by Han et al. [X. Han, S.J. Zhou, Y.Z. Tan, X. Wu, F. Gao, Z.J. Liao, R.B. Huang, y.q. Feng, X. Lu, S.Y. Xie, L.S. Zheng, Angew. Chem. Int. Ed. 47 (2008) 5340]. It is revealed from analyzing the frontier orbitals of C 64 that the C–C bonds locate on the pentagon–pentagon fusions function as active sites in chemical reactions, facilitating hydrogen atoms or halogen atoms attachment. The electronegativity of C 64X 4 cluster molecules decrease with the increased atomic number of X, however, the electronegativity of the CX fragment in the molecules is affected by its located site. The molecule electronegativity χ and the chemical hardness η of C 64X 4 (X = F, Cl, Br, and I) decrease with the increased atomic number of X, while the electrophilicity index ω increases from C 64F 4 to C 64I 4. The C 3 v –C 64 is weak aromatic, whereas, the C 64X 4 (X = F, Cl, Br, I) show nonaromatic character.