Structures, Stabilities, and Electronic and Optical Properties of C₅₈Fullerene Isomers, Ions, and Metallofullerenes

Abstract

The 1205 classical isomers of fullerene C58, as well as one quasi-fullerene C58 isomer with a heptagonal ring (labeled as Cs:hept) have been investigated by the quantum chemical methods PM3, HCTH/3-21G, and B3LYP/6-31G(d). Isomer C3v:0001, which has the lowest number of adjacent pentagons, is predicted to be the most stable isomer, but the quasi-fullerene isomer Cs:hept is only 2.50 kcal mol-1 higher in energy. Systematic investigations of the electronic properties of C3v:0001 and Cs:hept find that the C3v:0001 isomer has high vertical electron affinity (3.19 eV). The nucleus-independent chemical shifts (NICS) value at the center of Cs:hept (-5.1 ppm) is more negative than that of C60 (-2.8 ppm). The NICS value at the center of the heptagonal ring in Cs:hept (-2.5 ppm) indicates weakly aromatic character. In contrast, the C58(6-) and C58(8-) ions of the C3v:0001 and Cs:hept geometries possess large aromatic character, with NICS values between -14.0 and -26.2 ppm. To clarify the thermodynamic stabilities of C58 isomers at different temperatures, the entropy contributions are taken into account on the basis of the Gibbs energy at the B3LYP/6-31G(d) level. The C3v:0001 isomer prevails in a wide range of temperatures, and the Cs:hept isomer is also an important component around 2800 K. The IR spectra of C58 isomers are simulated to facilitate experimental identification of different isomers. In addition, the electronic spectra and the second-order hyperpolarizabilities are predicted by ZINDO and the sum-over-states model. The static second-order hyperpolarizability of the C3v:0001 isomer is 96.5 % larger than that of C60, and its second-order hyperpolarizabilities at external field frequencies are at least nine times larger than those of C60.

Carbon arc production of heptagon-containing fullerene[68]

“…At a temperature above 2,100 K, however, the heptagon-incorporating C 68 becomes the most abundant species as entropic factors have a decisive role in their relative Gibbs free energies and relative concentrations/abundances (Supplementary Tables S8 and S9). In agreement with this prediction about the temperature-dependent stability, several theoretical studies have suggested the prevalence of heptagons in the world of the cage-closed all-carbon allotropes1112131415161718192021232425263536. Experimental corroboration of such a prevalence of heptagons heavily depends on the in situ capture of heptafullerene in the carbon clustering venue for the growth of the whole family of fullerenes.…”

“…Experimentally, however, heptagon rings are also incorporated into carbon frameworks making the experimentally available carbon allotropes (for example, fullerenes and carbon nanotubes, as well as graphenes) defective species345678910. Although unambiguous identification of heptagons in the family of all-carbon allotropes remains an open question, numerous theoretic studies have focused on the heptagon-involved defect because of its key responsibility for changing geometric structures and properties of the experimentally available carbon allotropes111213141516171819.…”

“…A bare heptafullerene[62] with C s -symmetry23, as well as the exohedral heptagon-containing C 68 X 4 (X=H, F, Cl)24, has been calculated to be more stable than all the classical non-heptagon isomers. Very recently, a number of smaller heptafullerenes (C 46 –C 58 ) have also been suggested to be viable182526. However, experimental confirmation of the existence of heptagons in the family of fullerenes is still a challenge for chemists and physicists.…”

Imitating trumpet shells: Möbius container molecules

“…To provide more helpful hints to the experimental identification of these designed Möbius molecules, the calculated vibrational spectra for the three designed structures and the corresponding cage C 58 [14] at the B3LYP/6-31G(d) level are shown in Figure 4. There are two apparent differences between these Möbius molecules and the cage C 58 molecule.…”

“…For geometry optimization, Becke-3-three-parameter density functional theory (DFT) and Lee-Yang-Parr correlation functional (B3LYP) level with the 6-31G(d) basis set have been used for the neutral C 58 cages [14] and C 54 cages [15]. Three theoretically designed Möbius molecules in the singlet state, C 64 H 8 , C 60 N 4 H 4 , and C 58 N 6 H 2 with all real frequencies, were obtained at the B3LYP/6-31G(d) level (with STABLE keyword).…”