A Study of the Aromaticity of the Heterofullerene C_24–2nB_nN_n(n= 3 or 6) and C₁₂N₁₂Isomers

Abstract

The global aromaticity of the heterofullerene C 24-2n B n N n (n D 3 or 6) and C 12 N 12 isomers formed from the initial C 24 fullerene with D 6 symmetry, has been investigated using both the topological resonance energy (TRE) and the percentage topological resonance energy (%TRE) methods. The local aromaticity was studied using the bond resonance energy (BRE) method. Analysis was made of the effects of the types, the numbers, and the arrangements of heteroatoms on the global and local aromaticity of the molecules under consideration. Our results obtained by the TRE and %TRE methods were compared with the nucleus independent chemical shift (NICS (0)) values at the cage center. We found that NICS(0) values were not suitable for estimating the global aromaticity of these compounds. It was expected that the inclusion of heteroatoms would decrease the antiaromaticity relative to the C 24 (D 6 ) cage. Our BRE results show that the antiaromaticity is primarily related to the existence of highly reactive antiaromatic bonds in the molecule. We found that when a local structure within the cage had two nitrogen and one boron atom in the same pentagon ring, it played an important role in the global aromaticity of these compounds. Finally, we predicted the kinetic stability using the minimum BRE method.

Systematic Construction and Calculation of Electronic Properties of Fullerene Series Related by Rotational Symmetry: From Fullerenes to Bicapped Nanotubes

“…Studies of fullerenes that include C 20 and C 30 of Figure have been performed. , Their MNDO enthalpy of formation were computed to be Δ H f ° = 825 and 945 kcal/mol for C 20 and C 30 , respectively. The endohedral NICS value for C 20 suggests that it is aromatic, and the positive value for C 24 , that it is antiaromatic. , However, in more recent studies C 24 fullerene gave a positive NICS value at the cage center at one level of ab initio theory and a negative one at another . We note that unlike NICS(0) and NICS(1) values, which fix the distances to 0 and 1 Å above the ring currents, endohedral NICS values at the cage center involve variable radial distances and do allow direct comparisons among different size fullerenes.…”

Combination High Energy with Stability: Polynitrogen Explosives N14 and N18

“…Thereby olefin and benzene ring are expected to form a large π bond with nitrogen atoms to improve its stability thought the large conjugated bonds do not appear at last. A structure C12N12 being similar to N18 was reported, Mondal [24] indicates that are slightly aromatic in nature, but Tursungul [25] doesn`t agree with him.…”

On the 13C‐NMR chemical shift anisotropy patterns and aromatic character in strained fullerenes: Computational analysis of D6h/D2d‐C36 fullerene

“…C 36 is the first stable hollow fullerene composed of a small number of carbon atoms to be characterized, produced by Zettl and co‐workers, [ 15,16 ] which exhibits an enhanced curved π‐system, allowing us to study the characteristics of strained fullerenes as given by low‐nuclear cages. [ 17–25 ] Recently, C 36 has served to evaluate the spin gap in supramolecular complexes [ 26 ] and the role of symmetry breaking in a single‐determinant representation of the electronic structure quantifying the role of electronic correlation [ 27 ] by the Lee group. In addition, Song and coworkers extended the studies of C 36 to the characterization of several isomers by simulating their X‐ray photoelectron spectroscopy and near‐edge X‐ray absorption fine‐structure spectra, through density functional theory, [ 28 ] as a relevant approach toward the estimation of expected patterns for the characterization of molecular structures of smaller and medium‐sized fullerenes.…”