A systematic investigation on the aromaticity and kinetic stability of fullerene C40 isomers: A SYSTEMATIC INVESTIGATION ON THE AROMATICITY AND KINETIC STABILITY OF FULLERENE C40 ISOMERS

Open-shell nature of non-IPR fullerene С40: isomers 29 (C2) and 40 (Td)

It is well-known that the small non-IPR fullerenes C_n (n < 60) are highly unstable and that is why they cannot be obtained as empty cages. However, they become stable as exohedral or endohedral derivatives. In this report, the molecular structures of non-IPR isomers 29 (C₂) and 40 (T_d) of fullerene C₄₀ are investigated using a semiempirical approach developed earlier for higher fullerenes. Quantum-chemical calculations (DFT) show that isomers 29 (C₂) and 40 (T_d) have open-shell structures. The distributions of single, double, and delocalized π-bonds in the isomer molecules in question are presented for the first time as well as their molecular formulas. It is found unusual for higher fullerenes chain of π-bonds passing through some cycles. Identified features in the structures of small fullerene molecules can be predictive of the ability to their synthesis as derivatives and will assist in their structure determination.

Identification of Four C40 Isomers by Means of a Theoretical XPS/NEXAFS Spectra Study

XPS and NEXAFS spectra of four stable C₄₀ isomers [29( C₂), 31( C _s), 38( D₂), and 39( D_{5 d})] have been investigated theoretically. We combined density functional theory and the full core hole potential method to simulate C 1s XPS and NEXAFS spectra for nonequivalent carbon atoms of four stable C₄₀ fullerene isomers. The NEXAFS showed obvious dependence on the four C₄₀ isomers, and XPS spectra are distinct for all four isomers, which can be employed to identify the four stable structures of C₄₀. Furthermore, the individual components of the spectra according to different categories have been investigated, and the relationship between the spectra and the local structures of C atoms was also explored.

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

The results herein demonstrate that the methods of circumscribing and the facile calculation of Hückel molecular orbital (HMO) eigenvalues by mirror-plane fragmentation have a broad application in the construction of carbon cluster series and the systematic study of trends in their electronic properties. In comparing open-ended nanotubes and their isomeric elongated fullerenes (bicapped nanotubes), we show that the former are more aromatic but the latter are more conjugated and that progressive elongation increases aromaticity and conjugation in both. Recursion equations that will allow one to obtain the eigenvalues to all 5-endcapped nanotubes are given.