Trapping N5 rings and N3 chains on the outer surface of fullerene C60: a theoretical study

Introducing a novel C50N10 azafullerene with chained nitrogen atoms on a buckyball pole: structure, stability, vibration, and electronic properties

CONTEXT

Fullerenes are of high significance due to their unique chemical properties and various applications in technology, particularly materials science, drug delivery, electronics, and nanoelectronics. In the recent years, many attempts have been focused to introduce new heteroatom-doped fullerenes having advanced chemical properties and tunable electronic traits, which make them a potential candidate for application in many branches of sciences. In this study, a novel C₅₀N₁₀ azafullerene with a fascinating structure of chained nitrogen atoms on a buckyball pole, with different electronic and optical properties compared to its other analogs, is introduced and trace of N-N substructures on the surface of C₆₀ fullerene cage is investigated. For this molecule, four structural isomers including 3 structures with chain N atoms on a fullerene buckyball pole (NP isomers) and one isomer with separated N atoms (SN isomer) have been studied. All isomers have been studied with and without symmetry constraints, and the symmetry influence on the structure and stability of each isomer has been investigated. Although the studied NP structures have lower stability than the SN isomer, some reasons (such as their more all-carbon hexagonal rings, breaking some of their N-N bonds for partial opening of the cage and creating bigger rings in order to get rid of the unfavorable strain, as well as decreasing the N-N lone pair repulsions) lead to the acceptable stability of these structures with the bonded N atoms. The results of atomization energy and vibrational frequency calculations indicate that isomers with the bonded N atoms have acceptable stabilities and do not decompose into their constituent components. Investigation on the structural parameters demonstrates important roles of the number of all-carbon hexagonal rings, the number of N-N junction, and the molecule symmetry in the stability of the structures with the bonded N atoms. Study on the electronic and optical properties indicates that the target structures exhibit high electronic polarizability, relatively small HOMO/LUMO gap, high first- and second-order hyperpolarizability, and also large third-order nonlinear optical properties.

METHODS

All calculations have been performed using Gaussian G09 software using density functional theory (DFT) approach. Three-parameter Beck hybrid exchange functional (B3) hybridized with nonlocal correlation functional of Lee, Yang, and Parr (LYP) has been employed as the level of DFT calculations. All optimizations have been performed at double-zeta polarized (DZP) split valence 6-31G(d,p) and also at split valence TZP 6-311G(d,p) basis sets. The global minimum structures have been confirmed by frequency calculations at the same level of optimizations. The natural bond orbital (NBO) analyses, frontier orbital surfaces imaging, atomic charges, and charge transfer analyses have been achieved by GenNBO program package.

Computational insights into novel dicobalt polynitrogen: structure, stability, intermolecular interaction, and application

Previous studies have suggested that polynitrogen species are significant as potential candidates for superior energetic material. In this paper, the polynitrogen species of Co2(N5)4 were reasonably designed and studied by the density functional theory (DFT), and five isomers of Co2(N5)4 were selected. These species were explored in detail, including structure, stability, intermolecular interaction, and application. The five isomers, each with its own special structure feature, were stable enough based on the analysis of bond energy, chemical hardness, and aromaticity. Furthermore, the intermolecular interactions suggested the presence of a covalent interaction in the Co–Co and N–N bonds, the electronic delocalization in cyclo-N5, and the ionic feature in the Co–N bond. In addition, all of the title species held high-energy content. Compared with the known high energy density materials of HB(N5)3Be2(N5)3BH, energetic material of nitromethane, and famous nitramine explosive HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), Co2(N5)4 holds a stronger advantage. The five Co2(N5)4 species were located at 27.8–35.8 kcal/mol per N2 unit, their energy densities were about 2.73 × 104 MJ/kg, and their mass densities were in the range of 2.60–2.74 g/cm3. Significantly, the 4-1 was the most stable, and its density was also the greatest among the five species. Thus, it has the most potential as a high energy density material.