Substituent effect on structure, stability, and aromaticity of novel B_nN_mC_20–(n+m) heterofullerenes

Abstract

We are focusing our calculations on the structural stabilities and electronic properties of 26 novel B n N m C 20-(n+m) heterofullerenes, with n, m = 1 − 5, at B3LYP/6-311++G** and B3LYP/AUG-cc-pVTZ levels of theory. Vibrational frequency calculations on C 20 and its analogues show that except B 2 N 2 C 16 (1) and B 2 N 2 C 16 (2), all other heterofullerenes are true minima. The heats of atomization energies, binding energy, band gaps (ΔE HOMO-LUMO ), aromaticity, nucleusindependent chemical shifts, thermodynamic stability, kinetic stability against electronic excitation, binding energy as a stability criterion of different configurations, geometrical parameters, conformational structures, conductivity, charge transfer, and possibility for hydrogen storage of these heterofullerenes strongly depend on their number of heteroatoms, topology, filling patterns, and locations as well as "B-site and N-site attachments." B 5 N 5 C 10 contains 5 alternating boron and nitrogen atoms in the equatorial position. It is predicted to be thermodynamically and kinetically the most stable against electron excites. Thus, it is energetically favorable and its electronic properties as well as stabilities make it perhaps a good candidate for an experimental investigation and testing verification.

Reaching for [6]n SiC‐cyclacenes and [6]n SiC‐acenes: A DFT approach

“…All species were predicted to have high conductivity and charge transfer, making them a possible candidate for hydrogen storage owing to their low band gap. Lowering the band gap could overcome the 2 electron pair repulsion and transform the ground states from singlet in more previous substituted cyclacnes [31,32] to triplet one in the [6] n SiC-cyclacenes and acenes (Table 1).…”

“…As demonstrated in Figure 7, [6] n SiC-cyclacenes contained 2 horizontal rings (silatrannulene) with 2 very similar molecular orbitals. [32] The silatrannulene circuits with 4k electrons in π orbitals were realized for [6] n SiCcyclacenes (n = 6, 8, 10, and 12). Indeed, each silatrannulene included 12, 16, 20, and 24 π electron, when n = 6, 8, 10, and 12 respectively (Figure 7).…”

“…[51] The SiCand GeC-nanotubes with alternative heteroatom and C atoms with full point charges introduced as good candidates for hydrogen storage. [32] So, MEP plots could show the hydrogen storage possibility of [6] n SiC-cyclacenes and acenes. To be expected, significant electron density transfer from doped Si atoms to the remaining C atoms of scrutinized structures, because of electronegative difference of C and Si (Pauling ENs: Si = 1.7, C = 2.5).…”

“…Heterocyclic derivatives of cyclacenes and polyacenes were studied through their molecular electronic properties, stabilities, and crystal structures of these materials. [12,[28][29][30][31][32] Actually, some synthesized heteroatom-carbon acenes led us to more study in this field. [33,34] In spite of silicon and germanium could be one of the most logical candidates to replace carbon, [35,36] there are few papers on silicon or germanium substitution cyclacenes.…”

“…[33,34] In spite of silicon and germanium could be one of the most logical candidates to replace carbon, [35,36] there are few papers on silicon or germanium substitution cyclacenes. [29,31,32] Hence, silabenzene as a stable structure was selected for more studies in this field. [37] So, in this work, [6] n SiC-cyclacenes and -acenes were theoretically studied at B3LYP/6-31G(d), B3LYP/cc-pvdz, and M06-2X/6-31G(d) (n = 6, 8, 10, and 12) ( Figure 2).…”