The evolutions of the structure stability, vibrational frequency, frontier orbital, and electronegativity of the unconventional exohedral fullerenes C64X4 (X=H, F, Cl, Br, and I): A density functional study

A theoretical study of electronic effects in alkyne‐linked reactive intermediates: (nitrenoethynyl)methylenes, (nitrenoethynyl)silylenes, and (nitrenoethynyl)germylenes

“…The C 3 –M 4 bond indicated the highest contribution to their relative HOMO orbitals, while C 2 –C 3 bond and M 4 atomic orbitals revealed the highest contribution to their relative LUMOs. The HOMO–LUMO energy gap (Δ E LUMO–HOMO ) is a conventional measure of kinetic stability . A narrow HOMO–LUMO gap results in low kinetic stability and high chemical reactivity.…”

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

“…The nucleus independent chemical shift values (NICS) were selected as a criterion for aromaticity of [6] n SiC‐cyclacenes and ‐acenes, . Despite the controversy surrounding this method for aromaticity measurements of a few compounds, NICS were introduced the most exploited for the calculation of aromaticity in nanostructures including carbon nanotubes, cyclacenes, trannulenes, and fullerene systems …”

Chemical Bonding by the Chemical Orthogonal Space of Reactivity

“…However, the electrophilicity index (ω = χ 2 /2 η ) increases from C 64 F 4 to C 64 I 4 paralleling the decreasing stability recorded by means of decreasing of bond dissociation energies, energy gaps, and maximal frequencies. They indicate a general nonaromatic character for the carbon halogen molecules of C 64 X 4 (X = F, Cl, Br and I) [ 65 ]; Electronic properties of oxides were successfully established in terms of the electronegativity- chemical hardness binomial ( χ , η ) coupling namely as (i) ( χ ↑ & η ↓) is specific for oxides of transition elements with high oxidation state; (ii) ( χ ↑ & η ↑) characterizes the insulators with large optical (HOMO-LUMO) gap; (iii) ( χ ↓ & η ~>) feature alkali and alkaline earth oxides; and (iv) ( χ ↓ & η ↑) describe ionic oxides with relatively large optical gap [ 66 ]; The atoms-in-molecule Bent rule, according to which “more electronegative substituents prefer hybrid orbitals having less ‘s’ character and more electropositive substituents prefer hybrid orbitals having more ‘s’ character” was found consistent with the maximum chemical hardness reactivity principle, for a series of isomers, since the more electronegative atom occupies the axial position has maximum hardness. However, the same rule is less correlating with the minimum polarizability principle, being the last more sensitive to the basis set used, especially when the diffusion is this way better represented; application on different isomers of SF 4 , SF 4 O as well as for a family of PCl x F 5−x (x = 1–4) in combination with B3LYP with different basis sets of computational density functional theory confirms such general tendencies [ 67 ]; On the other side, the simple MP2 model combined with the straight approximation of chemical hardness kernel as the Dirac localized function, , finely orders the Lewis acids and bases the computed global chemical hardness perspective when compared with experimental data [ 68 ].…”

“…However, the electrophilicity index (ω = χ 2 /2 η ) increases from C 64 F 4 to C 64 I 4 paralleling the decreasing stability recorded by means of decreasing of bond dissociation energies, energy gaps, and maximal frequencies. They indicate a general nonaromatic character for the carbon halogen molecules of C 64 X 4 (X = F, Cl, Br and I) [ 65 ];…”