Validation of the recently developed aromaticity index D3BIA for benzenoid systems. Case study: acenes

Abstract

There are four types of aromaticity criteria: energetic, electronic, magnetic and geometric. The delocalization, density and degeneracy-based index of aromaticity, D3BIA, is an electronic aromaticity index from QTAIM that is not reference dependent and can be used for aromatic, homoaromatic, sigma aromatic and other aromatic systems with varying ring size containing hetereoatoms or not. We used B3LYP, MP2 and MP3 methods to search for linear relations between well-known aromaticity indices and D3BIA for a series of acenes. We found that the D3BIA versus FLU correlation exceeded 91 % and reasonably good correlations exist between D3BIA and HOMA and between D3BIA and PDI. Previous works have shown that D3BIA can be used for homoaromatic systems and tetrahedrane derivatives (sigma aromaticity), but no previous work has validated D3BIA for benzenoid systems. This is the first time we have shown that D3BIA can be used successfully for benzenoid systems, for example, acenes. This work supports and validates the use of D3BIA in classical aromatic systems.

Application of a quantum genetic algorithm and QTAIM analysis in the study of structural and electronic properties of neutral bimetallic clusters NaxLiy (4 ≤ x + y ≤ 10)

“…For example, in Na 1 Li 5 and Na 2 Li 4 clusters, it is expected that the degree of degeneracy (not taking into account any charge transfer) would be 0.833 and 0.667, respectively. However, in Na 1 Li 5 system, there are three lithium atoms with close atomic energies (Li3 to Li5), in accordance with the D3BIA degree of degeneracy criterion to systems in cage [46], and two other lithium atoms of lower energy (Li2 and Li6). Due to Li2 and Li6 are closer to Na1 (see Fig.…”

“…In order to better evaluate the atomic energies, we used the formula of the degree of degeneracy, δ, from D3BIA aromaticity index [46], i.e., δ = n/N, where in this work "n" represents the number of subset of degenerate or neardegenerate atoms (or the total number of near-degenerate atoms when this number is greater than the number of subsets, e.g., in Na 5 Li 1 ) and "N" is the total number of the atoms of the cluster. The term "near-degenerate atoms" means that the atomic energy between any atomic pair is smaller than 0.009 Hartree.…”

“…In addition, the atomic interactions of Na x Li y systems (x + y = 6) were analyzed by the Quantum Theory of Atoms in Molecules (QTAIM). Moreover, the delocalization, density, and degeneracy-based index of aromaticity (D3BIA) [46] and nucleus-independent chemical shifts (NICS) [47,48] were also applied to evaluate a possible aromaticity of some clusters.…”

Kekulene: On-Surface Synthesis, Orbital Structure, and Aromatic Stabilization

“…While the HOMA is not the only yardstick of aromaticity, 11 other suggested criteria of aromaticity based on geometric, energetic, magnetic and electronic properties of molecules are found to be in good correlation with the HOMA. 11,35,36 As an advantage of the HOMA concept, the partial equalization of bond lengths in aromatic systems, which is quantified by the HOMA value, can be easily obtained from DFT calculations. In addition, not only the aromaticity of the molecule as a whole, but also the aromaticity of any cyclic conjugation path can be easily quantified, allowing, e.g., the separate description of local, peripheral and global aromaticities.…”

Kekulene: On-Surface Synthesis, Orbital Structure and Aromatic Stabilization

“…The original and fundamental idea is that each pair of carbon atoms can be involved in both, a σ-and a π-bond, with We use the HOMA (red color scale and white numbers in with the HOMA. 11,35,36 As an advantage of the HOMA concept, the partial equalization of bond lengths in aromatic systems, which is quantified by the HOMA value, can be easily obtained from DFT calculations. In addition, not only the aromaticity of the molecule as a whole, but also the aromaticity of any cyclic conjugation path can be easily quantified,…”