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In the current work, the authors analyzed and compared the chemical behavior of some (anti)aromatic compounds. The species selected are benzene and cyclobutadiene as the aromatic and antiaromatic classical examples, respectively. Next, the anion Al42−, which is the first all‐metal molecule catalogued as aromatic and its non‐metallic isoelectronic analog, B42− were also analyzed. The antiaromatic clusters Al44− and B44− were studied in form of lithium salts. And the end, the non‐planar B12 boron cluster and its isoelectronic analogs (B11Be− and B11C+) were considered for being analyzed under the same criterium. The analysis was realized employing the following descriptors: molecular electrostatic potential and local hyper‐softness to get insights concerning local reactivity when facing reagents leading to ionic or covalent interactions. The results show that all the molecules analyzed presented some specific variations in their respective local reactivity despite being labeled as aromatic compounds. This analysis provides a notion that the local reactivity is more based on the nature of the atoms and the molecular geometry than the aromatic character by itself. [ABSTRACT FROM AUTHOR]

The KID (Koopmans in DFT) protocol usually applies in organic molecules of the closed-shell type. We used the KID procedure on an open-shell Mo-based system for the first time to choose the most suitable density functional to compute global and local reactivity descriptors obtained from the conceptual density-functional theory (DFT). From a set of 18 density functionals, spread from the second until the fourth rung of Jacob's ladder: BLYP, BP86, B97-D, MN12-L, MN15-L, M06-L, M11-L, CAM-B3LYP, PBE0, B3LYP, N12-SX, M06-2X, MN15, MN12-SX, ωB97X-D, M11, LC-ωHPBE, and APFD, we concluded that CAM-B3LYP provides the best outcome, and in the second place, M06-2X. Because the vertical first ionization potential and vertical first electron affinity in the ground state (gs) are defined as follows I = E gs ( N - 1) - E gs ( N ) and A = E gs ( N ) - E gs ( N + 1), where E gs ( N - 1), E gs ( N ), and E gs ( N + 1) correspond to energies of the system bearing N , N + 1, and N - 1 electrons, along with Koopmans' theorem (KT) given by I ≈ -ε HOMO (ε HOMO , highest occupied molecular orbital energy) and A ≈ -ε LUMO (ε LUMO , lowest unoccupied molecular orbital energy), the deviation from the KT was performed by the use of the index, such that J I = | E gs ( N - 1) - E gs ( N ) + ε HOMO | and J A = | E gs ( N ) - E gs ( N + 1) + ε LUMO |, which are absolute deviations from the perspective of I and A , respectively. Furthermore, the ε SOMO (SOMO: singly-occupied molecular orbital energy) leads us to another index given by |ΔSL| = |ε SOMO - ε LUMO |. Therefore, J HL and |ΔSL| are indexes defined to evaluate the quality of the KT when employed within the context of quantum chemical calculations based on DFT and not the Hartree-Fock theory. We propose the index that could be more suitable to choose the most proper density functional because the J HL and |ΔSL| are independent indexes., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)