Borataalkene or boratabenzene? Understanding the aromaticity of 9-borataphenanthrene anions and its central ring

2022

ACS Omega

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Aromaticity is a useful tool to rationalize the structure, stability, and reactivity in several compounds. Although aromaticity is not directly an observable, it is well accepted that electronic delocalization around the molecular ring is a key stabilizing feature of aromatic compounds. This contribution presents a systematic evaluation of the capability of delocalization and reactivity criteria to describe aromaticity in a set of fluorinated benzenes. The aromaticity indices are compared with quantities obtained from the magnetic criteria of aromaticity, i.e., the strength of the ring current induced by an external magnetic field and the popular NICS zz (1) index. In this evaluation, the indices based on delocalization criteria used are aromatic fluctuation index (FLU), para-delocalization index (PDI), PDI π , and the multicenter delocalization index (MCI). In addition, indices based on the bifurcation values of scalar functions are derived from electron density such as electron localization function (the π contribution, ELF π ) and the π contribution of the localized orbital locator (LOL π ). Furthermore, reactivity indices based on chemical reactivity and the information-theoretic (reactivity) approach are para-linear response (PLR), Shannon entropy, Fisher information, and Ghosh–Berkowitz–Parr (GBP) entropy. The results obtained show that the delocalization-based indicators present a high sensitivity to slight changes in aromaticity and that the reactivity criterion can be considered as a complementary tool for the study of this phenomenon, even when these changes are minimal. These results encourage the use of multiple indicators for a complete understanding of aromaticity in various chemical compounds.

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Evaluation of Slight Changes in Aromaticity through Electronic and Density Functional Reactivity Theory-Based Descriptors

Báez‐Grez

2022

ACS Omega

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“…24 Beyond classical counting rules, several strategies and indicators have been developed to not only determine the (anti)aromatic character of a system, but also to quantify it. [25][26][27] There is a plethora of indicators of aromaticity that are based on different magnetic, 28 geometric, 29 electronic, 30 reactivity, 31,32 and orbital localization properties, 33 and more recently also derived from the information-theoretic approach. 34 However, the first three are the most popular and used criteria to quantify aromaticity.…”

Section: Introductionmentioning

confidence: 99%

Acenes and phenacenes in their lowest-lying triplet states. Does kinked remain more stable than straight?

Phys. Chem. Chem. Phys.

Báez‐Grez

Solà

2021

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“…In the present article, the local aromaticity in 1 and its isomers has been assessed by means of a number of aromaticity criteria based on different magnetic, geometric, energetic, and delocalization properties, as usually recommended. , The results obtained show that there is a reduction in the aromatic character in the 6MR, whereas the 5MR presents a slight increase in its aromatic character when the compounds are ordered as follows: 1 → 2 → 3 .…”

Section: Introductionmentioning

confidence: 99%

The Relative Stability of Indole Isomers Is a Consequence of the Glidewell-Lloyd Rule

Solà

2020

J. Phys. Chem. A

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Indole (1) is a heterocyclic aromatic compound consisting of a pyrrole ring (5MR) fused with a benzene ring (6MR). This compound is highly stable, found in several natural products, and used as a building block for the synthesis of novel organic compounds. On the other hand, its isomers isoindole (2) and indolizine (3) are much less stable and are normally isolated when bonded to other stable compounds. The stability of these compounds has been analyzed in terms of local aromaticity using magnetic, geometric, and delocalization criteria. All criteria used indicate that there is a continuing reduction in aromaticity of the 6MR whereas, for the 5MR, the aromaticity increases when going from 1 to 3. This is confirmed by Natural Resonance theory calculations indicating that the resonant structures which retain the aromaticity of 5MR are the ones having the largest contribution.The results obtained suggest that the relative stability of indole isomers is a consequence of the Glidewell-Lloyd rule.