In the quest of Hückel–Hückel and Hückel–Baird double aromatic tropylium (tri)cation and anion derivatives

Escayola, Sílvia; Vedin, Nathalie Proos; Poater, Albert; Ottosson, Henrik; Solà, Miquel

doi:10.1002/poc.4447

Cited by 4 publications

(7 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, several hexaselanylbenzene and hexatellanylbenzene dications [C 6 (ChR) 6 ] 2+ (Ch = Se, Te; R = H, Me, Ph) were found experimentally and computationally to be doubly aromatic compounds. − Borazine analogues of hexaiodobenzene and hexakis(selenyl)benzene dication [B 3 N 3 I 6 ] 2+ as well as [B 3 N 3 (TeH) 6 ] 2+ were also reported to be doubly aromatic, although the π-aromaticity of borazine is known to be extensively lower than that of benzene . And very recently, the triplet state of [C 7 Br 7 ] 3+ has been found to be π-Hückel aromatic (with six π-electrons in the tropylium ring) and weakly σ-Baird aromatic (with 12 delocalized σ-electrons in the Br 7 ring, Scheme b) . Let us mention that Baird’s rule states that annulenes with 4 n π-electrons are aromatic, and those with 4 n +2 are antiaromatic in their lowest-lying triplet states. − Other examples are the double σ- and π-aromaticity in bishomotriboriranide and in twisted thienylene–phenylene structures in toroidal and catenated topologies. , …”

Section: Introductionmentioning

confidence: 99%

Single─Not Double─3D-Aromaticity in an Oxidized Closo Icosahedral Dodecaiodo-Dodecaborate Cluster

Poater,

Escayola,

Poater

et al. 2023

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

3D-aromatic molecules with (distorted) tetrahedral, octahedral, or spherical structures are much less common than typical 2D-aromatic species or even 2D-aromatic-in-3D systems. Closo boranes, [B n H n ] 2− (5 ≤ n ≤ 14) and carboranes are examples of compounds that are singly 3D-aromatic, and we now explore if there are species that are doubly 3D-aromatic. The most widely known example of a species with double 2D-aromaticity is the hexaiodobenzene dication, [C 6 I 6 ] 2+ . This species shows π-aromaticity in the benzene ring and σ-aromaticity in the outer ring formed by the iodine substituents. Inspired by the hexaiodobenzene dication example, in this work, we explore the potential for double 3D-aromaticity in [B 12 I 12 ] 0/2+ . Our results based on magnetic and electronic descriptors of aromaticity together with 11 B{ 1 H} NMR experimental spectra of boron-iodinated o-carboranes suggest that these two oxidized forms of a closo icosahedral dodecaiodo-dodecaborate cluster, [B 12 I 12 ] and [B 12 I 12 ] 2+ , behave as doubly 3D-aromatic compounds. However, an evaluation of the energetic contribution of the potential double 3D-aromaticity through homodesmotic reactions shows that delocalization in the I 12 shell, in contrast to the 10σ-electron I 6 2+ ring in the hexaiodobenzene dication, does not contribute to any stabilization of the system. Therefore, the [B 12 I 12 ] 0/2+ species cannot be considered as doubly 3D-aromatic.

show abstract

Section: Introductionmentioning

confidence: 99%

Single─Not Double─3D-Aromaticity in an Oxidized Closo Icosahedral Dodecaiodo-Dodecaborate Cluster

Poater,

Escayola,

Poater

et al. 2023

J. Am. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Miquel Solà and Sílvia Escayola’s article explores double aromaticity in substituted tropylium cations [ 95 ]. Hexaiodobenzene and hexakis(phenylselenyl)benzene dications are known for their σ- and π-double aromaticity, making their characterization essential for organic and structural chemistry.…”

Section: Complex Molecule Synthesismentioning

confidence: 99%

“…The presence of strong electronic repulsion between external substituents or substituents with np orbitals that are not diffuse enough can quench the σ-aromaticity by puckering the benzene or tropylium cation rings. The most interesting species analyzed in the study were 1C 7 Br 7 +3 , which had an internal Hückel aromatic tropylium ring and an external Hückel antiaromatic Br 7 ring, and 3 C 7 Br 7 +3 , which had an internal Hückel aromatic tropylium ring and an external weak Baird aromatic Br 7 ring [ 95 ].…”

Section: Complex Molecule Synthesismentioning

confidence: 99%

Tropylium Ion, an Intriguing Moiety in Organic Chemistry

Zahra,

Saeed,

Mumtaz

et al. 2023

Molecules

View full text Add to dashboard Cite

The tropylium ion is a non-benzenoid aromatic species that works as a catalyst. This chemical entity brings about a large number of organic transformations, such as hydroboration reactions, ring contraction, the trapping of enolates, oxidative functionalization, metathesis, insertion, acetalization, and trans-acetalization reactions. The tropylium ion also functions as a coupling reagent in synthetic reactions. This cation’s versatility can be seen in its role in the synthesis of macrocyclic compounds and cage structures. Bearing a charge, the tropylium ion is more prone to nucleophilic/electrophilic reactions than neutral benzenoid equivalents. This ability enables it to assist in a variety of chemical reactions. The primary purpose of using tropylium ions in organic reactions is to replace transition metals in catalysis chemistry. It outperforms transition-metal catalysts in terms of its yield, moderate conditions, non-toxic byproducts, functional group tolerance, selectivity, and ease of handling. Furthermore, the tropylium ion is simple to synthesize in the laboratory. The current review incorporates the literature reported from 1950 to 2021; however, the last two decades have witnessed a phenomenal upsurge in the utilization of the tropylium ion in the facilitation of organic conversions. The importance of the tropylium ion as an environmentally safe catalyst in synthesis and a comprehensive summary of some important reactions catalyzed via tropylium cations are described.

show abstract

mentioning

confidence: 99%

“…You et al [ 15 ] report on osmapentalene and osmapyridinium complexes with carbone ligands which are aromatic in both the lowest lying singlet and triplet states, a phenomenon labeled as adaptive aromaticity. The paper by Escayola et al [ 16 ] describes the double Hückel and Baird aromaticity of the triplet state of C 7 Br 7 +3 , which features an inner Hückel‐aromatic tropylium ring and an outer weak Baird‐aromatic Br 7 ring. Finally, Preethalayam et al [ 17 ] analyze the extent of Baird aromaticity in the T 1 states of BN/CC cyclooctatetraene isosteres, revealing large differences between the magnetic aspect of aromaticity (response aromaticity) and the electronic and energetic aspects (intrinsic aromaticity).…”

mentioning

confidence: 99%