Are Antiaromatic Rings Stacked Face-to-Face Aromatic?

Corminbœuf, Clémence; Schleyer, Paul von Ragué; Warner, Philip

doi:10.1021/ol071183y

Cited by 81 publications

(96 citation statements)

References 69 publications

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“…These values are quite substantial, considering that aromatic tetramesitylporphyrin exhibits a HOMA value of 0.77. Accordingly, the attenuated BLA in 3b strongly supports an increase in aromaticity through stacking of antiaromatic π-systems, as predicted by Corminboeuf et al 8. and Bean and Fowler9.…”

Section: Resultssupporting

confidence: 78%

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Stacked antiaromatic porphyrins

et al. 2016

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Aromaticity is a key concept in organic chemistry. Even though this concept has already been theoretically extrapolated to three dimensions, it usually still remains restricted to planar molecules in organic chemistry textbooks. Stacking of antiaromatic π-systems has been proposed to induce three-dimensional aromaticity as a result of strong frontier orbital interactions. However, experimental evidence to support this prediction still remains elusive so far. Here we report that close stacking of antiaromatic porphyrins diminishes their inherent antiaromaticity in the solid state as well as in solution. The antiaromatic stacking furthermore allows a delocalization of the π-electrons, which enhances the two-photon absorption cross-section values of the antiaromatic porphyrins. This feature enables the dynamic switching of the non-linear optical properties by controlling the arrangement of antiaromatic π-systems on the basis of intermolecular orbital interactions.

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Section: Resultssupporting

confidence: 78%

“…Corminboeuf et al 8. have proposed that stacking of two antiaromatic systems in methano-bridged superphanes such as cyclobutadiene dimer 1 (Fig.…”

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confidence: 99%

Stacked antiaromatic porphyrins

et al. 2016

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“…Among them, we have attained a planar COT structure in 19(S) without bulky substituents unlike the other planar COTs, and X-ray crystallography showed a stacking structure [45]. Thus, the structure of 19(S) may be utilized for study on an intermolecular antiaromatic-antiaromatic interaction [88] by controlling the stacking manner with additional substituents at the side positions. Such experiments may also lead to these compounds becoming unique candidates for efficient organic electronic devices, in which the use of antiaromatic ring has not been tested.…”

Section: Discussionmentioning

confidence: 94%

“…Recently, it has been shown using NICS calculations that stacking of antiaromatic annulene rings into superphane structure can reverse antiaromaticity and result in through-space three-dimensional aromatic character [88]. As for the COT ring system 20 ( Figure 14), D 8h structure is minimum, indicating that the stacked ring aromaticity causes the bond length equalization.…”

Section: Stacking Of Planar Cot Ringsmentioning

confidence: 96%

Recent Studies on the Aromaticity and Antiaromaticity of Planar Cyclooctatetraene

2010

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Cyclooctatetraene (COT), the first 4nπ-electron system to be studied, adopts an inherently nonplanar tub-shaped geometry of D 2d symmetry with alternating single and double bonds, and hence behaves as a nonaromatic polyene rather than an antiaromatic compound. Recently, however, considerable 8π-antiaromatic paratropicity has been shown to be generated in planar COT rings even with the bond alternated D 4h structure. In this review, we highlight recent theoretical and experimental studies on the antiaromaticity of hypothetical and actual planar COT. In addition, theoretically predicted triplet aromaticity and stacked aromaticity of planar COT are also briefly described.

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“…The concept of 3D‐aromaticity, first proposed by Schleyer in 2007, predicted that stacking of 4nπ‐antiaromatic systems induces aromatic stabilization as a consequence of strong through‐space frontier orbital interactions. This proposal was supported by a theoretical study by Fowler et al.…”

Section: Figurementioning

confidence: 99%

Aromatic and Antiaromatic Cyclophane‐type Hexaphyrin Dimers

Osuka

2019

Chemistry An Asian Journal

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A peripherally strapped [28]hexaphyrin takes a rectangular conformation and exhibits antiaromatic character. A cyclophane‐type dimer consisting of such [28]hexaphyrins was synthesized from hexakis(pentafluorophenyl) [26]hexaphyrin via SNAr reaction with allyl alcohol, one‐pot intra‐ and intermolecular olefin metathesis under improved Hoveyda–Grubbs catalysis, and final reduction with NaBH4. The cyclophane‐type structures of [26]‐ and [28]hexaphyrin dimers have been revealed by X‐ray analysis. Studies on the structural, optical, and electronic properties have led to a conclusion that there is no favorable electronic interaction between the two [28]hexaphyrin segments and thus no indication of 3D aromaticity.

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Are Antiaromatic Rings Stacked Face-to-Face Aromatic?

Cited by 81 publications

References 69 publications

Stacked antiaromatic porphyrins

Stacked antiaromatic porphyrins

Recent Studies on the Aromaticity and Antiaromaticity of Planar Cyclooctatetraene

Aromatic and Antiaromatic Cyclophane‐type Hexaphyrin Dimers

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