Shaping Antiaromatic π‐Systems by Metalation: Synthesis of a Bowl‐Shaped Antiaromatic Palladium Norcorrole

Yonezawa, Tsubasa; Shafie, Siham A.; Hiroto, Satoru; Shinokubo, Hiroshi

doi:10.1002/anie.201706134

Cited by 55 publications

(39 citation statements)

References 59 publications

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“…Figure 2 depicts highlights of the B3LYP 7–9 -D3 10 /STO-TZ2P optimized geometries. The energy minima turned out to be a C i -symmetric wave conformation for H 2 Nc 11 and a C 2v -symmetric dome conformation for NiNc. The planar D 2h form of NiNc, just 0.03 eV (0.7 kcal/mol) higher in energy relative to the C 2v minimum, was found to correspond to the transition state for the bowl inversion process.…”

Section: Resultsmentioning

confidence: 97%

“…The X-ray structures of certain other NiNc derivatives (YEQKUC 6 ; CALRAL 12 ; MUJTIW, MUJTOC 15 , on the other hand, exhibit larger differences (>0.04 Å) between adjacent C meso -C α bonds. To this list may be added a slightly saddled CuNc (YEHTOX) 11 and a strongly domed PdNc (YEHTEN) 11 structure, which exhibit an intermediate difference (~0.03 Å) between adjacent C meso -C α bonds. Significant bond localization has been observed for several NiNc derivatives with strongly conjugating β -substituents such as cyano 15 , nitro 16 or amino 17 ; these systems are not within the purview of the present study.…”

Section: Resultsmentioning

confidence: 99%

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Norcorrole as a Delocalized, Antiaromatic System

Conradie

Foroutan‐Nejad

Ghosh

2019

Sci Rep

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Nickel norcorrole provides an unusual example of a molecule that is strongly antiaromatic according to the magnetic criterion, but which exhibits, according to high-quality DFT calculations, a symmetric, delocalized structure with no difference in bond length between adjacent Cmeso-Cα bonds. A fragment molecular orbital analysis suggests that these discordant observations are a manifestation of the high stability of the dipyrrin fragments, which retain their electronic and structural integrity even as part of the norcorrole ring system.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Norcorrole as a Delocalized, Antiaromatic System

Conradie

Foroutan‐Nejad

Ghosh

2019

Sci Rep

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“…The Soret bands of 4·PF 6 and 5·PF 6 are observed at 387 and 398 nm, respectively, and the associated Q-bands at 449 and 561 nm for 4·PF 6 and 463 and 580 nm for 4·PF 6 . Shinokubo and co-workers established methods for the synthesis of norcorroles with anti-aromatic characteristics that are stable compounds under ambient conditions, [48][49][50] but interestingly they show unique reactivity towards nucleophiles. Generally, [14]triphyrin(2.1.1) derivatives emit very weak fluorescence (Φ f < 1 %), mainly because of their flexible conformation with small cavity.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of [14]Oxatriphyrins(2.1.1) and Their Transformation into Ethane‐Bridged Oxatripyrrins by Boron Complexation

et al. 2018

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[14]Oxatriphyrins(2.1.1) incorporating a furan moiety in the macrocycle have been synthesized by intramolecular McMurry coupling of oxatripyrromethane followed by oxidation. The [14]oxatriphyrins(2.1.1) are highly planar structures with 14π‐electron aromaticity, inducing typical porphyrin‐like absorption and fluorescence features. Compared with [14]thiatriphyrin(2.1.1) and arene‐fused oxatriphyrins(2.1.1), arene‐unperturbed [14]oxatriphyrins(2.1.1) exhibit stronger aromatic characteristics and fluorescence properties. The borylation of [14]oxatriphyrins(2.1.1) with dichloro(phenyl)borane resulted in the formation of boron complexes with a reduced olefin bridge. As a result of the reduction, the macrocycles of these boron complexes lost their aromatic properties, although the targeted boron complexes were predicted to have distinct anti‐aromatic properties by DFT calculations. The resultant ethane‐bridged oxatripyrrins exhibit intense emission because of their rigid structures.

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“…This macrocycle 35 with a bridging oxygen between two pyrrolic units was identified as an aromatic species and from 1 H NMR spectroscopy and further confirmed computational studies. Later, the same group explored the chemistry of this Ni(II) corrole complex and was also successful in the synthesis of similar Cu(II) and Pd(II) norcorrole complexes 35 with altered structural features. Further, this macrocycle undergoes cycloaddition reaction leading to π-extended macrocycle.…”

Section: Account Syn Lettmentioning

confidence: 99%

Syntheses and Redox Chemistry of Antiaromatic Core-Modified Isophlorinoids

Panchal¹,

Reddy²,

Anand³

2018

Synlett

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During the attempted total synthesis of chlorophyll, Woodward hypothesized the formation of tetrapyrrolic 20π isophlorin as a transient antiaromatic intermediate which provides a plausible template to synthesize stable antiaromatic molecules. Despite its structural similarity with the 18π aromatic porphyrin, it significantly differs in its electronic and chemical properties. However, due to its unstable nature under ambient conditions it immediately gets oxidized to stable 18π aromatic porphyrin. Similar macrocyclic structures with β-substituted heterocycles, such as furan/thiophene/selenophene, have been synthesized, which undergo facile oxidation to yield the 18π porphyrin dication. Attempts to synthesize stable tetrapyrrolic isophlorin and its metal complex have remained unaccomplished till date. Strategies to synthesize stable core-modified 20π isophlorin and its confused isophlorin derivative have met with considerable success. Predominantly, they are synthesized by replacing three or four pyrroles with furan/thiophene. The 20π systems either with four furan units or with a ‘pair’ of furan and thiophene units were sufficiently stable enough to resist oxidation towards the corresponding porphyrin dication. The 20π isophlorins displayed noncovalent interactions with the curved π surface of fullerene which predominantly rises due to van der Waals attraction between the dissimilar π systems. This antiaromatic isophlorin-fullerene complexes were obtained and successfully characterized by single-crystal X-ray diffraction studies. Replacing only three pyrroles by furan rings yielded the first stable pyrrole derivative of antiaromatic 20π isophlorin, which can be reversibly oxidized to 18π aromatic porphyrin without deprotonating the inner pyrrole NH. In addition, replacing all the pyrrole units of N-confused porphyrin with thiophene yielded the first derivative of confused isophlorin. Further, its two-electron oxidation led to the formation of 18π aromatic cation with enhanced aromaticity. The structure and electronic properties of the oxidized and neutral species were unambiguously determined from a combination of spectroscopic techniques, X-ray crystallography, and computational methods. These studies reveal that antiaromatic systems like isophlorin and its confused isophlorin derivative can be stabilized under ambient conditions and they offer potential to explore the chemistry of 4nπ systems. This Account focuses of recent advances in 20π antiaromatic isophlorins, confused isophlorins, and nocorroles along with their redox chemistry. 1 Introduction2 Stable 20π Isophlorins2.1 Furan-/Thiophene-Based Isophlorins2.2 Pyrrole Isophlorins3 Confused Isophlorins3.1 Isophlorin-Fullerene3.2 meso-meso-Bridged Tetraoxaisophlorin Dimer4. Norcorroles5. Conclusion and Outlook

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Shaping Antiaromatic π‐Systems by Metalation: Synthesis of a Bowl‐Shaped Antiaromatic Palladium Norcorrole

Cited by 55 publications

References 59 publications

Norcorrole as a Delocalized, Antiaromatic System

Norcorrole as a Delocalized, Antiaromatic System

Synthesis of [14]Oxatriphyrins(2.1.1) and Their Transformation into Ethane‐Bridged Oxatripyrrins by Boron Complexation

Syntheses and Redox Chemistry of Antiaromatic Core-Modified Isophlorinoids

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