Chiral Stable Phenalenyl Radical: Synthesis, Electronic‐Spin Structure, and Optical Properties of [4]Helicene‐Structured Diazaphenalenyl

Ueda, Akira; Wasa, Hideki; Suzuki, Shuichi; Okada, Keiji; Sato, Kazunobu; Takui, Takeji

doi:10.1002/ange.201202654

Cited by 29 publications

(13 citation statements)

References 67 publications

(10 reference statements)

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“…The spectrum is significantly different from that of DAPC. [15] The primary transition appears at a similar energy, but in 1C bands can be seen at 450 and 400 nm that are not present in DAPC. The N-alkylation must result in a significantly different electronic structure.…”

Section: Radical Stabilitymentioning

confidence: 93%

“…[12a, 13a, 14] Recently, a N,N'-dealkylated derivative of DMQA + , with tertbutyl groups in the para positions, was used as a precursor for a highly stable and delocalised diazaphenalenyl radical (DAPC, see Scheme 1). [15] In a flat conjugated system, bulk and highly stabilising oxo or cyanoethylene units are required to achieve the same degree of stabilisation.…”

Section: Introductionmentioning

confidence: 99%

“…In inert solvents, [15] here benzonitrile, DMQA + is stable as a cation and radical. The accessible redox states are shown in Scheme 3.…”

mentioning

confidence: 99%

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Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

2014

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N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA+) is a configurationally locked [4]helicene, a stable carbenium ion and a potent near‐infrared emitter. The versatile synthesis and resolution into M and P enantiomers has made DMQA+ and its congener helicenium derivatives attractive chiral dyes and building blocks. In the present study, electrochemical and spectroscopic studies showed that several redox states of DMQA+ are accessible and stable. The cation stability towards nucleophiles is determined and it is shown that the addition of OH− proceeds with a surprisingly low rate of reaction. The synthetic methodologies leading to DMQA+ are described, and the chemistry occurring from the different redox states of DMQA is identified. This [4]helicene is shown to be a unique molecular framework that is stable as a neutral radical and very stable as a carbenium ion.

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Section: Radical Stabilitymentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

2014

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“…Phenalenyl that is a planar neutral π-radical with delocalized electronic spin over its hydrocarbon framework has been utilized to construct a lot of functional open-shell molecules (Figure 3, Table 3). [35] Based on diazaphenalenyl scaffold, T. Takui and Y. Morita et al prepared a [4]heterohelicene 16 as a neutral radical, [36] which was the first example of an isolated air-stable helicene radical, irrespective of the absence of its crystallographic analysis and magnetic susceptibility measurement. 492, 565, 593, 668, 778, 1017, 1304, 1604 [40] [a] λ max values in parentheses are estimated from the absorption spectra by the authors of this review.…”

Section: Neutral Radicals Of Helicenesmentioning

confidence: 99%

Helicene Radicals: Molecules Bearing a Combination of Helical Chirality and Unpaired Electron Spin

2020

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Chiral helicenes that have helical π-conjugated frameworks comprised of ortho-fused aromatic rings have been intensively investigated for several decades owing to their attractive properties and high potential for a variety of applications. In contrast, studies concerning helicene radicals (open-shell helicenes) formed by redox reactions have been severely limited due to inherent high reactivity of organic radicals. However, open-shell helicenes possessing a combination of chirality and unpaired electron spin(s) delocalized on helical π-conjugated orbital(s) are promising for novel synergic magnetic functions. Recently, several kinds of isolable air-stable helicene radicals have been prepared to enable their detailed analysis of the crystal structures and physicochemical properties. This Minireview describes the recent advances and future prospects of organic-based helicene radicals categorized into three groups: 1) ionic radicals, 2) neutral radicals, and 3) diradicals.

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“…To the best of our knowledge, only four examples of [4]helicene radicals have been reported. [30][31][32] [33] Of these radicals, two showed limited stability, [30] [31] and one was never isolated. [32] Notably, no X-ray crystallographic structure of any [4]helicene-based neutral radical has been reported.…”

mentioning

confidence: 99%

Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

Shaikh¹,

Hossain²,

Moutet³

et al. 2020

Preprint

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<p>Stable organic radicals have gained considerable attention in the fields of catalysis and material sciences. In particular, helical molecules are of great interest in the development and application of novel organic radicals in optoelectronic and spintronic materials. Here we report the syntheses of highly stable neutral quinolinoacridine radicals by chemical reduction of their quinolinoacridinium cation analogs. The crystal structures of these [4]helicene radicals were determined by X-ray diffraction. Electron paramagnetic resonance (EPR) measurements, supported by density functional theory (DFT) calculations, indicate that the unpaired electron is mostly localized, showing more than 40% of spin density located at the central carbon of the [4]helicene radicals. Quantitative conversion from neutral radical to cation is observed upon exposure to air, monitored via UV-vis spectroscopy. The successful photoreductive dehalogenation of aryl halides occurs in the presence of 10 mol% of [4]helicene radical under blue light.<b></b></p>

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Chiral Stable Phenalenyl Radical: Synthesis, Electronic‐Spin Structure, and Optical Properties of [4]Helicene‐Structured Diazaphenalenyl

Cited by 29 publications

References 67 publications

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

Helicene Radicals: Molecules Bearing a Combination of Helical Chirality and Unpaired Electron Spin

Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

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Chiral Stable Phenalenyl Radical: Synthesis, Electronic‐Spin Structure, and Optical Properties of [4]Helicene‐Structured Diazaphenalenyl

Cited by 29 publications

References 67 publications

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA+): A [4]Helicene with Multiple Redox States

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA+): A [4]Helicene with Multiple Redox States

Helicene Radicals: Molecules Bearing a Combination of Helical Chirality and Unpaired Electron Spin

Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

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Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States