Protonation-Induced Antiaromaticity in Octaaza[8]circulenes: Cyclooctatetraene Scaffolds Constrained with Four Amidine Moieties

Shuhei Akahori; Atsushi Kaga; Jinseok Kim; Hideki Yorimitsu; Dongho Kim; Hiroshi Shinokubo; Yoshihiro Miyake

doi:10.1002/asia.202200244

Protonation-Induced Antiaromaticity in Octaaza[8]circulenes: Cyclooctatetraene Scaffolds Constrained with Four Amidine Moieties

Shuhei Akahori, Atsushi Kaga, Jinseok Kim, Hideki Yorimitsu, Dongho Kim, Hiroshi Shinokubo, Yoshihiro Miyake

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

Abstract

The switching of cyclic π-conjugation pathways using external stimuli is an attractive research topic in the field of organic chemistry. Here, we synthesized C_4h-symmetric octaaza[8]circulenes with four peripherally arranged amidine moieties that exhibit enhanced antiaromaticity upon protonation. Titration experiments with methanesulfonic acid revealed the formation of the tetraprotonated forms of the octaaza[8]circulenes in solution. Single-crystal X-ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaaza[8]circulenes is enhanced by the delocalization of charge through the protonation of the pyridine rings.

Original language	English
Article number	e202200244
Journal	Chemistry - An Asian Journal
Volume	17
Issue number	12
DOIs	https://doi.org/10.1002/asia.202200244
Publication status	Published - 2022 Jun 15

Bibliographical note

Funding Information:
This work was supported by a Grant‐in‐Aid for Scientific Research in the Innovative Area “Soft Crystals (No. 2903)” (JSPS KAKENHI grant JP20H04668) from MEXT, Japan. S. A. expresses his gratitude for a JSPS Research Fellowship for Young Scientists (JP18 J22906). The work at Yonsei University was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2021R1 A2 C300630811). We also acknowledge Prof. Takahiro Sasamori (University of Tsukuba) for help with X‐ray diffraction analysis.

Publisher Copyright:
© 2022 Wiley-VCH GmbH.

All Science Journal Classification (ASJC) codes

Biochemistry
Organic Chemistry

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10.1002/asia.202200244

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title = "Protonation-Induced Antiaromaticity in Octaaza[8]circulenes: Cyclooctatetraene Scaffolds Constrained with Four Amidine Moieties",

abstract = "The switching of cyclic π-conjugation pathways using external stimuli is an attractive research topic in the field of organic chemistry. Here, we synthesized C4h-symmetric octaaza[8]circulenes with four peripherally arranged amidine moieties that exhibit enhanced antiaromaticity upon protonation. Titration experiments with methanesulfonic acid revealed the formation of the tetraprotonated forms of the octaaza[8]circulenes in solution. Single-crystal X-ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaaza[8]circulenes is enhanced by the delocalization of charge through the protonation of the pyridine rings.",

author = "Shuhei Akahori and Atsushi Kaga and Jinseok Kim and Hideki Yorimitsu and Dongho Kim and Hiroshi Shinokubo and Yoshihiro Miyake",

note = "Funding Information: This work was supported by a Grant‐in‐Aid for Scientific Research in the Innovative Area “Soft Crystals (No. 2903)” (JSPS KAKENHI grant JP20H04668) from MEXT, Japan. S. A. expresses his gratitude for a JSPS Research Fellowship for Young Scientists (JP18 J22906). The work at Yonsei University was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2021R1 A2 C300630811). We also acknowledge Prof. Takahiro Sasamori (University of Tsukuba) for help with X‐ray diffraction analysis. Publisher Copyright: {\textcopyright} 2022 Wiley-VCH GmbH.",

year = "2022",

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doi = "10.1002/asia.202200244",

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AU - Kim, Jinseok

AU - Yorimitsu, Hideki

AU - Kim, Dongho

AU - Shinokubo, Hiroshi

AU - Miyake, Yoshihiro

N1 - Funding Information: This work was supported by a Grant‐in‐Aid for Scientific Research in the Innovative Area “Soft Crystals (No. 2903)” (JSPS KAKENHI grant JP20H04668) from MEXT, Japan. S. A. expresses his gratitude for a JSPS Research Fellowship for Young Scientists (JP18 J22906). The work at Yonsei University was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2021R1 A2 C300630811). We also acknowledge Prof. Takahiro Sasamori (University of Tsukuba) for help with X‐ray diffraction analysis. Publisher Copyright: © 2022 Wiley-VCH GmbH.

PY - 2022/6/15

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N2 - The switching of cyclic π-conjugation pathways using external stimuli is an attractive research topic in the field of organic chemistry. Here, we synthesized C4h-symmetric octaaza[8]circulenes with four peripherally arranged amidine moieties that exhibit enhanced antiaromaticity upon protonation. Titration experiments with methanesulfonic acid revealed the formation of the tetraprotonated forms of the octaaza[8]circulenes in solution. Single-crystal X-ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaaza[8]circulenes is enhanced by the delocalization of charge through the protonation of the pyridine rings.

AB - The switching of cyclic π-conjugation pathways using external stimuli is an attractive research topic in the field of organic chemistry. Here, we synthesized C4h-symmetric octaaza[8]circulenes with four peripherally arranged amidine moieties that exhibit enhanced antiaromaticity upon protonation. Titration experiments with methanesulfonic acid revealed the formation of the tetraprotonated forms of the octaaza[8]circulenes in solution. Single-crystal X-ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaaza[8]circulenes is enhanced by the delocalization of charge through the protonation of the pyridine rings.

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Protonation-Induced Antiaromaticity in Octaaza[8]circulenes: Cyclooctatetraene Scaffolds Constrained with Four Amidine Moieties

Abstract

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