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 octaazacirculenes 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 octaazacirculenes in solution. Single-crystal X-ray diffraction analyses and theoretical calculations indicated that the contribution of the 8π antiaromatic character of the octaazacirculenes is enhanced by the delocalization of charge through the protonation of the pyridine rings.
|Journal||Chemistry - An Asian Journal|
|Publication status||Published - 2022 Jun 15|
Bibliographical noteFunding 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.
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All Science Journal Classification (ASJC) codes
- Organic Chemistry