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Chiral Cyclic [n]Spirobifluorenylenes: Carbon Nanorings Consisting of Helically Arranged Quaterphenyl Rods Illustrating Partial Units of Woven Patterns

preprint
revised on 29.04.2020, 23:00 and posted on 30.04.2020, 10:36 by Kaige Zhu,, Kosuke Kamochi, Takuya Kodama, Mamoru Tobisu, Toru Amaya
Chiral cyclic [n]spirobifluorenylenes consisting of helically arranged quaterphenyl rods, illustrating partial units of woven patterns, were designed and synthesized as a new family of carbon nanorings. The synthesis was accomplished by the Ni(0)-mediated Yamamoto-coupling of chiral spirobifluorene building blocks. The structures of the cyclic 3-, 4-, and 5-mers were determined by X-ray crystallographic analysis. These carbon nanorings exhibited a strong violet colored emission with high quantum yields in solution (95%, 93%, and 94% for 3-, 4-, and 5-mer, respectively). Other spectroscopic properties, including their chiroptical properties, were also investigated. The g-values for circularly polarized luminescence were found to be in the order of 10-3, where that of the 4-mer showed a relatively higher value 8.5 x 10-3. Characteristic spiroconjugation induced by multiple
3) bifluorenyl units, for example the even-odd effect of the number of units in the matching of the sign of the orbitals, were also indicated by DFT calculations.

Funding

JSPS KAKENHI (17K05782 and 20H02724)

History

Email Address of Submitting Author

amaya@chem.eng.osaka-u.ac.jp

Institution

Graduate School of Engineering, Osaka University

Country

Japan

ORCID For Submitting Author

0000-0002-7716-0630

Declaration of Conflict of Interest

no conflict of interest

Version Notes

Version 02

Licence

Exports