Jiaobing Wang, Sun Yat-Sen University, Guangzhou, China, and colleagues have used superbenzene units (hexabenzocoronenes, HBCs) to synthesize a helical graphene nanoribbon, which the team calls "supertwistacene". It was synthesized via a polyphenylene intermediate, which was oxidized to form the central polycyclic system and extended at both ends using Sonogashira coupling reactions. Diels–Alder reactions at both ends, followed by a dehydrocyclization, then gave the desired product.

The nanoribbon consists of four linearly fused HBC units, has an overall twist of 117°, and a length of 4.3 nm. Bulky tert-butyl substitutions at the ribbon's edges prevent racemization. Single enantiomers of the nanoribbon were obtained using chiral high-performance liquid chromatography (HPLC). The optically pure compound showed a strong Cotton effect, i.e., a change in circular dichroism around its absorption bands. According to the team, this work could be a basis for further studies of nonplanar polycyclic aromatic hydrocarbons.


Reference:

Supertwistacene: A Helical Graphene Nanoribbon, Shuang Ma, Jiajian Gu, Chaojun Lin, Zhixing Luo, Yanpeng Zhu, Jiaobing Wang, J. Am. Chem. Soc. 2020. https://doi.org/10.1021/jacs.0c08555.

ChemistryViews.org. Posted: September 24, 2020.