The structure-selective precise synthesis of carbon nanotubes (CNTs) has been long sought in materials science. The aromatic molecules corresponding to segment structures of CNTs, that is, carbon nanobelts (CNBs), are of interest as templates for CNT growth. Among the three types of CNB (armchair, chiral and zigzag CNBs), zigzag CNBs have been considered the most difficult type to synthesize. Here we report the synthesis, isolation and structural characterization of a zigzag CNB. The synthesis involves an iterative Diels–Alder reaction sequence followed by reductive aromatization of oxygen-bridged moieties. As predicted by theoretical calculations, this CNB was isolated as a stable compound. The structure of the zigzag CNB was fully characterized by X-ray crystallography and its wide energy gap with blue fluorescence properties was revealed by photophysical measurements. With synthetic strategies towards all three types of CNB in hand, the road to the precise synthesis of CNTs can now proceed to the next stage.
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Materials and methods, experimental procedures, photophysical studies and NMR spectra are available in the Supplementary Information. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition number CCDC 1992947 (1). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/. Source data are provided with this paper.
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This work was supported by JST ERATO grant number JPMJER1302 (K.I.), JSPS KAKENHI grant numbers 19H05463 (K.I.), JP16K05771 (Y.S.), JP19H02701 (Y.S.), JP19K22183 (Y.S.) and the Murata Science Foundation (Y.S.). K.Y.C. acknowledges the Croucher Foundation Fellowship programme. K.W. acknowledges the Special Inter-University Researcher programme of the Institute for Molecular Science. We thank R. Okude and H. Shudo for assistance with the measurements, V. Gandikota, K. Matsui and K. Okada for pioneering synthetic attempts and I. A. Stepek for fruitful comments. Mass spectrometry was supported by the Toray Research Center. Calculations were performed using the resources of the Research Center for Computational Science, Okazaki, Japan. The Institute of Transformative Bio-Molecules (ITbM) is supported by the World Premier International Research Center Initiative (WPI), Japan.
The authors declare no competing interests.
Peer review information Nature Chemistry thanks Birgit Esser, Ramesh Jasti and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Supplementary Figs. 1–26, discussion and Tables 1 and 2.
Cartesian coordinates (XYZ files) of optimized structures.
Source data in Microsoft Excel format for Supplementary Figs. 4 and 10a,b.
Raw NMR data.
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Cheung, K.Y., Watanabe, K., Segawa, Y. et al. Synthesis of a zigzag carbon nanobelt. Nat. Chem. (2021). https://doi.org/10.1038/s41557-020-00627-5