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Synthesis of monolayer and persistent bilayer graphene fragments by using a radical-mediated coupling approach

Nature Synthesis volume 2, pages 1104–1115 (2023)Cite this article

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Abstract

Atomically precise single-layer graphene fragments show size- and edge-dependent electronic properties and are promising materials for electronics, photonics and spintronics. However, their synthesis has been limited to a few types of reactions. In addition, bilayer graphene fragments can exhibit intriguing properties originating from interlayer electronic interactions, but attaining a stable bilayer structure remains challenging. Here we report a synthetic strategy to prepare large-size single-layer graphene fragments by using intramolecular radical-mediated coupling reactions. One of the obtained open-shell graphene fragments demonstrates a closely stacked bilayer structure in solid state via strong intermolecular radical–radical interaction, which can be classified as delocalized ‘32-centre-2-electron’ pancake bonding. The bilayer structure is persistent in solution and dissociates only at highly oxidized states. The electronic properties of the graphene fragments were investigated. This study provides an intramolecular/intermolecular radical-mediated/radical–radical coupling approach towards diverse single-layer, bilayer and possibly multilayer graphene fragments with tunable properties.

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Fig. 1: Representative open-shell π-extended radicals and the strategy for mono-/bilayer graphene fragments by using a radical-mediated coupling approach.
Fig. 2: Synthesis of OR-2 and studies demonstrating the radical–radical coupling mechanism.
Fig. 3: Synthesis of the OR-3 and OR-4.
Fig. 4: Single-crystal structures of OR-2 and OR-3, and theoretical study revealing the 32-centre-2-electron pancake bond nature of the radical π-dimer of OR-3.
Fig. 5: Solution-phase experimental studies revealing the diradical character, redox property and dissociation behaviour of the [OR-3]2.
Fig. 6: Electronic, optic, redox properties and aromaticity of OR-2 and OR-4.

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Data availability

The data that support the findings of this study are available in Supplementary Information. Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2220240 (dtbp-OR-2) and 2220242 (tips-OR-3). 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.

References

  1. Enoki, T., Kobayashi, Y. & Fukui, K.-I. Electronic structures of graphene edges and nanographene. Int. Rev. Phys. Chem. 26, 609–645 (2007).

    Article  CAS  Google Scholar 

  2. Morita, Y., Suzuki, S., Sato, K. & Takui, T. Synthetic organic spin chemistry for structurally well-defined open-shell graphene fragments. Nat. Chem. 3, 197–204 (2011).

    Article  CAS  PubMed  Google Scholar 

  3. Fujii, S. & Enoki, T. Nanographene and graphene edges: electronic structure and nanofabrication. Acc. Chem. Res. 46, 2202–2210 (2013).

    Article  CAS  PubMed  Google Scholar 

  4. Yano, Y., Mitoma, N., Ito, H. & Itami, K. A quest for structurally uniform graphene nanoribbons: synthesis, properties, and applications. J. Org. Chem. 85, 4–33 (2020).

    Article  CAS  PubMed  Google Scholar 

  5. Zeng, W. & Wu, J. Open-shell graphene fragments. Chem 7, 358–386 (2021).

    Article  CAS  Google Scholar 

  6. Gu, Y., Qiu, Z. & Müllen, K. Nanographenes and graphene nanoribbons as multitalents of present and future materials science. J. Am. Chem. Soc. 144, 11499–11524 (2022).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. Wu, J., Pisula, W. & Müllen, K. Graphenes as potential material for electronics. Chem. Rev. 107, 718–747 (2007).

    Article  CAS  PubMed  Google Scholar 

  8. Jiang, W., Li, Y. & Wang, Z. Tailor-made rylene arrays for high performance n-channel semiconductors. Acc. Chem. Res. 47, 3135–3147 (2014).

    Article  CAS  PubMed  Google Scholar 

  9. Bonal, V. et al. Solution-processed nanographene distributed feedback lasers. Nat. Commun. 10, 3327 (2019).

    Article  PubMed  PubMed Central  Google Scholar 

  10. Liu, Z. et al. Solution-processed graphene–nanographene van der Waals heterostructures for photodetectors with efficient and ultralong charge separation. J. Am. Chem. Soc. 143, 17109–17116 (2021).

    Article  CAS  PubMed  Google Scholar 

  11. Mishra, S. et al. Topological frustration induces unconventional magnetism in a nanographene. Nat. Nanotechnol. 15, 22–28 (2020).

    Article  CAS  PubMed  Google Scholar 

  12. Mishra, S. et al. Large magnetic exchange coupling in rhombus-shaped nanographenes with zigzag periphery. Nat. Chem. 13, 581–586 (2021).

    Article  CAS  PubMed  Google Scholar 

  13. Lombardi, F. et al. Quantum units from the topological engineering of molecular graphenoids. Science 366, 1107–1110 (2019).

    Article  CAS  PubMed  Google Scholar 

  14. Wang, H. et al. Graphene nanoribbons for quantum electronics. Nat. Rev. Phys. 3, 791–802 (2021).

    Article  CAS  Google Scholar 

  15. Gu, Y., Wu, X., Gopalakrishna, T. Y., Phan, H. & Wu, J. Graphene-like molecules with four zigzag edges. Angew. Chem. Int. Ed. 57, 6541–6545 (2018).

    Article  CAS  Google Scholar 

  16. Gu, Y. et al. peri-Acenoacenes. Chem. Commun. 55, 5567–5570 (2019).

    Article  CAS  Google Scholar 

  17. Grzybowski, M., Skonieczny, K., Butenschön, H. & Gryko, D. T. Comparison of oxidative aromatic coupling and the scholl reaction. Angew. Chem. Int. Ed. 52, 9900–9930 (2013).

    Article  CAS  Google Scholar 

  18. Jassas, R. S. et al. Scholl reaction as a powerful tool for the synthesis of nanographenes: a systematic review. RSC Adv. 11, 32158–32202 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Marshall, J. L., Lehnherr, D., Lindner, B. D. & Tykwinski, R. R. Reductive aromatization/dearomatization and elimination reactions to access conjugated polycyclic hydrocarbons, heteroacenes, and cumulenes. ChemPlusChem 82, 967–1001 (2017).

    Article  CAS  PubMed  Google Scholar 

  20. Narita, A., Wang, X.-Y., Feng, X. & Müllen, K. New advances in nanographene chemistry. Chem. Soc. Rev. 44, 6616–6643 (2015).

    Article  CAS  PubMed  Google Scholar 

  21. Ohta, T., Bostwick, A., Seyller, T., Horn, K. & Rotenberg, E. Controlling the electronic structure of bilayer graphene. Science 313, 951–954 (2006).

    Article  CAS  PubMed  Google Scholar 

  22. Zhang, Y. et al. Direct observation of a widely tunable bandgap in bilayer graphene. Nature 459, 820–823 (2009).

    Article  CAS  PubMed  Google Scholar 

  23. Wu, J. et al. Controlled self-assembly of hexa-peri-hexabenzocoronenes in solution. J. Am. Chem. Soc. 126, 11311–11321 (2004).

    Article  CAS  PubMed  Google Scholar 

  24. Feng, X., Pisula, W. & Müllen, K. From helical to staggered stacking of zigzag nanographenes. J. Am. Chem. Soc. 129, 14116–14117 (2007).

    Article  CAS  PubMed  Google Scholar 

  25. Zhao, X.-J. et al. Molecular bilayer graphene. Nat. Commun. 10, 3057 (2019).

    Article  PubMed  PubMed Central  Google Scholar 

  26. Mahl, M., Niyas, M. A., Shoyama, K. & Würthner, F. Multilayer stacks of polycyclic aromatic hydrocarbons. Nat. Chem. 14, 457–462 (2022).

    Article  CAS  PubMed  Google Scholar 

  27. Pigulski, B., Shoyama, K., Sun, M.-J. & Würthner, F. Fluorescence enhancement by supramolecular sequestration of a C54-nanographene trisimide by hexabenzocoronene. J. Am. Chem. Soc. 144, 5718–5722 (2022).

    Article  CAS  PubMed  Google Scholar 

  28. Sogo, P. B., Nakazaki, M. & Calvin, M. Free radical from perinaphthene. J. Chem. Phys. 26, 1343–1345 (1957).

    Article  CAS  Google Scholar 

  29. Goto, K. et al. A stable neutral hydrocarbon radical: synthesis, crystal structure, and physical properties of 2,5,8-tri-tert-butyl-phenalenyl. J. Am. Chem. Soc. 121, 1619–1620 (1999).

    Article  CAS  Google Scholar 

  30. Xiang, Q. et al. Stable olympicenyl radicals and their π-dimers. J. Am. Chem. Soc. 142, 11022–11031 (2020).

    Article  CAS  PubMed  Google Scholar 

  31. Arikawa, S., Shimizu, A., Shiomi, D., Sato, K. & Shintani, R. Synthesis and isolation of a kinetically stabilized crystalline triangulene. J. Am. Chem. Soc. 143, 19599–19605 (2021).

    Article  CAS  PubMed  Google Scholar 

  32. Xiang, Q. & Sun, Z. Doublet open-shell graphene fragments. Chem. Asian J. 17, e202200251 (2022).

    Article  CAS  PubMed  Google Scholar 

  33. Zaitsev, V., Rosokha, S. V., Head-Gordon, M. & Kochi, J. K. Steric modulations in the reversible dimerizations of phenalenyl radicals via unusually weak carbon-centered π- and σ-bonds. J. Org. Chem. 71, 520–526 (2006).

    Article  CAS  PubMed  Google Scholar 

  34. Mou, Z., Uchida, K., Kubo, T. & Kertesz, M. Evidence of σ- and π-dimerization in a series of phenalenyls. J. Am. Chem. Soc. 136, 18009–18022 (2014).

    Article  CAS  PubMed  Google Scholar 

  35. Uchida, K., Mou, Z., Kertesz, M. & Kubo, T. Fluxional σ-bonds of the 2,5,8-trimethylphenalenyl dimer: direct observation of the sixfold σ-bond shift via a π-dimer. J. Am. Chem. Soc. 138, 4665–4672 (2016).

    Article  CAS  PubMed  Google Scholar 

  36. Inoue, J. et al. The first detection of a Clar’s hydrocarbon, 2,6,10-tri-tert-butyltriangulene: a ground-state triplet of non-Kekulé polynuclear benzenoid hydrocarbon. J. Am. Chem. Soc. 123, 12702–12703 (2001).

    Article  CAS  PubMed  Google Scholar 

  37. Xiang, Q. et al. Unveiling the hidden σ-dimerization of a kinetically protected olympicenyl radical. Chem. Eur. J. 27, 8203–8213 (2021).

    Article  CAS  PubMed  Google Scholar 

  38. Small, D. et al. Intermolecular π-to-π bonding between stacked aromatic dyads. Experimental and theoretical binding energies and near-IR optical transitions for phenalenyl radical/radical versus radical/cation dimerizations. J. Am. Chem. Soc. 126, 13850–13858 (2004).

    Article  CAS  PubMed  Google Scholar 

  39. Suzuki, S. et al. Aromaticity on the pancake-bonded dimer of neutral phenalenyl radical as studied by MS and NMR spectroscopies and NICS analysis. J. Am. Chem. Soc. 128, 2530–2531 (2006).

    Article  CAS  PubMed  Google Scholar 

  40. Reid, D. H. Stable π-electron systems and new aromatic structures. Tetrahedron 3, 339–352 (1958).

    Article  CAS  Google Scholar 

  41. Uchida, K., Ito, S., Nakano, M., Abe, M. & Kubo, T. Biphenalenylidene: isolation and characterization of the reactive intermediate on the decomposition pathway of phenalenyl radical. J. Am. Chem. Soc. 138, 2399–2410 (2016).

    Article  CAS  PubMed  Google Scholar 

  42. Zhang, X., Li, J., Qu, H., Chi, C. & Wu, J. Fused bispentacenequinone and its unexpected michael addition. Org. Lett. 12, 3946–3949 (2010).

    Article  CAS  PubMed  Google Scholar 

  43. Ribar, P., Valenta, L., Šolomek, T. & Juríček, M. Rules of nucleophilic additions to zigzag nanographene diones. Angew. Chem. Int. Ed. 60, 13521–13528 (2021).

    Article  CAS  Google Scholar 

  44. Hoffmann, R. & Woodward, R. B. Conservation of orbital symmetry. Acc. Chem. Res. 1, 17–22 (1968).

    Article  CAS  Google Scholar 

  45. Woodward, R. B. & Hoffmann, R. The conservation of orbital symmetry. Angew. Chem. Int. Ed. Engl. 8, 781–853 (1969).

    Article  CAS  Google Scholar 

  46. Steiner, R. P. & Michl, J. pi.,.pi.-Biradicaloid hydrocarbons. The pleiadene family. 3. A facile symmetry-forbidden thermal conversion of a polycyclic butadiene moiety to a cyclobutene. J. Am. Chem. Soc. 100, 6413–6415 (1978).

    Article  CAS  Google Scholar 

  47. Ravat, P. et al. Cethrene: A helically chiral biradicaloid isomer of heptazethrene. Angew. Chem. Int. Ed. 55, 1183–1186 (2016).

    Article  CAS  Google Scholar 

  48. Šolomek, T., Ravat, P., Mou, Z., Kertesz, M. & Juríček, M. Cethrene: the chameleon of Woodward–Hoffmann rules. J. Org. Chem. 83, 4769–4774 (2018).

    Article  PubMed  Google Scholar 

  49. Ravat, P., Šolomek, T., Häussinger, D., Blacque, O. & Juríček, M. Dimethylcethrene: a chiroptical diradicaloid photoswitch. J. Am. Chem. Soc. 140, 10839–10847 (2018).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  50. Kertesz, M. Pancake bonding: an unusual pi-stacking interaction. Chem. Eur. J. 25, 400–416 (2019).

    Article  CAS  PubMed  Google Scholar 

  51. Zeng, Z. et al. Pro-aromatic and anti-aromatic π-conjugated molecules: an irresistible wish to be diradicals. Chem. Soc. Rev. 44, 6578–6596 (2015).

    Article  CAS  PubMed  Google Scholar 

  52. Kubo, T. Recent progress in quinoidal singlet biradical molecules. Chem. Lett. 44, 111–122 (2014).

    Article  Google Scholar 

  53. Y. Gopalakrishna, T., Zeng, W., Lu, X. & Wu, J. From open-shell singlet diradicaloids to polyradicaloids. Chem. Commun. 54, 2186–2199 (2018).

    Article  CAS  Google Scholar 

  54. Wu, J. Diradicaloids (Jenny Stanford Publishing, 2022).

  55. Bleaney, B. & Bowers, K. D. Anomalous paramagnetism of copper acetate. Proc. R. Soc.Lond. Ser. A 214, 451–465 (1952).

    Article  CAS  Google Scholar 

  56. Klod, S. & Kleinpeter, E. Ab initio calculation of the anisotropy effect of multiple bonds and the ring current effect of arenes—application in conformational and configurational analysis. J. Chem. Soc. Perkin Transact. 2, 1893–1898 (2001).

    Google Scholar 

  57. Schleyer, P. V. R., Maerker, C., Dransfeld, A., Jiao, H. & van Eikema Hommes, N. J. R. Nucleus-independent chemical shifts: a simple and efficient aromaticity probe. J. Am. Chem. Soc. 118, 6317–6318 (1996).

    Article  CAS  PubMed  Google Scholar 

  58. Kruszewski, J. & Krygowski, T. M. Definition of aromaticity basing on the harmonic oscillator model. Tetrahedron Lett. 13, 3839–3842 (1972).

    Article  Google Scholar 

  59. Geuenich, D., Hess, K., Köhler, F. & Herges, R. Anisotropy of the induced current density (ACID), a general method to quantify and visualize electronic delocalization. Chem. Rev. 105, 3758–3772 (2005).

    Article  CAS  PubMed  Google Scholar 

  60. zum Bezolproblem, Q. B. & zum Problem, Q. B. Quantentheoretische Beiträge zum Benzolproblem. Z. Phys. Chem. 70, 204–286 (1931).

    Google Scholar 

  61. Sondheimer, F. Annulenes. Acc. Chem. Res. 5, 81–91 (1972).

    Article  CAS  Google Scholar 

  62. Spitler, E. L., Johnson, C. A. & Haley, M. M. Renaissance of annulene chemistry. Chem. Rev. 106, 5344–5386 (2006).

    Article  CAS  PubMed  Google Scholar 

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Acknowledgements

J.W. acknowledges the financial support from A*STAR AME IRG grant (A20E5c0089) and NRF Investigatorship award (NRF-NRFI05-2019-0005). Z.S. thanks the financial support from National Natural Science Foundation of China (21971187), Natural Science Foundation of Tianjin (19JCJQJC62700) and the Haihe Laboratory of Sustainable Chemical Transformations.

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Authors and Affiliations

  1. Department of Chemistry, National University of Singapore, Singapore, Singapore

    Tianyu Jiao, Yong Ni, Tingting Xu, Xudong Hou, Shaofei Wu, Longbin Ren, Yanwei Gu & Jishan Wu

  2. Instrumentation and Service Center for Physical Sciences, Westlake University, Hangzhou, China

    Xiaohe Miao

  3. Institute of Molecular Plus, Department of Chemistry, Tianjin University and Haihe Laboratory of Sustainable Chemical Transformations, Tianjin, China

    Zhe Sun

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Contributions

T.J., Z.S. and J.W. conceived the project, designed the research and prepared the manuscript. T.J. carried out experiments and analysed the data. Z.S. and J.W. supervised the project. X.H., S.W. and X.M. contributed to X-ray crystallographic analyses. T.X. contributed to ESR measurements. L.R. contributed to oxidation titration analyses. Y.G. contributed to theoretical calculation of aromaticity. Y.N. discussed and commented on the manuscript.

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Correspondence to Zhe Sun or Jishan Wu.

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Nature Synthesis thanks Wei Zhang, Andrey Turchanin and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary handling editor: Alison Stoddart, in collaboration with the Nature Synthesis team.

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Supplementary information

Supplementary Information

General methods, Supplementary Figs. 1–109, Tables 1–14 and Cartesian coordinates for the optimized structures.

Supplementary Data 1

Crystal data for dtbp-OR-2, CCDC 2220240.

Supplementary Data 2

Crystal data for tips-OR-3, CCDC 2220242.

Source data

Source Data Fig. 5

VT ESR data.

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Jiao, T., Ni, Y., Xu, T. et al. Synthesis of monolayer and persistent bilayer graphene fragments by using a radical-mediated coupling approach. Nat. Synth 2, 1104–1115 (2023). https://doi.org/10.1038/s44160-023-00348-w

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