Properties, Synthesis, and The Road to Future Research of Cyclo[18]carbon 

Written By Matthew Graham

In the last decade, carbon-rich materials have taken center stage in the world of surface and material chemistry, and for good reason. From diamonds to graphene, these versatile materials are known for their unique properties and wide range of uses. But there’s one form of carbon that’s particularly elusive and exciting: Cyclo[18]carbon, a mysterious two-coordinate species that’s been teasing scientists for decades with its potential. Like carbon nanotubes, which have revolutionized everything from electronics to medicine, cyclo-carbons are poised to unlock incredible advancements in technology—and possibly much more.

While the idea of this exotic carbon allotrope has been around for years, it was only recently that researchers led by Kaiser et al. finally cracked the code, isolating and synthesizing Cyclo[18]carbon for the first time. This breakthrough is a major game-changer. With cyclo[18]carbon now in hand, labs worldwide are diving deep into its structure, bonding patterns, electronic properties, and more. Each discovery opens new doors, sparking a wave of research as scientists try to unravel the full potential of this carbon-based marvel.

The quest to understand Cyclo[18]carbon isn’t without controversy. As with any cutting-edge research, each experiment seems to raise new questions while answering old ones. For instance, studies on improving the synthesis process, like debromination of C18Br6 to boost yields, are revealing unexpected details about the molecule’s bonding and geometry. At the same time, researchers are exploring how this unique structure behaves on a quantum level, investigating its potential in quantum mechanical tunneling and molecular electronics.

Beyond the lab, the real excitement comes from the future possibilities of Cyclo[18]carbon. Its unusual properties could be a game-changer in molecular engineering, with researchers already working to stabilize intermediates and find ways to link these carbon rings to create larger, more complex structures. Imagine the possibilities for molecular devices, nanotechnology, or even new materials that could change the way we build and interact with technology.

As Cyclo[18]carbon continues to capture the imagination of chemists, its role in material science is growing. The need for a comprehensive review of the latest research is more critical than ever, not only to catch up those just entering the field but to push the boundaries of what’s possible. This review would provide a full rundown of everything we know so far, from its structural and mechanical properties to potential real-world applications, while also addressing the challenges ahead. One thing’s for sure: Cyclo[18]carbon is just getting started, and the future looks incredibly bright for this tiny but mighty molecule.

References:  

  1. Kaiser, K.; Scriven, L.; Schulz, F.; Gawel, P.; Gross, L.; & Anderson, H. An sp-hybridized molecular carbon allotrope, cyclo[18]carbon. Science. 2019, 365, 1914–1301. https://doi.org/10.1126/science.aay1914 

  2. Scriven, L.; Kaiser, K.; Schulz, F.; Sterling, A.; Woltering, S.; Gawel, P.; Christensen, K.; Anderson, H.; & Gross, L. Synthesis of Cyclo[18]carbon via Debromination of C18Br6. J. Am. Chem. Soc. 2020, 142(30), 12921–12924. https://doi.org/10.1021/jacs.0c05033 

  3. Nandi, A.; Solel, E.; & Kozuch, S. Carbon Tunneling in the Automerization of Cyclo[18]carbon. Chem. Eur. J. 2019, 26(3), 625–628. https://doi.org/10.1002/chem.201904929 

  4. Zhang, L.; Li, H.; Feng, Y.; & Shen, L. Diverse Transport Behaviors in Cyclo[18]carbon-Based Molecular Devices. J. Phys. Chem. Lett. 2020, 11(7), 2611–2617. https://doi.org/10.1021/acs.jpclett.0c00357 

  5. Baryshnikov, G.; Valiev, R.; Kuklin, A.; Sundholm, D.; & Ågren, H. Cyclo[18]carbon: Insight into Electronic Structure, Aromaticity, and Surface Coupling. J. Phys. Chem. Lett. 2019, 10(21), 6701–6705. https://doi.org/10.1021/acs.jpclett.9b02815 

  6. Pereira, Z. S.; & da Silva, E. Z. Spontaneous symmetry breaking in cyclo [18] carbon. J. Phys. Chem. A. 2020, 124(6), 1152-1157. https://doi.org/10.1021/acs.jpca.9b11822  

  7. Xu, S.; Liu, F.; Xu, J.; Cui, Y.; & Wang, C. Theoretical investigation on bond and spectrum of cyclo [18] carbon (C 18) with sp-hybridized. J. Mol. Model. 2020, 26, 1-6. https://doi.org/10.1007/s00894-020-4344-5  

  8. Dai, C.; Chen, D.; & Zhu, J. Achieving Adaptive Aromaticity in Cyclo [10] carbon by Screening Cyclo [n] carbon (n= 8‐24). Chem. Asian J. 2020, 15, 2187-2191. https://doi.org/10.1002/asia.202000528  

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  10. Fang, S.; & Hu, Y. H. Cyclo [18] carbon as an Ultra-Elastic Molecular O-Ring with Unique Mechanical Properties. Carbon. 2020, 171, 96-103. https://doi.org/10.1016/j.carbon.2020.08.082  

  11. Hou, X.; Ren, Y.; Fu, F.; & Tian, X. Doping atom to tune electronic characteristics and adsorption of cyclo [18] carbons: A theoretical study. Comput. Theor. Chem. 2020, 1187, 112922. https://doi.org/10.1016/j.comptc.2020.112922  

  12.  Shi, B.; Yuan, L.; Tang, T.; Yuan, Y.; & Tang, Y. Study on electronic structure and excitation characteristics of cyclo [18] carbon. Chem. Phys. Lett. 2020, 741, 136975. https://doi.org/10.1016/j.cplett.2019.136975  

  13. Pichierri, F. Boron-nitrogen analogues of cyclo [18] carbon. Chem. Phys. Lett. 2020, 738, 136860. https://doi.org/10.1016/j.cplett.2019.136860   

  14. Liu, Z.; Lu, T.; & Chen, Q. Intermolecular interaction characteristics of the all-carboatomic ring, cyclo [18] carbon: Focusing on molecular adsorption and stacking. Carbon. 2020, 171, 514-523. https://doi.org/10.1016/j.carbon.2020.09.048  

  15. Qin, B.; Zhang, Q.; Li, Y.; Yang, G.; Yu, H.; & Peng, F. Mechanistic insights into the electrochemical reduction of CO2 on cyclo [18] carbon using density functional theory calculations. ChemElectroChem. 2020, 7, 1838-1842. https://doi.org/10.1002/celc.202000180  

Matthew Graham
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