Cyclo[18]carbon Formation from C18Br6 and C18(CO)6 Precursors

Rahul Suresh; Glib V Baryshnikov; Artem V Kuklin; Diana I Nemkova; Svetlana V Saikova; Hans Ågren

doi:10.1021/acs.jpclett.2c02659

Cyclo[18]carbon Formation from C₁₈Br₆ and C₁₈(CO)₆ Precursors

J Phys Chem Lett. 2022 Nov 10;13(44):10318-10325. doi: 10.1021/acs.jpclett.2c02659. Epub 2022 Oct 28.

Authors

Rahul Suresh¹, Glib V Baryshnikov², Artem V Kuklin³, Diana I Nemkova^{1

4}, Svetlana V Saikova⁴, Hans Ågren³

Affiliations

¹ International Research Center of Spectroscopy and Quantum Chemistry - IRC SQC, Siberian Federal University, 79 Svobodny pr., 660041Krasnoyarsk, Russia.
² Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, 60174Norrköping, Sweden.
³ Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20Uppsala, Sweden.
⁴ Division of Physical and Inorganic Chemistry, Institute of Non-ferrous Metals, Siberian Federal University, 79 Svobodny pr., 660041Krasnoyarsk, Russia.

Abstract

Although cyclo[18]carbon has been isolated experimentally from two precursors, C₁₈Br₆ and C₁₈(CO)₆, no reaction mechanisms have yet been explored. Herein, we provide insight into the mechanism behind debromination and decarbonylation. Both neutral precursors demonstrate high activation barriers of ∼2.3 eV, while the application of an electric field can lower the barriers by 0.1-0.2 eV. The barrier energy of the anion-radicals is found to be significantly lower for C₁₈Br₆ compared to C₁₈(CO)₆, confirming a considerably higher yield of cylco[18]carbon when the C₁₈Br₆ precursor is used. Elongation of the C-Br bond in the anion-radical confirms its predissociation condition. Natural bonding orbital analysis shows that the stability of C-Br and C-CO bonds in the anion-radicals is lower compared to their neutral species, indicating a possible higher yield. The applied analysis provides crucial details regarding the reaction yield of cyclo[18]carbon and can serve as a general scheme for tuning reaction conditions for other organic precursors.