Cyclo[18]carbon Formation from C 18 Br 6 and C 18 (CO) 6 Precursors.

Although cyclo[18]carbon has been isolated experimentally from two precursors, C 18 Br 6 and C 18 (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 C 18 Br 6 compared to C 18 (CO) 6 , confirming a considerably higher yield of cylco[18]carbon when the C 18 Br 6 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.