On-surface synthesis of an odd-number cyclo[13]carbon

A collaboration between Oxford Chemistry and IBM Research Europe – Zurich has achieved the synthesis and characterisation of the first odd-numbered cyclocarbon, C₁₃. The study is published this week in Science.

Left: Reaction used to synthesise cyclo[13]carbon. Right: AFM images of molecules of cyclo[13]carbon adsorbed on NaCl. (From Science article.)

• Cyclo[13]carbon was synthesised from decachlorofluorene (C₁₃Cl₁₀) on a NaCl monolayer, deposited on a gold Au(111) substrate, at 5 K.
• The reaction was promoted by applying voltage pulses from the scanning probe tip, and appears to occur via retro-Bergman rearrangement of benzyne intermediates.
• C₁₃ has an open-shell triplet ground state and a delocalised carbene centre.
• Atomic force microscopy (AFM) reveals that molecules of C₁₃ have a kinked geometry, which shows different extents of distortion and carbene localization, depending on the molecular environment.
• Dehalogenation of two proximate precursor molecules was found to generate cyclo[26]carbon, probably via dimerization of C₁₃.

You can read more about this study in Science. https://doi.org/10.1126/science.ado1399