On-surface synthesis of cyclo[20]carbon and cyclo[30]carbon from cyclo[10]carbon

On-surface synthesis recently enabled access to generate a series of cyclo[n]carbons (Cn, up to C26) via delicately designed precursors. However, for even larger cyclocarbons, synthesis of the corresponding precursors is being challenged. Here, we report another strategy for synthesizing larger cyclocarbons via the coupling and ring-opening reactions from smaller ones. We chose C10 as the precursor, and induce the coupling and ring-opening reactions via tip manipulation to successfully generate C20 and C30 (the largest one synthesized on the surface so far). Bond-resolved atomic force microscopy imaging unambiguously reveals the polyynic structure of C30, aligning with theoretical prediction. This approach establishes a new pathway to access larger cyclocarbons, and potentially enables controlled polymerization of cyclocarbons.