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 (C_n, up to C₂₆) via delicately designed precursors. However, for 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. 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.