On‐Surface Synthesis of Giant Conjugated Macrocycles

We have achieved an on‐surface synthesis of giant conjugated macrocycles having a diameter of ≈7 nm and consisting of up to 30 subunits. The synthesis started with a debrominative coupling of the molecular precursors on a hot Ag(111) surface, leading to the formation of arched oligomeric chains and macrocycles. These products were revealed by scanning tunneling microscopy in combination with density functional theory to be covalent oligomers. These intermediates also display C–Ag organometallic bonds between parallel molecular subunits due to site‐selective debromination and the asymmetric molecular conformation. Subsequent cyclodehydrogenation at higher temperatures steered the final conjugation of the macrocycles. Our findings provide a novel design strategy toward π‐conjugated macrocycles and open up new opportunities for the precise synthesis of organic nanostructures. Giant conjugated macrocycles with a diameter of roughly 7 nm consisting of up to 30 subunits were synthesized on a Ag(111) surface in a two‐step reaction. Site‐selective debromination initiated the synthesis, resulting in arched covalent oligomers and macrocycles, which were assisted by C–Ag organometallic bonds between parallel molecular subunits. The subsequent cyclodehydrogenation steered the final conjugation of the macrocycles.