Control over on-surface reaction pathways is crucial but challenging for the precise construction of conjugated nanostructures at the atomic level. Herein we demonstrate a selective on-surface covalent coupling reaction that is templated by metal-organic coordinative bonding, and achieve a porous nitrogen-doped carbon nanoribbon structure. In contrast to the inhomogeneous polymorphic structures resulting from the debrominated aryl-aryl coupling reaction on Au(111), the incorporation of an Fe-terpyridine (tpy) coordination motif into the on-surface reaction controls the molecular conformation, guides the reaction pathway, and finally yields pure organic sexipyridine-p-phenylene nanoribbons. Emergent molecular conformers and reaction products in the reaction pathways are revealed by scanning tunneling microscopy, density functional theory calculations and X-ray photoelectron spectroscopy, demonstrating the template effect of Fe-tpy coordination on the on-surface covalent coupling. Our approach opens an avenue for the rational design and synthesis of functional conjugated nanomaterials with atomic precision.

Fine-tuning of 2D metal–organic nanostructures is realized by alkali–pyridyl coordination.

Scheme 1. The chemical structure of 2,9-dibromo-1,10-Phenanthroline (1) and its reaction pathways (cyclization and polymerization) on Cu(111), towards the formation of macrocycles via intermolecular cis-connections (green) and polymeric chains via trans-connections (red), respectively. ChemPhysChemCommunications

Precise control over on-surface covalent reaction pathways is crucial for engineering organic nanostructures with the single-atom precision. Herein, we demonstrate a step-by-step control of an on-surface cascade covalent reaction based on a successive debromination templated by noncovalent metal− organic coordination motifs. The molecular precursor is predesigned with different reactive sites and functional ligands, allowing for both chemical and structural tuning during on-surface reactions. Through the Fe-terpyridine template effect, we are able to direct the reaction to proceed in a three-step cascade pathway and finally to achieve a porous polyarylene nanoribbon structure. The approach opens new opportunities for construction of on-surface organic nanostructures in a predictable manner.