Abstract
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.
Highlights
IntroductionBottom-up engineering of covalent organic nanoarchitectures via on-surface reactions has attracted intense interest in the past decade[1,2,3,4,5,6,7,8]
Bottom-up engineering of covalent organic nanoarchitectures via on-surface reactions has attracted intense interest in the past decade[1,2,3,4,5,6,7,8]. Both the structures and the properties of the conjugated nanostructures could be finely tuned at the single-atom level through the covalent coupling between the molecular precursors
A collection of covalent coupling reactions applied in traditional bulk chemistry such as dehalogenated aryl-aryl coupling and homocoupling of alkanes and alkynes have been revisited
Summary
Bottom-up engineering of covalent organic nanoarchitectures via on-surface reactions has attracted intense interest in the past decade[1,2,3,4,5,6,7,8]. Surface-confined supramolecular coordination chemistry has demonstrated the success of the highly self-recognizable, self-selective metal-organic coordination motifs (e.g., Fe/Cu–N/O bonds) in construction of desired nanostructures with the atomic scale order[42,43,44] Inspired by these remarkable results, use of metal-coordination motifs as the template to control the on-surface reactions has received attention in recent years[39,45,46]. Scanning tunneling microscopy (STM), in combination with density functional theory (DFT) simulations and X-ray photoelectron spectroscopy (XPS), reveal the template effect of Fe-tpy coordination motifs on the selective on-surface covalent coupling. Our approach opens an avenue for the rational design protocol towards novel conjugated nanomaterials, precisely controlled in both structure and chemistry
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