Carbon‐Carbon Coupling on Inert Surfaces by Deposition of en Route Generated Aryl Radicals

On-surface synthesis of exceptionally stable and p-conjugated carbon-carbon (C-C) bonded nanostructures requires metal surfaces. Albeit beneficial for characterization, metal surfaces are detrimental for electronic applications. To also facilitate C-C coupling on inert surfaces, we devised a radical deposition source (RDS) for the direct deposition of aryl radicals onto arbitrary substrates. Its core piece is a heated reactive drift tube through which halogenated precursors are deposited and en route converted into radicals. For the proof-of-concept we study 4,4''-diiodo- p -terphenyl (DITP) precursors on iodine-passivated metal surfaces. Deposition with the RDS at room temperature results in highly regular structures comprised of mostly monomeric (terphenyl) or dimeric (sexiphenyl) biradicals. Mild heating activates progressive C-C coupling into more extended molecular wires. These structures are distinctly different from the self-assemblies observed upon conventional deposition of intact DITP. Direct deposition of radicals renders substrate reactivity unnecessary, thereby paving the road for synthesis on application relevant inert.