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Radical cyclization is among the most powerful and versatile reactions for constructing mono- and polycyclic systems, but has, to date, remained unexplored in the context of on-surface synthesis. We report the controlled on-surface synthesis of stable corrole radicals on Ag(111) via site-specific dehydrogenation of a pyrrole N-H bond in the 5,10,15-tris(pentafluoro-phenyl)-corrole triggered by annealing at 330 K under ultrahigh-vacuum conditions. We reveal a thermally induced regioselective cyclization reaction mediated by a radical cascade and resolve the reaction mechanism of the pertaining cyclodefluorination reaction at the single-molecule level. Via intramolecularly resolved probing of the radical-related Kondo signature, we achieve real space visualization of the distribution of the unpaired electron density over specific sites within the corrole radical. Annealing to 550 K initiates intermolecular coupling reactions, producing an extended π-conjugated corrole system.

Supporting functional molecules on crystal facets is an established technique in nanotechnology. To preserve the original activity of ionic metallorganic agents on a supporting template, conservation of the charge and oxidation state of the active center is indispensable. We present a model system of a metallorganic agent that, indeed, fulfills this design criterion on a technologically relevant metal support with potential impact on Au(III)-porphyrin-functionalized nanoparticles for an improved anticancer-drug delivery. Employing scanning tunneling microscopy and -spectroscopy in combination with photoemission spectroscopy, we clarify at the single-molecule level the underlying mechanisms of this exceptional adsorption mode. It is based on the balance between a high-energy oxidation state and an electrostatic screening-response of the surface (image charge). Modeling with first principles methods reveals submolecular details of the metal-ligand bonding interaction and completes the study by providing an illustrative electrostatic model relevant for ionic metalorganic agent molecules, in general.