Co(III), Co(II), Co(I): Tuning Single Cobalt Metal Atom Oxidation States in a 2D Coordination Network

Abstract

AbstractIt is shown that the self‐assembly of a surface‐confined metal–organic network such as cobalt porphyrins on graphene is accompanied by the evolution of coordination‐dependent observables in the electronic structure: variation of the layer's valence states within almost 1 eV range and of the metal atoms oxidation states. Coordination of cobalt porphyrins, driven by Co ad‐atoms, allows the synthesis of single metal atom centers with +3, +2, or +1 oxidation states. The electronic structure is determined by lateral interactions extending up to a few nanometers, beyond nearest‐neighbor distances. The reactivity of the single Co sites, which is strongly dependent on the local electronic configuration and, thus, on the metal‐specific oxidation state, is probed by carbon monoxide, which is found to ligate at pyridinic Co(I) at room temperature for background pressures above a fraction of a mbar.