Conformational Control of Chemical Reactivity for Surface-Confined Ru-Porphyrins.

We assess the crucial role of tetrapyrrole flexibility in the CO ligation to distinct Ru-porphyrins supported on an atomistically well-defined Ag(111) substrate. Our systematic real-space visualisation and manipulation experiments with scanning tunnelling microscopy directly probe the ligation, while bond-resolving atomic force microscopy and X-ray standing-wave measurements characterise the geometry, X-ray and ultraviolet photoelectron spectroscopy the electronic structure, and temperature-programmed desorption the binding strength. Density-functional-theory calculations provide additional insight into the functional interface. We unambiguously demonstrate that the substituents regulate the interfacial conformational adaptability, either promoting or obstructing the uptake of axial CO adducts.