Conformational Control of Chemical Reactivity for Surface‐Confined Ru‐Porphyrins

Abstract

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.O ur systematic real-space visualisation and manipulation experiments with scanning tunnelling microscopyd irectly probe the ligation, while bond-resolving atomic force microscopya nd X-ray standing-wave measurements characterise the geometry,X-ray and ultraviolet photoelectron spectroscopyt he electronic structure,a nd temperature-programmed desorption the binding strength. Density-functional-theory calculations provide additional insight into the functional interface.W eu nambiguously demonstrate that the substituents regulate the interfacial conformational adaptability,e ither promoting or obstructing the uptake of axial CO adducts.

N‐Heterocyclic Carbenes: Molecular Porters of Surface Mounted Ru‐Porphyrins

“…It is therefore reasonable to assign this component to IMe desorption from the transported Ru‐TPP molecules and to the reintegration of those Ru‐TPP molecules back into the compressed phase. This is in good accord with the stronger binding of ligands to the Ru‐TPP adlayer vs. to Ru‐TPP in direct contact with Ag(111) observed experimentally for CO [14e] . Indeed, DFT calculations find an energy difference of 1.05 eV between the bond strength of IMe to the isolated Ru‐TPP molecule vs. to Ru‐TPP adsorbed on Ag(111).…”

“…The trans ‐effect is documented upon ligation of several inorganic molecules on metalloporphyrins and phthalocyanines. In particular, a substantial structural trans ‐effect is observed on the Ru‐TPP/Ag(111) upon CO ligation: the Ru atoms are displaced 0.6 Å further away from the Ag interface, while they remain very close to their initial adsorption sites [14e] . In contrast, the strong registry on Ag(111) hollow sites is not found after IMe ligation in the DFT optimised geometries (Figure S4).…”

“…In contrast, the strong registry on Ag(111) hollow sites is not found after IMe ligation in the DFT optimised geometries (Figure S4). And, importantly, it is notable that such a porter effect cannot be observed on the corresponding LEED experiment when CO replaces IMe (Figure S11), in an experiment albeit performed at a 100 K lower temperature required by the lower desorption energy of CO [14e] …”

N‐Heterocyclic Carbenes: Molecular Porters of Surface Mounted Ru‐Porphyrins

“…In particular, a substantial structural trans ‐effect is observed on the Ru‐TPP/Ag(111) upon CO ligation: the Ru atoms are displaced 0.6 Å further away from the Ag interface, while they remain very close to their initial adsorption sites. [14e] In contrast, the strong registry on Ag(111) hollow sites is not found after IMe ligation in the DFT optimised geometries (Figure S4). And, importantly, it is notable that such a porter effect cannot be observed on the corresponding LEED experiment when CO replaces IMe (Figure S11), in an experiment albeit performed at a 100 K lower temperature required by the lower desorption energy of CO. [14e] …”

Distortion-driven spin switching in electron-doped metal porphyrins

“…21 Interestingly, it has been recently demonstrated that ruthenium tetraphenylporphyrin (RuTPP) on Ag(111) can be stabilized in two different conformations, saddle-shaped and planar, and only the former may axially interact with CO as a consequence of its greater molecular flexibility. 22 As such, the role played by the molecular flexibility in prompting the electronic and magnetic properties of TMTPP after electron doping is an essential aspect whose potential applications are not yet sufficiently investigated.…”