Adsorption and charge transfer interactions of bi-isonicotinic acid on Ag(111)

Abstract

The adsorption and charge transfer dynamics of the organic molecule bi-isonicotinic acid (4,4-dicarboxy-2,2-bipyridine) on single crystal Ag(111) has been studied using synchrotron radiation-based photoemission, x-ray absorption and resonant core spectroscopies. Measurements for multilayer and monolayer coverage are used to determine the nature of the molecule-surface interactions and the molecular orientation. An experimental density of states for the monolayer with respect to the underlying metal surface is obtained by combining x-ray absorption spectroscopy at the N 1s edge and valence photoemission to measure the unoccupied and occupied valence states, respectively. This shows that the lowest unoccupied molecular orbital in the core-excited state lies energetically below the Fermi level of the surface allowing charge transfer from the metal into this orbital. Resonant photoelectron spectroscopy was used to probe this charge transfer in the context of super-spectator and super-Auger electron transitions. The results presented provide a novel interpretation of resonant core-level spectroscopy to explore ultra-fast charge transfer between an adsorbed organic molecule and a metal surface through the observation of electrons from the metal surface playing a direct role in the core-hole decay of the core-excited molecule.

Site-Selective Orbital Interactions in an Ultrathin Iron-Carbene Photosensitizer Film

“…The RPES line profiles show coupling of these NEXAFS features with the first three distinct occupied MO features at binding energies 3.6 eV, 6.0 eV, and 7.5 eV, which are enhanced in the maps via participant decay. 26,27 The first 3.6 eV feature shows strong enhancement/ coupling with the N a atom and little coupling with the N b /N c atoms. The feature at 6.0 eV BE is equally enhanced on excitation into either nitrogen environment.…”

Solution-Based Self-Assembly and Stability of Ruthenium(II) Tris-bipyridyl Monolayers on Gold

“…When aiming for the characterization of headgroup/substrate interactions, X-ray photoelectron spectroscopy (XPS) with its high surface sensitivity and the ability to reveal oxidation states of chemical elements has been proven to provide key insights into the nature of the molecule/substrate bonds. − While the binding of Ru­(II) polypyridyl complexes through carboxylic headgroups on semiconductor surfaces is well established, − only one study reports the assembly by physical vapor deposition (PVD) of carboxyl-functionalized Ru­(II) complexes on gold substrates . Here, the binding was shown to occur via the thiocyanate ligands present at the Ru­(II) centers.…”

Formation of diphenyl-bipyridine units by surface assisted cross coupling in Pd-cyclometalled complexes

“…components at 398.6 eV and 399.3 eV. Both species are suitable for N atoms in the pyridinic ring but have a slightly different interaction with the Ag substrate [35] The high energy component is similar to the one observed for bi-isonicotinic acid on Ag(1 1 1) and identified with nitrogen atoms weakly interacting with the substrate [36]. Viceversa, the 398.6 eV line is compatible with the signal measured for N-doped graphene on Ni(1 1 1) [37] and, as already suggested in ref.…”