title: Depopulation of Single-Phthalocyanine Molecular Orbitals upon Pyrrolic-Hydrogen Abstraction on Graphene.
abstract: Single-molecule chemistry with a scanning tunneling microscope has preponderantly been performed on metal surfaces. The molecule-metal hybridization, however, is often detrimental to genuine molecular properties and obscures their changes upon chemical reactions. We used graphene on Ir(111) to reduce the coupling between Ir(111) and adsorbed phthalocyanine molecules. By local electron injection from the tip of a scanning tunneling microscope the two pyrrolic H atoms were removed from single phthalocyanines. The detachment of the H atom pair induced a strong modification of the molecular electronic structure, albeit with no change in the adsorption geometry. Spectra and maps of the differential conductance combined with density functional calculations unveiled the entire depopulation of the highest occupied molecular orbital upon H abstraction. Occupied π states of intact molecules are proposed to be emptied via intramolecular electron transfer to dangling σ states of H-free N atoms.
authors.affiliation: Institut für Physik, Technische Universität Ilmenau , D-98693 Ilmenau, Germany.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Néel
authors.affiliation: Department of Chemistry, UMR ENS-CNRS-UPMC 8640, Ecole Normale Supérieure , F-75005 Paris, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Lattelais
authors.affiliation: Department of Chemistry, UMR ENS-CNRS-UPMC 8640, Ecole Normale Supérieure , F-75005 Paris, France.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Bocquet
authors.affiliation: Institut für Physik, Technische Universität Ilmenau , D-98693 Ilmenau, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Kröger
keywords: density functional theory; graphene; phthalocyanine; scanning tunneling microscopy; scanning tunneling spectroscopy; single-molecule chemistry