title: Surface cis Effect: Influence of an Axial Ligand on Molecular Self-Assembly.
abstract: Adding ligands to molecules can have drastic and unforeseen consequences in the final products of a reaction. Recently a surface trans effect due to the weakening of a molecule-surface bond was reported. Here, we show a surface cis effect where an axial ligand at adsorbed transition-metal complexes enables lateral bonding among the molecules. In the absence of this ligand, the intermolecular interaction is repulsive and supramolecular patterns are not observed. Fe-tetramethyl-tetraazaannulene on Au(111) was investigated using low-temperature scanning tunneling microscopy and spectroscopy along with density functional theory calculations. At low coverages, the molecules remain isolated. Exposure to CO leads to axial CO bonding and induces reordering into extended clusters of chiral molecular trimers. The changed self-assembly pattern is due to a CO-induced modification of the molecular structure and the corresponding charge transfer between the molecule and the substrate, which in turn changes the lateral intermolecular forces.
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel , 24118 Kiel, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Knaak
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur , Kanpur 208016, India.
authors.forename: Thiruvancheril G
authors.initials: TG
authors.lastname: Gopakumar
authors.affiliation: Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel , 24118 Kiel, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Schwager
authors.affiliation: Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel , 24118 Kiel, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Tuczek
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The Barcelona Institute of Science and Technology , Campus UAB, Bellaterra, 08193 Barcelona, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Robles
authors.affiliation: Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU) , Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián, Spain.|Donostia International Physics Center (DIPC) , Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Lorente
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel , 24118 Kiel, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Berndt