title: Switching of an Azobenzene-Tripod Molecule on Ag(111).
abstract: The trans-cis isomerization makes azobenzene (AB) a robust molecular switch. Once adsorbed to a metal, however, the switching is inefficient or absent due to rapid excited-state quenching or loss of the trans-cis bistability. We find that tris-[4-(phenylazo)-phenyl]-amine is a rather efficient switch on Ag(111). Using scanning tunneling and atomic force microscopy at submolecular resolution along with density functional theory calculations, we show that the switching process is no trans-cis isomerization but rather a reorientation of the N-N bond of an AB unit. It proceeds through a twisting motion of the azo-bridge that leads to a lateral shift of a phenyl ring. Thus, the role of the Ag substrate is ambivalent. While it suppresses the original bistability of the azobenzene units, it creates a new one by inducing a barrier for the rotation of the N-N bond.
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität , 24098 Kiel, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Scheil
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 Physikalische Chemie, Christian-Albrechts-Universität , 24098 Kiel, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Bahrenburg
authors.affiliation: Institut für Physikalische Chemie, Christian-Albrechts-Universität , 24098 Kiel, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Temps
authors.affiliation: Lehrstuhl für Theoretische Chemie, Technische Unversität München , 85747 Garching, Germany.
authors.forename: Reinhard Johann
authors.initials: RJ
authors.lastname: Maurer
authors.affiliation: Lehrstuhl für Theoretische Chemie, Technische Unversität München , 85747 Garching, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Reuter
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität , 24098 Kiel, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Berndt