title: Purely Armchair or Partially Chiral: Noncontact Atomic Force Microscopy Characterization of Dibromo-Bianthryl-Based Graphene Nanoribbons Grown on Cu(111).
abstract: We report on the atomic structure of graphene nanoribbons (GNRs) formed via on-surface synthesis from 10,10'-dibromo-9,9'-bianthryl (DBBA) precursors on Cu(111). By means of ultrahigh vacuum noncontact atomic force microscopy with CO-functionalized tips we unveil the chiral nature of the so-formed GNRs, a structure that has been under considerable debate. Furthermore, we prove that-in this particular case-the coupling selectivity usually introduced by halogen substitution is overruled by the structural and catalytic properties of the substrate. Specifically, we show that identical chiral GNRs are obtained from 9,9'-bianthryl, the unsubstituted sister molecule of DBBA.
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sánchez-Sánchez
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dienel
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
authors.forename: Okan
authors.initials: O
authors.lastname: Deniz
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Ruffieux
authors.affiliation: Center for Advancing Electronics Dresden (cfaed) and Department of Chemistry and Food Chemistry, Technische Universität Dresden , D-01062 Dresden, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Berger
authors.affiliation: Center for Advancing Electronics Dresden (cfaed) and Department of Chemistry and Food Chemistry, Technische Universität Dresden , D-01062 Dresden, Germany.
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: Max Planck Institute for Polymer Research , D-55128 Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.|Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, CH-3012 Bern, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Fasel
keywords: armchair; bottom-up; chiral; functionalized tip; graphene nanoribbons; on-surface synthesis