title: Toward cove-edged low band gap graphene nanoribbons.
abstract: Graphene nanoribbons (GNRs), defined as nanometer-wide strips of graphene, have attracted increasing attention as promising candidates for next-generation semiconductors. Here, we demonstrate a bottom-up strategy toward novel low band gap GNRs (Eg = 1.70 eV) with a well-defined cove-type periphery both in solution and on a solid substrate surface with chrysene as the key monomer. Corresponding cyclized chrysene-based oligomers consisting of the dimer and tetramer are obtained via an Ullmann coupling followed by oxidative intramolecular cyclodehydrogenation in solution, and much higher GNR homologues via on-surface synthesis. These oligomers adopt nonplanar structures due to the steric repulsion between the two C-H bonds at the inner cove position. Characterizations by single crystal X-ray analysis, UV-vis absorption spectroscopy, NMR spectroscopy, and scanning tunneling microscopy (STM) are described. The interpretation is assisted by density functional theory (DFT) calculations.
authors.affiliation: †Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Junzhi
authors.initials: J
authors.lastname: Liu
authors.affiliation: ‡State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
authors.forename: Bo-Wei
authors.initials: BW
authors.lastname: Li
authors.affiliation: ‡State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
authors.forename: Yuan-Zhi
authors.initials: YZ
authors.lastname: Tan
authors.affiliation: §Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium.
authors.forename: Angelos
authors.initials: A
authors.lastname: Giannakopoulos
authors.affiliation: ∥Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sanchez-Sanchez
authors.affiliation: §Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium.
authors.forename: David
authors.initials: D
authors.lastname: Beljonne
authors.affiliation: ∥Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Ruffieux
authors.affiliation: ∥Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.|⊥Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Fasel
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: †Max-Planck Institut für Polymerforschung, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen