title: On-Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles.
abstract: We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C180H120) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Straße 4, 35032 Marburg, Germany.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Jian
authors.initials: J
authors.lastname: Shang
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Kai
authors.initials: K
authors.lastname: Wu
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Straße 4, 35032 Marburg, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Kuttner
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Straße 4, 35032 Marburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hilt
authors.affiliation: Lehrstuhl für Theoretische Chemie and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg , Egerlandstraße 3, 91058 Erlangen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hieringer
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Straße 4, 35032 Marburg, Germany.
authors.forename: J Michael
authors.identifier: 0000-0001-5579-2568
authors.initials: JM
authors.lastname: Gottfried
keywords: Ullmann reaction; conjugation; electron confinement; macrocycle; on-surface synthesis; quantum corral; scanning tunneling microscopy