Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 49: Poster: Nanostructures on Surfaces I

O 49.1: Poster

Tuesday, March 13, 2018, 18:15–20:30, Poster A

Ullmann Coupling of 1,3-Dibromoazulene — •Claudio K. Krug, Qitang Fan, Florian Fillsack, Johannes Glowatzki, Nicole Trebel, Martin Schmid, and J. Michael Gottfried — Department of Chemistry, Philipps-Universität Marburg, Germany, Hans-Meerwein-Str. 4, 35032 Marburg

The surface-confined Ullmann coupling reaction is a well-established strategy for creating covalent bonds between formerly halogenated aromatic molecules on coinage metal surfaces. So far, the focus has been on benzoid carbon backbones with alternant topologies. Here, we report the first Ullmann coupling involving a non-alternant aromatic hydrocarbon backbone. Specifically, the reaction of 1,3-dibromoazulene (DBAz) on Cu(111) was studied by means of scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) under ultrahigh vacuum (UHV) conditions. Upon room temperature deposition of DBAz on Cu(111), long regioirregular chains are formed. The organometallic character suggested by the lattice constant is confirmed by XPS. Annealing to 440 K transforms the chains to cyclic organometallic hexamers with high yield. We have investigated the formation of these hexamers depending on the surface coverage. At low coverages, only isolated hexamers are observed because of lateral repulsive interactions. Increasing the coverage yields larger islands of Cu-DBAz cyclic hexamers. Annealing to higher temperatures results in the formation of regioregular covalent chains.