Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 35: Poster Session II (Polymeric biomolecular films; Nanostructures; Electronic structure; Spin-orbit interaction; Phase transitions; Surface chemical reactions; Heterogeneous catalysis; Particles and clusters; Surface magnetism; Electron and spin dynamics; Surface dynamics; Methods; Electronic structure theory; Functional molecules)
O 35.5: Poster
Tuesday, March 27, 2012, 18:15–21:45, Poster B
Covalently bonded mixed chains of Br-NDI and Br-TTP molecules — •Finn Lorbeer1, Isabel Fernandez Torrente1, Martina Corso1, Lena Kaufmann2, Max Kerbs2, Arno Wiehe2, Christoph A. Schalley2, Andrew DiLullo3, Saw-Wai Hla3, José Ignacio Pascual1, and Katharina J. Franke1 — 1Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Insitut für Chemie und Biochemie, Freie Universität Berlin, Takustraß e 3, 14195 Berlin, Germany — 3Dept. of Physics and Astronomy, Clippinger Lab 251B, Athens, OH 45701, USA
A promising route for the synthesis of a junction composed of a molecular charge donor and an acceptor on a surface resembling a diode, is the controlled formation of a covalent bond between individual organic donor and acceptor species. Here we use low temperature scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) to investigate the brominated naphthalenediimide (Br-NDI) and tetra(4-bromophenyl)porphyrin (Br-TPP) bond formation on Au(111).
For preparation temperatures of 300 K the Br-NDI and Br-TPP form H-bonded networks. Above 650 K annealing temperature we de-brominate the two species and covalently bonded chains are formed. The electronic properties of the TPP remain unaffected after the bond formation. In contrast the flexible NDI molecule is geometrically distorted in the chains and the energy level alignment depends on this deformation as well as on the neighbors in the chain. We can change the geometric configuration of the NDI by vertical manipulation and hence shift the energy levels without affecting the covalent chains.