Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 11: Focus Session: Molecular Nanostructures on surfaces - New Concepts towards Complex Architectures I
O 11.9: Vortrag
Montag, 12. März 2018, 17:30–17:45, MA 004
On-surface synthesis of indenofluorene polymers using methyl groups to form 5-membered rings — •Marco Di Giovannantonio1, José I. Urgel1, Aliaksandr Yakutovich1, Jan Wilhelm2, Uliana Beser3, Akimitsu Narita3, Carlo A. Pignedoli1, Pascal Ruffieux1, Klaus Müllen3, and Roman Fasel1,4 — 1Empa - Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, 8600 Dübendorf, Switzerland — 2University of Zurich, Department of Chemistry, 8057 Zurich, Switzerland — 3Max Planck Institute for Polymer Research, 55128 Mainz, Germany — 4Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
On-surface synthesis has opened pathways to molecular nanostructures that have been inaccessible so far. Here, we show the surface-assisted aryl-aryl coupling of brominated precursor molecules, followed by the cyclization of methyl groups on a poly(para-phenylene) backbone to form 5-membered rings, and to realize a fully conjugated chain composed of indenofluorene units. Indenofluorenes are appealing molecules consisting of an array of fused 6-5-6-5-6-membered rings with 20 π-electrons, which have received increasing attention for their formal anti-aromaticity, open-shell biradical character, and narrow HOMO-LUMO gap. The structure and electronic properties of the obtained indenofluorene polymers have been characterized by STM, nc-AFM, and STS, which are supported by theoretical calculations. The reported synthetic protocol can potentially be extended to other novel molecular nanostructures to fine tune their electronic properties.