Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 32: Focus Session: Designer Quantum Systems II (joint session O/TT)
TT 32.4: Vortrag
Dienstag, 2. April 2019, 15:15–15:30, H15
On-Surface Synthesis and Characterization of Cycloarenes: a C108 Graphene Quantum Ring — •Qitang Fan1, Daniel Martin Jimenez2, Simon Werner1, Daniel Ebeling2, André Schirmeisen2, Jörg Sundermeyer1, Wolfgang Hieringer3, and J. Michael Gottfried1 — 1Fachbereich Chemie, Philipps-Universität Marburg, Germany — 2Institute of Applied Physics (IAP), Justus Liebig University Gießen, Germany — 3Lehrstuhl für Theoretische Chemie, Universität Erlangen-Nürnberg, Germany
Cycloarenes, such as kekulene, are a unique class of polycyclic aromatic hydrocarbons (PAHs). They enclose a cavity by circularly annulated benzene rings. In a modern view, they can thus be considered as nanorings cut-out from graphene with atomic precision. These graphene rings could serve as useful model quantum materials for the exploration of geometry-dependent electronic properties of nanographenes, e.g., the Aharonov-Bohm effect in graphene quantum rings. However, the synthesis and characterization of cycloarenes with more than one band of benzene rings is still challenging due to their special ring-shaped geometry and low solubility. Here, we employed the high-dilution principle both on a metal surface and in solution to synthesize a novel hexagonal cycloarene with two bands of annulated benzene rings, containing 108 sp2 carbons, by hierarchical Ullmann coupling and cyclodehydrogenation reaction of dibrominated aromatic precursors. The structure and properties of this C108 cycloarene molecule has been unambiguously clarified by various techniques including STM/STS, nc-AFM, UV-vis spectroscopy, and DFT calculations.