Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 79: Surface Reactions and Heterogeneous Catalysis 3
O 79.5: Talk
Friday, September 9, 2022, 11:45–12:00, H4
Deciphering the intramolecular C-C coupling mechanism of a model aryl radical via bond-level AFM imaging — •Qigang Zhong1, Jannis Jung2, Daniel Kohrs3, Daniel Ebeling1, Doreen Mollenhauer2, Hermann A. Wegner3, and André Schirmeisen1 — 1Institute of Applied Physics, Justus-Liebig University Giessen (JLU), Germany — 2Institute of Physical Chemistry, JLU, Germany — 3Institute of Organic Chemistry, JLU, Germany
Although on-surface dehalogenative and dehydrogenative C-C coupling has proved to be a versatile and prevailing approach to constructing atomically precise carbon-based nanostructures, understanding of the reaction mechanisms remains limited by the elusive intermediates. Here, we studied the intramolecular cyclodehydrobromination of 1-bromo-8-phenylnaphthalene on Cu(111) and Ag(111) using bond-level atomic force microscopy (BL-AFM). The reaction occurs at room temperature on both metal surfaces, while the reaction rate on Cu(111) is much higher than that on Ag(111) presumably due to the higher catalytic activity of copper. Surface-bound radicals, cyclized intermediates and dehydrogenated product were captured by BL-AFM imaging and verified by DFT calculations, suggesting a multi-step reaction process, i.e. debromination, radical cyclization and dehydrogenation. The large proportion (up to 65 percent) of cyclized intermediates on Cu(111) indicates that dehydrogenation is the rate-determining step, which is corroborated by DFT calculations of activation barriers. To achieve a reasonable activation barrier for dehydrogenation, multiple pathways were theoretically evaluated.