Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 52: Poster Wednesday: Adsorption and Catalysis 2

O 52.2: Poster

Wednesday, September 7, 2022, 18:00–20:00, P4

Influence of the Substrate Orientation Dependent Reactivity on the On-surface Ullmann Coupling Reaction of 2,2-Dibromobiphenyl Studied by XPS — •Paul Schweer and Karina Morgenstern — Chair of Physical Chemistry I, Ruhr-University of Bochum, Germany

The Ullmann coupling reaction is considered the leading approach for accessing low dimensional covalent organic structures in the context of on-surface synthesis. Despite extensive studies on the influence of the halogen substitution pattern of the halogen-aryl precursor on the reaction mechanism and product formation, the impact of ortho-substitution is barely investigated. Hence, this work aims to reveal the temperature-induced reaction steps for 2,2-dibromobiphenyl on low-index Cu surfaces. For this purpose, the precursor is deposited in ultra-high vacuum at 86 K and stepwise annealed to 600 K. By using X-ray photoelectron spectroscopy, chemical changes of the organic species and the bromine atoms are identified and assigned to the typical Ullmann reaction steps: dissociation of the halogen-carbon bond, surface bonding, and C-C coupling. Here, we further discuss different precursor reactivities on Cu(111) and Cu(110) and an additional binding energy shift on Cu(110), indicating a structural change of the surface bound biphenyl before C-C coupling at a higher temperature.