Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 8: Focus Session Molecular Nanostructures on Surfaces: On-Surface Synthesis and Single-Molecule Manipulation I
O 8.4: Talk
Monday, March 17, 2025, 11:30–11:45, H24
Kinetics of the on-surface reactions of 3,3"-dibromo-p-terphenyl on Cu(111): Cis-trans isomerization as rate limiting step towards the final configurations — •Mohit Jain1, Tamam Bohamud1, Daniel Kohrs2, Nathaniel Ukah2, Hermann A. Wegner2, and Michael Dürr1 — 1Institut für Angewandte Physik and Zentrum für Materialforschung, Justus-Liebig-Universität Giessen, Germany — 2Institut für Organische Chemie and Zentrum für Materialforschung, Justus-Liebig-Universität Giessen, Germany
The kinetics of the on-surface synthesis reactions of 3,3"-dibromo-p-terphenyl were investigated at fixed surface temperature of 300 K. The initially adsorbed molecules linked through C-Cu-C bonds were found in configurations consisting of long, chain-like and few shorter ring-like structures. With the progression of the reaction through time at 300 K, the configurations showed a shift from long chains and closed structures to 3-molecule ring structures. These structures then slowly aligned to form surface-wide phases of 3-molecule closed-ring structures.
The lateral surface mobility of the molecules was observed to be high at 300 K along with the frequent cleavage and re-formation of the C-Cu-C bond; nevertheless the actual transformation of chain structures towards complete ring structures was detected at a much longer timescale. By quantitative analysis, the trans-to-cis isomerization of the molecules which is necessary for closed-ring formation, was found to be the rate limiting step. To further consolidate the results, experiments with different substitution patterns of the p-terphenyl molecules were performed.
Keywords: reaction kinetics; Ulmann coupling; p-terphenyl; Cu(111); scanning tunneling microscopy