SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 90: Poster Session VII: Surface reactions I
O 90.7: Poster
Donnerstag, 4. März 2021, 10:30–12:30, P
Surface-controlled intramolecular radical addition versus C-H insertion toward cyclodehydrogenation under mild conditions — •Qigang Zhong1, Daniel Kohrs2, Jannis Jung3, Daniel Ebeling1, Doreen Mollenhauer3, Hermann A. Wegner2, and Andre Schirmeisen1 — 1Institute of Applied Physics, Justus-Liebig University Giessen, Germany — 2Institute of Organic Chemistry, Justus-Liebig University Giessen, Germany — 3Institute of Physical Chemistry, Justus-Liebig University Giessen, Germany
Despite the ubiquitous existence of aryl radicals in surface reactions, the reactivity of surface-stabilized aryl radicals and its influence on the reaction pathways to C-C coupling remain elusive. Here, we studied the debromination and cyclodehydrogenation of 1-bromo-8-phenylnaphthalene (BPN) on Cu(111) and Ag(111) using bond-resolved scanning probe microscopy. Debromination of BPN at room temperature generated a radical at the naphthyl group which enabled the subsequent cyclodehydrogenation to proceed at mild temperatures (about 350 K on Cu and 420 K on Ag). The reaction temperature is lower on Cu than Ag due to the higher activity of Cu. High-resolution imaging of the cyclized intermediates revealed that radical addition to the phenyl ring transformed the connected C(sp2)-H bond into an out-of-plane C(sp3)-H bond on Cu(111), while the protruding hydrogen atom was shifted to the naphthyl group on Ag(111), reminiscent of C-H insertion in solution. In combination with DFT calculations, we rationalized the different routes to radical C-H activation by the varied reactivity of the aryl radicals depending on the substrate materials.