Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)

O 35.22: Poster

Dienstag, 12. März 2013, 18:15–21:45, Poster B1

Combined photoemission and STM study of the surface-assisted Ullmann coupling reaction — •Min Chen¹, Jie Xiao², Hans-Peter Steinrück², Shiyong Wang³, Weihua Wang³, Nian Lin³, and Michael Gottfried¹ — ¹Fachbereich Chemie, Philipps-Universität Marburg — ²Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg — ³Department of Physics, Hong Kong University of Science and Technology

The Ullmann reaction, a Cu catalyzed C-C coupling reaction for haloarenes has been used for surface-assisted synthesis two-dimensional covalent nanostructures. Generally, this reaction provides a versatile route to the formation of larger arenes and arene-based extended nanostructures, especially one-dimensional molecular wires and two-dimensional covalent organic networks. In this study, we provide evidence for the Ullmann reaction of 4,4''-Dibromo-p-terphenyl (DBTP) and 1,3,5-Tris(4-bromophenyl)benzene (TBB) on Cu(111) by using X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) as well as scanning tunneling microscopy (STM). Assisted by Cu atoms from substrate, the C-Br bonds break between 170 and 240 K, and neighboring molecules get linked through intermediate C-Cu-C bonds. Upon further increasing the temperature, the C-Cu-C bonds are transformed into C-C bonds, such that neighboring arene fragments are covalently coupled, while Cu is released from the bridge positions. STM gives insight into the reaction progress on the molecular level. Our results provide an example for a possible strategy towards the bottom-up construction of functional devices based on molecular building blocks.