Dresden 2017 – scientific programme
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O: Fachverband Oberflächenphysik
O 97: Nanostructures at Surfaces: Molecular Systems II
O 97.4: Talk
Thursday, March 23, 2017, 16:15–16:30, REC/PHY C213
A comparative temperature-programmed XPS study of surface-assisted Ullmann coupling on Au(111) vs. Ag(111) — •Massimo Fritton1,2, David Duncan1, Peter Deimel1, Atena Rastgoo Lahrood1,2, Francesco Allegretti1, Wolfgang M. Heckl1,2,3, and Markus Lackinger1,2,3 — 1Departement of Physics, TU München, James-Franck-Str. 1 — 2Center for NanoScience (CeNS), Schellingstr. 4 — 3Deutsches Museum, Museumsinsel 1
The intention of our study is to compare the kinetics of thermally activated Ullmann coupling of 1,3,5-Tris(4-bromophenyl)benzene on Au(111) vs. more reactive Ag(111) under ultrahigh vacuum conditions. Two aspects are studied here: activation by cleavage of halogen substituents as well as formation and conversion of reaction intermediates, i.e. organometallic networks. Therefore, we use temperature-programmed XPS (TP-XPS) in combination with STM. TP-XPS allows us to track the progression of dehalogenation, vs. temperature while heating due to chemical shifts of the Br 3d line. On Ag(111) debromination starts at 250 K and is completed at 300 K, while on Au(111) the dehalogenation occurs at higher temperature and over a more extended temperature range between 330 K and 460 K. STM images on both surfaces endorse the spectroscopic data. On Ag(111) the organometallic intermediates can easily be distinguished by the increased bond length and a bright feature corresponding to the C-Ag-C linkages. In contrast on Au(111) annealing directly leads to the covalent network formation.