AVS 65th International Symposium & Exhibition
    Surface Science Division Tuesday Sessions
       Session SS+HC+NS+PS-TuM

Paper SS+HC+NS+PS-TuM4
The Mechanism of Glaser Coupling Reactions on Ag(111) and Cu(111) Surfaces: a Case for Halogen Substituted Terminal Alkyne

Tuesday, October 23, 2018, 9:00 am, Room 203C

Session: Controlling Mechanisms of Surface Chemical Reactions
Presenter: Junfa Zhu, National Synchrotron Radiation Laboratory and Department of Chemical Physics, University of Science and Technology of China
Authors: T. Wang, University of Science and Technology of China
H.F. Lv, University of Science and Technology of China
L. Feng, University of Science and Technology of China
J.M. Huang, University of Science and Technology of China
X.J. Wu, University of Science and Technology of China
J.F. Zhu, National Synchrotron Radiation Laboratory and Department of Chemical Physics, University of Science and Technology of China
Correspondent: Click to Email
Ullman and Glaser homo-couplings are the two most well-developed on-surface coupling reactions, which have been successfully employed to fabricate one-dimensional and two-dimensional nanostructures on metal surfaces. The mechanism towards surface-confined Ullman coupling has been well-established. However, the mechanism of surface-confined Glaser coupling has been poorly understood. In this presentation, we report our recent studies on the surface-confined Glaser coupling reactions on Ag(111) and Cu(111) using 1,1’-biphenyl,4-bromo-4’-ethynyl (BPBE) as the precursor molecule. By direct observations of alkynyl-Ag-alkynyl and alkynyl-Cu-alkynyl type organometallic intermediates on Ag(111) and Cu(111), respectively, we have proposed a reaction pathway initiated by single-molecule dehydrogenation, similar as the mechanism of on-surface Ullman coupling. The reaction processes were further explored by density functional theory based transition state calculations. Interestingly, the dehydrogenation of terminal alkyne is revealed as a H adatom-related process on Ag(111) while a Cu adatom-related process on Cu(111). After the release of interstitial metal adatoms in the organometallic intermediates, the final C-C coupling occurs easily on Ag(111), but shows extremely low efficiency on Cu(111) due to the too strong interaction between ethynylene and the Cu(111) substrate. In addition, we have demonstrated that Glaser reaction of the molecule is prior to Ullman reaction on Ag(111), which provides a promising approach of stepwise fabrication of sp-hybrid nanostructures. This work is supported by the National Natural Science Foundation of China (21773222, 21473178) and the National Key R&D Program of China (2017YFA0403402).