COLL 179 |
| Sanjini U. Nanayakkara, E. Charles H. Sykes, Luis C. Fernández-Torres, Patrick Han, and Paul S. Weiss. Departments of Chemistry and Physics, The Pennsylvania State University, 152 Davey Laboratory, University Park, PA 16802 |
| We present an atomic-scale study of the Ullmann coupling reaction between aromatic halides, which form biaryls on a Cu{111} surface, utilizing low temperature scanning tunneling microscopy and spectroscopy. Chemical identification of the surface-bound intermediates has been achieved using their spectroscopic signatures. We demonstrate that when the bromobenzene molecules dissociatively chemisorb at 293 K, they form phenyl intermediates, which travel distances of up to a few 1000 Ĺ over bare Cu{111} terraces to bind preferentially at step edges. We attribute this effect to the anisotropic electron density distribution at the steps. We illustrate that C-C bond formation only takes place at the steps, and once phenyl intermediates combine to form biphenyl molecules and the adsorption sites at the steps are saturated, these molecules diffuse onto the terraces. Our observations of intermolecular interactions on the molecular scale are explained in terms of the local electronic perturbations by surface defects and adsorbates. |
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Posters: Fundamental Research in Surface and Colloid Chemistry
6:00 PM-8:00 PM, Monday, August 23, 2004 Pennsylvania Convention Center -- Hall C, Poster
Division of Colloid and Surface Chemistry |