Mechanistic Picture and Kinetic Analysis of Surface-Confined Ullmann Polymerization
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- 作者：Marco Di Giovannantonio ; Massimo Tomellini ; Josh Lipton-Duffin ; Gianluca Galeotti ; Maryam Ebrahimi ; Albano Cossaro ; Alberto VerdiniNeerav Kharche ; Vincent Meunier ; Guillaume Vasseur ; Yannick Fagot-Revurat ; Dmitrii F. Perepichka ; Federico Rosei ; Giorgio Contini
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：December 28, 2016
- 年：2016
- 卷：138
- 期：51
- 页码：16696-16702
- 全文大小：566K
- ISSN：1520-5126
文摘
Surface-confined polymerization via Ullmann coupling is a promising route to create one- and two-dimensional covalent π-conjugated structures, including the bottom-up growth of graphene nanoribbons. Understanding the mechanism of the Ullmann reaction is necessary to provide a platform for rationally controlling the formation of these materials. We use fast X-ray photoelectron spectroscopy (XPS) in kinetic measurements of epitaxial surface polymerization of 1,4-dibromobenzene on Cu(110) and devise a kinetic model based on mean field rate equations, involving a transient state. This state is observed in the energy landscapes calculated by nudged elastic band (NEB) within density functional theory (DFT), which assumes as initial and final geometries of the organometallic and polymeric structures those observed by scanning tunneling microscopy (STM). The kinetic model accounts for all the salient features observed in the experimental curves extracted from the fast-XPS measurements and enables an enhanced understanding of the polymerization process, which is found to follow a nucleation-and-growth behavior preceded by the formation of a transient state.