Enantioselective Reactions on Chirally-Modified Model Surfaces: A New Molecular Beam/Surface Spectroscopy Apparatus
2Institute of Physical Chemistry, Christian Albrechts University of Kiel, Kiel
A molecular-level understanding of enantioselective processes on chiral surfaces is an important prerequisite for the rational design of new enantiospecific catalysts. Therefore, in this study, the reaction mechanisms, kinetics and dynamics of surface reactions were investigated using multi-molecular beam techniques and in-situ surface spectroscopic and microscopic tools on well-defined model surfaces in UHV.
A new UHV apparatus consisting of two independent UHV systems for the preparation and characterization of chirally modified model catalysts has been designed and built. This apparatus comprises three molecular beams (two effusive and one supersonic molecular beam), infrared reflection absorption spectroscopy (IRAS) as well as a number of standard tools for preparation and characterization of model surfaces, both single crystals and nanostructured surfaces consisting of metal nanoparticles supported on thin oxide films. Additionally, the sample can be transferred to an independent unit containing scanning tunneling microscope (STM).
First experiments were carried out at the newly setup UHV apparatus to investigate adsorption and reactivity behavior of a model chiral modifier (R)-(+)-1-(1-Naphthyl)ethylamine (NEA) and a prochiral molecule acetophenone over Pt(111). These processes were investigated over a broad range of coverage and temperature conditions. NEA was found to homogeneously distribute over Pt(111) surface at low coverage and to build island-like structures in the high coverage regime. Currently, co-adsorption of NEA with acetophenone is investigated with STM to follow the formation of NEA-acetophenone complexes on this chirally modified surface.
Spectroscopically, acetophenone was observed to strongly interact with the pristine Pt(111) surface resulting in strong changes of the IR spectra as compared to the unperturbed molecules in multilayers. Further experiments are currently in progress.
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