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ENREMOS Report Summary

Project ID: 335205
Funded under: FP7-IDEAS-ERC
Country: Germany

Mid-Term Report Summary - ENREMOS (Enantioselective Reactions on Model Chirally Modified Surfaces)

Imparting chirality to non-chiral metal surfaces by adsorption of chiral modifiers is a highly promising route to create effective heterogeneously catalyzed processes for production of enantiopure pharmaceuticals. A molecular-level understanding of enantioselective processes on chiral surfaces is an importance prerequisite for the rational design of new enantiospecific catalysts, which is currently nearly missing. The present project addresses this topic from the viewpoint of surface science and aims at the fundamental level understanding of the structure of chirally modified surfaces, the bonding of the prochiral substrate on the chiral media and the details of the kinetics and dynamics of enantioselective surface reactions. We apply a combination of the molecular beam techniques, infrared spectroscopy (IRAS) and scanning tunneling microscopy to obtain a full mechanistic picture of these aspects. The reactive processes on chiral surfaces are carried out both on the extended single crystal surfaces, mimicking a local interaction of the modifier-substrate complexes with a metal, and on the small chirally modified nanoparticles that more accurately resemble the structural properties and high catalytic activity of practically relevant powdered supported catalyst.
In the first reporting period, experimental equipment (a UHV system consisting of a preparation and scattering chamber, two effuse and one supersonic molecular beams, IRAS, STM and a high pressure cell) was installed/tested and the preparation and characterization of the single crystalline and thin-film oxide samples was optimized. First experimental results were obtained for adsorption of chiral modifiers and prochiral substrates onto these samples. Additionally, adsorption behavior and reactivity of prochiral and chiral molecules has been studied in two different UHV apparatus provided by the host institution. In these studies, the adsorption behavior and reactivity in partial hydrogenation of multi-unsaturated hydrocarbons (isophorone, acrolein) was investigated by a combination of IRAS and molecular beam experiments. These experiments were complemented by synchrotron-based studies on the adsorption behavior of isophorone over Pd (111) investigated by NEXAFS. In this part of the project, we investigated the interaction of these molecules with the clean single crystals and pristine metal nanoparticles, which will be later compared with the reactivity behavior of the same molecules on the chirally-modified surfaces.
Besides of that, a UHV single crystal calorimetry (SCAC) apparatus was used for direct determining the binding energies and dynamics of adsorption process of pro-chiral molecules (S- and R- propylene oxide) on chirally modified surfaces. Here two types of chiral modifiers supported on Pt(111) were investigated: (R)-(+)-1-(1-naphthyl)ethylamine and (S)-(+)-2-methylbutanoic acid. Different types of adsorption dynamics were observed in this study.
These studies are the basis for the more complex in-situ studies that will be tackled in the second period of the project.

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