Speaker
Description
A molecular-level understanding of enantioselective processes on chirally modified 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 vacuum systems for preparation and characterization of chirally modified model catalysts as well as investigations of their reactivity behavior 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 nano-structured surfaces consisting of metal nano-particles supported on thin oxide films. Additionally, the sample can be transferred to an independent unit containing scanning tunneling microscope (STM), as well as to high pressure cell, where the reactivity of the chirally modified model catalysts can be investigated under ambient pressure conditions.
First experiments were carried out at the newly UHV setup to investigate adsorption and reactivity behavior of a 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. 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.
NEA was found to homogeneously distribute over Pt(111) surface at room temperature, and to build self-assembled structures at 180K. Spectroscopically, it was found that NEA adopts a tilted geometry at sub-monolayer coverages. Lastly, CO was used as a first proxy to probe the interactions of carbonyl compounds with the chiral modifier and was found to strongly interact with the NEA.
Currently, co-adsorption of NEA with acetophenone is investigated with STM to follow the formation of NEA-acetophenone complexes on this chirally modified surface.
