Paper SS-ThM5
Probing Individual Binding Sites around Individual Chiral Molecules on a Metal Surface: Chemisorption and Non-Covalent Bonding in Heterogeneous Asymmetric Hydrogenation

Thursday, November 10, 2016, 9:20 am, Room 104D

There is rapid progress in the design and application of chirally-modified metal particles for heterogeneous catalytic enantioselective reactions. Modification is achieved by adsorbing chiral molecules to create asymmetric active sites. Great advances are being made in operando studies, surface science studies and theoretical studies of such systems. We will describe combined experimental and theoretical work related to the enantioselective hydrogenation of activated ketones on chirally-modified Pt(111). We will present results from combined variable temperature STM and optB88-vdW DFT studies of individual bimolecular docking complexes formed between enantiopure 1-(1-naphthyl)ethylamine, and related molecules, and representative prochiral substrates. The experiments reveal sub-molecularly resolved site-specific and stereospecific data. Single chemisorbed enanantiomers simultaneously present several chiral pockets, each displaying a specific prochiral ratio for a given substrate molecule. A hierarchy of chemisorption and intermolecular interactions is found to control prochiral selection at each pocket. Fine-tuning the structure of the modifier reveals how sensitive the stereochemical outcome is to even minor molecular changes. Time-lapsed STM measurements of individual substrate molecules sampling a set of chiral pockets provide new insight on stereocontrol, and on reaction paths and barriers at individual binding sites.