Paper SS-ThM5
Single-Site Studies of Chirality Transfer Complexes on Chirally Modified Pt(111)

Thursday, November 1, 2012, 9:20 am, Room 22

Stereoselective catalytic sites on achiral metallic surfaces may be prepared by adsorbing optically active compounds described as chiral modifiers. A fundamental understanding of the stereodirecting forces in such systems is necessary to develop more efficient enantioselective catalysts. We will present data for chirality transfer complexes formed by the chiral modifier (R)-(+)-1-(1-naphthyl)ethylamine ((R)-NEA) and pro-chiral α-phenylketone and α-ketoester substrates on Pt(111). Time-lapsed scanning tunneling microscopy allowed us to isolate individual chiral modifier/substrate complexes. The structure of the diastereomeric complexes were separately determined using DFT calculations. The extremely good convergence between the calculated structures and visual STM data, as well as supporting surface spectroscopy data, shows that prochiral steering on chirally modified Pt(111) can be followed with submolecular resolution at the reaction temperature (room temperature), thus enabling conformational, regiospecific and enantiospecific characterisation. The study reveals the contributions of steric repulsion, non-covalent attractive interactions and site-specific chemisorption to stereoinduction. We will conclude with a short description of the targeted design of new chiral modifiers.