April 2016   (Technical report   )

A Comparative Study of Diastereomeric Complexes Formed by a Prochiral Substrate and Three Structurally Analogous Chiral Molecules on Pt(111)

Jean-Christian Lemay, Yi Dong, Michael N. Groves, Vincent Demers-Carpentier, Guillaume Goubert, Raphael Lafleur-Lambert, John Boukouvalas, Peter McBreen

A comparative study of chemisorbed bimolecular diastereomeric complexes formed by three structurally analogous chiral modifiers and a prochiral substrate on Pt(111) was performed using scanning tunneling microscopy (STM) and density functional theory (DFT) methods. The experiments determine, subject to a number of assumptions, the abundant binding configurations and whether the complexed substrate is organized into pro-S or pro-R states. The overall prochiral ratio (pr) estimated in this manner may be compared in each case to literature values for the enantiomeric ratio (er) observed in catalysis experiments. The experiments were performed using ketopantolactone as the substrate and (R)-1-(1-naphthyl)ethylamine, (R)-N-Methyl-1-(1-naphthyl)ethylamine and (R)-1-naphthyl-1,2-ethanediol as the structurally analogous chiral modifiers. The STM measurements were performed at room temperature to better mimic conditions under which the catalytic studies reported in the literature were performed. The results are discussed in terms of the stereochemical effects of subtle modifications of the structure of the chiral modifier.

http://www.sciencedirect.com/science/article/pii/S0039602815003969