Monte Carlo Studies of Segregation of Enantiomers and Induction of Chirality in Adlayers of Tartrate and Succinate

C.G.M. Hermse and A.P.J. Jansen

Schuit Institute of Catalysis SKA, Eindhoven University of Technology, Eindhoven, The Netherlands

We have used Density-Functional Theory to determine the nature and the strengths of the lateral interactions in tartrate layers on Cu(110). The results show that the chirality in (R,R)-tartrate is due to steric repulsion between OH groups, whereas hydrogen bonds are only formed intramolecularly. The trough in the (9 0, 1 2) structure is caused by adsorbate-induced stress in the surface along the rows of Cu atoms. The steric repulsion seems to be the more important factor to explain the structures of adlayers of tartrate and similar molecules. So we have made some simpler models without stress and with hard sphere interactions modeling the other interactions. We have used these models in (kinetic) Monte Carlo simulations to study the induction of chirality in adlayers of succinate by tartrate, and to study the segregation of (R,R)- and (S,S)-tartrate. The segregation is a consequence of close-packing in these models. The induction of chirality in succinate depends on the adsorption mode of the succinate. If the succinate adsorbs to four Cu atoms forming a rectangle, as does tartrate, then little or no chiral induction is found. If the four Cu atoms form a skewed parallelogram, then chiral induction is possible provided the succinate can changed between the two orientation that are possible for that adsorption mode.