AVS 60th International Symposium and Exhibition
    Surface Science Thursday Sessions
       Session SS-ThM

Paper SS-ThM2
Creation of Local Chiral Surface Environments via the Adsorption of Propylene Oxide on achiral Pt(111) Surfaces

Thursday, October 31, 2013, 8:20 am, Room 202 A

Session: Chirality & Enantioselectivity on Surfaces
Presenter: S. Karakalos, University of California, Riverside
Authors: S. Karakalos, University of California, Riverside
F. Zaera, University of California, Riverside
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The efficient development of enantiomeric separations has become increasingly important, especially in the pharmaceutical industry, as optical isomers often show different biological behavior, some detrimental to physiological functions. Two-dimensional (2D) molecular surface science aims at understanding molecular recognition, the nature and consequences of intermolecular interactions. The identical alignment of molecules due to adsorption on 2D surfaces, imposes a directionality among lateral interactions. In this study, temperature programmed desorption (TPD), molecular beam (MB) experiments, and Monte Carlo (MC) simulations have been carried out to investigate how propylene oxide (PO), a small chiral molecule, can act as a seed to induce enantioselective adsorption on Pt(111) single-crystal surfaces. TPD results showed that the adsorption of a small initial amount of enantiopure PO on Pt(111) leads to differences in the coverages of a second adsorbate such as enantiopure propylene oxide or propylene (Py), as probed by using a third molecule. Additional studies of isotope exchange on the Pt(111) surface by coadsorbing regular and deuterated PO showed significant replacement of the initially adsorbed PO by the incoming molecules. By using deuterated Py with regular PO, it was also possible to assess the contribution of each molecule on the total coverage on the surface and establish that the induced chirality from the seeding PO plays a crucial role in the final surface coverage. The sticking probabilities of Py, measured by MB experiments on clean Pt(111) and on various PO/Pt(111) systems, identified differences in the adsorption kinetics indicating that the adsorbed chiral PO can lead to desired enantiolselective reactions. Initial Monte Carlo simulations have show promise in their ability to reproduce these sticking probabilities.