Chiral Single Crystal Surface Chemistry

Several experiments have been performed to probe the enantiospecific properties of chiral single crystal surfaces. The surfaces chosen have been the (643) planes of Ag and Cu, both face centered cubic structures. The chirality of these surfaces arises from the handedness of their kinked step structures. These structures are such that the (643) and the Image surfaces are related by mirror symmetry but are non-superimposable. We denote them as (643)R and (643)S. As a consequence of this handedness it is expected that the interactions of these surfaces with the left- and right-handed enantiomers of a chiral molecule should be different. In other words the chemistry of chiral molecules on these surfaces should be enantiospecific. We have observed that the desorption energies of R-3-methyl-cyclohexanone differ by 0.22±0.05 kcal/mole on the Cu(643)R and the Cu(643)S surfaces. Similarly, on the Ag(643)R surface we have observed that the orientations of R- and S-2-butanoxy groups differ. This enantiospecific orientation is revealed by the intensities of the absorption bands in an infrared absorption spectra of these species on the Ag(643)R surface. These two results expand the small but growing set of observations of the enantiospecific properties of chiral single crystal surfaces.