AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA5
Stereochemistry in Surface Explosion

Tuesday, November 16, 2004, 2:40 pm, Room 210B

Session: Hydrocarbon Reactions on Metal Surfaces
Presenter: K.-H. Ernst, EMPA Duebendorf, Switzerland
Authors: K.-H. Ernst, EMPA Duebendorf, Switzerland
B. Behzadi, EMPA Duebendorf, Switzerland
R. Fasel, EMPA Duebendorf, Switzerland
S. Romer, EMPA Duebendorf, Switzerland
Correspondent: Click to Email
The vast majority of chiral compounds crystallize into racemic crystals. It has been predicted early and was later experimentally established as a rule, that chiral molecules on surfaces are more easily separated into homochiral domains due to confinement into a 2D-plane and lower entropic contributions. We investigated the formation and stability of two-dimensional tartrate lattices on a Cu(110) surface for the racemic mixture by means of temperature programmed desorption (TPD), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). At low coverage, the bitartrate species becomes separated into homochiral domains, but with increasing surface density the monotartrate species forms a closed-packed racemic 2-D crystal. Consequently, the 2-D conglomerate bitartrate phase does not show differences to the enantiopure bitartrate phase with respect to thermal stability. However, the thermally induced autocatalytic decomposition reaction, so-called surface explosion, of the monotartrate species is influenced by the chirality of the adjacent molecules. The racemic mixture undergoes decomposition at a lower temperature than the enantiopure lattice at same coverage and lateral arrangement. This is in contrast to the higher stability of 3D tartaric acid crystals, but is consistent with the observation that homochirality is preferred in hydrogen-bonded self-assembled biomolecular structures.