AVS 58th Annual International Symposium and Exhibition
    Surface Science Division Monday Sessions
       Session SS2-MoA

Paper SS2-MoA8
Influence of Solvent on the Chiral Resolution of Organic Molecules on Au(111): EC-STM Study of Biphenyl Dicarboxylic Acid on Au (111) in an Aqueous Environment

Monday, October 31, 2011, 4:20 pm, Room 110

Session: Molecular Ordering and Electrochemical Interfaces
Presenter: Byung Kim, Boise State University
Authors: B.I. Kim, Boise State University
J.A. Hanson, Boise State University
M.W. Turner, Boise State University
L.J. Reeder, Boise State University
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Adsorption induced chiral resolution of organic molecules is important due to its potential applications in stereo-selective catalysis. We studied the adsorption induced chiral resolution using a model achiral molecule of 4,4’ biphenyl dicarboxylic acid (BPDA) on Au (111) in 0.1 M perchloric acid (HClO4) by scanning tunneling microscopy (STM). The BPDA molecules are known to have chiral resolution on Au(111) in an ultrahigh vacuum (UHV). However, our experimental data show that the molecules form island structures with distinctive preferred orientations at the length scale of the molecular size, whereas they have no orientation order at the length scale bigger than the molecular size. We calculated angle dependent binding energy between the substrate and a BPDA molecule, the intermolecular interactions between the BPDA molecules and their interactions with water molecules. The calculation suggests that the absence of chiral resolution in the aqueous environment may originate from the increase of effective rotation energy barrier of the BPDA molecules due to its hydrogen bonding with the surrounding water molecules. The strength hydrogen binding between BPDA molecules is sufficient to overcome the energy barrier for chiral resolution through rotational motion in UHV, but not in an aqueous environment.