AVS 52nd International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP18
Chiral Attachment of Styrene Mediated by Surface Dimers on Ge(100)

Tuesday, November 1, 2005, 4:00 pm, Room Exhibit Hall C&D

Session: Surface Science Poster Session
Presenter: Y.J. Hwang, Korea Advanced Institute of Science and Technology (KAIST), South Korea
Authors: Y.J. Hwang, Korea Advanced Institute of Science and Technology (KAIST), South Korea
A. Kim, Korea Advanced Institute of Science and Technology (KAIST), South Korea
E.K. Hwang, Korea Advanced Institute of Science and Technology (KAIST), South Korea
S. Kim, Korea Advanced Institute of Science and Technology (KAIST), South Korea
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We determine the absolute chirality of adsorbed styrene using scanning tunneling microscope (STM) and demonstrate a novel method for the achiral molecule to produce dimeric enantiomers and diastereomers covalently bonded to the Ge(100) surface. On the Ge(100) surface, styrene adsorbs in a paired end-bridge between two neighboring Ge dimers within the same dimer row (PEB) as well as on the top of a single Ge-Ge dimer (OT). The OT configuration is classified into (S) and (R) OT chiral products according to the direction in which styrene molecule attacks the Ge dimer. Similarly, in case of paired adsorption, we found enantiomeric (R,R)- and (S,S)-trans-PEB and diastereomeric (R,S)-cis-PEB configurations through STM images.@footnote 1@ Temperature programmed desorption (TPD) spectra indicated that the desorption temperatures for the OT and PEB configurations are 320 K and 365 K, respectively. STM measurements indicate that the OT configurations is converted into the thermodynamically more stable PEB configurations either by annealing a styrene-adsrobed Ge surface at 340 K or by scanning the Ge surface at high bias voltages. Such conversion of chiral configurations suggests the possibility of the controlled adsorption of chiral molecules on the surface. Therefore, we anticipate that the chiral structures prepared by paired adsorption will provide chiral organic hybrid systems on semiconductor surfaces for potential application to semiconductor-based molecular devices, chiral sensors, and heterogeneous enantioselective catalysis. @FootnoteText@@footnote 1@ Hwang, Y. J.; Kim, A.; Hwang, E.; Kim, S. J. AM. CHEM. SOC. 2005, 127, 5016-5017