Manipulating Self-Assembly with Achiral Molecules:  An STM Study of Chiral Segregation by Achiral Adsorbates

The self-assembly of a mixture of hexadecanoic acid with racemic (R)/(S)-2-bromohexadecanoic acid has been investigated using scanning tunneling microscopy. When this mixture is physisorbed onto the basal plane of graphite, hexadecanoic acid controls the resultant two-dimensional structure. By self-...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2000-08, Vol.104 (32), p.7627-7635
Main Authors: Yablon, Dalia G, Giancarlo, Leanna C, Flynn, George W
Format: Article
Language:English
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Summary:The self-assembly of a mixture of hexadecanoic acid with racemic (R)/(S)-2-bromohexadecanoic acid has been investigated using scanning tunneling microscopy. When this mixture is physisorbed onto the basal plane of graphite, hexadecanoic acid controls the resultant two-dimensional structure. By self-assembling on a graphite substrate into two distinct domains exhibiting nonsuperimposable mirror image morphology, achiral hexadecanoic acid induces the segregation of 2-bromohexadecanoic acid into enantiomerically pure (R and S) domains. The 2-bromohexadecanoic acid molecules provide convenient markers to directly differentiate the 2D chiral domains of inherently achiral hexadecanoic acid. The pattern in which hexadecanoic acid assembles with enantiomerically pure 2-bromohexadecanoic acid is shown to be more energetically favorable than a monolayer in which the unsubstituted fatty acid is mixed with both chiral isomers of 2-bromohexadecanoic acid.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp994414u