Structure, Selectivity, and Solvation of a Model Chiral Stationary Phase

• Published in: The journal of physical chemistry. B 2004-03, Vol.108 (11), p.3512-3522
• Main Authors: Nita, S, Cann, N. M, Horton, J. H
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp0365615

The presence of chirality at an interface enables a surface to distinguish between enantiomers. The mechanism by which this selectivity occurs is complicated by the surface morphology, the possible involvement of the solvent, and the characteristics of the chiral molecules at the surface. In this article, atomic force microscopy (AFM), chemical force titrations, density functional theory, and molecular dynamics simulations are employed to examine surfaces terminated by (S)- and (R)-N-(1-phenylethyl)-N‘-[3-(triethoxysilyl)propylurea (PEPU). A “brush-type” chiral interface is formed by attaching the PEPU molecules to either an oxidized poly(dimethylsiloxane) or oxidized Si(111) substrate. Using AFM, the morphologies of the resulting chiral surfaces are obtained. Chemical force measurements of the chiral selectivity in the presence of water, methanol, hexane, and CS2 have been performed. Ab initio studies provide descriptions of the hydrogen bonding between PEPU molecules at the interface. Molecular dynamics simulations are employed to examine the distribution of water, methanol, and CS2 near PEPU interfaces.