Chiral templating of surfaces: adsorption of (S)-2-methylbutanoic acid on Pt(111) single-crystal surfaces.
The adsorption and thermal chemistry of (S)-(+)-2-methylbutanoic acid ((S)-2MBA) on Pt(111) single-crystal surfaces was characterized by using temperature programmed desorption (TPD) and reflection-adsorption infrared (RAIRS) spectroscopies. Particular emphasis was placed on the characterization of the chiral superstructures formed upon the deposition of the submonolayer coverages of enantiopure (S)-2-methylbutanoate species that are produced by thermal dehydrogenation of the (S)-2MBA. The enantioselectivity of the empty platinum sites left open on those structures were identified by their difference in behavior toward the adsorption of the two enantiomers of propylene oxide. It was found that a significant enhancement in adsorption is possible on surfaces with the same chirality of the probe molecule, specifically that the uptake of (S)-propylene oxide is larger than that of (R)-propylene oxide on (S)-2-methylbutanoate adsorbed layers. This contrasts with the lack of enantioselectivity previously reported for the same adsorbate on Pd(111). Detectable differences in adsorption energetics of (R)- vs (S)-propylene oxide on the (S)-2-methylbutanoate/Pt(111) overlayers were measured but deemed not to be the controlling factor in the enantioselectivity reported in this system.
Lee
Ilkeun
I
Department of Chemistry, University of California, Riverside, California 92521, USA.
Zaera
Francisco
F
D000327:Adsorption; D002087:Butyrates / Q000737:chemistry*; D003460:Crystallization; D010984:Platinum / Q000737:chemistry*; D013237:Stereoisomerism; D013499:Surface Properties; D013696:Temperature
D002087:Butyrates; D010984:Platinum; C019475:2-methylbutanoic acid