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Abstract:
Imparting chirality to non-chiral metal surfaces by adsorption of chiral modifiers is a highly promising
route to create effective heterogeneously catalyzed processes for the production of enantiopure
pharmaceuticals. One of the major current challenges in heterogeneous chiral catalysis is the
fundamental-level understanding of how such chirally-modified surfaces interact with chiral and
prochiral molecules to induce their enantioselective transformations. Herein we report the first direct
calorimetric measurement of the adsorption energy of chiral molecules onto well-defined chirally-modified
surfaces. Two model modifiers 1-(1-naphthyl)ethylamine and 2-methylbutanoic acid were used to impart
chirality to Pt(111) and their interaction with propylene oxide was investigated by means of single-crystal
adsorption calorimetry. Differential adsorption energies and absolute surface uptakes were obtained for the
R- and S-enantiomers of propylene oxide under clean ultrahigh vacuum conditions. Two types of
adsorption behavior were observed for different chiral modifiers, pointing to different mechanisms of
imparting chirality to metal surfaces. The results are analyzed and discussed in view of previously reported
stereoselectivity of adsorption processes
