Surface Structure-Sensitive Enantioselectivity: Aspartic Acid Reaction Kinetics on All Surfaces Vicinal to Cu(111)

Abstract

Enantioselective reactions on chiral, single-crystal metal surfaces can provide novel insight into the origins of enantioselectivity in chiral molecular adsorption and catalysis. Using a high-throughput approach to study the surface of a spherical Cu single crystal, we have measured the surface reaction kinetics of aspartic acid decomposition on 169 different Cu(hkl) crystal planes vicinal to the Cu(111) orientation. These span both R- and S-surface chiralities comprehensively. The decomposition kinetics of d- and l-aspartic acids were measured and their decomposition rate constants were estimated on all 169 different surface orientations. The half-times, t1/2(hkl), for the decomposition of aspartic acid reveal that the reactivity for both enantiomers is lower along achiral directions exposing surfaces with (100) step edges than the reactivity along directions exposing surfaces with (110) step edges. The orientation-resolved rate constants, k(hkl), clearly reveal structure sensitivity on surfaces vicinal to Cu(111) but enantiospecificity is only observed for the initiation rate constant, ki(hkl).