Molecular Origins of Chiral Amplification on an Achiral Surface: 2D Monolayers of Aspartic Acid on Cu(111)

Abstract

Recent experiments have demonstrated an intriguing phenomenon in which adsorption of a nonracemic mixture of aspartic acid (Asp) enantiomers onto an achiral Cu(111) metal surface leads to autoamplification of surface enantiomeric excess, ee s , to values well above those of the impinging gas mixtures, ee g . This is particularly interesting because it demonstrates that a slightly nonracemic mixture of enantiomers can be further purified simply by adsorption onto an achiral surface. In this work, we seek a deeper understanding of this phenomena and apply scanning tunneling microscopy to image the overlayer structures formed by mixed monolayers of d - and l -Asp on Cu(111) over the full range of surface enantiomeric excess; ee s = −1 (pure l -Asp) through ee s = 0 (racemic dl -Asp) to ee s = 1 (pure d -Asp). Both enantiomers of three chiral monolayer structures are observed. One is a conglomerate (enantiomerically pure), another is a racemate (equimolar mixture of d - and l -Asp); however, the third structure accommodates both enantiomers in a 2:1 ratio. Such solid phases of enantiomer mixtures with nonracemic composition are rare in 3D crystals of enantiomers. We argue that, in 2D, the formation of chiral defects in a lattice of one enantiomer is easier than in 3D, simply because the stress associated with the chiral defect in a 2D monolayer of the opposite enantiomer can be dissipated by strain into the space above the surface.

Biochemical Behavior, Influence on Cell DNA Condition, and Microbiological Properties of Wool and Wool–Copper Materials

“…These reactivities of metallic copper were summarized and illustrated recently [ 32 ]. Physio-chemical investigations on the chemisorption of amino acids and peptide on copper phases have been the subject of numerous reports [ 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 , 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 ]. Their summed information is listed in Supplemental Information Table S1 and presented schematically in Figure 3 .…”

“…The following supporting information can be downloaded at: , Table S1: Chemisorption of amino acids [ 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 ] and peptides [ 157 , 158 , 159 , 160 , 161 , 162 , 163 , 164 , 165 ] on copper phase.…”

From Short‐ to Long‐Range Chiral Recognition on Surfaces: Chiral Assembly and Synthesis

“…A great number of chiral assemblies have been studied on metal surfaces, including 0D chiral clusters, [ 24–27 ] 1D chiral chains, stripes or lines, filaments, wires [ 28–34 ] and 2D chiral islands, lamellas structures and honeycomb or more complex nontrivial architectures (chiral Kagome networks, quasicrystals, Sierpiński triangle fractals and semi‐regular Archimedean tilings) [ 33–58 ] that may possess intriguing physical and chemical properties. Most of these chiral nanostructures are achieved through short‐range chiral recognition induced by non‐covalent intermolecular interactions, such as hydrogen bonding, [ 24,28,30,31,34–42 ] halogen bonding, [ 33,43–46 ] van der Waals (vdW) forces, [ 47 ] dipole–dipole interactions, [ 48 ] metal‐organic coordination [ 33,49–51 ] or cooperative interactions of two or more sorts of intermolecular forces.…”