Adsorption differences between low coverage enantiomers of alanine on the chiral Cu{421}R surface

Dynamic Diastereomerism on Chiral Surfaces

Adsorption of chiral molecules on chiral surfaces implies diastereomerism, evident in the adoption of distinct adsorption geometries. We show here that this diastereomerism produces a signature in the motion of chiral molecules desorbing from a chiral surface. The rotations of S- and R-alanine molecules are analyzed upon desorption from R-Cu{531} using first-principles molecular dynamics simulations. S-Ala molecules exhibit a larger angular momentum, with a clear preference for one rotational sense, whereas no such preference is observed for R-Ala molecules upon desorption from this surface. These trends would be reversed for desorption from the S-Cu{531} surface. Possible applications include chiral separation techniques and enantiospecific sensors.

XPS as a Probe for the Bonding Nature in Metal Acetates

Metal carboxylates are an extensive family of coordination compounds of growing importance in Materials Science; hence, there is a need for improving the characterization methods for these complexes, especially at...

Chiral Surface and Geometry of Metal Nanocrystals

Chirality is a basic property of nature and has great importance in photonics, biochemistry, medicine, and catalysis. This importance has led to the emergence of the chiral inorganic nanostructure field in the last two decades, providing opportunities to control the chirality of light and biochemical reactions. While the facile production of 3D nanostructures has remained a major challenge, recent advances in nanocrystal synthesis have provided a new pathway for efficient control of chirality at the nanoscale by transferring molecular chirality to the geometry of nanocrystals. Interestingly, this discovery stems from a purely crystallographic outcome: chirality can be generated on high-Miller-index surfaces, even for highly symmetric metal crystals. This is the starting point herein, with an overview of the scientific history and a summary of the crystallographic definition. With the advance of nanomaterial synthesis technology, high-Miller-index planes can be selectively exposed on metallic nanoparticles. The enantioselective interaction of chiral molecules and high-Miller-index facets can break the mirror symmetry of the metal nanocrystals. Herein, the fundamental principle of chirality evolution is emphasized and it is shown how chiral surfaces can be directly correlated with chiral morphologies, thus serving as a guide for researchers in chiral catalysts, chiral plasmonics, chiral metamaterials, and photonic devices.

Theoretical investigation of amino-acid adsorption on hydroxylated quartz surfaces: dispersion can determine enantioselectivity

Chiral mineral surfaces, such as quartz, are attractive substrates for use in enantioselective separation and may have contributed to the origin of biological homochirality. In this work, we apply density-functional theory and the exchange-hole dipole moment (XDM) dispersion model to study the adsorption of 5 amino acids (glycine, serine, alanine, valine, and phenylalanine) on a hydroxylated α-quartz (0001) surface. It is demonstrated that London dispersion is responsible for 30-50% of the total adsorption energies and its inclusion or omission can reverse predictions of enantioselectivity. Differing dispersion stabilization, caused by the opposing side-chain placements relative to the quartz surface, lead to differences of 1.0 and 1.8 kcal mol^-1 in the adsorption energies of the alanine and phenylalanine enantiomers, respectively. These results are consistent with a 3-point model, with the hydrogen-bonding sites conserved and variations in the dispersion interactions determining enantioselectivity.