We have two identical hands – almost. They are mirror images, or chiral. Jacob Wright of Empa in Switzerland demonstrated at EUROPACAT2025 that metals can also have such a structure.
Figure 1: Chirality represented by two enantiomers of a chiral molecule, which behave toward each other similarly to the right and left hands. (Image source: Wikipedia)
The surface structure of such crystals can also exhibit chirality. The catalytic scientist is delighted with such a distinctive substrate, because a chiral adsorbate will also take over the configuration. And this is the dream of fine chemical catalysis: producing enantiomerically pure substances, selecting the cis-trans configuration, and producing R- or S-pure substances. An example of a prochiral, larger organic molecule on a chiral metal interface is shown in the second image.
Figure 2: Non-contact AFM image of R- and S-enantiomer complex of 9-ethynylphenanthrene on chiral PdGa:B(111) surface.
Special alloy mixtures, namely intermetallic compounds of the crystalline space group 198, such as PdGa, PtAl, etc., result in the same type of mirror symmetry breaking as in our hands. These metals exhibit chirality, and research is currently underway to use them as chiral-selective catalysts in surface reactions. All volume-terminated surfaces are chiral and, with a similar electronic structure, exhibit various geometric arrangements that can be used for specific reactions. Courtesy of Empa Switzerland – nanotech@surfaces – Chiral Surfaces; Contact: jacob.wright@empa.ch.
To read more:
– Samuel Stolz, doctoral thesis “Exploiting the chirality of intermetallic PdGa“, EPFL (2020); https://infoscience.epfl.ch/entities/publication/6f335d94-f9af-45d1-a649-067b23662143
– S. Stolz, et al. “Asymmetric azide-alkyne Huisgen cycloaddition on chiral metal surfaces“, Communications Chemistry 4, 51 (2021)
