Electrochemistry for chiral recognition

The ubiquitous nature of chiral molecules means that they are of great interest both for fundamental research and for more applied fields requiring pure enantiomers. They can be found in everything from butterfly wings to medicines and perfume aromas. What's special about these molecules is that they exist in two virtually identical forms, known as enantiomers. The enantiomers of a chiral molecule have the same chemical composition, but differ in the spatial arrangement of a group of atoms. This small difference has important consequences. For example, in the case of drugs, while one enantiomer has the desired effect, the other enantiomer may have no effect at all, or a completely different (potentially toxic) activity. The same applies to aromas, for which limonene is a good example. D-limonene has more of a citrus scent, while L-limonene is more likely to be found in pine or mint oils.

The study of chirality therefore has a wide range of interests. Enantiomers, because of their extremely close chemical formulas, have similar physico-chemical properties. It is therefore complicated to synthesize them specifically or to separate them efficiently. Numerous methods and technologies have been developed to understand this phenomenon and control the synthesis and detection of these compounds. Chromatographs are widely used to analyze and separate two enantiomers. Numerous asymmetric synthesis routes have also been developed, such as chiral ligand- or catalyst-assisted synthesis, surface modification of a material by adsorption of chiral molecules, or molecular imprinting in polymer matrices.

This paper proposes a new technology using a range of electrochemical methods to detect and generate chirality. Electrochemical enantioselectivity is based on the use of selective mesoporous electrodes. These electrodes are obtained by electrodepositing a platinum film from an electrolyte containing the metal salt, as well as a surfactant and the chiral molecule, which act as molecular molds. The ratio of surfactant to water must be controlled so that the surfactant forms self-assembled supramolecular columns perpendicular to the substrate surface, between which the platinum is deposited. In this way, a mesoporous platinum electrode containing chiral information is obtained. The molecular molds are removed by immersing the electrode in water. The electrodes obtained in this way are then used as working electrodes. They can be used to observe the selective oxidation or reduction of an enantiomer by voltammetry. They can also be used for asymmetric synthesis of a prochiral molecule. The molecule is introduced into the chiral cavities, and its conversion (oxidation or reduction) is selective, depending on which enantiomer has been imprinted in the metal. Recently, an enantiomeric excess...