Enantioselective selectors for chiral electrochemistry and electroanalysis : stereogenic elements and enantioselection performance

The ability to select among different electroactive molecules, or among different redox centers on a single molecule, in both analytical and synthetic applications, is a typical asset of electrochemistry, based on fine control of the electrode potential, possibly enhanced by the choice of appropriate electrode surfaces and media. An attractive step further, of great fundamental and applicative interest, is represented by enantioselective electrochemistry, implying the ability to discriminate the enantiomers of chiral molecules (in electroanalysis), or to selectively activate or achieve a given enantiomer of a chiral molecule controlling the electrode potential (in electrosynthesis). Since the enantiomers of a chiral molecule have identical scalar physico-chemical properties and therefore the same electrochemical behavior except when interacting with some other chiral entity, enantioselective electrochemistry necessarily implies the electron transfer process to take place in asymmetric conditions. This can be achieved by the use of a chiral electrode surface or a chiral medium. Artificial selectors are particularly interesting on account of the virtually unlimited range of tailored structures possible as well as the possibility to have both enantiomers of a given selector equally available. Among the many approaches so far proposed for this ambitious target along either of the two above ways, outstanding results have been recently obtained, based on the use of "inherently chiral molecular materials" (either as electrode surfaces or as media) in which the same structural element endows the molecule with both its key functional property and with chirality.