"Inherently chiral" electrode surfaces: stereogenic elements and enantiodiscrimination performances

Electrochemical processes are intrinsically "intelligent" on account of the selectivity achievable in both analytical and preparative contexts through fine control of the electrode potential. They can become even smarter by addition of chirality, implying to discriminate between enantiomers of chiral electroactive probes, which requires the electron transfer process to take place at an enantiopure chiral interphase.[1,2] A recently proposed groundbreaking strategy is based on the use of heterocycle-based "inherently chiral" molecular selectors, i.e. with chirality and key functional properties originating from the same structural element, which coincides with the main molecular backbone, featuring a tailored torsion with associated energy barrier too high to be overcome at room T. This concept has been successfully implemented by us in both electrode surfaces[3-10] and in ionic-liquid based media.[11,12] We will particularly focus on preparation, features and performances of enantiopure electrode surfaces obtained starting from enantiopure monomers with atropisomeric 3,3'-bithiophene or 2,2'-biindole cores and oligothiophene wings[3-9] or from enantiopure helical monomers (tetrathiahelicenes).[10] By fast and regular electrooligomerization enantiopure inherently chiral films are obtained, often including attractive cyclic terms, with high electroactivity and, above all, impressive enantiodiscrimination ability as general-scope electrode surfaces in terms of large potential differences for the enantiomers of very different chiral probes, also of pharmaceutical interest. The film impressive enantioselectivìty also holds with circularly polarized light and electron spins, resulting in outstanding chiroptical and spin filter performances, suggesting fascinating correlations between the three contexts.[2,8-10] Acknowledgements: The support is gratefully acknowledged of Regione Lombardia and Fondazione Cariplo (Avviso congiunto per l’incremento dell’attrattività del sistema di ricerca lombardo e della competitività dei ricercatori candidati su strumenti ERC-edizione 2016, Project 2016-0923). [1] Curr. Opin. Electrochem. 2018,7,188; [2] Curr. Opin. Electrochem. 2018,8,60; [3] Angew. Chem., 2014, 53,2623; [4] Chem. Eur J. 2014,20,15298; [5] Chem. Sci. 2015,6,1706; [6] Anal. Bional. Chem. 2016,408,7243; [7] Chem. Eur J. 2016, 22, 10839; [8,9] Chem. Sci under revision 2018; [10] Chem. Sci. accepted 2018 [11] Angew. Chem. 2017,56,2079; [12] Electrochem. Comm. 2018,89,57.