Electrodeposition of enantioselective inherently chiral electrode surfaces: from traditional media to RTILs

Thiophene-based inherently chiral conducting films, under development in our research group, have very high and stable chiral activity, depending on a tailored torsion of the whole conducting backbone rather than on attached chiral pendants; accordingly, such chirality is modulable by the amount of injected charge (reducing the torsion angle to achieve better system conjugation), a phenomenon which suggested us the image of a breathing system. Perfectly specular electrode surfaces have been prepared by electrodeposition cycles, starting from the corresponding inherently chiral oligomers. To finely discriminate among the racemate and enantiomer film properties, and above all to achieve enantioselective electrode surfaces for applications in the electroanalysis and electrocatalysis domains, reproducibility is a necessary but hard task. In this context, preliminary literature studies [1,2] point to room temperature ionic liquids RTIL, both as such and as co-solvents, significantly improving the regularity and the mechanical and morphological properties of electrodeposited conducting molecular films. In this frame, we have carried out an extensive study aimed to the rationalization of the conducting film features obtained in different conditions (i.e., RTILs vs non polar and polar VOCs, on various electrodes), both on model starting monomers (EDOT and EDOP) and on our newly developed inherently chiral ones. In particular, enantiomer film deposition from RTILs on screen-printed electrodes afforded reproducible and repeatable enantiorecognition ability of the specular electrode surfaces towards specular probes.