Preparing and testing in potentiometric setups self-standing chiral membranes consisting of open and cyclic “inherently chiral” thiophene-based oligomers

Recently, the “inherent chirality” strategy has been displaying more and more impressive enantiodiscrimination manifestations in chiral electroanalysis and electrochemistry experiments. Such a strategy implies the use of chiral molecular selectors in which the same element, usually the whole main molecular backbone featuring a tailored torsion, is the source of both chirality and key functional properties; moreover, regioregular design can enable propagation and amplification of the peculiar features of a single unit in macro and supramolecular structures. After having successfully implemented inherent chirality in electrode surfaces and, as an alternative, in ionic liquid media or related additives, we are now adding a new interesting tool in the growing palette of “inherently chiral” selectors, by introducing enantiopure self-standing membranes prepared by electrodeposition from enantiopure thiophene-based inherently chiral monomers followed by film detachment from the electrode support. Such membranes consist of a mixture of both open and cyclic oligomers, mainly dimers and trimers, in tunable ratio according to the electrodeposition conditions, as accounted for by high resolution LDI analysis. The membranes have been also characterized in terms of IR features and their morphology was carefully studied by SEM, TEM and AFM. As a preliminary investigation of functional properties, racemate membranes were implemented in a ISE-like setup, performing potentiometric tests with various achiral electrolytes at different concentrations; reliable transmembrane potential readings were obtained, quite consistent with those predicted considering the membrane and cell features.