Highlighting spin selectivity properties of chiral electrode surfaces from redox potential modulation of an achiral probe under applied magnetic field

Impressive spin-related effects are observed in cyclic voltammetry (CV) experiments performed under applied magnetic field on a non-ferromagnetic electrode modified with a thin electroactive oligothiophene film, either "inherently chiral" or featuring chiral pendants with stereogenic centres. By flipping the magnet north/south orientation, the CV peaks of two achiral, chemically reversible Fe(III)/Fe(II) redox couples in aqueous or organic solution undergo impressive potential shifts (up to nearly 0.5 V depending on protocol conditions), specularly by changing the film (R)- or (S)-configuration. The magnitude of the potential shift decreases both increasing the polymer film thickness and the distance between the permanent magnet from the electrode surface. Such unprecedented spin-related redox potential modulation, obtained in the absence of a magnetic electrode acting as spin injector, provides a striking evidence (as well as an attractive evaluation criterion) of the spin selectivity properties of chiral thin films.