Aspects of electron transfer at ITIES

Studies involving heterogeneous electron transfer (HET) at the interface between two immiscible electrolyte solutions (ITIES) can reveal many additional interesting features such as decomposition reactions, ion pairing and phase formation. These extra and often unwanted reactions can be linked to the reactivity of the reactants/products of the chosen redox couples and the base electrolytes used in both phases. Conventional cyclic voltammetry is a very useful qualitative tool and has been shown to give important information on the simplicity or complexity of the chosen system. For the three most commonly used organic redox couples 7,7,8,8-tetracyanoquinodimenthane (TCNQ), 1,1-dimethylferrocene (DmFc) and ferrocene (Fc), association in the low permittivity organic phase, the role of the aqueous redox couple and possible electron transfer (ET)–ion transfer (IT) coupling have been considered. Association of the base electrolyte cation with the product of HET between the aqueous redox couple and TCNQ in 1,2-dichloroethane was noted to have a facilitating effect on electron transfer. It has been demonstrated that it is possible to obtain a new phase at the interface either as a consequence of interfacial reactions or precipitation from the aqueous phase due to Gibbs energy coupling.