Probing Electron-Transfer and Ion-Transfer Coupling Processes at Liquid/Liquid Interfaces with Pipette Electrodes

Electron-transfer (ET) reactions at a liquid/liquid (L/L) interface have attracted much attention because they are relevant to many important chemical and biological processes. At an L/L interface, the ET reaction is usually coupled with an ion-transfer (IT) reaction, and it is difficult to discriminate between them. Despite the great progress that has been made, the nature of the coupling is still unclear and the two proposed mechanisms have been the subject of much debate over the past several decades. Herein, the coupling reactions between ferrocene (Fc) in 1,2-dichloroethane and [Fe(CN)(6)](3-) in water are investigated in detail by using various types of pipette electrodes, and the two mechanisms are clarified with the help of salting-out effects. It is demonstrated that the mechanism which dominates is dependent on the concentration ratio of the redox species in the two phases.