Redox and Photochemical Reactions at the Interface Between Immiscible Liquids

Abstract

One of the important specific features of the interface between immiscible liquids — ionic conductors — is the fact that, for the reaction of electron transfer across the interface to occur, electron donors and acceptors must be present in the contacting phases. Artificial systems of immiscible liquids in which redox processes occur are as yet only a subject of investigation [1–3]. In nature, however, the redox reactions occurring in the membrane/electrolyte system are quite widespread [4]. For instance, the energy conversion processes in the respiratory chain of mitochondria or energy storage in photosynthesis represent a chain of redox transformations taking place on a mitochondrial or photosynthetic membrane. From an electrochemical point of view, the membrane on which redox transformations take place represents for the electron a thin insulating layer consisting of two monolayers of lipids oriented with their hydrophobic tails towards each other. Electron donors or acceptors can be immersed in this lipid matrix, as well as the enzymes catalyzing the redox transformations [1]. As a rule, the attempts to investigate experimentally the redox transformations involving protein enzyme systems are faced with difficulties since an artificial bilayer is not everywhere capable of withstanding mechanically the adhesion to its surface of high-molecular enzyme systems. Nevertheless, on the bilayers it is possible to effect redox transformations involving both relatively low-molecular compounds and membrane protein complexes [5–8].