Electron Transfer Processes

Abstract

Electron transfer processes are at the core of all oxidation–reduction reactions, including those associated with electrochemistry and corrosion. Photoelectrochemistry and solar energy conversion, organic light emitting diodes, and molecular electronic devices, all dominated by electron transfer and electron transmission in molecular systems, are presently subjects of intensive research at the interface of science and technology. Similarly, electron transfer processes constitute fundamental steps in important biological phenomena such as photosynthesis and vision. This chapter is an introduction to the general phenomenology and theoretical concepts associated with these processes. Electron transfer is one of the most important, and most studied, elementary chemical processes. This most fundamental oxidation–reduction process lies at the core of many chemical phenomena ranging from photosynthesis to electrochemistry and from the essential steps governing vision to the chemical processes controlling corrosion. As other molecular phenomena that involve charges and charged particles, the natural environment for such processes is a polar solution; the solvation energy associated with the polarization of the environment is a major component in the energetics of such processes. Noting that in vacuum typical molecular ionization potentials are of the order of (100–400)kBT for T = 300 K, it appears that the stabilization of ionic species by the solvent environment is the reason why electron transfer processes in solution can take place at room temperature. When we try to go beyond this general statement, questions arise.