ABSTRACT
The transfer of an electron from one site to another in a molecule, as well as between molecules or redox centers located in two different phases, is one of the most fundamental and ubiquitous processes in chemistry and biology. For decades researchers have investigated this reaction from both the theoretical and experimental points of view.' There are two crucial questions which need to be dealt with. First, it is important to establish how far an electron can travel between redox sites in a single, concerted reaction. In other words, what role does the distance separating the redox centers play in the kinetics of the electron-transfer events? Second, is there a link between the thermodynamic driving force of the electrontransfer event and the rate at which it occurs? The theoretical analysis of this problem is by no means simple. It has been - and still is - a major challenge for theoreticians to develop models that give satisfactory explanations for all relevant experimental observations and to predict with good accuracy the kinetic characteristics of electron transfer events.
