Fundaments of Photoinduced Electron Transfer in Inorganic Molecular Systems

AbstractPhotoinduced electron transfer (PET) is a general scientific terminology that can represent physicochemical phenomena and also a broad field of research. As a type of reaction, it can be regarded as an electron transfer between molecules (or molecules and heterogeneous substrates) after electronic excitation of one of them using light. The phenomenon is well understood after many years of development and it can be interpreted by the application of theories that describe the photo-physics of excitation and electron transfer theoretical models. It has evolved through time as a new field of multidisciplinary research gathering physicists, chemists, and biologists. Its present challenge is related to energy conversion since the actual mechanism of natural photosynthesis is yet to be disclosed and artificial photosynthesis still has technological obstacles to be circumvented.Some boundary conditions were used in conceiving this chapter. Firstly, it is not a review of the literature and its main objective is to give an overview of the most important ideas and concepts involved in the field, in an introductory form. Consequently, in order to keep the text more conceptual, we present the key equations without any complex mathematical deduction. We start with the presentation of electron transfer models because these theories are more general and can be applied to problems involving all sorts of molecules (and solids) in any electronic state. In the sequence, electron transfer meets photoexcitation of molecules and we conclude the chapter with some selected examples in which PET is applied to photosynthesis and energy conversion. Examples are restricted to molecular inorganic compounds. By no means this is an indication that this class of compounds is more important, and other examples like organic, supramolecular, and heterogeneous systems will be discussed in other chapters of this handbook.KeywordsPhotoinduced electron transferElectron transferArtificial photosynthesisPhotoinduced proton-coupled electron transferH2O oxidationCO2 reduction