Electron transfer

Under an electron transfer is the transfer of an electron between two spatially separated centers on the basis of quantum-mechanical transitions. This is a central process of energy transfer on the microscopic scale that is relevant for the chemical ( binding and excitation in molecular systems ), building on the biology and for the physics and, based in technologically relevant processes of materials science (eg B. semiconductor industry). Depending on the field are related to the concept of electron transfer other aspects.

In chemistry it is called electron transfer reaction (including electron transfer reactions) in response to the electron transfer, so rather the macroscopically tangible initial and final ( and includes for example any approach, such as diffusion of the centers with a ).

In biology, the Zusammanspiel of electron transfer and the heterogeneous molecular environment importance for the complex processes in biological processes, and will be summarized here as the electron transport chain.

Even in electronic components of the quantum mechanical electron transfer plays a central role on the microscopic scale. However, specific quantum mechanical effects are due to the size of components and the number of involved electrons and atoms generally involves. no role and is referred to as electron transport or from the macroscopically measurable current. But as soon as a boundary is involved, occur microscopic processes that are described by the solid-state physics and, for example, are important in semiconductor technology or solar technology.

Classifications (chemistry)

One distinguishes the homogeneous from heterogeneous electron transfer. The former identifies the exchange within two chemical species ( for example, two molecules ). The heterogeneous electron transfer between an electrode and the electron chemical species is exchanged. The electron donor (short donor) are in this case on an electron to the acceptor as mentioned.

Are the donor and acceptor in a chemical species, as referred to the electron transfer as intramolecular. However, if an electron between two species exchanged, it is called this form the intermolecular electron transfer.

If the electron transfer the chemical mechanism, the redox behavior of the species is a consequence of the same. The electron donor is oxidized at the time of electron transfer ( so increasing its oxidation state ), whereas the acceptor is reduced (that is, its oxidation number decreases ).

Physical chemistry of electron transfer

Kinetic theories, such as the Marcus theory, try the rate of electron transfer reactions interpreted as a consequence of thermodynamic state functions. Quantitative predictions are possible by means of models known today only in rare cases. This is particularly the description by the enormous number of poorly measurable values ​​on the one hand and the complexity of the externally seemingly simple mechanism on the other. More modern models attempt a consistent integration of the diffusion process in theories of elementary process. Of importance here are the Kramer- theories and theories Encounter.

Experimental methods for the study of electron transfer are mainly magnetic resonance methods (eg electron spin resonance), relaxation techniques ( eg, laser spectroscopy) and electrochemical methods (often mentioned in combination with the other methods ).