One-Electron Theoretical Models

In the simplest one-electron model, is replaced by (p and v /b by (p,, (pj, and (pA being the centers orbitals occupied by the electron when it is on the donor and on the acceptor, respectively. Thus, expression (5) reduces to  

In fact, since the early developments of electron transfer theories, it has been recognized that the magnitude of T b is greatly enhanced if /a and (j/b are delocalized through the intercenter medium [54, 55]. In the framework of one-electron models, this delocalization can be described by a mixing of (pu and (Pa with the medium orbitals which leads to the so-called superexchange contribution. The origin of this contribution may be introduced as follows. If only one medium orbital cPm interacts with both (po and (Pa, the initial and final states may be written  

The electronic factor of the reaction rate is obtained by evaluating (19) and (20) at the nuclear configuration Q = Q where haa bb equal. Expression (20) is readily generalized to a sequence of n orbitals bridging cp and tp. For Q = Q, the main term can be written  

Hiickel method and are evaluated semi-empirically. The reliability of such a procedure cannot be readily assessed, and more elaborate many-electron models are needed to obtain accurate values of T i,. 

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Application of Electron Transfer Theories to Biological Systems 2.2.2 One-Electron Theoretical Models... 

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