Reorganization factor, intrinsic

Results from the dissociative reduction of aryl ethers led to a number of important generalizations. These are classical stepwise systems initially forming jr -type radical anions. In this case, the intrinsic barriers for the formation of the intermediate radical anions are dominated by solvent reorganization with only a small (sometimes negligible) contribution from internal reorganization. Thus, the ETs to these systems are properly described by Marcus theory, in which the harmonic approximation satisfactorily accounts for both outer and inner reorganization factors. On the... 

The forward and backward activation free energies and the corresponding rate constants thus depend on an extrinsic factor, the standard free energy of the reaction, AG° = E — E°, and an intrinsic factor, the standard activation free energy, that reflects the solvent and internal reorganization energy, Aq and A [equation (1.31)]. 

In semiclassical ET theory, three parameters govern the reaction rates the electronic couphng between the donor and acceptor (%) the free-energy change for the reaction (AG°) and a parameter (X.) related to the extent of inner-shell and solvent nuclear reorganization accompanying the ET reaction [29]. Additionally, when intrinsic ET barriers are small, the dynamics of nuclear motion can limit ET rates through the frequency factor v. These parameters describe the rate of electron transfer between a donor and acceptor held at a fixed distance and orientation (Eq. 1),... 

Finally, it may be useful to note that the Fermi golden rule and time correlation function expressions often used (see ref. 12, for example) to express the rates of electron transfer have been shown [13], for other classes of dynamical processes, to be equivalent to LZ estimates of these same rates. So, it should not be surprising that our approach, in which we focus on events with no reorganization energy requirement and we use LZ theory to evaluate the intrinsic rates, is closely related to the more common approach used to treat electron transfer in condensed media where the reorganization energy plays a central role in determining the rates but the z factor plays a second central role. 

Another approach is to measure the redox potential at different temperatures and to calculate AH° and AS0. However, these thermodynamic terms also depends on both protein intrinsic factors and solvent reorganization effects. In general, the... 

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