INTRINSIC BARRIER REORGANIZATION ENERGY

As with the Marcus-Hush model of outer-sphere electron transfers, the activation free energy, AG, is a quadratic function of the free energy of the reaction, AG°, as depicted by equation (7), where the intrinsic barrier free energy (equation 8) is the sum of two contributions. One involves the solvent reorganization free energy, 2q, as in the Marcus-Hush model of outer-sphere electron transfer. The other, which represents the contribution of bond breaking, is one-fourth of the bond dissociation energy (BDE). This approach is... 

The solvent reorganization energy, 70, is expected to be small, as discussed elsewhere, giving rise to a term 70 /4 on the order of 0.15 and 0.1 eV for the chloro and bromo series, respectively. The predicted values of the intrinsic barrier are thus 1.23 and 1.03 eV for the chloro and bromo derivatives, respectively (i.e., much larger than the experimental values). 

Symbolized by A, the reorganization energy of a one-electron transfer reaction is that energy needed for all structural adjustments, not only in the two reactants but in the neighboring solvent molecules as well, required for the two reactants to assume the correct configuration needed to transfer the sole electron. See Intrinsic Barrier Marcus Equation... 

REORGANIZATION ENERGY INTRINSIC BARRIER MARCUS EQUATION Repeatability,... 

There are a number of problems associated with measuring bimolecular rate constants for ET. Only a small set of data can be obtained. In addition, since a wide range of donor anion radicals is used, there are variations in the reorganization energies that influence local curvature (and thus intrinsic barrier equation 53) for each point. In principle, electrochemical measurements such as those described in Section 2 can provide similar information. 

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