Intramolecular reaction solvent viscosity dependent

The outer-sphere electron transfer reaction between [Fe(CN)6] and [Co(NH3)5H20] has been studied as a function of temperature and pressure in a variety of water-glycerol solvent mixtures. While AV remains essentially constant at 28 cm moP both A/f and A5 increase with an increase in the viscosity of the solvent. The intramolecular electron transfer processes in (NH3)5CoLFe(CN)5 complexes, where L is 3,3 -dimethyl-4,4 -bipyridine, 4,4 -bipyridylacetylene, 2,7-diazapyrene, and 3,8-phenathroline, have been studied. The activation free energies display an inverse dependence on the Fe-Co distance and, when corrected for solvent reorganization energies, are relatively constant at 14.0 0.5 kcal moP. ... 

This analysis concerns for instance the formation of the twisted intramolecular charge transfer state, the photoisomerization processes, etc... in solution for which the intramolecular motion is related with the solvent motion. The unimolecular reaction -the passage from the reactant well to the product well in the Kramers treatment- is modeled by a sink term depending on the reaction coordinate. In the high-viscosity case the motion is governed by the modified Smoluchowski equation [6 ]... 

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