Intermolecular Interactions and the Theory of Electron Transfer Between Hexaaquoiron Ions and Hexaammineruthenium Ions in Water.

Theoretical studies of the electron transfer rates between hexaaquoiron(II) and (III) ions, and between hexaammineruthenium(II) and (III) ions in aqueous solutions have been undertaken using detailed representations of the interaction potentials and including the flexibility of the ligand geometry. This is done through an intuitive and efficient computational scheme involving tested site-site potentials for water and ammonia. The calculations on the ferrous-ferric electron exchange indicate that fluctuations in the configuration of the hydration shell are important and affect the rate significantly. In the hexaammineruthenium reaction, there is no evidence for any substantial contribution from this factor, although rates tend to be consistently lower than experimental results. This may indicate a weakness in the ammonia-ammonia potential function used or in the treatment of the electronic coupling matrix element