Kinetics electron transfer, counterion effects

Salt effects have been studied for a large number of electron-transfer reactions. The effect of extremely dilute salt solutions can in most cases be accounted for by the Debye-Hiickel formalism, whereas explanations for more concentrated solutions vary. Among these are the associative nature of reactants and counterions as well as specific kinetic effects such as cation bridges between redox pairs to facilitate electron transfer. 

The kinetics of electron-exchange and electron-transfer reactions involving the optically active [Co(phen)3] + +, [Co(4,7-Me2phen)3] +, and [Co(5,5-Me2phen)3] couples have been studied. The self-exchange rate constants were observed to be dependent on the nature of the counterion, with an acceleration effect in the order CIO >N07 >Br >C1 , and the formation of ion multiplets is proposed. Flash photolysis kinetic measurements on the oxidation of several cobalt(II) polyaza macrocycles by [Ru(bpy)3] + and [Cr(bpy)3] + have been reported. ... 

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