Ion pairing effects on the kinetic of the intramolecular electron transfer reaction [FeII(CN)5pzCoIII(NH3)5] → [FeIII(CN)5pzCoII(NH3)5]

The kinetics of the title reaction was studied in different salt solutions (NaNO3, LiNO3, Ca(NO3)2 and Na2SO4). The results are interpreted as a consequence of ion pairing effects. It has been shown that the anion of the salts is the ion associating with the binuclear complex. This association of the anion produces a less favorable reaction free energy and consequently a diminution of the reaction rate.