Solvent Isotope Effects Upon the Kinetics of some Simple Electrode Reactions.
MICHIGAN STATE UNIV EAST LANSING DEPT OF CHEMISTRY
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The effect of replacing H2O with D2O solvent upon the electrochemical kinetics of simple transition-metal redox couples containing aquo, ammine, or ethylenediamine ligands have been investigated at mercury electrodes as a means of exploring the possible contribution of ligand-aqueous solvent interactions to the activation barrier to outer-sphere electron transfer. Comparison of isotope rate ratios for corresponding electrochemical and homogeneous outer-sphere reactions involving cationic ammine and aquo complexes yields values of isotopic rate ratios of hydrogen and deuterium for the former processes that are typically markedly larger than those predicted by the Marcus model from the homogeneous rate ratios. These discrepancies appear to arise from differences in the solvent environments in the transition states for electrochemical and homogeneous reactions.
- Physical Chemistry