Some Electronic and Dynamical Factors in Electron-Transfer Chemistry: Metal Complexes, Clusters, and Surfaces

Some selected concepts involving electronic and dynamical factors in the electron-transfer chemistry of inorganic and organometallic systems are outlined and illustrated by recent results primarily from the authors laboratory, with some emphasis placed on the redox properties of electrochemical interfaces in comparison with molecular reagents. Three interrelated topics are considered. The first concerns the control of electron-transfer rates by an interplay between donor-acceptor electronic coupling and nuclear dynamics. The role of the solvating medium in limiting the barrier-crossing frequency solvent friction effects is described, and the diagnostic capabilities and limitations of this phenomenon for probing the degree of electronic coupling by tuning the reaction dynamics are noted. Secondly, the behavioral differences anticipated between the kinetic properties of molecular redox reagents and electrode surfaces are discussed. A formalism is described for this purpose which intercompares homogeneous-phase and heterogeneous rate data on a unified basis, and is utilized in some illustrative experimental comparisons. Thirdly, the infrared spectroelectrochemical properties of high-nuclearity platinum carbonyl clusters in nonaqueous solvents are outlined in comparison with the potential-dependent properties of monocrystalline platinum electrode analogs.