18943-33-4Relevant articles and documents
Electrocatalysis at Redox Polymer Electrodes with Separation of the Catalytic and Charge Propagation Roles. Reduction of O2 to H2O2 as Catalyzed by Cobalt(II) Tetrakis(4-N-methylpyridyl)porphyrin
Anson, Fred C.,Ni, Chin-Long,Saveant, Jean-Michel
, p. 3442 - 3450 (1985)
The kinetics of the reduction of O2 by Ru(NH3)6(2+) as catalyzed by cobalt(II) tetrakis(4-N-methylpyridyl)porphyrin are described both in homogeneous solution and when the reactants are confined to Nafion coatings on graphite electrodes.The catalytic mechanism is delineated and the factors that can control the total reduction currents at Nafion-coated electrodes are specified.A kinetic zone diagram for analyzing the behavior of catalyst-mediator-substrate systems at polymer-coated electrodes is presented and utilized in identifying the current-limiting processes.Good agreement is demonstrated between calculated and measured reduction currents at rotating disk electrodes.The experimental conditions that will yield the optimum performance of coated electrodes are discussed, and a relationship is derived for the optimal coating thickness.
Endicott, J. F.,Taube, H.
, p. 1686 - 1691 (1964)
Charge-Transfer Perturbations of the Electronic Contributions to Electron-Transfer Reactions. Enhanced Donor-Acceptor Couplings Mediated by Coordinated Ligands
Endicott, John F.,Ramasami, T.
, p. 3740 - 3747 (2007/10/02)
The factors contributing to variations in the adiabaticity of a series of Co(III)-Co(sep)(2+) (sep= (S)-1,3,6,8,10,13,16,19-octaazabicycloeicosane) cross-reactions have been investigated.Coordinated ligands can be effective in making the electron-transfer rates more adiabatic by altering the electronic structure of the complex and/or by contributing to intermolecular charge-transfer interactions.Alterations of the coordinated ligands change both the ligand field and the charge-transfer excited states of the Co(III) acceptor, and the contributions of each kind of excited state perturbation must be considered in evaluating rate patterns.For Co(NH3)5X(2+) oxidants, the inferred values of the electronic transmission coefficient, κel, increase systematically through the series X=CN, Cl, Br, N3, and I with the smallest value of κel being ca. 10-3 and the largest approaching unity.Simple models are proposed which account for the variations in κel based on the perturbational effects of ligand to metal charge transfer and triplet ligand field excited states on the electron exchange integral coupling reactants and products.
Kinetics of the hexaammineruthenium(II)-(ethylenediaminetetraacetato)iron(III) reaction. A relative Marcus theory evaluation
Moattar,Walton, John R.,Bennett, Larry E.
, p. 550 - 553 (2008/10/08)
Kinetic parameters for the outer-sphere reaction between Ru(NH3)62+ and Fe(EDTA)- have been determined at I = 1.00 M: k = (2.2 ± 0.2) × 106 M-1 s-1 (25°C), ΔH? = 3.6 ± 0.3 kcal mol-1, and ΔS? = -17 ± 1 eu. With the reported variation of k with I, these results provide the basis for a detailed evaluation of the Marcus cross-reaction relationships for ΔG?, ΔH?, and ΔS?. At I = 0.00 M the agreement with extrapolated experimental results is excellent when the work terms are taken properly into account. Major components of the substantial corrections they provide to ΔG0?, ΔH0?, and S0? are attributable to differences in solvation shell polarization relative to the respective self-exchanges. At I = 0.10 M, ΔH? and ΔS? are less well accounted for than is ΔG?, with the deviations suggesting an exaggerated shielding of charge by the supporting electrolyte within the Debye-Hu?ckel model for ΔHw and ΔSw.
