Roger Parsons—Olin Palladium Award Medalist

The Olin Palladium Medal of this Society has such a distinguished set of former awardees that I suspect the person who has been asked to introduce each of the medal winners has probably felt as superfluous as I do today. Roger Parsons has played so prominent a role in the development of fundamental electrochemistry in the last thirty years that his name and his ideas constantly pop up in discussions among electrochemists in Moscow and Buenos Aires, Delhi and Paris, College Station and Pasadena

Electrochemistry and Adsorption of Bis 2,2′‐Bipyridinecobalt(I) and Bis 6,6′‐Dimethyl‐2,2′‐Bipyridinecobalt(I) in Acetonitrile

Cyclic voltammetry, coulometry, and chronocoulometry were used to examine the reduction of bis‐2,2′‐bipyridinecobalt(II), Co(bipy)^(2+)_2 , and bis‐6,6′‐dimethyl‐2,2′‐bipyridinecobalt(II), Co(dmbp)^(2+)_2 in acetonitrile solution. Both of the cobalt(I) reduction products, Co(bipy)^(+)_2 and Co(dmbp)^(+)_2 , adsorb on mercury but not on graphite or platinum electrodes. Formula decomposes at a modest rate while Formula is much more stable. Neither reduced complex proved effective as a catalyst for the electroreduction of nitrous oxide or alkyl halides

Factors Affecting the Electrochemical Responses of Metal Complexes at Pyrolytic Graphite Electrodes Coated with Films of Poly(4-Vinylpyridine)

Electrochemical responses from the reduction of RuIII (edta) coordinatedto films of high molecular weight poly(4-vinylpyridine) on pyrolytic graphiteelectrodes were studied as functions of film thickness, temperature, supportingelectrolyte composition, and solvent. Responses at filmed electrodes from metalcomplexes that do not coordinate to the films were also examined. With filmsthicker than ca. 1000Å, the current responses are limited by the rates of molecularmotions within the films. Penetration of counterions, segmental motion ofsections of the polymer chains, and juxtapositioning of pairs of attached metalcomplexes to facilitate intercomplex electron transfer within the film or combinationsof the three are suggested as likely current limiting processes

High Sensitivity of Electron Transfer Rates within Nafion Coatings Saturated with Os(bpy)^(2+)_3 to the Extent of Hydration of the Coating

The sensitivity of the electrochemical responses obtained from electroactive counterions incorporated in Nafion coatings to the extent of hydration of the coatings^(27-38) is shown to be enhanced significantly when the electroactive ion is the only counterion present in the coating. Nafion coatings fully saturated with Os(bpy)^(2+)_3 exhibit unusually narrow and sharply peaked anodic currents in first-scan oxidative voltammograms. This voltammetric feature is accompanied by the expulsion of one-third of the Os complex from the coating. The counterion actually ejected is primarily Os(bpy)^(3+)_3. As the Os(bpy)^(3+)_3 counterions are ejected, H_2O molecules enter the coatings. The quantity of H_2O molecules incorporated is so large that the mass of the coating (monitored with a quartz crystal microbalance) increases despite the ejection of the heavy Os(bpy)^(3+)_3 cations. After several voltammetric cycles, normally shaped voltammograms are obtained that are relatively insensitive to the initial state of hydration of the coatings. The contrasting behaviors of hydrated and unhydrated coatings are compared, and possible explanations are offered for the differences observed

Catalysis of the Electroreduction of Allyl Chloride by Cobalt 2,2'-Bipyridine Complexes

The electrochemical reduction of allyl chloride is strongly catalyzed in the presence of cobalt complexes of 2,2′‐bipyridine. A prominent reaction product of the catalyzed reduction is 1,5‐hexadiene. Voltammetry, coulometry, and gas chromatographic data are presented and analyzed and a mechanistic scheme proposed to account for the catalytic action of the cobalt‐2,2′‐bipyridine complexes

Electrostatic Binding of Metal Complexes to Electrode Surfaces Coated with Highly Charged Polymeric Films

Previous reports in which metal complexes have been attached to electrode surfaces coated with polymeric molecules have depended upon the formation of covalent or coordination bonds in the attachment procedure (1-4). Such schemes can be quite successful but depending, as they do, on rather specific surface chemistry, they are not applicable to as wide a variety of metal complexes as might be desirable. We have observed that coating graphite electrodes with polymers bearing charged ionic groups produces surfaces which strongly bind multiply-charged metal complexes bearing charges opposite to that on the attached ionic polymer. By exploiting this observation it is entirely possible that virtually any desired metal ion can be attached in large quantities to electrode surfaces by coordinating the metal ion with ligands that produce a multiply-charged complex ion

Shifts in Redox Formal Potentials Accompanying the Incorporation of Cationic Complexes in Perfluoro Polycarboxylate and Polysulfonate Coatings on Graphite Electrodes

The formal potentials of several redox couples incorporated in coatings of a perfluoropolycarboxylate on graphite electrodes were measured and compared with the formal potentials of the same couples in homogeneous solution. The differences observed agreed with those calculated from the Nernst equation with the independently measured incorporationcoefficients for both halves of the redox couples. The dependences of the shifts in formal potentials on the nature of theincorporating complex ion, the ionic strength, and the temperature were determined and indicated that the incorporationequilibrium is governed by electrostatic and hydrophobic interactions that act in opposite directions. The incorporation ofmost cations examined was driven by large increases in entropy which overcame the usually unfavorable enthalpy changes

Calculation of cyclic voltammetric responses for the reductive formation of catalyst-substrate adducts on electrode surfaces

Electrocatalysts based on monolayers of transition-metal complexes attached to electrode surfaces frequently follow mechanisms in which a chemical step is interposed between the first and subsequent electron-transfer steps. The cyclic voltammetric responses to be anticipated for such systems were calculated using finite difference procedures to solve the relevant differential equation. The calculated variation of the peak currents and peak potentials with the kinetic parameters governing the three steps in the mechanistic scheme are presented in graphical form. Application of the results to a specific experimental system, the catalysis of the electroreduction of O_2 by a macrocyclic complex of Co^(III) adsorbed on graphite electrodes, produced reasonable agreement between calculated and observed cyclic voltammograms

Electrochemistry of 2,2'-Bipyridine Complexes of Cobalt in the Presence of Acrylonitrile

The previously claimed (1) catalysis of the electroreduction of acrylonitrile by means of a complex of Co(I) and 2,2′‐bipyridine is shown to be erroneous. The “catalytic currents” result instead from the two‐electron reduction of a mixed complex of Co(I) acrylonitrile and 2,2′‐bipyridine. The equilibrium and forward rate constants for the formation of the mixed complex have been estimated and its spectrum is given. The behavior of a number of other vinyl monomers, which mimic acrylonitrile, is described