Electrochemistry of chemisorbed molecules. II. Influence of charged chemisorbed molecules on the electrode reactions of platinum complexes

Abstract

The influence of chemisorbed olefins having ionic substituents on the electrode rates of Pt(II) and Pt(IV) complexes at Pt electrodes has been studied. Chemisorption alters the potential at the reaction plane, n<t>2, with the result that ionic complexes tend to react more rapidly at surfaces coated with ionic olefins of opposite charge than at clean surfaces. A comparison of cationic coatings, such as allylammonium ion with anionic ones (such as allylacetic acid anion) adsorbed at potentials positive of the zero-charge condition, demonstrates that the extent to which r<£2 is altered depends upon the position of the charged substituent in relation to the remainder of the double layer and not merely upon the magnitude of its interfacial excess. The detailed electrostatic effects can be predicted in terms of a Boltzmann distribution, taking into account the chain length, structure, functional group charge, electrodic charge, and position of the reactant during electron transfer. The precise extent to which the reactions are sterically hindered by the chemisorbed surfactant has been determined from the variation of electrode rate with surfactant coverage. The results indicate that two adjacent electrode sites are required to form the rate-limiting intermediate in halide-bridged reduction of Pt(IV) complexes.

Electrochemistry and blocking properties of thin films of platinum phenylethynyl complexes

“…Platinum surfaces have been modified with alkene-containing molecules, which bind to the Pt through their p bond, much as they do with Pt hydrogenation catalysts [8,9]. However, no work on electrode films consisting of alkynes has been reported.…”

Electrode Materials (Bulk Materials and Modification)

“…22 The range of analytes that can be determined with electrochemical reaction on bulk electrodes is large and comprised both metal ions and organic compounds. The possibility to preconcentrate the species to be detected by simple adsorption or electrochemical concentration before stripping analysis permits to reach very low detection limits, i.e., down to 10 À10 M. Moreover, several species (e.g., metal ions) can be detected Adsorption of alkenes on platinum electrodes 6,7 1978 Deposition of polymers on electrodes 8,9 1981 Chemically modified carbon paste electrodes 10 …”

“…6,7 They were the first to suggest the possibility of modifying the electrode surface to achieve a desired functionality. In 1976, Elliott and Murray had foreseen the potential of chemically modified electrodes as they described "this line of research as leading to a wide array of chemically modified electrode surfaces with unusual analytical, chemical, catalytic, and optical properties".…”

Modified Electrodes

“…The result shows that the sensitivity of the cell to photon energies lower than the bandgap of the semiconductor is possible. It is known that sensitization can only be accomplished by excited adsorbed dye molecules.llS,ll 6 It has been observed that much higher photocurrents are obtained when rhodamine B (RhB) is bonded to Sn02 through a direct ester linkage than with the n-propylamide linkage. This difference was initially interpreted in terms of the insulating character of the propyl chain in the amide system.…”