Electron transfer reactions in micellar systems: Separation of the true (unimolecular) electron transfer rate constant in its components

A comparative study on the electron transfer reaction (ETR) of surfactant cobalt(iii) complexes of aliphatic/aromatic ligands in micro heterogeneous media: a thermodynamic approach

The electron transfer reaction between different surfactant cobalt(iii) complex ions and Fe²⁺ ions in micelles as well as β-cyclodextrin was studied at different temperatures using a spectrophotometry method.

Thermodynamics and kinetic investigation of electron transfer reactions of surfactant cobalt(iii) complexes containing diimine ligands with iron(ii) in the presence of liposome vesicles and amphiphilic salt media

The kinetics of reductions of surfactant cobalt(iii) complexes by iron(ii) in liposome vesicles (DPPC) and amphiphilic salt ((BMIM)Br) were studied at different temperatures by UV-Vis absorption spectroscopy method under pseudo first order conditions using an excess of the reductant.

Determination of Reaction and Reorganization Free Energies of Electron Transfer Reactions under Restricted Geometry Conditions

In this paper, different methods of obtaining the two parameters controlling the rate of electron transfer processes (reaction and reorganization free energies, Λ and Δ G0’, respectively) under restricted geometry conditions are considered. The main difficulty of accomplishing this comes from lack of knowledge of the properties in the interfacial region, where the reaction occurs. A general method has been presented and illustrated with the study of intermolecular processes in micelles. This method is optimized when the free energies for (at least) the three reactions required are quite different. For excited state electron transfer, the general approach is based on the appearance of the so-called Marcus inverted region: at the starting point of this region the value of Δ G0’ gives the value of Λ directly. These reaction free energies also present some uncertainties because in their calculation it is necessary to know the value of the local dielectric constant. Finally, it should be mentioned that some authors have suggested that the treatments for electron transfer reactions could not be applicable under restricted conditions. However, experiments do seem to show the applicability of the Marcus-Hush treatment under these conditions.

Reaction and reorganization free energies of electron-transfer reactions under restricted geometry conditions

Electron-transfer reactions between iron and cobalt complexes were studied in beta-cyclodextrin (betaCD), 2-hydroxypropyl-beta-cyclodextrin (HbetaCD), and 18-crown-6 ether (18C6) solutions. The results were rationalized taking as the basis the Marcus-Hush formalism. We employed two different approaches, depending on the kind of receptor and solvent, to obtain the reorganization and reaction free energies that determine the reaction rate constant. The opposite trends in reactivity observed in betaCD and HbetaCD solutions and the behavior in solutions of 18C6 are explained.

Micellar catalysis on the electron transfer reactions of iron(iii)-polypyridyl complexes with organic sulfides—importance of hydrophobic interactions

The oxidation of organic sulfides with iron(III)-polypyridyl complexes [Fe(NN)3]3+ proceeds through an electron transfer mechanism and an increase in the methanol content in the methanol-water mixture favors the reaction. The reaction is catalyzed by both the anionic surfactant, sodium dodecyl sulfate (SDS) and the cationic surfactant, cetyltrimethylammonium bromide (CTAB). The micellar catalysis in the presence of SDS is accounted for in terms of strong binding of the cationic oxidant with the anionic surfactant and the development of positive charge on sulfur center of substrate in the transition state. The micellar catalysis observed on the reaction involving a trication, [Fe(NN)3]3+, in the presence of CTAB indicates the importance of hydrophobic interaction between the micelle and hydrophobic ligand of [Fe(NN)3]3+. The micellar catalysis is explained in terms of a pseudophase ion exchange model.

Method for the Evaluation of the Reorganization Energy of Electron Transfer Reactions Produced under Restricted Geometry Conditions

The kinetics of the electron transfer reactions between S(2)O(8)(2-) and the complexes (Ru(NH(3))(5)L)(2+) (L = pyridine, pyrazine, and 4-cyanopyridine) have been studied in micellar (SDS) solutions. A method for the evaluation of the reorganization energy of these reactions, based on the comparison of their rate constants, is proposed. From the results obtained, we concluded that the observed rate constants go through a minimum for the surfactant concentration in which the reorganization energy goes through a maximum. The method can be applied to any kind of restricted geometry conditions.