The Fe3+/2+ redox couple, in the form of Fe (II) and Fe (III) trifluoromethane sulphonate, has been investigated in several non-aqueous solvents; propylene carbonate (PC), acetonitrile (ACN), tetrahydrofuran (THF), dimethyl sulphoxide (DMSO) and dimethyl formamide (DMF), as well as in tetraethyleneglycol dimethylether, a low molecular weight liquid polyether, and poly(ethylene oxide), a high molecular weight solid polyether. It has been shown that the Fe3+/2+ couple exhibits a simple one electron transfer reaction in all cases. The influence of the solvent on the electrode kinetics of the Fe3+/2+ redox couple has been investigated with a view to identifying the factors controlling the rate of the simple electron transfer process for this redox couple. The standard apparent rate constant (ksh) in each system was determined via ac impedance spectroscopy. For studies in the solid polyether solvent a new technique has been developed involving ac impedance spectroscopy at an ultramicroelectrode. This new technique proved to be a very powerful tool in the identification of interfacial processes occurring in highly resistive media. Using the Marcus and the Levich, Dogonadze & Kuznetsov theories for activation of electron transfer, kinetic data were interpreted in terms of inner and outer sphere contributions from the solvent. For the liquid solvents a correlation between ksh and the donor number of the solvent was found, indicating inner sphere activation of electron transfer via vibration of the coordinate bond. However, for the solid solvent activation of electron transfer was found to be influenced by outer sphere solvent dynamics as solvent reorganisation in the polymer is slower than in the liquid solvents.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:750685 |
| Date | January 1996 |
| Creators | Christie, Lynn |
| Contributors | Bruce, Peter G. |
| Publisher | University of St Andrews |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10023/15528 |
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