Reversible oxidation and rereduction of magnesium phthalocyanine (MgPc) thin films (1 000-2000 8, thick) on gold electrodes have been observed in the potential range from 0.0 to 0.9 V vs. SCE in various electrolytes, including aqueous NaCI, NaNO,, NaCIO.,, and potassium hydrogen phthalate (KHP). In situ Raman spectra recorded during oxidation and rereduction show spectral changes in the 400-1800-cm-' range that can be related to the vibrational modes of ring structures in MgPc, hence the oxidation seems to occur in the ligand. The spectroscopic results unambiguously demonstrate the movement of anions into and out of the electrode during oxidation and rereduction processes. Both cyclic voltammetry and chronocoulornetry showed that smaller anions allow full oxidation at rapid rates, whereas larger ones inhibit the oxidation, at least with respect to rate. Auger electron spectrometry showed that anions appear to be homogeneously distributed in partially oxidized films.

Cyclic voltammetry data have been obtained for the bis-, bisesquis-, and tris(2,2'-bipyridine) (bpy) complexes of iridium(II1) in acetonitrile. A reaction mechanism is proposed based on analysis of electrochemical and luminescence data. For the bisesquis and tris complexes the mechanism involves successive one electron transfers producing stable species on an electrochemical time scale. For [Ir(bpy),Clz]+ the electron transfer sequence is interrupted at several steps by the elimination of a chloride. These elimination reactions are time dependent and can be resolved by the variation of the scan rate. The classification of the redox orbitals as localized or delocalized is also discussed.

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A new model system was developed for the study of autoxidation of thin films of neat lipid and the effect of relative humidity on the oxidation reaction. In the model system, the surface-to-volume ratio of lipid was large and measureable, and the relative humidity (RH) and oxygen partial pressure were controlled. Methyl linoleate, oxidized at six different RH as a thin film in an atmosphere of pure oxygen, exhibited a maximum rate of oxidation at 32% RH and minimum rates at 0% and 100% RH. The rates of oxygen uptake, determined manometrically, were linear and reproducible at all six RH. The maximum rate at 32% RH was attributed to solvation and stabilization of the propagation transition state by water. Increasing the RH beyond 32% resulted in solvation of the peroxy radical, sterically hindering the radical from entering the propagation transition state.

The electrochemical oxidation of 1,8-bis(4-methylpheny1thio)-9-(2, 6-dimethoxyphenyl) .These results ,provide strong evidence for the postulated structure of dication 2 which incorporates