Mossbauer oxidation

Because of the possibility of applying Mossbauer spectroscopy the solid-state chemistry of the Fe- substituted material is best understood [69, 72, 77]. Mossbauer spectroscopy confirms that the Fe in the pyroaurite type material is Fe(III). Glemser and co-workers have found that electrochemical oxidation of the material converts about 30% of the Fe(III) to Fe(IV) [69, 72], The results were... 

Electrobalances suitable for thermogravimetry are readily adapted for measurements of magnetic susceptibility [333—336] by the Faraday method, with or without variable temperature [337] and data processing facilities [338]. This approach has been particularly valuable in determinations of the changes in oxidation states which occur during the decompositions of iron, cobalt and chromium oxides and hydroxides [339] and during the formation of ferrites [340]. The method requires higher concentrations of ions than those needed in Mossbauer spectroscopy, but the apparatus, techniques and interpretation of observations are often simpler. 

The lower trialkyltin hydroxides and oxides, which are usually readily interconverted, have been characterized by IR and Mossbauer spectroscopy (212). The dimer of di-n-butyltin oxide (Bu2SnO)2 has been reported to be formed as a crystalline solid when dibutyltin dichloride is hydrolyzed with ammonium hydroxide (213). 

Recent organometallic studies have been reported. Mossbauer spectra have shown that the Fej dimer reacts at 4K with CH4 to oxidatively cleave the C—H bond to form HFe2CH3. Zirconium atoms have also been shown to oxidatively cleave the C—H and C—C bonds of alkanes to form discrete organometallic species. ... 

During oxidation of the MoFe protein the P clusters are the first to be oxidized at about -340 mV. This redox potential was first measured (40) using Mossbauer spectroscopy and exhibited a Nemst curve consistent with a two-electron oxidation process. It is possibly low enough for this redox process to be involved in enzyme turnover (see Section V). No additional EPR signal was observed from this oxidized form at this time. However, later a weak signal near g = 12 was detected and was finally confirmed, using parallel mode EPR... 

Mossbauer spectroscopy has been used to characterize the iron clusters in fuscoredoxin isolated from D. desulfuricans (133). The authors explained why the iron nuclearity was incorrectly determined, and studied the protein in three different oxidation states fully oxidized, one-electron reduced, and two-electron reduced. The error made in determining the iron cluster nuclearity was caused by the assumption that in the as-purified fuscoredoxin, cluster 2 is in a pure S = state. This assumption was proven to be false and unnecessary. In fact, the observation of four resolved, equal intensity (8% of total Fe absorption) spectral components associated with the S = i species in the as-purified protein is consistent with cluster 2 being a tetranuclear Fe cluster. The 4x8 = 32% Fe absorption for the four components indicates that only 64% of clusters 2 are in the S = state (the total Fe absorption for cluster 2 is 50% of the total Fe absorption). The remaining clusters 2 are in a different oxidation state, the spectrum of which is unresolved from that of cluster 1. 

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