Mossbauer spectroscopy neutralization

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

The oxidation state of the central iron ions in the neutral species [FeL], as well as their monocation and dicationic oxidation products, [Fe(L )]+ and [Fe(L )]2+, are amenable to direct measurement by Mossbauer spectroscopy where the isomer shift gives direct information for the dn electron configuration, provided that the coordination number and the nature of the donor atoms are invariant. Frozen acetonitrile solutions of the above 57Fe enriched species have been investigated by this technique (147). 

Khoe Robins, 1989 Bottero et ak, 1991 1994, Tchoubar et ak, 1991 Rose et ak 1997 Doelsch et ak 2000). Johnston and Lewis (1986) separated the species in partly neutralized 0.1 M Fe(N03)3 solutions into different molecular weight fractions by ul-trafiltration (Amicon DiafQters) and examined each fraction with Mossbauer spectroscopy. In all fractions Fe was octahedrally coordinated. Monomers and dimers predominated in the <500 fraction when no base was added. As OH/Fe increased to 0.5, the proportion of polymer species (MW >500) increased from 12 to 44% and at OH/... 

The first isolable, albeit binuclear, butatrienylidene complexes, the cationic diiron complexes 8, were likewise prepared by addition of an electrophile E+ to neutral butadiynyl complexes. Instead of mononuclear butadiynyl complexes, binuclear C4-bridged butadiyndiyl complexes 7 were used as the starting complexes by Lapinte et al. (Scheme 3.4) [18]. Complexes 8 were characterized by multinuclear NMR, IR, UV-vis, and Mossbauer spectroscopies, mass spectrometry and cyclic voltammetry. 

Iron Core Only a small fraction of the iron atoms in ferritin bind directly to the protein. The core contains the bulk of the iron in a polynuclear aggregate with properties similar to ferrihydrite, a mineral found in nature and formed experimentally by heating neutral aqueous solutions of Fe(III)(N03)3. X-ray diffraction data from ferritin cores are best fit by a model with hexagonal close-packed layers of oxygen that are interrupted by irregularly incomplete layers of octahedrally coordinated Fe(III) atoms. The octahedral coordination is confirmed by Mossbauer spectroscopy and by EXAFS, which also shows that the average Fe(III) atom is surrounded by six oxygen atoms at a distance of 1.95 A and six iron atoms at distances of 3.0 to 3.3 A. 

The heteronuclear mixed-valence complexes 16b,c were obtained from H2L 15, triethylamine, and iron(III) chloride in the presence of an excess of cobalt(II) chloride or copper(II) chloride. In neutral 16b,c iron is present only in the oxidation state 3 , as unambiguously confirmed by Mossbauer spectroscopy, which reveals only one quadruple doublet. Cyclic voltammetric investigation of the redox-active metal centers of neutral 16b shows a reversible three-potential one-electron transfer process. The half-wave potentials of -660 and -1310 mV correspond to the redox processes [(Fe )2Co"OLf ] [Fe Fe Co OLf ]" [(Fe")2Co"OLf ] , whereas... 

TPP)Fe]2C in CH2CI2 can be oxidized by four electrons in four successive one-electron-transfer steps, but the number of oxidations varies with the nature of the nonaqueous solvent [246]. Neutral [(TPP)Fe]2C was shown to contain two Fe(IV) units by Mossbauer spectroscopy [247], and the four redox processes of this porphyrin most likely correspond to a stepwise oxidation of the jr-ring system to form initially two individual n-cation radicals (one on each macrocycle) and then two porphyrin dications at more positive potentials [246]. 

Starting from iron acetate or iron nitrate salts and following the neutral and oxidative pathways, a separated analysis of iron (2+, 2.5+, 3+)-calcium oxide and iron (2+, 2.5+, 3+)-magnesium oxide will be useful also to clarify the nature of the iron-dolomite interaction. The Fe/substrate catalysts have been characterized by X-Ray diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Oxidation (TTO), and Mdssbauer analysis. XRD and TPR experimental conditions, as well as the microreator used in catalytic tests, have been described previously [Di Felice et al., 2009], whereas Mossbauer spectroscopy and TPO are briefly illustrate here. 

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