By Mossbauer spectroscopy

Apart from XeF, which is the light-emitting species in certain Xe/F2 lasers, there is no evidence for the existence of any odd-valent fluorides. Reports of XeFg have not been confirmed. Of the other halides, XeCl2, XeBr2 and XeCl4 have been detected by Mossbauer spectroscopy as products of the -decay of their... 

Reinvestigation of iron porphyrins by Mossbauer spectroscopy using synchrotron radiation 98PAC917. 

Iron electronic configurations in proteins studies by Mossbauer spectroscopy. A. J. Bearden and W. R. Dunham, Struct. Bonding (Berlin), 1970, 8, 2-52 (196). 

With trifluoromethanesulfonic acid, all four vinyl groups are displaced at - 78°, to give a compound that was shown by Mossbauer spectroscopy to contain both Sn(II) and Sn(IV), and that was assigned the formula Sn [Sn (S03CF3)6]. Trivinyltin carboxylates have also been prepared from the reaction between tet avinyltin and mercury(I) carboxylates, which may be generated electrochemically in situ (185). 

Desulforubidin was found in strains of the Desulfomicrobium genus and has been described as the sulfite reductase of this genus. The subunit composition and molecular mass are similar to what was observed for desulfoviridin. However, in desulforubidin all sirohydrochlorins are metalated as proved by Mossbauer spectroscopy (152). The as-isolated protein contains four [4Fe-4S] clusters two of them are exchange-coupled to two paramagnetic sirohemes. 

The Fe hyperfine tensor components were determined by Mossbauer spectroscopy in the case of the rubredoxin from Clostridium... 

This study could be extended to the synthesis of iron nanoparticles. Using Fe[N(SiMe3)2]2 as precursor and a mixture of HDA and oleic acid, spherical nanoparticles are initially formed as in the case of cobalt. However, a thermal treatment at 150 °C in the presence of H2 leads to coalescence of the particles into cubic particles of 7 nm side length. Furthermore, these particles self-organize into cubic super-structures (cubes of cubes Fig. ) [79]. The nanoparticles are very air-sensitive but consist of zerovalent iron as evidenced by Mossbauer spectroscopy. The fact that the spherical particles present at the early stage of the reaction coalesce into rods in the case of cobalt and cubes in the case of iron is attributed to the crystal structure of the metal particles hep for cobalt, bcc for iron. 

Bearden, A. J., Dunham, W. R. Iron Electronic Configuration in Proteins Studies by Mossbauer Spectroscopy. Vol. 8, pp. 1-52. 

Spin-canting is conveniently studied by Mossbauer spectroscopy with large magnetic fields applied parallel to the y-ray direction. The relative areas of the six lines are given by 3 p l l p 3, where... 

The ratio of the quadrupole moments in tungsten isotopes as measured by Mossbauer spectroscopy - collected from [222-228] - is... 

We have learned from the preceding chapters that the chemical and physical state of a Mossbauer atom in any kind of solid material can be characterized by way of the hyperfine interactions which manifest themselves in the Mossbauer spectrum by the isomer shift and, where relevant, electric quadrupole and/or magnetic dipole splitting of the resonance lines. On the basis of all the parameters obtainable from a Mossbauer spectrum, it is, in most cases, possible to identify unambiguously one or more chemical species of a given Mossbauer atom occurring in the same material. This - usually called phase analysis by Mossbauer spectroscopy - is nondestructive and widely used in various kinds of physicochemical smdies, for example, the studies of... 

Coordination compounds of dianionic dithiolene (S2C2 R2) and benzene-1,2-dithiolene (bdt = (S2C6H4) and their derivatives have been studied since the 1960s by Mossbauer spectroscopy [87] and other techniques. Nevertheless, many aspects of their electronic structure remained uncertain for a long time. The five-coordinate ferric complexes with two equatorial dithiolene ligands exhibit intermediate spin and show the Mossbauer parameters = 0.25-0.38 mm s and A q = 1.6-3.2 mm s For example, [Fe° mnt)2/ y] with two mnt ligands (=S2C2(CN)2) and an... 

Scorzelli, R. B., S. Petrick, A. M. Rossi, G. Poupeau, and G. Bigazzi (2001), Obsidian archeological artefacts provenance studies in the western Mediterranean basin An approach by Mossbauer spectroscopy and electron paramagnetic resonance, C. R. Acad. Sci., Series Ila, Sciences de la Terre et des Planetes, 332(12), 769-776. 

Iron oxidized by ferritin must be at or near the outer surface of the apoferritin molecule, since iron appears to be exchanged between ferritin molecules, as shown by Mossbauer spectroscopy (Bauminger et ah, 1991a,b) and by the observation that iron oxidized by ferritin can be taken up directly by apotransferrin (Bakker and Boyer, 1986 Jin and Crichton, 1987). 

The aim of this work was to apply combined temperature-programmed reduction (TPR)/x-ray absorption fine-structure (XAFS) spectroscopy to provide clear evidence regarding the manner in which common promoters (e.g., Cu and alkali, like K) operate during the activation of iron-based Fischer-Tropsch synthesis catalysts. In addition, it was of interest to compare results obtained by EXAFS with earlier ones obtained by Mossbauer spectroscopy to shed light on the possible types of iron carbides formed. To that end, model spectra were generated based on the existing crystallography literature for four carbide compounds of... 

Although three forms of Te03 can be found in the literature, only one, the so-called p-Te03, is a real Te(VI) compound, while a- and y-Te03 contain substantial amounts of Te4+ as it has been shown by Mossbauer spectroscopy in the case of a-Te03 and by vibrational spectroscopy proving the presence of... 

The special feature of the spin crossover process in all bpym-bridged dinuclear compounds studied so far is the occurrence of a plateau in the spin transition curve. A reasonable assumption to account for this observation is that a thermal spin transition takes place successively in the two metal centres. However, it cannot be excluded that spin transition takes place simultaneously in the dinuclear units leading directly from [HS—HS] pairs to [LS-LS] pairs with decreasing temperature. Therefore, two possible conversion pathways for [HS—HS] pairs with decreasing temperature may be proposed [HS—HS]<->[HS—LS]<->[LS—LS] or [HS-HS] [LS-LS]. The differentiation of the existence of the [LS—LS], [HS—LS], and [HS—HS] spin pairs is not trivial and has recently been solved experimentally by utilisation of magnetisation versus magnetic field measurements as a macroscopic tool [9], and by Mossbauer spectroscopy in an applied magnetic field as a microscopic tool [11]. 

A further example illustrating the importance of lattice effects on the SCO behaviour of these trinuclear compounds is given by [Fe3(iptrz)f,(H20)6] (CF3S03)6 (iptrz = 4-(isopropyl)-1,2,4-triazole). A strong influence of the ST of the central Fe(II) ion on both external Fe(II) ions has been found by Mossbauer spectroscopy, as detected by the perturbation of their quadru-pole interactions [15]. The nature of this phenomenon has been proposed to... 

Schroder, C. et al. 2004. Weathering of Fe-bearing minerals under Martian conditions, investigated by Mossbauer spectroscopy. Planetary and Space Science, 52, 997-1010. 

When the Fe-MnO catalyst is analyzed after use in the Fischer-Tropsch reaction (the synthesis of hydrocarbons from CO and H2), the XRD pattern in Fig. 6.2 reveals that all metallic iron has disappeared. Instead, a number of weak reflections are visible, which are consistent with the presence of iron carbides, as confirmed by Mossbauer spectroscopy [7]. The conversion of iron to carbides under Fischer-Tropsch conditions has been studied by many investigators and has been discussed in more detail in Chapter 5 on Mossbauer spectroscopy. 

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). 

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