Mossbauer spectra compound

The Mossbauer spectrum of the rearranged compound corresponds with that of a Sn(IV) compound, and the most probable structure appears to be that of a chlorine-bridged dimer. 

Some early studies [126] on the S-methyldithiocarbazate of 2-formylpyridine, 6, showed it to form low spin iron(III) species, [Fe(6-H)2]C104 and [Fe(6-H)2] [FeCm. The Mossbauer spectrum of the latter showed the presence of two different iron centers, and the compound was a 1 1 electrolyte in nitromethane. 

The first Ni Mossbauer spectrum of nickel in a bioinorganic compound with determinable EFG and isomer shift was reported for a nickel complex compound with planar [NiSJ core and considered as a model compound for hydrogenase. This Mossbauer spectrum from the formal Ni compound is presented in Fig. 7.16. The observed quadrupolar interaction can be understood in terms of ligand field theory. In this approach, the b g and levels (d y2 and d ) are not occupied which is expected to cause a large negative EFG contribution [32]. 

Fig. 7.16 Ni Mossbauer spectrum at 4.2 K of a nickel complex compound with planar [NiS4] core known as a model compound for hydrogenase (source Nio.gsCro.is (97% enriched) activated at Mainz Microtron) (from [32])...

The most direct information on the state of cobalt has come from Mossbauer spectroscopy, applied in the emission mode. As explained in Chapter 5, such experiments are done with catalysts that contain the radioactive isotope 57Co as the source and a moving single-line absorber. Great advantages of this method are that the Co-Mo catalyst can be investigated under in situ conditions and the spectrum of cobalt can be correlated to the activity of the catalyst. One needs to be careful, however, because the Mossbauer spectrum one obtains is strictly speaking not that of cobalt, but that of its decay product, iron. The safest way to go is therefore to compare the spectra of the Co-Mo catalysts with those of model compounds for which the state of cobalt is known. This was the approach taken... 

The appearance of only one XPS peak for a mixed valence compound is consistent with a delocalized ground state (and excited state). Bifeirocenylene (II, III) picrate, whose structure is shown in Fig. 8, probably fits in this category. The Mossbauer spectrum of the complex indicates only one kind of iron atom, and the Fe 2p3,2 spectrum consists of only one peak with a weak shoulder at higher binding energy 29). It should be recognized, however, that even in the case of a localized system in which two XPS peaks are expected, if the chemical shift between the two peaks is less than the resolution of the spectrometer, only one peak will be observed. 

JJor chemists interested in modem theories of chemical bonding, the most useful data obtainable by the Mossbauer technique are the magnitude and sign of the electric quadrupole field gradient tensor and the magnitude of the shift, 8, (which we prefer to call the chemical isomeric. Cl, shift), of the center of the Mossbauer spectrum relative to some standard absorber. Although a considerable amount of chemical and structural information is potentially available from quadrupole data on iron compounds, relatively little use has been made of such data in the literature, and we will not discuss this parameter here. We will instead restrict ourselves to two main points review of the explanations put forth to explain Cl shift data in iron compounds, and a survey of some of the correlations and generalizations which have been found. 

Dr. Herber One of the organic compounds we synthesized some years ago was a toluene dithiol complex that apparently forms a polymer, is quite stable, and produces a suitable Mossbauer spectrum at room temperature. 

Reaction of iron(II) chloride with the carbothioamide derivative of bipy, beta (200), gave three compounds, [Fe(bcta)2]Cl2 H20, [Fe(bcta)2][FeCl4], and [Fe(bcta)2]2[Cl3Fe0FeCl3]Cl2 3H20. This last compound contains low-spin Fe and high-spin Fe its Mossbauer spectrum exhibits an unusual temperature dependence." ... 

The very low Neel temperature (77 K) of lepidocrocite ensures that this compound is paramagnetic at RT. The Mossbauer spectrum at RT consists of a doublet with a AEq of 0.53 mm s . Magnetically ordered lepidocrocite shows a sextet with a Bhf of 45-46 T at 4K that is lower than that of any other Fe oxide (Johnson, 1969 Murad Schwertmann, 1984). 

Augite, Mossbauer spectrum of, 6 474 Au(PRj) fragment, addition to homonuclear gold cluster compounds, 39 329-332 Auranofin, 36 21 cytotoxicity, 36 22, 34 Auro-bis(thiosulfate), 36 18-19 Aurosomes, gold in, 36 21-22 Aurothioglucose, 36 18-19 Aurothiomalate, 36 18-21... 

FIGURE 2.1 Energy levels, isomer shift, and quadrupole splitting for 57Fe. The Mossbauer spectrum shown was recorded at T— 4.2 K with a sodium nitroprusside absorber, a diamagnetic (.S 0) compound often used for velocity calibrations. The isomer shift, indicated by the vertical dashed line, has the value 5 — —0.18 mm/s relative to Fe metal. 1 mm/s Doppler shift... 

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