Mossbauer spectroscopy table

Spectroscopy (spectrometry) — MoRbauer (Mossbauer) spectroscopy — Table... 

Figure 10.9 shows the temperature dependence of the effective magnetic moments of [Fe(OETPP)(L)2] determined by SQUID for the microcrystalline samples [45]. In the solid, spin crossover occurs not only in the Py but also in the 4-CNPy complex, which is further supported by the Mossbauer spectroscopy. Table 10.9 shows the Mossbauer parameters of [Fe(OETPP)(L)2]" and [Fe(OMTPP)(L)2] determined at ambient temperature and at 78-80 K [45,70]. Being consistent with the magnetic data, [Fe(OETPP)(4-CNPy)2]" shows two sets of doublets at 80 K assigned... 

The relation of the structure of organotin compounds and their activity is not found from the data of X-ray diffraction and Mossbauer spectroscopy (Table 10.11) [105,106]. The organotin compounds are considered to act in an entirely different way from cisplatin. 

Application of Mossbauer Spectroscopy Table 3.2 Summary of hypeifine parameters for goethite... 

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 various, solid-state stereochemistries just described may often be distinguished fairly readily by " Sn Mossbauer spectroscopy 5-9, 452), particularly from the value of the quadrupole splitting parameter, AEq (see Table II). 

Typical Mossbauer spectra for the fresh, reduced, carblded and used Fe/ZSM-5 system are shown in a composite Fig. 5. Similar spectra were obtained for the Fe-Co/ZSM-5 system. The product distribution for the F-T reaction, using the Fe and Fe-Co systems, are shown in Table 1. The gasoline range hydrocarbon yield increased from 75 to 94%, when the Fe-Co clusters were used in place of Fe only. In a typical CEMS (Conversion Electron Mossbauer Spectroscopy) of the Fe-Co system, no spectrum for 57pg vas observed even after one week from this. It was concluded that in the Fe-Co clusters Co was predominantly in the "mantle" and Fe species were In their "core," in the parlance of metallurgy/geophysics. This model Is sometimes referred to as the cherry model. 

Table I. Samples Used for MOssbauer Spectroscopy and Magnetic Susceptibility Studies...

Table 3.2 Properties of detectors commonly used in Mossbauer spectroscopy...

For a comparison of experimental Mossbauer isomer shifts, the values have to be referenced to a common standard. According to (4.23), the results of a measurement depend on the type of source material, for example, Co diffused into rhodium, palladium, platinum, or other metals. For Fe Mossbauer spectroscopy, the spectrometer is usually calibrated by using the known absorption spectrum of metallic iron (a-phase). Therefore, Fe isomer shifts are commonly reported relative to the centroid of the magnetically split spectrum of a-iron (Sect. 3.1.3). Conversion factors for sodium nitroprusside dihydrate, Na2[Fe(CN)5N0]-2H20, or sodium ferrocyanide, Na4[Fe(CN)]6, which have also been used as reference materials, are found in Table 3.1. Reference materials for other isotopes are given in Table 1.3 of [18] in Chap. 1. 

In Table 7.1 at the end of the book), nuclear data are collected for those Mdssbauer transitions of transition metal nuclides that are used in Mossbauer spectroscopy. The symbols used in this table have the following meaning ... 

Chemical information from hafnium Mossbauer spectroscopy can primarily be deduced from the quadrupole-splitting parameter. In Table 7.4, we have listed the quadrupole coupling constants eQV for some hafnium compounds. Schafer et al. 

There are two iridium isotopes, ir and Ir, suitable for Mossbauer spectroscopy. Each of them possesses two nuclear transitions with which nuclear resonance absorption has been observed. Figure 7.58 (from [266]) shows the (simplified) nuclear decay schemes for both iridium Mossbauer isotopes the Mossbauer transitions are marked therein with bold arrows. The relevant nuclear data known to date for the four Mossbauer transitions are collected in Table 7.1 at the end of the book. 

Bis(stannyl) dicarboxylates 10 and 11 showed usually tetracoordinated Sn atoms by IR and MOssbauer spectroscopy. See also Tables 5 and 8124. 

TABLE 7. Structural determination of organometallic compounds containing tin(II) atoms by NMR and Mossbauer spectroscopy methods... 

Polymeric trigonal bypiramidal Sn structure 221 with trans O—Sn—O binding. Also variable-temperature 119Sn Mossbauer spectroscopy (see compound 50 in Table 5). These compounds are important pesticides. 

The results of Mossbauer spectroscopy investigations of Fe(C0)5 decomposition on Ti02 samples pretreated in three different fashions are given in Table I. These three samples were pretreated in a manner intended to produce different populations of Ti + ions and hydroxyl groups on the surface of the support. This is explained in the discussion section. 

In Table II, it can be seen that decomposition at low temperatures left a CO/Fe ratio on the surface of between 0.8 and 1.3. A reasonable explanation for the high CO to iron ratios on the surfaces, given the fact that Mossbauer spectroscopy studies show that a large fraction of the iron is oxidized, is that iron subcarbonyl species are stable on the surface at 383 K. This is true since CO does not adsorb strongly on iron oxides (35). 

Table I shows the various Mossbauer nuclides—i.e., the nuclides where the Mossbauer eflFect has actually been seen. Not all of these are as easy to exploit as the Fe and 9Sn cases referred to above. However, with improved techniques a number of these should prove accessible to the chemist. Representative elements of almost all parts of the periodic table are tractable by these techniques. It seems clear, however, that the methods of Mossbauer spectroscopy are no longer technique-oriented but that this field is becoming a problem-oriented discipline. In other words, the Mossbauer effect is now used successfully in many cases not only to demonstrate the effect or to corroborate physical evidence obtained by other means—NMR, or infrared, or kinetic studies— but also to solve new chemical problems.

For iron and tin the magnitude of 8 has been found to be related to the oxidation state of the metal (15, 28) (Table I). In iron complexes, the spin of the 3d electrons of the iron atoms can be paired (low spin) or unpaired (high spin). In low spin ferrous and ferric complexes, 8 and AEq values are similar, but the value of AEq differs greatly for the high spin complexes (Figure 1). Mossbauer spectroscopy has been used to... 

As indicated in the previous discussion, Mossbauer spectroscopy provides information that when coupled with results using other structural techniques assists in determining the structure of the complex under analysis. The relationships between the various techniques are summarized in Table II. The Mossbauer chemical shift provides information about the 4 electron contribution to the bond between the metal and the ligands in a complex. Similar estimates can be obtained from the results of measurements on the fine structure in the x-ray absorption edge and nuclear magnetic resonance data. The number of unpaired electrons can be evaluated from magnetic susceptibility data, electron spin resonance, and the temperature coeflScient of the Mossbauer quadrupole splitting (Pr). 

Dr. Erickson For those interested in coordination chemistry, certain other transition metal atoms are suitable for Mossbauer spectroscopy. One in particular is ruthenium which is just below iron in the Periodic Table. It is a difficult isotope to work with since it requires helium temperatures almost exclusively. I don t know whether it is possible to work at nitrogen temperatures or not, but Kistner at Brookhaven has examined various ruthenium compounds from the 2-j- to the 8+ oxidation states with interesting results. These are not published yet, but at least his work offers the possibility of going down one element below the other in the Periodic Table to study chemical effects. Osmium, which is below ruthenium, can also be Mossbauered. Some sort of systematic study like this involving elements in the various transition series would be extremely interesting. 

One large class of non-heme iron-containing biomolecules involves proteins and enzymes containing iron-sulfur clusters. Iron-sulfur clusters are described in Sections 1.7 (Bioorganometallic Chemistry) and 1.8 (Electron Transfer) as well as in Section 3.6 (Mossbauer Spectroscopy). See especially Table 3.2 and the descriptive examples discussed in Section 3.6.4. Iron-sulfur proteins include rubredoxins, ferrodoxins, and the enzymes aconitase and nitrogenase. The nitrogenase enzyme was the subject of Chapter 6 in the hrst edition of this text—see especially Section 6.3 for a discussion of iron-sulfur clusters. In this... 

The variety of symmetries in the garnet structure (coordinations 4, 6, and 8) allows considerable compositional range. Table 5.16 lists the elements commonly present in positions X, X and Z. The diadochy of Al, Ti" ", and Fe in the tetrahedral site has been confirmed by Mossbauer spectroscopy on natural Fe-Ti-bearing garnets (Schwartz and Burns, 1978), and the presence of phosphorus in these sites, observed in upper mantle garnet, is attributable, according to Bishop et al. (1976), to coupled substitutions of the type... 

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