Isomer shifts and quadrupole splittings

Summary of EPR -Values, Fg-Hyperfine Coupling Constants, Isomer Shifts, and Quadrupole Splittings for Some Representative [Fg3S4] Clusters... 

The spin state of the compounds XFe(R2dtc)2 is 3/2 (64). Mossbauer spectra of ClFe(Et2 tc)2 in solution are almost identical with the spectrum of the six-coordinated Fe(Et2magnetic susceptibility and in the isomer shift and quadrupole splitting parameters suggests a geometrical correspondency in solution, which can be attained by the binding of a solvent molecule to the sixth coordination site of the ClFe(Et2[Pg.98]

Various Ru-oxides, YBa2Cu307, c (I), Ba Ru2/3Gdi/303 (II) as well as Ru-doped a-Fe203 (III), to probe the local chemical structure around the Ru atoms. Compound (I) has interesting properties with x < 0.2 it is a superconductor and with x 1 a semiconductor. Ru oxidation state and coordination are discussed on the basis of measured isomer shifts and quadrupole splittings Ru(IV) ions exclusively occupy Cu-1 sites which form one-dimensional chains... 

Wagner et al. [258] reported a systematic investigation of the isomer shift and quadrupole splitting in various osmium compounds. Of special interest is the comparison with similar or isoelectronic compounds of iridium and ruthenium. 

The range of isomer shifts and quadrupole splittings is larger than that for tin and iron. 

Table 8.6 Isomer shift and quadrupole splitting of iron carbonyls and metal-organic compounds...

Apart from the determination of the structures of stannylenes by diffraction methods (X-ray or electron diffraction) many other physico-chemical techniques can be exployed to characterize these compounds more completely. Besides the classical methods such as IR-, Raman-, PE-, UV- and NMR-spectroscopy, MoBbauer-119 m-tin spectroscopy is widely used for the determination of the oxidation states of tin atoms and of their coordination 1n8-12°-123>. jt is not in the scope of this report to study the dependence of MoBbauer constants such as isomer shift and quadrupole splitting on structural parameters. Instead, we want to concentrate on one question Which information can we deduce from the structure of stannylenes to evaluate their reactivity ... 

The source for the 14.41-keV y radiation used in Mossbauer experiments is indicated by the boldface arrow in Figure 3.26.3 Origin of the isomer shift and quadrupole splitting phenomena are indicated at the right-hand side of the diagram. 

Figure 3.26 Cobalt-57 source of 14.41-keV y radiation used in Mossbauer experiments. Isomer shift and quadrupole splitting characteristics are shown at right. (Adapted from Figure 2.26 of reference 3 and Figure 1 of reference 24.)...

The temperature dependence of the isomer shift and quadrupole splitting for the high-spin and low-spin iron(II) states in [Fe(HC(3,5-(CH3)2pz)3)2](BF4)2 and details of the fits and their temperature dependence may be found elsewhere [46]. The extent of the spin-state crossover is shown in Fig. 18, a figure which clearly indicates that the spin-state crossover in [Fe(HC(3,5-(CH3)2pz)3)2](BF4)2 stops at 50 percent. In contrast it should be noted that, in the structurally very similar [Fe(HC(3,5-(CH3)2pz)3)2]l2 complex, [49] the spin-state crossover is 100 percent complete at 4.2 K. 

Figure 5.7 gives the relation between isomer shift and quadrupole splitting for iron in various environments. In oxidic components of iron catalysts, one usually only encounters the high-spin configurations of Fe2+ and Fe,+ ions. 

Mossbauer isomer shift and quadrupole splitting are commonly used to obtain information about the bonding environment around source nuclides. The isomer shift arises from the electric monopole interaction of the nucleus with the electrons and depends on the... 

The Mossbauer effect, although not a substitute for other analytical methods such as x-ray diffraction, can be used to obtain several kinds of structural information about solids. In favorable cases, it is possible to obtain rather detailed information about the electronic configuration of atoms and the local symmetry of their sites by measuring the isomer shift and quadrupole splitting. If more than one valence state of a given atom is present, a semiquantitative determination of the amount of each kind is possible. In solid solutions, the amount of local or long range order can be estimated, and in certain defect structures the relation between the active atoms and the defects can be studied. 

Relation between isomer shift and quadrupole splitting for stannous compounds (13)... 

Relationship between Isomer Shift and Quadrupole Splitting in Some Iodine Compounds... 

Table I. Isomer Shifts and Quadrupole Splittings at Liquid Nitrogen Temperature...

A correlation between the isomer shift and quadrupole splitting is adumbrated. However, more data would be needed to confirm this. Such a correlation might be consistent with the molecular orbital approach and the linear relationships in Equations 3 and 5. The decreased quadru-... 

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