Mdssbauer quadrupole splitting

The presence of the oxo bridge in oxyHr and metHrX is reflected in then-magnetic susceptibility, NMR, and MOssbauer properties. The coirq)lexes exhibit strong andferromagnetic coupling, small NMR isotropic shifts, and large Mdssbauer quadrupole splittings. J values obtained for metHr and oxyHr from fits to variable temperature susceptibiliy data are -134 and -77 cm-i, respectively (34). The J for metHr compares favorably with those observed for the synthetic... 

The QS in the Fe Mdssbauer spectra is determined by the geometry of the iron(II) coordination polyhedron and has been utilized to gain information on the structure of the complexes from the spectral parameter vs structure correlation. Conversely, the data available on the structure of clathrochelates employed for working out a modern version of the partial quadrupole splitting (PQS) concept permits one to obtain absolute PQS values and to analyse the results for macrobicyclic complexes [264, 265]. 

Table 10. Comparison of Quadrupole Splittings (AEQ) and Isomer Shifts (S) for some Xe(II) and Xe(IV) Compounds, derived from 129Xe Mdssbauer Spectra (Ref.40 )...

Sn Mdssbauer data have been reported for 3-Sn-l,2-B9C2H, 8 = 4.67 0.04mm s, AE0 = 3.83 0.004 mm s. The isomer shift is consistent with a formal Sn" oxidation state, while the large quadrupole splitting arises from the marked asymmetry of the molecular structure.76... 

Fig. 10. Mdssbauer spectra of reduced (left panels) and oxidized (right panels) PS-I core complex at 80 K (top panels) and 4.2 K (bottom panels), The lower spectrum in each of the left panels was corrected for the unreduced component. The table at top right lists the experimentally determined isomer-shift (IS) and quadrupole-splitting (QS) parameters for oxidized and reduced core complexes at 77 K lower table lists isomer-shift values reported in the literature for other [4Fe 4S] and [2Fe 2S] clusters. Data source Petrouleas, Brand, Parrett and Golbeck (1989) A Mossbauer analysis of the low-potential iron-sulfur center in photosystem I Spectroscopic evidence that Fx is a [4Fe-4S] cluster. Biochemistry 28 8982.

Table 12. Mdssbauer spectra of polymeric iron phthalocyanine (6 experimental isomer shift, A quadrupole splittings, A relative areas of absorption lines, f line widths details s, 193)...

Two crystalline modifications of tin(II) fluoride are known [53]. The orthorhombic form of SnF2 shows significantly different Mdssbauer parameters from the better-known monoclinic form. In particular the smaller chemical isomer shift in the former is indicative of increased covalent character, while the larger quadrupole splitting suggests a more distorted environment about... 

The Mdssbauer spectra, particularly useful in the case of iron compounds, can be exploited for the construction of the xHS versus T curve as well. They exhibit a characteristic quadrupole doublet for the HS state which is differently positioned (isomer shift) and possesses a different width (higher quadrupole splitting) when compared to the LS state (Fig. 9.3). Thus the area fraction of quadrupole splitting for the HS complex gives rise to... 

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