57Fe Mossbauer

McMahon, M. T., deDios, A. D, Godbout, N., Salzmann, R., Laws, D. D., Le, H., Havlin, R. H., Oldfield, E., 1998, An Experimental and Quantum Chemical Investigation of CO Binding to Heme Proteins and Model Systems A Unified Model Based on 13C, 170 and 57Fe Nuclear Magnetic Resonance and 57Fe Mossbauer and Infrared Spectroscopies , J. Am. Chem. Soc., 120, 4784. 

Figure 2 57Fe Mossbauer spectrum for a poly(w-carborane-siloxane).

Fe Mossbauer study of iron distribution in zeolite A during zeolite crystallization process... 

Keywords Fe-exchanged zeolite A, 57Fe Mossbauer spectroscopy, hydrothermal crystallization... 

The samples were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, 57Fe Mossbauer spectroscopy [2] and Rutherford backscattering spectrometry (RBS). 

Figure 2. Relative amounts of various iron species deduced from 57Fe Mossbauer spectra of the Fe-exchanged samples shown in relation to the progress of the hydrothermal crystallization process at 80°C (A), 57Fe Mossbauer spectra of the Fe-exchanged samples after 0 (a), 120 (b), 180 (c) and 240 min (d) of the hydrothermal crystallization process at 80°C (B) and RBS spectra collected on five different particles of the sample crystallized for 240 min (C). The position of surface Fe in Fig. 2C is marked by the vertical arrow. Depth scale (depth into each particle) is increasing toward left (marked with the horizontal arrow). Fit to experimental data with assumed homogeneous depth distribution of Fe is marked with the continuous line.

Properties of FeCr,o solid samples have been studied by X-ray diffraction, 57Fe Mossbauer spectroscopy and magnetic measurements to stimulate the interaction of Fe with fullerene. FeCr,o samples have been prepared by decomposition of the 1,3-dipolar cycloadduct of the fullerene and ferrocene nitrile oxide. The components exhibit super paramagnetic properties originating from an interaction between FeCr,o complexes within the nano-particles. Each nano-particle consists of hundreds to thousands complexes (546). 

The recoilless nuclear resonance absorption of y-radiation (Mossbauer effect) has been verified for more than 40 elements, but only some 15 of them are suitable for practical applications [33, 34]. The limiting factors are the lifetime and the energy of the nuclear excited state involved in the Mossbauer transition. The lifetime determines the spectral line width, which should not exceed the hyperfine interaction energies to be observed. The transition energy of the y-quanta determines the recoil energy and thus the resonance effect [34]. 57Fe is by far the most suited and thus the most widely studied Mossbauer-active nuclide, and 57Fe Mossbauer spectroscopy has become a standard technique for the characterisation of SCO compounds of iron. 

Fe HB(C2H2N3)3 2] has been obtained by dehydration under heating of the low-spin hexahydrate. The crystal structure for this hexahydrate has been determined at room temperature [17]. It clearly contains Fe(II) ions in the low-spin state (average Fe-N distance=1.99 A). The dehydrated derivative [Fe HB(C2H2N3)3 2] has been reported to exhibit a very abrupt spin transition between 334-345 K via variable temperature UV-vis and 57Fe Mossbauer spectroscopy studies [19]. After the publication of a preliminary magnetic study in 1994 [19], a more detailed report appeared in 1998 [20]. 

It has been postulated that the origin of the two different high-spin Fe(II) doublets observed in the 57Fe Mossbauer spectra may be that a small fraction (about 6%) of the Fe(II) ions experience a different local environment, most likely in the distribution of the non-coordinating solvent and anion molecules, from that of the majority of the high-spin Fe(II) ions. 

Fig. 19 LIESST effect observed by 57Fe Mossbauer spectroscopy for [Fe(btzp)3](Cl04)2 at 5 K, without light irradiation (top) at 5 K, after light irradiation (middle) at 125 K, after light irradiation (bottom). (Reprinted with permission from [87]. Copyright (2000) American Chemical Society)... 

Most interestingly, [Fe(btzp)3](Cl04)2 is the first one-dimensional Fe(II) spin crossover compound, which shows the LIESST effect, detected in this instance by 57Fe Mossbauer spectroscopy (Fig. 19). 

Fig. 9 57Fe Mossbauer spectra of (bt, S) recorded at 4.2 K in zero-field (a) and in a magnetic field of 50 kOe (b). 57Fe Mossbauer spectra of (bpym, S) recorded at 4.2 K in zero-field (c) and in a magnetic field of 50 kOe (d). 57Fe Mossbauer spectra of (bpym, Se) recorded at 4.2 K in zero-field (e) and in a magnetic field of 50 kOe (f). LS in [HS-LS] and [LS-LS] pairs (grey), HS in [HS-LS] pairs (light grey), HS in [HS-HS] pairs (dark grey) (adapted from [11])...

Fig. 11 57Fe Mossbauer spectra of (bt, S) recorded at 4.2 K in zero-field before irradiation (a), immediately after irradiation (b), 6 days (c) and 11 days (d) after irradiation. Mossbauer subspectra correspond to HS species (grey), LS species (dark grey)...

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