Moessbauer spectroscopy

One-step hydroxylation of aromatic nucleus with nitrous oxide (N2O) is among recently discovered organic reactions. A high eflSciency of FeZSM-5 zeolites in this reaction relates to a pronounced biomimetic-type activity of iron complexes stabilized in ZSM-5 matrix. N2O decomposition on these complexes produces particular atomic oj gen form (a-oxygen), whose chemistry is similar to that performed by the active oxygen of enzyme monooxygenases. Room temperature oxidation reactions of a-oxygen as well as the data on the kinetic isotope effect and Moessbauer spectroscopy show FeZSM-5 zeolite to be a successfiil biomimetic model. 

A researcher in the field of heterogeneous catalysis, alongside the important studies of catalysts chemical properties (i.e., properties at a molecular level), inevitably encounters problems determining the catalyst structure at a supramolecular (textural) level. A powerful combination of physical and chemical methods (numerous variants x-ray diffraction (XRD), IR, nuclear magnetic resonance (NMR), XPS, EXAFS, ESR, Raman of Moessbauer spectroscopy, etc. and achievements of modem analytical chemistry) may be used to study the catalysts chemical and phase molecular structure. At the same time, characterizations of texture as a fairytale Cinderella fulfill the routine and very frequently senseless work, usually limited (obviously in our modem transcription) with electron microscopy, formal estimation of a surface area by a BET method, and eventually with porosimetry without any thorough insight. 

Ratera et al. (2003) discovered valence tautomerism in the ferrocene connected through the ethylenic bond with perchlorotriphenylmethyl radical. As ascertained by Moessbauer spectroscopy, this species in the solid state exhibited a thermally induced intramolecular electron transfer resulting in the formation of ferrocenium and perchlorotriphenylmethyl anion moieties. The authors used the initial species in its trans form. If the cis form would be available, the possibility of rotation around the ethylenic bond would be interesting to disclose. According to the authors, the interconversion of the cation-radical and anion centers proceeds gradually. At ambient temperature, equilibrium composition of the tautomers is achieved. This peculiarity is important with respect to potential technical applications. 

It should be pointed out that the treatment of phosphorus or sulfur donors bearing ferrocenyl groups with diiodine results in the formation of molecular charge-transfer adducts without simultaneous oxidation of the ferrocenyl groups (Durfey et al. 2000, Gridunova et al. 1982). At the same time, the reaction of 4-ferrocenyl-l,3-dithiolene-2-thione with diiodine leads to a charge-transfer complex in which the iron has been oxidized from Fe" to Fe ". This was confirmed by magnetic measurements and Moessbauer spectroscopy (Allen et al. 2003). 

Auger spectroscopy, ESCA, Moessbauer spectroscopy, electron microprobe, EDS... 

Iron bearing minerals in coal characterization using Moessbauer spectroscopy... 

The major minerals in coal are clays. Kaolinite is usually present in coal, but its identification by Moessbauer spectroscopy is very difficult due to the small amount of iron present and to surface contamination of the clay grains with iron oxides, mainly goethite. The other clay minerals present in coal are il-lite, chlorite and mixed clays. Their identification is not always easy. We have used a simple method, carrying out Moessbauer measurements at low temperatures and applying an external magnetic field to resolve the spectra and distinguish, for example, between illite and chlorite (11). 

Our objective was to measure the changes in the Moessbauer parameters as a function of temperature, solvent, H2 pressure and time. The first run consisted of a sample of about 300 mg/cm coal inside the reactor under 2 psi of N2 and no solvent. It was run between room temperature and 420° C, and maintained at 420°C for 10 minutes, long enough to obtain a Moessbauer spectrum. No evidence of transformation of FeS2 to pyrrhotite was detectable by Moessbauer spectroscopy. After rapidly returning the sample to room temperature a Moessbauer spectrum was taken, from which it was observed that the characteristic spectrum of FeS2 was retained with a very small amount of conversion to pyrrhotite. 

Huggins, F.E. Huffman, G.P. Lee, R.J. Scanning Electron Microscope-Based Automated Image Analysis (SEM-AIA) and Moessbauer Spectroscopy — Quantitative Characterization of Coal Min er als. In Coal and Coal Products Analytical Characterization Techniques, Fuller, E.L. Jr., Ed. ACS SYMP. SERIES 205, American Chemical Society Washington, D. C., 1982, pp. 

Fm] Fruehart, D., Chaudouet, R, Fruchart, R., Rouault, A., Senateur, J.P., Structural Studies on Cementite-Type Compounds Effects of Hydrogen on FeaC Followed by Neutron Diffiac-tion. Moessbauer Spectroscopy on FeCo2B et C03B Doped with Fe-57 , J. Solid State Chem., 51, 246-252 (1984) (Crys. Structure, Experimental, 35)... 

R308 C. E. Carraher Jr., F. D. Blum, M. B. Nair, G. Barot, A. Battin, T. Fiore, C. Pellerito, M. Scopelliti, A. Zhao, M. R. Roner and L. PeUerito, Solid State Analysis of Metal-Containing Polymers Employing Moessbauer Spectroscopy, Solid State NMR and F El TOF MALDI Mass Spectrometry , J. Inorg. Organomet. Polym. Mater., 2010, 20, 570. 

Fierro CA, Mohan M, Scherson DA (1990) In situ Moessbauer spectroscopy of a species irreversibly adsorbed on an electrode surface. Langmuir 6(8) 1338-1342... 

Moessbauer spectroscopy is readily applicable only for a few elements that exhibit suitable low-energy nuclear transitions on which the method is based— to Fe, Sb, and Sn. For measurements with Ru, Ir, Pt, and Au, one faces a number of complications (low measurement temperatures, dependence on sources with short half-lives, working at synchrotrons, etc.). Co is accessible by inverse Moessbauer spectroscopy, which requires preparation of the sample with Co, the isotope that decays into the source nucleus Fe. 

Chemical analysis of thick surface layers is traditionally used to analyze the amount of corrosion if the reaction products are insoluble. Techniques such as X-ray diffraction and SEM/EDX are frequently used, but also techniques that are not as common, e.g., Moessbauer spectroscopy, IR spectroscopy, or Raman microscopy (Kurosawa et al., 1995 Mansour and Melendres, 1995 Monzo et al., 1991 Persson and Leygraf, 1990 Matheison et al., 1993 Grundmeier etal., 1996 Sridhar and Dunn, 1997 Kasperek and Lenglet, 1997 Simpson and Melendres, 1996 Devine, 1994 Hoffmann and Stratmann, 1993). If the method is capable of localized analysis local corrosion phenomena are also detected. 

Review articles are invited on methods and applications of NMR, NQR, EPR, Moessbauer spectroscopy, etc. Special issues on selected topics are published under the guidance of guest editors. 

Moessbauer spectroscopy of, 216078j silica-supported, for Fischer-Tropsch reaction,... 

Goldanskii, V. I. and Berber, R. H., Chemical Application of Moessbauer Spectroscopy, Academic Press, New York, London, I968. 

O Neill, H. S. C., H. Annersten and D. Virgo (1992). The Temperature Dependence of the Cation Distribution in Magnesioferrite (MgFc204) from Powder XRD Structural Refinements and Moessbauer Spectroscopy . American Mineralogist 77 725-740. 

---