Search

We report the results of the complex study of the bulk interior of Bursa L6 ordinary chondrite using optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, electron microprobe analysis (EMPA), X-ray diffraction (XRD), magnetization measurements, and Mossbauer spectroscopy. The main and minor iron-bearing phases and their chemical compositions were determined by these techniques. The detected iron-bearing phases in the bulk interior of Bursa L6 are the following: olivine; orthopyroxene; Ca-rich clinopyroxene; troilite; chromite; hercynite; ilmenite; the alpha(2)-Fe(Ni, Co), alpha-Fe(Ni, Co), and gamma-Fe(Ni, Co) phases; and ferrihydrite resulting from meteorite terrestrial weathering. Using the EMPA, the values of fayalite and ferrosilite were obtained as similar to 25.2% and similar to 21.4%, respectively. The unit cell parameters for silicate crystals were determined from XRD, then the Fe2+ and Mg2+ occupations of the M1 and M2 sites in these crystals were estimated. Further calculations of the ratios of the Fe2+ occupancies in the M1 and M2 sites in olivine and orthopyroxene based on XRD and Mossbauer spectroscopy appeared to be in a good agreement. The temperatures of equilibrium cation distributions for olivine and orthopyroxene obtained from these techniques are consistent: 623 K (XRD) and 625 K (Mossbauer spectroscopy) for olivine and 1138 K (XRD) and 1122 K (Mossbauer spectroscopy) for orthopyroxene., Ministry of Science and Higher Education of the Russian Federation [FEUZ-2020-0060, AAAA-A18-118053090045-8, AAAA-A19-119071090011-6]; Act 211 of the Government of the Russian Federation [02.A03.21.0006]; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [MFAG/113F035]; Ege University Scientific Research Projects Coordination UnitEge University [17-FEN-050]; Hungarian Ministry of Human Capacities [783-3/2018/FEKUTSRAT], The authors are grateful to G.A. Yakovlev (Ural Federal University, Ekaterinburg, Russian Federation) for the help with scanning electron microscopy. This work was supported by the Ministry of Science and Higher Education of the Russian Federation, project No FEUZ-2020-0060 and by Act 211 of the Government of the Russian Federation, contract No 02.A03.21.0006. O.U. was supported by the Scientific and Technological Research Council of Turkey (TUBITAK), project No MFAG/113F035 and by the Ege University Scientific Research Projects Coordination Unit, project No 17-FEN-050. D.A.Z. and A.A.M. were supported by the Ministry of Science and Higher Education of the Russian Federation, projects No AAAA-A18-118053090045-8 (D.A.Z.) and No AAAA-A19-119071090011-6 (D.A.Z. and A.A.M.). on behalf of two of us (~ A.Sz. and Z.D.), this work was completed in the ELTE Excellence Programme (783-3/2018/FEKUTSRAT) supported by the Hungarian Ministry of Human Capacities. This work was carried out within the Agreement of Cooperation between the Ural Federal University (Ekaterinburg) and the E_otv_os Lor~and University (Budapest).

Magnetization and low temperature in-field 57Fe Mossbauer spectroscopy measurements have been performed on a Fe[C(SiMe3)3]2/ferrihydrite hetero-mixture. The results indicate the presence of ferromagnetic coupling of magnetic moments involving Fe[C(SiMe3)3]2 with a hyperfine magnetic field of about 151 T, attributable mainly to the non-frozen atomic orbital contribution. The present findings show the sensitivity of single-ion molecular magnets to local alterations of their lattice-environment and might explain and reconcile some of the differences found in the literature for the observed bulk magnetic properties of the title Fe[C(SiMe3)3]2 compound.

A systematic study on anti-corrosion and anti-fouling effect of hydrophobic Langmuir-Blodgett and self-assembled molecular layers deposited on metal surfaces, as well as anti-microbial adhesion properties of coatings with biocide is presented. Both types of efficiencies produced by LB films are enhanced by Fe 3+ ions built in the molecular film. The quaternary ammonium type biocide embedded into the cross-linked gelatin decreased significantly the microbial adhesion, the biofilm formation.

The reaction of a diiron(III)-EDTA complex with H 2 O 2 in alkaline medium is studied by Mossbauer spectroscopy in conjunction with the rapid-freeze/quench technique in order to identify possible intermediate species during the formation and decomposition of the purple (EDTA)Fe I I I (η 2 -O 2 ) 3 - complex ion. Starting from the six-coordinate [Fe I I I EDTA] - species at acidic pH, it is demonstrated that mononuclear complexes formed at a pH of about 1 are convert into the diiron(m)-EDTA complex [(EDTA)Fe I I I -O-Fe I I I (EDTA)] 4 - upon raising the pH to around 10.4. H 2 O 2 reacts with the diiron(III) complex to give peroxide/hydroperoxide related adducts. Initially, the reaction tears apart the dimers to form a peroxo adduct, namely the seven-coordinate mononuclear [(EDTA)-Fe I I I (η 2 -O 2 )] 3 - , which is stable only at very high pH. The decomposition of this peroxo adduct gives two new species, which are reported for the first time. The Mossbauer parameters of these species suggest a six-coordinate μ-peroxodiiron(III) complex [(EDTA)Fe I I I -(OO)-Fe I I I (EDTA)] 4 - and a seven-coordinate μ-hydroxo-μ-peroxodiiron(III) complex [(EDTA)Fe I I I -(OO)(OH)-Fe I I I (EDTA)] 5 - . A badly resolved, extremely broad component is observed in the Mossbauer spectra during the conversion of the monomer to dimeric peroxo species, which may be attributed to the short-lived [[EDTA)Fe I I I l -OO] 3 - or [(EDTA)Fe I I I -OOH] 2 - intermediate species.

CD spectroscopic study of the secondary structure of partly adenylylated glutamine synthetase (GS) of the bacterium Azospirillum brasilense showed both the native and cation-free (EDTA-treated) enzyme to be highly structured (58 and 49% as α-helices, 10 and 20% as β-structure, respectively). Mg2+, Mn2+, or Co2+, when added to the native GS, had little effect on its CD spectrum, whereas their effects on the cation-free GS were more pronounced. Emission (57Co) Mossbauer spectroscopic (EMS) study of 57Co2+-doped cation-free GS in frozen solution and in the dried state gave similar spectra and Mossbauer parameters for the corresponding spectral components, reflecting the ability of the Co2+–enzyme complex to retain its properties upon drying. The EMS data show that (a) A. brasilense GS has 2 cation-binding sites per active center and (b) one site has a higher affinity to Co2+ than the other, in line with the data on other bacterial GSs. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004

The preparation and characterisation of two dinuclear iron(III) complexes with tripodal ligands 1,3-bis(2′-pyridylimino)isoindoline (indH) are presented. The μ-oxo-bridged diiron(III) complex [{FeCl(ind)}2O] (2) has been prepared by reacting FeCl3·6H2O with indH in methanol solution. Compound [{Fe(ind)(OAc)}2O] (3) was obtained from the reaction of 2 with CH3CO2Ag in THF. Both compounds were characterised by elemental analysis and UV/vis, IR, and Mossbauer spectroscopy. The X-ray structure analysis of [Fe2O(ind)2Cl2]·THF (2·THF) revealed a distorted trigonal bipyramidal (τ = 0.88) coordination geometry around the iron(III) ion. More importantly, 2 is a good functional model for the activation of small molecules as its 5-coordinate iron ions can easily coordinate such molecules. This is confirmed by the high catalase-like activity of 2, transforming 87% of the excess of H2O2 into O2 in 1 min. The complexes exhibited monooxygenase-like activity using H2O2 as the oxidant and oxidise alkanes to alcohols and ketones in acetonitrile in moderate yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)