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Iron and 2-oxoglutarate dependent (Fe/2OG) enzymes exhibit an exceedingly broad reaction repertoire. The most prevalent reactivity is hydroxylation, but many other reactivities have also been discovered in recent years, including halogenation, desaturation, epoxidation, endoperoxidation, epimerization, and cyclization. To fully explore the reaction mechanisms that support such a diverse reactivities in Fe/2OG enzyme, it is necessary to utilize a multi-faceted research methodology, consisting of molecular probe design and synthesis, in vitro enzyme assay development, enzyme kinetics, spectroscopy, protein crystallography, and theoretical calculations. By using such a multi-faceted research approach, we have explored reaction mechanisms of desaturation and epoxidation catalyzed by a bi-functional Fe/2OG enzyme, AsqJ. Herein, we describe the experimental protocols and computational workflows used in our studies., (Copyright © 2024. Published by Elsevier Inc.)

Intravenous iron-carbohydrate nanomedicines are widely used to treat iron deficiency and iron deficiency anemia across a wide breadth of patient populations. These colloidal solutions of nanoparticles are complex drugs which inherently makes physicochemical characterization more challenging than small molecule drugs. There have been advancements in physicochemical characterization techniques such as dynamic light scattering and zeta potential measurement, that have provided a better understanding of the physical structure of these drug products in vitro. However, establishment and validation of complementary and orthogonal approaches are necessary to better understand the 3-dimensional physical structure of the iron-carbohydrate complexes, particularly with regard to their physical state in the context of the nanoparticle interaction with biological components such as whole blood (i.e. the nano-bio interface)., (Copyright © 2023. Published by Elsevier B.V.)

Pyrococcus furiosus is a hyperthermophilic anaerobic archaeon whose metabolism depends on whether elemental sulfur is (+S 0 ) or is not (-S 0 ) included in growth medium. Under +S 0 conditions, expression of respiratory hydrogenase declines while respiratory membrane-bound sulfane reductase and the putative iron-storage protein IssA increase. Our objective was to investigate the iron content of WT and ΔIssA cells under these growth conditions using Mössbauer spectroscopy. WT-S 0 cells contained ∼1 mM Fe, with ∼85% present as two spectroscopically distinct forms of S = 0 [Fe 4 S 4 ] 2+ clusters; the remainder was mainly high-spin Fe II . WT+S 0 cells contained 5 to 9 mM Fe, with 75 to 90% present as magnetically ordered thioferrate-like (TFL) iron nanoparticles. TFL iron was similar to chemically defined thioferrates; both consisted of Fe III ions coordinated by an S 4 environment, and both exhibited strong coupling between particles causing high applied fields to have little spectral effect. At high temperatures with magnetic hyperfine interactions abolished, TFL iron exhibited two doublets overlapping those of [Fe 4 S 4 ] 2+ clusters in -S 0 cells. This coincidence arose because of similar coordination environments of TFL iron and cluster iron. The TFL structure was more heterogeneous in the presence of IssA. Presented data suggest that IssA may coordinate insoluble iron sulfides as TFL iron, formed as a byproduct of anaerobic sulfur respiration under high iron conditions, which thereby reduces its toxicity to the cell. This was the first Mössbauer characterization of the ironome of an archaeon, and it illustrates differences relative to the iron content of better-studied bacteria such as Escherichia coli., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Ferritin-like carboxylate-bridged non-heme diiron enzymes activate O 2 for a variety of difficult reactions throughout nature. These reactions often begin by abstraction of hydrogen from strong CH bonds. The enzymes activate O 2 at their diferrous cofactors to form canonical diferric peroxo intermediates, with a range of possible coordination modes. Herein, we explore the ability of high-energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS) to provide insight into the nature of peroxo level intermediates in non-heme diiron proteins. Freeze quenched (FQ) peroxo intermediates from p-aminobenzoate N-oxygenase (AurF), aldehyde-deformylating oxygenase (ADO), and the β subunit of class Ia ribonucleotide reductase from Escherichia coli (Ecβ) are investigated. All three intermediates are proposed to adopt different peroxo binding modes, and each exhibit different Fe Kα HERFD XAS pre-edge features and intensities. As these FQ-trapped samples consist of multiple species, deconvolution of HERFD XAS spectra based on speciation, as determined by Mössbauer spectroscopy, is also necessitated - yielding 'pure' diferric peroxo HERFD XAS spectra from dilute protein samples. Finally, the impact of a given peroxo coordination mode on the HERFD XAS pre-edge energy and intensity is evaluated through time-dependent density functional theory (TDDFT) calculations of the XAS spectra on a series of hypothetical model complexes, which span a full range of possible peroxo coordination modes to a diferric core. The utility of HERFD XAS for future studies of enzymatic intermediates is discussed., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Wetlands mitigate the migration of groundwater contaminants through a series of biogeochemical gradients that enhance multiple contaminant-binding processes. The hypothesis of this study was that wetland plant roots contribute organic carbon and release O2 within the rhizosphere (plant-impact soil zone) that promote the formation of Fe(III)-(oxyhydr)oxides. In turn, these Fe(III)-(oxyhydr)oxides stabilize organic matter that together contribute to contaminant immobilization. Mineralogy and U binding environments of the rhizosphere were evaluated in samples collected from contaminated and non-contaminated areas of a wetland on the Savannah River Site in South Carolina. Based on Mössbauer spectroscopy, rhizosphere soil was greatly enriched with nanogoethite, ferrihydrite-like nanoparticulates, and hematite, with negligible Fe(II) present. X-ray computed tomography and various microscopy techniques showed that root plaques were tens-of-microns thick and consisted of highly oriented Fe-nanoparticles, suggesting that the roots were involved in creating the biogeochemical conditions conducive to the nanoparticle formation. XAS showed that a majority of the U in the bulk wetland soil was in the +6 oxidation state and was not well correlated spatially to Fe concentrations. SEM/EDS confirm that U was enriched on root plaques, where it was always found in association with P. Together these findings support our hypothesis and suggest that plants can alter mineralogical conditions that may be conducive to contaminant immobilization in wetlands., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Four (57)Fe-labeled tetrachloroferrates(III) of organic cations (1-butyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, 1-methyl-1-propylpyrrolidinium, tetraphenylphosphonium) were examined by temperature-dependent Mössbauer spectroscopy. The hyperfine and dynamic parameters of the iron(III) site were determined. Single crystal X-ray diffraction data of [Ph(4)P][FeCl(4)] were collected at four temperatures (295, 223, 173, and 123 K), and the dynamics of the iron atom inferred from the Mössbauer data and the single crystal U(i,j) parameters have been compared.

Compounds that exhibit the spin crossover effect are known to show a change of spin states through external stimuli. This reversible switching of spin states is accompanied by a change of the properties of the compound. Complexes, like iron (II)-triazole complexes, that exhibit this behavior at ambient temperature are often discussed for potential applications. In previous studies we synthesized iron (II)-triazole complexes and implemented them into electrospun nanofibers. We used Mössbauer spectroscopy in first studies to prove a successful implementation with maintaining spin crossover properties. Further studies from us showed that it is possible to use different electrospinning methods to either do a implementation or a deposition of the synthesized solid SCO material into or onto the polymer nanofibers. We now used a solvent in which both, the used iron (II)-triazole complex [Fe(atrz)3](2 ns)2 and three different polymers (Polyacrylonitrile, Polymethylmethacrylate and Polyvinylpyrrolidone), are soluble. This shall lead to a higher homogeneous distribution of the complex along the nanofibers. Mössbauer spectroscopy and other measurements are therefore in use to show a successful implementation without any significant changes to the complex. [ABSTRACT FROM AUTHOR]

Two trinuclear oxo-centred iron(III) coordination compounds of monensic and salinomycinic acids (HL) were synthesized and their spectral properties were studied using physicochemical/thermal methods (FT–IR, TG–DTA, TG–MS, EPR, Mössbauer spectroscopy, powder XRD) and elemental analysis. The data suggested the formation of [Fe3(µ3–O)L3(OH)4] and the probable complex structures were modelled using the DFT method. The computed spectral parameters of the optimized constructs were compared to the experimentally measured ones. In each complex, three metal centres were joined together at the axial position by a μ3–O unit to form a {Fe3O}7+ core. The antibiotics monoanions served as bidentate ligands through the carboxylate and hydroxyl groups located at the termini. The carboxylate moieties played a dual role bridging each two metal centres. Hydroxide anions secured the overall neutral character of the coordination species. Mössbauer spectra displayed asymmetric quadrupole doublets that were consistent with the existence of two types of high-spin iron(III) sites with different environments—two Fe[O5] and one Fe[O6] centres. The solid-state EPR studies confirmed the +3 oxidation state of iron with a total spin St = 5/2 per trinuclear cluster. The studied complexes are the first iron(III) coordination compounds of monensin and salinomycin reported so far. [ABSTRACT FROM AUTHOR]

The main aims of this work were the synthesis and characterization of iron(III) complexes with a ditopic ligand H2L consisting of a bis(salicylidene) isothiosemicarbazide moiety with a N2O2 binding site and a crown-ether (O6) moiety. A series of high-spin iron(III) complexes, i.e., [FeIIILClBa(CH3OH)(H2O)0.5(ZnCl4)] (1), [FeIIILCl] (2), [FeIIIL(N3)] (3) and [(FeIIIL)2O] (4), were synthesized. The complexes were characterized by mass spectrometry, IR and UV--Vis spectroscopy, variable temperature (VT) magnetic susceptibility measurements, Mössbauer spectroscopy, single crystal X-ray diffraction and cyclic voltammetry. [ABSTRACT FROM AUTHOR]

The direct oxidation of methane to methanol (MTM) is a significant challenge in catalysis and holds profound economic implications for the modern chemical industry. Bioinspired metal–organic frameworks (MOFs) with active iron and copper sites have emerged as innovative catalytic platforms capable of facilitating MTM conversion under mild conditions. This review discusses the current state of the art in applying MOFs with iron and copper catalytic centers to effectuate the MTM reaction, with a focus on the diverse spectroscopic techniques employed to uncover the electronic and structural properties of MOF catalysts at a microscopic level. We explore the synthetic strategies employed to incorporate iron and copper sites into various MOF topologies and explore the efficiency and selectivity of the MOFs embedded with iron and copper in acting as catalysts, as well as the ensuing MTM reaction mechanisms based on spectroscopic characterizations supported by theory. In particular, we show how integrating complementary spectroscopic tools that probe varying regions of the electromagnetic spectrum can be exceptionally conducive to achieving a comprehensive understanding of the crucial reaction pathways and intermediates. Finally, we provide a critical perspective on future directions to advance the use of MOFs to accomplish the MTM reaction. [ABSTRACT FROM AUTHOR]

AyB1−yCxFe2−xO4 (C=Ho,Gd,Al) ferrite powders have been synthesized by the sol-gel combustion route. The X-ray diffraction of the CoHoxFe2−xO4 (x = 0~0.08) results indicated the compositions of single-phase cubic ferrites. The saturation magnetisation of CoHoxFe2−xO4 decreased by the Ho3+ ions, and the coercivity increased initially and then decreased with the increase of the calcination temperature. The Mössbauer spectra indicated that CoHoxFe2−xO4 displays a ferrimagnetic behaviour with two normal split Zeeman sextets. The magnetic hyperfine field tends to decrease by Ho3+ substitution owing to the decrease of the A–B super-exchange by the paramagnetic rare earth Ho3+ ions. The value of the quadrupole shift was very small in the CoHoxFe2−xO4 specimens, indicating that the symmetry of the electric field around the nucleus is good in the cobalt ferrites. The absorption area of the Mössbauer spectra changed with increasing Ho3+ substitution, indicating that the substitution influences the fraction of iron ions at tetrahedral A and octahedral B sites. The X-ray diffraction of Mg0.5Zn0.5CxFe2−xO4(C=Gd,Al) results confirmed the compositions of single-phase cubic ferrites. The variation of the average crystalline size and lattice constant are related to the doping of gadolinium ions and aluminum ions. With increasing gadolinium ions and aluminum ions, the coercivity increased and the saturation magnetization underwent a significant change. The saturation magnetization of AlMg0.5Zn0.5FeO4 ferrite reached a minimum value (MS= 1.94 mu/g). The sample exhibited ferrimagnetic and paramagnetic character with the replacement with Gd3+ ions, that sample exhibited paramagnetic character with the replacement with Al3+ ions, and the isomer shift values indicated that iron is in the form of Fe3+ ions. [ABSTRACT FROM AUTHOR]

We explore the solventless synthesis of iron oxide nanomaterials obtained on thermal conversion of iron(III)citrate in presence of malonic acid and glucose as co-precursors in varying weight ratios and physical characterization of the materials obtained. Pure phase of hematite was found only for a particular combination of precursor and co-precursor and else a mixture of hematite and magnetite. Significant effect of the co-precursors on the nature and size of the synthesized materials was noticed. Gradual conversion of hematite to magnetite with increasing amount of co-precursor was established. Morin transition was observed in the temperature dependent magnetization study for the hematite materials. Absorption spectroscopy exhibited three different electronic transitions that take place within the 3d5 shell of the octahedrally coordinated Fe3+ ions for hematite materials. The optical (direct and indirect) band gaps estimated from the Tauc's plot showed particle size dependence. From photoluminescence study the transitions of trapped electrons in various defect states of oxygen vacancies were observed which led to the appearance of nonradiative peaks. In the Raman spectra the significant bands of hematite (A1g and Eg bands) were noted. From morphology study the hematite nanomaterials appear as clusters of large irregular shaped particles of various sizes. Formation of hematite nanomaterials as observed by XRD studies was supplemented by the SAED patterns obtained in the HRTEM study. Present study established that nano-sized pure hematite materials can be thermally synthesized at comparatively lower temperature on thermal decomposition of iron(III)citrate by varying the weight ratio of suitable co-precursors. [ABSTRACT FROM AUTHOR]

Novel iron(II) coordination compounds containing a ligand 2,6-bis(1H-imidazol-2-yl)pyridine (L), having such a composition as [FeL2]SO4·0.5H2O, [FeL2]Br2·H2O, [FeL2](ReO4)2, [FeL2]B10H10∙H2O, [FeL2]B12H12∙1.5H2O had been synthesized and studied using UV-Vis (diffuse reflectance), infrared, extended X-ray absorption fine structure (EXAFS), and Mössbauer spectroscopy methods, as well as X-ray diffraction and static magnetic susceptibility methods. The analysis of the μeff(T) dependence in the temperature range of 80–600 K have shown that all the obtained complexes exhibit a high-temperature spin crossover 1A1 ↔ 5T2. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • XRF, EPR and Mössbauer provides information on iron chemical state in fresh, equilibrium and artificially metalized FCC catalysts. • Low-field EPR in FCC catalysts is exclusively associated to meta-kaolinite phase; its intensity serves as an indicator of the redox environment. • Contaminant iron is mostly deposited on equilibrium catalysts as ferri- and superparamagnetic maghemite. • The redox environment during cracking and regeneration cycles determines which species is preferentially formed. Abstract Amongst the contaminant transition metals that deposit onto the fluid catalytic cracking (FCC) catalyst, iron is well-known for its accumulation on the outer surface, negatively affecting accessibility of reactants to the interior of the porous particles and even causing fluidization problems in the circulating unit. Earlier studies have been dedicated to understand the complex deposition mechanism of iron in FCC particles, but only a few was devoted to determine the crystalline phases and the valence states of the deposited Fe during its operation under alternate redox conditions. Besides, the co-existing structural iron in the manufactured catalyst (fresh) makes such studies even more challenging. To better elucidate this field, we present in this paper a combined investigation using X-ray fluorescence (XRF), electron paramagnetic resonance (EPR) and Mössbauer spectroscopy (MS) in fresh, artificially metalized samples and deactivated catalysts collected from the industrial FCC process (E-cat). Using as subsidiary information the characterization of fresh and laboratory impregnated samples submitted to different redox environments at 750 °C, the investigation of E-cats from two refineries working in partial and full burn regeneration mode allowed us to conclude that contaminant iron is mostly deposited as maghemite (γ-Fe 2 O 3) with spinel structure in both its forms: the ferrimagnetic and the superparamagnetic phase, this latter associated to nanosized crystals. The structural Fe(III) in meta-kaolinite from the original catalyst is mostly transformed to Fe(II), indicating that in real FCC unit the regeneration conditions are not severe enough to fully oxidize the Fe species formed in the reductive conditions of the FCC cracking step. Moreover, evidences suggested that the ferrimagnetic form of maghemite is preferentially formed in the reaction zone and it is more or less converted in the regenerator into the superparamagnetic species, more resistant to the oxidizing condition. [ABSTRACT FROM AUTHOR]

The phase Na5FeSi4O12 [pentasodium iron(III) silicate] crystallizes readily from the Na2O–Fe2O3–SiO2 glass system in a relatively large compositional range. However, its crystal structure and properties have not been studied in detail since its discovery in 1930. In this work, the Na5FeSi4O12 phase was crystallized from a host glass with 5Na2O·Fe2O3·8SiO2 stoichiometry, and both the glass and the crystal were studied. It was found that the Na5FeSi4O12 phase crystallizes at ∼720 °C from the glass and melts at ∼830 °C when heated at a rate of 10 °C min−1. The crystal structure was solved using single‐crystal X‐ray diffraction and the refined data are reported for the first time for the Na5FeSi4O12 phase. It exhibits trigonal symmetry, space group Rc, with a = 21.418 and c = 12.2911 Å. The Na atoms located between adjacent structural channels exhibit positional disorder and splitting which was only refined by using low‐temperature data collection (150 K). While ∼7% of the total Fe cations occur as Fe2+ in the glass, four‐coordinated Fe3+ constitutes ∼93% of the total Fe cations. However, iron in the crystal, which exhibits a paramagnetic behavior, is solely present as six‐coordinated Fe3+. The magnetic and vibrational properties of the glass and crystal are discussed to provide additional insight into the structure. The crystal structure of Na5FeSi4O12, crystallized from a stoichiometric glass, was solved by single‐crystal X‐ray diffraction. Fe is present in its trivalent state and occupies a single unique octahedral site, while Na occurs in several disordered independent positions. [ABSTRACT FROM AUTHOR]

Oxygen fugacity (fo2) exerts first-order control on the geochemical evolution of planetary interiors, and the Fe3+/ΣFe ratios of silicate glasses provide a useful proxy for fO2. Fe K-edge micro-X-ray absorption near-edge structure (XANES) spectroscopy allows researchers to micro-analytically determine the Fe3+/ΣFe ratios of silicate glasses with high precision. In this study we characterize hydrous and anhydrous basalt glass standards with Mössbauer and XANES spectroscopy and show that synchrotron radiation causes progressive changes to the XANES spectra of hydrous glasses as a function of radiation dose (here defined as total photons delivered per square micrometer), water concentration, and initial Fe3+/ΣFe ratio. We report experiments from eight different radiation dose conditions and show that Fe in hydrous silicate glasses can undergo rapid oxidation upon exposure to radiation. The rate and degree of oxidation correlates with radiation dose and the product of water concentration and ferrous/ferric iron oxide ratio on a molar basis (Φ = XHO0.5·XFeO/XFeO1.5). For example, a basalt glass with 4.9 wt% dissolved H2O and Fe3+/ΣFe = 0.19 from its Mössbauer spectrum may appear to have Fe3+/ΣFe ≥ 0.35 when analyzed over several minutes at a nominal flux density of ~2 × 109 photons/s/μm2. This radiation-induced increase in Fe3+/ΣFe ratio would lead to overestimation of fO2 by about two orders of magnitude, with dramatic consequences for the interpretation of geological processes. The sample area exposed to radiation shows measureable hydrogen loss, consistent with radiation-induced breaking of O–H bonds, associated H migration and loss, and oxidation of Fe2+. This mechanism is consistent with the observation that anhydrous glasses show no damage under any beam conditions. Cryogenic cooling does not mitigate, but rather accelerates, iron oxidation. The effects of beam damage appear to persist indefinitely. We detect beam damage at the lowest photon flux densities tested (3 × 106 photons/s/ μm2); however, at flux densities ≤6 × 107 photons/s/µm2, the hydrous glass calibration curve defined by the centroid (derived from XANES spectra) and Fe3+/SFe ratios (derived from Mössbauer spectra) is indistinguishable from the anhydrous calibration curve within the accuracy achievable with Mössbauer spectroscopy. Thus, published Fe3+/ΣFe ratios from hydrous glasses measured at low photon flux densities are likely to be accurate within measurement uncertainty with respect to what would have been measured by Mössbauer spectroscopy. These new results demonstrate that to obtain accurate Fe3+/ΣFe ratios from hydrous, mafic, silicate glasses, it is first necessary to carefully monitor changes in the XANES spectra as a function of incident dose (e.g., fixed-energy scan). Defocusing and attenuating the beam may prevent significant oxidation of Fe in mafic water-bearing glasses. [ABSTRACT FROM AUTHOR]

Fe(III)-oxides and Fe(III)-bearing phyllosilicates are the two major iron sources utilized as electron acceptors by dissimilatory iron-reducing bacteria (DIRB) in anoxic soils and sediments. Although there have been many studies on microbial Fe(III)-oxide and Fe(III)-phyllosilicate reduction with both natural and specimen materials, no controlled experimental information is available on the interaction between these two phases when both are available for microbial reduction. In this study, the model DIRBGeobacter sulfurreducenswas used to examine the pathways of Fe(III) reduction in Fe(III)-oxide stripped subsurface sediment that was coated with different amounts of synthetic high surface area (HSA) goethite. Cryogenic (12K)57Fe Mössbauer spectroscopy was used to determine changes in the relative abundances of Fe(III)-oxide, Fe(III)-phyllosilicate, and phyllosilicate-associated Fe(II) [Fe(II)-phyllosilicate] in bioreduced samples. Analogous Mössbauer analyses were performed on samples from abiotic Fe(II) sorption experiments in which sediments were exposed to a quantity of exogenous soluble Fe(II) (FeCl2⋅2H2O) comparable to the amount of Fe(II) produced during microbial reduction. A Fe partitioning model was developed to analyze the fate of Fe(II) and assess the potential for abiotic Fe(II)-catalyzed reduction of Fe(III)-phyllosilicates. The microbial reduction experiments indicated that although reduction of Fe(III)-oxide accounted for virtually all of the observed bulk Fe(III) reduction activity, there was no significant abiotic electron transfer between oxide-derived Fe(II) and Fe(III)-phyllosilicatesilicates, with 26–87% of biogenic Fe(II) appearing as sorbed Fe(II) in the Fe(II)-phyllosilicate pool. In contrast, the abiotic Fe(II) sorption experiments showed that 41 and 24% of the added Fe(II) engaged in electron transfer to Fe(III)-phyllosilicate surfaces in synthetic goethite-coated and uncoated sediment. Differences in the rate of Fe(II) addition and system redox potential may account for the microbial and abiotic reaction systems. Our experiments provide new insight into pathways for Fe(III) reduction in mixed Fe(III)-oxide/Fe(III)-phyllosilicate assemblages, and provide key mechanistic insight for interpreting microbial reduction experiments and field data from complex natural soils and sediments. [ABSTRACT FROM AUTHOR]

Iron(II) complexes of the type [Fe(L)(NCS)2] with tetradentate ligands L are well known to show spin crossover properties. However, this behavior is quite sensitive in regard to small changes of the ligand system. Starting from the thoroughly investigated complex [Fe(tmpa)(NCS)2] [tmpa = tris(2-pyridylmethyl)amine, also abbreviated as tpa in the literature] we modified the ligand by increasing systematically the chelate ring sizes from 5 to 6 thus obtaining complexes [Fe(pmea)(NCS)2], [Fe(pmap)(NCS)2], and [Fe(tepa)(NCS)2] [pmea = N,N-bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine, pmap = N,N-bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine, and tepa = tris[2- (2-pyridyl)ethyl]amine]. All complexes were structurally characterized and spin crossover properties were investigated using Möβbauer spectroscopy, magnetic measurements, and IR/Raman analyses. The results demonstrated that only the iron complexes with tmpa and pmea showed spin crossover properties, whereas the complexes with the ligands pmap and tepa only formed high spin complexes. Furthermore, DFT calculations supported these findings demonstrating again the strong influence of ligand environment. Herein the effect of increasing the chelate ring sizes in iron(II) isothiocyanato complexes with tetradentate tripyridyl-alkylamine ligands is clearly demonstrated. [ABSTRACT FROM AUTHOR]

We report a study of the structural and magnetic properties, as well as of the heat release, of an iron/wüstite composite, prepared from iron powder and water by high energy mechanical milling. We identify that the produced sample consists of α -Fe nanoparticles embedded in a wüstite matrix and has high stability in time. Moreover, we observe that it presents noticeable features, as exchange bias effect at low temperatures and, when an alternating magnetic field is applied, its temperature reaches ∼46 °C in ∼600 s. Thus, the results and the possibility of tuning the magnetic properties of α -Fe nanoparticles embedded in a wüstite matrix, through interface interactions, place this system as a very attractive candidate for biomedical applications such as magnetic hyperthermia agent for cancer therapy. [ABSTRACT FROM AUTHOR]

We have studied the speciation of carbon monoxide in both Fe-bearing and Fe-free basaltic glasses using Raman, FTIR, and Mössbauer spectroscopy. We show that a band at 2110 cm-1 in the Raman spectrum and another band at 2210 cm-1 in the FTIR spectrum occur both in the Fe-bearing and Fe-free samples, implying that they cannot be due to any Fe-bearing species. This observation is consistent with 57Fe Mössbauer spectra, which do not show any evidence for Fe species with zero isomer shift, as expected for carbonyls. Thermodynamic calculations show that iron carbonyl in basaltic melts under crustal and upper mantle conditions may only be a trace species. Rather than being due to distinct chemical species, the range of vibrational frequencies observed for carbon monoxide in silicate glasses appears to be due to rather subtle interactions of the CO molecule with the matrix. Similar effects are known from the extensive literature on carbon monoxide adsorption on oxides and other surfaces. In the melt at high temperature, there is likely little interaction of the CO molecule with the silicate matrix and solubility may be largely controlled by pressure, temperature, and the overall polymerization or ionic porosity of the melt. [ABSTRACT FROM AUTHOR]

Fossil-bearing shale specimens that include sulfides in their compositions are chemically reactive and sometimes also mechanically fragile. This decay is often related to iron sulfate efflorescence resulting from the oxidation of sulfide compounds. The processes underlying these degradations are poorly known, thus impeding the elaboration of curative or preventive treatments. The present contribution aims to identify the origin of museum specimen alterations. It focuses on the Flouest collection housed at the Muséum national d’Histoire naturelle (MNHN, Paris, France) and originating from the Autun Basin (Saône-et-Loire, France; Permian). To evaluate the alteration of MNHN specimens, it appeared necessary to compare their composition with that of unaltered shale so as to identify chemical changes occurring during ageing. Therefore new material was collected in the Autun Basin, among others on the locality of Muse that corresponds to the same lithostratigraphic unit than that of the MNHN specimens. The present article focuses on the combined use of X-ray diffraction and Mössbauer spectrometry for characterizing the speciation and reactivity of iron within the shale matrix. Crystalline pyrite was evidenced by X-ray diffraction (XRD) on one sample only and elemental analysis showed that iron is present in large excess with respect to sulfur. Iron sulfide, if present, involves a minor fraction of iron. A more complete characterization of iron-bearing phases was achieved with Mössbauer measurements, showing that a great part of iron, between approx. 25% and 65%, corresponds to iron(II) incorporated in clay minerals (illite and vermiculite were detected by XRD). Similar percentages of these iron(II) signatures were found for MNHN specimens and new shale samples, suggesting that iron(II) present in clays is not affected by ageing. This point is complementary highlighted by porosity and permeability measurements showing that the pore size distribution of the samples originating from Muse is mostly unimodal and narrow (average radius below 10 nm). As a result, the shale is poorly permeable to water and almost fully impermeable to oxygen. This might explain the poor reactivity of iron(II) during ageing. Iron(III)-bearing phases were also identified. On new shale samples, they exclusively involve clay minerals. On MNHN specimens, poorly crystallized iron(III) sulfates are additionally observed. The presence of iron(III) oxyhydroxides appeared unlikely. The change of iron speciation provoked by the alteration of the matrix also mainly corresponds to the emergence of more or less crystallized iron(III) sulfates probably formed though iron sulfide oxidation. These phases however remain in the inner part of shale and cannot account for the large efflorescence of iron(II) sulfates observed nearby the fossil. [ABSTRACT FROM AUTHOR]

Effects of hafnium addition on the structure and properties of iron borophosphate glasses with nominal composition of xHfO 2 –yB 2 O 3 –[40–(x + y)]Fe 2 O 3 –60P 2 O 5 (x = 0–8, mol%) and xHfO 2 –yB 2 O 3 –[40–(x + y)][40Fe 2 O 3 –60P 2 O 5 ] (x = 2–6, mol%) have been investigated by XRD, DTA, IR, SEM and Mössbauer spectroscopy. There were some surface crystallizations on some of the samples containing high amounts of Hf and B. XRD spectra revealed that HfP 2 O 7 crystallized in the glass matrix when HfO 2 content was above 2 mol% even when there was no surface crystallization and samples looked glassy. SEM-EDAX image-analyses supported the formation of the HfP 2 O 7 phase. Dissolution rates of Hf-containing iron borophosphate glasses were in the 10 − 9 –10 − 10 g/cm 2 min range which shows that the existence of the crystalline HfP 2 O 7 phase in the glass matrix has not degraded the aqueous chemical durability of these glasses. The band observed at ~ 984 cm − 1 in the IR spectra of Hf containing samples was attributed to the Hf–O–P bonds in HfP 2 O 7 . Iron existed in two valence states, i.e. Fe 2 + and Fe 3 + and Mössbauer hyperfine parameters indicated that both ions have octahedral coordinations in the samples studied. [ABSTRACT FROM AUTHOR]

Redox activation (reduction of structural Fe) of smectites greatly alters their chemical reactivity and physical properties, which may be exploited for various environmental, agricultural or industrial purposes. Their re-oxidation during preparation, characterization, and use is, however, a significant risk to their utility. In this study, methods and apparatus were developed and described which mitigated reoxidation. Ferruginous smectite (sample SWa-1, Na saturated) was used as the model smectite. It was reduced with sodium dithionite in a citrate-bicarbonate buffer solution at 70°C for 4 h, which achieved a maximum Fe(II)/total Fe ratio of 0.9113±0.0048. The first step in rendering reduced samples useful is to remove from them the reducing agents and other solutes present during reduction. This was accomplished in the present study by reducing the sample in an inert-atmosphere reaction tube (IRT) (a 50 mL centrifuge tube equipped with a removable septum cap), then removing solutes from the suspension by centrifuge washing. The washing steps were performed with the aid of a controlled-atmosphere liquid exchanger (CALE) which provided connections between the sample suspension and deoxygenated solutions. The reduced state was measured by 1,10-phenanthroline or by Mössbauer spectroscopy at 77 K to give Fe(II)/total Fe ratios. Some samples were freeze dried after washing. Results revealed that if reduced smectites are washed without protection from atmospheric O2, the extent of reoxidation is on the order of 40 to 60%. If the sample is subsequently dried, reoxidation increases to more than 76%. If the sample is protected using the IRT and the CALE, however, reoxidation is decreased to less than 2%. Freeze drying in a glove box allowed reoxidaton to increase to slightly more than 10%. These results indicate that more reoxidation occurred during the drying stage than during the washing stage. These observations lead to the conclusions that (1) protection of reduced samples from atmospheric O2 is essential if extensive reoxidation is to be prevented, and (2) the methods and apparatus described herein are effective for accomplishing that purpose in abiotically reduced smectites. They may also be effective if applied to microbially reduced smectites. [ABSTRACT FROM AUTHOR]

Although Fe-sulfate minerals occur only rarely on Earth as alteration products of sulfidic basalts or in hydrothermal systems, multiple lines of evidence point to the importance of Fe- (and other) sulfate minerals on the surface of Mars. One such martian data set comes from the MIMOS II Mössbauer spectrometers on the Mars Exploration Rovers, which acquired hundreds of spectra from the martian surface at two locations. Interpretation of those spectra has been limited by the lack of a comprehensive set of laboratory analog spectra of the broad range of naturally occurring sulfate minerals. Accordingly, this study reports Mössbauer data of 98 samples representing 47 different sulfate mineral species, all containing six- or higher-coordinated Fe. The resultant Mössbauer parameters are related to the local polyhedral environment around the Fe cation in each mineral to explain variations in spectral characteristics. Results show that the size of the coordination polyhedron is the best predictor of quadrupole splitting, which increases with both octahedral volume and mean bond length. Species within groups of structurally similar minerals are shown to have comparable spectral peaks that generally fall within small ranges. Although coordination polyhedron geometry is not necessarily unique to any particular mineral species or group, Mössbauer data can be used to help constrain mineral identifications from martian spectra. The number of mineral species is large, but the range of crystal structures and hyperfine parameters may be small, so that in many cases, individual minerals cannot be uniquely fingerprinted. Examples would include quenstedtite, coquimbite, kornelite, and lausenite, which have indistinguishable spectra, as do apjohnite, bilinite, dietrichite, and römerite. Overlap of Mössbauer parameters is a particular complication for identification of Fe3+-rich phases because the range of Mössbauer parameters for Fe3+ in any coordination number is so small. Previous analyses of martian Mössbauer spectra reported the presence of jarosite (Klingelhöfer et al. 2004; Morris et al. 2004) and an unspecific ferric sulfate (Morris et al. 2008). New data presented here indicate that botryogen, metasideronatrite, and slavikite exhibit Mössbauer spectra similar to those attributed to jarosite at Meridiani Planum. Fibroferrite and rhomboclase have parameters similar to those observed at Arad Samra, and copiapite and parabutlerite could be present at Tyrone Mount Darwin and Berkner Island. Unique mineral identifications are generally not possible from Mössbauer data alone, particularly for paramagnetic phases, although combining Mössbauer results with other data sets enables a greater level of confidence in constraining mineralogy. This study provides a new expansive data set for future interpretation of iron sulfates on Mars. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel method for detecting the solid–liquid phase boundary of compressed iron at high temperatures using synchrotron Mössbauer spectroscopy (SMS). Our approach is unique because the dynamics of the iron atoms are monitored. This process is described by the Lamb–Mössbauer factor, which is related to the mean-square displacement of the iron atoms. Focused synchrotron radiation with 1meV bandwidth passes through a laser-heated 57Fe sample inside a diamond-anvil cell, and the characteristic SMS time signature vanishes when melting occurs. At our highest compression measurement and considering thermal pressure, we find the melting point of iron to be T M =3025±115K at P=82±5GPa. When compared with previously reported melting points for iron using static compression methods with different criteria for melting, our melting trend defines a steeper positive slope as a function of pressure. The obtained melting temperatures represent a significant step toward a reliable melting curve of iron at Earth''s core conditions. For other terrestrial planets possessing cores with liquid portions rich in metallic iron, such as Mercury and Mars, the higher melting temperatures for compressed iron may imply warmer internal temperatures. [Copyright &y& Elsevier]

Abstract: We discuss here the chemical oxidation of a high-spin iron(II) complex containing the 1,3-bis(2′-benzimidazolylimino)isoindoline ligand (HL1) using tris(4-bromophenyl)aminium hexachloroantimonate (Magic Blue). The product was X-ray structurally, spectroscopically (Mössbauer, FT-IR, UV–vis) and electrochemically characterized and can be formulated as [FeIII(L1)2][FeIII(L1H−2)(L1)] (1), a low-spin iron(III) 1D coordination polymer with strong H-bonds between ligands and N,N-dimethylformamide (DMF) solvent molecules in the solid phase. The redox potential of the [FeII(L1)2] complex at −407mV vs. ferrocene in DMF is shifted to the anodic direction only by 12mV in the case of 1 against the expected cathodic shift upon proton loss from the ligand. The difference in the spin state of [FeII(L1)2] and 1, and the impact of H-bonds (detected in the crystal structure) that are able to facilitate proton-coupled electron transfer have been considered as plausible explanations. [Copyright &y& Elsevier]

Abstract: CuIn1−x Fe x S2(x=0–0.30) was synthesized via high-temperature, solid-state synthesis. Phase-pure materials were found in samples where x=0–0.15, after which a secondary phase became apparent. The materials were characterized with the use of X-ray powder diffraction (XRPD), and Reitveld refinement revealed a linear decrease in unit cell volume as the amount of iron substitution increases in accordance with Vegard’s Law. Inductively coupled plasma (ICP) confirms that the actual stoichiometry is close to the nominal composition of the materials. The temperature for both the chalcopyrite-to-sphalerite and the sphalerite-to-wurtzite phase transitions decreases with increasing iron substitution for indium. These findings suggest that the Fe is being randomly incorporated into the crystal structure of the CuInS2. X-ray photoelectron spectroscopy (XPS) measurements were used to determine the oxidation state of the ions (Cu1+, In3+, and S2−), and Fe57 Mössbauer spectroscopy verified that the iron is in the 3+ oxidation state. Band gaps of the solid solution were estimated to be in the range of 0.70–0.85eV. Rietveld refinement of neutron diffraction data indicates that the iron is occupying the In site within the chalcopyrite structure. [Copyright &y& Elsevier]

Abstract: Mössbauer and Electron paramagnetic resonance (EPR) spectroscopy studies of iron status in doped sodium-silicate glasses (100− x, mol%)Na2Oic>x, mol%)SiO2 ic>y, wt.%) Fe2O3 (x =75; 81; y =0.05–13) were made as a function of glass matrix and total iron content. 5 [5] Total iron content is expressed as Fe2O3 in the paper. Mössbauer spectroscopy identified three signals: Fe3+ doublet, Fe2+ doublet and Fe3+ broad hyperfine splitting (HFS) at room temperature dealing with slow relaxation effect of ferric ions. X-band EPR spectra exhibits resonance signals at g≈2.0, g≈4.3 and a shoulder in the region of g≈6.0. EPR spectra were simulated on the basis of rhombic spin-Hamiltonian with Zeeman and fine-structure terms. The nature of EPR absorption signals was interpreted as a combination of five types of Fe3+ complexes. Three of them were clustered ferric ions and two others were isolated paramagnetic ferric ions in distorted octahedral sites. The iron RedOx ratio (Fe2+/Fe3+) has been estimated from Mössbauer spectroscopy, while proportion of Fe3+ ions in adjacent sites (Fe3+ isolated)/Fe3+ clustered) has been obtained from Mössbauer spectra and simulated EPR spectra. [Copyright &y& Elsevier]

Polycrystalline Ba2Znx{\rm Co}2-{\rm x}{\rm Fe}12{\rm O}22 samples were prepared by solid state reaction method. The crystallographic structure and magnetic properties of the Zn-doped Y-type hexaferrite samples were investigated by X-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. The crystal structure was found to be hexagonal with space group of R-3/m. The lattice constants of the samples increased as Zn contents increase. From the temperature dependence of magnetization, measured from 50 to 700 K, the magnetic transition temperature (TS,TC) of Ba2Znx{\rm Co}2-{\rm x}{\rm Fe}12{\rm O}22 decreased with increasing Zn concentration. Mössbauer spectra of Ba2Znx{\rm Co}2-{\rm x}{\rm Fe}12{\rm O}22({\rm x}=0,1) were obtained at various temperature ranging from 4.2 to 300 K. Based on the observed spectra, the site occupancies in six interstitial sites of Co, Zn and Fe ions were calculated from the average of the relative sub-spectra absorption areas. Increasing Zn contents, the Debye temperature of the samples decreased. The isomer shift values of the samples at various temperatures were 0.1<\delta<0.45\ mm/s, relative to the Fe metal, which were consistent with the Fe^3+ valance state. [ABSTRACT FROM AUTHOR]

The nature of the interaction between iron oxyhydroxide compounds and natural organic matter (NOM) may take various forms and is still a matter of debate. It is an important field to understand, especially for water treatment applications and for the knowledge of iron transport in the environment. The nature of association reached between iron oligomeric species and NOM is here investigated using Mössbauer spectroscopy and electron energy-loss spectroscopy (EELS) at the Fe-L3 edge. Raw water NOM taken from Moselle River (France), natural humic substances extracted from the riverine suspended matter, and a synthesized humic-like substance, are coagulated with iron nitrate according to a jar-test procedure. The results from Mössbauer spectroscopy indicate that Fe is present in an octahedral coordination environment, which is consistent with prior X-ray absorption spectroscopy reported in the literature. The areas beneath the peaks (Fe L3 edge) and the peak shapes of EELS spectra differ according to the origin of the organic matter, suggesting that various types of Fe populations can be distinguished using the EELS technique. Combining the selectivity of both Mössbauer spectroscopy for identifying trace, poorly crystalline Fe solids, oxidation state and of EELS for being able to characterize the population of Fe based on L-edge spectra, appears promising for characterizing Fe in systems containing NOM. [ABSTRACT FROM AUTHOR]

Abstract: The reactions of FeX3 (X=Cl and Br) and pz∗H (pz∗H=pyrazole, or substituted pyrazole) in CH2Cl2 have led to three types of mononuclear complexes: mer-[FeX3(pz∗H)3], trans-[FeX2(pz∗H)4]− and trans-[FeX2(pz∗H)4]. The latter type, containing FeII-centers results from spontaneous reduction of the FeIII starting material. The X-ray crystal structures of eleven such complexes and the 57Fe-Mössbauer spectra of three of them are reported. [Copyright &y& Elsevier]

Fe/SiO and Rh-Fe/SiO catalysts with increasing Fe/Rh ratio have been prepared and characterized by TEM, XRD, oxygen adsorption and Mössbauer spectroscopy. It was confirmed that Fe/SiO catalysts cannot be reduced under hydrogen flow, to more than 50 % whatever the temperature in the 200-500 °C range and shown that the presence of even a small amount of Rh (Fe/Rh ≤2,000) promoted the reduction of iron up to 85-95 %. This promoting effect also took place with a Fe/SiO + Rh/SiO physical mixture (Fe/Rh ≤2,000). Therefore, the occurrence of a hydrogen spillover effect may be involved in the observed process. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: This laboratory study describes the abiotic mineralogical transformation of ferrihydrite (F), goethite (G) and hematite (H) into mixed FeII–FeIII green rust (GR). Stoichiometric quantities of ferric oxides were reacted with hydroxylated FeII species under static batch conditions at a final pH of ~6.3 for 2h. Mössbauer spectroscopy and transmission electron microscopy (TEM) was used to characterize initial and resulting transformation products. Results indicate that the order of reactivity to transform into GR is F>G>H. Complete transformation of F into GR was achieved while about half of G or H was transformed although G or H are known for their higher thermodynamic stability. As expected, the concentration of soluble iron at the end of the experiment followed the order H>G>F which is in agreement with the predictions of the FeII–FeIII mass balance diagram. The formation kinetics of GR is much higher than that observed for magnetite (Fe3O4) under similar experimental conditions. Therefore in the environment, when hydroxylated FeII species interact with ferric oxides, fougerite, the mineral counter part of GR, could be preferentially formed. [Copyright &y& Elsevier]

Mössbauer and x-ray diffraction spectroscopic analyses were carried out on ZnFe2O4 nanoferrite of average size 17 nm after γ-irradiation with three absorbed doses of 291 kGy, 582 kGy and 873 kGy using 60Co source. The obtained Mössbauer analysis data were unchanged before and after irradiation for the investigated sample. A broad paramagnetic doublet spectrum was observed which is refereeing to octahedral high spin Fe3+ in the B-site of the ZnFe2O4 structure. The x-ray powder diffraction analysis has revealed that there is slight shift in some of the diffracted lines of the characteristic XRD pattern due to irradiation which is attributed to change in the lattice parameter. The estimated net magnetic moment was decrease after irradiation due to redistribution of the cations occupying the tetrahedral and octahedral sites. These results are discussed in the light of γ-rays interaction with ferrite lattice. [ABSTRACT FROM AUTHOR]

Abstract: A new tetradentate bis benzimidaozlyl diamide ligand N,N′-Bis (benzimidazol-2-yl-methyl)-hexane-1,6-dicarboxamide (GBSA) has been synthesized and utilized to prepare new Fe(III) complexes with exogenous anionic ligand X=Cl− and NO3 −. Isomer shift values are in the range found for Iron in the +3 oxidation state while Quadrupole Splitting indicates large distortion from a six coordinate geometry, a finding supported by low temperature EPR work. The E 1/2 values are found to be quite cathodic indicating stability of the Iron (III) complexes. The oxidation of alcohols was investigated using [Fe(GBSA)Cl3] as the catalyst with TBHP as an alternate source of oxygen. The respective carbonyl products have been isolated and characterized by 1H NMR, electronic spectroscopy, mass and IR spectral studies. [Copyright &y& Elsevier]

Investigations based on Fe Mössbauer spectroscopy and powder X-ray diffraction report the existence of siderite in a manganese ore deposit in the city of Conselheiro Lafaiete, Minas Gerais, Brazil. Mössbauer parameters at 110 K indicated the isomorphous substitution of Fe in siderite structure by other cations such as Ca and Mg, resulting in the distortion of siderite structure. The proposed mechanism suggests the formation of siderite and it is consistent with the process of carbonate formation in reducing environments. [ABSTRACT FROM AUTHOR]

Abstract: Fe(III)-doped TiO2 based heterogeneous photocatalysts were prepared by the sol–gel technique (S samples) or flame hydrolysis (F samples). In photocatalytic phenol decomposition, the undoped F-sample performed much better, than the undoped S one. However, for the S samples, photocatalytic activity first increased with the increasing Fe(III) concentration, and then passed through a maximum, while Fe(III)-doping in F samples significantly decreased it, even at the smallest dopant level. Since the same dopant caused opposite photocatalytic effects in the two series, their structure was systematically compared to identify the underlying chemical and/or physical reasons. The photocatalysts were first characterized by AAS, DRS, XRD and TEM methods and it has been shown that the differences in the photocatalytic activity cannot be explained by the minor variations in the bulk structural properties of TiO2. Mössbauer and XP spectroscopic measurements performed on representative samples qualitatively proved that the local structure of Fe(III) is different in the two series. To quantify these effects, Fe-K edge X-ray absorption measurements were performed. From the pre-edge and XANES region it was learnt that Fe(III) was present in a distorted octahedral environment in both series, however, the extent of distortion is much more significant within the S than within the F one. Information obtained from the EXAFS region indicated that the structure of Fe2O3 was much more ordered in the F-series then in the S one and vacancies were more abundant in the S than in the F series. Moreover, the geometry around Fe(III) systematically varied within the S-series, which could explain, why photocatalytic activity passed through a maximum with the increasing Fe(III) concentration in these samples. [Copyright &y& Elsevier]

Aim of the study: To investigate the relation between the clinical effects and the quality of crude drugs, we focused on Tokishakuyakusan (TS), consisted of 6 crude drugs. Materials and methods: We prepared two kinds of TS containing either medicinal cultivar of Paeonia lactiflora (MTS) or ornamental one (OTS). Other components were the same. First, we assessed the clinical effects of two TS formulations by cross-over study among the anemia patients. Second, we investigated the chemical differences between them by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Mössbauer analysis. Results: The clinical effects of these formulations (3g/day for 8 weeks) were tested in the cross-over study consisted of 12 women patients who were diagnosed as having anemia (Hb≤11g/dl) and consented to participate to this study. Both TS formulations were effective for anemia symptoms as shown by the improvement of several hematological parameters, whereas their comprehensive effects were distinguishable by Genetic Algorithm Partial Least Squares (GA-PLS) analysis. There were no significant differences in organic ingredients and Fe content measured by ultra performance liquid chromatography (UPLC) and ICP-MS, respectively. Interestingly, Mössbauer spectra of Fe ion were remarkably different between two formulations. Fe ion in MTS was only one form, but that in OTS was at least two forms. Conclusions: This study suggested that clinical effects of TS formulation reflect the quality of Paeoniae Radix. [Copyright &y& Elsevier]

Abstract: Yeast cells deficient in the yeast frataxin homolog (Yfh1p) accumulate iron in their mitochondria. Whether this iron is toxic, however, remains unclear. We showed that large excesses of iron in the growth medium did not inhibit growth and did not decrease cell viability. Increasing the ratio of mitochondrial iron-to-Yfh1p by decreasing the steady-state level of Yfh1p to less than 100 molecules per cell had very few deleterious effects on cell physiology, even though the mitochondrial iron concentration greatly exceeded the iron-binding capacity of Yfh1p in these conditions. Mössbauer spectroscopy and FPLC analyses of whole mitochondria or of isolated mitochondrial matrices showed that the chemical and biochemical forms of the accumulated iron in mitochondria of mutant yeast strains (Δyfh1, Δggc1 and Δssq1) displayed a nearly identical distribution. This was also the case for Δggc1 cells, in which Yfh1p was overproduced. In these mitochondria, most of the iron was insoluble, and the ratio of soluble-to-insoluble iron did not change when the amount of Yfh1p was increased up to 4500molecules per cell. Our results do not privilege the hypothesis of Yfh1p being an iron storage protein in vivo. [Copyright &y& Elsevier]

Radioactive veins in shear zones of the El-Seboah granite in Egypt with anomalous concentrations of Nd, Ce, Zr, Y, Nb, Sm, Th and U were studied by petrographic microscopy, x-ray diffraction, 57Fe Mössbauer and wet chemical methods. The veins are composed essentially of quartz, aegirine-augite and minor K-feldspar ± α-iron oxide (hematite) ± γ-iron oxide hydroxide (goethite). They likely represent late-stage felsic melt that was quenched and devitrified at high temperature to yield crystals and crystallites, and then subjected to low temperature alteration during which most of the K feldspar transformed to kaolinite and opal. Mössbauer parameters of the samples indicate that the existing Fe-bearing minerals are primary, with appreciable ordering in the Fe sites. The bulk-sample iron (ΣFe) contents are extremely high (12.3-22.4%). The extent of oxidation of the Fe has been found to be 100% by Mössbauer spectroscopy and 95.36-99.69% by a chemical method. These conditions of Fe enrichment and strong oxidation suggest that the veins are extreme differentiates of granite magmas where high states of oxygen fugacity prevailed. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of [Fe3EuO2(O2CCCl3)8(H2O)(THF)3] or [Fe2CaO(O2CCCl3)6(THF)4] and [Fe3O(O2CCMe3)6(H2O)3]NO3 with 1,1′-ferrocenedicarboxylic acid (fcdcH2) yielded penta- and hepta-nuclear [Fe4O2(O2CCCl3)6(fcdc)(THF)2(H2O)2] and [Fe6O2(OH)2(O2CCMe3)10(fcdc)(H2O)2], respectively, which are the first X-ray structurally characterized clusters comprising Fe(III) and the ferrocenedicarboxylic organometallic ligand. Variable-temperature solid-state magnetic susceptibility measurements in the temperature range 1.8–300K were carried out, and for both complexes a predominantly antiferromagnetic exchange interaction between the metal centres was observed. Mössbauer investigations show the presence of different environments for the Fe(III) atoms and confirm that no electron-transfer from Fe(II) of the ferrocene unit to Fe(III) of the central core occurs. [Copyright &y& Elsevier]

Abstract: The new tetranuclear complexes [Fe3Ln(μ3-O)2(CCl3COO)8(H2O)(THF)3]·THF (Ln=CeIII (1), PrIII (2), NdIII (3)) and [Fe3Ln(μ3-O)2(CCl3COO)8(H2O)(THF)3]·THF·C7H16 (Ln=SmIII (4), EuIII (5), GdIII (6), TbIII (7), DyIII (8), HoIII (9), LuIII (10) and YIII (11)) have been prepared. All compounds were prepared by the reaction between [Fe2BaO(CCl3COO)6(THF)6] and the corresponding LnIII nitrate salt. The crystal structures of 1–4, 8 and 9 have been determined; these isostructural molecules have a non-planar {Fe3Ln(μ3-O)2} “butterfly” core. Magnetic susceptibility measurements show dominant intramolecular antiferromagnetic exchange interactions for all the complexes. 57Fe Mössbauer spectroscopy shows three different environments for the FeIII metal ions, all in their high-spin state S =5/2 (confirming that no electron transfer from CeIII to FeIII occurs in 1). At the time scale of the Mössbauer spectroscopy (about 10−7 s), evidence of magnetization blocking, i.e. slow relaxation of the magnetization, is observed below 3K for 7, which was confirmed by ac susceptibility measurements. [Copyright &y& Elsevier]

Abstract: Samples of LaNi5−x Fe x were prepared by arc melting and subsequent melt spinning procedure. Structural, magnetic and Mössbauer investigations were performed for physical characterization while the hydrogen storage properties were carefully analyzed. Detailed discussions concerning the sample''s quality, the site assignment, the effect of temperature and applied fields on hyperfine parameters and the related Debye temperatures were provided. [Copyright &y& Elsevier]

Samples of SnO2 doped with different amount of Fe (10–20%) and Sb (5–25%) were prepared by sol–gel method. Room temperature ferromagnetism was found to increase as a result of co-doping with Sb, as compared to SnO2 doped only with Fe. 57Fe Mössbauer spectra of almost all samples exhibited two paramagnetic doublets and a small subspectrum referring to magnetic relaxation at room temperature. Only the samples Sn0.65Fe0.2Sb0.15O2 − δ and Sn0.85Fe0.1Sb0.05O2 − δ with 4 h long annealing time showed well developed sextets and larger magnetic coercivity compared to that of the other samples. The sextet observed was considered to be due to precipitates like Sn doped α-Fe2O3. The results suggest that the origin of the magnetic interactions is enhanced by the presence of magnetic defects, which can interact with the iron ions by free carrier electrons. For the sample with precipitates, the grain boundary defects may play an important role of enhanced ferromagnetism. [ABSTRACT FROM AUTHOR]

There is a general lack of understanding of the hydrogen isotope fractionations between different experimental approaches both at higher and at lower temperatures of exchange. The complexity of bonding related with the hydroxyl ion in most hydrous minerals makes theoretical treatments rather difficult. Though some of the differences between experimental findings have recently been shown to be related to pressure effects that influence the hydrogen isotope fractionation properties of water, some other factors may also have significance. One of the major unknowns is the compositional control, especially the Fe-content and effects of variable Fe3+/Fe2+ ratios on hydrogen isotope fractionations between minerals and fluids (Suzuoki and Epstein, Geochim Cosmochim Acta 40:1229–1240, ; Chacko et al. ). We have studied a series of amphibole samples by Mössbauer spectroscopy, EPMA and TC-EA-IRMS to examine for possible correlations between D/H fractionation and Fe2+ to Fe3+ ratio/total iron content. Our measurements show that this correlation may exist for one particular origin of samples, but local conditions of mineral formation (most probably chemical composition and reactions accompanying the formation of minerals) may be more important in controlling the hydrogen isotope composition of minerals. [ABSTRACT FROM AUTHOR]

Abstract: Highly crystalline CoFe1.9RE0.1O4 ferrite nanoparticles, where RE=La, Ce, Nd, Sm, Eu, Gd, Tb, and Ho, have been synthesized by forced hydrolysis in polyol. X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), 57Fe Mössbauer spectrometry, Co K-edge X-ray absorption spectroscopy and magnetic measurements using a SQUID magnetometer were employed to investigate the effect of the substitution RE3+ ions for Fe3+ ones on the structure, the microstructure, the chemical homogeneity, and the magnetic properties of the cobalt ferrite system. All the produced particles are superparamagnetic at room temperature. Nevertheless, the substitution causes reduction of the blocking temperature which is mainly ascribed to partial cation exchange among the spinel-like sublattices of CoFe2O4 induced by the insertion of the relatively large RE3+ ions. The low-temperature saturation magnetization and coercivity appear to be greatly affected by the nature of RE3+ ions—maxima values were found for Gd3+ and Eu3+, respectively. [Copyright &y& Elsevier]