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Strong Goss texture ({110}〈001〈) was successfully developed by secondary recrystallization in Fe81Ga19 sheets without conventional application of inhibitor or surface energy effect as grain-oriented silicon steel. Goss grains cover 90% surface area of annealed sheet, and the magnetostriction coefficient reaches up to 262 ppm. The primary recrystallization microstructure and texture provide the prerequisites for nucleation and abnormal grain growth of secondary Goss grains. The dispersedly distributed Goss grains do not exhibit an evident advantage in grain size and number, and the normal grain growth of matrix grains can be inhibited by low-angle grain boundaries before onset of secondary recrystallization. The existence of low-angle grain boundaries is proposed to be an important factor for the occurrence of secondary recrystallization in binary Fe-Ga sheets based on grain boundary character distribution analysis. [ABSTRACT FROM AUTHOR]

Femtosecond mid-infrared pump-probe and two-dimensional mid-infrared spectroscopy have been used to investigate the dynamics of vibrational relaxation and vibrational spectral diffusion of the asymmetric N3-stretching vibration of pseudo-octahedral azidoiron(III) complexes, [L6-nFe(N3)n]+ with n = 1 or 2 and L being an auxiliary ligand of denticity 6-n, in acetonitrile at room temperature. Compared to the free azide anion in acetonitrile solution, the vibrational relaxation dynamics are considerably accelerated. Vibrational energy transfer to the solvent is accelerated by virtue of a resonance with an overtone transition of the solvent. Intramolecular vibrational redistribution is found to be accelerated by virtue of a coupling between the initial azide stretching vibration and the torsional modes involving the axial ligands. Vibrational spectral diffusion within the asymmetric N3-stretching resonance was found to be insensitive to solvent fluctuations because the axial azide ligands are only partially accessible to the solvent. The particular role of intramolecular structural relaxations of the complex for shaping the linear and nonlinear two-dimensional infrared spectra is discussed in terms of ultrafast symmetry-breaking torsional fluctuations and on the basis of density functional theory calculations. [ABSTRACT FROM AUTHOR]

Applications using FeRh for controllable exchange coupling of two magnetic layers with in-plane and out-of-plane anisotropies require ultrathin (~10 nm) films with pure antiferromagnetic (AF) FeRh α" phase at room temperature (RT). However, it is also well known that the antiferromagnetic-ferromagnetic (AF-FM) transition of FeRh is sensitive to composition and deteriorates at low thicknesses. Hence, in this work, we study the composition-dependent phase ordering of co-sputtered FeRh thin films at ultrathin thicknesses of ~10 nm. As the ultrathin films get richer in Rh, the appearance of α" phase is typically characterized magnetically by a sudden drop in RT moment, and structurally by a slight decrease in degree of B2 chemical ordering with a sharp decrease in c-axis lattice constant. These observations are consistent with the FeRh phase diagram where FeRh abruptly enters the AF α" phase once it becomes slightly disordered. Dependences of magnetic transition parameters on composition were also described. Moreover, higher sputtering powers possibly allow the formation of purer α" phase with less γ-face centered cubic phase impurities. Consequently, a composition optimized 10 nm film shows a relatively low residual moment (13.5 emu/cc), thus suggesting good AF phase formation. In addition, correlation of the magnetic transition parameters with the crystal structural parameters reveal that the maximum rate of AF-FM transition (Rmax,h) and the corresponding total change in magnetization (ΔMh) interestingly shows linear dependence on the c-axis lattice constant, but would depart from this linearity under certain conditions, i.e., when grain sizes were large, crystallinity was improved and Fe content was high. [ABSTRACT FROM AUTHOR]

Two new mononuclear iron(III) Schiff base complexes [Fe( L 1 ) 2 ]SCN (1) and [Fe( L 2 )( HL 3 )]ClO 4 (2) {where HL 1  = 1-((3-amino-2,2-dimethylpropylimino)methyl)naphthalen-2-ol, H 2 L 2  = N,N′-bis(3-ethoxysalicylidene)2,2-dimethyl-1,3-propanediamine and HL 3  = 2-((3-amino-2,2-dimethylpropylimino)methyl)-6-ethoxyphenol} have been synthesized and characterized by elemental and several spectral analyses. Single crystal X-ray structure determination confirmed their structures. Structural features have been examined in details that reveal the formation of interesting supramolecular networks generated through weak non-covalent interaction. Both complexes are able to show catechol oxidase mimicking activity and kinetics of the reactions are monitored spectrophotometrically. [ABSTRACT FROM AUTHOR]

An iron(II) pyridyl-benzohydrazonate-based complex decorated with long alkyl chains is reported as a rare spin-crossover compound displaying a wide thermal hysteresis spanning room temperature. On heating, this compound exhibits a spin transition between a LS ground state and an ordered HS-LS phase with symmetry breaking from monoclinic P21/n into orthorhombic P21212 space groups. During cooling, the compound first transits into a magnetically distinguishable HS-LS phase with monoclinic P21 symmetry before returning into the LS phase. Interconversion between the two distinct HS-LS phases is the result of subtle structural changes in the alkyl chains and produces a second minor thermal hysteresis that superposes to the large one. This unprecedented result shows that the combination of a conventional cooperative spin transition and ligand-driven magnetic changes can promote magnetic tristability at room temperature. [ABSTRACT FROM AUTHOR]

This study presents a novel strategy for remedying acidification and improving the removal efficiency of pollutants from digested effluent by using Zero-Valent Iron (iron scraps) in a sequencing batch reactor. Through this strategy, the pH increased from 5.7 (mixed liquid in the reactor without added ZVI) to 7.8 (reactors with added ZVI) because of Fe 0 oxidation and NO 3 − reduction. The removal efficiencies of COD increased from 11.5% to 77.5% because of oxidation of ferric ion and OH produced in chemical reactions of ZVI with oxygen and because of flocculation of iron ions. The removal efficiencies of total nitrogen rose from 1.83% to 93.3% probably because of autotrophic denitrification using electron donors produced by the corrosion of iron, as well as the favorable conditions for anammox due to iron ions. Total phosphorus increased from −25.8% to 77.1% because of the increase in pH and the precipitation with iron ions. [ABSTRACT FROM AUTHOR]

The influence of plasma environment on the atomic parameters associated with the K-vacancy states has been investigated theoretically for several iron ions. To do this, a time-averaged Debye-Hückel potential for both the electron-nucleus and electron-electron interactions has been considered in the framework of relativistic multiconfiguration Dirac-Fock computations. More particularly, the plasma screening effects on ionization potentials, K-thresholds, transition energies, and radiative rates have been estimated in the astrophysical context of accretion disks around black holes. In the present paper, we describe the behaviour of those atomic parameters for Ne-, Na-, Ar-, and K-like iron ions. [ABSTRACT FROM AUTHOR]

Synthesis of Ni and Zn substituted nano-greigite, Fe3S4, is achieved from single source diethyldithiocarbamato precursor compounds, producing particles typically 50-100 nm in diameter with plate-like pseudohexagonal morphologies. Up to 12 wt.% Ni is incorporated into the greigite structure, and there is evidence that Zn is also incorporated but Co is not substituted into the lattice. The Fe L3 X-ray absorption spectra for these materials have a narrow single peak at 707.7 eV and the resulting main X-ray magnetic circular dichroism (XMCD) has the same sign at 708.75 eV. All XMCD spectra also have a broad positive feature at 711 eV, a characteristic of covalent mixing. The greigite XMCD spectra contrast with the three clearly defined XMCD site specific peaks found in the ferrite spinel, magnetite. The Fe L2,3 X-ray absorption spectra and XMCD spectra of the greigite reflect and reveal the high conductivity of greigite and the very strong covalency of the Fe-S bonding. The electron hopping between Fe3+ and Fe2+ on octahedral sites results in an intermediate oxidation state of the Fe in the Oh site of Fe2.5+ producing an effective formula of [Fe3+↑]A-site[2Fe2.5+↓]B-siteS2-4]. The Ni L2,3 X-ray absorption spectra and XMCD reveal substitution on the Oh site with a strongly covalent character and an oxidation state

Iron complex [FeIII(N3)(MePy2tacn)](PF6)2 (1), containing a neutral triazacyclononane-based pentadentate ligand, and a terminally bound azide ligand has been prepared and spectroscopically and structurally characterized. Structural details, magnetic susceptibility data, and Mössbauer spectra demonstrate that 1 has a low-spin (S = 1/2) ferric center. X-ray diffraction analysis of 1 reveals remarkably short Fe-N (1.859 Å) and long FeN-N2 (1.246 Å) distances, while the FT-IR spectra show an unusually low N-N stretching frequency (2019 cm-1), suggesting that the FeN-N2 bond is particularly weak. Photolysis of 1 at 470 or 530 nm caused N2 elimination and generation of a nitrido species that on the basis of Mössbauer, magnetic susceptibility, EPR, and X-ray absorption in conjunction with density functional theory computational analyses is formulated as [FeV(N)(MePy2tacn)]2+ (2). Results indicate that 2 is a low-spin (S = 1/2) iron(V) species, which exhibits a short Fe-N distance (1.64 Å), as deduced from extended X-ray absorption fine structure analysis. Compound 2 is only stable at cryogenic (liquid N2) temperatures, and frozen solutions as well as solid samples decompose rapidly upon warming, producing N2. However, the high-valent compound could be generated in the gas phase, and its reactivity against olefins, sulfides, and substrates with weak C-H bonds studied. Compound 2 proved to be a powerful two-electron oxidant that can add the nitrido ligand to olefin and sulfide sites as well as oxidize cyclohexadiene substrates to benzene in a formal H2-transfer process. In summary, compound 2 constitutes the first case of an octahedral FeV(N) species prepared within a neutral ligand framework and adds to the few examples of FeV species that could be spectroscopically and chemically characterized. [ABSTRACT FROM AUTHOR]

With the aim to obtain iron tubular microstructures attractive for various applications, we have used a natural biogenic iron ochre as a raw material and explore various procedures and experimental conditions to achieve our goal. Our experiments included reduction, nitridation and characterization of microtubes derived from biogenic iron ochre. Various temperatures of reduction under streams of H/N or NH were tested. Our results show that the tubular structure is maintained after reduction of the natural material under H/N. In addition, ammonia was not produced under our experimental conditions, and as expected, hydrogen reduced the material. However, the treatment under NH reduces the material and allows the incorporation of nitrogen into the structure of the solid yielding iron nitride microtubes. Reduced and nitrided microstructures were successfully obtained from natural biogenic iron ochre. A temperature of 500 °C seems to be suitable to expose the calcined biogenic iron ochre under H/N for 4 h or under ammonia for 8 h to obtain reduced or nitrided microtubes, respectively. The stability of the tubular structure during reduction/reduction-nitridation is maintained under both treatments. Further interesting applications of this natural biomaterial could be envisaged. [ABSTRACT FROM AUTHOR]

The phase relations in the (Pr1−xSmx)2Fe14B system in a whole concentration range have been studied by means of X-ray powder diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The XRD patterns of the (Pr1−xSmx)2Fe14B samples have been refined by Rietveld method. These results reveal that all the alloys (Pr1−xSmx)2Fe14B are similar to the end member of the investigated system Pr2Fe14B with tetragonal structure (space group P42/mnm). The continuous solid solutions were formed in this system. The normalized lattice parameters and unit cell volumes of (Pr1−xSmx)2Fe14B solid solutions decrease linearly withxranging from 0 to 1.0. The DTA measurements show that the peritectic temperature of (Pr1−xSmx)2Fe14B increases with increasing Sm content and no metastable phases are detected. Based on the DTA data, SEM–EDS and XRD results, the vertical section of Pr2Fe14B–Sm2Fe14B in the Pr–Sm–Fe–B system has been constructed. [ABSTRACT FROM AUTHOR]

Samples of 0.9Pb(Fe1/2Nb1/2)O3-0.1PbTiO3 were mixed with ZnO at 0, 1, 2, and 3 wt.%, and were synthesised by mixed oxide through a two-step sintering method. Phase transition of the samples was analysed by using X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). The dielectric properties were determined by LCR meter at 1 kHz, 10 kHz, and 100 kHz. The results showed that the morphotropic phase boundary of 0.9PFN-0.1PT shifting to tetragonal phase and suppressed pyrochlore phase when ZnO was added into 0.9PFN-0.1PT. In addition, FTIR spectra peak showed zinc and oxygen bond bonding vibration at frequencies range 3,452 cm-1 and 3,792 cm-1 after level doping ZnO of 3 wt.%. The samples exhibited the maximum dielectric constant at temperature for 144°C. The dispersion of dielectric constantly decreased with increasing ZnO contents. The relaxor ferroelectric of 0.9PFN-0.1PT ceramic shifted to normal ferroelectric with increasing ZnO contents. [ABSTRACT FROM AUTHOR]

The Sm-Ni-Fe ternary system has been investigated at 773 K by means of powder x-ray diffraction, metallography and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The isothermal section consists of 16 single-phase regions, 29 two-phase regions and 14 three-phase regions. The influence of Fe-doping on the structure and the microwave absorption properties of the SmNi compound has been systematically studied. The homogeneity range in SmNiFe was determined as x = 16.67. The lattice parameters were found to gradually increase and the particle size become much finer with the increase of Fe concentration. All the samples exhibited good microwave absorption properties in the X-band (8-12 GHz). The highest reflection loss of the SmNiFe ( x = 0.0, 5.0, 10.0,15.0, 16.67) alloys are −10.12 dB, −10.39 dB, −16.44 dB, −20.69 dB, and −43.05 dB at 6.96 GHz, 7.92 GHz, 8.56 GHz, 10.04 GHz, and 11.08 GHz, respectively. The absorption peak shifted towards the higher frequency region with the increasing amount of Fe substitution. [ABSTRACT FROM AUTHOR]

Vibrational spectra are measured for Fe3 +(CH4) n (n = 1-3) and Fe4 +(CH4)4 in the C-H stretching region (2650-3100 cm-1) using photofragment spectroscopy, monitoring loss of CH4. All of the spectra are dominated by an intense peak at around 2800 cm-1 that is red-shifted by ~120 cm-1 from free methane. This peak is due to the symmetric C-H stretch of the η3 hydrogen-coordinated methane ligands. For clusters with three iron atoms, the peak becomes less red-shifted as the number of methane ligands increases. For clusters with one methane ligand per iron atom, the red shift increases in going from Fe2 +(CH4)2 (88 cm-1) to Fe3 +(CH4)3 (108 cm-1) to Fe4 +(CH4)4 (122 cm-1). This indicates increased covalency in the binding of methane to the larger iron clusters and parallels their increased reactivity. Density functional theory calculations, B3LYP, BPW91, and M11L, are used to identify possible structures and geometries and to predict the spectra. Results show that all three functionals tend to overestimate the methane binding energies. The M11L calculations provide the best match to the experimental spectra. [ABSTRACT FROM AUTHOR]

In this work, a new multifunctional nanoplatform (Fe3O4@mSiO2-FA-CuS-PEG nanocomposite) for magnetic resonance imaging (MRI) and targeted chemo-photothermal therapy, was firstly fabricated on the basis of magnetic mesoporous silica nanoparticles (Fe3O4@mSiO2), on which folic acid (FA) was grafted as the targeting reagent, CuS nanocrystals were attached as the photothermal agent, and polyethylene glycol (PEG) was coupled to improve biocompatibility. The characterization results demonstrated that the fabricated Fe3O4@mSiO2-FA-CuS-PEG nanocomposites not only showed strong magnetism and excellent MRI performance, but also had a high doxorubicin (DOX, an anticancer drug) loading capacity (22.1%). The loaded DOX can be sustainably released, which was apt to be controlled by pH adjustment and near infrared (NIR) laser irradiation. More importantly, targeted delivery of the DOX-loaded Fe3O4@mSiO2-FA-CuS-PEG nanocomposites could be accomplished in HeLa cells via the receptor-mediated endocytosis pathway, and this exhibited synergistic effect of chemotherapy and photothermal therapy against HeLa cells under irradiation with a 915 nm laser. Therefore, the fabricated multifunctional Fe3O4@mSiO2-FA-CuS-PEG nanocomposite has a great potential in image-guided therapy of cancers. [ABSTRACT FROM AUTHOR]

The phase behaviour and spin states of [Fe(NCS)2(dpq)2] (1; dpq = dipyrido[3,2-f:2′,3′-h]quinoxaline), [Fe(NCS)2(dppz)2] (2; dppz = dipyrido[3,2-a:2′3′-c]phenazine) and [Fe(NCS)2(dppn)2] (3; dppn = dipyrido[3,2-a:2′3′-c]benzophenazine) have been investigated. Solvent-free 1 and 2 are isostructural and low-spin in the crystalline state, in contrast to previously published 2·py (py = pyridine) which exhibits a hysteretic spin-crossover (SCO) transition near 140 K. The inactivity of 1 and 2 towards SCO may relate to their more crowded intermolecular lattice environment, particularly two very short intermolecular anion…π contacts involving the NCS− ligands. Two solvate phases of 1 are also described, including 1·2py which undergoes gradual SCO with T½ca. 188 K. Bulk samples of 2 and 3 are predominantly low-spin and isostructural with the crystals of 2 by powder diffraction, but bulk samples of 1 contain an extra phase that exhibits hysteretic SCO, but was not crystallographically characterised. Crystal structures of low-spin [Fe(dppz)3][ClO4]2 (4) and a solvate of [Fe(dppn)3][BF4]2 (5) are also described, which are the first homoleptic complexes of these ligands to be crystallographically characterised. [ABSTRACT FROM AUTHOR]

Iron gallates with iron in the oxidation states Fe2+ and Fe3+ were prepared and studied by Mössbauer spectroscopy, X-ray diffraction, and IR spectroscopy. FeIII 3,4,5-trihydroxybenzoate (gallate) Fe(C7O5H4) ·2H2O, whose structure was first determined by Wunderlich, was obtained by the reaction of gallic acid and metallic iron or by oxidation of the FeII gallate, which was obtained by the reaction of ferrous sulfate with 3,4,5-trihydroxybezoic acid (gallic acid) under anoxic conditions. Trials to reproduce the hydrothermal preparation method of Feller and Cheetham show that the result depends crucially on the free gas volume in the reaction vessel. If there is no free volume one obtains the same FeIII gallate as in the other preparation methods. With a large free volume another compound was found to form whose composition and structure could not be determined. It could be specified only by Mössbauer spectroscopy. FeIII gallate, the FeII gallate, and the new phase show magnetic ordering at liquid helium temperature. [ABSTRACT FROM AUTHOR]

A number of hydroxytriazenes have been used as analytical reagents for various transition metals. In the present paper spectrophotometric studies of 3-hydroxy-3-(4-chlorophenyl)-1-(4-acetylsulfonyl) phenyltriazene in the determination of Fe(III) is being reported. The complex absorbs at 403 nm and form 1:2 complex with Fe(III) in the pH range of 1.4-2.0. [ABSTRACT FROM AUTHOR]

The Raman spectra of pseudolaueite, strunzite, ferrostrunzite and ferristrunzite have been obtained at 298 K using Raman microscopy. These spectra are compared with their infrared spectra. The vibrational spectra of the four minerals are different, in line with differences in crystal structure and composition. Some similarity in the Raman spectra of the hydroxyl-stretching region exists, particularly but characteristic differences in the OH deformation regions are observed. Differences are also observed in the phosphate stretching and deformation regions. Graphical Abstract: This paper offers new knowledge and understanding of the mineral pseudolaueite of formula MnFe(PO)(OH)·8HO,a hydrated hydroxy phosphate of ferric iron and manganese.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Diamagnetic iron chloro compounds [(PPh2NPh2)FeCp*Cl] [1Cl] and [(PCy2NPh2)FeCp*Cl] [2Cl] and the corresponding hydrido complexes [(PPh2NPh2)FeCp*H] [1H] and [(PCy2NPh2)FeCp*H] [2H] have been synthesized and characterized by NMR spectroscopy, electrochemical studies, electronic absorption, and 57Fe Mössbauer spectroscopy (PPh2NPh2 = 1,3,5,7-tetraphenyl-1,5-diphospha-3,7-diazacyclooctane, PCy2NPh2 = 1,5-dicyclohexyl-3,7-diphenyl-1,5-diphospha-3,7-diazacyclooctane, Cp* = pentamethylcyclopentadienyl). Molecular structures of [2Cl], [1H], and [2H], derived from single-crystal X-ray diffraction, revealed that these compounds have a typical piano-stool geometry. The results show that the electronic properties of the hydrido complexes are strongly influenced by the substituents at the phosphorus donor atoms of the PR2NPh2 ligand, whereas those of the chloro complexes are less affected. These results illustrate that the hydride is a strong-field ligand, as compared to chloride, and thus leads to a significant degree of covalent character of the iron hydride bonds. This is important in the context of possible catalytic intermediates of iron hydrido species, as proposed for the catalytic cycle of [FeFe] hydrogenases and other synthetic catalysts. Both hydrido compounds [1H] and [2H] show enhanced catalytic currents in cyclic voltammetry upon addition of the strong acid trifluoromethanesulfonimide [NHTf2] (pKaMeCN = 1.0). In contrast to the related complex [(PtBuNBn)²FeCpC6F5H], which was reported by Liu et al. (Nat. Chem. 2013, 5, 228-233) to be an electrocatalyst for hydrogen splitting, the here presented hydride complexes [1H] and [2H] show the tendency for electrocatalytic hydrogen production. Hence, the catalytic direction of this class of monoiron compounds can be reversed by specific ligand modifications. [ABSTRACT FROM AUTHOR]

Iron(iii) diamine sarcophagine (DiAmsar) has attracted great attention in biological and medical applications. In particular, for any potential in vivo application, knowledge about the interaction of iron(iii) DiAmsar with serum albumin is crucial. As a step towards the elucidation of the fate of iron(iii) DiAmsar introduced into an organism, first, iron(iii) DiAmsar was synthesised and characterised. In the next step, interactions of iron(iii) DiAmsar with human serum albumin (HSA) and bovine serum albumin (BSA) were systematically investigated by various spectroscopic methods (Fourier-transform infrared, UV-visible, fluorescence) and cyclic voltammetry and molecular docking techniques under simulated physiological conditions. The fluorescence intensities of HSA and BSA decreased remarkably with increasing concentration of iron(iii) DiAmsar. The Stern-Volmer quenching constant KSV at different temperatures and corresponding thermodynamic parameters such as ΔHo, ΔGo, and ΔSo were calculated. The binding distance of iron(iii) DiAmsar with HSA and BSA was also determined using the theory of fluorescence energy transfer. Further, the conformational changes of HSA and BSA induced by iron(iii) DiAmsar were analysed by means of Fourier-transform (FT)-IR. In addition, molecular docking was performed to explore the possible binding sites and the microenvironment conditions around the bound iron(iii) DiAmsar. [ABSTRACT FROM AUTHOR]

By implementing transmission electron microscope (TEM) image processing, effects of a reducing agent and surfactant concentrations on the reactions between Pt(acac) and alternative Fe( β-diketonate) , i.e., Fe(tmhd) and Fe(hfac) , can be determined. The oleic acid and oleylamine of 0.5 mmol give rise to the FePt-based nanoparticles as small as 3 nm. Larger particles up to 5 nm in diameter with better self-assembled patterns are obtained by increasing each surfactant to 5 mmol. With such excessive surfactants in the synthesis, the reducing agent such as 1,2-hexadecanediol may not be required since it does not significantly influence the particle size and assembly. Moreover, it accelerates the reduction of Pt(acac) , resulting in larger size distribution. This work demonstrates that image processing allows the size analysis from statistically sufficient number of nanoparticles. This intensity-based analysis is, however, susceptible to the error arising from a low contrast between the nanoparticle and the background. The magnification of TEM images should therefore be optimized to minimize systematic errors. [ABSTRACT FROM AUTHOR]

FeIII-hypohalite complexes have been implicated in a wide range of important enzyme-catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post-translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme FeIII-hypohalite intermediates of possible relevance to iron halogenases. We show that FeIII-OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo-ESIMS. DFT methods rationalize the pathways to the formation of the FeIII-OCl, and ultimately FeIVO, species and provide indirect evidence for a short-lived FeII-OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases. [ABSTRACT FROM AUTHOR]

The crystal structure of a novel Mg2Fe2O5 oxide synthetized at 15 GPa and 1550 °C has been determined by means of single-crystal X-ray diffraction. This compound is isostructural with Fe4O5 and can be considered as the other end-member of a solid solution between these two oxides involving the substitution of Fe2+ for Mg. The resulting unit-cell lattice parameters a = 2.8889(4), b = 9.7282(4), and c = 12.5523(7) Å are smaller than those of Fe4O5. Mg and Fe3+ cations are found to be disordered among the three crystallographic sites of the Mg2Fe2O5 structure, although preference of Mg for the trigonal prism coordination (M3) is observed. Substitution of Mg into the Fe4O5 structure reduces the octahedral distortion of both the M1 and M2 sites. Like Mg, Cr has recently been found to substitute into Fe4O5, so that Fe3+/ΣFe can vary from 0 to 1.0 in the Mg-Cr-Fe oxides system. Substitution of both Mg and Cr in Fe4O5 also makes this phase more relevant for bulk compositions expected in the Earth's transition zone and deep upper mantle. M4O5 phases having the CaFe3O5-type structure, therefore, need to be considered as a new addition to the phase relations of several simple oxide systems at pressure and temperature conditions at which the spinel-structured phases become unstable. [ABSTRACT FROM AUTHOR]

A series of four isostructural Fe2II complexes, [(TPyA)2Fe2(

Metal complexes incorporating the tris(3,5-diphenylpyrazolyl)borate ligand (TpPh2) and ortho-dihalophenolates were synthesized and characterized in order to explore metal-halogen secondary bonding in biorelevant model complexes. The complexes TpPh2ML were synthesized and structurally characterized, where M was Fe(II), Co(II), or Ni(II) and L was either 2,6-dichloro- or 2,6-dibromophenolate. All six complexes exhibited metal-halogen secondary bonds in the solid state, with distances ranging from 2.56 Å for the TpPh2Ni(2,6-dichlorophenolate) complex to 2.88 Å for the TpPh2Fe(2,6-dibromophenolate) complex. Variable temperature NMR spectra of the TpPh2Co(2,6-dichlorophenolate) and TpPh2Ni(2,6-dichlorophenolate) complexes showed that rotation of the phenolate, which requires loss of the secondary bond, has an activation barrier of ~30 and ~37 kJ/mol, respectively. Density functional theory calculations support the presence of a barrier for disruption of the metal-halogen interaction during rotation of the phenolate. On the other hand, calculations using the spectroscopically calibrated angular overlap method suggest essentially no contribution of the halogen to the ligand-field splitting. Overall, these results provide the first quantitative measure of the strength of a metal-halogen secondary bond and demonstrate that it is a weak noncovalent interaction comparable in strength to a hydrogen bond. These results provide insight into the origin of the specificity of the enzyme 2,6-dichlorohydroquinone 1,2-dioxygenase (PcpA), which is specific for ortho-dihalohydroquinone substrates and phenol inhibitors. [ABSTRACT FROM AUTHOR]

We demonstrate giant magnetoresistance in Fe/MoS2/Fe junctions by means of ab initio transport calculations. We show that junctions incorporating either a monolayer or a bilayer of MoS2 are metallic and that Fe acts as an efficient spin injector into MoS2 with an efficiency of about 45%. This is the result of the strong coupling between the Fe and S atoms at the interface. For junctions of greater thickness, a maximum magnetoresistance of ∼300% is obtained, which remains robust with the applied bias as long as transport is in the tunneling limit. A general recipe for improving the magnetoresistance in spin valves incorporating layered transition metal dichalcogenides is proposed. [ABSTRACT FROM AUTHOR]

Aims. We have studied the structure and dynamics of the upper photosphere and lower chromosphere of the quiet Sun. Methods. We analyzed a sequence of scans of slit spectra of the Ca II H line at 396.8 nm, with a spectral resolution of 850 000, and a spatial resolution of about one arcsec, taken in the quiet Sun at disk center, with a duration of about 55 min and an area coverage of 185" x 3.5" . We used statistical methods to characterize size, lifetime, and dynamics of emission features of the Fe II line at 396.94 nm. Results. We have identified about 780 distinct features where the Fe II line shows emission stronger than 3% above the local continuum. Their lifetime is on the order of one minute, and the spatial extent is about or less than 2". On average, Fe II emission features show a significant redshift of 1.3 km s-1, with respect to the position of the absorption line. The redshift of the Fe II emission is absent close to the solar limb. The Fe II emission is coupled with a strongly enhanced intensity level of the Ca II wings. A time line analysis shows that other photospheric lines show significant redshift one minute before, and a blueshift after, the occurrence of an emission event. A redshift of the Ca II H line core precedes the redshift of the Fe II line by about 30 s. The occurrence of the H2v emissions is strongly reduced before and significantly increased after the Fe II emission events. Conclusions. The temporal behavior of the Fe II emission line and both the Ca II H line core and H2v emission suggest a connection between Fe II emission and chromospheric activity. The presence of a significant redshift during the Fe II emissions and the absence of this redshift near the limb suggest that the observed redshift is indeed caused by a downflow in the line-forming region. From our result concerning the intensity fluctuations in the core of the Fe II line, and from the magnitude of the downflow velocities we conclude that the Fe II emissions at 396.94 nm occur in the photosphere. [ABSTRACT FROM AUTHOR]

Abstract: A heptanuclear FeIII 7 cluster is reported, prepared from the reaction of [Fe3O(O2CPh)6(H2O)3]+ and a combination of aliphatic aminoalcohol ligands, namely apH (3-amino-1-propanol) and hmpipH (2-hydroxymethyl piperidine). The (apH2)[Fe7O3(OH)3(hmpip)6(O2CPh)7] complex possesses a metal core resembling a metal-centered non-planar six-pointed star. Thermogravimetric analysis was used to monitor the thermal stability of 1, and shows stepwise loss of mass for this complex upon heating, while Mössbauer spectroscopy was used to evaluate the chemical environment of the Fe ions. The latter confirmed the existence of only high-spin FeIII ions in the cluster, as also suggested by X-ray crystallography. Dc and ac magnetic susceptibilities were measured on microcrystalline samples of 1, and the ground state for this cluster was found to be S =21/2, with low lying excited states. Attempts to rationalize the observed spin using two different magnetostructural correlation relationships, previously derived for oxide-bridged FeIII dimers, suggested the presence of spin frustrated pathways along the peripheral hexagon, which in turn produce a high-spin ground state. The observed S =21/2 was finally rationalized using the results of this magnetostructural analysis, and assuming a combination of S i =5/2 and intermediate S i =3/2 spin projections. This Fe7 cluster is the third reported example of a heptanuclear Fe cluster with this topology, featuring a tetrahedral Fe ion at the center, and joins a small family of Fe clusters based on the aliphatic ligands apH and hmpipH. [Copyright &y& Elsevier]

The reactions of FeCl3 with benzotriazole (btaH), 1-methylbenzotriazole (Mebta), 5,6-dimethylbenzotriazole (5,6Me2btaH) and 5-chlorobenzotriazole (5ClbtaH) were studied in non-polar solvents. The new solid complexes [FeCl3(btaH)2] (1), [FeCl3(Mebta)2] (2), [FeCl3(5,6Me2btaH)2] (3) and [FeCl3(5ClbtaH)2]·2(5ClbtaH) (4) have been isolated. The structures of the complexes have been determined by single-crystal, X-ray crystallography. The structures of 1–4 consist of mononuclear, high-spin 5-coordinate molecules; in addition, the crystal structure of 4 contains two lattice 5ClbtaH molecules per [FeCl3(5ClbtaH)2] unit. The coordinated benzotriazole molecules behave as monodentate ligands with their ligated atom being the nitrogen of the position 3 of the azole ring. The geometry at iron(III) is trigonal bipyramidal with the chlorido ligands occupying the equatorial sites. The crystal structures of the complexes are stabilized by stacking interactions and H bonds (for 1, 3 and 4 only). The new complexes were characterized by elemental analyses, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, solid-state electronic UV/VIS/near-IR, 57Fe-Mössbauer, EPR only for complex 4) methods. All data are discussed in terms of the nature of bonding and the known structures. Complexes 1, 2 and 4 have been tested as homogeneous (MeCN) oxidation catalysts in the presence of the “green” H2O2 oxidant; they display moderate to high catalytic activity in the oxidation of several alkenes, cyclohexane and n-hexane, which is described in detail. [ABSTRACT FROM AUTHOR]

Nanostructures are considered as chemical systems of high potential owing to their unusual properties at the interface of those of molecular species and bulk metals. Consequently, they are promising candidates for application in different domains such as catalysis, magnetism, medicine, opto-electronics or sensors. The control of the characteristics of nanostructures is a fundamental prerequisite if one envisages exploring their physical or chemical properties since they vary dramatically with size, shape and surface state. Thus, the development of efficient methods leading to reproducible nanostructures is presently one of the main objectives in the nanochemistry community. Although organometallic chemistry has been early involved, it arises only marginally in the field. Nevertheless, the concepts and techniques of organometallic chemistry appear to be well-adapted for the growth of well-controlled nanostructures. This will be discussed through recent advances in the synthesis of metal and metal oxide nanoparticles in terms of size dispersion, chemical composition, surface state, shape or organization, pointing out the role of ligands. Moreover their characterization at a molecular level and the development of their chemical/physical properties towards applications will be described. This review reflects more than 20 years of efforts of our team to achieve these goals. [ABSTRACT FROM AUTHOR]

Alkoxy carbene complexes incorporating the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3)] were prepared in good yields from either the corresponding acyl complexes or methoxymethyl complex of the auxiliary. A range of nucleophilic addition reactions to these alkoxy carbene complexes showed moderate to high diastereoselectivities and the reactive conformations of the carbene complexes under these conditions are discussed. [ABSTRACT FROM AUTHOR]

Alkoxy carbene complexes incorporating the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3)] were prepared in good yields from either the corresponding acyl complexes or methoxymethyl complex of the auxiliary. A range of nucleophilic addition reactions to these alkoxy carbene complexes showed moderate to high diastereoselectivities and the reactive conformations of the carbene complexes under these conditions are discussed. [ABSTRACT FROM AUTHOR]

Atomic-resonance absorption spectroscopy is used to study the production and loss of iron atoms under dissociation of the Fe(CO) vapor in a quartz reactor that is induced by the pulses of the KrF excimer laser. Iron atoms populate the ground state owing to the quenching of the excited states generated in the course of the laser photolysis and are detected using the resonance absorption at a wavelength of 385.99 nm. The effective quenching rates are in good agreement with the known rates of the quenching of metastable iron atoms by the Fe(CO) molecules. It is demonstrated that a loss of iron atoms is related to the recombination with dimer and trimer formation and the secondary atomic reactions with the Fe(CO), CO, and FeCO molecules. The rates of the main elementary reactions responsible for the loss of iron atoms are determined using the comparison of the experimental results and kinetic simulation data. [ABSTRACT FROM AUTHOR]

A mixed amine pyridine polydentate FeII complex was covalently tethered in hexagonal mesoporous silica of the MCM-41 type. Metal site isolation was generated using adsorbed tetramethylammonium cations acting as a patterned silanol protecting mask and trimethylsilylazane as a capping agent. Then, the amine/pyridine ligand bearing a tethering triethoxysilane group was either grafted to such a pretreated silica surface prior to or after complexation to FeII. These two synthetic routes, denoted as two-step and one-step, respectively, were also applied to fumed silica for comparison, except that the silanol groups were capped after tethering the metal unit. The coordination of the targeted complex was monitored using UV-visible spectrophotometry and, according to XPS, the best control was achieved inside the channels of the mesoporous silica for the two-step route. For the solid prepared according to the one-step route, tethering of the complex occurred mainly at the entrance of the channel. [ABSTRACT FROM AUTHOR]

This work establishes the ability of valence-to-core X-ray emission spectroscopy (XES) to serve as a direct probe of N2 bond activation. A systematic series of iron-N2 complexes has been experimentally investigated and the energy of a valence-to-core XES peak was correlated with N–N bond length and stretching frequency. Computations demonstrate that, in a simple one-electron picture, this peak arises from the N2 2s2s σ* orbital, which becomes less antibonding as the N–N bond is weakened and broken. Changes as small as 0.02 Å in the N–N bond length may be distinguished using this approach. The results thus establish valence-to-core XES as an effective probe of small molecule activation, which should have broad applicability in transition-metal mediated catalysis. [ABSTRACT FROM AUTHOR]

Surface properties of Co-doped BaFe2As2 epitaxial superconducting thin films were inspected by X-ray photoelectron spectroscopy, scanning spreading resistance microscopy (SSRM), and point contact spectroscopy (PCS). It has been shown that surface of Fe-based superconductors degrades rapidly if being exposed to air, what results in suppression of gap-like structure on PCS spectra. Moreover, SSRM measurements revealed inhomogeneous surface conductivity, what is consistent with strong dependence of PCS spectra on contact position. Presented results suggest that fresh surface and small probing area should be assured for surface sensitive measurements like PCS to obtain intrinsic properties of Fe-based superconductors. [ABSTRACT FROM AUTHOR]

Abstract: An oxo-centred, carboxylate bridged trinuclear iron(III) complex [Fe3(μ3-O)(O2CCH2Cl)6(H2O)3]ClO4·9H2O (1·9H2O) has been synthesized and characterized on the basis of X-ray crystallography, elemental analysis, cyclic voltammetric, UV–vis and IR spectroscopic techniques. Molecular structure has been established by X-ray diffraction analysis and reveals that the complex 1·9H2O crystallizes in the rhombohedral space group R 3 with a =18.0070(6)Å, b =18.0070(6)Å, c =9.7962(5)Å, α = β =90.00° and γ =120.00°. In the highly symmetric trinuclear structure, three iron(III) atoms occupy vertices of equilateral triangle and exhibits a quasi-reversible one-electron reduction at E ½ =+0.337V vs Ag/AgCl (ΔEp =0.079V) due to the [Fe3(μ3-O)(O2CCH2Cl)6(H2O)3]+/[Fe3(μ3-O)(O2CCH2Cl)6(H2O)3] couple. In addition, ascending difference between cathodic and anodic peak potentials (ΔEp ) with the increasing scan rate confirmed the reduction wave to be quasi-reversible. [Copyright &y& Elsevier]

The compounds of this study have yielded to complementary structural, spectroscopic (Mössbauer, EPR/ ENDOR, IR), and computational probes that illustrate the fine control of electronic and steric features that are involved in the two structural forms of (μ-SRS)[Fe(CO)2PMe3]20,+ complexes. The installation of bridgehead bulk in the -SCH2CR2CH2S- dithiolate (R = Me, Et) model complexes produces 6-membered FeS2C3 cyclohexane-type rings that produce substantial distortions in FeIFeI precursors. Both the innocent (Fc+) and the noninnocent or incipient (NO+/CO exchange) oxidations result in complexes with inequivalent iron centers in contrast to the FeIFeI derivatives. In the FeIIFeI complexes of S = 1/2, there is complete inversion of one square pyramid relative to the other with strong super hyperfine coupling to one PMe3 and weak SHFC to the other. Remarkably, diamagnetic complexes deriving from isoelectronic replacement of CO by NO+, {(μ-SRS)[Fe(CO)2PMe3] [Fe(CO)(NO)- PMe3]+}, are also rotated and exist in only one isomeric form with the -SCH2CR2CH2S- dithiolates, in contrast to R = H (Olsen, M. T.; Bruschi, M.; De Gioia, L.; Rauchfuss, T. B.; Wilson, S. RJ. Am. Cheni. Soc. 2008, 130, 12021-12030). The results and redox levels determined from the extensive spectroscopic analyses have been corroborated by gas-phase DFT calculations, with the primary spin density either localized on the rotated iron in the case of the S = 1/2 compound, or delocalized over the {Fe(NO)} unit in the S = 0 complex. In the latter case, the nitrosyl has effectively shifted electron density from the FeIFeI bond, repositioning it onto the spin coupled Fe-N-O unit such that steric repulsion is sufficient to induce the rotated structure in the FeII-{FeI(•NO)}8 derivatives. [ABSTRACT FROM AUTHOR]

Structured diffuse-scattering intensities, whether of compositional or of pure displacive origin, static or dynamic, contain important information about the symmetry of the individual compositional and/or displacive modes responsible for the observed intensities. However, the interpretation of the experimental data is very often impeded by the lack of a symmetry-based approach to the analysis of the structured diffuse-scattering distributions. Recently, we have demonstrated the existence of systematic phonon selection rules for diffuse scattering that depend on the symmetries of the mode and the scattering vector, and not on the specific structure. Here, we show that such symmetry analysis can be successfully extended and also applied to structure-dependent diffuse scattering associated with `disordered' materials: the combination of theoretically determined, diffuse-scattering extinction conditions with the concept of non-characteristic orbits proves to be very useful in the interpretation of the observed diffuse-scattering extinctions. The utility of this approach is illustrated by the analysis of diffuse-scattering data from ThAsSe, FeOF and FeF2. The essential part of the associated calculations are performed by the computer programs NEUTRON (systematic phonon extinction rules in inelastic scattering) and NONCHAR (non-characteristic orbits of space groups) that are available on the Bilbao crystallographic server (). [ABSTRACT FROM AUTHOR]

The relationship between Compton scattered photon counts per unit mass and the content of a component in a binary powder mixture is deduced based on the Compton scattering theory. This relationship can be regarded linear after some approximations. The scattered photon counts per unit mass increases faster with the content when the difference of the atomic numbers of the two components in the binary powder mixture is larger. The relationship was verified with Compton scattering experiments on a series of Ni-Cu and Fe-C binary powder mixtures. The method of using this linear dependene of scattered photon counts on the content of a binary powder mixture to ascertain the component content in a binary mixture was introduced. [ABSTRACT FROM AUTHOR]

Iron, an important microelement essential to the functioning of the body, plays a special role in the process of respiration. There are more and more new products available on the pharmaceutical market. Some of them were the subject of previous studies, especially by using the Mossbauer spectroscopy. One of the latest is Biofer. For the present tests three tablets from three different production series of Biofer were used for examination of elemental composition using the X-ray fluorescence and energy dispersive X-ray spectroscopy methods. Information about oxidation of iron contained in the tablets was obtained with by means of the Mossbauer spectroscopy. [ABSTRACT FROM AUTHOR]

Background: The percentage of hypochromic red cells (% Hypo-He) is now available on the Sysmex analyzer XE 5000 (Sysmex Corporation, Kobe, Japan). In this study the reliability of % Hypo-He in the assessment of iron status in the presence of inflammation is investigated. Methods: Ninety healthy subjects, 91 patients with iron deficiency anemia (IDA) previous to therapy, 65 patients with chronic kidney disease (CKD), 57 patients with anemia of chronic diseases (ACD) and 28 patients with storage iron deficiency (ACD/IDA) receiving therapy were analyzed. Pearson's correlation, Independent samples t-test, receiver operating characteristic (ROC) curve analysis and Cohen's k index were applied. Results: % Hypo-He values inversely correlated with the blood hemoglobin (Hb) (r=-0.78) and Hb content (MHC, r=-0.75). In patients with IDA and ACD/IDA the values obtained for % Hypo-He showed no statistical difference (p=0.5037). ROC analysis results for % Hypo-He in the detection of iron deficiency defined by a serum transferrin receptor (sTfR) >21 nmol/L. The area under the curve is 0.929; cut-off 3.6%, sensitivity 91.5% and specificity 80.9%. Using the threshold 3.6% the k index obtained in comparison to sTfR was 0.64. Conclusions: % Hypo-He is a reliable parameter for the detection of iron deficiency in patients with anemia in the presence of inflammation. [ABSTRACT FROM AUTHOR]

A response is presented from the authors of the article "Direct Observation of Tetrahedrally Coordinated Fe(III) in Ferrihydrite" from volume 46, 2012 of “Environmental Science and Technology” to comments within the issue by R. K. Hocking and colleagues on the application of linear combination fitting to the L-edge absorption spectra of iron in ferrihydrite. Topics include the effectiveness of L-edge absorption spectroscopy in the analysis of nanomaterials, nuclear charge and covalency, and the impact of various ligand symmetry and strengths.

The article discusses the report "Direct Observation of Tetrahedrally Coordinated Fe(III) in Ferrihydrite," by D. Peak and T. Z. Regier from volume 46, 2012 of “Environmental Science and Technology.” The authors dispute several conclusions from the article regarding the use of linear combinations to interpret iron (Fe) L-Edge X-ray absorption spectroscopy (XAS) of ferrihydrite. Topics include the TT-Multiplex simulation code, the effects of energy shift and intensity, and bonding in iron compounds.

Low-energy electron excitation spectra were measured on a single crystal of a typical iron-based superconductor PrFeAsO0.7 using resonant inelastic x-ray scattering (RIXS) at the Fe-L3 edge. Characteristic RIXS features are clearly observed around 0.5, 1-1.5, and 2-3 eV energy losses. These excitations are analyzed microscopically with theoretical calculations using a 22-orbital model derived from first-principles electronic structure calculation. Based on the agreement with the experiment, the RIXS features are assigned to Fe-d orbital excitations which, at low energies, are accompanied by spin flipping and dominated by Fe dyz and dxz orbital characters. Furthermore, our calculations suggest dispersive momentum dependence of the RIXS excitations below 0.5 eV, and predict remarkable splitting and merging of the lower-energy excitations in momentum space. Those excitations, which were not observed in the present experiment, highlight the potential of RIXS with an improved energy resolution to unravel new details of the electronic structure of the iron-based superconductors. [ABSTRACT FROM AUTHOR]