Mössbauer

The ferric uptake regulator (Fur) is a global transcription factor that regulates intracellular iron homeostasis in bacteria. The current hypothesis states that when the intracellular "free" iron concentration is elevated, Fur binds ferrous iron and the iron-bound Fur represses the genes encoding for iron uptake systems and stimulates the genes encoding for iron storage proteins. However, the "iron-bound" Fur has never been isolated from any bacteria. Here we report that the Escherichia coli Fur has a bright red color when expressed in E...

In this work, we report a new octanuclear cluster based on FeIII and the ligand 1 H -imidazole-4,5-dicarboxylic acid, [Et3 NH]12 [Fe8 (IDC)12 ]·10DMF·13H2 O ( 1 ), with a metal core containing eight FeIII connected by only one type of organic ligand. A peak at 573 m / z in the mass spectra of the compound suggests the adduct species {[Fe8 (IDC)12 ]+8H}4- . By X-ray photoelectron spectroscopy, the oxidation state of the iron cation was confirmed to be 3+, also identifying the presence of a quaternary nitrogen species, which act as a countercation of the anionic metal core [Fe8 (IDC)12 ]12- ...

A polycrystalline sample of Sr2 ScFeAsO3 was studied by 57 Fe Mössbauer spectroscopy down to 1.7 K. In contrast to the earlier Mössbauer data, the obtained in this work results indicate that Sr2 ScFeAsO3 is in paramagnetic state down to 10 K, while the spectra recorded at 4.6 K and 1.7 K show a weak magnetic order of Fe moments in the Fe2 As2 layers. Temperature dependences of isomer shift and quadrupole splitting/shift are compared with specific heat and electrical resistivity data from earlier investigations revealing different local Debye temperatures for the Fe2 As2 and perovskite-related Sr2 ScO3 layers...

The aim of this work consists in the use of cashew gum (Anacardium occidentale), a naturally occurring tropical specie from the Brazilian northeastern coast, for the synthesis of CoFe2 O4 (CF) and NiFe2 O4 (NF) nanoparticles. The structural, morphological and vibrational properties of nanoparticles were characterized by analytical and spectroscopic techniques such as X-ray diffraction (XRD), FTIR, Raman spectroscopy, TEM, SAED and TG. Magnetic properties were investigated through Mössbauer spectroscopy and DC magnetometry...

Ultrawideline 35 Cl solid-state nuclear magnetic resonance (SSNMR) spectra of a series of 12 tin chlorides were recorded. The magnitude of the 35 Cl quadrupolar coupling constant ( C Q ) was shown to consistently indicate the chemical state (oxidation number) of the bound Sn center. The chemical state of the Sn center was independently verified by tin Mössbauer spectroscopy. C Q (35 Cl) values of >30 MHz correspond to Sn(IV), while C Q (35 Cl) readings of <30 MHz indicate that Sn(II) is present. Tin-119 SSNMR experiments would seem to be the most direct and effective route to interrogating tin in these systems, yet we show that ambiguous results can emerge from this method, which may lead to an incorrect interpretation of the Sn oxidation number...

A one-dimensional (1D) chain compound <mml:math xmlns:mml="https://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mo>[</mml:mo> <mml:msub> <mml:mi>Fe(en)</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:mo>]</mml:mo> </mml:mrow> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>FeSe</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mo>)</mml:mo> </mml:mrow> <mml:mn>4</mml:mn> </mml:msub> <mml:msub> <mml:mi>Cl</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> ( en = ethylenediamine), featuring tetrahedral FeSe2 chains separated by [Fe(en)3 ]2+ cations and Cl- anions, has been synthesized by a low temperature solvothermal method using simple starting materials...

Iron and manganese are ubiquitous in the natural environment. FeII -FeIII layered double hydroxide, commonly called green rust ( GR ), and MnIII -MnIV birnessite ( Bir ) are also well known to be reactive solid compounds. Therefore, studying the chemical interactions between Fe and Mn species could contribute to understanding the interactions between their respective biogeochemical cycles. Moreover, ferromanganese solid compounds are potentially interesting materials for water treatment. Here, a {Fe(OH)2 , FeII aq } mixture was oxidized by Bir in sulphated aqueous media in the presence or absence of dissolved O2 ...

We report the syntheses of a family of tetrahedral iron complexes bearing a bulky redox active o-phenylenediamide ligand. The electronic structures of these complexes have been investigated by Mössbauer spectroscopy, magnetic susceptibility measurements, and X-ray crystallography.

The investigation of elemental composition, crystal structure and thermal behavior of vonsenite and hulsite from the Titovskoe boron deposit in Russia is reported. The structures of the borates are described in terms of cation-centered and oxocentred polyhedra. There are different sequences of double chains and layers consisting of oxocentred [OM4 ]n + tetrahedra and [OM5 ]n + tetragonal pyramids forming a framework. Elemental composition was determined by energy-dispersive X-ray spectroscopy (EDX). Oxidation states and coordination sites of iron and tin in the oxoborates are determined using Mössbauer spectroscopy and compared with EDX and X-ray diffraction data (XRD)...

An accurate single-crystal X-ray diffraction study of bismuth-containing HoFe3 (BO3 )4 between 11 and 500 K has revealed structural phase transition at Tstr = 365 K. The Bi atoms enter the composition from Bi2 Mo3 O12 -based flux during crystal growth and significantly affect Tstr . The content of Bi was estimated by two independent methods, establishing the composition as (Ho0.96 Bi0.04 )Fe3 (BO3 )4 . In the low-temperature (LT) phase below Tstr the (Ho0.96 Bi0.04 )Fe3 (BO3 )4 crystal symmetry is trigonal, of space group P31 21, whereas at high temperature (HT) above 365 K the symmetry increases to space group R32...

Recently, the iron containing langasite-type crystal Ba3 NbFe3 Si2 O14 has attracted great attention as a new magnetically induced multiferroic. In this work, magnetic, structural and electronic properties of the multiferroic Ba3 NbFe3 Si2 O14 were investigated by several methods, including synchrotron X-ray diffraction, Raman spectroscopy and synchrotron Mössbauer source technique at high quasi-hydrostatic pressures (up to 70 GPa), created in diamond anvil cells. At room temperature, two structural transitions at pressures of about 3...

With the aim of demonstrating phase coexistence of two magnetic phases in an intermediate annealing regime and obtaining highly coercive FePt nanocomposite magnets, two alloys of slightly off-equiatomic composition of a binary Fe-Pt system were prepared by dynamic rotation switching and ball milling. The alloys, with a composition Fe53 Pt47 and Fe55 Pt45 , were subsequently annealed at 400 °C and 550 °C and structurally and magnetically characterized by means of X-ray diffraction, 57 Fe Mössbauer spectrometry and Superconducting Quantum Interference Device (SQUID) magnetometry measurements...

Iron phthalocyanine (FePc) is a promising non-precious catalyst for the oxygen reduction reaction (ORR). Unfortunately, FePc with plane-symmetric FeN4 site usually exhibits an unsatisfactory ORR activity due to its poor O2 adsorption and activation. Here, we report an axial Fe-O coordination induced electronic localization strategy to improve its O2 adsorption, activation and thus the ORR performance. Theoretical calculations indicate that the Fe-O coordination evokes the electronic localization among the axial direction of O-FeN4 sites to enhance O2 adsorption and activation...

Sodium-ion batteries (NaIBs) are increasingly being envisioned for grid-scale energy-storage systems because of cost advantages. However, implementation of this vision has been challenged by the low-energy densities delivered by most NaIB cathodes. Toward addressing this challenge, the authors report the synthesis and characterization of a new iron-doped Na3 Fe0.3 V1.7 O(PO4 )2 F2 cathode using a novel facile hydrothermal route. The synthesized material was characterized using scanning electron microscopy, X-ray diffraction, and Mössbauer spectroscopy techniques...

A tin-supported iron catalyst produces 5.9 turnovers of NH3 from N2, using [Ph2NH2]OTf as the acid and CoCp2* as the reductant. Two redox states of the Fe(N2) adduct and an Fe silyldiazenido complex were characterized using X-ray crystallography along with NMR and Mössbauer spectroscopies. Density functional theory calculations reveal that the charge on the Sn center correlates strongly with both the polarization of the N2 moiety and the charge on the distal N atom.

Proton conductive materials have attracted extensive interest in recent years due to their fascinating applications in sensors, batteries, and proton exchange membrane fuel cells. Herein, two Fe-diphosphonate chains (H4 -BAPEN)0.5 ·[FeIII (H-HEDP)(HEDP)0.5 (H2 O)] ( 1 ) and (H4 -TETA)2 ·[FeIII 2 FeII (H-HEDP)2 (HEDP)2 (OH)2 ]·2H2 O ( 2 ) (HEDP = 1-hydroxyethylidenediphosphonate, BAPEN = 1,2-bis(3-aminopropylamino)ethane, and TETA = triethylenetetramine) with different templating agents were prepared by hydrothermal reactions...

Extended metal atom chain (EMAC) complexes of first-row transition metals with metal-metal bonds have the potential to elicit unique magnetic properties and reactivities. Until now, the library of EMAC complexes with late-first-row transition metals was incomplete because of the omission of a triiron species with Fe-Fe bonding. Herein we report the synthesis and preliminary investigation of the first linear, triiron(II) complex containing close Fe-Fe interactions. The complex is supported by three dianionic 2,6-bis[(trimethylsilyl)amido]pyridine ligands ( L ), with an overall composition of Fe 3 L 3 , and pseudohelical ligand coordination stabilizing the local trigonal-planar geometry at each iron...

Developing O2 -selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal-organic framework materials of the type A x Fe2 (bdp)3 (A = Na+ , K+ ; bdp2- = 1,4-benzenedipyrazolate; 0 < x ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O2 over N2 at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including 23 Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O2 uptake...

Imogolite and magnetic imogolite-Fe oxide nanocomposites (Imo-Fe50 and Imo-Fe25 , at 50 and 25 % Fe loading (w/w), respectively) were synthesized and tested for the removal of aqueous copper (Cu), cadmium (Cd), and arsenic (As) pollutants. The materials were characterized by transmission electron microscopy, and specific surface area and isoelectric point measurements. The Fe-containing samples were additionally characterized by Mössbauer spectroscopy and vibrating-sample magnetometry. Significant differences were found in the morphological, electrophoretic, and magnetic characteristics between imogolite and the nanocomposites...

Synchrotron X-ray powder diffraction data indicate that La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3 adopt distorted perovskite structures (space group Pnma) with A-site and B-site cation disorder. A combination of XPS and 57Fe Mössbauer data indicate the transition metal cations in the two phases adopt Mn3+/Rh4+ and Fe3+/Rh4+ oxidation state combinations respectively. Transport data indicate both phases are insulating, with ρ vs. T dependences consistent with 3D variable-range hopping. Magnetisation data reveal that La0...