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Martin Clémancey, Thibault Cantat, Geneviève Blondin, Jean-Marc Latour, Pierre Dorlet, Guillaume Lefèvre
Mechanistic studies of the reduction of Fe(III) and Fe(II) salts by aryl Grignard reagents in toluene/tetrahydrofuran mixtures in the absence of a supporting ligand, as well as structural insights regarding the nature of the low-valent iron species obtained at the end of this reduction process, are reported. It is shown that several reduction pathways can be followed, depending on the starting iron precursor. We demonstrate, moreover, that these pathways lead to a mixture of Fe(0) and Fe(I) complexes regardless of the nature of the precursor...
March 15, 2017: Inorganic Chemistry
Airi Kawamura, Arin R Greenwood, Alexander S Filatov, Audrey T Gallagher, Giulia Galli, John S Anderson
A series of isoreticular metal-organic frameworks (MOFs) of the formula M(BDC)(L) (M = Fe(II) or Co(II), BDC = 1,4-benzenedicarboxylate, L = pyrazine (pyz) or 4,4'-bipyridine (bipy)) has been synthesized and characterized by N2 gas uptake measurements, single crystal and powder X-ray diffraction, magnetometry, X-ray absorption spectroscopy, and Mössbauer spectroscopy. These studies indicate the formation of a permanently porous solid with high-spin Fe(II) and Co(II) centers that are weakly coupled, consistent with first-principles density functional theory calculations...
March 3, 2017: Inorganic Chemistry
Zeba Haque, Gohil Singh Thakur, Rangasamy Parthasarathy, Birgit Gerke, Theresa Block, Lukas Heletta, Rainer Pöttgen, Amish G Joshi, Ganesan Kalai Selvan, Sonachalam Arumugam, Laxmi Chand Gupta, Ashok Kumar Ganguli
We have synthesized two new Eu-based compounds, EuSr2Bi2S4F4 and Eu2SrBi2S4F4, which are derivatives of Eu3Bi2S4F4, an intrinsic superconductor with Tc = 1.5 K. They belong to a tetragonal structure (SG: I4/mmm, Z = 2), similar to the parent compound Eu3Bi2S4F4. Our structural and (151)Eu Mössbauer spectroscopy studies show that, in EuSr2Bi2S4F4, Eu-atoms exclusively occupy the crystallographic 2a-sites. In Eu2SrBi2S4F4, 2a-sites are fully occupied by Eu-atoms and the other half of Eu-atoms and Sr-atoms together fully occupy 4e-sites in a statistical distribution...
February 28, 2017: Inorganic Chemistry
Brian Ginn, Christof Meile, Jared Wilmoth, Yuanzhi Tang, Aaron Thompson
Iron oxides are important structural and biogeochemical components of soils that can be strongly altered by redox-driven processes. This study examined the influence of temporal oxygen variations on Fe speciation in soils from the Luquillo Critical Zone Observatory (Puerto Rico). We incubated soils under cycles of oxic-anoxic conditions (τoxic:τanoxic = 1:6) at three frequencies with and without phosphate addition. Fe(II) production, P availability, and Fe mineral composition were monitored using batch analytical and spectroscopic techniques...
February 28, 2017: Environmental Science & Technology
Daniel L Reger, Andrea E Pascui, Elizabeth A Foley, Mark D Smith, Julia Jezierska, Agnieszka Wojciechowska, Sebastian A Stoian, Andrew Ozarowski
A series of monochloride-bridged, dinuclear metallacycles of the general formula [M2(μ-Cl)(μ-L)2](ClO4)3 have been prepared using the third-generation, ditopic bis(pyrazolyl)methane ligands L = m-bis[bis(1-pyrazolyl)methyl]benzene (Lm), M = Cu(II), Zn(II), and L = m-bis[bis(3,5-dimethyl-1-pyrazolyl)methyl]benzene (Lm*), M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II). These complexes were synthesized from the direct reactions of M(ClO4)2·6H2O, MCl2, and the ligand, Lm or Lm*, in the appropriate stoichiometric amounts...
February 20, 2017: Inorganic Chemistry
Joshua D Wofford, Mrinmoy Chakrabarti, Paul Alan Lindahl
Cardiac function requires continuous high levels of energy, and so iron, a critical player in mitochondrial respiration, is an important component of the heart. Hearts from (57)Fe-enriched mice were evaluated by Mossbauer spectroscopy. Spectra consisted of a sextet and two quadrupole doublets. One doublet was due to residual blood while the other was due to [Fe4S4](2+) clusters and Fe(II) hemes, most of which were associated with mitochondrial respiration. The sextet was due to ferritin; there was no evidence of hemosiderin, a ferritin decomposition product...
February 15, 2017: Journal of Biological Chemistry
Sebastian F M Schmidt, Changhyun Koo, Valeriu Mereacre, Jaena Park, Dieter W Heermann, Vladislav Kataev, Christopher E Anson, Denis Prodius, Ghenadie Novitchi, Rüdiger Klingeler, Annie K Powell
We present the synthesis, structure, magnetic properties, as well as the Mössbauer and electron paramagnetic resonance studies of a ring-shaped [Fe(III)4Ln(III)2(Htea)4(μ-N3)4(N3)3(piv)3] (Ln = Y 1, Gd 2, Tb 3, Dy 4, Ho 5, Er, 6) coordination cluster. The Dy, Tb, and Ho analogues show blocking of the magnetization at low temperatures without applied fields. The anisotropy of the 3d ion and the exchange interaction between 3d and 4f ions in Fe4Ln2 complexes are unambiguously determined by high-field/high-frequency electron paramagnetic resonance measurements at low temperature...
February 10, 2017: Inorganic Chemistry
R A Susilo, J M Cadogan, W D Hutchison, G A Stewart, M Avdeev, S J Campbell
We have investigated the low temperature magnetic properties of Dy2Fe2Si2C by using magnetisation, specific heat, x-ray diffraction, neutron powder diffraction and (57)Fe Mössbauer spectroscopy measurements over the temperature range 1.5 K-300 K. Dy2Fe2Si2C exhibits two magnetic transitions at low temperatures: an antiferromagnetic transition at [Formula: see text] K and a spin-reorientation transition at [Formula: see text] K. The magnetic structure above T t can be described with a propagation vector [Formula: see text] with the ordering of the Dy magnetic moments along the monoclinic b-axis whereas on cooling below T t the Dy moment tips away from the b-axis towards the ac-plane...
March 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Torben Esmann Mølholt, Haraldur Gunnlaugsson, Karl Johnston, Roberto Mantovan, Jens Röder, V Adoons, Adeleh Gerami, Hilary Masenda, Y Matveyev, M Ncube, Iraultza Unzueta, Krish Bharuth-Ram, Haflidi Gislason, P Krastev, Guido Langouche, Deena Naidoo, Sveinn Olafsson, A Zenkevich
The common charge states of Sn are 2+ and 4+. While charge neutrality considerations favour 2+ to be the natural charge state of Sn in ZnO, there are several reports suggesting the 4+ state instead. In order to investigate the charge states, lattice sites, and the effect of the ion implantation process of dilute Sn atoms in ZnO, we have performed <sup>119</sup>Sn emission Mössbauer spectroscopy on ZnO single crystal samples following ion implantation of radioactive <sup>119</sup>In (<i>T</i><sub>½</sub> = 2...
February 6, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Barbara Lyson-Sypien, Anna Kusior, Mieczylaw Rekas, Jan Zukrowski, Marta Gajewska, Katarzyna Michalow-Mauke, Thomas Graule, Marta Radecka, Katarzyna Zakrzewska
The aim of this research is to study the role of nanocrystalline TiO2/SnO2 n-n heterojunctions for hydrogen sensing. Nanopowders of pure SnO2, 90 mol % SnO2/10 mol % TiO2, 10 mol % SnO2/90 mol % TiO2 and pure TiO2 have been obtained using flame spray synthesis (FSS). The samples have been characterized by BET, XRD, SEM, HR-TEM, Mössbauer effect and impedance spectroscopy. Gas-sensing experiments have been performed for H2 concentrations of 1-3000 ppm at 200-400 °C. The nanomaterials are well-crystallized, anatase TiO2, rutile TiO2 and cassiterite SnO2 polymorphic forms are present depending on the chemical composition of the powders...
2017: Beilstein Journal of Nanotechnology
Bernhard Schäfer, Thomas Bauer, Isabelle Faus, Juliusz A Wolny, Fabian Dahms, Olaf Fuhr, Sergei Lebedkin, Hans-Christian Wille, Kai Schlage, Katharina Chevalier, Fabian Rupp, Rolf Diller, Volker Schünemann, Manfred M Kappes, Mario Ruben
A heterotrinuclear [Pt2Fe] spin crossover (SCO) complex was developed and synthesized employing a ditopic bridging bpp-alkynyl ligand L and alkynyl coordinated Pt(II) terpy units: [Fe(II)(L-Pt(II))2]2(BF4)2 (1). We identified two different types of crystals of 1 which differ in their molecular packing and the number of co-crystallized solvent molecules: 1H (1·3.5CH2Cl2 in P1[combining macron]) and 1L (1·10CH2Cl2 in C2/c); while 1L shows a reversible SCO with a transition temperature of 268 K, the analogous compound 1H does not show any SCO and remains blocked in the HS state...
January 30, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Sergiu Shova, Maria Cazacu, Ghenadie Novitchi, Giorgio Zoppellaro, Cyrille Train, Vladimir B Arion
A new iron(iii)-centred ferric wheel Fe⊂{Fe6} of the formula [Fe7(H2L)6(NCS)6](ClO4)3·10H2O, where H4L = N,N'-bis(3-carboxylsalicylidene)-1,3-bis(3-aminopropyl)tetramethyldisiloxane, was synthesised and fully characterised. (57)Fe Mössbauer spectra indicate the presence of high spin (S = 5/2) Fe(3+) cations adopting a slightly different coordination environment in agreement with the X-ray diffraction structure. There are competing antiferromagnetic exchange interactions along the rim (J1 = -1.00 cm(-1)) and the radius (J2 = -1...
January 25, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Hiroyuki Hayashi, Shota Katayama, Takahiro Komura, Yoyo Hinuma, Tomoyasu Yokoyama, Ko Mibu, Fumiyasu Oba, Isao Tanaka
Daylight-driven photocatalysts have attracted much attention in the context of "green" technology. Although various active materials have been reported and their applications are rapidly increasing, many are discovered after enormous experimental efforts. Herein the discovery of a novel oxide photocatalyst, β-SnMoO4, is demonstrated via a rational search of 3483 known and hypothetical compounds with various compositions and structures over the whole range of SnO-MO q/2 (M: Ti, Zr, and Hf (q = 4); V, Nb, and Ta (q = 5); Cr, Mo, and W (q = 6)) pseudobinary systems...
January 2017: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Javier Fernández Sanjulián, Madhu Chennabasappa, Susana García-Martín, Gwilherm Nénert, Alain Wattiaux, Etienne Gaudin, Olivier Toulemonde
SrFe0.25Co0.75O2.63 was synthesized by a solid-state reaction. Its structural study at room temperature using conventional X-ray as well as neutron powder diffraction, electron diffraction and high-resolution transmission electron microscopy is presented. An oxygen-vacancy ordering related to the "314" model known for the Sr3Y1Co4O10.5 oxide is proposed despite neither an A-site ordering nor an A-site mismatch. By means of Mössbauer spectroscopy, Mohr salt titration and the difference in the neutron cross sections of Fe and Co, a cation distribution within the crystallographic sites as the following Sr4(Fe0...
January 18, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Spencer C Peck, Chen Wang, Laura M K Dassama, Bo Zhang, Yisong Guo, Lauren J Rajakovich, J Martin Bollinger, Carsten Krebs, Wilfred A van der Donk
Activation of O-H bonds by inorganic metal-oxo complexes has been documented, but no cognate enzymatic process is known. Our mechanistic analysis of 2-hydroxyethylphosphonate dioxygenase (HEPD), which cleaves the C1-C2 bond of its substrate to afford hydroxymethylphosphonate on the biosynthetic pathway to the commercial herbicide phosphinothricin, uncovered an example of such an O-H-bond-cleavage event. Stopped-flow UV-visible absorption and freeze-quench Mössbauer experiments identified a transient iron(IV)-oxo (ferryl) complex...
February 8, 2017: Journal of the American Chemical Society
Madhumita Dalal, Ayan Mallick, Jean-Marc Greneche, Dipankar Das, Pabitra K Chakrabarti
Nanocrystalline samples of Ni0.3Zn0.4Co0.2Cu0.1Fe2O4 (NZCCF) are prepared by a simple co-precipitation method. To obtain nanoparticles of different sizes, the as prepared sample is annealed at 400, 600, 800 and 1000 °C. Nanoparticles of the sample annealed at 600 °C are encapsulated in multi-walled carbon nanotubes (MWCNT). To confirm the crystallographic phase, x-ray diffraction (XRD) patterns are analyzed by the Rietveld method and cation distribution in A- and B-sites is estimated from the analysis. Occupancy of Zn(2+) ions in A-site and that of Fe(3+) ions in B-site increase with the increase of annealing temperature (T A) and lattice parameters lie within 8...
March 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xiao Ma, Chen-Sheng Lin, Xiao-Quan Zhu, Sheng-Min Hu, Tian-Lu Sheng, Xin-Tao Wu
The heterometallic complexes trans-[Cp(dppe)FeNCRu(o-bpy)CNFe(dppe)Cp][PF6 ]n (1[PF6 ]n , n=2, 3, 4; o-bpy=1,2-bis(2,2'-bipyridyl-6-yl)ethane, dppe=1,2-bis(diphenylphosphino)ethane, Cp=1,3-cyclopentadiene) in three distinct states have been synthesized and fully characterized. 1(3+) [PF6 ]3 and 1(4+) [PF6 ]4 are the one- and two-electron oxidation products of 1(2+) [PF6 ]2 , respectively. The investigated results suggest that 1[PF6 ]3 is a Class II mixed valence compound. 1[PF6 ]4 after a thermal treatment at 400 K shows an unusually delocalized mixed valence state of [Fe(III) -NC-Ru(III) -CN-Fe(II) ], which is induced by electron transfer from the central Ru(II) to the terminal Fe(III) in 1[PF6 ]4 , which was confirmed by IR spectroscopy, magnetic data, and EPR and Mössbauer spectroscopy...
January 12, 2017: Angewandte Chemie
Yi-Fei Deng, Tian Han, Wei Xue, Naoaki Hayashi, Hiroshi Kageyama, Yan-Zhen Zheng
One-dimensional spin chains featuring strong axial anisotropic magnetism are promising candidates for isolatable and miniatured information storage materials, the so-called single-chain magnets (SCMs). Here we show a mixed azido/carboxylato bridged metamagnetic iron(ii) chain [Fe(N3)2(4-mpc)]n (4-mpc = N-methylpyridinium-4-carboxylate) with a large energy barrier of 150 K, a large remnant magnetization (1.55Nβ) and coercivity (1.7 T at 2 K) for homo-spin SCMs. Heat capacity and Mössbauer spectroscopy studies corroborate the intrinsic nature of SCM behavior regardless of weak interchain magnetic interactions, which lead to the coexistence of metamagnetism but not long-range magnetic ordering...
January 11, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Ragnar Bjornsson, Frank Neese, Serena DeBeer
Despite decades of research, the structure-activity relationship of nitrogenase is still not understood. Only recently was the full molecular structure of the FeMo cofactor (FeMoco) revealed, but the charge and metal oxidation states of FeMoco have been controversial. With the recent identification of the interstitial atom as a carbide and the more recent revised oxidation-state assignment of the molybdenum atom as Mo(III), here we revisit the Mössbauer properties of FeMoco. By a detailed error analysis of density functional theory-computed isomer shifts and computing isomer shifts relative to the P-cluster, we find that only the charge of [MoFe7S9C](1-) fits the experimental data...
January 10, 2017: Inorganic Chemistry
Susana García-Martín, Keisuke Manabe, Esteban Urones-Garrote, David Ávila-Brande, Noriya Ichikawa, Yuichi Shimakawa
Perovskite-related GdBaMnFeO5 and the corresponding oxidized phase GdBaMnFeO6, with long-range layered-type ordering of the Ba and Gd atoms have been synthesized. Oxidation retains the cation ordering but drives a modulation of the crystal structure associated with the incorporation of the oxygen atoms between the Gd layers. Oxidation of GdBaMnFeO5 increases the oxidation state of Mn from 2+ to 4+, while the oxidation state of Fe remains 3+. Determination of the crystal structure of both GdBaMnFeO5 and GdBaMnFeO6 is carried out at atomic resolution by means of a combination of advanced transmission electron microscopy techniques...
January 9, 2017: Inorganic Chemistry
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