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Valeriy Yu Verchenko, Sergei S Sokolov, Alexander A Tsirlin, Alexey V Sobolev, Igor A Presniakov, Mikhail A Bykov, Maria A Kirsanova, Andrei V Shevelkov
A new ternary telluride, Fe3-δAs1-yTe2, was synthesized from elements at 600 °C. It crystallizes in the hexagonal P63/mmc space group with the unit cell parameters a = 3.85091(9) Å and c = 17.1367(4) Å for δ = 0.3 and y = 0.04. Its layered crystal structure contains partially occupied intralayer and interlayer Fe positions, which give rise to significant nonstoichiometry: Fe3-δAs1-yTe2 was found to possess the homogeneity range of 0.25 < δ < 0.45 and y = 0.04. Regions of local vacancy ordering alternate with regions of randomly distributed vacancies, so that the ordering of Fe atoms and vacancies is not complete in the average structure...
October 3, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Wojciech Szczerba, Jan Żukrowski, Marek Przybylski, Marcin Sikora, Olga Safonova, Aleksey Shmeliov, Valeria Nicolosi, Michael Schneider, Tim Granath, Maximilian Oppmann, Marion Straßer, Karl Mandel
The maximum magnetisation (saturation magnetisation) obtainable for iron oxide nanoparticles can be increased by doping the nanocrystals with non-magnetic elements such as zinc. Herein, we closely study how only slightly different synthesis approaches towards such doped nanoparticles strongly influence the resulting sub-nano/atomic structure. We compare two co-precipitation approaches, where we only vary the base (NaOH versus NH3), and a thermal decomposition route. These methods are the most commonly applied ones for synthesising doped iron oxide nanoparticles...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Fernande Grandjean, Gary J Long
The proportionality constant, α, between the observed isomer shifts and the calculated electron probability density at the iron nucleus has been reevaluated in terms of the correct experimental isomer shifts relative to α-iron and their corresponding accuracy, which should be considered in the linear regression fit yielding α. The iron-57 excited state nuclear quadrupole moment, Q, is not a "relative" value and its widely accepted experimental value is 0.16(1) × 10(-28) m(2) as also confirmed by nuclear model calculations...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Dianne J Xiao, Julia Oktawiec, Phillip J Milner, Jeffrey R Long
Metal-organic frameworks are a new class of heterogeneous catalysts in which molecular-level control over both the immediate and long-range chemical environment surrounding a catalytic center can be readily achieved. Here, the oxidation of cyclohexane to cyclohexanol and cyclohexanone is used as a model reaction to investigate the effect of a hydrophobic pore environment on product selectivity and catalyst stability in a series of iron-based frameworks. Specifically, expanded analogues of Fe2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) were synthesized and evaluated, including the biphenyl derivative Fe2(dobpdc) (H4dobpdc = 4,4'-dihydroxy-[1,1'-biphenyl]-3,3'-dicarboxylic acid), the terphenyl derivative Fe2(dotpdc) (H4dotpdc = 4,4''-dihydroxy-[1,1':4',1''-terphenyl]-3,3''-dicarboxylic acid), and three modified terphenyl derivatives in which the central ring is replaced with tetrafluoro-, tetramethyl-, or di-tert-butylaryl groups...
October 5, 2016: Journal of the American Chemical Society
Sergey M Aksenov, Nikita V Chukanov, Vyacheslav S Rusakov, Taras L Panikorovskii, Ramiza K Rastsvetaeva, Ramil R Gainov, Farit G Vagizov, Konstantin A Lyssenko, Dmitry I Belakovskiy
Vesuvianite containing 5.85 wt% TiO2 from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, Pakistan, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement, (27)Al NMR, (57)Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are: a = 15.5326 (2), c = 11.8040 (2) Å, space group P4/nnc. The structure was refined to final R1 = 0...
October 1, 2016: Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials
M Shopska, D Paneva, G Kadinov, Z Cherkezova-Zheleva, I Mitov, M Iliev
The biogenic iron oxide/hydroxide materials possess useful combination of physicochemical properties and are considered for application in various areas. Their production does not require special investments because these compounds are formed during cultivation of neurophilic iron bacteria. Bacteria from genus Leptothrix develop intensively in the Sphaerotilus-Leptothrix group of bacteria isolation medium and feeding media of Fedorov and Lieske. These media are different in their composition which determined the present study as an attempt to clear up the reasons that define the differences in the composition of the laboratory-obtained biomasses and the natural biomass finds...
October 1, 2016: Applied Biochemistry and Biotechnology
Thibaut Molle, Yohann Moreau, Martin Clemancey, Farhad Forouhar, Jean-Luc Ravanat, Nicolas Duraffourg, Vincent Fourmond, Jean-Marc Latour, Serge Gambarelli, Etienne Mulliez, Mohamed Atta
RimO, a radical-S-adenosylmethionine (SAM) enzyme, catalyzes the specific C3 methylthiolation of the D89 residue in the ribosomal S12 protein. Two intact iron-sulfur clusters and two SAM cofactors both are required for catalysis. By using electron paramagnetic resonance, Mössbauer spectroscopies, and site-directed mutagenesis, we show how two SAM molecules sequentially bind to the unique iron site of the radical-SAM cluster for two distinct chemical reactions in RimO. Our data establish that the two SAM molecules bind the radical-SAM cluster to the unique iron site, and spectroscopic evidence obtained under strongly reducing conditions supports a mechanism in which the first molecule of SAM causes the reoxidation of the reduced radical-SAM cluster, impeding reductive cleavage of SAM to occur and allowing SAM to methylate a HS(-) ligand bound to the additional cluster...
October 6, 2016: Biochemistry
Bin Hu, Mingrui He, Zhen Yao, Charles E Schulz, Jianfeng Li
The synthesis and characterization of several electron-poor iron(II) porphyrin (FeTFPPBr8) complexes with axial imidazole ligands are reported. The single-crystal X-ray structures have been studied by a combination of crystal packing and Hirshfeld surface calculations, which explained the unusual axial-ligand geometries, e.g., the strong tilt of the Fe-NIm bonds and the imidazole planes. The six-coordinate [Fe(TFPPBr8)(1-MeIm)2] was studied by multiple-temperature solid-state Mössbauer spectroscopy, which suggested that it is a low-spin complex with δ ∼ 0...
October 3, 2016: Inorganic Chemistry
C Balasubramanian, B Joseph, P B Orpe, N L Saini, S Mukherjee, K Dziedzic-Kocurek, J Stanek, D Di Gioacchino, A Marcelli
Magnetic properties and phase compositions of iron-oxide nanoparticles synthesised by a high temperature arc plasma route have been investigated by Mössbauer spectroscopy and high harmonic magnetic AC susceptibility measurements, and correlated with morphological and structural properties for different synthesis conditions. The Mössbauer spectra precisely determined the presence of different iron-oxide fractions in the investigated nanoparticles, while the high harmonic magnetic susceptibility measurements revealed the occurrence of metastable magnetic phases evolving in temperature and time...
November 4, 2016: Nanotechnology
Wajid Rehman, Rehana Yasmeen, Fazal Rahim, Muhammad Waseem, Cun-Yue Guo, Zonera Hassan, Umer Rashid, Khurshid Ayub
The search for an alternative to platinum anticancer agents is a major motivation for continuing investigations concerning the antitumor properties of other transition metal-based compounds. Keeping this in view, synthesis, antitumor and antimicrobial activity of diorganotin (IV) complexes was studied. A novel series of diorganotin (IV) complexes of the Schiff base ligand derived from 7-methoxy-2-hydroxy-1-naphthaldehyde, 1,2-phenylenediamine, Salicylaldehyde were synthesized. Physical and spectral examination was done through various techniques using elemental analyses, IR, (1)H, (13)C, (119)Sn NMR, and (119m)Sn Mössbauer techniques respectively...
September 13, 2016: Journal of Photochemistry and Photobiology. B, Biology
Ethan A Hill, Andrew C Weitz, Elizabeth Onderko, Adrian Romero-Rivera, Yisong Guo, Marcel Swart, Emile L Bominaar, Michael T Green, Michael P Hendrich, David C Lacy, A S Borovik
High-valent Fe-OH species are often invoked as key intermediates but have only been observed in Compound II of cytochrome P450s. To further address the properties of non-heme Fe(IV)-OH complexes, we demonstrate the reversible protonation of a synthetic Fe(IV)-oxo species containing a tris-urea tripodal ligand. The same protonated Fe(IV)-oxo species can be prepared via oxidation, suggesting that a putative Fe(V)-oxo species was initially generated. Computational, Mössbauer, XAS, and NRVS studies indicate that protonation of the Fe(IV)-oxo complex most likely occurs on the tripodal ligand, which undergoes a structural change that results in the formation of a new intramolecular H-bond with the oxido ligand that aids in stabilizing the protonated adduct...
October 12, 2016: Journal of the American Chemical Society
Wen-Te Liao, Christoph H Keitel, Adriana Pálffy
Heralded entanglement between macroscopical samples is an important resource for present quantum technology protocols, allowing quantum communication over large distances. In such protocols, optical photons are typically used as information and entanglement carriers between macroscopic quantum memories placed in remote locations. Here we investigate theoretically a new implementation which employs more robust x-ray quanta to generate heralded entanglement between two crystal-hosted macroscopical nuclear ensembles...
2016: Scientific Reports
Deanna L Miller, Randall B Siedschlag, Laura J Clouston, Victor G Young, Yu-Sheng Chen, Eckhard Bill, Laura Gagliardi, Connie C Lu
A series of iron and iron-cobalt bimetallic complexes were isolated: LFe2Cl (1), LFe2 (2), Li(THF)3[LFe2Cl](Li(THF)3[2-Cl]), LFeCoCl (3), and LFeCo (4), where L is a trianionic tris(phosphineamido)amine ligand. As elucidated by single-crystal X-ray diffraction studies and quantum-chemical calculations, the Fe(II)Fe(II) and Fe(II)Co(II) complexes, 1 and 3, respectively, have weak metal-metal interactions (the metal-metal distances are 2.63 and 2.59 Å, respectively) with a partial bond order of 0.5. The formally mixed-valent complexes, Fe(II)Fe(I) (3) and Fe(II)Co(I) (4), have short metal-metal bonds (2...
October 3, 2016: Inorganic Chemistry
Soukaina El-Guendouz, Smail Aazza, Badiaa Lyoussi, Vassya Bankova, João P Lourenço, Ana M Rosa Costa, José F Mariano, Maria G Miguel, Maria L Faleiro
Biofilm bacteria are more resistant to antibiotics than planktonic cells. Propolis possesses antimicrobial activity. Generally, nanoparticles containing heavy metals possess antimicrobial and antibiofilm properties. In this study, the ability of adherence of Methicillin Resistant Strains of Staphylococcus aureus (MRSA) to catheters treated with magnetite nanoparticles (MNPs), produced by three methods and functionalized with oleic acid and a hydro-alcoholic extract of propolis from Morocco, was evaluated. The chemical composition of propolis was established by gas chromatography mass spectrometry (GC-MS), and the fabricated nanostructures characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Mossbauer spectroscopy and Fourrier transform infrared spectroscopy (FTIR)...
2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Yisong Guo, Carlos Echavarri-Erasun, Marie Demuez, Emilio Jiménez-Vicente, Emile L Bominaar, Luis M Rubio
The biological activation of N2 occurs at the FeMo-cofactor, a 7Fe-9S-Mo-C-homocitrate cluster. FeMo-cofactor formation involves assembly of a Fe6-8 -SX -C core precursor, NifB-co, which occurs on the NifB protein. Characterization of NifB-co in NifB is complicated by the dynamic nature of the assembly process and the presence of a permanent [4Fe-4S] cluster associated with the radical SAM chemistry for generating the central carbide. We have used the physiological carrier protein, NifX, which has been proposed to bind NifB-co and deliver it to the NifEN protein, upon which FeMo-cofactor assembly is ultimately completed...
October 4, 2016: Angewandte Chemie
Pierfranco Demontis, Giuseppe B Suffritti
As an attempt to explain some of the many anomalies and unresolved problems which have been reported about the dynamic behavior of particles and molecules absorbed in crystalline solids, the "reverse Mössbauer effect" (RME) is proposed. RME theory posits that a particle in non-equilibrium state with respect to a crystal (colliding with the crystal or absorbed in it, but set out of thermal equilibrium by some external cause) is scattered by the whole crystal with a momentum proportional to a vector representing a reciprocal lattice point...
September 7, 2016: Journal of Chemical Physics
Georg Schmid, Hendrik Auerbach, Antonio J Pierik, Volker Schünemann, Matthias Boll
The class I benzoyl-coenzyme A (BzCoA) reductases (BCRs) are key enzymes in the anaerobic degradation of aromatic compounds that catalyze the ATP-dependent dearomatization of their substrate to a cyclic dienoyl-CoA. The phylogenetically distinct Thauera- and Azoarcus-type BCR subclasses are iron-sulfur enzymes and consist of an ATP-hydrolyzing electron activation module and a BzCoA reduction module. More than 20 years after their initial identification, all biochemical information about class I BCRs derives from studies of the wild-type enzyme from the denitrifying bacterium Thauera aromatica (BCRTaro)...
October 4, 2016: Biochemistry
K Kothapalli, A E Böhmer, W T Jayasekara, B G Ueland, P Das, A Sapkota, V Taufour, Y Xiao, E Alp, S L Bud'ko, P C Canfield, A Kreyssig, A I Goldman
A hallmark of the iron-based superconductors is the strong coupling between magnetic, structural and electronic degrees of freedom. However, a universal picture of the normal state properties of these compounds has been confounded by recent investigations of FeSe where the nematic (structural) and magnetic transitions appear to be decoupled. Here, using synchrotron-based high-energy x-ray diffraction and time-domain Mössbauer spectroscopy, we show that nematicity and magnetism in FeSe under applied pressure are indeed strongly coupled...
2016: Nature Communications
P Wilfert, A Mandalidis, A I Dugulan, K Goubitz, L Korving, H Temmink, G J Witkamp, M C M Van Loosdrecht
Iron is an important element for modern sewage treatment, inter alia to remove phosphorus from sewage. However, phosphorus recovery from iron phosphorus containing sewage sludge, without incineration, is not yet economical. We believe, increasing the knowledge about iron-phosphorus speciation in sewage sludge can help to identify new routes for phosphorus recovery. Surplus and digested sludge of two sewage treatment plants was investigated. The plants relied either solely on iron based phosphorus removal or on biological phosphorus removal supported by iron dosing...
November 1, 2016: Water Research
Judith A Serth-Guzzo, Ilona Turowska-Tyrk, Martin K Safo, F Ann Walker, Peter G Debrunner, W Robert Scheidt
The reaction of [Fe(TMP)(OClO3)], where TMP is the dianion of tetramesitylporphyrin, with a combination of a strong π-acceptor ligand and a π-donating imidazole can lead to the preparation of mixed-ligand complexes [Fe(Porph)(4-CNPy)(L)](+) where L is imidazole itself or 1-acetylimidazole and 4-cyanopyridine is the strong π acceptor ligand. The stability of the new mixed-ligand pair is the presumed result of synergic bonding between the two axial ligands. The molecular structure and other characterization of the new mixed axial ligand complex, [Fe(TMP)(4-CNPy)(HIm)]ClO4 is described...
January 2016: Journal of Porphyrins and Phthalocyanines
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