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Agnieszka Magdziarz, Juan C Colmenares, Olga Chernyayeva, Dmytro Lisovytskiy, Justyna Grzonka, Krzysztof Kurzydłowski, Kinga Freindl, Józef Korecki
Fe(3+)/TiO2/zeolite Y photocatalyst synthesized by using sonophotodeposition method was compared with photocatalysts prepared by simple photodeposition and sonodeposition methods in order to clarify the role of light irradiation and ultrasounds while they are used simultaneously. To gain an insight into the mechanism of this method a detailed characterization of the photocatalysts was carried out by means of the following techniques: UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, Mössbauer measurements and photocatalytic test reaction...
September 2017: Ultrasonics Sonochemistry
Lian Duan, Xiang Zhang, Wenjun Zheng
Two 1,2-diaza-4-phosphaferrocenes [(η(5)-3,5-R2dp)Fe(η(5)-CpMe5)] (R = tBu (3), Ph (4)) with a single η(5) ring containing two nitrogen atoms are prepared. Mössbauer spectroscopic, electrochemical, and density functional theory (DFT) studies have provided a more detailed understanding of the electronic structures and stabilities of these complexes.
June 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Martin Tzvetkov, Maria Milanova, Zara Cherkezova-Zheleva, Ivanka Spassova, Evgenia Valcheva, Joana Zaharieva, Mitov Ivan
A combination of thermal and mechanical (high energy ball milling) treatment was applied in an attempt to obtain polycrystalline mixed metal binary and ternary oxides of the type CoxZn1-xFe2O4 (x = 0; 0.25; 0.5; 0.75; 1). The synthetic procedure used successfully produced single-phased, homogeneous ZnFe2O4, CoFe2O4, and Co0.75Zn0.25Fe2O4, as well as mixed oxides, whose composition depended both on the duration of the high energy ball milling and the ratio Zn(II)/Co(II). The formation of spinel-like structures was proved by XRD, Mössbauer spectroscopy and Raman spectroscopy...
June 2017: Acta Chimica Slovenica
Gagan Kumar, R K Kotnala, Jyoti Shah, Vijay Kumar, Arun Kumar, Pooja Dhiman, M Singh
The effect of Co(2+) substitution into nanocrystalline Mg-Mn ferrite synthesized by a solution combustion technique has been studied. The cation distribution has been inferred from X-ray diffraction, the magnetization technique, and Mössbauer spectroscopy. The X-ray analysis and cation distribution data have been used to investigate the detailed structural parameters such as hopping lengths, ionic radii of tetrahedral and octahedral sites, oxygen positional parameter, site bond as well as edge lengths, bond lengths, and bond angles...
June 16, 2017: Physical Chemistry Chemical Physics: PCCP
Chunmei Chen, Ravi K Kukkadapu, Olesya Lazareva, Donald L Sparks
Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic (XAS) techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplains, which exhibited a succession of oxic, anoxic and suboxic-oxic zones with increasing depth along the vertical profiles. The incised stream channel is bounded on the east by a narrow floodplain and a steep hillslope, and on the west by a broad floodplain...
June 15, 2017: Environmental Science & Technology
Demyan E Prokopchuk, Eric S Wiedner, Eric D Walter, Codrina V Popescu, Nicholas A Piro, W Scott Kassel, R Morris Bullock, Michael T Mock
The geometric constraints imposed by a tetradentate P4N2 ligand play an essential role in stabilizing square planar Fe complexes with changes in metal oxidation state. A combination of high-pressure electrochemistry and variable temperature UV-vis spectroscopy were used to obtain thermodynamic measurements of N2 binding. In addition, X-ray crystallography, 57Fe Mössbauer spectroscopy, and EPR spectroscopy were used to fully characterize these new compounds. Analysis of Fe0, FeI, and FeII complexes reveals that the free energy of N2 binding across three oxidation states spans more than 37 kcal mol-1...
June 14, 2017: Journal of the American Chemical Society
Gursu Culcu, Diana A Iovan, Jeremy P Krogman, Matthew J T Wilding, Mark W Bezpalko, Bruce M Foxman, Christine M Thomas
Heterometallic multiple bonds between niobium and other transition metals have not been reported to date, likely owing to the highly reactive nature of low valent niobium centers. Herein, a C3-symmetric tris(phosphinoamide) ligand framework is used to construct a Nb/Fe heterobimetallic complex Cl-Nb(iPrNPPh2)3Fe-Br (2), which features a Fe→Nb dative bond with a metal-metal distance of 2.4269(4) Å. Reduction of 2 in the presence of PMe3 affords Nb((i)PrNPPh2)3Fe-PMe3 (6), a compound with an unusual trigonal pyramidal geometry at a Nb(III) center, a Nb≡Fe triple bond, and the shortest bond distance (2...
June 14, 2017: Journal of the American Chemical Society
Kevin J Anderton, Brian J Knight, Arnold L Rheingold, Khalil A Abboud, Ricardo García-Serres, Leslie J Murray
The triiron trihydride complex Fe3H3L (1) [where L(3-) is a tris(β-diketiminate)cyclophanate] reacts with CO and with BF3·OEt2 to afford (Fe(I)CO)2Fe(II)(μ3-H)L (2) and Fe3F3L (3), respectively. Variable-temperature and applied-field Mössbauer spectroscopy support the assignment of two high-spin (HS) iron(i) centers and one HS iron(ii) ion in 2. Preliminary studies support a CO-induced reductive elimination of H2 from 1, rather than CO trapping a species from an equilibrium mixture. This complex reacts with H2 to regenerate 1 under a dihydrogen atmosphere, which represents a rare example of reversible CO/H2 exchange and the first to occur at high-spin metal centers, as well as the first example of a reversible multielectron redox reaction at a designed high-spin metal cluster...
May 1, 2017: Chemical Science
Gerard Sabenya, Laura Lazaro, Ilaria Gamba, Vlad Martin-Diaconescu, Erik Andris, Thomas Weyhermüller, Frank Neese, Jana Roithova, Eckhard Bill, Julio Lloret-Fillol, Miquel Costas
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 state (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, respectively, and the FT-IR spectra showed an unusually low N - N stretching frequency (2019 cm-1), suggesting that the FeN - N2 bond is particularly weak...
June 9, 2017: Journal of the American Chemical Society
Mark R Ringenberg, Florian Wittkamp, Ulf-Peter Apfel, Wolfgang Kaim
The tricarbonyliron (TCFe) complexes Fe(CO)3(dppf) and Fe(CO)3(dppp), where dppf = 1,1'-bis(diphenylphosphino)ferrocene and dppp = 1,3-bis(diphenylphosphino)propane, exhibit redox activity that induces configurational isomerization. The presence of the ferrocenyl (Fc) group stabilizes higher oxidized forms of TCFe. Using spectroelectrochemistry (IR, UV-vis, Mössbauer, and EPR) and computational analysis, we can show that the Fc in the backbone of the dppf ligand tends to form a weak dative bond to the electrophilic TCFe(I) and TCFe(II) species...
June 9, 2017: Inorganic Chemistry
Laurel K ThomasArrigo, Christian Mikutta, James Byrne, Andreas Kappler, Ruben Kretzschmar
In freshwater wetlands, organic flocs are often found enriched in trace metal(loid)s associated with poorly crystalline Fe(III)-(oxyhydr)oxides. Under reducing conditions, flocs may become exposed to aqueous Fe(II), triggering Fe(II)-catalyzed mineral transformations and trace metal(loid) release. In this study, pure ferrihydrite, a synthetic ferrihydrite-polygalacturonic acid coprecipitate (16.7 wt % C), and As- (1280 and 1230 mg/kg) and organic matter (OM)-rich (18.1 and 21.8 wt % C) freshwater flocs dominated by ferrihydrite and nanocrystalline lepidocrocite were reacted with an isotopically enriched (57)Fe(II) solution (0...
June 7, 2017: Environmental Science & Technology
Jonny Proppe, Markus Reiher
One of the major challenges in computational science is to determine the uncertainty of a virtual measurement, that is the prediction of an observable based on calculations. As highly accurate first-principles calculations are in general unfeasible for most physical systems, one usually resorts to parameteric property models of observables, which require calibration by incorporating reference data. The resulting predictions and their uncertainties are sensitive to systematic errors such as inconsistent reference data, parametric model assumptions, or inadequate computational methods...
June 5, 2017: Journal of Chemical Theory and Computation
V Augustyns, M Trekels, H P Gunnlaugsson, H Masenda, K Temst, A Vantomme, L M C Pereira
We describe an experimental setup for conversion electron Mössbauer spectroscopy (CEMS) at low temperature. The setup is composed of a continuous flow cryostat (temperature range of 4.2-500 K), detector housing, three channel electron multipliers, and corresponding electronics. We demonstrate the capabilities of the setup with CEMS measurements performed on a sample consisting of a thin enriched (57)Fe film, with a thickness of 20 nm, deposited on a silicon substrate. We also describe exchangeable adaptations (lid and sample holder) which extend the applicability of the setup to emission Mössbauer spectroscopy as well as measurements under an applied magnetic field...
May 2017: Review of Scientific Instruments
Shyam K Gore, Santosh S Jadhav, Vijaykumar V Jadhav, S M Patange, Mu Naushad, Rajaram S Mane, Kwang Ho Kim
The bismuth (Bi(3+))-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. To obtain information about the phase analysis and structural parameters, like lattice constant, Rietveld refinement process is applied. The replacement of divalent Co(2+) by trivalent Bi(3+) cations have been confirmed from energy dispersive analysis of the ferrite samples. The micro-structural evolution of cobalt ferrite powders at room temperature under various Bi(3+) doping levels have been identified from the digital photoimages recorded using scanning electron microscopy...
May 31, 2017: Scientific Reports
Lucı A Piñeiro-López, Francisco Javier Valverde-Muñoz, Maksym Seredyuk, M Carmen Muñoz, Matti Haukka, José Antonio Real
The synthesis, crystal structure, magnetic, calorimetric, and Mössbauer studies of a series of new Hofmann-type spin crossover (SCO) metal-organic frameworks (MOFs) is reported. The new SCO-MOFs arise from self-assembly of Fe(II), bis(4-pyridyl)butadiyne (bpb), and [Ag(CN)2](-) or [M(II)(CN)4](2-) (M(II) = Ni, Pd). Interpenetration of four identical 3D networks with α-Po topology are obtained for {Fe(bpb)[Ag(I)(CN)2]2} due to the length of the rod-like bismonodentate bpb and [Ag(CN)2](-) ligands. The four networks are tightly packed and organized in two subsets orthogonally interpenetrated, while the networks in each subset display parallel interpenetration...
May 30, 2017: Inorganic Chemistry
Uttam Chakraborty, Serhiy Demeshko, Franc Meyer, Christophe Rebreyend, Bas de Bruin, Mihail Atanasov, Frank Neese, Bernd Mühldorf, Robert Wolf
The 15 valence-electron iron(I) complex [Cp(Ar) Fe(IiPr2 Me2 )] (1, Cp(Ar) =C5 (C6 H4 -4-Et)5 ; IiPr2 Me2 =1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene) was synthesized in high yield from the Fe(II) precursor [Cp(Ar) Fe(μ-Br)]2 . (57) Fe Mössbauer and EPR spectroscopic data, magnetic measurements, and ab initio ligand-field calculations indicate an S= 3/2 ground state with a large negative zero-field splitting. As a consequence, 1 features magnetic anisotropy with an effective spin-reversal barrier of Ueff =64 cm(-1) ...
June 26, 2017: Angewandte Chemie
Feng Li, Stephanie H Carpenter, Robert F Higgins, Mark G Hitt, William W Brennessel, Maryline G Ferrier, Samantha K Cary, Juan S Lezama-Pacheco, Joshua T Wright, Benjamin W Stein, Matthew P Shores, Michael L Neidig, Stosh A Kozimor, Ellen M Matson
Inspired by the multielectron redox chemistry achieved using conventional organic-based redox-active ligands, we have characterized a series of iron-functionalized polyoxovanadate-alkoxide clusters in which the metal oxide scaffold functions as a three-dimensional, electron-deficient metalloligand. Four heterometallic clusters were prepared through sequential reduction, demonstrating that the metal oxide scaffold is capable of storing up to four electrons. These reduced products were characterized by cyclic voltammetry, IR, electronic absorption, and (1)H NMR spectroscopies...
May 26, 2017: Inorganic Chemistry
Min Wang, Yushi Yang, Xiaobo Liu, Zonghua Pu, Zongkui Kou, Peipei Zhu, Shichun Mu
Fe-N-C series catalysts are always attractive for their high catalytic activity towards the oxygen reduction reaction (ORR). However, they usually consist of various components such as iron nitrides, metallic iron, iron carbides, N-doped carbon and Fe-N4 moieties, leading to controversial contributions of these components to the catalysis of the ORR, especially iron nitrides. In this work, to investigate the function of iron nitrides, FexN nanoparticles (NPs) embedded in mesoporous N-doped carbon without Fe-N4 moieties are designed and constructed by a simple histidine-assisted method...
June 8, 2017: Nanoscale
William P Clark, Simon Steinberg, Richard Dronskowski, Catherine McCammon, Ilya Kupenko, Maxim Bykov, Leonid Dubrovinsky, Lev G Akselrud, Ulrich Schwarz, Rainer Niewa
The combination of laser-heated diamond anvil cells and synchrotron Mössbauer source spectroscopy were used to investigate high-temperature high-pressure chemical reactions of iron and iron nitride Fe2 N with nitrogen. At pressures between 10 and 45 GPa, significant magnetic hyperfine splitting indicated compound formation after annealing at 1300 K. Subsequent in situ X-ray diffraction reveals a new modification of FeN with NiAs-type crystal structure, as also rationalized by first-principles total-energy and chemical-bonding studies...
June 12, 2017: Angewandte Chemie
Wasinee Phonsri, David S Macedo, Casey G Davies, Guy N L Jameson, Boujemaa Moubaraki, Keith S Murray
The influence of the halogen substituent on the qsal moiety of iron(iii) heteroleptic compounds with the formulae [Fe(qsal-X)(thsa)]·nMeCN, where qsal-X(-) = X-substituted quinolylsalicylaldimine; thsa(2-) = thiosemicarbazone-salicylaldiminate; X = F; n = 2.5, 1·2.5MeCN and X = Cl 2, Br 3 and I 4, n = 1 (labelled 2·MeCN, 3·MeCN and 4·MeCN, respectively) has been systematically investigated. Magnetic studies on solid samples show incomplete spin crossover in 1-3 which can be related to MeCN solvent loss...
May 30, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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