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Takahiko Kojima, Fumiya Ogishima, Takahisa Nishibu, Hiroaki Kotani, Tomoya Ishizuka, Toshihiro Okajima, Shunsuke Nozawa, Yoshihito Shiota, Kazunari Yoshizawa, Hiroyoshi Ohtsu, Masaki Kawano, Takuya Shiga, Hiroki Oshio
An iron(III) complex having a dibenzotetraethyltetraamido macrocyclic ligand (DTTM4- ), (NEt4 )2 [FeIII (DTTM)Cl] (1), was synthesized and characterized by crystallographic, spectroscopic, and electrochemical methods. Complex 1 has a square-pyramidal structure in the S =3 /2 spin state. The complex exhibited two reversible redox waves at +0.36 and +0.68 V (vs SCE) in the cyclic voltammogram measured in CH2 Cl2 at room temperature. The stepwise oxidation of 1 using chemical oxidants allowed us to observe clear and distinct spectral changes with distinct isosbestic points for each step, in which oxidation occurred at the phenylenediamido moiety rather than the iron center...
March 16, 2018: Inorganic Chemistry
Thomas M Pangia, Casey G Davies, Joshua R Prendergast, Jesse B Gordon, Maxime A Siegler, Guy N L Jameson, David P Goldberg
A nonheme iron(III) terminal methoxide complex, [FeIII (N3PyO2Ph )(OCH3 )]ClO4 , was synthesized. Reaction of this complex with the triphenylmethyl radical (Ph3 C• ) leads to formation of Ph3 COCH3 and the one-electron-reduced iron(II) center, as seen by UV-vis, EPR,1 H NMR, and Mössbauer spectroscopy. These results indicate that homolytic Fe-O bond cleavage occurs together with C-O bond formation, providing a direct observation of the "radical rebound" process proposed for both biological and synthetic nonheme iron centers...
March 14, 2018: Journal of the American Chemical Society
Jinglu Xu, Yang Yu, Kang Ding, Zhiying Liu, Lei Wang, Yanhua Xu
This study converted sewage sludge into a carbonaceous catalyst via pyrolysis and employed it in the ozonation of hydroquinone. The catalyst was characterized by Mössbauer spectroscopy, X-ray photoelectron spectroscopy, temperature programmed desorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Intermediate products were detected by gas chromatography-mass spectrometry, and a pathway for hydroquinone degradation was proposed...
March 2018: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Chen Zhang, Jia Song, Jia Zhang, Jingyi Zhang, Juanjuan Xing, Dongli Hu, Yongqiang Peng, Jizhi Zhou, Qiang Liu, Hui Gu, Guangren Qian
Industrial sludge has been shown to be a valuable source of transition metals and to be effective in NO reduction. This research has further revealed a characteristic texture (O-Me-C) that promotes effective NO reduction and supports its existence in a sludge-derived catalyst. HRTEM exhibited that the O-Me-C consisted of multi-metal-oxide core, carbon shell and their binding interfaces. Furthermore, pre-treatment of the sludge with aromatic containing wastewater produced a more active texture (O-Me-GOL ), characterized by the presence of multi-metal-oxide core, graphene oxide-like carbon and highly active interfaces (EELS, Mössbauer and Raman)...
March 8, 2018: Science of the Total Environment
Johanna K Jochum, Michael Lorenz, Haraldur P Gunnlaugsson, Christian Patzig, Thomas Höche, Marius Grundmann, André Vantomme, Kristiaan Temst, Margriet J Van Bael, Vera Lazenka
Correlations were established between the hyperfine field distribution around the Fe atoms, the multiferroic properties, and the high magnetoelectric coefficient in BaTiO3 -BiFeO3 multilayer stacks with variable BiFeO3 single layer thickness, down to 5 nm. Of key importance in this study was the deposition of57 Fe - enriched BiFeO3 , which enhances the sensitivity of conversion electron Mössbauer spectroscopy by orders of magnitude. The magnetoelectric coefficient αME reaches a maximum of 60.2 V cm-1 Oe-1 at 300 K and at a DC bias field of 2 Tesla for a sample of 15 × (10 nm BaTiO3 -5 nm BiFeO3 ) and is one of the highest values reported so far...
March 9, 2018: Nanoscale
Stefan Schaub, Andreas Miska, Jonathan Becker, Stefan Zahn, Doreen Mollenhauer, Sakshath Sadashivaiah, Volker Schünemann, Siegfried Schindler
The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclo-tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H2O)(tmc)Fe=O)](OTf)2 could be prepared. This complex is important in regard to a better understanding of the reactivity of Fe(IV) oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of = 0.19 mms-1 and a quadrupole splitting EQ = 1.38 mms-1 confirming the high valent Fe(IV) state...
March 9, 2018: Angewandte Chemie
Mohammed A Albedah, Farshad Nejadsattari, Zbigniew M Stadnik, Yi Liu, Guanghan Cao
The results of ab-initio hyperfine-interaction parameters calculations, and of X-ray diffraction and <sup>57</sup>Fe and <sup>151</sup>Eu Mössbauer spectroscopy study of the new 35 K superconductor CsEuFe<sub>4</sub>As<sub>4</sub> are reported. The superconductor crystallizes in the tetragonal space group <i>P</i>4/<i>nmm</i> with the lattice parameters a = 3...
March 7, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Mei-Ling Chen, Zhi-Wen Gao, Xue-Min Chen, Shu-Chao Pang, Yi Zhang
Magnetic graphene-based hybrids are being increasing recognized as an effective nanotheranostic agent in biomedicine. Conventional technologies for their synthesis have drawbacks not only from a synthetic standpoint, mainly requiring high temperatures and multi-step processes, but also from a biological perspective, chemical precursors or surfactants involved in the chemical process are toxic to cells. Herein, we report a novel approach for one-step fabricating magnetic graphene hybrid nanocomposites based on laser irradiation of an Fe target in GO-PEG aqueous solution at room temperature without using any other chemical reagent...
May 15, 2018: Talanta
Marina A Andreeva, Roman A Baulin, Aleksandr I Chumakov, Rudolf Rüffer, Gennadii V Smirnov, Yurii A Babanov, Denis I Devyaterikov, Mikhail A Milyaev, Dmitrii A Ponomarev, Lazar N Romashev, Vladimir V Ustinov
Mössbauer reflectivity spectra and nuclear resonance reflectivity (NRR) curves have been measured using the Synchrotron Mössbauer Source (SMS) for a [57 Fe/Cr]30 periodic multilayer, characterized by the antiferromagnetic interlayer coupling between adjacent57 Fe layers. Specific features of the Mössbauer reflectivity spectra measured with π-polarized radiation of the SMS near the critical angle and at the `magnetic' maximum on the NRR curve are analyzed. The variation of the ratio of lines in the Mössbauer reflectivity spectra and the change of the intensity of the `magnetic' maximum under an applied external field has been used to reveal the transformation of the magnetic alignment in the investigated multilayer...
March 1, 2018: Journal of Synchrotron Radiation
Samuel D Oberdick, Ahmed Abdelgawad, Carlos Moya, Samaneh Mesbahi-Vasey, Demie Kepaptsoglou, Vlado K Lazarov, Richard F L Evans, Daniel Meilak, Elizabeth Skoropata, Johan van Lierop, Ian Hunt-Isaak, Hillary Pan, Yumi Ijiri, Kathryn L Krycka, Julie A Borchers, Sara A Majetich
Magnetic nanoparticles (MNPs) have become increasingly important in biomedical applications like magnetic imaging and hyperthermia based cancer treatment. Understanding their magnetic spin configurations is important for optimizing these applications. The measured magnetization of MNPs can be significantly lower than bulk counterparts, often due to canted spins. This has previously been presumed to be a surface effect, where reduced exchange allows spins closest to the nanoparticle surface to deviate locally from collinear structures...
February 21, 2018: Scientific Reports
Lydia Pohl, Angelika Kölbl, Florian Werner, Carsten W Mueller, Carmen Höschen, Werner Häusler, Ingrid Kögel-Knabner
RATIONALE: Al-substituted goethite is ubiquitous in soils and sediments. The extent of Al substitution affects the physicochemical properties of the mineral and influences its macroscale properties. Bulk analysis only provides total Al/Fe ratios without providing information with respect to the Al-substitution of single minerals. Here, we demonstrate that Nanoscale secondary ion mass spectrometry (NanoSIMS) enables the precise determination of Al-content in single minerals, while simultaneously visualising the variation of the Al/Fe ratio...
February 21, 2018: Rapid Communications in Mass Spectrometry: RCM
Ruixi Fan, Joan Serrano-Plana, Williamson N Oloo, Apparao Draksharapu, Estefania Delgado-Pinar, Anna Company, Vlad Martin-Diaconescu, Margarida Borrell, Julio Lloret-Fillol, Enrique García-España, Yisong Guo, Emile L Bominaar, Lawrence Que, Miquel Costas, Eckard Münck
The reaction of [(PyNMe3 )FeII (CF3 SO3 )2 ], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490-nm chromophore associated with an S = ½ EPR signal having g-values at 2.07, 2.01, and 1.94 . This species was shown to be in a fast equilibrium with a second S = ½ species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by Mössbauer spectroscopy...
February 20, 2018: Journal of the American Chemical Society
Matteo Ardini, Barry D Howes, Annarita Fiorillo, Elisabetta Falvo, Silvia Sottini, Donella Rovai, Marco Lantieri, Andrea Ilari, Dante Gatteschi, Gabriele Spina, Emilia Chiancone, Simonetta Stefanini, Maria Fittipaldi
Ferritins are ubiquitous and conserved proteins endowed with enzymatic ferroxidase activity, that oxidize Fe(II) ions at the dimetal ferroxidase centre to form a mineralized Fe(III) oxide core deposited within the apo-protein shell. Herein, the in vitro formation of a heterodimetal cofactor constituted by Fe and Mn ions has been investigated in human H ferritin (hHFt). Namely, Mn and Fe binding at the hHFt ferroxidase centre and its effects on Fe(II) oxidation have been investigated by UV-Vis ferroxidation kinetics, fluorimetric titrations, multifrequency EPR, and preliminary Mössbauer spectroscopy...
February 9, 2018: Journal of Inorganic Biochemistry
A Scrimshire, A Lobera, A M T Bell, A H Jones, I Sterianou, S D Forder, P A Bingham
Lanthanide orthoferrites have wide-ranging industrial uses including solar, catalytic and electronic applications. Here a series of lanthanide orthoferrite perovskites, LnFeO 3 (Ln = La; Nd; Sm; Eu; Gd), prepared through a standard stoichiometric wet ball milling route using oxide precursors, has been studied. Characterisation through x-ray diffraction and x-ray fluorescence confirmed the synthesis of phase-pure or near-pure LnFeO 3 compounds. 57 Fe Mössbauer spectroscopy was performed over a temperature range of 10 K-293 K to observe hyperfine structure and to enable calculation of the recoil-free fraction and Debye temperature (θ D ) of each orthoferrite...
February 16, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Lianke Wang, Matija Zlatar, Filip Vlahovic, Serhiy Demeshko, Christian Philouze, Florian Molton, Franc Meyer, Carole Duboc, Maja Gruden, Marcello Gennari
The complexes [FeLN2S2X] (where LN2S2 = 2,2'-(2,2'-bipryridine-6,6'-diyl)bis(1,1'-diphenylethanethiolate) and X = Cl, Br and I), characterized crystallographically earlier and here (Fe(L)Br), reveal a square pyramidal coordinated FeIII ion. Unusually, all three complexes have intermediate spin ground states. Susceptibility measurements, powder cw X- and Q-band EPR spectra, zero-field powder Mössbauer spectra and DFT calculations show that all complexes display distinct magnetic anisotropy.
February 15, 2018: Chemistry: a European Journal
Biserka Gržeta, Dirk Lützenkirchen-Hecht, Martina Vrankić, Sanja Bosnar, Ankica Šarić, Masashi Takahashi, Dimitar Petrov, Marijan Bišćan
Powder samples of pure BaAl2O4 and doped with 4.9 atom % Eu in relation to Ba were prepared by a hydrothermal route. The samples were characterized by X-ray diffraction, 151Eu Mössbauer spectroscopy, synchrotron-based X-ray absorption spectroscopy at the Ba L3- and Eu L3-edges, and photoluminescence measurements. Diffraction lines were broadened, indicating that the samples were nanocrystallline. The samples possessed a hexagonal crystal structure, space group P63. 151Eu Mössbauer spectroscopy revealed the presence of Eu in the 3+ oxidation state...
February 8, 2018: Inorganic Chemistry
Chao Shan, Jiajia Chen, Zhe Yang, Huichao Jia, Xiaohong Guan, Weiming Zhang, Bingcai Pan
Although the removal of Se(VI) from water by using zero-valent iron (ZVI) is a promising method, passivation of ZVI severely inhibits its performance. To overcome such issue, we proposed an efficient technique to enhance Se(VI) removal via pre-corrosion of ZVI with H2O2/HCl in a short time (15 min). The resultant pcZVI suspension was weakly acidic (pH 4.56) and contained abundant aqueous Fe2+. 57Fe Mössbauer spectroscopy showed that pcZVI mainly consisted of Fe0 (66.2%), hydrated ferric oxide (26.3%), and Fe3O4 (7...
January 19, 2018: Water Research
Ian Barr, Troy A Stich, Anthony S Gizzi, Tyler L Grove, Jeffrey B Bonanno, John A Latham, Tyler Chung, Carrie M Wilmot, R David Britt, Steven C Almo, Judith P Klinman
The Radical SAM (RS) enzyme PqqE catalyzes the first step in the biosynthesis of the bacterial cofactor pyrroloquinoline quinone, forming a new carbon-carbon bond between two side chains within the ribosomally synthesized peptide substrate PqqA. In addition to the active site RS 4Fe-4S cluster, PqqE is predicted to have two auxiliary Fe-S clusters, like the other members of the SPASM domain family. Here we identify these sites and examine their structure using a combination of X-ray crystallography and Mössbauer and electron paramagnetic resonance (EPR) spectroscopies...
February 6, 2018: Biochemistry
Stefanie Dehnen, Niklas Rinn, Lukas Guggolz, Jurek Lange, Theresa Block, Sangam Chatterjee, Rainer Pöttgen
Reactions of the organotin selenide chloride clusters [(R1SnIV)3Se4Cl] (A, R1 = CMe2CH2C(O)Me) or [(R1SnIV)4Se6] (B) with [Cu(PPh3)3 xClx] yields cluster compounds with different inorganic, mixed-valence core structures: [Cu4SnIISnIV6Se12], [Cu2SnII2SnIV4Se8Cl2], [Cu2SnIISnIV4Se8], [Cu2SnII2SnIV2Se4Cl4], and [Cu2SnIV2Se4]. Five of the compounds, namely [(CuPPh3)2{(R1SnIV)2Se4}] (1), [(CuPPh3)2SnII{(R2SnIV)2Se4}2] (2), [(CuPPh3)2(SnIICl)2{(RSnIV)2Se4}2] (3) [(CuPPh3)2(SnIICu2){(R1SnIV)2Se4}3] (4), and [Cu(CuPPh3)(SnIICu2){(R1SnIV)2Se4}3] (5) are structurally closely related...
February 6, 2018: Chemistry: a European Journal
Luiza Notini, Drew E Latta, Anke Neumann, Carolyn I Pearce, Michel Sassi, Alpha T N'Diaye, Kevin M Rosso, Michelle M Scherer
Despite substantial experimental evidence for Fe(II)-Fe(III) oxide electron transfer, computational chemistry calculations suggest that oxidation of sorbed Fe(II) by goethite is kinetically inhibited on structurally perfect surfaces. We used a combination of 57Fe Mössbauer spectroscopy, synchrotron X-ray absorption and magnetic circular dichroism (XAS/XMCD) spectroscopies to investigate whether Fe(II)-goethite electron transfer is influenced by defects. Specifically, Fe L-edge and O K-edge XAS indicates that the outermost few Angstroms of goethite synthesized by low temperature Fe(III) hydrolysis is iron deficient relative to oxygen, suggesting the presence of defects from Fe vacancies...
February 6, 2018: Environmental Science & Technology
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