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In the present work, a combination of various techniques is utilized for the study of nano-mineralogy and -geochemistry of high-grade karst-type bauxite (Al-rich and Fe-depleted samples; Al2O3 ca. 80 wt.%) from the Parnassos-Ghiona mines located in Greece. Initial characterization using PXRD and electron microscopy in microscale and mesoscale (SEM-EDS including STEM mode), proved the presence of “Fe-Cr-Ti-containing diaspore”, anatase and minor rutile. The study by means of 57Fe Mössbauer spectroscopy, in correlation with magnetic susceptibility measurements and, complemented, with Synchrotron-based spectroscopies at the microscale (SR micro-XRF and micro-XANES/-EXAFS), indicated that Fe3+, in contrast to [6]Cr3+, is not exclusively a component of the diaspore structure. While Cr3 + substitutes Al3 + in octahedral sites of diaspore ([6]Cr3+ ↔ [6]Al3+), the electron microscopy in nanoscale (TEM-EDS & EELS) revealed that Fe exists in the form of peculiar Fe3+-bearing nanominerals (most likely maghemite-type phases) between 25 and 45 nm in size, in addition to the Fe3+ ions substituting Al3+ in the diaspore structure. Moreover, it was proven that TiO2 polymorph mineral nanoparticles, particularly rounded anatase mesocrystals and nanocrystals and individual needle-shaped rutiles, are dispersed into the diaspore matrix. Thus, diaspore in the studied bauxite concerns -in fact- a distinct Fe3+-Cr3+-AlOOH low-T authigenic phase, demonstrated for the first time in literature. On the other hand, the observed TiO2 mineral nanoparticles (formed, together with diaspore, during diagenesis) and Fe nanominerals (formed during epigenesis) were hitherto unknown not only for the allochthonous karst-type bauxite deposits of Greece, but also for the overall bauxite deposits, worldwide. © 2016 Elsevier B.V.

J Hazard Mater

Journal of Nanoparticle Research

Magnetic Fe2O3/carbon hybrids were prepared in a two-step process. First, acetic acid vapor interacted with iron cations dispersed on the surface of a nanocasted ordered mesoporous carbon (CMK-3). In the second step, the primarily created iron acetate species underwent pyrolysis and transformed to magnetic iron oxide nanoparticles. X-ray diffraction, Fourier-transform infrared, and Raman spectroscopies were used for the chemical and structural characterization of the hybrids, while surface area measurements, thermal analysis, and transmission electron microscopy were employed to determine their physical, surface, and textural properties. These results revealed the preservation of the host carbon structure, which was homogenously and controllably loaded (up to 27 wt %) with nanosized (ca. 20 nm) iron oxides inside the mesoporous system. Mossbauer spectroscopy and magnetic measurements at low temperatures confirmed the formation of gamma-Fe2O3 nanoparticles exhibiting superparamagnetic behavior. The kinetic studies showed a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these magnetic mesoporous hybrids and a considerably increased adsorption capacity per unit mass of sorbent in comparison to that of pristine CMK-3 carbon. The results also indicate highly pH-dependent sorption efficiency of the hybrids, whereas their kinetics was described by a pseudo-second-order kinetic model. Taking into account the simplicity of the synthetic procedure and possibility of magnetic separation of hybrids with immobilized pollutant, the developed mesoporous nanomaterials have quite real potential for applications in water treatment technologies. Langmuir

A 3 to 1 Ni/Si antiferromagnetic layered phyllosilicate, Ni3Si(C3H6NH3)F0.65O1.9(OH)(4.45)(CH3COO)(1.1)center dot xH(2)O, was modified with K-4[Fe(CN)(6)]center dot 3H(2)O. This compound retained its ordering as proved by X-ray diffraction, while infrared spectra revealed the presence of [Fe(CN)(6)](4-) groups and X-ray photoelectron spectroscopy showed that the latter partially substitute the acetate groups. Both the parent and the modified compound are canted antiferromagnets with an anisotropy perpendicular to the layers and show spin-flop transitions. For the parent compound, a single step spin-flop occurs at H = 24 kOe. The modified compound shows increased antiferromagnetic canting and a two-step transition (H-1 = 24 kOe, H-2 = 48 kOe). These results testify to the existence of competing interactions that depend sensitively on the grafted species. Langmuir

Four new organotin(IV) complexes of bis-(2,6-di-tert-butylphenol)tin(IV) dichloride [(tert-Bu-)(2)(HO-Ph)](2)SnCl2 (1) with the heterocyclic thioamides 2-mercapto-pyrimidine (PMTH), 2-mercapto-4-methyl-pyrimidine (MPMTH), 2-mercapto-pyridine (PYTH) and 2-mercapto-benzothiazole (MBZTH), of formulae {[(tert-Bu-)(2)(HO-Ph)](2)Sn(PMT)(2)}(2), {[(tert-Bu-)(2)(HO-Ph)](2)Sn(MPMT)(2)} (3), {[(tert-Bu-)(2)(HO-Ph)](2)SnCl(PYT)} (4) and {[(tert-Bu-)(2)(HO-Ph)](2)SnCl(MBZT)} (5), have been ;synthesized and characterized by elemental analysis, H-1-, C-13-, Sn-119-NMR, EPR, FT-IR, Raman and Mossbauer spectroscopic techniques. The crystal and molecular structures of compounds 1-5 have been determined by X-ray diffraction. The geometries around the metal center adopted in complexes 1-5 varied between tetrahedral in 1, trigonal bipyramidal in 3, 4, 5 and distorted octahedral in 2. Two carbon atoms from aryl groups and two chlorine atoms form a distorted tetrahedron in the case of 1. Two carbon, two sulfur and two nitrogen atoms from thione ligands form a distorted octahedral geometry around tin (IV) with trans-C-2, cis-N-2, cis-S-2-configurations in 2. However, in the case of 4 and 5 complexes two carbon, one sulfur, one nitrogen and one chloride atom form a distorted trigonal bipyramidal arrangement. Finally, in the case of 3 the trigonal bipyramidal geometry is achieved by two carbon, two sulfur and one nitrogen atom in a unique coordination mode of thioamides toward the tin(IV) cation. Compounds 1-5 were tested for their in vitro cytotoxicity against the human breast adenocarcinoma (MCF-7) cell line. Compound 3 exhibits strong cytotoxic activity against MCF-7 cells (IC50 = 0.58 +/- 0.1 mu M). Dalton Transactions

Air-stable bimetallic spherically shaped Fe-Ni and Fe-Co magnetic nanoparticles (MNPs), having an average size of 15 nm and core-shell structure, were synthesized by a simple wet chemical method under ambient conditions. For the first time, sodium borohydride reduction method, commonly applied for the syntheses of metal nanoparticles, was used for the preparation of well-defined Fe-Ni and Fe- Co nanoalloys, avoiding exploitation of any organic solvent. This approach allows a large scale production of nanoparticles specifically stabilized by an iron oxyhydroxide shell without a need of secondary functionalization. Transmission electron microscopy, X-ray powder diffraction, X-ray fluorescence, magnetization, and M?ssbauer data demonstrate a core- shell nature of the as-synthesized nanoparticles. The nanoparticle core is of metallic origin and is inhomogeneous at the atomic level, consisting of iron-rich and iron-poor alloy phases. The composition of the shell is close to the ferrihydrite and its role lies in prevention of oxidation-induced degradation of nanoparticle properties. The core is ferromagnetic at and below room temperature, experiencing superparamagnetic relaxation effects due to a reduced size of nanoparticles, whereas the shell is completely superparamagnetic at 300 K and magnetically orders below?25 K. Both developed types of magnetic nanoalloys exhibit a strong magnetic response under applied magnetic fields with a high magnetization values achievable at relatively low applied magnetic fields. Beside this, the highly biocompatible chemical composition of the nanoparticle shell and ability of its chemical modification by substitution or addition of other ions or molecules further empower the application potential of these MNPs, especially in the field of biomedicine. © Springer Science+Business Media B.V. 2012. Journal of Nanoparticle Research

The structural and magnetic properties and spin dynamics of dextran coated and uncoated γ-Fe 2O 3 (maghemite) nanoparticles have been investigated using high resolution transmission electron microscopy (HRTEM), 57Fe nuclear magnetic resonance (NMR), M?ssbauer spectroscopy and dc magnetization measurements. The HRTEM observations indicated a well-crystallized system of ellipsoid-shaped nanoparticles, with an average size of 10nm. The combined M?ssbauer and magnetic study suggested the existence of significant interparticle interactions not only in the uncoated but also in the dextran coated nanoparticle assemblies. The zero-field NMR spectra of the nanoparticles at low temperatures are very similar to those of the bulk material, indicating the same hyperfine field values at saturation in accord with the performed M?ssbauer measurements. The T 2 NMR spinspin relaxation time of the nanoparticles has also been measured as a function of temperature and found to be two orders of magnitude shorter than that of the bulk material. It is shown that the thermal fluctuations in the longitudinal magnetization of the nanoparticles in the low temperature limit may account for the shortening and the temperature dependence of the T 2 relaxation time. Thus, the low temperature NMR results are in accord with the mechanism of collective magnetic excitations, due to the precession of the magnetization around the easy direction of the magnetization at an energy minimum, a mechanism originally proposed to interpret M?ssbauer experiments in magnetic nanoparticles. The effect of the surface spins on the NMR relaxation mechanisms is also discussed. © 2012 IOP Publishing Ltd. Journal of Physics Condensed Matter

Four new organotin(IV) complexes of bis-(2,6-di-tert-butylphenol)tin(IV) dichloride [(tert-Bu-)2(HO-Ph)]2SnCl2 (1) with the heterocyclic thioamides 2-mercapto-pyrimidine (PMTH), 2-mercapto-4-methyl-pyrimidine (MPMTH), 2-mercapto-pyridine (PYTH) and 2-mercapto-benzothiazole (MBZTH), of formulae {[(tert-Bu-)2(HO-Ph)]2Sn(PMT)2} (2), {[(tert-Bu-)2(HO-Ph)]2Sn(MPMT)2} (3), {[(tert-Bu-)2(HO-Ph)]2SnCl(PYT)} (4) and {[(tert-Bu-)2(HO-Ph)]2SnCl(MBZT)} (5), have been synthesized and characterized by elemental analysis, 1H-, 13C-, 119Sn-NMR, EPR, FT-IR, Raman and Mössbauer spectroscopic techniques. The crystal and molecular structures of compounds 1-5 have been determined by X-ray diffraction. The geometries around the metal center adopted in complexes 1-5 varied between tetrahedral in 1, trigonal bipyramidal in 3, 4, 5 and distorted octahedral in 2. Two carbon atoms from aryl groups and two chlorine atoms form a distorted tetrahedron in the case of 1. Two carbon, two sulfur and two nitrogen atoms from thione ligands form a distorted octahedral geometry around tin(IV) with trans-C2, cis-N2, cis-S2-configurations in 2. However, in the case of 4 and 5 complexes two carbon, one sulfur, one nitrogen and one chloride atom form a distorted trigonal bipyramidal arrangement. Finally, in the case of 3 the trigonal bipyramidal geometry is achieved by two carbon, two sulfur and one nitrogen atom in a unique coordination mode of thioamides toward the tin(IV) cation. Compounds 1-5 were tested for their in vitro cytotoxicity against the human breast adenocarcinoma (MCF-7) cell line. Compound 3 exhibits strong cytotoxic activity against MCF-7 cells (IC50 = 0.58 ± 0.1 μM). Dalton Transactions

The reaction of di-iodine with N-methyl-2-mercapto-benzothiazole (NMBZT) in the presence of ferric tetra-phenyl-porphyrin chloride (FeTPPCl) in 6 : 3 : 1 (I(2) : thioamide : FeTPPCl) molar ratio yields a mixture of products consisting of the iodonium {[(NMBZT)(2)I](+)center dot[(I(7))(-)]}(n) salt, 1, and the FeTPPCl complex, 2. The compounds were characterized by X-ray diffraction analysis. The crystal structure of 1 was identical to the one already published, while of compound 2 at 294(1) K re-evaluates previous work on it. The inhibition activity of the thioamide ligands (N-methyl-2-mercapto-benzothiazole (NMBZT), 2-mercapto-benzothiazole (MBZT), 5-chloro-2-mercapto benzothiazole (CMBZT), 2-mercaptothiazolidine (MTZT), 2-mercaptopyridine (PySH), thiourea (TU), 1,3-bis(3-pyridyl-methyl)-2-thiourea (PyTU), 2-mercapto-3,4,5,6-tetrahydropyrimidine (THP), 2-mercaptopyrimidine (PmSH), 6-propyl-2-thiouracil (PTU), 6-methyl-2-thiouracil (MTU), di-thiouracil-2,4 (DTUC), 2-mercapto-4-methyl-pyrimidine hydro chloride (MPmCl), methimazole (MMI), 2-mercapto-benzimidazole (BZIM), 5-nitro-2-mercapto-benzimidazole (NiMBZIM), 5-methyl-2-mercapto-benzimidazole (MBZIM), 2-hydroxy-pyrimidine (PmOH), 2-hydroxypyridine (PyOH)) against the catalytic oxidation of iodides by H(2)O(2) in the presence of FeTPPCl (a model of the active site of Thyroid Peroxidase (TPO)) was measured as a result of the yield of I(3)(-) resulting from the oxidation of I(-) and was also evaluated theoretically using electronic structure calculation methods (DFT). The compounds exhibiting high and intermediate degree of inhibition (between 27% and 17%) are MBZT, MMI, PySH, NMBZT, PmSH, MBZIM, NiBZIM and MTZT. The kinetic study of inhibition of lactoperoxidase (LPO) (a model of TPO) is based on the assessment of LPO activity in the presence of its inhibitors-the thioamide compounds. LPO activity can be assayed by measuring guaiacol (gua) peroxidation to tetraguaiacol in the presence of H(2)O(2). The results illustrated that the lowest IC(50) values (

The effect of magnetic annealing on the texture is investigated in a series of CoPt films of different thickness obtained by annealing of Co/Pt multilayers. Magnetic field is found to promote the (001) texture by selective (001) grain growth driven by the magnetic field and biaxial strain. A systematic correlation between in-plane biaxial strain and the degree of (001) texture is found only for the magnetically annealed samples. (C) 2011 American Institute of Physics. [doi:10.1063/1.3651380] Journal of Applied Physics

Nanocomposite thin films of Spinel Iron-Oxide and SiO2 have been prepared with sol-gel dip-coating technique involving the synthesis of a ferrofluid, which has been stabilized in absence of organic media and led to the formation of magnetic nanoparticles. Structural and morphological characteristics of the synthesized ferrofluid and the relevant derived nanocomposite films are reported, as determined from X-ray diffraction (XRD), Raman, Fourier-transform infrared, Mossbauer and Ultraviolet-visible experimental techniques. Scanning electron microscopy, atomic force and magnetic force microscopy results are also reported. The synthesized ferrofluid, composed of magnetic nanoparticles of an XRD estimated average size of 18 nm, exhibit Raman spectra characteristic of a maghemite phase. These ferromagnetic nanoparticles retained their nanostructure after being inserted into the as prepared films. After heat treatment under Ar atmosphere, the maghemite nanoparticles were transformed to non-stoichiometric magnetite, providing the final composite material with useful potential application characteristics. The calcined films reported here exhibit crack-free morphology, consisting of aggregated silica/magnetic nanoparticles, with a final average size of c.a. 100 nm, while the film roughness shows a maximum peak to peak of C.a. 10 nm. (C) 2011 Elsevier B.V. All rights reserved. Thin Solid Films

The reaction between 2-thiobarbituric acid (H(2)TBA), which was treated with an equimolar amount of potassium hydroxide, in a water with triphenytin chloride in methanol, results in the formation of the {[Ph3Sn(O-HTBA)]}(n) (1) complex. Crystals of the hydrated 1 with formula {[Ph3Sn(O-HTBA)]center dot 0.7(H2O)}(n) were growth from methanol/acetonitrile solution, of the white precipitation, filtered off, from the reaction. The crystal structure of complex 1 has been determined by X-ray diffraction at 120K. Complex 1 is polymeric. The geometry around the tin(IV) ions is trigonal bi-pyramidal with coordination to three C atoms from phenyl groups and one O atom from a de-protonated HTBA ligand. Complex 1 and the already known [(n-Bu)(3)Sn(O-HTBA)center dot H2O] (2) were evaluated for their in vitro cytotoxic activity (cell viability) against human cancer cell lines: HeLa (cervical), OAW-42 (ovarian), MCF-7 (breast, ER positive), MDA-MB-231 (breast, ER negative), A549 (lung), Caki-1 (renal) and additionally, the normal human lung cell line MRC-5 (normal human fetal lung fibroblast cells) and normal immortalized human mammary gland epithelial cell line MTSV17 with a Trypan Blue assay. Moreover complex I was evaluated for its in vitro cell growth proliferation activity against leiomyosarcoma cells (LMS), MCF-7 and MRC-5 cells with a Thiazolyl Blue Tetrazolium Bromide (MU) assay. The type of cell death caused by complexes 1 and 2 was also evaluated by use of flow cytometry assay. The results showed that these compounds mediate a strong cytotoxic response to normal and cancer cell lines tested through apoptosis and induce cell cycle arrest in S phase of the cell cycle, suggesting DNA intercalation (direct or indirect) with the complexes. Finally, the influence of these complexes 1 and 2 upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically and theoretically studied. (C) 2011 Elsevier Masson SAS. All rights reserved. Eur J Med Chem

A recently developed computer based 57Fe-119Sn M?ssbauer spectra fitting program is described. The program uses full Hamiltonian matrices to generate theoretical M?ssbauer spectral contributions with which fits the experimental data based on a least-squares minimization procedure. The user of the program can exploit its interactive user interface to built and modify on-the-fly a starting theoretical model of proposed contributions without the need to write or alter the initial M?ssbauer parameter values to or from any file. Changes in the M?ssbauer parameters values for the proposed model can be made on the screen and the theoretical contributions can be displayed during those changes in real time together with the experimental spectrum in order to give the user the ability to approximate with the best and fast way the desired solution before launching the minimization procedure. Single as well as multiple sub-component contributions with Gaussian-type spreading of quadrupole splitting/shift or hyperfine magnetic field values can be realized to fit transmission, conversion electron or X-ray M?ssbauer spectra of randomly or non-randomly oriented powder or single crystal samples. The program is currently written for 3/21/2 nuclear spin transitions but can be modified to include higher spins, as well as distributions of other types and of other M?ssbauer parameters values. © 2010 IOP Publishing Ltd. Journal of Physics: Conference Series

Single crystals of CaCr(0.84)Fe(3.16)As(3), a Cr substituted analog of CaFe(4)As(3), were grown from Sn flux and characterized with single crystal neutron diffraction. CaCr(0.84)Fe(3.16)As(3) crystallizes in the orthorhombic space group Pnma with a three-dimensional framework, where Fe, Cr, and As form a covalent channel-like network with Ca(2+) cations residing in the channels. CaCr(0.84)Fe(3.16)As(3) has a unit cell of a = 12.057(4) angstrom, b = 3.7374(13) angstrom, and c = 11.694(3) A, as determined by room temperature single crystal neutron diffraction (R(1) = 0.0747, wR(2) = 0.1825). Structural data was also collected at 10 K. The single crystal neutron data showed that Cr selectively occupies a particular metal site, Fe(4). The antiferromagnetic transition associated with spin density wave (SDW) in the parent compound is preserved and shifts from 96 to 103 K with the selective Cr doping. Mossbauer, magnetic, and electrical resistivity measurements are reported. Chemistry of Materials

A trinuclear iron(III) oxo-centered complex [Fe(3)(mu(3)-O)(3-OCH(3)-salnec)(3)]OH center dot 5H(2)O was synthesized and characterized as cluster containing the semi-cubane [Fe(3)(mu(3)-O)](7+) core. The central oxygen atom is bridging the three iron(111) ions, which form an equilateral triangle with an average edge of -3.00 angstrom as it was deduced from X-ray diffraction studies. The new tetradentate ligand 3-OCH(3)-salnecH(2) = 1-[1-hydroxy-2(9'-methyl-1,10'-phenanthrolin-2-yl)ethyl]-3-methoxyphenol-2, was generated "in situ" during the synthesis process as a product of the addition reaction between the starting ligands 2,9-dimethyl-phenanthroline(neoc) and 3-methoxy-salicylaldehyde(3-OCH(3)-saloH(2)), in the presence of sodium methoxide and Fe(3+). Variable-temperature magnetic measurements indicate antiferromagnetic exchange interactions between the iron(III) ions in the cluster. Additionally, spectroscopic (IR, UV/Vis, Mossbauer, EPR) and electrochemical studies (CV) are presented and discussed. Zeitschrift Fur Anorganische Und Allgemeine Chemie

The reaction of metal(II) nitrates with oxamide-N,N'-diacetic acid (HA) in aqueous media under mild conditions, leads to the formation of novel coordination polymers formulated as {[M(H(2)L)(H(2)O)(x)]. 2(H(2)O)}(n) where M = Co(II), x = 4 (1); Ni(II), x = 4 (2); Zn(II), x = 3 (3); Cd(II), x = 3 (4): Ca(II), x = 2 (5). Compounds 1-4 are 1D polymers with the ligand being doubly deprotonated and coordinated through the carboxylic edges. Compound 5 is a 2D polymer with the ligand utilizing all of the available oxygen atoms for coordination. In all cases extended hydrogen bonding leads to the formation of 3D supramolecular architectures. The structures are discussed in terms of topological description. The synthesized compounds were also characterized with spectroscopic techniques and their stability was checked with thermal studies. (C) 2009 Elsevier Ltd. All rights reserved. Polyhedron

Mixed oxides of the general formula La(0.8)Sr(0.2)FeO(3-x) were prepared by ceramic and surfactant methods and tested towards the NO/H(2)/O(2) and NO/CH(4)/O(2) lean-deNO(x) reactions in the 200-450 degrees C range. The materials were characterized for their bulk and surface composition by XRD, Mossbauer and XPS techniques. The main crystal phases detected were perovskites LaFeO(3) and SrFeO(3-x), and alpha-Fe(2)O(3). The Mossbauer technique allowed the precise determination of the composition of Fe-containing phases in the solids prepared by both the ceramic and surfactant methods. Significant differences in the composition of the phases and the surface chemical states of Fe, Sr and La were revealed among the two solid compositions. For the CH(4) lean-deNO(x) reaction at 350 degrees C, the La(0.8)Sr(0.2)FeO(3-x) solid composition (LSF-2) prepared by the surfactant method exhibited an increase by 50% in the rate of NO conversion and by 30% in the rate of N(2) formation (per gram basis) as compared to the solid prepared by the ceramic method (LSF-1). An opposite relative catalytic activity behavior was observed for the two solids when tested towards the H(2) lean-deNO(x) reaction. At 375 degrees C (maximum activity observed) the solid prepared by the ceramic method (LSF-1) exhibited an increase by 83% in the rate of N(2) formation as compared to the solid prepared by the surfactant method (LSF-2). It is suggested that the mobility of surface lattice oxygen, the concentration of oxygen vacant sites, and the mixed valences of metal cations present in the La(0.8)Sr(0.2)FeO(3-x) solid all influenced by the preparation method used are the main parameters that largely influenced the catalytic behavior observed over the LSF-1 and LSF-2 solids. (C) 2009 Elsevier B.V. All rights reserved. Applied Catalysis B-Environmental

We present the synthesis and characterization of a novel metal-organic molecular solid using the ligand 4,8-disulfonaphthalene-2,6-dicarboxylic acid. The solid features a sulfonated, isolated supertetrahedra, [Fe(16)O(4)(SO(4))(12)(L2)(6)], built from mixed-valence [Fe(3)(3+)Fe(2+)(mu(3)-O)(mu(3)-SO(4))(3)(-CO(2))(3)] clusters. Inorg Chem

Organotin(IV) complexes with o- or p-hydroxybenzoic acids (o-H(2)BZA or p-H(2)BZA) of formulae [R(2)Sn(HL)(2)] (where H(2)L = o-H(2)BZA and R = Me- (1), n-Bu- (2)); [R(3)Sn(HL)] (where H(2)L = o-H(2)BZA and R = n-Bu- (3), Ph- (4) or H(2)L = p-H(2)BZA and R = n-Bu- (5), Ph- (6)) were synthesized by reacting a methanolic solution of di- and triorganotin(IV) compounds with an aqueous solution of the ligand (o-H(2)BZA or p-H(2)BZA) containing equimolar amounts of potassium hydroxide. The complexes were characterized by elemental analysis, FT-IR, Far-IR, TGA-DTA, FT-Raman, Mossbauer spectroscopy, (1)H, (119)Sn-NMR, UV/Vis spectroscopy, and Mass spectroscopy. The X-ray crystal structures of complexes 1 and 2 have also been determined. Finally, the influence of these complexes 1-6 upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically studied and the results showed that triorganotin(IV) complex 6 has the lowest IC(50) value. Also complexes 1-6 were studied for their in vitro cytotoxicity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, and the results showed that the complexes have high activity against these cell lines with triphenyltin((IV) complex 4 to be the most active one. Bioinorg Chem Appl

Multiwalled carbon nanotubes (MWCNTs) were used as nanotemplates for the dispersion and stabilization of FePt nanoparticles (NPs). Pre-formed capped FePt NPs were connected to the MWCNTs external surface via covalent binding through organic linkers. Free FePt NPs and MWCNTs-FePt hybrids were annealed in vacuum at 700 °C in order to achieve the L10 ordering of the FePt phase. Both as prepared and annealed samples were characterized and studied using a combination of experimental techniques, such as Raman and Mössbauer spectroscopies, powder X-ray Diffraction (XRD), magnetization and transmittion electron microscopy (TEM) measurements. TEM measurements of the hybrid sample before annealing show that a fine dispersion of NPs along the MWCNTs surface is achieved, while a certain amount of free particles attached to each other in well connected dense assemblies of periodical or non-periodical particle arrangements is also observed. XRD measurements reveal that the FePt phase has the face-centered cubic (fcc) disordered crystal structure in the as prepared samples, which is transformed to the face-centered tetragonal (fct) L10 ordered crystal structure after annealing. An increase in the average particle size is observed after annealing, which is higher for the free NPs sample. Superparamagnetic phenomena due to the small FePt particle size are observed in the Mössbauer spectra of the as prepared samples. Mössbauer and magnetization measurements of the MWCNTs-FePt hybrids sample reveal that the part of the FePt particles attached to the MWCNTs surface shows superparamagnetic phenomena at RT even after the annealing process. The hard magnetic L10 phase characteristics are evident in the magnetization measurements of both samples after annealing, with the coercivity of the hybrid sample over-scaling that of the free NPs sample by a factor of 1.25.

The reaction of K(2)Sn(2)Q(5) (Q = S, Se, Te) with stoichiometric amounts of alkyl-ammonium bromides R(4)NBr (R = methyl or ethyl) in ethylenediamine (en) afforded the corresponding salts (R(4)N)(4)[Sn(4)Q(10)] (Q = S, Se, Te) in high yield. Although the compound K(2)Sn(2)Te(5) is not known, this reaction is also applicable to solids with a nominal composition "K(2)Sn(2)Te(5)" which in the presence of R(4)NBr in en are quantitatively converted to the salts (R(4)N)(4)[Sn(4)Te(10)] on a multigram scale. These salts contain the molecular adamantane clusters [Sn(4)Q(10)](4-) and can serve as soluble precursors in simple metathesis reactions with transition metal salts to synthesize the large family of open-framework compounds (Me(4)N)(2)M[Sn(4)Se(10)] (M = Mn(2+), Fe(2+), Co(2+), Zn(2+)). Full structural characterization of these materials as well as their magnetic and optical properties is reported. Depending on the transition metal in (Me(4)N)(2)M[Sn(4)Se(10)] the energy band gaps of these compounds lie in the range of 1.27-2.23 eV. (Me(4)N)(2)Mn[Ge(4)Te(10)] is the first telluride analogue to be reported in this family. This material is a narrow band gap semiconductor with an optical absorption energy of 0.69 eV. Ab initio electronic band structure calculations validate the semiconductor nature of these chalcogenides and indicate a nearly direct band gap. Inorg Chem

The combination of ytterbium, nickel, iron in liquid aluminum resulted in the formation of the new intermetallic compound YbNi(2-x)Fe(x)Al(8) (x = 0.91) which adopts the CaCO(2)Al(8) structure type with a = 14.458(3) angstrom, b = 12.455(3) angstrom, c = 3.9818(8) angstrom and space group Pbam. Its resistivity drops with decreasing temperature, saturating to a constant value at lower temperatures. Above 50 K, the inverse magnetic susceptibility data follows Curie-Weiss Law, with a calculated mu(eff) = 2.19 mu(B). Although the observed reduced moment in magnetic susceptibility measurement suggests that the Yb ions in this compound are of mixed-valent nature, ab initio electronic structure calculations within density functional theory using LDA+U approximation give an f(13) configuration in the ground state. (C) 2008 Elsevier Inc. All rights reserved. Journal of Solid State Chemistry

Two rare earth iron aluminium silicides, REFe4Al9Si6 (RE = Tb, Er), were synthesized in liquid Al at temperatured below 850 degrees C. They crystallize in the tetragonal space group P4(2)/mnc (no. 137) with cell dimensions of a = 8.718(1) angstrom and c = 15.171(3) angstrom for the Tb analogue. The structure, which is highly intricate and represents a rare structural arrangement, is based on that of NdRh4Al15.4. It can be understood in terms of highly corrugated layers of merged Al-6 rings stacking to form a three-dimensional framework. the Fe and Si atoms are situated in various sites in the framework. The RE atoms have a very high coordination number (20) and sit in remaining pockets formed by the bonding arrangements in the structure. Magnetic measurements show that the rare earth ions are in a 3+ state, whereas Mossbauer measurements show that the Fe atoms do not exhibit a magnetic moment and are more reduced than in elemental Fe. The possible insights gained from these results into the mettallurgical processing of advanced aluminum matrix alloys are discussed. Thermal gravimetric analysis experiments in air show that REFe4Al9Si6 is resistant to oxidation up to 900 degrees C, Which is attributable to an alumina/silica surface scale. Chemistry of Materials

Organotin(IV) complexes with the formulas [(C6H5)3Sn(mbzt)] (1), [(C6H5)3Sn(cmbzt)] (3), and [(C6H5)2Sn(cmbzt)2] (4) (Hmbzt ) 2-mercaptobenzothiazole and Hcmbzt ) 5-chloro-2-mercaptobenzothiazole) have been synthesized and characterized by elemental analysis; FT-IR, Raman, 1H, 13C, and 119Sn NMR, and Mo¨ssbauer spectroscopic techniques; and X-ray crystallography at various temperatures. The crystal structures of complexes 1, 3, and 4 were determined by X-ray diffraction at room temperature [295(1) or 293(2) K]. The complexes [(C6H5)3Sn(mbzo)] (2) and [(n-C4H9)2Sn(cmbzt)2] (5) (Hmbzo ) 2-mercaptobenzoxazole) were synthesized by new improved methods, and their structures were determined at low temperature [100(1) K] and compared to those solved at room temperature. Comparison with {(CH3)2Sn(cmbzt)2]} (6), already reported, was also attempted. The influence of temperature on the geometry of the complexes is discussed. In the cases of complexes 1-3, three carbon atoms from phenyl groups and one sulfur atom and one nitrogen atom from thione ligands form a tetrahedrally distorted trigonal-bipyramidal geometry around the five-coordinate tin(IV) ion. In complexes 4-6, two carbon atoms from aryl groups and two sulfur atoms and two nitrogen atoms from thione ligands form a distorted tetrahedral geometry, tending toward octahedral, around the six-coordinate tin(IV) ions, with trans-C2, cis-N2, and cis-S2 configurations. Although the C-Sn and S-Sn bond distances are found to be constant in compounds 1-6, their N-Sn bond lengths vary significantly (from 2.635 to 3.078 Å), with the longer distances found in the cases of five-coordinate complexes 1-3. Inorg. Chem.

A detailed comparative Mossbauer study of La(0.67)Ca(0.33)MnO(3) and La(0.67)Sr(0.33)MnO(3) samples doped with 1% Sn is presented. The spectra at 5 K can be analyzed by a single ferromagnetic component. However, at higher temperatures two separate ferromagnetic components and a paramagnetic one are required to fit the spectra. The ferromagnetic component with the lower hyperfine field is attributed to clusters of weakened double-exchange interactions due to competition by localization mechanisms. Clear differences between the two samples in regard to the critical behavior arise: (i) The hyperfine field of La(0.67)Ca(0.33)Mn(0.99)Sn(0.01)O(3) disappears abruptly at T(c) in contrast to that of La(0.67)Sr(0.33)Mn(0.99)Sn(0.01)O(3) which varies continuously and goes to zero smoothly at the critical temperature. (ii) The second ferromagnetic phase appears above 0.35T(c) in the Ca sample but only above 0.83T(c) in the Sr sample. The paramagnetic component appears for T > 0.67T(c) in the former compared to T > 0.9T(c) in the latter. The results support recent studies that show differences in the polaronic character, and critical behavior thereof, between the two materials. Physical Review B

A detailed comparative Mossbauer study of La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 samples doped with 1% Sn is presented. The spectra at 5 K can be analyzed by a single ferromagnetic component. However, at higher temperatures two separate ferromagnetic components and a paramagnetic one are required to fit the spectra. The ferromagnetic component with the lower hyperfine field is attributed to clusters of weakened double-exchange interactions due to competition by localization mechanisms. Clear differences between the two samples in regard to the critical behavior arise: (i) The hyperfine field of La0.67Ca0.33Mn0.99Sn0.01O3 disappears abruptly at T-c in contrast to that of La0.67Sr0.33Mn0.99Sn0.01O3 which varies continuously and goes to zero smoothly at the critical temperature. (ii) The second ferromagnetic phase appears above 0.35T(c) in the Ca sample but only above 0.83T(c) in the Sr sample. The paramagnetic component appears for T > 0.67T(c) in the former compared to T > 0.9T(c) in the latter. The results support recent studies that show differences in the polaronic character, and critical behavior thereof, between the two materials. Physical Review B

MgO supported bimetallic catalysts containing a combination of Fe and Ni metals in 1:1 ratio at varying loadings (from 1 to 50 wt.%) were prepared by a wet impregnation method. Carbon nanotubes were synthesized over the prepared catalysts by the catalytic decomposition of acetylene for different reaction conditions. The effect of reaction temperature, reaction time and metal loading to the yield, structural perfection and morphology of the synthesized carbon products was investigated using a combination of XRD, DTA/DTG, Raman spectroscopy and Scanning Electron Microscopy (SEM) techniques. The results revealed that both the selection of the growing conditions and the metal loading are critical for the nature of the synthesized carbon nanotubes and can assign their yield and their overall quality. The synthesized carbon nanotubes exhibit extended crystallinity while they were synthesized at high yields. (c) 2006 Elsevier B.V. All rights reserved. Diamond and Related Materials

Sr2Fe1-xCrxMo1-xWxO6, x = 0, 0.05, 0.10, 0.15, 0.20, and 0.30 compounds have been prepared by the solid state encapsulation technique and their magnetic and magnetotransport properties have been studied. All samples show ferromagnetism at room temperature, the Curie temperature increases with x up to x = 0.10 (T-C = 426 K), remaining at high values even for x = 0.30 (T-C = 408 K). The resistivity of the low-doped (x < 0.10) as prepared compounds is the lowest reported in the literature for bulk samples at room temperature, but the low-field magnetoresistance is poor due to the lack of an appreciable insulating grain boundary layer in these samples. Enhancement of the low-field magnetoresistance is observed after post-annealing, due to modification of the composition of the grain boundary layer. (c) 2007 Elsevier B.V. All rights reserved. Journal of Magnetism and Magnetic Materials

International audience; Superconducting low dimensional systems are the natural choice for fast and sensitive infrared detection, because of their quantum nature and the low-noise, cryogenic operation environment. On the other hand, monochromatic and coherent electron beams, emitted from superconductors and carbon-based nanostructured materials, respectively, are significant for the development of electron optical systems such as electron microscopes and electron-beam nanofabrication systems. Here we describe for the first time a simple method which yields carbon nanotubes encapsulating single crystalline superconducting tin nanowires by employing the catalytic chemical vapor deposition method over solid tin dioxide. The superconducting tin nanowires, with diameters 15-35 nm, are covered with well-graphitized carbon walls and show, due to their reduced diameters, a critical magnetic field (H-c) more than 30 times higher than the value of bulk metallic tin.

The magnetic critical behavior of the manganese perovskite series La0.67-y (Sr; Ba; Ca) 0.33+y Mn1-xSnxO3 (x = 0.01, 0.02, y = 0, 0.07) is studied by means of dc magnetic measurements and Sn-119 Mossbauer spectroscopy. The structure can be described by a rhombohedral unit cell (space group R-3C) for the samples where the A-site is occupied by La and Sr or La and Ba ions and orthorhombic unit cell (space group Pnma) for the samples where the A-site is occupied by La and Ca ions. Arrott and scaling plots show that the samples, where the A-site is occupied by La and Sr or La and Ba ions, follow the behavior of a conventional second-order ferromagnetic transition. In contrast, the samples that contain La and Ca ions in the A-site show anomalous behavior around Curie point. Mossbauer measurements show two magnetic phases below T-c. One of them exhibits stronger exchange interactions with more rapid electron transfer between Mn3+/Mn4+, compared to the other. Hyperfine Interactions

Crystals of a water soluble, potassium(I) complex with the heterocyclic thioamide; 2-mercapto-nicotinic acid (H2mna), of formula {[K(H2mna)2]+.[K(ΞΌ-OH)2]-.4H2O}n (1) were grown from the filtrate of the reaction between 2-mercapto-nicotinic acid with KOH in a molar ratio 1:1.5 in water. The complex has been characterized by elemental analysis, TG-DTA, 1H NMR and FT-IR spectroscopic techniques and X-ray powder diffraction. The single crystal structure of complex (1) has been determined by X-ray diffraction at ambient conditions. The polymeric structure of the complex is microporous, where water molecules are retained. The water molecules can be reversibly removed. The complex is ionic, containing [S-K+-S] linkages and an infinite ribbon of {[K(ΞΌ-OH)2]-}n as a counter anion. Strong hydrogen bonds and Ο€-Ο€ interactions stabilize the supramolecular architecture of the inorganic/metal-organic hybrid formed. Heating of (1) at 100 Β°C for 4 h forms the {[K(H2mna)2]+ .[K(ΞΌ-OH)2]-}n (2), which retains the framework structure although the coordinated water molecules were evacuated. Inorg. Chim. Acta

The magnetic critical behaviour of the manganese perovskite series La0.67-y(Sr, Ba, Ca)(0.33+y)Mn1-xSnxO3 (x = 0.01, 0.02, y = 0, 0.07) is studied by means of dc magnetic measurements. The substitution of Mn by Sn ions in the samples results in a decrease of the transition temperature. The structure can be described by a rhombohedral unit cell (space group R-3C) for the samples where the A-site is occupied by La and Sr or La and Ba ions and an orthorhombic unit cell (space group Pnma) for the samples where the A-site is occupied by La and Ca ions. An increase of the cell volume is observed as Mn substituted by Sn ions in all samples. Arrott and scaling plots show that the samples, where the A-site is occupied by La and Sr or La and Ba ions, follow the behaviour of a conventional second-order ferromagnetic transition. The values of the critical exponents (beta, gamma) are between those predicted by the three-dimensional Heisenberg model and mean field theory. In contrast, the samples that contain La and Ca ions in the A-site show anomalous behaviour around the Curie point. Static disorder induced by Sn substitutions leads to a rounding of the transition. (c) 2006 Elsevier Ltd. All rights reserved. Solid State Communications

Polycrystalline double perovskites Sr2Fe1-xCr xMo1-xWxO6 with x = 0, 0.05, 0.10, 0.15, 0.20, and 0.30 have been prepared by sold state reactions. A continuous decrease of the tetragonal unit cell parameters α and c with increasing x values is observed. The highest Curie temperature T C = 426 K is recorded for the x = 0.10 compound. 57Fe M?ssbauer spectroscopy measurements indicate a non-integral electronic configuration of ?3d 5.3 for the Fe ions at the ordered double perovskite structure for x ?0.20, which reaches ?3d5.4 for x = 0.30. Fe-Mo/W anti-site and anti-phase boundary defects are observed in all samples in equal concentrations of around 3% of the total number of Fe ions in their structure. © 2006 Springer Science+Business Media, Inc. Hyperfine Interactions

Crystals of a water soluble, potassium(I) complex with the heterocyclic thioamide; 2-mercapto-nicotinic acid (H(2)mna), of formula {[K(H2mna)(2)](+) center dot [K(mu-OH)(2)](-) center dot 4H(2)O}(n) (1) were grown from the filtrate of the reaction between 2-mercapto-nicotinic acid with KOH in a molar ratio 1: 1.5 in water. The complex has been characterized by elemental analysis, TG-DTA, H-1 NMR and FT-IR spectroscopic techniques and X-ray powder diffraction. The single crystal structure of complex (1) has been determined by X-ray diffraction at ambient conditions. The polymeric structure of the complex is microporous, where water molecules are retained. The water molecules can be reversibly removed. The complex is ionic, containing [S-K+-S] linkages and an infinite ribbon of { [K(mu-OH)(2)](-)}(n) as a counter anion. Strong hydrogen bonds and pi-pi interactions stabilize the supramolecular architecture of the inorganic/metal-organic hybrid formed. Heating of (1) at 100 degrees C for 4 h forms the {[K(H2mna)(2)](+) center dot [K(V-OH)(2)](-)}(n) (2), which retains the framework structure although the coordinated water molecules were evacuated. (c) 2005 Elsevier B.V. All rights reserved. Inorganica Chimica Acta

The synthesis and detailed characterization of a few samples of the compound RbxMn[Fe(CN)(6)](y)center dot zH(2)O are described. The composition of the materials significantly depends on the applied preparative conditions. Analysis of spectroscopic results (FTIR, Raman, Fe-57 Mossbauer, XPS) and X-ray powder-diffraction data yielded a further assessment of the difference in structural features in terms of the amount of Fe(CN)6 vacancies and the associated number of water molecules. The characteristic individual magnetic behavior, as well as the metal-to-metal charge-transfer capabilities of the various samples, could be related to significant changes within the structures that appear to be associated with the synthetic method used. Chemistry of Materials

Polycrystalline double perovskites Sr2Fe1-x Cr (x) Mo1-x W (x) O-6 with x = 0, 0.05, 0.10, 0.15, 0.20, and 0.30 have been prepared by sold state reactions. A continuous decrease of the tetragonal unit cell parameters alpha and c with increasing x values is observed. The highest Curie temperature T (C) = 426 K is recorded for the x = 0.10 compound. Fe-57 Mossbauer spectroscopy measurements indicate a non-integral electronic configuration of similar to 3d(5.3) for the Fe ions at the ordered double perovskite structure for x

Mesostructured chalcogenide-based materials with long-range order and semiconducting properties can be prepared using suitable molecular building blocks, linkage metal ions and surfactant molecules. In this paper we present surfactant templated, open framework platinum tin selenicle and telluride materials assembled using K(4)SnQ(4) (Q = Se, Te) salts and K2PtCl4 as precursors and a study of pore and wall organization. We find that materials prepared in water exhibit disordered pore organization, whereas those prepared in formamide are long-range ordered with hexagonal symmetry. In formannide the [SnQ(4)](4-) anions undergo condensation-oligomerization reactions that produce different chalcogenido molecular species, whereas in water the anions remain intact. In addition to solvent, the pore organization and overall quality of the mesostructured materials strongly depend on the surfactant molecules, i.e., chain length and headgroup size. For example, highly ordered mesostructured platinum tin selenides with hexagonal symmetry were obtained using the hydroxyl-functionalized surfactants CnH2n+1N(CH3)(CH2CH2OH)(2)Br (n = 16, 18, and 20), but when the headgroup was triethylammonium, hexagonal pore order was achieved only for n = 20 and not for n = 16 and 18. The experimental results imply that in order to achieve highly ordered chalcogenide frameworks a single building anionic block might be insufficient. Finally, we also report the first examples of hexagonal mesostructured Pt/Sn/Te materials based on K4SnTe4 as the precursor. The tellurides behave differently for their selenium analogues and have very low energy band gaps, in the range 0.5-0.7 eV. J Am Chem Soc

A detailed electrochemical study of a novel composite film based on ferrocene intercalated vanadium pentoxide xerogel/polyvinyl alcohol (FeCp(2)/VXG PVA-SbQ) and its potential use in the development of amperometric biosensors is presented. FeCp(2)-VXG was characterized with X-ray powder diffraction, Mossbauer spectroscopy, energy dispersive spectroscopy and IR-spectroscopy suggesting a molecular formula close to (FeCp(2))(0.37)center dot V(2)O(5)center dot nH(2)O. Composite films of (FeCp(2))(0.37)center dot V(2)O(5)center dot nH(2)O with PVA-SbQ were developed over a glassy carbon electrode. Cyclic voltammetry experiments showed that composite films exhibit reversible, almost charge-transfer controlled redox functions. The influence of various buffering systems composition on the working stability of the so modified electrodes was also investigated. Redox films were further modified by immobilizing glucose oxidase as a model enzyme. A remarkable electrocatalytic effect of the intercalated FeCp(2) towards the reduced form of the enzyme cofactor (FAD-H(2)) was observed. Under optimized conditions, glucose biosensor was mounted into a flow injection analysis manifold and found to yield a linear response up to 10 mM glucose. (C) 2005 Elsevier B.V. All rights reserved. Electrochemistry Communications

The efficiency of Fe-Mn-Zn-Ti-O mixed-metal oxides of varying composition prepared by sol-gel methods toward removal of H2S from a gas mixture containing 0.06 vol% H2S, 25 vol% H-2, 7.5 vol% CO2, and 1-3 vol% H2O was studied in the 25-100 degrees C range. In particular, the effects of the Fe/Mn molar ratio in the Fe-Mn-Zn-Ti-O solids on the H2S uptake and regeneration performance of the solids were studied. The nominal chemical composition (metal mol%) of the Fe-Mn-Zn-Ti-O solids was found to strongly influence the chemical composition, particle size, and morphology of the crystal phases formed. It was found that the 5 Fe-15 Mn-40 Zn-40 Ti-O mixed-metal oxide provides the highest H2S uptake as fresh and after regeneration in 20% O-2/He gas mixture in the 500-750 degrees C range compared with the other solids investigated. It was also found that 5 Fe-15 Mn-40 Zn-40 Ti-O exhibits higher H2S uptake than a commercial Ni-based H2S adsorbent in the 25-50 degrees C range. In particular, a three times greater H2S uptake at 25 degrees C compared with that on the commercial adsorbent was found. The effectiveness of the regeneration procedure of 5 Fe-15 Mn-40 Zn-40 Ti-O solid after complete sulfidation was found to be in the 48-82% range, depending on the sulfidation temperature and regeneration conditions applied. A detailed characterization of the fresh. sulfided, and regenerated 5 Fe-15 Mn-40 Zn-40 Ti-O and 20 Fe-40 Zn-40 Ti-O solids, which exhibited the best and worst H2S uptake performance, respectively, using BET, XRD, Raman, XPS, and Mossbauer techniques revealed important information on the sulfidation mechanism. The present work provides new fundamental knowledge that could trigger further research efforts toward the development of alternative mixed metal oxides not based on toxic chromia (Cr2O3-Fe2O3/alpha-Al2O3), Which is used today in several industrial plants for the catalytic oxidation of H2S (Claus process). (c) 2005 Elsevier Inc. All rights reserved. Journal of Catalysis

Fe-57 Mossbauer spectra at 85, 200 and 293 K of magnetically aligned powders of Nd-3(Fe1-xCox)(27.7)Ti-1.3 (0

Starting with the Nd-3(Fe,Ti)(29) stoichiometry [Tb-3(Fe1-xCox)(27.4)V-1.6 and DY3(Fe1-xCox)(27.8)V-1.2; x = 0.6, 0.8, 1.0] two novel series of R-Fe-Co-V intermetallic compounds with a disordered variant of the hexagonal Th2Ni17-type structure were formed. The cell parameters decrease and the Curie temperature increases with increasing Co content. XRD patterns of magnetically aligned powder samples revealed the presence of a planar magnetic anisotropy. (C) 2003 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds

Substituted perovskite-type mixed oxides of the general formula La1-xSrx(Fe3+/Fe4+)O3+/-6 were prepared for x = 0.00, 0.15, 0.30, 0.40, 0.60, 0.70, 0.80, and 0.90 by the ceramic method and heating at 1000degreesC. The prepared solids were examined by X-ray diffractogram (XRD) for their crystal structure and by Mossbauer spectroscopy at RT for the kind and the exact amount of iron containing crystal phases. The gradual substitution of La3+ by Sr2+ results in a quantitative development of the crystal phase SrFe4+O3 and the corresponding diminution of the rest phases containing iron, i.e. LaFeO3 and Fe2O3 (traces). Detailed thermogravimetric O-2/temperature-programmed desorption (TPD) experiments showed that the solids release oxygen when heated in a He atmosphere which is strictly proportional to the amount of Fe4+ in the samples. Quantitative calculations showed that exactly one atom of oxygen is released per unit cell of Sr-Fe-O perovskite, which contains four Sr(Fe4+/Fe3+)O3+/-delta units. The phenomenon is reversible and the solids re-adsorb fast and quantitatively the lost lattice oxygen when gaseous oxygen is admitted back to the system. (C) 2002 Elsevier Science B.V. All rights reserved. Applied Catalysis a-General

The compounds RE4FeGa12-xGex (RE = Sm, Tb) were discovered in reactions employing molten Ga as a solvent at 850 degreesC. However, the isostructural Y4FeGa12-xGex was prepared from a direct combination reaction. The crystal structure is cubic with space group Im (3) over barm, Z = 2, and a = 8.657(4) Angstrom and 8.5620(9) Angstrom for the Sm and Tb analogues, respectively. Structure refinement based on full-matrix least squares on F-0(2) resulted in R-1 = 1.47% and wR(2) = 4.13% [1 > 2sigma(1)] for RE = Sm and R-1 = 2.29% and wR(2) = 7.12% [1 > 2sigma(l)] for RE = Tb. The compounds crystallize in the U4Re7Si6 structure type, where the RE atoms are located on 8c (1/4, 1/4, 1/4) sites and the Fe atoms on 2a (0, 0, 0) sites. The distribution of Ga and Ge in the structure, investigated with single-crystal neutron diffraction on the Tb analogue, revealed that these atoms are disordered over the 12d (1/4, 0, 1/2) and 12e (x, 0, 0) sites. The amount of Ga/Ge occupying the 12d and 12e sites refined to 89(4)/11 and 70(4)/30%, respectively. Transport property measurements indicate that these compounds are metallic conductors. Magnetic susceptibility measurements and Mossbauer spectroscopy performed on the Tb analogue show a nonmagnetic state for Fe, while the Tb atoms carry a magnetic moment corresponding to a mu(eff) of 9.25 mu(B). Inorg Chem

We report on magnetometry, resistivity and Mossbauer spectroscopy measurements on single-phase Fe(3)BO(5) in a wide temperature range from 4.2 to 620 K. Magnetically split Mossbauer spectra were observed below T(N) = 114 K, although a proportion of the Fe(2+) ions in the basal plane (crystallographic site Fe1) remain paramagnetic down to the ferrimagnetic transition at T(w) = 74 K. This unusual magnetic behaviour known as 'idle-spin behaviour' can be explained by the competitive magnetic interactions with its neighbouring ordered ions and should be related to the topology of the octahedral Fe I sites in the crystal structure of Fe(3)BO(5). The behaviour change recorded in the de magnetization and Mossbauer data indicates that the magnetic structure of Fe(3)BO(5) should change at 74 K, where the spin frustration gradually ceases to exist. Electron delocalization in the Fe3-Fe2-Fe3 triads between pairs of Fe(2+) and Fe(3+) ions was observed at all temperatures between 4.2 and 180 K and coexists with localized ferric and ferrous (Fe1 and Fe4 crystallographic sites) states. Above 180 K the delocalization in the Fe3-Fe2-Fe3 triads includes the rest of the Fe(3+) ions and some evidence can be seen in the resistivity data as well. Journal of Physics-Condensed Matter