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The metalloantibiotic of formula Ph2Sn(CIP)2 (CIPTIN) (HCIP = ciprofloxacin) was synthesized by reacting ciprofloxacin hydrochloride (HCIP·HCl) (an antibiotic in clinical use) with diphenyltin dichloride (Ph2SnCl2DPTD). The complex was characterized in the solid state by melting point, FT-IR, X-ray Powder Diffraction (XRPD) analysis, 119Sn Mossbauer spectroscopy, X-ray Fluorescence (XRF) spectroscopy, and Thermogravimetry/Differential Thermal Analysis (TG-DTA) and in solution by UV-Vis, 1H NMR spectroscopic techniques and Electrospray Ionisation Mass Spectrometry (ESI-MS). The crystal structure of CIPTIN and its processor HCIP was also determined by X-ray crystallography. The antibacterial activity of CIPTIN, HCIP·HCl, HCIP and DPTD was evaluated against the bacterial species Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), by the means of Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Inhibition Zones (IZs). CIPTIN shows lower MIC values than those of HCIP·HCl (up to 4.2-fold), HCIP (up to 2.7-fold) or DPTD (>135-fold), towards the tested microbes. CIPTIN is classified into bactericidal agents according to MBC/MIC values. The developing IZs are 40.8 ± 1.5, 34.0 ± 0.8, 36.0 ± 1.1 and 42.7 ± 0.8 mm, respectively which classify the microbes P. aeruginosa, E. coli, S. aureus and S. epidermidis to susceptible ones to CIPTIN. These IZs are greater than the corresponding ones of HCIP·HCl by 1.1 to 1.5-fold against both the tested Gram negative and Gram positive bacteria. CIPTIN eradicates the biofilm of P. aeruginosa and S. aureus more efficiently than HCIP·HCl and HCIP. The in vitro toxicity and genotoxicity of CIPTIN were tested against human skin keratinocyte cells (HaCaT) (IC50 = 2.33 μM). CIPTIN exhibits 2 to 9-fold lower MIC values than its IC50 against HaCaT, while its genotoxic effect determined by micronucleus assay is equivalent to the corresponding ones of HCIP·HCl or HCIP.

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.

Li2SnS3 is a fast Li+ ion conductor that exhibits high thermal stability (mp ∼750 °C) as well as environmental stability under ambient conditions. Polycrystalline Li2SnS3 was synthesized using high-temperature, solid-state synthesis. According to single-crystal X-ray diffraction, Li2SnS3 has a sodium chloride-like structure (space group C2/c), a result supported by synchrotron X-ray powder diffraction and 119Sn Mossbauer spectroscopy. According to impedance spectroscopy, Li2SnS3 exhibits Li+ ion conductivity up to 1.6 × 10–3 S/cm at 100 °C, which is among the highest for ternary chalcogenides. First-principles simulations of Li2SnS3 and the oxide analogue, Li2SnO3, provide insight into the basic properties and mechanisms of the ionic conduction. The high thermal stability, significant lithium ion conductivity, and environmental stability make Li2SnS3 a promising new solid-state electrolyte for lithium ion batteries.

Triangular FePt nano-islands with size ~70 and ~330 nm have been prepared by using regular single-layer arrays of nanospheres (173 nm) and microspheres (978 nm), as deposition masks. The coercivity of the 330 nm islands is close to that of the continuous film (11 kOe) whereas the 70 nm ones have coercivity close to 9 kOe and their hysteresis is characterized by the coexistence of an uncoupled soft phase. The switching behavior is characterized by non-zero dM-plots. The lower dM is obtained for the 70 nm sample heat-treated at 500 °C for 15 min and increases for longer times and higher heat-treatment temperatures. 10% of the islands are in multi-domain state. These findings are compared with micromagnetic modeling which shows that for anisotropy values high enough to match the observed coercivity, multidomain islands can result in due to the existence of either a softer part or different anisotropy direction part within each magnetic entity. Journal of Magnetism and Magnetic Materials

MCM-41-supported nanoscale zero-valent iron (nZVI) was sytnhesized by impregnating the mesoporous silica martix with ferric chloride, followed by chemical reduction with NaHB4. The samples were studied with a combination of characterization techniques such as powder X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Mössbauer spectroscopy, N2 adsorption measurements, transmission electron microscopy (TEM), magnetization measurements, and thermal analysis methods. The experimental data revealed development of nanoscale zero-valent iron particles with an elliptical shape and a maximum size of ∼80 nm, which were randomly distributed and immobilized on the mesoporous silica surface. Surface area measurements showed that the porous MCM-41 host matrix maintains its hexagonal mesoporous order structure and exhibits a considerable high surface area (609 m(2)/g). Mössbauer and magnetization measurements confirmed the presence of core-shell iron nanoparticles composed of a ferromagnetic metallic core and an oxide/hydroxide shell. The kinetic studies demonstrated a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these stabilized nZVI particles on MCM-41, and a considerably increased reduction capacity per unit mass of material in comparison to that of unsupported nZVI. The results also indicate a highly pH-dependent reduction efficiency of the material, whereas their kinetics was described by a pseudo-first order kinetic model.

The reaction of Fe(ClO4)3·9H2O with 2-pyrrole aldoxime (pyroxH2) and two equivalents of sodium benzoate in MeCN afforded the complex {[FeIII6O2(OH)2(pyroxH)2(PhCOO)10(H2O)2]·[FeIII3O(pyroxH2)2(PhCOO)6(MeCN)](ClO4)·6.6MeCN} (1·6.6MeCN) in moderate yield. Repeating the same reaction in EtOH gave the complex [FeIII6O2(OH)2(pyroxH)2(PhCOO)10(EtOH)2] (2) in good yield. The crystal structures of 1 and 2 have been determined by single-crystal X-ray crystallography. Complex 1 contains two different clusters in the crystal: a trinuclear [FeIII3] molecule and a hexanuclear [FeIII6] unit, both of which contain different forms of the 2-pyrrole aldoxime ligand. Complex 2 is a hexanuclear [FeIII6] cluster almost identical with the hexametallic unit found in 1, with the difference being the presence of two terminal EtOH molecules in 2 versus two terminal H2O molecules in the hexametallic sub-unit of 1. DC magnetic susceptibility studies were performed on polycrystalline sample of 2, revealing the presence of strong antiferromagnetic interactions within the cluster leading to a well isolated diamagnetic ground-state. The oxidation state of the iron atoms in 2 were further established by Mossbauer studies performed at 77 K.

Magnetic Fe(2)O(3)/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. Mössbauer spectroscopy and magnetic measurements at low temperatures confirmed the formation of γ-Fe(2)O(3) 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.

The iron(III) spin-crossover compounds [Fe(Hthsa)(thsa)]⋅H2O (1), [Fe(Hth5Clsa)(th5Clsa)2]⋅H2O (2), and [Fe(Hth5Brsa)(th5Brsa)2]⋅H2O (3) (H2thsa=salicylaldehyde thiosemicarbazone, H2th5Clsa=5-chlorosalicylaldehyde thiosemicarbazone, and H2th5Brsa=5-bromosalicylaldehyde thiosemicarbazone) have been synthesized and their spin-transition properties investigated by magnetic susceptibility, Mossbauer spectroscopy, and differential scanning calorimetry measurements. The three compounds exhibit an abrupt spin transition with a thermal hysteresis effect. The more polarizable the substituent on the salicylaldehyde moiety, the more complete is the transition at room temperature with an increased degree of cooperativity. The molecular structures of 1 and 2 in the high-spin state are revealed. The occurrence of the light-induced excited-spin-state trapping phenomenon appears to be dependent on the substituent incorporated into the 5-position of the salicylaldehyde subunit. Whereas the compounds with an electron-withdrawing group (-Br or ‒Cl) exhibit light-induced trapped excited high-spin states with great longevity of metastability, the halogen-free compound does not, even though strong intermolecular interactions (such as hydrogen-bonding networks and π stacking) operate in the system. For compound 2, the surface level of photoconversion is less than 35 %. In contrast, compound 3 displays full photoexcitation.

Single crystals of CaCr0.84Fe3.16As3, a Cr substituted analog of CaFe4As3, were grown from Sn flux and characterized with single crystal neutron diffraction. CaCr0.84Fe3.16As3 crystallizes in the orthorhombic space group Pnma with a three-dimensional framework, where Fe, Cr, and As form a covalent channel-like network with Ca2+ cations residing in the channels. CaCr0.84Fe3.16As3 has a unit cell of a = 12.057(4) A, b = 3.7374(13) A, and c = 11.694(3) A, as determined by room temperature single crystal neutron diffraction (R1 = 0.0747, wR2 = 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.

We report experimental evidence that shows superconductivity in NaFeAs occurs when it is Na deficient. The oxidation of NaFeAs progresses differently in water and in air. In water the material oxidizes slowly and slightly retaining the original anti-PbFCl structure. In air NaFeAs oxidizes topotactically quickly and extensively transforming to the ThCr2Si2 structure type. Water acts as a mild oxidizing agent on the FeAs layer by extracting electrons and Na+ cations from the structure, while oxidation in air is more extensive and leads to change in structure type from NaFeAs to NaFe2As2. The superconducting transition temperature moves dramatically during the oxidation process. Exposed to water for an extended time period NaFeAs shows a substantial increase in Tc up to 25 K with contraction of unit cell volume. NaFe2As2, the air oxidized product, shows Tc of 12 K. We report detailed characterization of the redox chemistry and transformation of NaFeAs in water and air using single crystal and powder X-ray di...

A trinuclear iron(III) oxo-centered complex [Fe3(μ3-O)(3-OCH3-salnec)3]OH·5H2O was synthesized and characterized as cluster containing the semi-cubane [Fe3(μ3-O)]7+ core. The central oxygen atom is bridging the three iron(III) ions, which form an equilateral triangle with an average edge of –3.00 A as it was deduced from X-ray diffraction studies. The new tetradentate ligand 3-OCH3-salnecH2 = 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-OCH3-saloH2), in the presence of sodium methoxide and Fe3+. 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.

Experimental interactions of Slovak bentonites with metallic ironThe experimental stability of four bentonites and one K-bentonite from Slovak deposits in the presence of iron was studied to simulate the possible reactions of clays (bentonite barrier) in the contact with Fe containers in a nuclear waste repository. The batch experiments were performed at 60 °C for 30 and 120 days in aerobic conditions. The reaction products were examined by XRD, FTIR, and Mössbauer spectroscopies and CEC (cation exchange capacities) were determined. Reaction solutions were analysed for selected elements using AAS (atomic absorption spectrometry). The results show that bentonites do not interact equally with metallic iron. Bentonites from the Jelšový Potok, Kopernica and Lieskovec deposits reacted similarly whereas the interaction between the bentonite from Lastovce and the iron was less intensive. The lower reactivity of the bentonite from Lastovce can be explained by its low content of smectite. During iron-clay interactions the iron was consumed and Fe oxides (magnetite, lepidocrocite) were formed. Decrease of the smectite diffraction peaks intensity and CEC values during the experiments show rather the rearrangement of the original smectite crystals than dissolution of smectite. In the K-bentonite from the Dolná Ves deposit where the mixed-layer illite-smectite is present instead of smectite, the dissolution of illite-smectite was observed along with the neoformation of smectite. The structure of illite-smectite deteriorated more than the structure of smectites which suggests that this mixed-layer illite-smectite is much less stable in the presence of iron than smectites.

The reaction of metal(II) nitrates with oxamide-N,N′-diacetic acid (H4L) in aqueous media under mild conditions, leads to the formation of novel coordination polymers formulated as {[M(H2L)(H2O)x]·2(H2O)}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.

The magnetic properties of magnetron sputtered Co films (with in-plane anisotropy) and Co/Pt multilayers (with perpendicular anisotropy) deposited on elastomeric poly-dimethylsiloxane (PDMS) films and nanostructured templates are presented. Apart from the etched nanosize features, maze-like submicron features develop after the sputter deposition as a result of film buckling due to thermal contraction of the underlying PDMS layer. The nanostructured templates can physically isolate the magnetic entities but magnetic correlations within the range of the buckling features remain. By using oblique deposition geometries in-plane anisotropy develops and it is transferred to the PDMS buckling patterns. In the case of Co/Pt multilayers deposition on PDMS nanostructured templates results in a loss of the perpendicular anisotropy, attributed to the acuteness of the PDMS nanostructures. (C) 2009 Elsevier B. V. All rights reserved. Journal of Magnetism and Magnetic Materials

Synthesis and structural investigation of trimethyl and triphenyltin esters of the 3-, 4-amino and 3,5-diaminobenzoic acids are reported as a reinvestigation of their local and overall molecular structure based on crystal structure determinations and on correlation of solid state vibrational and -emission spectroscopic evidence. Evidence is provided for the existence of more than one tin environment and therefore different carboxylate coordination modes in the compounds. Journal of Coordination Chemistry

The reaction of K2Sn2Q5 (Q = S, Se, Te) with stoichiometric amounts of alkyl-ammonium bromides R4NBr (R = methyl or ethyl) in ethylenediamine (en) afforded the corresponding salts (R4N)4[Sn4Q10] (Q = S, Se, Te) in high yield. Although the compound K2Sn2Te5 is not known, this reaction is also applicable to solids with a nominal composition “K2Sn2Te5” which in the presence of R4NBr in en are quantitatively converted to the salts (R4N)4[Sn4Te10] on a multigram scale. These salts contain the molecular adamantane clusters [Sn4Q10]4− and can serve as soluble precursors in simple metathesis reactions with transition metal salts to synthesize the large family of open-framework compounds (Me4N)2M[Sn4Se10] (M = Mn2+, Fe2+, Co2+, Zn2+). Full structural characterization of these materials as well as their magnetic and optical properties is reported. Depending on the transition metal in (Me4N)2M[Sn4Se10], the energy band gaps of these compounds lie in the range of 1.27−2.23 eV. (Me4N)2Mn[Ge4Te10] is the first tellurid...

Two rare earth iron aluminum silicides, REFe4Al9Si6 (RE = Tb, Er), were synthesized in liquid Al at temperatures below 850 °C. They crystallize in the tetragonal space group P42/nmc (no. 137) with cell dimensions of a = 8.718(1) A and c = 15.171(3) A 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 Al6 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 metallurgical processing of advanced al...

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 degrees C in order to achieve the L1(0) 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 Mossbauer 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) L1(0) 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 Mossbauer spectra of the as prepared samples. Mossbauer 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 L1(0) 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.

A comparative study between two groups of substituted perovskite-type solids, one oxidic and another chlorinated with general formulas La1−xSrxFeO3±δ and La1−xSrxFeO3±δClσ ( x = 0.0 , 0.4 , 0.6 and 0.8), was carried out for the oxidation of CH4 by O2 and N2O. For stoichiometric feeding compositions CH4:O2 = 1:2 and CH4:N2O = 1:4, the catalysts were active in the temperature range 400–760 °C. The oxidic solids were more active than the chlorinated ones. Catalysts of both groups, containing Sr, exhibited a drop in activity for the above reactions, related to an increased amount of desorbed oxygen from the solids. The amount of desorbed oxygen is linearly correlated with the Fe4+ content in the solid. The lower activity of the chlorinated samples can be attributed to a poisoning effect by chlorine, the quantity of which was estimated using proper deactivation kinetics.

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.

Polycrystalline Li2SnS3 is prepared by solid state reaction of stoichiometric amounts of Li2S, Sn, and S (graphite crucible in evacuated silica tube, 750 °C, 96 h).

The magnetic critical behaviour of the manganese perovskite series La0.67−y(Sr,Ba,Ca)0.33+yMn1−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 - 3 C ) 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 ( β , γ ) 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.

The magnetic critical behavior of the manganese perovskite series La0.67−y (Sr, Ba, Ca)0.33+y Mn1−x SnxO3 (x=0.0l, 0.02, y=0, 0.07) is studied by means of de magnetic measurements and 119Sn 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.

Crystals of a water soluble, potassium(I) complex with the heterocyclic thioamide; 2-mercapto-nicotinic acid (H2mna), of formula {[K(H2mna)2]+ · [K(μ-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(μ-OH)2]−}n as a counter anion. Strong hydrogen bonds and π–π interactions stabilize the supramolecular architecture of the inorganic/metal-organic hybrid formed. Heating of (1) at 100 °C for 4 h forms the {[K(H2mna)2]+ · [K(μ-OH)2]−}n (2), which retains the framework structure although the coordinated water molecules were evacuated.

A detailed electrochemical study of a novel composite film based on ferrocene intercalated vanadium pentoxide xerogel/polyvinyl alcohol (FeCp2/VXG–PVA–SbQ) and its potential use in the development of amperometric biosensors is presented. FeCp2–VXG was characterized with X-ray powder diffraction, Mössbauer spectroscopy, energy dispersive spectroscopy and IR-spectroscopy suggesting a molecular formula close to (FeCp2)0.37 · V2O5 · nH2O. Composite films of (FeCp2)0.37 · V2O5 · nH2O 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 FeCp2 towards the reduced form of the enzyme cofactor (FAD-H2) 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. Keywords: Vanadium pentoxide xerogel, Ferrocene, Intercalation, Amperometric glucose amperometric biosensor, Photocrosslinkable styrylpyridinium modified polyvinyl alcohol

Clay-carbon nanotube composites were prepared by employing the catalytic chemical vapor deposition method (CCVD) over different transition metal oxides supported on montmorillonite. Various analytical techniques including SEM, TEM, XRD and DTA/TGA were used for the characterization of the final composite materials. The morphology, quality and structure of the produced nanotubes is shown to be dependent on the type of transition metals.

Three fulleropyrrolidine derivatives, characterized by the presence of positive charges, were introduced in the interlayer space of montmorillonite. The composites were characterized by powder X-ray diffraction and differential thermal and thermogravimetric (DTA-TGA) analysis, in conjunction with FTIR, UV-Vis, Raman, and Fe-57-Mossbauer spectroscopies. Organophilic derivatives were intercalated into organically modified clays, while water-soluble fulleropyrrolidines were introduced into the clay galleries through ion exchange. The experiments, complemented by computer simulations, show that not all the clay-clay platelets are intercalated by the fullerene derivatives and that a sizable amount of charge transfer takes place between the host and the guests. J Am Chem Soc

Starting with the Nd 3 (Fe,Ti) 29 stoichiometry [Tb 3 (Fe 1− x Co x ) 27.4 V 1.6 and Dy 3 (Fe 1− x Co x ) 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 Th 2 Ni 17 -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.

The synthesis and characterization of the organotin compounds [(n-C(4)H(9))(2)Sn(cys)] (1), [(C(6)H(5))(2)Sn(cys)] (2), [(C(6)H(5))(3)Sn(Hcys).(H(2)o)] (3), {[(CH(3))(2)Sn(Kcys)(2)].2(H(2)0)} (4), {[(n-C(4)H(9))(2)Sn(Kcys)(2)].2(H(2)0)} (5) and {[(C(6)H(5))(2)Sn(Kcys)(2)].2(H(2)0)} (6) (where H(2)cys = L-cysteine) are reported. The compounds have been characterized by elemental analysis and (1)H-NMR, Uv-Vis, FT-IR and MOssbauer spectroscopic techniques. Attempted recrystallization of (2) in DMSO/methanol 2:1 solution yielded after several days unexpectedly the dimeric compound bis(tri-phenyltin)sulphide {[(C(6)H(5))(3)Sn](2)S} (7) which has been characterized by x-ray analysis. The structure of the parent complex (2) as well as the mechanism of the decomposition of cysteine are being further investigated. The in vitro anticancer activity of complexes (I)- (6), against human leukemia (HL60), human liver (Bel7402), human stomach (BGC823) and human cervix epithelial human carcinoma (Hela), nasopharyngeal carcinoma (KB) and lung cancer (PG) tumor cells, were evaluated.

Fe2O3–Al2O3 composites were prepared by interaction of acetic acid vapors with iron oxides dispersed on the surface of a sol–gel derived porous alumina. Upon pyrolysis the created iron acetate species were transformed to magnetic iron oxide nanoparticles. The atmosphere which is used during the synthetic procedure affects significantly the nature of the nanoparticles which could be either γ-Fe2O3 or magnetite, or non-magnetic such as α-Fe2O3. X-Ray diffraction, surface area measurements and scanning electron microscopy (SEM) were used for the structural characterization and determination of the sorption properties of the composite material properties. The development of magnetic phases decreases the specific surface area of alumina by seeding of the alumina particles and, in parallel, the coverage of their free surface. Mossbauer spectroscopy, magnetic measurements and transmission electron microscopy (TEM) provide evidence for the formation, size and type of magnetic iron oxide phases.

Substituted perovskite-type mixed oxides of the general formula La 1− x Sr x (Fe 3+ /Fe 4+ )O 3± δ 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 1000 °C. 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 La 3+ by Sr 2+ results in a quantitative development of the crystal phase SrFe 4+ O 3 and the corresponding diminution of the rest phases containing iron, i.e. LaFeO 3 and Fe 2 O 3 (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 Fe 4+ 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(Fe 4+ /Fe 3+ )O 3± δ 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.

The title compounds are characterized by synchrotron powder XRD, neutron powder diffraction, 57Fe and 119Sn Moessbauer spectroscopy, UV/VIS/NIR diffuse reflectance spectroscopy, and magnetic measurements.

The compounds RE4FeGa(12-x)Ge(x) (RE = Sm, Tb) were discovered in reactions employing molten Ga as a solvent at 850 degrees C. However, the isostructural Y4FeGa(12-x)Ge(x) was prepared from a direct combination reaction. The crystal structure is cubic with space group Imm, Z = 2, and a = 8.657(4) A and 8.5620(9) A for the Sm and Tb analogues, respectively. Structure refinement based on full-matrix least squares on F(o)2 resulted in R1 = 1.47% and wR2 = 4.13% [I2(I)] for RE = Sm and R1 = 2.29% and wR2 = 7.12% [I2(I)] 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 Mössbauer 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).

If the full scientific and technological potential of mesostructured materials is to be achieved, systems with continuous domains in the form of single crystals or films must be prepared. Here we report a reliable and facile system for making large single-crystal particles of chalcogenido mesostructured materials with a highly organized cubic structure, accessible pore structure, and semiconducting properties. Building blocks with square planar bonding topology, Pt(2+) and [Sn(2)Se(6)](4)(-), in combination with long-chain pyridinium surfactants (C(n)PyBr, n = 18, 20) favor faceted single-crystal particles with the highest possible space group symmetry Ia3d. This is an important step toward developing large single-domain crystalline mesostructured semiconductors and usable natural self-assembled antidot array systems. The tendency toward cubic symmetry is so strong that the materials assemble readily under experimental conditions that can tolerate considerable variation and form micrometer-sized rhombic dodecahedral cubosome particles. The c-C(n)PyPtSnSe materials are the first to exhibit reversible ion-exchange properties. The surfactant molecules can be ion-exchanged reversibly and without loss of the cubic structure and particle morphology. The cubosomes possess a three-dimensional open Pt-Sn-Se framework with a low-energy band gap of approximately 1.7 eV.

We present the first report of hexagonally ordered mesostructured ternary metal tin sulfide materials along with their structure and optical properties. The new mesophases designated as (CP)xMySn2S6 (M = Zn2+, Cd2+, Ga3+) where synthesized by linking [Sn2S6]4- clusters with metal ions in the presence of cetylpyridinium (CP) surfactant molecules in formamide solution under basic conditions. The materials are semiconductors in the energy range 2.5 < Eg < 3.1 eV. The mesostructured (CP)xMySn2S6 show photoluminescence, when excited with light above the band gap.

We report on magnetometry, resistivity and Mossbauer spectroscopy measurements on single-phase Fe3BO5 in a wide temperature range from 4.2 to 620 K. Magnetically split Mossbauer spectra were observed below TN = 114 K, although a proportion of the Fe2+ ions in the basal plane (crystallographic site Fe1) remain paramagnetic down to the ferrimagnetic transition at Tw = 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 Fe1 sites in the crystal structure of Fe3BO5. The behaviour change recorded in the dc magnetization and Mossbauer data indicates that the magnetic structure of Fe3BO5 should change at 74 K, where the spin frustration gradually ceases to exist. Electron delocalization in the Fe3-Fe2-Fe3 triads between pairs of Fe2+ and Fe3+ 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 Fe3+ ions and some evidence can be seen in the resistivity data as well.

Li2FeGeS4 (LIGS) and Li2FeSnS4 (LITS), which are among the first magnetic semiconductors with the wurtz-kesterite structure, exhibit antiferromagnetism with TN ≈ 6 and 4 K, respectively. Both compounds undergo a conventional metamagnetic transition that is accompanied by a hysteresis; a reversible spin-flop transition is dominant. On the basis of constant-wavelength neutron powder diffraction data, we propose that LIGS and LITS exhibit collinear magnetic structures that are commensurate and incommensurate with propagation vectors km = [1/2, 1/2, 1/2] and [0, 0, 0.546(1)], respectively. The two compounds exhibit similar magnetic phase diagrams, as the critical fields are temperature-dependent. The nuclear structures of the bulk powder samples were verified using time-of-flight neutron powder diffraction along with synchrotron X-ray powder diffraction. (57)Fe and (119)Sn Mössbauer spectroscopy confirmed the presence of Fe(2+) and Sn(4+) as well as the number of crystallographically unique positions. LIGS and LITS are semiconductors with indirect and direct bandgaps of 1.42 and 1.86 eV, respectively, according to optical diffuse-reflectance UV-vis-NIR spectroscopy.

Naturally abundant enzymes often feature active sites comprising transition metal cluster units that catalyze chemical processes and reduce small molecules as well as protons. We introduce a family of new chalcogenide aerogels (chalcogels), aiming to model the function of active sites and the structural features of a larger protective framework. New metal incorporated iron sulfur tin sulfide chalcogels referred to as ternary chalcogels and specifically the chalcogels M-ITS-cg3, fully integrate biological redox-active Fe4S4 clusters into a semiconducting porous framework by bridging them with Sn4S10 linking units. In the M-ITS-cg3 system we can tailor the electro- and photocatalytic properties of chalcogels through the control of spatial distance of redox-active Fe4S4 centers using additional linking metal ions, M(2+) (Pt, Zn, Co, Ni, Sn). The presence of a third metal does not change the structural properties of the biomimetic chalcogels but modifies and even enhances their functional performance. M-ITS-cg3s exhibit electrocatalytic activity in proton reduction that arises from the Fe4S4 clusters but is tuned inductively by M(2+). The metal ions alter the reduction potential of Fe4S4 in a favorable manner for photochemical hydrogen production. The Pt incorporated ITS-cg3 shows the greatest improvement in the overall hydrogen yield compared to the binary ITS-cg3. The ability to manipulate the properties of biomimetic chalcogels through synthetic control of the composition, while retaining both structural and functional properties, illustrates the chalcogels' flexibility and potential in carrying out useful electrochemical and photochemical reactions.

Open framework metal chalcogenide solids, with pore sizes in the nano- and mesoscale, are of potentially broad technological and fundamental interest in research areas ranging from optoelectronics to the physics of quantum confinement1,2. Although there have been significant advances in the design and synthesis of mesostructured silicas3,4, the construction of their non-oxidic analogues still remains a challenge. Here we describe a synthetic strategy that allows the preparation of a large class of mesoporous materials based on supramolecular assembly of tetrahedral Zintl anions [SnSe4]4- with transition metals in the presence of cetylpyridinium (CP) surfactant molecules. These mesostructured semiconducting selenide materials are of the general formulae (CP)4-2xMxSnSe4 (where 1.0 < x < 1.3; M=Mn, Fe, Co, Zn, Cd, Hg). The resulting materials are open framework chalcogenides and form mesophases with uniform pore size (with spacings between 35 and 40 A). The pore arrangement depends on the synthetic conditions and metal used, and include disordered wormhole, hexagonal and even cubic phases. All compounds are medium bandgap semiconductors (varying between 1.4 and 2.5 eV). We expect that such semiconducting porous networks could be used for optoelectronic, photosynthetic and photocatalytic applications.

N2O decomposition was examined over a series of Al2O3-Fe2O3 mixed oxidic solids with composition ranging from 0 to 100% of Fe2O3. The catalytic activity of the solids runs parallel to the number of atoms of iron in the Al2−x FexO3 solid solution phase. Two compensation effects are present. The first corresponds to catalysts rich in alumina, and the second one to catalysts rich in hematite.

A series of Al2O3-Fe2O3 mixed oxidic solids with composition ranging from 0 to 100% of Fe2O3 were prepared and examined for structural characteristics. XRD diagrams showed the presence of α-Al2O3 and hematite phases. The analysis of Mossbauer spectra revealed the existence of two iron containing phases. The specific surface area of the mixture decreases by the addition of iron and depends on the crystal phases of the mixture.

Polycrystalline Fe2BO4 was prepared by solid state reactions and its electronic and magnetic properties were investigated by Mossbauer spectroscopy and magnetization measurements. The Mossbauer spectra of Fe2BO4 below 270 K indicate the presence of Fe2+ and Fe3+ sites in the structure, in a ratio 1 : 1. Above this temperature electron delocalization sets in between the divalent and trivalent iron ions and Fe2.5+ states are observed. The temperature dependence of the Mossbauer spectra and magnetization measurements clearly show the onset of magnetic order below 155 K.

Polycrystalline Fe2 BO4 prepared by solid-state reaction was investigated over a wide temperature range using Mossbauer spectroscopy and magnetization and resistivity measurements. The Mossbauer data below 270 K reveal four iron sites (two Fe2+ and two Fe3+ ) in a 1:1:1:1 ratio. Above this temperature, electron delocalization sets in between the divalent-trivalent iron ions and up to 400 K both delocalized and localized iron states are observed. The magnetization and Mossbauer data indicate that this oxoborate mixed-valence system is an L-type ferrimagnet below Tc = 155 K, with the iron atoms in each sublattice having different point symmetries and different magnetic interactions. The resistivity data show the first-order nature of the charge-ordering transition (Tco = 316 K).

Five adducts of general formula Me2SnCl2L2 [L = IQNO(isoquinoline-N-oxide), 4-C1QNO, 4-MeQNO, 6-MeOQNO (6-methoxyquinoline-N-oxide) and 4-PhPyNO (4-Phenylpyridine-Af-oxide)] have been prepared by the addition of L to chloroform solutions of Me2SnCl2. The adducts have been characterized by analysis and spectroscopic (1R, 1H, 13C and Mossbauer) data. Structural predictions were derived from 119Sn NMR parameters such as 1 J(119Sn-13C) and 2 J(119Sn-1H). The single crystal diffraction study of the adduct Me2SnCl2(4-PhPyNO)2 shows the metal to be six-coordinate inan all trans-octahedral configuration; Sn-O and Sn-CI distances are 2.227(2) and 2.5774(9)A, respectively, and the CH3-Sn-CH3 bond angle is 180.0°.