Mössbauer studies on thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates

Thermal decomposition of some alkali tris (malonato) ferrate (III) tetrahydrates, i. e. M₃ [Fe(CH₂C₂O₄)₃]·4H₂O (M=Na, K) has been studied in the temperature range of 433–973 K in static air atmosphere using Mössbauer, IR and TG-DTG-DTA techniques. Mössbauer spectra are reported at different stages to study the mechanism of decomposition. The anhydrous complex decomposed into -Fe₂O₃ of varying particle sizes and alkali metal malonate/carbonate in successive stages. In the final stage of remixing of cations, a solid state reaction between -Fe₂O₃ and alkali metal carbonate/oxide gives fine particles of the respective ferrites at temperatures lower than for oxalate precursor or even for ceramic method. Thermal stability obeys the order: sodium > potassium > lithium tris(malonato) ferrate (III).     

Magnetic microspheres modified with Ti(IV) and Nb(V) for enrichment of phosphopeptides

Magnetic microspheres (Fe₃O₄) were coated with polydopamine (PDA) and loaded with the metal ions Ti(IV) and Nb(V) to give a material of type Fe₃O₄@PDA-Ti/Nb. It is shown to be useful for affinity chromatography and for enrichment of phosphopeptides from both standard protein solutions and real samples. For comparison, such microspheres loaded with single metal ions only (Fe₃O₄@PDA-Ti and Fe₃O₄@PDA-Nb) and their physical mixtures were also investigated under identical conditions. The binary metal ion-loaded magnetic microspheres display better enrichment efficiency than the single metal ion-loaded microspheres and their physical mixture. Both multiphosphopeptides and monophosphopeptides can be extracted. The Fe₃O₄@PDA-Ti/Nb microspheres exhibit ultra-high sensitivity (the lowest detection amount being 2 fmol) and selectivity at a low mass ratio such as in case of β-casein/BSA (1:1000).

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Graphical abstract Magnetic microspheres (Fe₃O₄) were coated with polydopamine (PDA) and loaded with the metal ions Ti(IV) and Nb(V) to give a material of type Fe₃O₄@PDA-Ti/Nb. Results showed its great potential as an affinity probe in phosphoproteome research due to rapid magnetic separation of phosphopeptides, ultrahigh sensitivity and selectivity, and remarkable reusability.

     

Mössbauer study of the thermal decomposition of alkali dihydroxo tetrapropionato ferrates(III)

Thermal decomposition of alkali dihydroxo tetrapropionato ferrates(III), M₃[Fe(C₂H₅COO)₄(OH)₂]xH₂O (M=Li, Na, K) has been studied upto 973 K. The complexes were calcined isothermally at various temperatures i. e., 473, 573, 773 and 973 K. The intermediates/products have been characterized by Mössbauer, infrared spectroscopies and XRD powder diffraction. The anhydrous complexes directly decompose to give -Fe₂O₃ and alkali metal carbonate without undergoing reduction to iron(II) moiety. An increase in the particle size and internal magnetic field of -Fe₂O₃ has been observed with increasing decomposition temperature. At higher temperature (973 K) MFeO₂ is formed as the final thermolysis product due to a solid state reaction between -Fe₂O₃ and alkali metal carbonate.     

Physico-chemical Studies on Thermal Decomposition of Alkali Tris(maleato)ferrates(III)

The thermal decomposition of alkali tris(maleato)ferrates(III), M₃ [Fe(C₂ H₂ C₂ O₄ )₃ ] (M =Li, Na, K) has been studied isothermally and non-isothermally employing simultaneous TG-DTG-DTA, XRD, Mössbauer and IR spectroscopic techniques. The anhydrous complexes decompose in the temperature range 215–300°C to yield Fe(II)maleate as an intermediate followed by demixing of the cations forming α-Fe₂ O₃ and alkali metal maleate/oxalate in successive stages. In the final stage of remixing of the cations (430–550°C) a solid state reaction occurs between α-Fe₂ O₃ and alkali metal carbonate leading to the formation of fine particles of respective ferrites. The thermal stabilities of the complexes have been compared with that of alkali tris(oxalato)ferrates(III).     

An intrinsic synthesis parameter governing the crystallization of silico(zinco)aluminophosphate molecular sieves

One of the most fundamental but yet unanswered questions in the synthesis of zeolites and zeolite-like materials is whether or not any parameter controlling the microporosity of the crystallized product from synthesis mixtures with feasible chemical compositions exists. Here we report that an experimentally optimized parameter (ca. 3.3 ≤ MOH/P₂O₅ ≤ 5.3, where M is alkali metal ions) is the criterion bringing about the successful formation of various high-charge-density silicoaluminophosphate (SAPO) and zincoaluminophosphate (ZnAPO) molecular sieves, without the aid of organic structure-directing agents. The materials obtained using this empirical concept include SAPO molecular sieves with CHA and LTA topologies, as well as a SAPO FAU/EMT intergrowth, and ZnAPO ones with CZP and SOD topologies. This study demonstrates the existence of an essential factor determining not only phase selectivity but also microporosity (0.3–2 nm) in the synthesis of zeotypes with charged frameworks which may offer interesting opportunities for more efficiently producing novel zeolite structures and/or compositions.

The existence of an essential parameter (ca. 3.3 ≤ MOH/P₂O₅ ≤ 5.3, where M is alkali metal ions used as structure-directing agents) determining phase selectivity and microporosity in the synthesis of zeotypes with charged frameworks is demonstrated.     

Interaction between Co2P4O12 and alkali metal nitrate (chloride) melts

Reactions between Co₂P₄O₁₂ and alkali metal nitrate (chloride) melts was studied in the temperature range 350–400°C (800–850°C) at different phosphate/melt ratios. The effect of the nature of an alkali metal and the ratio between the components in the Co₂P₄O₁₂-M^INO₃ (M^ICl) system on composition of the reaction products was established. The resulting crystalline phases (NaCoPO₄, Na₄Co₃(PO₄)₂P₂O₇, Na₉Co₃(PO₄)₅ and KCoPO₄) were studied by X-ray powder diffraction, IR and electron spectroscopy, and scanning electron microscopy. The features of transformation of the Co₂P₄O₁₂ framework into KCoPO₄ under the effect of excessive alkali metal ions in the melt are discussed.     

Iron(II) complexes of imidazoline-2-thiones: the crystal structure of dichlorobis(1-methylimidazoline-2-thione)iron(II)

Summary Imidazoline-2-thione (imtH ₂) and 1-methylimidazoline-2-thione (mimtH) react with FeCl₂·4H₂O in rigorously anhydrous media producing complexes of general formula Fe(LH)₂Cl₂.Infrared and electronic spectra as well as room temperature magnetic moments are consistent with mononuelear, pseudotetrahedral species. The crystal structure of [Fe(mimHH)₂Cl₂] confirms this arrangement. The complex crystallises in a triclinic unit cell (a=7.376(2),b=7.595(2),c=15.043(4) Å. =76.80(1)°, =79.60(1)°, =61.90(1)°; V=721.13 ų; space group=P1, Z=2). Final conventional R from 2267 observed data (F >4(F)) is 0.0271. Average bond lengths are 2.353 Å (Fe–S) and 2.265 Å (Fe–Cl). Angles at the metal range from 91.5(1)° to 114.5(1)°.Thermal degradation of the complexes in flowing air involves sequential loss of halogen and ligand with -Fe₂O₃ as the final product. The decomposition is exothermic in flowing dinitrogen.     

Physico-chemical studies on thermal analysis of cobalt hexa(formato)ferrate(III) decahydrate

Thermal decomposition of cobalt hexa(formato)ferrate(III) decahydrate, Co₃[Fe(HCOO)₆]₂. 10H₂O, has been studied up to 973 K in static air atmosphere, employing TG, DTG, DSC, XRD, ESR, Mössbauer and infrared spectroscopic techniques. Dehydration occurs in two stages in the temperature range of 340–430 K. Immediately after the removal of the last water molecule the anhydrous complex undergoes decomposition till -Fe₂O₃ and cobalt carbonate are formed at 588 K. In the final stage of remixing of cations, a solid state reaction between -Fe₂O₃ and cobalt carbonate leads to the formation of CoFe₂O₄ at a temperature (953 K) much lower than for the ceramic method. A saturation magnetization value of 2310 Gauss of ferrite (CoFe₂O₄) shows its potential to function at high frequencies.     

Effects of lithium salt and poly(4‐vinyl phenol) on crystalline and amorphous phases in poly(ethylene oxide)

Effects of a strong‐interacting amorphous polymer, poly(4‐vinyl phenol) (PVPh), and an alkali metal salt, lithium perchlorate (LiClO₄), on the amorphous and crystalline domains in poly(ethylene oxide) (PEO) were probed by differential scanning calorimetry (DSC), optical microscopy (OM), and Fourier transform infrared spectroscopy (FTIR). Addition of lithium perchlorate (LiClO₄, up to 10% of the total mass) led to enhanced T_g's, but did not disturb the miscibility state in the amorphous phase of PEO/PVPh blends, where the salt in the form of lithium cation and ClO anion was well dispersed in the matrix. Competitive interactions between PEO, PVPh, and Li⁺ and ClO ions were evidenced by the elevation of glass transition temperatures and shifting of IR peaks observed for LiClO₄‐doped PEO/PVPh blend system. However, the doping distinctly influenced the crystalline domains of LiClO₄‐doped PEO or LiClO₄‐doped PEO/PVPh blend system. LiClO₄ doping in PEO exerted significant retardation on PEO crystal growth. The growth rates for LiClO₄‐doped PEO were order‐of‐magnitude slower than those for the salt‐free neat PEO. Dramatic changes in spherulitic patterns were also seen, in that feather‐like dendritic spherulites are resulted, indicating strong interactions. Introduction of both miscible amorphous PVPh polymer and LiClO₄ salt in PEO can potentially be a new approach of designing PEO as matrix materials for electrolytes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3357–3368, 2006     

Electrochemical behaviour of solid lithium cobaltate (LiCoO2) and lithium manganate (LiMn2O4) in an aqueous electrolyte system

Lithium cobaltate (LiCoO₂) and lithium manganate (LiMn₂O₄) were synthesized by self-propagating high-temperature combustion and their phase purity and composition were characterized by X-ray diffraction and inductively coupled plasma spectroscopy. These transition metal oxides were mechanically immobilized on the surface of paraffin-impregnated graphite electrodes and their cyclic voltammetric behaviour in aqueous alkali electrolytes was examined. It was shown that both the oxides undergo proton insertion upon the reduction of Co³⁺ to Co²⁺ in LiCoO₂ and Mn⁴⁺ to Mn³⁺ in LiMn₂O₄, while they deintercalate protons on the reverse oxidation. Scanning electron microscopy reveals spherical LiCoO₂ particles with a very narrow size distribution. Energy dispersive X-ray detection proved the absence of metal cation intercalation. Received: 30 August 1999 / Accepted: 11 November 1999     

Cs5[Na{W4N10}]: The first framework nitridotungstate(VI)

Cs₅[Na{W₄N₁₀}] was prepared from a mixture of NaNH₂, CsNH₂ and tungsten powder (molar ration 1 : 10 : 4) at 700°C in autoclaves. After the reaction is finished the nitride is embedded in an alkali metal matrix. Dark red crystals were isolated by washing out the alkali metal with liquid ammonia at room temperature. The structure of Cs₅[Na{W₄N₁₀}] was solved by X-ray single crystal data: I4₁ (No. 80), Z = 4, a = 13.926(3) Å, c = 8.723(3) Å, Z(F) ≥ 3σ(F) = 1535, Z(Variables) = 63, R/R_w = 0.040/0.052. The compound is highly sensitive against moisture giving oxotungstates and ammonia. It contains a framework of tetrahedra [WNN_3/2^1.5?]. Sodium shares four terminal nitrogen ligands. Including sodium a distorted, β-cristobalite type arrangement [Na{W₄N₁₀}^5?] results. It contains caesium in all interstices formed by twelve nitrogen ligands in so-called Friauf polyhedra.     

Alkali metal ion-selective electrodes based on relevant alkali metal ion doped manganese oxides

Potentiometric properties of manganese oxides doped with alkali metal ions (Na⁺, K⁺, Rb⁺ and Cs⁺), which were prepared by heating mixed solutions (starting solution) of each alkali metal and Mn²⁺ ions, were examined. Electrodes based on mixed phases of Nao₄₄MnO₂/Mn₂O₃ and hollandite KMn₈O₁₆/M₂O₃ found by X-ray powder diffraction (XRD) exhibited Na⁺- and K⁺-selective responses with a near-Nernstian slope, respectively, when the molar ratio of alkali metal ion to Mn²⁺ ion in the starting solution was 0.1. When no alkali metal ions were added in the manganese oxide films, no significant potentiometric response was observed to any alkali metal ions. The selectivity coefficients of these electrodes were = 6.7 × 10^–2, = 7.1 × 10^–3, < 9 × 10^–4 and < 9x 10^–4 for the Na_0.44MnO₂/Mn₂O₃, and <4 × 10^–4 <4x 10^–4, =60 × 10^–2 ×10^–4, < 4 × 10^–4, for the KMn₈O₁₆/Mn₂O₃, respectively. Electrodes based on manganese oxides made from mixed solutions of Rb⁺/Mn²⁺ and Cs⁺/Mn²⁺ also responded to the respective primary ions, that is, Rb⁺ and Cs⁺ ions, although XRD patterns for the manganese oxides thus made did not show any peaks except for Mn₂O₃ (bixbyite); it was concluded in these cases that some amorphous type manganese oxides were formed in the Rb⁺/Mn²⁺ and Cs⁺/Mn²⁺ systems and they responded to the respective ions. Conditioning of these electrodes in an aerated indifferent electrolyte solution, 0.1M tetramethylammonium nitrate (TMA-NO₃), for relatively long time, typically more than 2 hours, was found to be a prerequisite for near-Nernstian response to the respective alkali metal ions. During this electrode conditioning, vacant sites (template) suitable in size for selective uptake of primary ions seemed to be formed by releasing the doped alkali metal ions from the solid phase into the adjacent electrolyte solution accompanying oxidation of the manganese oxide film.     

The thermolysis of zinc bis(citrato)ferrate(III) dodecahydrate

The thermolysis of zinc bis(citrato)ferrate(III)dodehydrate has been investigated from ambient temperature to 600 °C using various physico-chemical techniques, i.e., simultaneous TG-DTG-DTA, XRD, Mössbauer and I.R. spectroscopy. After dehydration at 200 °C, the anhydrous complex undergoes oxidative decomposition to yield -Fe₂O₃ and ZnO at 350 °C. Subsequently, the cations remix to yield fine particles of zinc ferrite, ZnFe₂O₄ as a result of solid state reaction between -Fe₂O₃ and ZnO at a temperature (450 °C) much lower than for ceramic method.     

Mechanochemical synthesis of iron-alumina (75 vol%) nanocermets

Nanocomposites -Al₂O₃-Fe containing 75 vol% Al₂O₃ have been obtained by reaction milling, in a vibratory ball mill, a stoichiometric excess of alumina with aluminum and hematite. The kinetics of synthesis of the nanocomposite has been studied for milling times between 15min. and 8h. The reduction reaction is completed in about 2h with formation of -Al₂O₃, iron, hercynite (FeAl₂O₄) and clusters of Fe in alumina. The reaction rate appears moderated by the alumina excess.     

Mo2(O2CPh)6(PEt3)2, the second example of bridging Y11-02CR for dimolybdenum (III) compounds

From the reaction or Mo₂Cl₆(THF)₃ with excess of NaO₂CPh and PEt₃ in THF three types of crystals have been obtained and recrystallized in CH₂Cl₂. They are brown compound Mo₂(O₂CPh)₆(PEt₃)2·2CH₂Cl₂ (1), yellow-Mo₂(O₂CPb)₄ (2), and black Mo₄O₆(O₂CPh)₆(PEt₃)₂.CH₂Cl₂ (3). When a strict ratio of MO₂Cl₆(THF)₃:NaO₂CPh = 1:2 was applied, Mo₂(O₂CPh)₄(THF)₂, (4) was the only compound separated from the THF reaction mixture. Their structures have been determined by X-ray crystallography. There are three coordination modes of benzoate in 1: bridging ²-O₂CPh, bridging ¹-O₂CPh and terminal O₂CPh groups. Compound 2 is chemically well known, but was found to pack differently from the previously reported structure. Mo₄O₆(O₂CPh)₆(PEt₃)₂·CH₂C1₂ (3) is a mixed-valence Mo (IV, V) tetranuclear compound in a butterfly arrangement. A molecule of 4 is actually a MO₂(O₂CPh)₄ molecule with two THIF molecules axially coordinating to the molybdenum atoms. The crystallographic data for these compounds are as follows: 1, triclinicPl witha = 11.612(3) Å, b = 11.970(2) Å,c=12.135(3) Å,=95.55(2)°,=117.51(2)°,98.84(2)°,V=l450.8(7) ų,Z=1,R=0.0673, and R _w ,=0.0936; 2, monoclinicP2₁/n witha = 14,437(2) Å,b=5.6168(7) Å,c=15.979(3) Å,=93,93(l)°,V=1292.7(4) ų,Z=2,R=0.0217, and R_w=0.0352; 3, trigonal (hexagonal setting)R3¯ witha=28.83(4) Å,c=44.98(2) Å,V=323570(10) ų,Z=18,R=0.067, andwR2=0203; 4 monoclinicP2₁/c witha=9.456(4) Å,b=17.757(8) Å,c=10.887(3) Å,=109.63(2)°,V=1722(2)ų Z=2,R=0.0330, andR _w = 0.0451.     

Mössbauer study of sodium ferrates(IV) and (VI)

Sodium ferrates(IV) and (VI) were synthesized by the reaction between Fe₂O₃ and Na₂O₂ in a dry oxygen stream. The Mössbauer data for the obtained samples are presented (for Na₂FeO₃–=0.18(2) mm/s; for Na₄FeO₅–=–0.54(2) mm/s). It was shown that pure K₂FeO₄ and Cs₂FeO₄ can be obtained by heating Fe₂O₃ with apropriate alkali metal peroxides.     

Ein neuartiges Polyoxocobaltat(II)‐Anion in Rb2Co2O3

A New Polyoxocobaltate(II) Anion in Rb₂Co₂O₃ Rb₂Co₂O₃ was prepared via the azide/nitrate route. Mixtures of the precursors Co₃O₄, RbN₃ and RbNO₃ in the molar ratios 6:17:1 were heated in a special regime up to 450 °C and annealed at this temperature for 50 h in silver crucibles. Single crystals have been grown by subsequent annealing of prepared powder at 450 °C for 500 h in silver crucibles, which were sealed in glass ampoules under dried Ar. According to the X‐ray analysis of the crystal structure (Pnma, Z = 8, 11.729(2), 6.058 (1), 8.004(1) Å) cobalt is trigonal planar coordinated by oxygen atoms. The CoO₃‐units share through all corners and build up an infinite two‐dimensional Co₂O₃‐network.     

A metal-organic framework nanocomposite made from functionalized magnetite nanoparticles and HKUST-1 (MOF-199) for preconcentration of Cd(II), Pb(II), and Ni(II)

The author describes the preparation of a magnetic metal organic framework of type MOF-199 containing magnetite (Fe₃O₄) nanoparticles carrying covalently immobilized 4-(thiazolylazo) resorcinol (Fe₃O₄@TAR). This material is shown to represent a viable sorbent for separation and preconcentration of Cd(II), Pb(II), and Ni(II) ions. Box-Behnken design was applied to optimize the parameters affecting preconcentration. Following elution with 0.6 mol L^?1 EDTA, the ions were quantified by FAAS. The capacity of the sorbent ranged between 185 and 210 mg g^?1. The limits of detection are 0.15, 0.40, and 0.8 ng mL^?1 for Cd(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations are <8.5 %. The method was successfully applied to the rapid extraction of trace amounts of these ions from sea food and agri food.

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Graphical abstract (a) A schematic diagram of Fe₃O₄ functionalization by TAR (4-(thiazolylazo) resorcinol). (b) The schematic illustration of the magnetic metal organic framework-TAR nanocomposite. H₃BTC: benzene-1,3,5-tricarboxylic acid; TEA: triethylamine; 3-CPS: 3-chloropropyl triethoxysilane.

     

Characterization of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) electrolytes complexed with different lithium salts

Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) gel electrolytes comprising a combination of plasticizers, ethylene carbonate (EC) and propylene carbonate (PC) and lithium salt LiX have been prepared using the solution casting technique in an argon atmosphere. The prepared electrolytes were subjected to ionic conductivity, compatibility with lithium metal anode and thermogravimetric (TG)/differential thermal analysis (DTA). The membranes, which possess lithium salt, LiBF₄ exhibited maximum conductivity and on contrary it undergoes severe passivation with lithium metal. All these membranes are found to be stable thermally about 70 °C.