Mössbauer study of paramagnetic relaxation effect in mixed crystals: High spin Fe3+ compounds diluted in diamagnetic hosts

The⁵⁷Fe Mössbauer spectra were measured in mixed crystals with different types of chemical bonding and crystal structure, i.e., (Fe,Al)(acac)₃, (Fe,Co)(acac)₃, K₃[(Fe,Al)(ox)₃]3H₂O, and NH₄(Fe,Al)(SO₄)₂12H₂O. The broadening of Mössbauer linewidth with increasing Fe³⁺–Fe³⁺ distance became less enhanced in the order: (Fe,Al)(acac)₃>(Fe,Co)(acac)₃, or K₃[(Fe,Al)(ox)₃]3H₂O>(Fe,Al)(acac)₃>NH₄(Fe,Al)(SO₄)₂12H₂O. Furthermore, it was found that the broadening of the linewidth was larger in neat tris (-diketonato) iron(III) complexes than in (Fe,Al)(acac)₃. Based on these results, the determining factors of the paramagnetic relaxation time other than Fe³⁺–Fe³⁺ distance and temperature were examined in terms of the Mössbauer linewidth as an indicator.     

Effect of sulfate additives on the 60Co gamma ray induced decomposition of lanthanum,europium and terbium nitrates in solid state

Gamma radiolysis of binary mixtures of La(NO₃)₃·6H₂O, Eu(NO₃)₃·6H₂O and Tb(NO₃)₃·6H₂O along with their respective sulfates have been studied over a wide range of absorbed doses up to 500 kGy. Radiolytic decomposition of the nitrate salts is affected by the concentration of the sulfate in the binary mixture as well as on the absorbed dose. G(NO₂⁻) values calculated on the basis of electron fraction of the nitrate salt in the binary mixture are enhanced by 10²–10³ times at >90 mol% of the sulfate additive. A study of binary mixtures of lanthanum nitrate with other mono-, bi-, tri- and tetra-valent sulfate additives shows that G(NO₂⁻) values are also affected by the nature and oxidation state of the cation including electron configuration. ESR and TL measurements suggest the formation of radical species, which may interact with the radical species of nitrate (NO₃²⁻, NO₂ etc.) causing enhanced decomposition by energy transfer. A possible mechanism of decomposition has been suggested. Anomalous behavior of Eu(NO₃)₃·6H₂O has been correlated with the electronic configuration and +2 oxidation state of Eu.     

Structural and spectroscopy studies of complexes of the uranyl ion with 2,2′-bipyridine-N,N′-dioxide

2,2′-Bipyridine-N,N′-dioxide (bypO₂ = L) complexes of the composition [UO₂(bypO₂)₂(NO₃)₂]·2H₂O (UO₂–L₂–NO₃), [UO₂(bypO₂)₂H₂O](ClO₄)₂ (UO₂–L₂–ClO₄) and [UO₂bypO₂(H₂O)₂SO₄] (UO₂–L–SO₄) have been prepared by the reactions of the respective hydrated uranyl salts with the bypO₂ ligand in water. The structures of the complexes were elucidated using elemental and thermal analyses, IR and luminescence spectroscopy as well as luminescence lifetime measurements. The IR spectra show that the bonding between uranium and bypO₂, as well as uranium and water or a counter ion (NO₃⁻ and SO₄²⁻) is formed. The nitrate or sulfate groups coordinate to the central metal ions in a monodentate manner. From TG–DTA curves, the nature of the water molecules present in the complexes and the decomposition temperature of the dehydrated uranyl complexes were determined. The thermal stability of the anhydrous uranyl complexes increases in the series: (UO₂–L₂–NO₃) < (UO₂–L₂–ClO₄) < (UO₂–L–SO₄). All the compounds show green-yellow intense luminescence. The main fluorescence bands and the emission lifetimes in these complexes were determined. The luminescence spectra of all the prepared complexes differ from each other with respect to their peak maxima positions. The luminescence lifetimes also vary. The structure of the (UO₂–L–SO₄) complex was determined by X-ray single-crystal analysis.     

Morphological studies of the mechanism of pit growth of pure aluminum in sulfate ion- or nitrate ion-containing 0.1 M NaCl solutions

The mechanism of pit growth of pure aluminum (Al) in sulfate ion (SO₄ ^2–)- or nitrate ion (NO₃ ^–)-containing 0.1 M sodium chloride solutions has been studied in terms of the morphological changes of artificial pits using potentiodynamic polarization experiment, potentiostatic current transient technique and optical microscopy. The increase in SO₄ ^2– and NO₃ ^– ion concentrations in NaCl solution raised the pitting potential E _pit of pure Al, which is ascribed to the impediment to pit initiation on pure Al by the addition of SO₄ ^2– or NO₃ ^– ions. From the potentiostatic current transients of artificial pits in aqueous 0.1 M NaCl solution, the average value of the pit current was observed to increase with increasing SO₄ ^2– ion concentration, whereas that value of the pit current in the presence of NO₃ ^– ions increased up to ca. 0.4 M NO₃ ^– ion concentration and then decreased abruptly with increasing NO₃ ^– ion concentration. From observations of the morphologies of the pits, it appears that the pit grows preferentially in the lateral direction or in the downward direction by adding SO₄ ^2– or NO₃ ^– ions to aqueous 0.1 M NaCl solution, respectively. Based upon the experimental results, two different pit growth mechanisms by anion additives can be proposed: (1) pit growth by the preferential attack of both SO₄ ^2– and Cl^– to the pit wall in SO₄ ^2–-containing solutions; (2) pit growth by the creation of an aggressive environment at the pit bottom up to 0.4 M NO₃ ^– ion concentration due to the lower mobility of NO₃ ^– than Cl^– in NO₃ ^–-containing solutions. Electronic Publication     

Anion exchange studies of aluminium and iron(III) in malonate solutions: Separation from mixtures

Summary Systematic anion exchange studies of aluminium and iron(III) in malonate solutions were carried out. Aluminium and iron form negatively charged complexes with malonic acid at pH 4.5. The malonate complexes can be adsorbed on a column (1.4×20 cm) of Dowex 21K. Various reagents (hydrochloric, sulfuric and nitric acids; ammonium chloride, bromide, sulfate and nitrate; and sodium chloride and nitrate) were tested as eluants. The efficiency of the eluants was evaluated in terms of elution constant, volume distribution coefficient and peak elution volume. Methods were developed for the separation of aluminium or iron from a large number of elements by taking advantage of the fact that certain elements form weaker or stronger malonate complexes as compared to those of aluminium or iron. The method was applied to the analysis of aluminiumbased alloy.

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Zusammenfassung Systematische Untersuchungen des Verhaltens von Al(III) und Eisen(III) in Malonatlösungen gegenüber Anionenaustauschern wurden durchgeführt. Beide Metalle bilden mit Malonsäure negativ geladene Komplexe bei pH 4,5. Diese werden in einer Säule (1,4×20 cm) von Dowex 21K adsorbiert. Verschiedene Reagenzien (HCl, H₂SO₄, HNO₃; NH₄Cl, NH₄Br, (NH₄)₂SO₄, NH₄NO₃; NaCl und NaNO₃) wurden als Elutionsmittel geprüft. Deren Wirksamkeit wurde mit der Elutionskonstante, dem Verteilungskoeffizienten und der Peakhöhe des Elutionsvolumens gekennzeichnet. Trennungsmethoden für Al oder Fe von vielen anderen Elementen ergaben sich daraus, daß manche Elemente vergleichsweise schwächere bzw. stärkere Malonatkomplexe bilden. Die Methode wurde zur Analyse von Aluminiumlegierungen verwendet.

     

Effect of Inorganic Ions on the Oxidation of Methyl Violet with Gliding Arc Plasma Discharge

Gliding arc discharge process was used for the treatment of methyl violet wastewater. First, the intermediate products were studied by gas chromatography coupled with mass spectrometry and Fourier transform infrared spectrometry, and ultraviolet–visible spectrometer. Second, the effects of inorganic anions including chloride (Cl^?), carbonate (CO₃ ^2?), sulfate (SO₄ ^2?), phosphate (PO₄ ^3?), nitrate (NO₃ ^?) on the degradation efficiency of methyl violet were examined. The research results indicated that hydroxyl radicals attacked carbon atom that situated in the center of dye molecule, and the conjugating structure of methyl violet was destroyed, and dye was degraded and decolored, so a possible degradation pathway was proposed by the analysis of intermediate products detected. The methyl violet degradation rate decreased with increasing anions concentrations, and their order of sequence according to the inhibition reaction was CO₃ ^2? > Cl^? > SO₄ ^2? > NO₃ ^?.     

The reactivity of sulfur dioxide with transition metal complexes containing 4-cyanopyridine- and 3-pyridylcarbinol-N-oxide: the high temperature isolation of a manganese(II) iodide SO2-adduct

The reactivity of metal complexes M(RPyO)_nX₂(H₂O)_m (RPyO=4-cyanopyridine-N-oxide or 3-pyridylcarbinol-N-oxide; M=Mn, Co, Cu; X=Cl, Br, I, NO₃; n=2–4 and m=0–3) with SO₂ has been studied in toluene slurries and in the solid state at room temperature and in the solid state at high temperature. Only the metal iodide precursors containing 4-CNPyO reacted with SO₂ in the solid state or in a toluene slurry but never above room temperature. Among the precursors containing 3-HOH₂CPyO, only the copper metal complexes interact with SO₂ at room temperature in toluene slurries. Surprisingly, Mn(3-HOH₂CPyO)₂I₂(H₂O) reacted with SO₂ at 210°C, whereas the metal complex was unreactive at room temperature. Likewise, Cu(3-HOH₂CPyO)₂(NO₃)₂ reacted at 100°C, the SO₂ being oxidised to sulfate, displacing the nitrate group, but not at room temperature.     

Sorption—desorption studies of anionic dyes on alumina pretreated with acids

Sorption—desorption behaviour of the anionic dyes naphthol blue-black (NB) and lissamine green ‘BN’ (LG) on chromatographic alumina, pretreated with mineral acids, is described. Alumina samples of surface-phase pH 1.0–8.0 were prepared and studied for their sorption behaviour. The sorption was found to vary with surface pH of the substrate and acid used for pretreatment. Quantitative sorption was shown at pH ⩽ 4.0 (NB) and pH ⩽ 3.5 (LG) on Al₂O₃ treated with HNO₃ [Al₂O₃(n)], and maximum sorption occurred at pH 5.0 (NB) and pH 5.5 (LG) on Al₂O₃ treated with H₂SO₄ [Al₂O₃(s)] and pH 2.5 (NB) and pH 3.0 (LG) on Al₂O₃ treated with H₃PO₄ [Al₂O₃(p)]. Variation in sorption with time (10 min-72, h), temperature (30–60°C) and regeneration of the substrates with aqueous electrolytes is also reported. Desorption efficacy of anions was in the order: PO³⁻₄ > SO²⁻₄ > NO⁻₃. The acid-treatment, and hence the specifically adsorbed anions (NO⁻₃, SO²⁻₄, PO³⁻₄), appears to modify the sorption properties of alumina significantly. It appears that the controlling force for adsorption is predominantly ion exchange. A few synthetic mixtures of the dyes were separated by column chromatography, using inorganic electrolytes as eluents.     

Oxonitrates VO(NO<Subscript>3</Subscript>)<Subscript>3</Subscript> and MoO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript> and nitronium and nitrosonium nitratometallates as nitrating agents

Dissolution of vanadium in anhydrous HNO₃ followed by exposure of the solution in a dessicator over P₂O₅ gave liquid vanadyl trinitrate (I). The X-ray diffraction analysis of I was carried out for a single crystal grown on cooling the liquid in a sealed capillary. The structure is composed of VO(NO)₃ molecules in which the V atom has an unusually high C.N. 7; it coordinates the terminal O atom and three bidentate nitrate groups to form a distorted pentagonal bipyramid as the coordination polyhedron with the terminal O atom occupying one axial vertex. Using the GAMESS program package, ab initio calculation of the structure of VO (NO₃)₃ in the liquid phase was carried out. It was shown that in all three physical states, vanadyl trinitrate retains its molecular structure almost invariable. Toluene and naphthalene nitration using I and (NO₂)[Fe(NO₃)₄], NO[Cu(NO₃)₃], (NO)_3/4(NO₂)_1/4[Zr(NO₃)₅], and MoO₂(NO₃)₂ proceeds at high rates at low temperatures to give an unusually high para-nitrotoluene percentage in the products as compared with the ortho-isomer. The activity of the studied compounds in the nitration of naphthalene decreases in the series VO(NO₃)₃ > (NO)_3/4(NO₂)_1/4[Zr(NO₃)₅] > MoO₂(NO₃)₂.     

Solid-state reactions between alkali persulfates and oxides of corundum structure

The effects of three corundum structure oxides, α-Al₂O₃, α-Cr₂O₃, and α-Fe₂O₃, on the thermal decomposition of sodium and potassium peroxodisulfates (persulfates) under non-isothermal static air conditions and using various oxide/persulfate molar ratios, have been thermoanalytically investigated. Compounds such as Na₃Al(SO₄)₃, K₃Al(SO₄)₃, Cr₂(SO₄)₃, K₃Cr(SO₄₃, and Na₃Fe(SO₄)₃ are identified by X-ray diffractometry and conventional chemical analysis. The molar ratios as well as temperatures of the stoichiometric formation for these compounds have been established. At higher temperatures, α-Al₂O₃ acts as a promoter catalyst for the decomposition of pyrosulfate to sulfate, whereas α-Cr₂O₃ behaves as a retarder for the decomposition of persulfate. A eutectic mixture is formed between K₃Al(SO₄) and K₂SO₄ at 675°C. Also, K₃Fe(SO₄)₃ is identified as two crystalline phases.     

Mixed Complex Salt [Cu4(SCN2H4)7(NO3)](NO3)(SO4) · 3.3H2O: Synthesis and X-Ray Diffraction Analysis

The complex salt [Cu₄(SCN₂H₄)₇(NO₃)](NO₃)(SO₄) · 3.3H₂O was synthesized via reaction of aqueous solutions of thiourea with copper nitrate at 80°C and studied using X-ray diffraction analysis. The conditions and reasons for the partial oxidation of thiourea to sulfate ions were established. The crystals are monoclinic: a = 12.6072(7) Å, b = 15.4265(8) Å, c = 22.108(1) Å, = 120.133(6)°, space group P2₁/c, Z = 4. The crystal structure consists of [Cu₄(SCN₂H₄)₇(NO₃)]³⁺ complex cations, SO₄ ^2–, and NO₃ ^– anions, and molecules of the water of crystallization. Three types of coordination of the Cu atom were distinguished in the structure: trigonal (Cu–S 2.213–2.279 Å), tetrahedral (Cu–S 2.315–2.459 Å), and trigonal–pyramidal (3+1) (Cu–S 2.26–2.288, Cu–O 2.68 Å). The NO₃ ligand was found to be orientationally disordered.     

An absorptiometric determination of perchlorate by means of a novel coloured liquid anion exchanger

A novel liquid anion exchanger can be prepared from tetra-n-hexylammonium iodide and Erdmann's salt, (NH₄)[Co(NH₃)₂(NO₂)₄]. When a solution of this quaternary erdmannate in a suitable organic solvent (e_max = 15,700 at 355 mμ) is equilibrated with an aqueous solution of a salt, the coloured ermannate ion is displaced to a greater or less extent; the effect decreases in the order ClO₄^- > ClO₃^- > NO₃^- > Cl^- > SO₄^2- etc. The effects of changes in the organic solvent composition, of ionic strength, and of other variables on the position of equilibrium have been studied with a view to defining the optimum conditions for the absorptiometric determination of perchlorate ion (≧25 μ) in the presence of chlorate and other ions. Methods are proposed for eliminating those ions that form insoluble silver salts and to allow for the presence of substantial proportions of chlorate or nitrate ions.     

Mössbauer studies of some iron(II) complexes of cyclohexanonesemicarbazone

Summary Mössbauer studies of high-spin iron(II) complexes of the type FeL₂X₂ [L = cyclohexanonesemicarbazone (CHSC); X = Cl, NO₃, 0.5 SO₄, NCS] have been carried out at room and at liquid nitrogen temperature. The results reveal doublet ground states for Fe(CHSC)₂Cl₂ and Fe(CHSC)₂(NO₃)₂ and singlet ground states for Fe(CHSC)₂SO₄ and Fe(CHSC)₂(NCS)₂.     

Effect of iron salt on the color removal of water containing the azo-dye reactive blue 69 using photo-assisted Fe(II)/H2O2 and Fe(III)/H2O2 systems

The effect of chloride, sulfate and nitrate anions on the color removal of water containing the azo-dye reactive blue 69 (RB69) in acidic solution, by using photo-assisted Fenton process with Fe(II)/H₂O₂ and Fe(III)/H₂O₂ systems was investigated. Experiments were conducted in a batch reactor irradiated during 5 h with a domestic 15 W lamp with emission in the visible spectra. Experimental results showed color disappearance in the first 5 min of reaction in the photo-assisted process for all of the different salts, greatly enhancing the reaction rate with respect to the corresponding systems under dark conditions. The exception of the general trend was the Fe₂(SO₄)₃/H₂O₂/UV system, where the decolorization process is slower probably because the oxidative species generated by rupture of Fe(III)–peroxo complexes are less reactive. Total organic matter depletion and mineralization of the effluent were also tested during the experimental runs by means of total organic carbon (TOC) showing that, for most of the photo-assisted experiments high mineralization was reached after 3 h of reaction.     

Glass formation in the Al<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>-Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system

Glass formation boundaries in the Al₂(SO₄)₃-Al(NO₃)₃-H₂O system were determined. IR spectra were studied. Schemes of structural rearrangements within the boundaries of a second glass formation region in the Al(NO₃)₃-H₂O binary subsystem are suggested. A structure is suggested for glassy Al(NO₃)₃H₂O.     

Fe–N/C nanofiber electrocatalysts with improved activity and stability for oxygen reduction in alkaline and acid solutions

Fe–N/C nanofiber (Fe–N/CNF) electrocatalysts were prepared by impregnating electrospun polyacrylonitrile nanofibers with iron nitrate (Fe(NO₃)₃) solution and subsequent heat treatment, exhibiting improved activity and stability during oxygen reduction reaction (ORR) both in 0.1 M KOH (pH?=?13) and 0.5 M H₂SO₄ (pH?=?0) electrolyte solutions. Higher treatment temperature and NH₃ atmosphere were preferred by the Fe–N/CNF catalysts, and especially the concentration of Fe(NO₃)₃ solution exerted great effects on the surface morphology, structure, and thus electrocatalytic performance of the catalysts. The Fe–N/CNFs prepared using 0.5 wt% Fe(NO₃)₃ solution showed relatively higher ORR activity in alkaline and acid solutions and better stability especially in 0.5 M H₂SO₄ solution than the catalyst without Fe, probably because Fe could promote the graphitization of the polymer-converted carbon species, enhancing the resistance to electrochemical oxidation and thus the stability of the Fe–N/CNF catalysts.     

H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

Synthesis, spectroscopic, powder X-ray diffraction and DNA binding studies on copper(II) complexes of 4,4′-diaminodiphenyl sulfone

Four new Cu(II) complexes of 4,4??-diaminodiphenyl sulfone (DDS) with different anions (chloride, sulfate, nitrate or acetate) were synthesized and characterized by elemental analysis, electronic absorption, IR, magnetic moment, thermal analysis and powder X-ray diffraction studies. It was found that the pure DDS and complex [Cu₂(DDS)₂(NO₃)₂].(NO₃)₂ (3) crystallize in orthorhombic system while the complexes [Cu₂(DDS)₂].Cl₄ (1), [Cu₂(DDS)₂].(SO₄)₂ (2), and [Cu₂(DDS)₂].(CH₃COO)₄ (4) crystallize in monoclinic system. The crystallite sizes of complexes have smaller values as compared to pure DDS. Infrared studies suggest that the coordination of NH₂ of DDS with Cu(II) ion. The binding of the complexes with calf thymus (CT) DNA was investigated by electronic absorption titration, fluorescence measurements and DNA thermal denaturation. The spectroscopic studies together with the DNA melting studies indicated that the complexes may bind to CT-DNA in a non-intercalative mode.     

Syntheses and crystal structures of SmIII and ThIV complexes with macrocyclic cavitand cucurbituril

Slow evaporation of solutions of samarium nitrate and thorium chloride in hydrochloric acid containing the macrocyclic cavitand cucurbituril (C₃₆H₃₆N₂₄O₁₂) afforded crystals of the [{Sm(H₂O)₅(NO₃)}₂(C₃₆H₃₆N₂₄O₁₂)](NO₃)₄·6.5H₂O and [{Th(H₂O)₅Cl}₂(C₃₆H₃₆N₂₄O₁₂)]Cl₆·13H₂O complexes, respectively. The [Sm(C₃₆H₃₆N₂₄O₁₂)(H₂O)₅(SO₄)][Sm(H₂O)₅(SO₄)₂]·17H₂O complex was generated upon heating (130 °C) of a mixture of samarium sulfate, cucurbituril, and water in a sealed tube. X-ray diffraction analysis demonstrated that the metal atoms in these complexes are bound to the portal oxygen atoms of the cucurbituril molecules. In addition, the portal oxygen atoms of cucurbituril are linked to the coordinated H₂O molecules via hydrogen bonds.     

Iron(III) complexes withN-Methyl-4-mercaptopiperidine

Summary Complexes of iron(III), containingN-methyl-4-mercaptopiperidine in its zwitterionic form (HRS), of stoichiometry Fe(HRS)₄XA₄ · nD, Fe(HRS)₃(BPh₄)₃ · 3DMF and (Fe(HRS)SO₄)₂SO₄ · 3MeOH · 2H₂O (X=Cl or NO₃; A=BPh₄ or PF₆; D=H₂O, MeOH or DMF) have been prepared and characterized by i.r. and electronic spectra, magnetic susceptibilities at room temperature and by cyclic voltammetry measurements.