Formation of variable-composition iron(III) hydrosilicates with the сhrysotile structure

The process of formation of iron hydrosilicates (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was studied. It was shown that the stage of coprecipitation of magnesium and iron hydroxides in the presence of silica nanoparticles forms poorly crystallized layered Mg–Fe double hydroxides having Fe³⁺ ions in the octahedral sites. Hydrothermal treatment of the mixtures of coprecipitated hydroxides and silica nanoparticles gives rise to layered hydrosilicates, where Fe³⁺ ions occupy both the octahedral (preferentially) and tetrahedral sires. The possibility of the formation and a fairly stable existence of the variable-composition layered hydrosilicate (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was shown to correlate with the stability range of its precursor brucite-like Mg–Fe layered double hydroxide.     

High-spin complexes of iron(III) with ethylene glycol and 3(2′-hydroxyphenyl)-5-(4′-substituted phenyl) pyrazolines

Complexes of iron(III) with ethylene glycol and 3(2′-hydroxyphenyl)-5-(4′-substituted phenyl) pyrazolines, [Fe(OCH₂CH₂O)(C₁₅H₁₂N₂OX)] _m ? nH₂O and [Fe(C₁₅H₁₂N₂OX)₂(OCH₂CH₂OH)] (where OCH₂CH₂O and OCH₂CH₂OH = ethylene glycol moiety; C₁₅H₁₂N₂OX = 3(2′-hydroxyphenyl)-5-(4-X-phenyl)pyrazoline; X = H, CH₃, OCH₃, or Cl; m = 2–3 and n = 2–3) have been synthesized and characterized by elemental analysis (C, H, N, Cl, and Fe), molecular weight measurement, magnetic moment data, thermogravimetric analysis, molar conductance, spectral (UV-Vis, IR, and FAB mass), scanning electron microscopy, and X-ray diffraction studies. Bonding of ethylene glycol and pyrazolines in these complexes and the particle size of iron(III) complexes are discussed. Antibacterial and antifungal potential of free pyrazoline and some iron(III) complexes are also discussed.     

Mössbauer spectroscopic study of an iron(III) complex with crown porphyrin

A complex of ⁵⁷Fe with 5-{4-[((4′-hydroxybenzo-15-crown-5)-5′-yl)diazo]phenyl}-10,15,20-triphenylporphyrin was studied by Mössbauer spectroscopy. The presence of signals of two types in the spectra (a doublet and an extended absorption band over a wide velocity range) suggests that the Fe atoms occupy two structurally different positions in this complex. The dependences of the doublet asymmetry on temperature and the angle between the normal to the sample plane and the γ-ray beam were studied. The isomer shift δ of the doublet in the temperature range from 360 to 5 K changes from 0.25 to 0.41 mm/s, while the quadrupole splitting remains virtually unchanged (Δ ≈ 0.65 mm/s). The relaxation-type absorption over a wide velocity range, the relative area of which strongly varies with temperature, can be described by a broad singlet with the following parameters: δ = 0.30–0.44 mm/s and Γ = 2.8–3.38 mm/s. According to the δ values, both signals are due to Fe(III) derivatives.     

Synthesis and properties of iron(II) and iron(III) complexes with 3-(α,γ-dicarboxy-n-propylidene-hydrazino)-5,6-diphenyl-1,2,4-triazine (DCPT)

Summary Proton-ligand formation constants ofDCPT and metal-ligand formation constants of its complexes with Fe(II) and Fe(III) have been determined potentiometrically at 10, 20, 30, and 40°C in 75% (v/v) dioxane-water at 0.10M ionic strength (KNO₃). The thermodynamic parameters G, H, and S have also been evaluated. The possibility of formingM(HL),M(HL)₂, andM(HL)₃ species was substantiated from potentiometric and electronic absorption measurements. The values of the stability constants logK _M(HL), log , and log derived from the spectrophotometric method are in good agreement with those obtained from potentiometric data. The use ofDCPT as an analytical reagent for the spectrophotometric determination of iron is discussed. The solid complexes have been characterized by chemical analysis and magnetic susceptibility, IR, NMR, and electronic spectral data.

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Synthese und Eigenschaften von Eisen(II)- und Eisen(III)-Komplexen mit 3-(,-Dicarboxy-n-propylidene-hydrazino)-5,6-diphenyl-1,2,4-triazin (DCPT)

Zusammenfassung Die Bildungskonstanten sowohl vonDCPT als auch seiner Komplexe mit Fe(II) und Fe(III) wurden bei 10, 20, 30 und 40°C in Dioxan-Wasser (75% (v/v)) bei einer lonenstärke von 0.1M KNO₃ potentiometrisch bestimmt. Zusätzlich wurden die thermodynamischen Parameter G, H und S ermittelt. Die Wahrscheinlichkeit des Auftretens von Komplexen der ArtM(HL),M(HL)₂ undM(HL)₃ wurde mittels potentiometrischer und absorptionsspektroskopischer Messungen erhärtet. Nach beiden Methoden ermittelte Stabilitätkonstanten stimmen gut überein. Die Verwendung vonDCPT als analytisches Reagens zur spektrophotometrischen Eisenbestimmung wird diskutiert. Die Komplexe konnten in Substanz hergestellt werden und wurden durch chemische Analyse und über ihre magnetischen und spektroskopischen Eigenschaften charakterisiert.

     

O,O′-Alkylene dithiophosphate derivatives of iron(II) and iron(III) and their reactions with nitrogen- and phosphorus-donor bases

Summary Solids of the stoichiometric formulae [Fe{S₂P(OPr-n)₂}₃] and [Fe{S₂PO₂G}₃] (G = —CH₂CMe₂CH₂—, CMe_2–CMe₂— or —CH₂CH₂CHMe—) are precipitated from the reactions of FeCl₃ with ammonium dithiophosphates in water. Soluble complexes of the type [Fe{S₂PO₂G}₂], formed by the reactions of FeCl₂ with NH₄[{S₂PO₂G}] in MeOH, can be extracted with benzene. Adducts of the types [Fe{S₂PO₂G}₂L] and [Fe{S₂PO₂G}₂(PPh₃)₂] are formed by the reaction of [Fe{S₂PO₂G}₂] with L (L = 2,2-bipyridyl or 1,10-phenanthroline) and PPh₃, respectively. All the compounds have been characterized by i.r. and u.v.-vis. spectroscopy and magnetic studies.This paper is dedicated to the late Dr. G. Srivastava, Associate Professor, Department of Chemistry, Rajasthan University, Jaipur.     

Synthesis and Characterization of Chromium(III), Molybdenum(III), Ruthenium(III) and Osmium(III) Complexes with N2O2–Schiff Bases of 2-Hydroxy-1-Naphthaldimines

Monomolybdenum, monochromium, triosmium and triruthenium clusters, containing weakly coordinated ligands, are valuable starting materials for the preparation of a wide variety of compounds because of the ease with which these ligands can be displaced by another substrate under mild conditions. Four widely used complexes of this type are Mo(CO)₆, Cr(CO)₆, Os₃(CO)₁₂ and Ru₃(CO)₁₂ respectively. These complexes react with 2-hydroxy-1-naphthaldimines to give octahedral complexes which are characterized by elemental analyses, i.r. and u.v.–vis. spectra, molar conductances, d.t.a. and t.g.a. analyses, cyclic voltammetry, magnetic and e.s.r. measurements. The molar conductances in DMF solution indicate that the complexes are non-ionic. The i.r. spectra of complexes (3), (7) and (10) show (CO) bands due to bonded CO groups, however complexes (6) and (13) show (CO) bands due to bonded, bridged and terminal CO groups. The g ₁₁-values of the complexes indicate that they have covalent bond character. Also, the electrochemical reduction of the complexes has been discussed.     

One-electron oxidized product of difluoroiron(III) porphyrin: is it iron(IV) porphyrin or iron(III) porphyrin π-cation radical?

The electronic structure of [Fe(TMP)F(2)], which is formally a one-electron oxidation equivalent above [Fe(III)(TMP)F(2)](-), has been examined in solution by (1)H NMR, UV-Vis, and M?ssbauer spectroscopy. In CD(2)Cl(2)-CD(3)OD solution at 193 K, the pyrrole-H and m-H signals appeared at 128.2 and 116.7 ppm, respectively. The UV-Vis spectrum showed broad absorption bands at 560-680 nm. The M?ssbauer spectrum taken in frozen toluene-methanol solution exhibited a very broad single line from which the IS and QS values were determined by computer simulation to be 0.50 and 0.14 mm s(-1), respectively. On the basis of these results, it was concluded that the one-electron oxidized product of [Fe(TMP)F(2)](-) should be formulated as the iron(III) radical cation [Fe(III)(TMP˙)F(2)], not as iron(IV) porphyrin [Fe(IV)(TMP)F(2)] as previously suggested.     

Physical properties of a new iron(III) complex, [3-pmH · 3-pm][Fe(NCS)4(3-pm)2]

The iron(III) compound of formula [3-pmH · 3-pm][Fe(NCS)₄(3-pm)₂] (3-pm = 3-(hydroxymethyl)pyridine) has been prepared by reaction between iron(III) thiocyanate and 3-(hydroxymethyl)pyridine in ethanol. The characterization was based on elemental analysis, infrared spectra and magnetic measurements. Single crystal X-ray diffraction methods show the monoclinic P2(1)/c space group with unit cell parameters: a = 12.295(3) Å, b = 15.854(3) Å, c = 16.880(3) Å, β = 100.12(3)° and Z = 4. The asymmetric unit of the title compound consists of [3-pmH · 3-pm]⁺ and [Fe(NCS)₄(3-pm)₂]^? held together by ionic interaction and a hydrogen bond interaction (O(68)–H(68) ··· O(78)). The central metal ion is octahedrally coordinated by six nitrogens, four from NCS^? form the equatorial plane and two from two 3-(hydroxymethyl)pyridines occupy axial positions. Magnetic susceptibility data in the temperature range 1.8–300 K show that iron(III) is high-spin S = 5/2(⁵ T _2g). Structural parameters and IR spectra of similar complexes are compared and discussed.     

Sorption of iron(III)–alginate complexes on cellulose fibres

Multivalent ions take a significant role in the sorption of soluble polysaccharides on solid cellulose substrates and thus demonstrate an important principle in structural polysaccharide organisation. Sorption of Fe(III)–alginate complexes on lyocell fibres as model for the insoluble cellulose matrix has been studied between pH 3–13, at 30 and 60 °C. Sorption maximum of the Fe(III)–alginate complex was observed at pH 3 where the sorbed amounts of alginate and iron were 6,600 and 85 mg iron per kg cellulose respectively. Under the experimental conditions used, a concentration of 0.05 mM Fe(III) is sufficient to achieve surface sorption of Fe(III)–alginate complex. The alginate sorption exhibited minor dependence on molar ratio of Fe(III) to alginate. In environmental scanning electron microscopy no deposition of Fe-hydroxides on the fiber surface was detected. The thickness of the adsorbed Fe(III)–alginate layer on the fiber surface was estimated with 12–22 nm. Tensile strength and abrasion resistance of Fe(III)–alginate treated fibers were not reduced through the sorption treatment. Alginate modified cellulose is of interest as material for medical application, as sorbent and textile finish.     

Synthesis and characterization of a monomeric and a dihydroxo-bridged dimeric complexes of iron(III) with α-benzoinoxime

The reaction of α-benzoinoxime, H₂BNO with FeCl₃ in the presence of Et₃N as a base gives the mononuclear Fe(III) complex, Fe(HBNO)₃ (1). Treatment of 1 with a methanolic solution of KOH at room temperature leads to a dinuclear Fe(III)–Fe(III) complex, [Fe(HBNO)₂OH]₂ (2). The complexes were initially characterized on the basis of their elemental, mass and thermal analyses. The IR studies were useful in assigning the coordination mode of the benzoinoxime ligand to the iron metal. In addition, the presence of a hydroxo-bridge in the dimeric complex 2 is inferred from the IR spectral studies. Room-temperature Mössbauer studies indicated octahedral, high-spin iron(III). Variable-temperature magnetic susceptibility measurements supported the existence of the μ-dihydroxo-bridging structure core, Fe^III(μ-OH)₂Fe^III in the dinuclear complex 2. Theoretical modelling of the magnetic data indicated a weak antiferromagnetic spin exchange between the iron(III) centers (J = −8.35 cm⁻¹, g = 2.01, ρ = 0.02 and TIP = 1.7 × 10⁻⁴ cm³ mol⁻¹ for H = −2JS₁ · S₂). The electronic spectra of the complexes revealed two bands due to d–d transitions and one band assignable to an oxygen (p_π) → Fe(d_π∗) LMCT transition observed in each complex. An additional charge-transfer transition, assignable to μ-hydroxo(p_π) → Fe(d_π∗), was observed for the dimeric complex 2. The structural and vibrational behaviors of these complexes have been elucidated with quantum mechanical methods.     

Crystal structure of a μ-oxo-bridged dimeric iron(III) complex

A dimeric [{Fe(5-ClL1)}₂(μ-O)], [H₂-5-ClL1 = N,N′-bis(5-chloro-2-hydroxybenzylidene)-2-methylpropane-1,2-diamine] tetradentate Schiff-base complex, 1, has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis. Structural analysis of complex 1 shows that the complex is a centrosymmetric dimer. Each of the Fe(III) ions has a five-coordinate geometry and one oxygen atom bridges two Fe(III) ions to form a μ-oxo structure. The geometry around iron atom can be described as a square based pyramid with the FeN₂O₂ coordination plane and oxo ligand.     

Fluorescence immunoassay of α-fetoprotein with iron(III) tetrasulfonatophthalocyanine as a mimetic enzyme labeling reagent

A new fluorimetric immunoassay for α-fetoprotein (AFP) has been developed using a novel promising mimetic peroxidase, iron(III) tetrasulfonatophthalocyanine (FeTSPc), as a labeling reagent to catalyze the fluorescence reaction of P- hydroxyphenylacetic acid (P-HPA) and hydrogen peroxide (H₂O₂). In the competitive immunoassay, anti-AFP antibody was coated on a 96-well plate (polystyrene) and a constant amount of FeTSPc-labeled AFP and a known amount of test solution were added. Non-labeled and FeTSPc-labeled AFP compete for binding to the plate-bound antibody. After the immunoreaction, the immunochemically adsorbed FeTSPc–AFP conjugate moiety was determined by measuring the fluorescence produced in a solution containing P-HPA and H₂O₂. AFP can be determined in the concentration range of 1–300 ng mL^–1 with a detection limit of 0.5 ng mL^–1. Received: 14 November 2000 / Revised: 29 December 2000 / Accepted: 15 January 2001     

A micro-heterometric determination of traces of iron (III) in alloys and salts with α-nitroso β-naphthol

Ferric iron constituting approximately 0.01% — 0.1% may be determined by a heterometric titration with α-nitroso-β-naphthol. The solution may contain 99.9% or more of calcium, barium, magnesium, aluminium, chromium, manganese, nickel, cadmium or lead salts. No previous separation is necessary. The α-nitroso-β-naphthol is dissolved in alcohol. The analysed solution must be acidified. No complexing agents are necessary. Citrate or tartrate must be absent. The maximum optical density values which are obtained at the end of the titration are proportional to the amount of iron which is analysed. These maximum values are entirely unaffected by the concentrated salt solutions. The heterometric sensitivity of the reaction between iron and α-nitroso-β-naphthol is three times higher in 50% alcoholic solution than in water. The titration takes about one hour. The error is 0.0—4%.     

NMR and EPR investigations of iron corrolates: iron(III) corrolate pi cation radicals or iron(IV) corrolates?

The chloroiron corrolates of 2,3,7,8,12,13,17,18-octamethyl- and 7,13-dimethyl-2,3,8,12,17,18-hexaethylcorrole ([(Me8C)FeCl] and [(7,13-Me2Et6C)FeCl], respectively) and their bisimidazole complexes have been investigated by NMR spectroscopy as a function of temperature, and by EPR spectroscopy at 4.2 K. Magnetic susceptibilities were measured by the modified Evans method. It is found that the electron configuration of the chloroiron corrolates is that of a S = 3/2 Fe(III) center coupled to a corrolate pi radical, where one electron has been removed from the pi system of the corrolate. This pi radical is antiferromagnetically coupled to the unpaired electrons of the iron to yield an overall S = 1 complex, as evidenced by the very large positive shifts of the meso-H resonances (183 and 172 ppm). That this antiferromagnetic coupling is very strong is supported by the near-Curie behavior of the 1H chemical shifts. For the chloroiron corrolates in the presence of imidazole, imidazole-d4, and N-methylimidazole at temperatures of -50 degrees C and below, the mono- and bisligand complexes are formed. The NMR spectra can be assigned on the basis of chemical exchange between the chloroiron(III) parent complex and the bisligand complex at -30 degrees C, and between the bisligand complex and the monoligand complex at -50 degrees C. The bisimidazole complexes show pyrrole CH2 and CH3 resonances characteristic of low-spin Fe(III) centers (S = 1/2), but with strongly upfield-shifted meso-H resonances (delta values of -95 and -82.5 ppm for the octamethyl complex and -188 and -161 ppm for the dimethylhexaethyl complex at 203 K) characteristic of the presence of a macrocycle-centered unpaired electron. The magnetic moments of these bisligand complexes are somewhat lower than expected for overall S = 1 systems, and decrease as the temperature is lowered. The lower apparent magnetic moments (2.0-1.8 mu B between -50 and -90 degrees C) are believed to be caused by a combination of weak or no magnetic coupling between the metal and macrocycle electrons and decreasing solubility of the complex as the temperature is lowered. The non-Curie behavior of the 1H chemical shifts observed in the low-temperature (-50 to -90 degrees C) NMR spectra likely arises from a combination of the effects of weak antiferromagnetic coupling of metal and macrocycle spins, a low-lying electronic excited state, and ligand binding/loss equilibria at the highest temperatures studied (-50 degrees C).     

Extraction chromatographic study of aluminium(III) and mutual separation of aluminium(III), gallium(III), indium(III) and thallium(III) with N-n-octylaniline

A selective method has been developed for extraction chromatographic studies of aluminium(III) and its separation from several metal ions with a chromatographic column containing N-n-octylaniline (liquid anion exchanger) coated on silanized silica gel as a stationary phase. The aluminium(III) was quantitatively extracted with the 0.065 mol/L N-n-octylaninine from 0.013 to 0.05 mol/L sodium succinate at a flow rate of 1.0 mL/min. The extracted metal ion has been recovered by eluting with 25.0 mL of 0.05 mol/L hydrochloric acid and estimated spectrophotometrically with aurintricarboxylic acid. The effects of the acid concentration, the reagent concentration, the flow rate and the eluting agents have been investigated. The log-log plots of distribution coefficient (KdAl(III)) versus N-n-octylaniline concentrationin 0.005 and 0.007 mol/L sodium succinate gave theslopes 0.5 and 0.7 respectively and showed theprobable composition of theextracted species was 1:1 (metal to amine ratio) and the nature of extracted species is [RR''NH2+ Al succinate2-] org. .The extraction of aluminium(III) was carried out in the presence of various ions to ascertain the tolerance limit of individual ions. Aluminium(III) has been separated from multicomponent mixtures, pharmaceutical samples and synthetic mixtures corresponding to alloys. A scheme for mutual separation of aluminium(III), indium(III), gallium(III) and thallium(III) has been developed by using suitable masking agents. The method is fast, accurate and precise.     

Mixed-ligand complexes of iron(II), iron(III), copper(II), and cobalt(II) with pyrazolonic and 2,2′-bipyridine ligands

New mixed-ligand complexes, [M₂(BAMP)(bipy)₂][MCl₄]₂, M=Co⁺²(1), Cu⁺²(2), [M₂(TAMEN)(bipy)₂][MCl₄]₂, M=Fe⁺²(3), Co²⁺(4), and [Fe₂(TAMEN)(bipy)₂][FeCl₆]₂ (5), where BAMP and TAMEN stand for the Mannich bases N,N′-bis(antipyryl-4-methylene)-piperazine and N,N′-tetra(antipyryl-4-methylene)-1,2-ethane-diamine, respectively, have been obtained and characterized by elemental analyses, conductometric and magnetic susceptibility measurements at room temperature, mass spectrometry, UV-Vis, infrared, and mass spectroscopy, and ¹H NMR spectra for the ligands.     

Mössbauer and electronic spectral studies of iron(III) complexes of oximes

The hydroxo-bridge complexes of the type [Fe(2)(ligand-H)(4)(OH)(2)] with bidentate nitrogen-oxygen donor ligands, viz. 2-hydroxynaphthaldehydeoxime [hnoH(2)], 2-hydroxyacetphenoneoxime [haoH(2)], salicylaldooxime [SalH(2)], 2-hydroxypropiophenoneoxime [hnoH(2)] have been prepared. All the complexes have been characterized by elemental analysis, magnetic moments, electronic and M?ssbauer spectral studies. M?ssbauer parameters of the complexes clearly suggest high spin configuration of Fe(III) showing lower magnetic moment to that of the spin only value, i.e. 5.92 BM. It may be due to the antiferromagnetic interaction between Fe(III) centers.     

Complexation of Sc(III), Ga(III), In(III) and Ln(III) with Eriochrome Red B

Cyclic linear-sweep voltammetry was used to study the complexation of Sc(III), Ga(III), In(III) and Ln(III) with eriochrome red B (ERB). It was established that all metal ions investigated form complex compounds with azodye having a mole ratio, M(III):ERB = 1:2. The hydroxo forms of M(III) ions, which take part in interaction with ERB, were determined by the Nazarenko method. The stability constants for the formation of these chelates are nearly the same. It was shown that the reduction of the ligand in the complex does not only depend on the peculiarities of complexation, but the processes occurring in pre-electrode layer also influence it.     

Redox reaction of N,N′-phenylenebis-(salicylideneiminato)iron(III) with hypophosphorous acid in mixed aqueous medium

Transition Metal Chemistry - The kinetics of redox reaction between N,N′-phenylenebis-(salicylideneiminato)iron(III), hereafter referred to as [FeSalphen]+, and hypophosphorous acid was...     

Studies on outer-sphere electron transfer reactions of surfactant–cobalt(III) complexes with iron(II) in liposome (dipalmitoylphosphotidylcholine) vesicles

The effect of unilamellar vesicles of dipalmitoylphosphotidylcholine (DPPC), both below and above the phase transfer region, on the second-order rate constants for outer-sphere electron transfer between Fe²⁺ and the surfactant?Ccobalt(III) complexes, cis-[Co(en)₂(C₁₂H₂₅NH₂)₂]³⁺ and cis-[Co(trien)(C₁₂H₂₅NH₂)₂]³⁺ (en?=?ethylenediamine, trien?=?triethylenetetramine, C₁₂H₂₅NH₂?=?dodecylamine) was studied by UV?CVis absorption spectroscopy. Below the phase transition temperature of DPPC, the rate decreased with increasing concentration of DPPC, while above the phase transition temperature the rate increased with increasing concentration of DPPC. It is concluded that below the phase transition temperature, there is an accumulation of surfactant?Ccobalt(III) complexes at the interior of the vesicle membrane through hydrophobic effects, and above the phase transition temperature the surfactant?Ccobalt(III) complex is released from the interior to the exterior surface of the vesicle. Through isokinetic plots, we have established that the mechanism of the reaction does not alter during the phase transition of DPPC.