Extraction,complex formation and spectrophotometric determination of iron(III) with 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone

Summary The extraction of iron(III) from aqueous HCl, H₂SO₄, HClO₄, HNO₃ solutions by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in CHCl₃ has been studied. Quantitative extraction of iron(III) is achieved if the concentration of the acids does not exceed 1N. The composition of the iron (III)—HA complex formed in the organic phase was investigated spectrophotometrically, radiometrically and by analysis of the isolated species. In the aqueous phase iron (III) and HA form three different complexes, depending on the initial iron: HA concentration ratio and the pH of the solution. They are the violet FeA²⁺, the orange-red FeA₂ ⁺ and the orange-yellow FeA₃. The latter is identical with the complex found in the organic phase, which was isolated as a solid crystalline material and characterized by elemental analysis and infrared spectroscopy. A spectrophotometric method for the determination of iron(III) in the aqueous phase and in the chloroform solution, by extraction with HA, is described.

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Zusammenfassung Die Extraktion von Fe(III) aus wäßrigen Lösungen von HCl, H₂SO₄, HClO₄ oder HNO₃ mit 2-Carbäthoxy-5-hydroxy-1-(4-tolyl)-4-pyridon (HA) in chloroformischer Lösung wurde untersucht. Sie verläuft quantitativ, wenn die Konzentration der Säure nicht größer ist als 1-n. Die Zusammensetzung des Fe(III)-HA-Komplexes in der organischen Phase wurde spektrophotometrisch, radiometrisch und durch Analyse der isolierten Substanz untersucht. In wäßrigem Milieu bilden Eisen(III) und HA drei verschiedene Komplexe je nach dem anfänglichen Konzentrationsverhältnis Fe(III): HA und je nach dem pH der Lösung. FeA²⁺ ist violett, FeA₂ ⁺ ist orange-rot und FeA₃ orangegelb. Diese Verbindung ist mit dem in der organischen Phase gefundenen Komplex identisch, der in kristallisierter Form isoliert und durch Elementaranalyse und IR-Spektrometrie charakterisiert wurde. Eine spektrophotometrische Methode zur Eisen(III)-Bestimmung in wäßriger Phase und in chloroformischer Lösung durch Extraktion mit HA wurde beschrieben.

     

Iron Extraction with Di(2-Ethylhexyl)dithiophosphoric Acid and a Binary Extractant Based on It

Iron(III) extraction with trioctylmethylammonium di(2-ethylhexyl)dithiophosphate and di(2- ethylhexyl)dithiophosphoric acid was studied. It was shown that di(2-ethylhexyl)dithiophosphoric acid extracts iron in the form of the complex FeA₂, regardless of the oxidation state of iron in the initial aqueous solution. It was also shown that the iron(III) extraction with trioctylmethylammonium di(2-ethylhexyl)dithiophosphate over a wide acidity range occurs primarily to produce extractable substance (R₄N)FeCl₄; and at pH > 1, iron(II) dialkyldithiophosphate is also extracted into the organic phase. It was established that, in a system with a binary extractant, iron can be efficiently stripped from the organic phase with water or diluted solutions of mineral acids.     

Synthesis and properties of a monomeric and a μ-oxo-bridged dimeric iron(III) complex with a tetradentate pyridine amide in-plane ligand. X-ray structure of [Fe(bpc)Cl(DMF)] [H2bpc=4,5-dichloro-1,2-bis(pyridine-2-carboxamido)benzene]

The controlled nucleophilic halide displacement reaction of [NEt₄][Fe(bpc)Cl₂] [H₂bpc=4,5-dichloro-1,2-bis(pyridine-2-carboxamido) benzene] with AgClO₄ in MeCN afforded a crystalline iron(III) complex Fe(bpc)Cl·H₂O 1. The mixed chloro-dimethylformamide (DMF) axially ligated complex [Fe(bpc)Cl(DMF)] (obtained during recrystallization of 1 from DMF; however, it loses DMF quite readily to revert back to 1) has been structurally characterized. It belongs to only a handful of mononuclear high-spin iron(III) complexes having deprotonated picolinamide ligand. The iron(III) centre is co-ordinated in the equatorial plane by two pyridine nitrogens and two deprotonated amide nitrogens of the ligand, and two axial sites are co-ordinated by a chloride ion and a DMF molecule. The metal atom has a distorted octahedral geometry. Reaction of 1 with [ⁿBu₄N][OH] in MeOH afforded a μ-oxo-bridged diiron(III) complex, [Fe(bpc)]₂O·DMF·2H₂O, 2. The spin state and the co-ordination environment of the iron(III) centres in 1 and 2 have been determined by temperature-dependent (25–300 K) magnetic susceptibility measurements in the solid state (Faraday method) and Mössbauer spectral studies at 300 K. Complex 1 behaves as a perfect S=5/2 system, in the solid-state as well as in DMF solution. The two iron(III) centres in 2 are antiferromagnetically coupled (J=−117.8 cm⁻¹) and the bridged dimeric structure is retained in DMF solution. Bridge-cleavage reactions of 2 have been demonstrated by its ready reaction with mineral acids such as HCl and MeCO₂H to generate authentic S=5/2 complexes, [Fe(bpc)Cl₂]⁻ and [Fe(bpc)(O₂CMe)₂]⁻, respectively.     

Electrochemical Behavior of Iron(III)/Iron(II) Couple in Dimethylformamide

The electrochemical behavior of the iron(III)/iron(II) couple was investigated in both complexing (Cl⁻) and noncomplexing (ClO⁻₄) media in dimethylformamide (DMF), and the results were compared with the results obtained in aqueous solutions. The diffusion coefficients for iron(III) and iron(II) in DMF are larger in complexing medium than in noncomplexing medium, contrary to the results obtained in aqueous solutions. The heterogeneous electron transfer rate constants for the iron(III)/iron(II) couple obtained in DMF were found to be smaller in DMF solution as a result of the specific adsorption of DMF. The formal potential of the Fe(III)/Fe(II) couple in DMF is about 0.2 V less positive in noncomplexing medium as a result of the greater stabilization of iron(III) by the strongly cation-solvating DMF. The formal potential of the same couple in complexing medium (Cl⁻) was found to be 0.5 V less positive due to a combination of solvation and complexation effects. Cyclic voltammetric investigations show a quasi-reversible electron transfer without any coupled chemical reaction.     

Preparation, Crystal Structure and Enthalpy Change of Formation of the Reaction in Liquid Phase of a New Three- Dimensional Mixed-Ligand Holmium（Ⅲ）Coordination Polymer Based on Strong π-π Stacking Interactions

A new three-dimensional coordination polymer, [Ho（5-nip）（phen）（NO3）（DMF）] （5-nip=5-nitroisophthalic acid and phen=1,10-phenanthroline）, was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the title complex crystallizes in space group P2/m with a= 1.0906（3） nm, b =1.2804 （3） nm, c= 1.6987（4） nm, β=91.400（5）°, Z=4, Dc= 1.931 Mg/m^3, F（000）= 1352. Each Ho（Ⅲ） ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO3 anion, one DMF molecule and one 1,10-phenanthroline molecule. The complex is constructed with one-dimensional ribbons featuring dinuclear units and the one-dimensional ribbons are further assembled into two-dimensional networks by strong π-π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three-dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 ℃. Its enthalpy change of formation of the reaction in liquid-phase in solvent DMF was measured using an RD496-Ⅲ type microcalorimeter with a value of （-11.016±0.184） kJ·mol^-1.     

Thin-layer chromatography of tris(1,10-phenanthroline)iron(II) and tris(2,2′-bipyridine)iron(II) on Sephadex G gels

Summary Gel chromatographic behaviour of tris(1, 10-phenanthroline)iron(II), tris(2,2′-bipyridine)iron(II) and tris(glycinato)cobalt(III) on Sephadex G-10 or G-25 was investigated by TLC with 0.001–1.0M NaCl as the eluent. The zone shapes and R_M values of tris(1,10-phenanthroline)iron(II) and tris(2,2′-bipyridine)iron(II) were appreciably dependent on the sample and eluent concentration, while the neutral complex, tris(glycinato) cobalt(III), exhibited the round zones with constant R_M values. The order of R_M values was found to be tris(glycinato)cobalt(III<tris(2,2∔pyridine)iron(II)<tris-(1,10-phenanthroline)iron(II) in all systems studied, although the reverse trend was expected when assuming the chromatographic behaviour of solute compounds to be controlled by the “sieving effect”. The comparison of the behaviour on Sephadex G gels with that on CM-cellulose revealed that the predominant mechanism involved is not the sieving effect, but ion-exchange and/or hydrophobic interaction.     

Hydroxamic acid polymers. II. Design of a polymeric chelating agent for iron

The iron chelating ability of hydroxamic acid polymers was studied as a function of the atomic chain spacing separating neighboring hydroxamic acid units. Two polymers were prepared, one having the hydroxamic acid group separated by 11 atoms and the other by three atoms. The iron binding of these polymers was compared with the model compound desferrioxamine B (DFO) and with a previously prepared polymer having a nine-atom spacing. Mole ratio plots indicated the following order of stability: DFO ≈ 11 atom > 9 atom > 3 atom. These results are in accordance with the picture derived from molecular models which shows that with a spacing of 11 atoms, three neighboring hydroxamic acids can fit the octahedral arrangement of the iron (III) complex without appreciable strain. Some strain is introduced when the spacing becomes only nine atoms, and with three atoms, complex formation between three neighboring groups becomes virtually impossible.     

Oxidation of a three-dimensional polymeric iron(II) complex with sodium nitrite in acidic medium

Oxidation of the water-insoluble polymeric iron(II) complex, [(Me₃Sn)₄Fe^II(CN)₆] _n , with NaNO₂ in an acidic medium was followed by monitoring the increase of absorbance of the water-soluble polymeric iron(III) complex product at 419 nm. The reaction is first order in polymer, oxidant and ethanoic acid. Experiments over the temperature range 25–40 °C allowed calculation of the activation parameters. The reaction between the solid polymeric iron(II) complex and NO₂ has been investigated by i.r., electronic-reflectance, X-ray powder diffraction spectra and magnetic measurements. A mechanism involving electron-transfer is proposed.     

Preparation,Structure, and Optical Properties of the 1D Chain Red Luminescent Europium Coordination Polymer: {[Eu2L6(DMF)­(H2O)]·2DMF·H2O}n (L = C9H6ClO2–)

The 1D chain red luminescent europium coordination polymer: {[Eu₂L₆(DMF)(H₂O)] · 2DMF · H₂O}_n ( I ) (L = 4‐chloro‐cinnamic acid anion, C₉H₆ClO₂^–, DMF = N, N‐dimethylformamide) was synthesized by the reaction of Eu(OH)₃ and 4‐chloro‐cinnamic acid ligand. The structure of the coordination polymer was determined by single‐crystal X‐ray diffraction analysis. It reveals that there exists two crystallographically nonequivalent europium atoms in each unit of this coordination polymer and Eu³⁺ ions are connected by two alternating bridging modes to form an endless polymer structure. The luminescent properties and energy transfer process in the complex are investigated at room temperature.     

Spectrophotometric determination of germanium in rocks after selective adsorption on sephadex gel

Germanium(IV) is preconcentrated on Sephadex G-25 from a carbonate solution (pH 12), and desorbed into 0.1 mol dm^?3 nitric acid. Iron(III) and tin(IV) in eluate were removed by a small cation-exchange column. The combination of the two columns made it possible to determine germanium in rocks at mg kg^?1 levels by spectrophotometry with phenylfluorone.     

Interaction of Polystyryl Radical with Tris Azido-Iron(III) Complex

The polymerization of styrene initiated by 2,2′-azobisisobutyro-nitrile (AIBN) had been studied in N, N-dimethylformamide (DMF) at 60°C in presence of tris azido-iron(III) complex. The complex was prepared in situ by mixing solid sodium azide with hexakis(N, N-dimethylformamide)iron(m) perchlorate, [Fe(DMF)₆] (ClO₄)₃, in the ratio 3:1. The nature of the complex formed was established by Job's method. The equilibrium constant for Fe³⁺ + 3N₃ ^? ? Fe(N₃)₃ determined by the limiting logarithmic method is 6.14 ± 10⁶ liter³/mole³. The velocity constant for the polystyryl radical towards the complex is 3.13 ± 10⁴ liter/mole-sec.     

Effects of iron(III) chloro complexes on the polymerization of styrene

The polymerization of styrene initiated by 2,2′-azobisisobutyronitrile has been studied in N,N-dimethylformamide solution at 60°C in the presence of hexakis(N,N-dimethylformamide) iron(III) tetrafluoroborate alone, and also in the presence of added lithium chloride. The presence of Fe(DMF)₆³⁺ ions in the polymerizing systems caused retardation, but iron(III) chloro complexes produced well defined inhibition periods. Velocity constants at 60°C for polystyryl radicals towards Fe(DMF)₆³⁺, Fe(DMF)₅Cl²⁺, Fe(DMF)₄Cl₂⁺, and FeCl₄^? ions were calculated to be 847, 4.15 × 10⁴, 6.55 × 10⁴, and 3.14 × 10⁴ l./mole-sec, respectively. Values of the initiator efficiency f for most systems investigated ranged from 0.59 to 0.62.     

Spectrophotometric Determination of Iron (III) Using 3-Hydroxy-2-Methyl-1,4-Naphthoquinone Monoxime (HMNQM)

Iron (III) forms brown coloured complex with 3-hydroxy-2-methyl-1,4-naphthoquinone monoxime. The iron (III)-HMNQM complex is found to be soluble in DMF and exhibits maximum absorption at 470 nm in the pH range 4.5–5.5. Beer's law is obeyed upto 5.58 ppm of iron (III) and sensitivity of the reaction is 0.0046 μg/cm², with molar absorptivity of 1.21×10⁴ ? mole^?1 cm^?1. The method has been used for the determination of iron (III) in alloys.     

Spectrophotometric Determination of Nitrofurazone

Abstract

A new sensitive and seleactive method for rapid and accurated determination of nitrofarazone is described. The nitrofurazone is reacted with hydroxyl-amine hydrochloride in alkaline medium to give hydroxamic acid which forms the purple violet coloured complex with iron (III), FeCl₃, in acidic medium. The nitrofurazone was determined in presence of commonly used drugs and additives. The results obtained by the proposed and B.P. methods were compared.     

Solvent effect in the preparation of iron(III) azomethine complexes based on 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-N′-ethyl-N-ethylenediamine

Mono- and bis-chelate iron(III)-containing complexes with a tridentate azomethine ligand based on n-dodecyloxybenzoic acid ester derivatives with oxybenzoyl-4-salidene-N??-ethyl-N-ethylenediamine with NO ₃ ^? counterions are obtained. The structure of the compounds is determined by IR spectroscopy, elemental analysis, and mass spectrometry (MALDI-ToF MS). It is found that the complexation of iron salts with tridentate ligands in a mixture of solvents (alcohol:benzene) results in the formation of bischelate compounds of the composition 1:2 with octahedral packing of iron in the complex, while in pure alcohol solutions, asymmetric mono-chelate complexes are obtained.     

Synthesis of dihydroxamic acid chelating polymers and the adsorptive property for uranium in sea water

Preparation of new chelating polymers bearing dihydroxamic acid groups and the adsorptive ability for uranium in sea water are described. Chloromethylated polystyrene crosslinked with divinylbenzene was treated with diethyl malonate in N, N-dimethylformamide to give the polymer having diethyl malonate groups. This polymer was then treated with hydroxylamine in methanol to afford the dihydroxamic acid polymer. The presence of hydroxamic acid groups was confirmed by the appearance of IR absorption band at 1680 cm^?1. The dihydroxamic acid polymer contained carboxylic acid groups as well as hydroxamic acid ones, and the contents of carboxylic acid and hydroxamic acid groups were estimated from elemental analysis to be 2–3 and 2–4 mmol/g, respectively. The polymer showed the adsorptive ability of 40 μg-U/g in 8 days for uranium in sea water. In addition, the polymer showed the selective adsorptivity for iron, nickel, copper, and zinc as well as uranium. The macroreticular-type polymer showed much higher adsorption rate for uranium in sea water than the gel-type ones did, suggesting that the rate depends on the diffusion of the uranium in the polymer support.     

Hydroxamic Acids and Their Metal Complexes Obtained in situ as Electrode-Active Components in the Membranes of Ion-Selective Electrodes

Metal complexes with a hydroxamic acid, namely, N-phenyl-N-(3-styrylacryloyl)hydroxylamine (PSAHA), are promising reagents for use in the preparation of cation- and anion-selective electrodes. The in situ formation of metal complexes by membrane conditioning in a solution of an appropriate metal salt made it possible to prepare cation-selective electrodes for methyl ester of phenylalanine (UO²⁺ ₂) and anion-selective electrodes for tryptophan, phenylalanine (Sn(IV)), and aspartic acid (Cu(II)). The PSAHA-based membrane is sensitive to nitrate ions in solutions of uranyl nitrate (the metal complex is formed in the membrane even without special conditioning).     

2-Bis(carboxymethyl)-amino-5-hydroxy-terephthalsäure als ambifunktioneller Ligand in Eisen(III)-Komplexen

2-Bis(carboxymethyl)-amino-5-hydroxy-terephthalic Acid as an Ambifunctional Ligand in Iron(III) Complexes From steric reasons the anthranilic acid -N,N-diacetic acid group and the salicylic acid group of 2-bis(carboxymethyl)-amino-5-hydroxy-terephthalic acid (H₅C) cannot coordinate to the same central atom. With iron(III) H₅C forms the mononuclear complex (HC)Fe(OH)^2?, the central atom is fixed to the anthranilic acid N,N-diacetic acid group. In a weak acid medium (HC)Fe(OH)^2? is converted into the binuclear species (HC)Fe(C)Fe(OH)^4? which is of a deep red colour. In this complex the anion C^5?has the function of a bridging ligand coordinating both by the anthranilic acid-N,N-diacetic acid group and by the salicylic acid group. The complex formation in the ternary system iron(III)/nitrilo triacetic acid/5-sulfo salicylic acid may be used as model for the dimerisation of the anion (HC)Fe(OH)^2?.     

Mössbauer spectroscopic evidence for iron(III) complexation and reduction in acidic aqueous solutions of indole-3-butyric acid

Mössbauer spectroscopic studies were carried out in acidic (pH 2.3) ⁵⁷Fe^III nitrate containing aqueous solutions of indole-3-butyric acid (IBA), rapidly frozen in liquid nitrogen at various periods of time after mixing the reagents. The data obtained show that in solution in the presence of IBA, iron(III) forms a complex with a dimeric structure characterised by a quadrupole doublet, whereas without IBA under similar conditions iron(III) exhibits a broad spectral feature due to a slow paramagnetic spin relaxation which, at liquid nitrogen temperature, results in a large anomalous line broadening (or, at T = 4.2 K, in a hyperfine magnetic splitting). The spectra of ⁵⁷Fe^III+IBA solutions, kept at ambient temperature under aerobic conditions for increasing periods of time before freezing, contained a gradually increasing contribution of a component with a higher quadrupole splitting. The Mössbauer parameters for that component are typical for iron(II) aquo complexes, thus showing that under these conditions gradual reduction of iron(III) occurs, so that the majority (85%) of dissolved iron(III) is reduced within 2 days. The Mössbauer parameters for the iron(III)-IBA complex in aqueous solution and in the solid state (separated from the solution by filtration) were found to be similar, which may indicate that the dissolved and solid complexes have the same composition and/or iron(III) coordination environment. For the solid complex, the data of elemental analysis suggest the following composition of the dimer: [L₂Fe-(OH)₂-FeL₂] (where L is indole-3-butyrate). This structure is also in agreement with the data of infrared spectroscopic study of the complex reported earlier, with the side-chain carboxylic group in indole-3-butyrate as a bidentate ligand. The Mössbauer parameters for the solid ⁵⁷Fe^III-IBA complex at T = 80 K and its acetone solution rapidly frozen in liquid nitrogen were virtually identical, which indicates that the complex retains its structure upon dissolution in acetone.     

Iron(III) bis-complexes of Schiff bases of S-methyldithiocarbazates: Synthesis,structure, spectral and redox properties and cytotoxicity

A series of iron(III) bis-complexes of the type [FeL₂]X 1-4 , X = OH⁻ ( 1 ), Cl^¯ ( 3 ), and FeCl₄^¯ ( 2 , 4 ), where LH is a tridentate (N,N,S) ligands such as N′-(1-pyridin-2-ylethylidene)-hydrazinecarbodithioic acid methyl ester ( HL1 ), N′-(phenylpyridin-2-ylmethylene)-hydrazinecarbodithioic acid methyl ester ( HL2 ), N′-quinolin-2-ylmethylene-hydrazinecarbodithioic acid methyl ester ( HL3 ), or N′-(1-methyl-1H-imidazol-2-yl-methylene)hydrazinecarbodithioic acid methyl ester ( HL4 ) has been isolated in moderate to good yields and completely characterized by elemental analyses, conductivity studies, and infrared and UV-visible spectral measurements. The single crystal X-ray structures of 1 , 2 and 4 revealed that two deprotonated tridentate (NNS) ligands are meridionally coordinated to constitute a distorted octahedral coordination geometry around iron(III). In acetonitrile solution, all the complexes show quasi-reversible Fe(III)/Fe(II) redox behavior. The in vitro cytotoxicity of the ligands HL1–HL4 (IC₅₀: HL1 , 64.5; HL2 , 51.0; HL3 , 124.0; HL4 , 45.0 μM at 24 h) and complexes 1–4 (IC₅₀: 1 , 84.5; 2 , 40.0; 3 , 168.5; 4 , 50.5 μM at 24 h) towards A549 lung cancer cell lines are similar to cisplatin (69.0 μM), revealing that free ligands cause cancer cell death with potency higher than the corresponding iron(III) complexes. Also, both the ligands and the complexes cause cell death mainly through apoptotic mode, as revealed by the observation of a higher percentage of apoptotic cells in acridine orange (AO)/ ethidium bromide (EB), and Annexin V-Cy3 stained cancer cells.