Speciation and Stability of Dioxovanadium(V) Complexes with Diethylenetriaminepentaacetic Acid at Different Ionic Strengths

UV spectroscopic measurements have been used to determine the binding ability of diethylenetriaminepentaacetic acid (DTPA) ligand towards the $ {\text{VO}}_2^+ $ ion at different ionic strengths of sodium chloride (0.11–0.95 mol·dm^?3) and at T = 298 K. Dissociation constants of DTPA have been gathered from the literature. Calculations allowed us to identify the formation of three species VO₂H₃L, VO₂H₂L^? and VO₂HL^2? in the pH range of about 1.00–2.50. All of these complexes were characterized in terms of their stability constants on the basis of two different thermodynamic models (extended Debye–Hückel type and specific ion interaction theory) for the investigation of the ionic strength dependence of the stability and dissociation constants. Comparison with literature data is also reported.     

Interaction of Dioxovanadium(V) with Alanine, Alanylalanine, and Alanylglycine

The stability constants of the systems dioxovanadium(V) with alanylalanine, alanylglycine, and alanine have been determined in aqueous solution in 0.8 pH 5 at 25°C and 0.1 mol-dm^–3 (NaClO₄), using a combination of potentiometric and spectrophotometric techniques. The compositions of the formed complexes were determined and it was shown that dioxovanadium(V) forms two mononuclear 1:1 and 1:2 species with alanine of the type VO₂L and VO₂L₂ ^–, and two mononuclear 1:1 complexes with alanylpeptides of the type VO₂HL and VO₂L^–.     

Ionic Strength Effect on the Stability of the V(V) + IDA Complex

In this research the interaction of dioxovanadium(V) with iminodiacetic acid has been considered at 25 °C and pH=1.00–2.50 in an ionic strength range of 0.1 to 1.0 mol⋅dm⁻³ of NaClO₄ by UV spectrophotometric and potentiometric techniques. Only one species, VO₂H₂L⁺, was assumed on the basis of two stoichiometric models. The extended Debye-Hückel theory predicts the first order effects in simple electrolyte solutions. Interactions between the reacting species and the ionic medium are taken into account in the specific ion interaction model. Parabolic, specific ion interaction, and extended Debye-Hückel models have been compared and it has been shown that the parabolic model with two coefficients is satisfactory for this complexation reaction. The results have also been compared with the literature values.     

Thermodynamic Modeling of Actinide Complexation with Acetate and Lactate at High Ionic Strength

The stability constants of NpO ₂ ⁺ , UO ₂ ²⁺ Am³⁺, and Th⁴⁺ with acetate and lactate anions has been measured in 0.3–5.0m NaCl media at 25°C by the solvent extraction technique. For the 1:1 complexation, the values of the stability constants increased in the order: NpO ₂ ⁺ < Am³⁺ < ₂ ²⁺ < Th⁴⁺, in accordance with the actinide charge density and reflecting the strongly ionic bonding of the complexes. The Pitzer ionic interaction parameters were calculated and used to estimate the thermodynamic stability constants at I = 0. Because our data were collected mainly in the high ionic strength region values of ⁽¹⁾ were estimated from values reported in the literature. For all stability constants the Pitzer model gives an excellent representation of the data using three interaction parameters ⁽⁰⁾, ⁽¹⁾, and COn leave from Institute of     

Complexation Constants of Lanthanide Ions with Poly(Methacrylic Acid) and its Copolymers

Complexation of some lanthanide ions with poly(methacrylic acid) and its copolymers was studied by potentiometric titration. Poly [methacrylic acid-co-oligo(ethylene oxide)methacrylate] and poly(methacrylic acid-co-acrylamide) formed tris-carboxylate coordinate lanthanide complexes with large overall complexation constants, while poly-(methacrylic acid)s and copolymer with higher content of the methacrylic acid residue formed bis-coordinate ones. It was concluded that the comonomer residues in the copolymer chains decreased the steric hindrance for the complexation and/or acted as co-coordinating groups of the carboxylic group to lanthanide ions. Very large positive and favorable entropy changes were observed for the complexation with poly(methacrylic acid) and its copolymers. This contribution of thermodynamic parameters to the complexation was contrary to that for the analogous monomeric methacrylic acid complex and is assumed to be induced by dehydration of the polymers through the lanthanide ion complexation.     

Thermodynamic Complexation of Dopamine with Zinc(II) in Media with Different Dielectric Constants

The complexation of zinc(II) with dopamine has been investigated by spectrophotometric measurements in mixed solvent system at an ionic strength of 0.2 mol•dm－3 sodium chloride, employed at at (15±0.1), (25±0.1), (35±0.1) ℃ at inin a pH range of ca. 6 to ca. 7 with a high ratio of ligand to metal. The effect of solvent systems on protonation and complexation are was was discussed. Linear relationships are werewere observed by plotting lg K versus 1/D, where K and D show stability and dielectric constants, respectively.     

Complexation of Molybdenum(VI) with GLDA at Different Ionic Strengths

The interaction of the biodegradable ligand, l-glutamic acid N,N-diacetic acid tetrasodium salt (GLDA) with molybdenum(VI) was studied by determining stability constants at pH 6.00, T?=?298.15 K, and ionic strength 0.0992?<?I/mol·dm^?3?<?2.5689 of sodium chloride. The ionic strength dependence of the stability constants was fitted to both extended Debye–Hückel and specific ion interaction models. Job’s method confirmed the formation of one species, MoO₃GLDA^4?. The values of the stability constants are in agreement with the other data in the literature for the complex formation of aminopolycarboxylic acids with molybdenum(VI). Experimental data were obtained by using UV spectrophotometric method. The formation constant in pure water is 18.96?±?0.08 on the molal concentration scale.     

Complexation of niobium(V) with some bis-(β-diketones)

The complexes of niobium(V) with 2-phenyl-1,1,3,3-tetraacetylpropane and 2-phenyl-1,3-diacetyl-1,3-dibenzoylpropane were investigated by IR, UV,¹H-NMR, and magnetic measurements. Together with analytical data and determination of molecular weights a trimeric structure is proposed for both 1:1 complexes.

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Komplexierung von Niob(V) mit einigen Bis(-diketonen)

Zusammenfassung Es wurden die Komplexe von Niob(V) mit 2-Phenyl-1,1,3,3-tetraacetylpropan und 2-Phenyl-1,3-diacetyl-1,3-dibenzoylpropan untersucht. IR-, UV- und¹H-NMR-Spektren sowie magnetische Messungen zusammen mit analytischen Daten und Molekulargewichtsbestimmungen ergaben für beide 1:1 Komplexe eine trimere Struktur.

     

Study of the Complexation of Protactinium(V) with EDTA

Journal of Solution Chemistry - The complex formation of protactinium(V) with ethylenediaminetetraacetic acid (EDTA) was studied at tracer concentration...     

Complexation of Tungsten(VI) with Methyliminodiacetic Acid at Different Ionic Strengths

The results of this research give ionic strength dependence patterns for the complexation of tungsten(VI) with methyliminodiacetic acid at T?=?298?K. The formation data reported in this work were obtained at different ionic strengths (0.1?<?I/mol·dm^?3?<?1.0) of sodium perchlorate on the basis of Job??s continuous variation method, which show that a 1:1 complex forms at pH?=?7.50. UV experimental data were collected for the calculation of the stability constants according to the extended Debye?CHückel theory, the specific ion interaction theory and the parabolic model. Finally, these three models have been compared.     

Spectrophotometric Determination of Dioxovanadium (V) Ion Using Some Halogen Derivatives of Phenylazo-Chromotropic Acid

A comparative study of the reaction of o-chloro-, m-chloro-, p-chloro-, p-bromo- and p-iodophenylazo-chromotropic acids with dioxovanadium (V) ion have shown that 1:1 and 1:2 violet water soluble complexes were formed at pH 4.5. The p-halogeno-derivatives were found to be very suitable reagents for spectrophotometric determination of VO⁺₂ up to 8 ppm. The application of these dyes as indicators in the spectrophotometric titration of VO⁺₂ with EDTA and the interference of a various cations and anions were reported.     

席夫碱双氧钒(Ⅴ)配合物的合成、结构及其抑制幽门螺旋杆菌脲酶研究

本文合成了2个双氧钒(Ⅴ)配合物,[VO2L1](1)和[VO2L2]2(2)(L1=4-氯-2-[(2-苯胺基乙亚胺基)甲基]苯酚盐;L2=4-[2-(2-{[1-(5-氯-2-羟基苯基)甲亚胺基]胺基}乙胺基)乙亚胺基]-2-戊酮),并通过物理化学方法和单晶X-射线衍射表征了它们的结构。在单核配合物1中,V原子采取畸变的四方锥配位构型,在双核配合物2中,V原子采取八面体配位构型。研究了这2个配合物对幽门螺旋杆菌脲酶的抑制活性。在浓度为100μmol.L-1时,配合物1和2对脲酶的抑制率分别为(52.1±1.8)%和(34.2±3.3)%。还做了配合物和幽门螺旋杆菌脲酶的分子对接研究。配合物的结构和其抑制脲酶活性的关系表明,配合物分子的尺寸和形状对脲酶的抑制作用具有重要影响。     

Determination of Aqueous Nickel-Carbonate and Nickel-Oxalate Complexation Constants

An ion-exchange method was used to determine complexation constants for the Ni-oxalate and Ni-carbonate systems in a NaClO₄ background electrolyte. The Ni-oxalate data were interpreted in terms of a single Niox(aq) complex having log K ₁ values for Ni²⁺ + ox^2– Niox(aq) of 3.9 ± 0.1 (I.S. = 0.5 mol-L^–1 p[H] = 7.1) and 4.4 ± 0.1 (I.S. = 0.1 mol-L^–1 p[H] = 8.6) at 22 ± 1C. Specific ion-interaction theory (SIT) was used to obtain log K ₁ = 5.17 ± 0.05 (95% confidence level and = –0.23 ± 0.15) at I.S. = 0. The Ni-carbonate studies were carried out at p[H] values of 7.5, 8.5, and 9.6 in 0.5 mol-L^–1 NaClO₄/NaHCO₃ solutions. The NiCO₃(aq) species was the dominant complex in the [CO₃ ^2–] concentration ranges studied at all three p[H] values. A log K ₁ value for Ni²⁺ + CO₃ ^2– NiCO₃(aq) of 2.9 ± 0.3 was deduced at I.S. = 0.5 mol-L^–1. Extrapolating this value to zero ionic strength using the SIT approach yielded log K ₁ = 4.2 ± 0.3 (95% confidence level and = –0.26 ± 0.04). The data allowed upper bound values for the complexation constants for NiHCO₃ ⁺ and Ni(CO₃)₂ ^2– to be estimated, i.e., log K < 1.4 for Ni²⁺ + HCO₃ ^– NiHCO₃ ⁺, and log K ₂ < 2 for NiCO₃(aq) + CO₃ ^2– Ni(CO₃)₂ ^2–, respectively.     

Studies on some N-acyl N-phenylhydroxylamines as metal-complexing ligands. V. Formation Constants of Al(III) Chelates

The formation of aluminium complexes of N-acetyl, -chloroacetyl, -benzoyl and -o-, -m- and -p-nitrobenzoyl N-phenylhydroxylamines has been studied potentiometrically in 1:1 aqueous acetone at constant ionic strength (μ = 0.5). Only the first two steps could be followed except in the case of N-acetyl derivative. Values of K₁ and K₂ have been evaluated by projection-strip method and those of K₁, K₂ and K₃ by linear plots. The stabilities of the chelates vary linearly with ligand basicity and a discussion has been made to account for the observed facts.     

Dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases encapsulated in zeolite-Y for the aerobic oxidation of styrene

A series of dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases were encapsulated into the supercages of zeolite-Y and were characterized by X-ray diffraction, SEM, N₂ adsorption/desorption, FT-IR, UV-vis spectroscopy, ICPAES, pair distribution function (PDF) and X-ray absorption near edge structure (XANES) measurements. The encapsulation is achieved by a flexible ligand method in which the transition metal cations were first ion-exchanged into zeolite-Y and then complexed with ligands. The dioxovanadium-exchanged zeolite, dioxovanadium complexes encapsulated in zeolite-Y plus non-encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes showed better activity than their respective nonencapsulated counterparts in most cases. All encapsulated dioxovanadium tetrahydro-Schiff base complexes showed much higher activity in aerobic oxidation of styrene than their corresponding Schiff base complexes.     

Complexation between vanadium(V) and citrate: spectroscopic and structural characterization of a dinuclear vanadium(V) complex

Investigation of the aqueous coordination chemistry for citrate and vanadium(V) resulted in the isolation and characterization of a dinuclear vanadium(V) citrato complex (1) Na₂K₂[VO2(Hcit)]₂ · 9H₂O. Complex (1) is an intermediate between the fully deprotonated and diprotonated citrate vanadate. It may represent an early mobilized precursor in the biosynthesis of FeV-co, as well as a relevant model in the proton transport relay process between P-cluster pair to M-cluster pair. The complex has been characterized by elemental analyses and i.r. spectroscopy. Its i.r. spectra are consistent with a oxo-bridged dinuclear structure as revealed by a single crystal X-ray diffraction study.     

An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelates Valid to High Ionic Strength. I. Ethylenedinitrilotetraacetic Acid (EDTA)

An aqueous thermodynamic model is developed, which accurately describes the effects of Na⁺ complexation, ionic strength, carbonate concentration, and temperature on the complexation of Sr²⁺ by ethylenedinitrilotetraacetic acid (EDTA) under basic conditions. The model is developed from the analysis of literature data on apparent equilibrium constants, enthalpies, and heat capacities, as well as on an extensive set of solubility data on SrCO₃(c) in the presence of EDTA obtained as part of this study. The solubility data for SrCO₃(c) were obtained in solutions ranging in Na₂CO₃ concentration from 0.01 to 1.8 m, in NaNO₃ concentration from 0 to 5 m, and at temperatures extending to 75C. The final aqueous thermodynamic model is based upon the equations of Pitzer and requires the inclusion of a NaEDTA^3– species. An accurate model for the ionic strength dependence of the ion-interaction coefficients for the SrEDTA^2– and NaEDTA^3–aqueous species allows the extrapolation of standard state equilibrium constants for these species, which are significantly different from the 0.1 m reference state values available in the literature. The final model is tested by application to chemical systems containing competing metal ions (i.e., Ca²⁺) to further verify the proposed model and indicate the applicability of the model parameters to chemical systems containing other divalent metal-EDTA complexes.     

An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelators Valid to High Ionic Strength. II. N-(2-Hydroxyethyl)ethylenedinitrilotriacetic Acid (HEDTA)

This is the second paper in a two part series on the development of aqueous thermodynamic models for the complexation of Na⁺ and Sr²⁺ with organic chelators. In this paper, the development of an aqueous thermodynamic model describing the effects of ionic strength, carbonate concentration, and temperature on the complexation of Sr²⁺ by HEDTA under basic conditions is presented. The thermodynamic model describing the Na⁺ interactions with the HEDTA^3–chelate relies solely on the use of Pitzer ion-interaction parameters. The exclusive use of Pitzer ion-interaction parameters differs significantly from our previous model for EDTA, which required the introduction of a NaEDTA^3– ion pair. Estimation of the Pitzer ion-interaction parameters for HEDTA^3– and SrHEDTA^– with Na⁺ allows the extrapolation of a standard-state equilibrium constant for the SrHEDTA^– species, which is one order of magnitude greater than the 0.1 M reference state value available in the literature. The overall model is developed from data available in the literature on apparent equilibrium constants for HEDTA protonation, the solubility of salts in concentrated HEDTA solutions, and from new data on the solubility of SrCO₃(c) obtained as part of this study. The predictions of the final thermodynamic model for the Na-Sr-OH-CO₃-NO₃-HEDTA-H₂O system are tested by application to chemical systems containing competing metal ions (i.e., Ca²⁺).