The thermodynamic characteristics of complex formation of Cd<Superscript>2+</Superscript> with N,N-Bis(carboxymethyl)aspartic acid in aqueous solutions at 298.15 K

The equilibrium constants and heats of formation of complexes of N,N-bis(carboxymethyl)aspartic acid (H₄Y) with Cd²⁺ ions at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO₃) were determined by potentiometric titration and calorimetrically. The thermodynamic characteristics of formation of the CdY²⁻ complex at fixed and zero ionic strength values were calculated. The values obtained were interpreted.     

Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.     

Thermodynamic characteristics of formation reactions of Zn<Superscript>2+</Superscript> and Ni<Superscript>2+</Superscript> complexes with succinic acid in aqueous solutions

The heat effects of complex formation between zinc(II) and nickel(II) ions and succinic acid were determined calorimetrically at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solution were calculated.     

Solution <Superscript>1</Superscript>H n.m.r. of paramagnetic Co<Superscript>2+</Superscript>complexes with dioxobis(carboxymethyl)tetraazamacrocycles

Paramagnetic shifts in the ¹H n.m.r. spectra were observed for high-spin Co²⁺ complexes with 12--14-membered tetraazamacrocycles incorporating two amide groups and two pendant carboxymethyl groups. The pseudocontact term due to the dipolar interaction between the metal ion and the resonant protons was calculated on the basis of X-ray structures, and the Fermi contact term due to spin delocalization was determined. The ethylenediamine moiety of the ligand molecule is coordinated in an unsymmetric manner, even in solution, and internal motion (involving conformational change of the macrocyclic frame and exchange of coordinate bonds) is much slower than the n.m.r. observation frequency. In the 12-membered macrocyclic complex Co(L12), three of the eight CH₂ groups fix their orientation in the n.m.r. time scale; in Co(L13) only one CH₂ group fixes its orientation; in Co(L14) all CH₂ groups undergo a rapid reorientation. The facility in internal motion increases with the ring size, and shows a correlation with the chemical stabilities of these Co²⁺ complexes against oxidation; to atmospheric oxygen, Co²⁺(L12) is the most resistant and Co²⁺(L14) is the most susceptible.     

Extraction of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, and Co<Superscript>2+</Superscript> ions from aqueous solutions with calcium and magnesium phosphates

The efficiency of calcium and magnesium phosphates of different compositions in the extraction of Cu²⁺, Zn², and Co²⁺ ions from aqueous solutions was studied.     

Specific features of absorption of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript> cations from aqueous solutions by calcium phosphates

Kinetic characteristics of the interaction of trisubstituted calcium phosphate Ca₃(PO₄)₂ · xH₂O with Cu²⁺, Zn²⁺, Co²⁺, and Pb²⁺ ions in aqueous solutions were studied.     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Composition and stability of lead(II) compounds with N-(carboxymethyl)aspartic and N,N-bis(carboxymethyl)aspartic acids in aqueous solutions

The reactions of N-(carboxymethyl)aspartic (H₃Y) and N,N-bis(carboxymethyl)aspartic (H₄X) acids with Pb²⁺ ions were studied by potentiometric titration at 298.15 K and I = 0.2, 0.5, and 1.0 (KNO₃). The formation of complex species PbY^?, PbHX^?, and PbX^2? was found and their stability constants were calculated.     

Complexation studies of Co<Superscript>2+</Superscript>ion with orthosilicic acid

Summary The complexation behavior of Co²⁺with ortho-silicic acid (o-SA) has been studied as a function of ionic strength (I) from 0.20 to 1.00M (NaClO₄) at pH 4.96±0.03 and 25 °C by solvent extraction with bis(2-ethylhexyl) phosphoric acid (HDEHP) as the extractant. The stoichiometry of the extracted species was determined to be Co(DEHP)₂(HDEHP)₂. Co²⁺forms a 1:1 complex, CoOSi(OH)₃⁺, as the predominant species witho-SA concentrations of 3.00^. 10^-4to 4.00^. 10^-3M. The stability constant (logb₁) values for CoOSi(OH)₃⁺complex decrease with the increase in ionic strength. These values were fitted with the extended Debye-Huckel expression to obtain the value of logb₁at I=0.00M. The effect of aging time of the o-SA solution on logb₁values for CoOSi(OH)₃⁺complex was investigated and compared with those of the UO₂OSi(OH)₃⁺complex.     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

The thermodynamic characteristics of the formation of Al<Superscript>3+</Superscript> ion complexes with iminodisuccinic acid in aqueous solutions

Complex formation between Al³⁺ and iminodisuccinic acid (H₄L) was studied at 25°C against the background of 0.1, 0.4, 0.6, and 0.8 N solutions of KNO₃ by potentiometry and mathematical modeling. The extrapolation of concentration constants to zero ionic strength was used to calculate the thermodynamic constants of the formation of the AlL⁻, AlHL, and AlOHL²⁻ complexes using an equation with one individual parameter (logβ⁰ = 16.48 ± 0.08, 8.93 ± 0.14, and 22.88 ± 0.08, respectively).     

Thermochemistry of complex formation of Ni<Superscript>2+</Superscript> with glycyl-L-asparagine in aqueous solutions

The heats of formation of complexes in the glycyl-L-asparagine—Ni²⁺ system were determined by calorimetry in an aqueous solution at ionic strengths of 0.5, 1.0, and 1.5 (KNO₃) and a temperature of 298.15 K. The thermodynamic characteristics of the formation of nickel complexes with dipeptide were determined. The influence of the ligand structure on the complexation thermodynamics in solutions was discussed.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 143–148.Original Russian Text Copyright © 2005 by Zelenin, Kochergina.     

Standard thermodynamic functions and constants of complex formation of Nd<Superscript>3+</Superscript> and La<Superscript>3+</Superscript> with L-asparagine in aqueous solutions at 298 K

The enthalpies of complex formation of L-asparagine (HAsn^±) with Nd³⁺ and La³⁺ ions are determined calorimetrically at 298.15 K and an ionic strength of 0.5 (KNO₃). The thermodynamic characteristics of the formation of the NdAsn²⁺, NdAsn²⁺, LaAsn₂⁺, and LaAsn₂⁺ complexes are calculated.     

Synthesis,characterization and DNA binding studies of ruthenium(II) complexes: [Ru(bpy)<Subscript>2</Subscript>(dtmi)]<Superscript>2+</Superscript> and [Ru(bpy)<Subscript>2</Subscript>(dtni)]<Superscript>2+</Superscript>

Two new ruthenium(II) polypyridyl complexes (1) (dtmi = 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-methoxylisatin) and (2) (dtni = 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-nitroisatin) have been synthesized and characterized by elemental analysis, FAB-MS, ES-MS and ¹H-n.m.r. The DNA-binding patterns of complexes were investigated by spectroscopic titration, viscosity measurements and thermal denaturation. The results indicate that the complexes (1) and (2) interact with calf thymus DNA (CT-DNA) by intercalative mode. Due to the withdrawing electronic substitutent in the intercalative ligand, ptni, the DNA-binding affinity of the complexes (2) is larger than that complex (1) does.     

Structural parameters of Cu<Superscript>2+</Superscript> aqua complexes in aqueous solutions of its salts

Published data of various research techniques and own experimental results obtained by the X-ray structural analysis concerning structural characteristics of copper(II) aqua complexes in aqueous solutions of its salts under standard conditions have been generalized. Structural parameters of the nearest environment of this ion, such as coordination number, interparticle distances, and ionic association types, were considered. The possibility of the Jahn-Teller effect realization in aqueous solutions of Cu²⁺ salts was examined.     

Thermal behavior of Cd<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd²⁺ and Co²⁺ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion. The kinetic analysis of the TG non-isothermal data was performed by the isoconversional methods suggested by Friedman and Flynn, Wall and Ozawa, as well as by the non-parametric (Sempere-Nomen) method. All processes put in evidence in TG curves exhibit strong changes of the activation energy values with the conversion degree, which mean that these processes are complex ones. Assuming that each of these processes consists in two steps, the application of non-parametric method leads to average values of the activation energy close to the average values of this parameter obtained by isoconversional methods.     

Synthesis,DNA-binding and photocleavage studies of cobalt(III) complexes [Co(bpy)<Subscript>2</Subscript>(dpta)]<Superscript>3+</Superscript> and [Co(bpy)<Subscript>2</Subscript>(amtp)]<Superscript>3+</Superscript>

Two novel cobalt(III) mixed-polypyridyl complexes [Co(bpy)₂(dpta)]³⁺ and [Co(bpy)₂(amtp)]³⁺ (bpy = 2,2′-bipyridine, dpta = dipyrido-[3,2-a;2′,3′-c]-thien-[3,4-c]azine, amtp = 3-amino-1,2,4-triazino[5,6-f]-1,10-phenanthroline) have been synthesized and characterized. The interaction of Co^III complexes with calf thymus DNA was investigated by spectroscopic and viscosity measurements. Results suggest that the two complexes bind to DNA via an intercalative mode. Moreover, Co^III complexes have been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. The mechanism studies reveal that hydroxyl radical (OH^•) is likely to be the reactive species responsible for the cleavage of plasmid DNA by [Co(bpy)₂(dpta)]³⁺ and superoxide anion radical (O ₂ ^•− ) acts as the key role in the cleavage reaction of plasmid DNA by [Co(bpy)₂(amtp)]³⁺.     

Structure of palladium(II) complexes with nitrilotrimethylenephosphonic acid in aqueous solutions according to <Superscript>31</Superscript>P and <Superscript>1</Superscript>H NMR data

The complex formation in the K₂PdCl₄-nitrilotrimethylenephosphonic acid (NTMP) system with a metal to ligand molar ratio of 1: 1 and 1: 2 was studied by ³¹P and ¹H NMR spectroscopy. The formation of equimolar complexes with NTMP coordinated in the bidentate ([N,O]) and tridentate ([N,O,O]) fashions depending on the reactant and chloride ion concentrations and solution pH was observed.     

Extraction of Cu<Superscript>2+</Superscript> from aqueous solutions using microcapsules containing ionic liquid [BMIM]PF<Subscript>6</Subscript>

Polysulfone (PSF) microcapsules filled with ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] were successfully prepared via solvent evaporation method. The encapsulation capacity of 38.0% was achieved. Microcapsules showed a spherical, porous honeycomb structure. The size of microcapsules was approximately 110 μm and the thickness was approximately 10 μm. Microcapsules have excellent thermal stability, with a higher thermal degradation onset temperature of 360°C compared to traditional extractant-loaded microcapsules. Microcapsules were used to extract Cu²⁺ from aqueous solutions. The effect of chelator, pH, PSF, and ionic liquid on the extraction rate were studied. When chelator was added in aqueous solutions, and the pH of aqueous solutions was 4.5, the extraction rate of microcapsules reached the maximum value, which was 99.0%. These PSF microcapsules containing [BMIM][PF₆] showed potential ability in the treatment of wastewater.     

The thermodynamic characteristics of formation of Zn<Superscript>2+</Superscript> complexes with D,L-tryptophan in aqueous solution

The heat effects of formation of D,L-tryptophan complexes with doubly charged zinc ions were determined calorimetrically. The heat effects of interaction of amino acid solutions with a solution of Zn(II) were measured at 288.15, 298.15, and 308.15 K and ionic strengths of 0.25, 0.50, and 0.75 against the background of KNO₃. The heats of dilution of solutions of zinc nitrate with solutions of the background electrolyte were determined under the same conditions. The corresponding corrections were introduced. The thermochemical data were processed taking into account step equilibria. Along with complex formation, “side” protolytic processes were included. The standard thermodynamic characteristics of complex formation were calculated. The influence of temperature on the heat effects of complex formation in the β-alanine-zinc(II) ions system was considered.