Stability constants of iron(II) sulfate complexes

The complex formation equilibria between iron(II) and sulfate ions have been studied at 25 degrees C in 3 M NaClO4 ionic medium by measuring with a glass electrode the competition of Fe2+ and H+ ions for the sulfate ion. The concentrations of the metal and of the ligand were varied in the ranges 0.01 to 0.125 and 0.01 to 0.250 M, respectively. The analytical concentration of strong acid was chosen to be 0.01 or 0.03 M. The potentials of the glass electrode, corrected for the effect of replacement of medium ions with reagent species, have been interpreted with the equilibria [formula: see text] Stability constants valid in the infinite dilution reference state, logK zero = 1.98 +/- 0.16, log beta 1 zero = 2.1(5) +/- 0.2 and log beta 2 = 2.5 +/- 0.2, have been estimated by assuming the validity of the specific interaction theory.     

Stability constants of manganese(II) bromide complexes

Manganese-54 has been used as a tracer in an investigation of solutions containing manganese(II) bromide complexes. By a cation-exchange method values have been obtained for the stability constants beta(j) = [MnBr((2-j)+)(j)]/[Mn(2+)][Br(-)](j), valid for 20 degrees and ionic strength 0.691M maintained with perchloric acid.     

Stability constants of palladium(II) complexes with thio- and dithiodiacids

The formation of complexes between palladium(II) and 3,3′-thiodipropanoic (TDPA) and 3,3′-dithiodipropanoic (DTDPA) acids has been studied by using spectrophotometric methods in acidic aqueous media with a constant ionic strength of 0.5 M (Na⁺, H⁺)ClO⁻₄. The stoichiometry of the detected complexes is 1:1 and 1:2 (metal:ligand) for the Pd-TDPA system, and 2:1 and 1:1 for the Pd-DTDPA system. The spectrophotometric characteristics and equilibrium constants for the different species have been calculated with the LETAGROP-SPEFO computer program.     

Stability constants of chloro-complexes of cadmium(II) in sea-water medium

Potentiometry with ion-selective electrodes and anodic stripping voltammetry were used to measure the stability constants for cadmium chloro-complexes at 20 +/- 0.1 degrees in synthetic sea-water and at an ionic strength of 0.700 (NaClO(4) + NaCl). The values of beta(ML) and beta(ML(2)) obtained by the two methods are in good agreement.     

Stability constants of nickel(II)-nicotinamide complexes in aqueous-ethanol solutions

The change in stability of 1: 1 and 1: 2 nicotinamide nickel(II) complexes in an aqueous ethanol with ethanol contents of 0 to 0.85 molar fractions is studied via potentiometry at 298.2 ± 0.1 K and a ionic strength of 0.25 (NaClO₄). The constant of complex formation for the first step increases at concentrations of organic solvent lower than 0.5 molar fractions and decreases at a higher content of ethanol. The weakening of the solvation of the donor center in nicotinamide corresponds to the observed change in the stability of the complex. A linear interrelation between the change in the coordination equilibrium constant and the difference between the effect of solvent composition on the solvation of the complex ions and complexing agent is revealed.     

Stability constants of oxalate complexes of copper (II) and nickel (II) by paper electrophoresis

Summary Stability constants of copper (II) and nickel (II) oxalates have been determined by paper electrophoresis. Oxalic acid (0.005 mol dm⁻³) was added to the background electrolyte: 0.1 mol dm⁻³ HClO₄. The proportions of HC₂O ₄ ⁻ and C₂O ₄ ²⁻ were varied by changing the pH of the electrolyte, these anions yielding the complex ions MHC₂O ₄ ⁺ and M(C₂O₄) ₂ ²⁻ , average values of the stability constants for which are 10^2.4 and 10^7.6 respectively for Cu(II), and 10^2.3 and 10^6.5 for Ni(II) (μ=0.1,30°).     

The Stability of the Copper(II)-Eriochrome Red B Complex and the Compleximetric Titration of Copper(II) Ion

Abstract

Values of the conditional stability constant of the copper(II)-Eriochrome Red B complex in aqueous solutions of pH 3–6 have been determined employing a cupric ion electrode. When the ionic strength of the solution is 0.01, the value of the second acidity constant (pk₂) of Eriochrome Red B is 6.28 and the logarithm of the stability constant of the copper complex, log k_CuHI, about 8.2. The complex can be used as an indicator in the ocapleximetric titration of cupric ion with EDTA at pH values from 4 to 8.     

Double Hydrated Cobalt(II) Copper(II) and Nickel(II) Copper(II) Ammine Diphosphates

Synthesis of amorphous and crystalline double hydrated cobalt copper and nickel copper ammine diphosphates with a coordination structure is described.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 369–372.Original Russian Text Copyright © 2005 by Voitenko, Zhilyak, Kopilevich.     

Copper(II) complexes of blood pressure active drugs

The interaction of copper(II) with medications, used for the regulation of arterial blood pressure, has been studied and discussed. The drugs include antihypotensives and antihypertensives of different types: -blockers, vasodilators, ACE-inhibitors and diuretics. The paper summarizes the results obtained for the characterization of the complexation processes and determination of the structure and properties of the complexes formed.     

Electrophilic Copper(II) → Metal(II) Substitution in Gelatin-Immobilized Copper(II) Hexacyanoferrate(II) Matrix Implants

Contact of thin layers of gelatin-immobilized copper(II) hexacyanoferrate(II) matrices with aqueous solutions of Co(II), Ni(II), Zn(II), and Cd(II) chlorides results in partial substitution of these ions for Cu(II) to give (dd)-heterobinuclear hexacyanoferrates(II) of copper(II) and the corresponding double-charged ion.     

The Acidity of Malondialdehyde and the Stability of its Complexes with Nickel(II) and Copper(II)

The acidity of malondialdehyde as well as the stability of its 1 :1-complexes with Ni^II and Cu^II have been determined (Table). In comparison with the enolates of aliphatic β-dike-tones the anion C₃H₃O₂? has not only a strikingly reduced basicity, but is also a grossly inferior ligand for metal cations.     

Copper(II) complexes of cyclic tetra-azatetra-acetic acids-unusual features and possible analytical applications

An examination of the copper(II) complexes of some cyclic tetra-azatetra-acetic acids has shown that the 1,4,7,10-tetra-azacyclotridecane-N,N',N',N'-tetra-acetic acid complex has an unusually high molar absorptivity and other favourable characteristics which make this ligand a convenient reagent for the fast and easy spectrophotometric determination of moderately small quantities of copper.     

Structure, Stability, and Lability of Copper(II) Complexes with Triglycine

Equilibrium constants of complex formation, rate constants of chemical exchange reactions, and characteristics of electronic absorption spectra for species detected in aqueous solution of copper(II) with triglycine were determined, and conclusions on the structure of the complexes were made. A possibility of H-bond formation between the ammonium group of the zwitter-ionic form of the ligand and the second peptide oxygen in the anionic form of an adjacent ligand was shown. Kinetics and mechanisms of ligand and proton exchanges in solutions of copper(II) bistripeptide complexes with the ligand containing a deprotonated peptide nitrogen atom were studied. A new mechanism was proposed for hydroxide-catalyzed substitution reactions in copper(II) complexes with tripeptides.     

Stability constants and molar absorptivities for complexes of chromium(III) and cobalt(II) with 2-pyridylmethanamine

The stability constants and molar absorptivities of complexes of Cr(3+) and Co(2+) with 2-pyridinemethanamine have been determined from spectrophotometric data of very dilute aqueous solutions.