Potentiometric studies in mixed solvents, II Complexes of Nickel(II), Copper(II) and zinc(II) with pyridine, ethylenediamine and glycine

Faraglia, G.; Rossotti, F. J. C.; Rossotti, Hazel

doi:10.1016/s0020-1693(00)93334-6

Cited by 30 publications

(10 citation statements)

References 15 publications

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“…A recent communication (23) has stressed the importance of taking into account the elimination of coordinated water molecules as a cause contributing to the medium effect. Thus a reaction of complex formation may be described by the equation…”

Section: Displacement Of Solvent Moleculesmentioning

confidence: 99%

“…It is commonly held that water molecules are preferentially, if not almost exclusively, solvated in mixed solvents (23,25), although there is certainly evidence (26) that methanol molecules are capable of appreciable solvation froill aqueous methanol solutions. If the co-solvent is essentially inactive with respect to solvation in reaction 11, d -0.…”

Section: Displacement Of Solvent Moleculesmentioning

confidence: 99%

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The Stability of Some Metal Complexes in Mixed Solvents

Mui¹,

McBryde²,

Nieboer³

1974

Can. J. Chem.

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Acidity constants and stability constants of certain metal complexes (nickel(II), zinc(II), and manganese(I1)) with ethylenediamine and glycine were determined a t 25 OC and in 0.1 M ionic strength in mixed aqueous solutions of methanol ( M e O H ) , dioxane (DOX) , acetonitrile (MeCN) , and dimethylformamide ( D M F ) . In general, t h e stability constants of the metal complexes and the first protonation constant of glycine increase with increasing composition of the co-solvent in the orderThe protonation constants of ethylenediamine pass through a minimum at some particular solvent composition, while the second protonation constant of glycine exhibits behavior characteristic of the particular solvent employed.These results are discussed in terms of medium and solvent effects and properties o f the solvent that might affect these, but find more satisfactory explanation in terms o f solvent displacement during the association reactions. The observations can be accounted for in terms of a complete equilibrium constant incorporating the concentration (activity) of each solvent substance. . En gtntrale, les constantes de stabilitt des complexes de mttaux et la constante de la premiere protonation de la glycine sont croissantes quand la composition de leur solvant augmente selon I'ordreLes constantes de protonation de l'tthyltnediamine passe par u n minimum B u n e certaine composition particulitre du solvant, alors que la constante de la seconde protonation de la glycine manifeste un comportement caracttristique du solvant particulier utilisi.Ces rtsultats sont discutts en termes du.milieu, des effets du solvant et des propritt6s du solvant qui pourraient influencer ces derniers; mais ils sont expliquts, de fafon plus satisfaisantes, en termes de dtplacement de solvant durant les rtactions d'association. Les observations peuvent Btre interprtties en termes de constante d'tquilibre complet incluant la concentration (activitt) de chaque substance de solvant.[ Introduction The possibility of utilizing mixed solvents to improve analytical methods involving complex formation have been noted elsewhere (1). Furthermore, studies of equilibrium and kinetics in mixed solvents may be of assistance in interpreting the role of solvent in inorganic reactions. Previous studies of the solvent effect on complex equilibria have been concerned mainly with simple organic acids and metal chelates in selected solvents such as dioxane and alcohols of low molecular weight. Of the few metal ions and ligands studied, the metal complexes increased in stability as the concentration of non-aqueous solvent (co-solvent) increased. This trend also held good for protonation constants of ligands with a carboxylate group, but those with amine groups behaved differently. So far no systematic studies in different solvents with a wide range of solvent compositions have been made.As part of a larger study of free-energy correlations in coordination chemistry we have undertaken the measurement of complex equilibria for three metal ions (NiZt, zn2', an...

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Section: Displacement Of Solvent Moleculesmentioning

confidence: 99%

Section: Displacement Of Solvent Moleculesmentioning

confidence: 99%

The Stability of Some Metal Complexes in Mixed Solvents

Mui¹,

McBryde²,

Nieboer³

1974

Can. J. Chem.

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“…There have been a number of reports in the pharmaceutical and chemistry literature on protonation of organic ligands in cosolvent solutions ( − ). Several authors have also studied metal complexes in mixed solvents ( − ); however, these investigators have not considered environmentally relevant systems. Additionally, organic solvents such as MeOH have been studied as model biological membranes in an effort to elucidate the transfer processes of complexed metal cations across the membrane ().…”

Section: Introductionmentioning

confidence: 99%

Stability of Metal−Organic Complexes in Acetone− and Methanol−Water Mixtures

Xue

Traina

Hille

1996

Environ. Sci. Technol.

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Contamination of soils and groundwaters by trace metals, organic ligands, and organic solvents has been identified at some DOE sites and hazardous landfills. Complexation of metal ions with organic ligands impacts the transport and fate of these contaminants. In this study, aqueous potentiometric titration was extended to cosolvent-water solutions to examine the effects of cosolvents on complexation stability. In H 2 O-acetone and H 2 O-methanol solutions, conditional stability constants, K c , increased with increasing organic cosolvent content for complexes between Co-(II) and oxalate, citrate, nitrilotriacetate (NTA), and ethylenediaminetetraacetate (EDTA). In most cases, the value of log K c varied linearly with 1/ (where is the dielectric constant of the solution). The stability of complexes between Cu(II) and EDTA declined as the content of the organic cosolvent increased, and the stability constants for Fe(III)-EDTA complexes exhibited little dependence on the concentration of organic cosolvent. Cupric electron paramagnetic spin measurements showed that the bonding between Cu and EDTA was more ionic than covalent, consistent with the linear dependence of log K c on the value of 1/ .

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“…stant. Faraglia et al(27) proposed a chemical model for the interpretation of the changes in equilibrium constants in binary solvent mixtures wherein the eliminated coordinated water is also considered. Extension of Marshall's(28) concept of the complete equilibrium constant (KM'ml) to aquo-organic media leads to KM'ml = KMml[H20]m(14) where [H2OJm is the concentration of water in binary solvent i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d .…”

mentioning

confidence: 99%

Chemometric investigation of complex equilibria in the solution phase. 3. Chemical models for the complexation of nickel(II) with adipic acid dihydrazide and 2-furoic acid hydrazide in water-N,N'-dimethylformamide and water-dioxane media. Correlation with solvent parameters

Babu¹,

Rao²

1992

J. Chem. Eng. Data

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The stability constants of binary complexes of adipic acid dihydrazide or 2-furoic acid hydrazide with Ni(II) in water-NjAP-dimethylformamide or water-dioxane (10-60% (vol/vol)) were determined pH metrically. The titrand consists of the mineral acid, ligand, and metal ion solutions in water-cosolvent mixtures. The hydrogen ion activities were measured using sodium hydroxide as titrant. The chemical models which gave the best fit were judged using residual analysis. The different trends for the distribution of species (MLH, ML, ML2H, and ML2) in the presence of varying amounts of cosolvent were explained on the basis of electrostatic interactions and specific solute-solvent and solvent-solvent contributions. In order to ascertain the accuracy of stability constants, the simultaneous effect of errors in the ingredient concentrations and electrode parameters was studied using three-dimensional plots. It was found that perturbation in pKw and total initial volume has a negligible effect. The robustness of the computer program MINIQUAD75 to refine the stability constants for wild initial guess values was investigated.

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Potentiometric studies in mixed solvents, II Complexes of Nickel(II), Copper(II) and zinc(II) with pyridine, ethylenediamine and glycine

Cited by 30 publications

References 15 publications

The Stability of Some Metal Complexes in Mixed Solvents

The Stability of Some Metal Complexes in Mixed Solvents

Stability of Metal−Organic Complexes in Acetone− and Methanol−Water Mixtures

Chemometric investigation of complex equilibria in the solution phase. 3. Chemical models for the complexation of nickel(II) with adipic acid dihydrazide and 2-furoic acid hydrazide in water-N,N'-dimethylformamide and water-dioxane media. Correlation with solvent parameters

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