Some factors influencing mixed complex formation

Martin, R. Bruce; Prados, Ronald A.

doi:10.1016/0022-1902(74)80643-3

Cited by 111 publications

(34 citation statements)

References 34 publications

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“…However, it is worth emphasizing that the formation of the ternary complexes is not favoured over the corresponding binary ones, as occurs in the case of the oxydiacetate cobalt(II) and nickel(II) complexes [3]. This conclusion can be drawn from the assessment of the relative stability of the ternary and the corresponding binary complexes, according to the following equation [16]: (3) (4) where is the logarithm of stability constant represented by the equilibrium ML + B = MLB and . In these studies the negative values of ∆logK were found for all the systems indicating the lack of cooperative interactions between the ligands in the coordination sphere of the metal ion.…”

Section: Resultsmentioning

confidence: 99%

Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

et al. 2014

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A potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)-and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2'-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288-303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2-0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

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Section: Resultsmentioning

confidence: 99%

Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

et al. 2014

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“…A value greater than this accounts for the extra stability of MLX. Another approach (Martin and Prados, 1974) to quantify the stability of ternary complexes was based on the difference in stability (D logK) for the reactions ML with X and M (aq) with L and X, where L is primary ligand and X is a secondary ligand. It is compared with that calculated purely on statistical grounds as given in Equation 2.…”

Section: Resultsmentioning

confidence: 99%

Mixed ligand complexes of toxic metal ions with L-glutamic acid and L-methionine in urea-water mixtures

Rao

Latha

Rao

et al. 2006

Chemical Speciation & Bioavailability

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Speciation of mixed ligand complexes of Pb(II), Cd(II) and Hg(II) with L-glutamic acid and L-methionine was studied in varying amounts (0.0 -36.83%wyv) of urea in aqueous solutions maintaining an ionic strength of 0.16 mol dm À 3 (NaNO 3 ) at 303 K. Titrations were carried out in the presence of different relative concentrations (M : L : X ¼ 1 : 2 : 2, 1 : 2 : 4, 1 : 4 : 2) of metal (M) to L-glutamic acid (L) to L-methionine (X) with sodium hydroxide. Stability constants of ternary complexes were refined with MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The species detected were MLXH for Pb(II), MLX and ML 2 X for Cd(II), and MLX and MLXH 2 for Hg(II). Extra stability of ternary complexes compared to their binary complexes was believed to be due to electrostatic interactions of the side chains of ligands, charge neutralization, chelate effect, stacking interactions and hydrogen bonding. The species distribution with pH at different compositions of urea and plausible equilibria for the formation of species were also presented. The bioavailability of the toxic metal ions is explained based on the speciation.

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“…Another approach (Martin and Prados, 1974) to quantify the stability of ternary complexes was based on the difference in stability (∆log K) for the reactions ML with X and M aq with L and X, where L is the primary ligand (dopa) and X is the secondary ligand (Phen). It is compared with that calculated purely on statistical grounds as given in Eqn (2).…”

Section: Ml2 + Mx2 2mlxmentioning

confidence: 99%

Speciation of ternary complexes of lead(II), cadmium(II) and mercury(II) with L-dopa and phenanthroline in propanediol-water mixtures

Padmaja

2012

Chemical Speciation & Bioavailability

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The formation constants of ternary complexes of title systems have been determined pH-metrically in biologically relevant conditions at an ionic strength of 0.16 mol dm -3 and 303 K. The overall stability constants have been evaluated using MINIQUAD75 computer program. The complexation equilibria have been derived on the basis of species distribution diagram. In the present study L-Dopa and 1, 10-phenanthroline are found to be compatible ligands, proving greater stability of ternary complexes as compared to binary ones. The trend in variation of stability constants with change in dielectric constant of medium is explained on the basis of electrostatic and non-electrostatic forces. Distributions of the species with pH at different compositions of propanediol-water mixtures are also presented. The factors responsible for the compatibility of both the ligands have also been discussed.

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Some factors influencing mixed complex formation

Cited by 111 publications

References 34 publications

Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

Mixed ligand complexes of toxic metal ions with L-glutamic acid and L-methionine in urea-water mixtures

Speciation of ternary complexes of lead(II), cadmium(II) and mercury(II) with L-dopa and phenanthroline in propanediol-water mixtures

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