scholarly journals Electrometric Investigation of the Nature and Stability of Mixed Ligand Complexes of L-Ornithine and 1,10-Phenanthroline with Some Essential Metal Ions in Aqua-TBAB or PEG-400 Surfactant

2021 ◽  
Author(s):  
Atnafu Guadie Assefa ◽  
Molla Tefera Negash ◽  
Mulugeta Legesse Akele ◽  
Bewketu Mehari Workneh ◽  
Ayal Adugna Mesfin ◽  
...  
Keyword(s):  
Metal Ions ◽  
Stability Constants ◽  
Tetrabutylammonium Bromide ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Essential Metal ◽  
Peg 400 ◽  
Chemical Models ◽  
Binary Complexes ◽  
The Stability

Abstract Background Despite the availability of information about the effect of aqua-surfactants media on the stability of binary complexes, data related to mixed ligand complexes of Phen and Orn with essential metals in aqua-surfactant medium is scarce. The aim of this study was, to determine the stabilities of the mixed ligand complexes of essential metal ions (Co2+, Ni2+, Cu2+) with Phen and Orn in aqua-TBAB and PEG-400 surfactants with an eye on the prediction of the bioavailability of the metal complexes. Results Complexes of some essential metal (M) ions (Co2+, Ni2+, Cu2+) of L-ornithine (L) and 1,10-phenanthroline (X) ligands in various concentrations (0.0–2.5% v/v) of aqueous tetrabutylammonium bromide (TBAB) or polyethylene glycol-400 (PEG-400) surfactant were synthesized pH-metrically at 298 K and 0.16 mol L− 1 ionic strength. The relative amounts of L:M:X were 2.5:1.0:2.5; 5.0:1.0:2.5; 2.5:1.0:5.0. The data acquisition of acid-base equilibria and determination of stability constants were performed using MINIQUAD75 algorithm. The distribution patterns of the complexes with varying pH and compositions of surfactants were presented from the plots of SIM run data. Conclusions The best fit chemical models were found to be MLXH, MLX2H in the lower pH, and MLX, ML2X in the higher pH ranges for all the metals. The logged values of stability constants decreased linearly with increasing concentrations of surfactants, indicating the dominance of electrostatic factors. The log of the disproportionation constant and the change in log values of the mixed ligand constant indicated additional stability of the mixed ligand complexes, compared to the parent binary complexes due to interactions outside the coordination sphere. This makes the mixed ligand complexes more amenable to metal ion storage and transport and threw light to have information on the less stable binary complexes easily bioavailability while the mixed ligand complexes could be stored and transported in the bio-fluids. Significant change on the magnitudes of the stability constants, high values of standard deviation and rejection of some of the proposed chemical models were observed due to pessimistic error, indicating the sufficiency of the models to represent the data and accuracy of the method employed.

scholarly journals Stability Constants of Mixed Ligand Complexes of Transition Metal(II) Ions with Salicylidene-4-methoxyaniline as Primary Ligand and 5-Bromosalicylidene-4-nitroaniline as Secondary Ligand

2011 ◽  
Vol 8 (4) ◽  
pp. 1765-1769 ◽  
Author(s):  
N. G. Nadkarni ◽  
K. V. Mangaonkar
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Water Medium ◽  
Binary And Ternary Complexes ◽  
Binary Complexes ◽  
The Stability ◽  
Secondary Ligand

Binary and ternary complexes of the type M-Y and M-X-Y [M = Mn(II), Ni(II), Cu(II) and Zn(II); X = salicylidene-4-methoxyaniline and Y=5-bromosalicylidene-4-nitroaniline] have been examined pH-metrically at 27±0.5 °C and at constant ionic strength, μ= 0.1 M (KCl) in 75 : 25(v/v) 1,4-dioxne-water medium. The stability constants for binary (M-Y) and ternary (M-X-Y) systems were calculated. The relative stability (Δ log KT) values of the ternary complexes with corresponding binary complexes for all the metal(II) ions in the present study found to be negative indicating that ternary 1:1:1 (M-X-Y) complexes are less stable than binary 1:1 (M-Y) complexes. In the ternary system studied, the order of stability constants of mixed ligand complexes with respect to the metal ions was found to be Cu(II) > NI(II) > Mn(II) > Zn(II); which is same as in the corresponding binary (M-Y) systems.

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu2+-Oligoglycine Systems

1972 ◽  
Vol 27 (4) ◽  
pp. 353-364 ◽  
Author(s):  
Helmut Sigel ◽  
Rolf Griesser ◽  
Bernhard Prijs
Keyword(s):  
Coordination Sphere ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Amide Group ◽  
Amide Proton ◽  
Mixed Ligand Complexes ◽  
Apical Position ◽  
Binary Complexes ◽  
The Stability ◽  
Ph Range

The stability constants of the binary Cu2+ complexes of glycine amide, diglycine, diglycine amide, triglycine, and tetraglycine were determined, as were those of the mixed-ligand Cu2+ systems containing 2,2′-bipyridyl and one of the mentioned oligoglycines. The results evidence that all these complexes have the same structure and, therefore, the binding sites of the ligands have to be the terminal amino group and the oxygen of the neighbored amide group. The stability differences between the ternary and the binary complexes are in agreement with this interpretation. It is of interest to note that these ternary complexes are significantly more stable than expected on statistical reasons. With increasing pH, the amide groups in the binary complexes are successively deprotonated. Thus, with tetraglycine finally all three amide protons are displaced, and the amide nitrogens are bound to the square-planar coordination sphere of Cu2+. As in the Cu2+-2,2′-bipyridyl 1 : 1 complex, only two coordination positions are left for the binding of the oligoglycine, in the tenary complexes, only one amide group can be deprotonated. An increase in pH with deprotonation of other amide groups leads to a displacement of 2,2′-bipyridyl, i. e. the simple binary complexes result. No evidence could be observed for the coordination of a deprotonated amide group to an apical position of the coordination sphere of Cu2+. Additionally, while the displacement of the first amide proton in the several binary Cu2+ oligoglycine complexes occurs over a large pH range (4 to 7), the deprotonation in all the mixed-ligand complexes takes place at pH approximately 8.

scholarly journals Stability Constants of Mixed Ligand Complexes of Transition Metal(II) ions with N-(2-hydroxybenzylidene)-2,3-dimethylaniline as Primary Ligand and N-(2-hydroxy-1-naphthylidene)-4-nitroaniline as Secondary Ligand

2011 ◽  
Vol 8 (2) ◽  
pp. 859-862 ◽  
Author(s):  
A. K. Mapari ◽  
K. V. Mangaonkar
Keyword(s):  
Ionic Strength ◽  
Transition Metal ◽  
Stability Constants ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Water Medium ◽  
Binary And Ternary Complexes ◽  
The Stability ◽  
Secondary Ligand

Binary and ternary complexes of the type M-Y and M-X-Y [M=Co(II), Ni(II), Cu(II) and Zn(II); X=N-(2-hydroxybenzylidene)-2,3-dimethylaniline and Y =N-(2-hydroxy-1-naphthylidene)-4-nitroaniline] have been examined pH-metrically at 27±0.5 °C and at constant ionic strength, μ=0.1 M (KCl) in 75:25(v/v) 1,4-dioxne-water medium. The stability constants for binary (M-Y) and ternary (M-X-Y) systems were calculated.

scholarly journals Mixed ligand complexes of essential metal ions with L-glutamine and succinic acid in SLS-water mixtures

2012 ◽  
Vol 77 (4) ◽  
pp. 453-463 ◽  
Author(s):  
Hima Bindu ◽  
Nageswara Rao
Keyword(s):  
Succinic Acid ◽  
Electrostatic Interactions ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Statistical Parameters ◽  
Chemical Models ◽  
Chelate Effect ◽  
Binary Complexes ◽  
Best Fit

Speciation of mixed ligand complexes of Co(II), Ni(II) and Cu(II) with L-glutamine and succinic acid was studied in varying amounts (0.0-2.5% w/v) of sodium lauryl sulphate in aqueous solutions maintaining an ionic strength of 0.16 mol L-1 (NaCl) at 303.0 K. Titrations were carried out in the presence of different relative concentrations (M : L : X = 1 : 2 : 2, 1 : 4 : 2, 1 : 2 : 4) of metal (M) to L-glutamine (L) to succinic acid (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 ML2X, MLX, MLXH and MLXH2 for Co(II), Ni(II) and Cu(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 SLS and plausible equilibria for the formation of species were also presented.

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