Binary Complexes Of Co Research Articles

Conductometric, Spectrophotometric and Computational Investigation of Binary and Ternary Complexes of Co(II) and Cu(II) Bivalent Metal Ions with L-Valine Amino Acid and Paracetamol Drug

The conductivity and spectrophotometry techniques were employed to evaluate the binary and ternary complexes of the divalent metal ions Co(II) and Cu(II) with the physiologically relevant amino acid L-Valine (Val) and the analgesic paracetamol. The conductivity experiments were generated by direct conductivity equation from conductivity titration data, while the spectrophotometry experiments were performed using the continuous variations approach (Job's method). Both techniques were accomplished in an aqueous solution with a constant concentration of 0.004 M of divalent metal ions at (40.0 ± 0.1) °C. The binary complexes of Co(II) and Cu(II) have a 1:1 binding ratio of metal to paracetamol (M:para). However, the binary complexes of Co(II) and Cu(II) have metal: Val binding ratios of either 1:1 or 2:1. In addition, the Cu(II) binary complexes of both ligands have a higher stability constant than Co(II) binary complexes of paracetamol and Val ligands, which was in good agreement with the Rossotti-Willime order. The ternary complexes of Co(II) and Cu(II) have a 1:1:1 binding ratio of metal to paracetamol: L-valine, (M:para:Val). The stability constants were in order: The ternary metal complexes > The binary metal-L-Val complexes > The binary metal-para complexes. DFT (Density Functional Theory) simulations were used in order to gain a better understanding of the molecular interactions of Co(II) and Cu(II) divalent metal ions with L-Val and paracetamol. Calculations were made on the electronic structure, HOMOs and LUMOs, and molecular geometry of complexes and their corresponding ligands. The findings unequivocally demonstrate that the metal ion is bound to both the amide nitrogen in the paracetamol ligand and the oxygen atom of the carbonyl group. Moreover, the metal ion is bound to the nitrogen atom of the amine NH2 group and the oxygen atom of the hydroxyl group for the L-Val ligand.

Synthesis, characterization, biological activity of Schiff bases derived from 3-bromo-4-methyl aniline and its potentiometric studies with Cu(II), Co(II) and Ni(II) ions

Schiff bases namely, 3-bromo-4-methyl-N-(2-nitrobenzylidene)aniline; 3-bromo-4-methyl-N-(2,4,5-trimethoxybenzylidene)aniline; 3-bromo-N-(4-methoxybenzylidene)-4-methylaniline and N-(3-bromo-4-methylphenyl)-1-(1H-indol-3-yl)methanimine have been synthesized and characterized by elemental analysis, FT-IR, Mass and 1H-NMR spectroscopy. Schiff bases have been screened for Antimicrobial activity against bacteria and fungi by using MIC determination. Binary complexes of Co(II), Ni(II) and Cu(II) with Schiff bases in solution have been studied potentiometrically in 60:40 % (V/V) 1,4-dioxane-water system at constant temperature 27˚±0.5˚C and at an ionic strength of 0.1 M KNO3. The order of stability constant of formed binary complexes in solution was examined.

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine in anionic micellar medium

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine (Phe) in the presence of water–anionic surfactant mixtures in the concentration range of 0.0–2.5% w/v SLS has been studied pH-metrically at a temperature of 303 K and at an ionic strength of 0.16 mol L−1. The selection of best fit chemical models is based on statistical parameters and residual analysis. The predominant species detected were ML, ML2, and ML2H2 for Co(II), Ni(II), and Cu(II). The trend in the variation of stability constants with the mole fraction of SLS was explained on the basis of electrostatic and non-electrostatic forces. Distribution of the species with pH at different compositions of SLS–water media was also presented.

Potentiometric and Theoretical Studies of (2Z, 3Z)-2H-benzo[b][1,4]thiazine-2,3(4H)-dionedioxime with Some Divalent Transition Metal Ions

The protonation equilibria of (2Z, 3Z)-2H-benzo[b][1,4]thiazine-2,3(4H)-dionedioxime (BTDH2) together with the equilibria of its bis- binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) were investigated potentiometrically. The investigation was carried out at 25 ± 0.1 °C, in aqueous solution, with a constant ionic strength of 0.100 mol·dm−3 NaCl. The protonation constants of the ligand together with the stability constants of a variety of complexes were determined potentiometrically in 10 % ethanol–water mixed solution using the SUPERQUAD computer program. Theoretical calculations were set up to assist in understanding the protonation sequence in the ligand molecule via the semi-empirical molecule orbital method of parameterized model number 3. Results are discussed in connection to the basicity of the donor atoms and structural arrangement of the ligand. Although BTDH2 has two dissociable protons, four protonation constants can be measured under the experimental conditions presented. These four protonation constants (as log10 βs) are 10.245, 19.397, 22.414 and 25.176.

Stability of binary complexes of L-aspartic acid in dioxan–water mixtures

Speciation of binary complexes of Co(II), Ni(II) and Cu(II) with L-aspartic acid in (0–60% v/v) 1,4-dioxan (Dox)-water mixtures was studied pH metrically at 303±0.1 K and at an ionic strength of 0.16 M. The models contained ML, ML2, ML2H2, ML2H3 and ML2H4 species. The trend in the variation of stability constants with Dox content was explained on the basis of electrostatic and non-electrostatic forces. Distribution of the species with pH at different compositions of Dox-water media was also presented. KEY WORDS: Binary complexes, Stability constants, Aspartic acid, Speciation, Dioxan Bull. Chem. Soc. Ethiop. 2013, 27(3), 367-376.DOI: http://dx.doi.org/10.4314/bcse.v27i3.5

Speciation of binary complexes of Co(II), Ni(II) and Cu(II) with L-aspartic acid in propylene glycol–water mixtures

Speciation of binary complexes of Co(II), Ni(II) and Cu(II) with L-aspartic acid in (0-60% v/v) propylene glycol-water mixtures was studied pH metrically at 303.0±0.1 K and at an ionic strength of 0.16 mol L-1. The binary species refined were ML, ML2, ML2H2, ML2H3 and ML2H4. The stabilities of the complexes followed the Irving-Williams order i.e.Co(II) <Ni(II) < Cu(II). The linear variation of stability constants as a function of dielectric constant of the medium indicated the dominance of electrostatic forces over non-electrostatic forces. Some species were stabilised due to electrostatic interactions and some were destabilised due to the decreased dielectric constant. The order of ingredients influencing the magnitudes of stability constants due to incorporation of errors in their concentrations was alkali > acid > ligand > metal. Equilibria for the formation of binary complexes were proposed based on the forms of the ligand and their existence at different pH values.

Speciation studies of Co(II), Ni(II) and Cu(II) complexes of L-valine in acetonitrile–water mixtures

Chemical speciation of binary complexes of Co(II), Ni(II) and Cu(II) with L-valine in 0.0-60.0% v/v acetonitrile-water mixtures was studied pH-metrically at an ionic strength of 0.16 mol L-1 at 303.0 K. The existence of different binary complexes was established from the modelling studies, using the computer program MINIQUAD75. The appropriateness of the model was ascertained by studying the effect of errors in concentrations of the reagents. The trend in variation of stability constants with change in the permittivity of the medium is explained on the basis of electrostatic and non-electrostatic forces. The species distribution diagrams and the plausible equilibria for the formation of the species are also presented.

Speciation of L-aspartic acid complexes of Co(II), Ni(II), Cu(II) and Zn(II) in acetonitrile- and ethylene glycol-water mixtures

Chemical speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid was investigated pH-metrically in acetonitrile- and ethylene glycol-water mixtures. The stability constants were calculated using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The models for the binary species contained ML2H2, ML2H and ML2 for Co(II) and Zn(II), ML, ML2H2 and ML2 for Ni(II) and Cu(II) in acetonitrile- and ethylene glycol-water mixtures. The trend in variation of stability constants with change in the dielectric constant of the medium was explained on the basis of electrostatic and non-electrostatic forces. Distribution of the species with pH at different variations (0.0-60.0% v/v) in acetonitrile- and ethylene glycol-water mixtures was also presented.&#160;KEY WORDS: Complex equilibria, L-Aspartic acid, Acetonitrile, Ethylene glycol, MINIQUAD75&#160;Bull. Chem. Soc. Ethiop. 2012, 26(2), 239-247.DOI: http://dx.doi.org/10.4314/bcse.v26i2.7

Effect of dielectric constant of medium on chemical speciation of L-histidine complexes of Co(II), Ni(II) and Cu(II)

Chemical speciation of binary complexes of Co(II), Ni(II) and Cu(II) ions with L-histidine have been studied pH metrically in the concentration range of 0–60% v/v DMSO-water mixtures maintaining an ionic strength of 0.16 M at 303 K. Alkalimetric titrations were carried out in different relative concentrations of metal and histidine. Stability constants of various models of binary complexes were refined with MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The species detected are MLH, ML­ 2 , ML 2 H, ML 2 H 2 and ML 2 H 4 for Co(II); ML­ 2 , ML 2 H, ML 2 H 2 and ML 2 H 4 for Ni(II); and MLH, ML 2 , ML 2 H and ML 2 H 2 for Cu(II). The chemical speciation, metal bioavailability and transportation are explained based on the distribution diagrams. KEY WORDS : L-Histidine, Chemical speciation, Essential metals, Binary complexes, Bioavailability, DMSO Bull. Chem. Soc. Ethiop. 2012 , 26(2), 227-238. DOI: http://dx.doi.org/10.4314/bcse.v26i2.6

&lt;b&gt;Formation of binary complexes of Co(II), Ni(II) and Cu(II) with L-DOPA in dioxan-water mixtures&lt;/b&gt;

Complexation of essential metal ions with (S)-2-amino-3-(3,4-dihydroxyphenyl) propanoic acid (dopa) in (0-60% v/v) dioxan-water mixtures has been studied pH-metrically at a temperature of 303 K and an ionic strength of 0.16 M. The existence of different binary species was established from modeling studies using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters like crystallographic R factor and sum of the squares of residuals in mass-balance equations. The models for binary complex systems contain the chemical species ML, ML2, MLH, ML2H and ML2H2 for Co(II), Ni(II) and Cu(II) in dioxan-water mixtures. The trend in the variation of stability constants with change in the mole fraction of the medium was explained based on electrostatic and non-electrostatic forces. Distribution of the species with pH at different compositions of dioxan-water mixtures was also presented.KEY WORDS: Binary species, Stability constants, Metal, Dopa, Dioxan, pH-metryBull. Chem. Soc. Ethiop. 2011, 25(1), 43-52.

Study of binary complexes of Cu(II), Ni(II) and Co(II) with sulfamethazine by voltammetry

Cyclic voltammetry (CV) and square-wave voltammetry (SWV) techniques have been used to study the binary complexes of Co(II), Ni(II) and Cu(II) with sulfamethazine (SMZ) at a static mercury drop electrode (SMDE) in 0.04 M Britton-Robinson (B-R) buffer. SMZ gave three peaks at 0.01, −1.32 and −1.55 V. Cu(II)-SMZ complex was recognized by a cathodic peak at −0.38 V. Ni(II)-SMZ complex was reduced at more positive potential (−0.77 V) than that of the hydrated Ni(II) ions (−1.08 V). Co(II)-SMZ complex is investigated at pH 7 and 8. The Co(II) complex at pH 7 is appeared as a shoulder at −1.19 V, whereas this peak becomes a well-separated form at pH 8. The study indicated that the SMZ serves as a catalyst in the reduction of Co(II) and Ni(II) ions. From electronic spectra data of the complexes, their stoichiometries of 1: 2 (metal-ligand) in aqueous medium are determined. The stability constants of the complexes are in agreement with the Irwing-Williams series (Co < Ni < Cu).

Speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid in anionic, cationic and neutral micellar medium

Chemical speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid was investigated pH-metrically in (0.5–2.5%) anionic, cationic and neutral micellar media. The stability constants were calculated using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The models for the binary species contained MLH, ML2 and ML2H for Co(II), ML, MLH, ML2 for Ni(II) and Cu(II), ML2,ML2H and ML2H2 for Zn(II) in anionic, cationic and nonionic micellar media The trend in variation of stability constants with change in the mole fraction of the medium was explained on the basis of electrostatic and non-electrostatic forces. Distributions of the species with pH at different composition of micellar media were also presented.

Effect of micelles on the chemical speciation of binary complexes of Co(II), Nii(II), Cu(II) and Zn(II) with succinic acid

Speciation of Co(II), Ni(II), Cu(II) and Zn(II) complexes with succinic acid in the presence of anionic, cationic and non-ionic surfactants at an ionic strength of 0.16 mol dm-3 and temperature 303 K were investigated pH metrically. The existence of different binary complex species was established from modelling studies using the computer program MINIQUAD75. The decreased stability of the complexes with increasing micellar content was explained by electrostatic forces. The influence of the micelles on the chemical speciation is discussed based on the mole fraction of the medium. Distribution diagrams of various species of the complexes in relation to pH are presented.