Stability constant of the trisglycinto metal complexes

The stability constants of iron, manganese, cobalt, and nickel complexes of glycine have been determined in aqueous solution by potentiometric titration with standard sodium hydroxide solution. The values of the stepwise stability constants were obtained by ORIGIN ‘50’ program. The overall stability constants of the complexes were found to be similar. Keywords: Glycinato, titration, stepwise stability constants, origin ‘50’ and toxicit

Synthesis, characterization of biologically active N, N’ - Bis(4-benzeneazosalicylidene)-o-phenylenediiminatocobalt(ii) complex

A Schiff base was prepared as reported, its cobalt(II) complex was  synthesized by refluxing ethanolic mixture of the prepared schiff base and cobalt(II) chloride. The cobalt(II) Schiff base complex synthesized is brown, of percentage yield 65% and has decomposition temperature of 258oC. The Schiff base and N, N’ - bis(4-benzeneazo salicylidene)-o-phenylenediiminatocobalt(II) complex were characterized by solubility, melting point/decomposition temperature, molar conductivity, elemental analysis, IR spectra, bioassay and potentiomentry. The Schiff base and itscobalt(II) complex are slightly soluble in methanol and ethanol but are readily soluble in DMSO and DMF. The molar conductance measurement of the complex determined is 4.6 ohm-1cm2mol-1, revealing its non electrolytic nature. The infrared spectral data of the ligand showed a bandat1590cm-1, which is attributed to v(C=N) stretching frequencies. The same band is observed in the synthesized cobalt(II) Schiff base complex, suggesting that the Schiff base is coordinated to the cobalt(II) Schiff base complex. The bands in the regions 585cm-1 and 511cm-1 in the complex are assigned to v(Co-N) and v(Co-O) stretching vibrations confirming the coordination of the Schiff base to the manganese(II) ion. The elemental analysis result of the complex is consistent with 1:1 metal to Schiff base ratio. The dissociation constant of the determined is 11.67, indicating a week acid. The average number of Schiff base coordinated to cobalt ion is one, the stability constant and Gibbs free energy of the complex  compound are 3.1x1011 and -64.15 KJmol-1, respectively, suggesting that the complex is very stable. The antifungal and antibacterial tests carried out on the Schiff base and its iron(II) complex showed good activity.Keywords: 4 –(Benzeneazo) Salicylaldehyde, Potentiometry, complex  compound, schiff base, molar conductance and solubility

Spectroscopic and Potentiometric Studies of N-(2- Hydroxybenzyl)-L-&#945-Valine Cobalt (II) Complex

A Schiff base was prepared from the reaction of 2-hydroxybenzylaldehyde and L-valine. The reaction of the Schiff base and cobalt (II) chloride formed 2-hydroxybenzylaldehyde and L-valine cobalt (II) complex. The Schiff base is crystalline white and has a yield of 66%. The prepared complex is pale brown, has a yield of 68% and decomposition temperature of 274oC. The Schiff base and its cobalt (II) complex are insoluble in most common solvents however they are soluble in ethanol-water mixture. The molar conductance of the cobalt (II) Schiff base complex compound determined is 5.2 ohm cm2 mol-1. The infra-red spectra of the Schiff base showed band in the range 1480 -1520cm-1, assignable to v(C=N) stretching vibrations, the same band is observable in the cobalt (II) Schiff base complex. The broad band in the range 3270 - 3420cm-1 observed in Schiff base is assigned to v(O-H) stretching vibrations. The dissociation constant (pKa) of N – (2 – hydroxybenzyl) - L -a - valine Schiff base determined is 8.84. The average number of the Schiff base to cobalt (II) ion is 1 (one)

Potentiometric studies of Nickel (II) and copper (II) acetyl acetonato complexes

The dissociation constant pKa of acetylacetone has been determined potentiometrically. The pKa value obtained is 9.40, indicating a weak acid. The stability constants of the complex compounds formed from the reaction of nickel (II) and copper (II) with acetylacetone determined using potentiometer are 6.32x1015 and 2.82x1014, respectively. Similarly, the number of acetylacetonato ligands coordinated to each metal ion determined potentiometrically is 3. Key words: Potentiometry, Acetylacetone, Dissociation and Stability Constants

Determination and stability constants of Manganese (II) amino acid complexes

The stepwise and the overall stability constants of the complexes formed by manganese (II) ion and twelve (12) amino acids have been determined. The dissociation constants, pKa, of the amino acids determined are; alanine (10.29), arginine (12.02), asparagine (9.39), glycine (9.87), histidine (7.01), lysine (9.28), methionine (9.68), phenyalanine (9.61), proline (10.54), threonine (10.31), tryptophan (9.77), and valine (9.99). The average number of amino acids coordinated to manganese (II) ion determined is 3. The Stepwise Stability Constants of manganese (II) amino acid complexes determined were found to decrease in the order K1 > K2 > K3 for all the complexes. The values of the overall stability constants of the complexes obtained are relatively high indicating good stability for the complexes. Keywords: Amino acids, dissociation constant, potentiometry, stability constan

Potentiometric Study of Trismethioninato Complexes of some Essential Transition Metals

Potentiometric study of methionine complexes of chromium, manganese, iron, cobalt and nickel was carried out in aqueous media by titrating with standard sodium hydroxide solution. The values of the stepwise and overall stability constant were obtained by new computational method, ‘ORIGIN 50’. The values of the stepwise stability constants of the complexes were found in general to follow the order K1 > K2 > K3 and that of the overall constants, logβ to be in the range 26.55 – 28.73

Synthesis, Antibacterial and Antifungal Investigations of Mn (Ii) Complexes with Schiff Bases Derived From 2 – Hydroxy – 1 – Naphthaldehyde and Some Aliphatic Diamines

Schiff base ligands derived from 2-hydroxy-1-naphthaldehyde and some aliphatic diamines were synthesized and characterized. Each of the ligands was used to form complex with Mn (II). Solubility, elemental analyses and IR spectra were carried evaluated. Elemental analyses of the complexes for C, N and H revealed 1:1 metal to ligand ratio. Antibacterial and antifungal activities were determined. Disc diffusion method was employed for these antimicrobial assays against four pathogenic bacteria (Escherichia coli, Salmonella typhi, Proteus sp. and Klebsiella pneumonae) and two fungi (Mucor sp. and Rhizopus sp.). It was found that the ligands and the complexes showed different activities against the isolates. The complexes showed higher activity than the free ligands. Keywords: Schiff base, diamine, ligand, complex, isolates, analysi

Spectroscopic and potentiometric studies of Co (II) and Ni (II) complexes with N-(I-Morpholinobenzyl) semicarbazide

The Schiff base complexes of cobalt(II) and nickel(II) were synthesized by refluxing the mixture of ethanolic solutions of the Schiff base and metal(II) chlorides, respectively. The complexes were characterized by gravimetry, spectrophotometry, potentiometry, molar conductance and infrared analyses. The N-(1- morpholinobenzyl)semicarbazide Schiff base and its complex compounds are not soluble in water, slightly soluble in most common organic solvents but are readily soluble in methanol and ethanol. The molar conductance of the cobalt (II) and nickel(II) schiff base complexes determined are in the range 5.38 - 6.03 ohm-1cm2mol-1, suggesting their nonelectrolytic nature. The dissociation constant, pKa, of N-(1- morpholinobenzyl)semicarbazide Schiff base determined is 5.40. The standard Gibb’s free energy of cobalt(II) and nickel(II) N-(1- morpholinobenzyl)semicarbazide Schiff base complexes determined are -70.78KJmol-1 and - 68.06KJmol-1, respectively. The ratio of metal ion to Schiff base determined potentiometrically and spectrophotometrically for the complex compounds is 1: 2. The IR spectrum of the Schiff base shows bands observable in the two Schiff base complex compounds, indicating the coordination of the Schiff base to the cobalt(II) and nickel(II) ions. Key Words: Schiff base, azomethine, benzyldehyde, potentiometry, spectrophotometry, morpholine

Synthesis and characterisation of Manganese (II), Cobalt (II), Nickel (II) and Copper (II) N,N'-bis(Benzoin)ethylenediiminato complexes

The manganese (II), cobalt (II), nickel (II) and copper (II) complexes of N, N’ –bis(benzoin)ethylenediiminato have been prepared and characterized by infrared, elemental analysis, conductivity measurements and solubility. The potentiometric, and elemental analyses studies of the complexes revealed 1:1 metal to ligand ratio. Key words: Spectrophotometry, potentiometry, N, N’ – bis(benzoin)ethylenediimine, complexes

Studies on Bis(Para Anisidine Acetylacetonato) Nickel (II) Complex

Schiff base was prepared from the reaction of para anisidine and acetylacetone. Bis(para anisidineacetylacetonato)nickel(II) complex was synthesized by the reaction of the prepared para anisidineacetylacetone ligand and nickel(II) chloride. The prepared Schiff base is orange yellow, has a yield of 61.90% and melting point of 86oC. The complex prepared is red, has a yield of 71% and decomposition temperature of 270oC. The para anisidineacetylacetone ligand is soluble in water and most organic solvents, similarly, its nickel(II) complex compound is soluble in most solvents except water and methanol, in which it slightly soluble. The molar conductance of bis(para anisidineacetylacetonato)nickel (II) complex compound determined is 4.70 ohm-1 cm2mol-1, suggesting that the complex is non-electrolyte. The infra-red spectral data of para anisidine and acetylacetone base showed a medium size band in the range 1595 – 1630cm-1, attributable to v(C=N) stretching vibrations, the same band is observable in the nickel(II) complex, indicating coordination of the ligand to the nickel(II) ion. The broad band in the range 3257 - 3420 cm-1 observed in para anisidineacetylacetone ligand is assigned to v(O-H) stretching vibrations, which is absent in anisidineacetylacetonato)nickel(II) complex, as a result of deprotonation of the para anisidineacetylacetone on coordination to the nickel(II) ion. The dissociation constant (pKa) of para-anisidine acetylacetone determined is 12.66. The stability constant of anisidineacetylacetonato)nickel (II) complex compound determined is 1.29x106 and the corresponding Gibb’s free energy of complex is -3.48 x104 KJ per mole. The average number of para anisidine ligand coordinated to nickel(II) ion determined using potentiometer is 2, suggesting a four coordinate complex compound. Keywords: Anisidineacetylacetone, complex compound, stability constant, potentiometry