scholarly journals Computer augmented modelling studies of Pb(II), Cd(II), Hg(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of L-glutamic acid in 1,2-propanediol-water mixtures

2008 ◽  
Vol 73 (12) ◽  
pp. 1169-1180 ◽  
Author(s):  
Rao Vegi ◽  
Latha Muddapu ◽  
Rao Tirukkuvalluri ◽  
Rao Gollapalli
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Glutamic Acid ◽  
Stability Constants ◽  
Chemical Speciation ◽  
Systematic Errors ◽  
Specific Interactions ◽  
Solvent Water ◽  
Modelling Studies ◽  
The Stability

Chemical speciation of Pb(II), Cd(II), Hg(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of L-glutamic acid was studied at 303 K in 0-60 vol. % 1,2-propanediol-water mixtures, whereby the ionic strength was maintained at 0.16 mol dm-3. The active forms of the ligand are + LH3, LH2 and LH-. The predominant detected species were ML, ML2, MLH, ML2H and ML2H2. The trend of the variation in the stability constants with changing dielectric constant of the medium is explained based on the cation stabilizing nature of the co-solvents, specific solvent-water interactions, charge dispersion and specific interactions of the co-solvent with the solute. The effect of systematic errors in the concentrations of the substances on the stability constants is in the order alkali > > acid > ligand > metal. The bioavailability and transportation of metals are explained based on distribution diagrams and stability constants.

scholarly journals Stability Studies of Transition Metal Chelates of 5-Bromosalicylidene-4-methoxyaniline andSalicylidene-2,3-dimethylaniline as Ligands

2011 ◽  
Vol 8 (4) ◽  
pp. 1911-1915
Author(s):  
N. G. Nadkarni ◽  
K. V. Mangaonkar
Keyword(s):  
Ionic Strength ◽  
Transition Metal ◽  
Stability Constants ◽  
Metal Chelates ◽  
Ternary Complexes ◽  
Water Medium ◽  
Stability Studies ◽  
Binary And Ternary Complexes ◽  
Transition Metal Chelates ◽  
The Stability

Binary and ternary complexes of the type M-Y and M-X-Y [M = Mn(II), Ni(II), Cu(II) and Zn(II); X = 5-bromosalicylidene-4-methoxyaniline and Y = salicylidene-2,3-dimethylaniline] 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 Potentiometric and spectrophotometric studies of the complexation of Schiff-base hydrazones containing the pyrimidine moiety

2003 ◽  
Vol 68 (10) ◽  
pp. 729-749 ◽  
Author(s):  
H.S. Seleem ◽  
B.A. El-Shetary ◽  
S.M.E. Khalil ◽  
M. Shebl
Keyword(s):  
Schiff Base ◽  
Ionic Strength ◽  
Thermodynamic Parameters ◽  
Stability Constants ◽  
Elemental Analysis ◽  
Mass Spectra ◽  
Dissociation Constants ◽  
The Stability ◽  
Pyrimidine Moiety ◽  
Metal Ligand

Three Schiff-base hydrazones (ONN ? donors) were prepared by condensation of 2-amino-4-hydrazino-6-methylpyrimidine with 2-hydroxyacetophenone 2-methoxybenzaldehyde and diacetyl to yield 2-OHAHP, 2-OMeBHPand DHP respectively. The structures of these ligands were elucidated by elemental analysis, UV, IR, 1H-NMR and mass spectra. The metal?ligand stability constants of Mn2+, Fe3+,Co2+,Ni2+,Cu2+, Zn2+,Cd2+,UO22+ and Th4+ chelates were determined potentiometrically in two different media (75%(v/v) dioxane?water and ethanol?water) at 283, 293, 303 and 313 K at an ionic strength of 0.05 M (KNO3). The thermodynamic parameters of the 1:1 and 1:2 complexes were evaluated and are discussed. The dissociation constants of 2-OHAHP, 2-OMeBHP and DHPligands and the stability constants of Co2+, Ni2 and Cu2+ with 2-OHAHP were determined spectrophotometrically in 75 % (v/v) dioxane?water.

Interligand interaction in ternary complexes of Zn(II) and Cd(II) with dipeptides and aminoacids

1994 ◽  
Vol 72 (4) ◽  
pp. 1107-1110 ◽  
Author(s):  
Alexander Varghese Vaidyan ◽  
Pabitra K. Bhattacharya
Keyword(s):  
Ionic Strength ◽  
Aqueous Medium ◽  
Computer System ◽  
Stability Constants ◽  
Ternary Complexes ◽  
Binary And Ternary Complexes ◽  
The Stability ◽  
Interligand Interaction

The stability constants of binary and ternary complexes [MA], [Ma2], and [MAL] (where M = Zn(II) or Cd(II); A = glycylglycine, glycyl L-alanine, glycyl L-leucine; L = α-alanine phenylalanine, tyrosine, tryptophan, or L-histidine) in aqueous medium have been determined potentometrically at 25 °C and an ionic strength of 0.2 M NaClO4 (0.2 mol dm−3) using a computer system. It is observed that Δ log K of MAL complexes has low negative or positive values. Probable reasons have been discussed.

The role of divalent cations in the activation of the NADP+-specific isocitrate dehydrogenase from Pisum sativum L.

1977 ◽  
Vol 55 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Robert J. Maloney ◽  
David T. Dennis
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Isocitrate Dehydrogenase ◽  
Divalent Cations ◽  
Free Form ◽  
Saturation Kinetics ◽  
The Difference ◽  
The Stability ◽  
Kinetics Of

A divalent cation electrode was used to measure the stability constants (association constants) for the magnesium and manganese complexes of the substrates for the NADP+-specific isocitrate dehydrogenase (EC 1.1.1.42) from pea stems. At an ionic strength of 26.5 mM and at pH 7.4 the stability constants for the Mg2+–isocitrate and Mg2+–NADP+ complexes were 0.85 ± 0.2 and 0.43 ± 0.04 mM−1 respectively and for the Mn2+–isocitrate and Mn2+–NADP+ complexes they were 1.25 ± 0.07 and 0.75 ± 0.09 mM−1 respectively. At the same ionic strength but at pH 6.0 the Mg2+–NADPH and Mn2+–NADPH complexes had stability constants of 0.95 ± 0.23 and 1.79 ± 0.34 mM−1 respectively. Oxalosuccinate and α-ketoglutarate do not form measureable complexes under these conditions. Saturation kinetics of the enzyme with respect to isocitrate and metal ions are consistent with the metal–isocitrate complex being the substrate for the enzyme. NADP+ binds to the enzyme in the free form. Saturation kinetics of NADPH and Mn2+ indicate that the metal–NADPH complex is the substrate in the reverse reaction. In contrast the pig heart enzyme appears to bind free NADPH and Mn2+. A scheme for the reaction mechanism is presented and the difference between the reversibility of the NAD+ and NADP+ enzyme is discussed in relation to the stability of the NADH and NADPH metal complexes.

Europium tartronate and mandelate ion association in water

1967 ◽  
Vol 45 (14) ◽  
pp. 1643-1647 ◽  
Author(s):  
P. G. Manning
Keyword(s):  
Ionic Strength ◽  
Solvent Extraction ◽  
Stability Constant ◽  
Stability Constants ◽  
Ion Association ◽  
Tridentate Ligand ◽  
Radiotracer Method ◽  
The Stability ◽  
Two Stages ◽  
Low Ionic Strength

Stepwise stability constants have been determined for the 1:1 and 1:2 Eu3+:mandelate− and Eu3+:tartronate2− complexes in water. Measurements were made at low ionic strength and the temperature was 25 °C. The solvent-extraction–radiotracer method was used.For the mandelate system at an ionic strength of 0.104, K1 = 5.0 × 102, K2 = 1.58 × 102, and K1:K2 = 3.1. The K1:K2 ratios suggest monodentate ligandcy.The stepwise stability constants for the two stages of tartronate ion association are: K1 = 7.1 ( ± 15%) × 104 and K1K2 = 4.2 ( ± 5%) × 108. The magnitudes of the stability constants suggest that tartronate is a tridentate ligand. The stability constant ratios are discussed with reference to the ratios for piperidinedicarboxylate and iminodiacetate complexes.

scholarly journals Kinetics and Mechanism of Oxidation of Glutamic Acid byN-Bromophthalimide in Aqueous Acidic Medium

2011 ◽  
Vol 8 (4) ◽  
pp. 1472-1477
Author(s):  
N. M. I. Alhaji ◽  
S. Sofiya Lawrence Mary
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Glutamic Acid ◽  
Acidic Medium ◽  
Reaction Medium ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Mechanism Of Oxidation ◽  
Kinetics Of ◽  
Aqueous Acidic Medium

The kinetics of oxidation of glutamic acid (Glu) withN-bromophthalimide (NBP) was studied in perchloric acid medium at 30°C by potentiometric method. The reaction is first order each in NBP and glutamic acid and is negative fractional order in [H+]. Addition of KBr or the reaction product, phthalimide had no effect on the rate. Similarly variation of ionic strength of the medium did not affect the rate of the reaction. Also the rate increased with decrease in dielectric constant of the reaction medium. The thermodynamic parameters were computed from Arrhenius and Eyring plots. A suitable mechanism consistent with the kinetic results has been proposed.

Coordination Compounds of Indium. Part XV. The Stability Constants of some Trifluoromethyl-β-diketonate Complexes of Indium (III)

1972 ◽  
Vol 50 (16) ◽  
pp. 2622-2625 ◽  
Author(s):  
Keith Bowden ◽  
(Mrs.) G. M. Tanner ◽  
D. G. Tuck
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Coordination Compounds ◽  
Divalent Cations ◽  
Aqueous Acetone ◽  
Solvent Systems ◽  
The Stability

The stability constants K1 and K2 have been measured for the interaction of indium(III) with the ligands R•CO•CH2•CO•CF3 (R = 2-furyl, 2-thienyl, phenyl, 2-naphthyl, i-butyl, and (t-butyl). The pKa values for these compounds, and for R = 3-pyridyl and methyl, are also reported. A conventional potentiometric technique was used; the results refer to 46% aqueous acetone, at an ionic strength of approximately 0.1 M. The results are compared with published values for complexes of these ligands with divalent cations in other solvent systems.

Effects of ionic strength and pH on the stability constants of the complex of Co(II) with soil fulvic acid

1999 ◽  
Vol 241 (2) ◽  
pp. 351-353 ◽  
Author(s):  
W. M. Dong ◽  
W. J. Li ◽  
H. Q. Zhang ◽  
X. D. Wang ◽  
Z. J. You ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Fulvic Acid ◽  
Stability Constants ◽  
The Stability
Sign in / Sign up

Export Citation Format

Share Document