Electrochemical Studies of the Stability of Copper β-Diketone Chelates

1998 ◽  
Vol 63 (12) ◽  
pp. 1963-1968 ◽  
Author(s):  
Wulfhard Mickler ◽  
Anke Mönner ◽  
Erhard Uhlemann
Keyword(s):  
Experimental Data ◽  
Stability Constants ◽  
Relative Stability ◽  
Complex Stability ◽  
Electrochemical Studies ◽  
Overall Stability ◽  
Potentiometric Measurements ◽  
The Stability

The voltammetric reduction of copper β-diketone chelates was used to get information on their complex stability. 1,1,1-Trifluoropentane-2,4-dione, pentane-2,4-dione, 1-phenylbutane-1,3-dione, 1,3-diphenylpropane-1,3-dione and 2,2,6,6-tetramethylheptane-3,5-dione were chosen as model ligands. The complexes were reduced in two separate steps the first of which proved to be reversible. The experimental data are suitable for calculation of the relative stability constants of corresponding Cu(I) and Cu(II) complexes. The data well correlate with the overall stability constants determined potentiometrically. The results were applied to some new hydrophobic β-diketones which are not accessible to potentiometric measurements.

scholarly journals Study of Metal-1,10-Phenanthroline Complex Equilibria by Potentiometric Measurements

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Naciye Türkel
Keyword(s):  
Stability Constants ◽  
Metal Cations ◽  
Potentiometric Method ◽  
Ionic Radii ◽  
Binary Complexes ◽  
Potentiometric Measurements ◽  
Software Program ◽  
Phenanthroline Complex ◽  
The Stability ◽  
Potentiometric Data

The interaction of Sc(III), Y(III), and La(III) ions with 1,10-phenanthroline (Phen) has been investigated, using the potentiometric method at 25   and  M KNO3. Collected potentiometric data were processed by the “BEST” software program to establish the complexation model for each system. SPE software program was used to evaluate the concentration distributions of the species formed in solution. The stability constants for the binary complexes increased as the ionic radii of the metal cations decreased.

scholarly journals Interaction of Ampicillin and Amoxicillin with Mn2+: A Speciation Study in Aqueous Solution

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3110
Author(s):  
Claudia Foti ◽  
Ottavia Giuffrè
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Formation Constants ◽  
Enthalpy Change ◽  
Ligand Concentration ◽  
Empirical Parameter ◽  
Speciation Study ◽  
Potentiometric Measurements ◽  
The Stability

A potentiometric and UV spectrophotometric investigation on Mn2+-ampicillin and Mn2+-amoxicillin systems in NaCl aqueous solution is reported. The potentiometric measurements were carried out under different conditions of temperature (15 ≤ t/°C ≤ 37). The obtained speciation pattern includes two species for both the investigated systems. More in detail, for system containing ampicillin MLH and ML species, for that containing amoxicillin, MLH2 and MLH ones. The spectrophotometric findings have fully confirmed the results obtained by potentiometry for both the systems, in terms of speciation models as well as the stability constants of the formed species. Enthalpy change values were calculated via the dependence of formation constants of the species on temperature. The sequestering ability of ampicillin and amoxicillin towards Mn2+ was also evaluated under different conditions of pH and temperature via pL0.5 empirical parameter (i.e., cologarithm of the ligand concentration required to sequester 50% of the metal ion present in traces).

scholarly journals Thermodynamic and Spectroscopic Studies of the Complexes Formed in Tartaric Acid and Lanthanide(III) Ions Binary Systems

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1121 ◽  
Author(s):  
Michal Zabiszak ◽  
Martyna Nowak ◽  
Zbigniew Hnatejko ◽  
Jakub Grajewski ◽  
Kazuma Ogawa ◽  
...  
Keyword(s):  
Tartaric Acid ◽  
Stability Constants ◽  
Binary Systems ◽  
Equilibrium Constants ◽  
Spectroscopic Studies ◽  
Luminescence Spectroscopy ◽  
Binary Complexes ◽  
Overall Stability ◽  
The Stability

Binary complexes of tartaric acid with lanthanide(III) ions were investigated. The studies have been performed in aqueous solution using the potentiometric method with computer analysis of the data for detection of the complexes set, determination of the stability constants of these compounds. The mode of the coordination of complexes found was determined using spectroscopy, which shows: Infrared, circular dichroism, ultraviolet, visible as well as luminescence spectroscopy. The overall stability constants of the complexes as well as the equilibrium constants of the reaction were determined. Analysis of the equilibrium constants of the reactions and spectroscopic data allowed the effectiveness of the carboxyl groups in the process of complex formation.

Fletcher–Powell minimization of analytical potentiometric data by microcomputer: application to the Cu(II) complexes of biological polyamines

1985 ◽  
Vol 63 (11) ◽  
pp. 3122-3128 ◽  
Author(s):  
Douglas M. Templeton ◽  
Bibudhendra Sarkar
Keyword(s):  
Biological Activity ◽  
Metal Complex ◽  
Stability Constants ◽  
Speciation Analysis ◽  
Complex Stability ◽  
Minimization Algorithm ◽  
The Stability ◽  
Best Fit ◽  
Complex Stability Constants ◽  
Potentiometric Data

The Fletcher–Powell minimization algorithm has been successfully implemented for the extraction of metal complex stability constants from analytical potentiometric data. The procedure has been adapted to run on a microcomputer with acceptable execution times, and several strategies are employed to speed convergence and avoid false minima. This allows economical minimization for a large number of models of speciation, and improves the reliability of the proposed best fit by encouraging the checking of more models than previously possible. The Ni(II)–glycine system has been analyzed and excellent agreement with the stability constants of an earlier multi-laboratory study has been attained. The system proves useful in the evaluation of both analytical and computational methods. The procedure has also been used for speciation analysis of the Cu(II) complexes of the growth regulating polyamines, spermine, and spermidine. Both systems form fully deprotonated complexes at physiological pH, which are relevant to their biological activity.

103Rh-NMR-Untersuchungen an Chloro-Bromo-Rhodaten(III) und Bestimmung der Stabilitätskonstanten im System [RhClnBr6-n]3-, n = 0-6 / 103Rh NMR Studies of Chloro-Bromo-Rhodates(III) and Determination of the Stability Constants in the System [RhCl„Br6-n]3-, n = 0-6

1989 ◽  
Vol 44 (11) ◽  
pp. 1402-1406 ◽  
Author(s):  
W. Kuhr ◽  
G. Peters ◽  
W. Preetz
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Stability Constant ◽  
Stability Constants ◽  
Trans Isomers ◽  
Nmr Studies ◽  
Downfield Shift ◽  
Overall Stability ◽  
The Stability

By 103Rh NMR spectroscopy the ten compounds of the system [RhCl„Br6_„]3-, n = 0-6 are identified by separate signals. A downfield shift of approximately 160 ppm is observed per substitution of Cl by Br, and the stereoisomers for n = 2, 3, 4 are separated by at least 4 ppm. From the relative intensities of the 103Rh signals in equilibrated solutions, whose total contents of Rh. Cl and Br are known, six individual stability constants are calculated. Their product gives the overall stability constant, indicating [RhBr6]3- to be 36,300 times more stable than [RhCl6]3-. On treatment of [RhBr6]3- with HCl cis/fac isomers are formed stereospecifically, whereas the reaction of [RhCl6]3- with HBr gives trans isomers, n = 2 and 4, containing 20—30% of the cis compounds; only mer-[RhCl3Br3] 3- is obtained pure. The high resolution spectra of [RhCl6]3- and [RhBr6]3- are exhibit five signals each, reflecting the intensity patterns of the most abundant isotopomers within [Rh35Cln37Cl6-n]3-, n = 2-6, and [Rh79Br„81Br6_„]3-, n = 1-5, respectively.

Studies on the solvent extraction of metal dithiocarbamates

1969 ◽  
Vol 47 (12) ◽  
pp. 2320-2323 ◽  
Author(s):  
Vedula S. Sastri ◽  
Keijo I. Aspila ◽  
Chuni L. Chakrabarti
Keyword(s):  
Solvent Extraction ◽  
Stability Constants ◽  
Divalent Metal ◽  
Divalent Metal Ions ◽  
Extraction Constants ◽  
Overall Stability ◽  
Stability Constants Of Complexes ◽  
Dithiocarbamic Acid ◽  
The Stability ◽  
Metal Dithiocarbamates

Studies on the solvent extraction of morpholine dithiocarbamic acid complexes of divalent metal ions Mn, Fe, Co, Ni, Cu, Zn, Pb, Cd, Hg, and Sn were carried out, and the extraction constants and the overall stability constants were determined. The stability constants of complexes of Cu(II) formed with various substituted dithiocarbamic acids, showed a variation of the stability constants with the basicity of the nitrogen and sulfur atoms in the reagents.

The Relative Stability of Internal Metal Complexes. I. Complexes of 8-Hydroxyquinoline, Salicylaldehyde, and Acetylacetone

1949 ◽  
Vol 2 (1) ◽  
pp. 92
Author(s):  
LE Maley ◽  
DP Mellor
Keyword(s):  
Analytical Chemistry ◽  
Metal Complexes ◽  
Stability Constants ◽  
Relative Stability ◽  
Solvent Mixture ◽  
The Other ◽  
Electrometric Method ◽  
Other Substances ◽  
The Stability ◽  
Quantitative Treatment

The stability constants of a series of internal metal complexes derived from 8-hydroxyquinoline, salicylaldehyde, and acetylacetone have been determined by means of an electrometric method. A quantitative treatment of the chelation of 8-hydroxyquinoline, based on the theory of step equilibria, is given and the modifications required for dealing with the other substances investigated are indicated. Two important facts emerge from this survey : (1) The order of the metals (as regards stability of their complexes) is substantially the same for each of the three chelating substances studied. (2) The order of the stability of the complexes derived from the three chelating substances is independent of the nature of the coordinating metal, the 8-hydroxyquinoline complex of a metal being more stable than its acetylacetone complex which in turn is more stable than its salicylaldehyde complex. Measurements were made of the stability constants in water-dioxan mixtures and the effect of changing the proportions of the two components in the solvent mixture was studied in several instances. The values of stability constants of internal metal complexes in water-dioxan mixtures are greater than those in water. It is shown that insolubility of internal metal complexes is not, in general, a criterion of their relative stability. The possible significance of stability-constants in chemotherapy, biochemistry, and analytical chemistry is briefly discussed.

scholarly journals Graphical and computational methods for determining the stability constants of mono- and polynuclear complexes with a common intersection point of the family of formation curves

2020 ◽  
Vol 2 (2) ◽  
pp. 70-77
Author(s):  
Igor Povar ◽  
◽  
Oxana Spinu ◽  
Boris Pintilie
Keyword(s):  
Experimental Data ◽  
Stability Constants ◽  
Critical Evaluation ◽  
Intersection Point ◽  
Computational Method ◽  
Tabular Data ◽  
The Family ◽  
Common Intersection ◽  
The Stability ◽  
Common Intersection Point

Aqueous polynuclear systems have been analyzed, for which the family of formation curves intersects at a common point. The analyzed graphical and computational method for determining the stability constants can be used as initial values within the iterative calculation process. In some cases, the stability constants are calculated using only the coordinates of the common intersection point. The obtained equations could be of special interest when the experimental data can be interpreted in several models. In these cases, given the large volume of experimental data, the calculation is simple and the model can certainly be chosen with high safety. The obtained equations may also be applied for critical evaluation of tabular data if the coordinates of the intersection point are known. A series of real polynuclear systems have been analyzed and useful conclusions have been made.

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