Stability constants of three iron(III) salicylates

1970 ◽  
Vol 48 (16) ◽  
pp. 2574-2586 ◽  
Author(s):  
W. A. E. McBryde ◽  
Janet L. Rohr ◽  
J. S. Penciner ◽  
J. A. Page
Keyword(s):  
Stability Constants ◽  
Equilibrium Constants ◽  
Background Electrolyte ◽  
Aminosalicylic Acid ◽  
Sulfosalicylic Acid ◽  
Spectrophotometric Measurement ◽  
Acidity Constants ◽  
Extinction Coefficients ◽  
The Stability ◽  
Improved Methods

Stability constants of the iron(III) complexes of salicylic acid, sulfosalicylic acid, and 4-aminosalicylic acid, together with several of the acidity constants of these, have been determined at 25 °C and in solutions with 0.5 M background electrolyte. For the spectrophotometric measurement of the stability constants improved methods for determining the extinction coefficients of the first and second complexes are described. Protonated species appear only with the aminosalicylate complexes, and the site of this protonation is discussed. Previous values of these equilibrium constants have been collected and critically assessed.

A SPECTROPHOTOMETRIC REEXAMINATION OF THE SPECTRA AND STABILITIES OF THE IRON (III) – TIRON COMPLEXES

1964 ◽  
Vol 42 (8) ◽  
pp. 1917-1927 ◽  
Author(s):  
W. A. E. McBryde
Keyword(s):  
Aqueous Solutions ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Sodium Perchlorate ◽  
Potassium Nitrate ◽  
Low Ph ◽  
Exact Nature ◽  
Simple Complex ◽  
Acidity Constants ◽  
The Stability

Variations in the spectra of the aqueous solutions of the iron (III) – sodium catechol disulphonate (Tiron) complexes may be interpreted in relation to pH of the solutions to show which complexes are present at any chosen pH. With this knowledge it is possible in this system to evaluate equilibrium constants for the formation of each complex in turn. Combining these with separately determined acidity constants for Tiron, the stability constants of the complexes may be calculated. These have been determined for background solutions of potassium nitrate or sodium perchlorate each at three different concentrations, and for three different ratios of reagent to metal. Averages of a number of determinations made under these conditions are given in Table III of the paper. The constant K1 in perchlorate media shows an unmistakable dependence suggestive of the existence of a protonated species at low pH as well as the simple complex ML. However, there is some ambiguity in the interpretation of the results so that the exact nature of the protonated complex cannot be decided.

Constraints on the determination of stability constants for metal complexes. II. The iron(III) phenolates

1968 ◽  
Vol 46 (14) ◽  
pp. 2385-2392 ◽  
Author(s):  
W. A. E. McBryde
Keyword(s):  
Metal Complexes ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Low Ph ◽  
Experimental Results ◽  
Good Precision ◽  
Acidity Constants ◽  
Extinction Coefficients ◽  
Molar Extinction Coefficients

Stability constants have been measured spectrophotometrically for the 1:1 complexes of iron(III) with phenol and five derivatives in background solutions having two different compositions, 0.027 M NaClO4 and 0 5 M KNO3 Conditional acidity constants for these phenols in the second of these media were also determined The experimental results were treated in two different ways to obtain values of the equilibrium constants and the molar extinction coefficients of the complexes It is apparent that the equilibrium in these cases must be studied under conditions, such as low pH and low concentration of iron, which militate against good precision in the results

Extraction of strontium and barium salts by the nitrobenzene solution of dicarbolide in the presence of glymes

1985 ◽  
Vol 50 (3) ◽  
pp. 581-599 ◽  
Author(s):  
Petr Vaňura ◽  
Emanuel Makrlík
Keyword(s):  
Stability Constants ◽  
Organic Phase ◽  
Equilibrium Constants ◽  
Minor Role ◽  
Nitrobenzene Solution ◽  
Ligand Structure ◽  
Stability Constants Of Complexes ◽  
Separation Factors ◽  
The Stability ◽  
A Minor

Extraction of microamounts of Sr2+ and Ba2+ (henceforth M2+) from the aqueous solutions of perchloric acid (0.0125-1.02 mol/l) by means of the nitrobenzene solutions of dicarbolide (0.004-0.05 mol/l of H+{Co(C2B9H11)2}-) was studied in the presence of monoglyme (only Ba2+), diglyme, triglyme, and tetraglyme (CH3O-(CH2-CH2O)nCH3, where n = 1, 2, 3, 4). The distribution of glyme betweeen the aqueous and organic phases, the extraction of the protonized glyme molecule HL+ together with the extraction of M2+ ion and of the glyme complex with the M2+ ion, i.e., ML2+ (where L is the molecule of glyme), were found to be the dominating reactions in the systems under study. In the systems with tri- and tetraglymes the extraction of H+ and M2+ ions solvated with two glyme molecules, i.e., the formation of HL2+ and ML22+ species, can probably play a minor role. The values of the respective equilibrium constants, of the stability constants of complexes formed in the organic phase, and the theoretical separation factors αBa/Sr were determined. The effect of the ligand structure on the values of extraction and stability constants in the organic phase is discussed.

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.

scholarly journals Studies on biologically important copper(II) / manganese(II) / uranyl(II) – norvaline binary complexes

2008 ◽  
Vol 27 (2) ◽  
pp. 157 ◽  
Author(s):  
Brij Bhushan Tewari
Keyword(s):  
Stability Constants ◽  
Coordination Compounds ◽  
Metal Ion ◽  
Background Electrolyte ◽  
Binary Complex ◽  
Paper Strip ◽  
Ph Values ◽  
Binary Complexes ◽  
Stability Constants Of Complexes ◽  
The Stability

In coordination compounds studies, a knowledge of the magnitude of the stability constants of complexes is necessary for preliminary quantitative treatment. Described herein is a method that involves the use of advanced ionophoretic technique for the study of the equilibria in binary complex systems in solution. This method is based upon the migration of a spot of the metal ion on a paper strip at different pH values of background electrolyte containing 0.1 M perchloric acid and 0.01 M norvaline. A graph of pH against mobility provides information about the nature of the complexation and helps in calculating stability constants. Using this method, the stability constants of binary complexes metal(II) – norvaline have been determined to be (8.11 ± 0.02, 7.03 ± 0.09); (3.77 ± 0.11, 2.39 ± 0.07) and (7.59 ± 0.05, 6.17 ± 0.04) (log K values) for Cu(II), Mn(II) and UO2(II) complexes, respectively, at 35 ºC.

Paper ionophoretic technique in the study of biologically important beryllium(II) / cobalt(II)-homoserine binary complexes in solution

2010 ◽  
Vol 29 (2) ◽  
pp. 139
Author(s):  
Brij Bhushan Tewari
Keyword(s):  
Complex System ◽  
Stability Constants ◽  
Present Method ◽  
Background Electrolyte ◽  
Binary Complex ◽  
Paper Strip ◽  
Successive Addition ◽  
Binary Complexes ◽  
Quantitative Indication ◽  
The Stability

Quantitative indication of the process of forming a complex comes from the evaluation of the stability constants, which characterize the equilibria corresponding to the successive addition of ligands. A method, involving the use of paper electrophoretic technique is described for the study of binary complex system in solution. Present method is based upon the migration of a spot of metal ions on a paper strip at different pH’s of background electrolyte. A graph of pH against mobility gives information about the binary complexes and permits calculation of their stability constants. The first and second stability constants of [Be(II)-homoserine] and [Co(II)-homoserine] complexes were found to be (7.13 ± 0.02; 6.11 ± 0.09) and (4.27 ± 0.07; 3.47 ± 0.11) (logarithm stability constant values) for Be(II) and Co(II) complexes, respectively, at ionic strength of 0.1 mol/L and a temperature of 35 °C.

Solution properties of metal ion complexes formed with the antiviral and cytostatic nucleotide analogue 9-[2-(phosphonomethoxy)ethyl]-2-amino-6-dimethylaminopurine (PME2A6DMAP)

2014 ◽  
Vol 92 (8) ◽  
pp. 771-780 ◽  
Author(s):  
Raquel B. Gómez-Coca ◽  
Astrid Sigel ◽  
Bert P. Operschall ◽  
Antonín Holý ◽  
Helmut Sigel
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Present System ◽  
Therapeutic Effects ◽  
Solution Properties ◽  
Acidity Constants ◽  
Nucleotide Analogue ◽  
Ether Oxygen ◽  
The Stability

The acidity constants of protonated 9-[2-(phosphonomethoxy)ethyl]-2-amino-6-dimethylaminopurine (H3(PME2A6DMAP)+) are considered, and the stability constants of the M(H;PME2A6DMAP)+ and M(PME2A6DMAP) complexes (M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+) were measured by potentiometric pH titrations in aqueous solution (25 °C; I = 0.1 mol/L, NaNO3). In the M(H;PME2A6DMAP)+ species, H+ and M2+ (mainly outersphere) are at the phosphonate group; this is relevant for phosphoryl-diester bridges in nucleic acids because, in the present system, there is no indication for a M2+–purine binding. This contrasts, for example, with the complexes formed by 9-[2-(phosphonomethoxy)ethyl]adenine, M(H;PMEA)+, where M2+ is mainly situated at the adenine residue. Application of log [Formula: see text] vs. [Formula: see text] plots for simple phosph(on)ate ligands, R–PO32− (R being a residue that does not affect M2+ binding), proves that all M(PME2A6DMAP) complexes have larger stabilities than what would be expected for a M2+–phosphonate coordination. Comparisons with M(PME–R) complexes, where R is a noncoordinating residue of the (phosphonomethoxy)ethane chain, allow one to conclude that the increased stability is due to the formation of five-membered chelates involving the ether–oxygen of the –CH2–O–CH2–PO32− residue: the percentages of formation of these M(PME2A6DMAP)cl/O chelates, which occur in intramolecular equilibria, vary between 20% (Sr2+, Ba2+) and 50% (Zn2+, Cd2+), up to a maximum of 67% (Cu2+). Any M2+ interaction with N3 or N7 of the purine moiety, as in the parent M(PMEA) complexes, is suppressed by the (C2)NH2 and (C6)N(CH3)2 substituents. This observation, together with the previously determined stacking properties, offers an explanation why PME2A6DMAP2– has remarkable therapeutic effects.

Equilibrium Constants for 2,3-Dihydroxypyridine and its Complex with Iron(III) in 1 M Hydrochloric Acid

1972 ◽  
Vol 50 (11) ◽  
pp. 1649-1654 ◽  
Author(s):  
K. E. Curtis ◽  
G. F. Atkinson
Keyword(s):  
Hydrochloric Acid ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Acidity Constants ◽  
Overall Stability

Improved values for two acidity constants of 2,3-dihydroxypyridine have been computed using program PITMAP. The composition of the complex with iron(III) and its conditional and overall stability constants in 1 M hydrochloric acid have been evaluated.

Complexes du germanium(IV) et du bore(III) avec des o-diphénols substitués

1969 ◽  
Vol 47 (14) ◽  
pp. 2569-2571 ◽  
Author(s):  
R. Meilleur ◽  
R. L. Benoit
Keyword(s):  
Complex Formation ◽  
Stability Constants ◽  
Acidity Constants ◽  
Spectrophotometric Methods ◽  
The Stability

Complex formation between germanium(IV) and boron(III) and some substituted o-diphenols H2L has been studied by potentiometric and spectrophotometric methods. Correlations are established between the stability constants of GeL32− and BL(OH)2− complexes and the acidity constants of the diphenols.

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