Stabilitätsuntersuchungen an Kupferkomplexen substituierter Acetessigsäure-2-amidopyridine und -pyrimidine II

The stability constants of the copper complexes of acetoacet-2-amidopyridine and-2-amidopyrimidine have been determined by potentiometric pH-measurements. The variation of stability constants with pyridyl and pyrimidyl substituents is interpreted.     

Relationen Zwischen Protonenassoziations-und Komplex-stabilitätskonstanten bei substituierten Anthranilsäuren

Relations between Proton Association and Complex Stability Constants of Substituted Anthranilic Acids A “model of similar coordination spheres” is developed. From this model a quantitative relation between the proton association constants and the complex stability constants of ligands of the types I and XIV (see text) may be derived. The influence of the substituents X and Y on the Protonation and on the complex formation is reduced to the inductive and mesomeric effect and to the field effect. The complex stability constants calculated with the help of the model are compared with the experimental results.     

Zur Bestimmung Thermodynamischer Komplexstabilitätskonstanten in Dioxan-Wasser-Mischung

On the determination of coordination stability constants in dioxane-water mixture. The potentiometric method of determining thermodynamic acid constants and coordination stability constants in dioxane—water mixture is critically examined and the necessary values for mean molal activity coefficients and pH meter correction are reascertained.     

Metallchelate von Thiohydroxamsäurederivaten

The chelate compounds of the VIII subgroup of N-thiobenzoyl-N-phenylhydroxylamine and benzothiohydroxamic acid were prepared. The magnetic properties and stability constants of some of these compounds are discussed.     

Über die relative Reaktivität von Nucleophilen. Vorläufige Mitteilung

For a number of nucleophiles L an approximate linear correlation between the logarithms of the stability constants of methylmercury-complexes of L and the nuclear spin-spin-coupling constants J of Ch₃HgL was found.     

Bestimmung der Stabilitätskonstanten gemischter Hexahalogenokomplexe von Osmium(IV)

Determination of the Stability Constants of Mixed Hexahalogeno Complexes of Osmium(IV) The individual and total stability constants of the complex series [OsX_xY_6?x]^2?; X ≠ Y = Cl, Br, I; x = 0–6 are determined by radiometric measurements of the equilibrium concentrations of all compounds. The thermodynamical stability increases from the hexabromo- over the hexachloro- to the hexaiodo-complex. The total stability constants are in ratio of 1:5,2:1225. With the individual constants the equilibrium diagrams are calculated. The photometric determination of the cis/trans ratio in complexes with x = 2, 3, 4 gives the statistical distribution of the ligands in the octahedrons. The relationship between thermodynamical and kinetical data is discussed.     

Chelate von β-Dicarbonylverbindungen und ihren Derivaten. XXIV. Stabilitätskonstanten von Metallchelaten unterschiedlich substituierter Pivaloylacylmethane

Chelates of β-dicarbonyl compounds and their derivatives. XXIV. Stability constants of metal chelates with differently substituted acylpivaloylmethanes Stoichiometric stability constants of copper(II), beryllium(II), nickel(II), cobalt(II) and zinc(II) chelates of 25 differently substituted acylpivaloylmethanes are determined in dioxane-water mixture and relations for calculating thermodynamic constants are given. The influence of aromatic and aliphatic substituents of the β-diketones on complex stability is discussed.     

Chelate von Chinolin-8-ol-Derivaten. VIII. Säure- und Komplexstabilitätskonstanten alkyl- bzw. alkenylsubstituierter Chinolin-8-ole

Chelates of 8-Quinolinol Derivatives. VIII. Acid and Complex Stability Constants of Alkyl and Alkenyl Substituted 8-Quinolinols For a series of 7-substituted alkyl and alkenyl 8-quinolinols as well as 2-, 5-, and 7-methyl-8-quinolinols the acid constants and the stability constants of the nickel and zinc chelates were determined potentiometrically in 75 vol-% dioxane-water mixture. Methyl groups, as expected, increase the basicity of both donor atoms of the 8-quinolinols, whereas alkyl substituents in 7-position cause a decrease in basicity of the quinoline N-atom. The influence of substituents on the complex stability is only small.     

Komplexone XLIV. Die Komplexe der Anionen der Triäthylentetraminhexa-Essigsäure mit Calcium(II), Kupfer(II) und Zink(II)

Using pH-methods - direct titration according to Schwarzenbach, and ligand-ligand exchange - the stability constants of the complexes of divalent calcium, copper and zinc ions with the anions of triethylenetetramine hexaacetic acid have been determined. The complications arising by the interpretation of the experimental measurements of pH-values below 3.5 are discussed. These factors are normally not taken into account, and often wrong values of the equilibrium constants have been communicated.     

Elektrophoretische Untersuchung der Komplexbildung von FeY− (H4Y = Ethylendiamintetraessigsäure) mit Aminopolycarbonsäuren

Electrophoretic Investigation of the Complexation of FeY^? (H₄Y = Ethylene Diamine Tetraacetic Acid) with Aminopolycarboxylic Acids In the system FeY/APC (iminodiacetic acid, nitrilotriacetic acid ethylenediaminetetraacetic acid, respectively) ternary complexes could be detected in aqueous solution. By means of electrophoretic measurements the ratio of the components in the species is FeY:APC = 1:1 without any exception. The stability constants K₁ = [FeYL]/[FeY][L] of the complexes are discussed.     

Zur Bestimmung der Komplexstabilität aus massenspektrometrischen Daten

On the Evaluation of Complex Stability from Mass Spectrometric Data Mass spectrometric data and potentiometric stability constants (75% v/v dioxane/water) of Ni(II) and Cu(II) 1:2 chelates of several N-Benzoyl(thio)benzamides and N-Benzoyl(thio, seleno)ureas are compared. It turns out, that the % total ion stream (% TIS) correlates fairly well in a logarithmical plot against the cumulative stability constant of the chelates.     

Complexation of Gd<Superscript>III</Superscript> with tetra-<Emphasis Type="Italic">p-tert</Emphasis>-butylthiacalix[4]arenoic acid in micellar media

The conditions for the formation of gadolinium(III) complexes possessing high relaxivity with various tetraacid stereoisomers based on p-tert-butylthiacalix[4]arene in micellar solutions of nonionic surfactants were established. The acid-base properties of individual isomers of the ligand were studied by pH-metric titration and UV spectroscopy. The composition and stability constants of the solubilized gadolinium(III) complexes with the obtained thiacalixarenes were determined using computer simulation of the NMR relaxation data.     

Elektrophoretische Untersuchung der Aminosäurekomplexe mit markiertem Zink, (65Zn)

Electrophoretic Investigation of Amino Acid Complexes with Labelled Zinc, (⁶⁵Zn) The formation of zinc complexes with sulphur amino acids and other, no sulphur containing amino acids, has been studied. The constants of stability determined from the electrophoretical mobilities were compared with those from literature. An influence of the sulphur atom in amino acids complexibility has been deduced.     

Über Eisen(III)-Komplexe mit Phenolen. V. Komplexbildung mit 4,5-Dibrombrenzcatechin-disulfonsäure(3,6)

The chelate formation between Fe³⁺ and 4.5-dibromopyrocatechol-3.6-disulfonic acid in aqueous solution has been investigated spectrophotometrically. The stability constants and the light absorption properties of the chelates are communicated. Compared with the bromine-free tiron, the ? values increase and the λ_max positions are shifted bathochromically on halogenation. However, due to the changed position of the sulfo groups, the bond-weakening effect of the halogen substituents is covered, leading to a distinct increase of pK_S1, but to only slight alterations of all the other constants. Poor solubility and accessability of the chelating reagent hinder its application in analysis.     

Complexation thermodynamics between butyl rhodamine B and calix[n]arenesulfonates (n = 4, 6, 8)

The characteristics of host–guest complexation between water-soluble calix[n]arenesulfonates (CnS, n = 4, 6, 8) and butyl rhodamine B (BRB) were investigated by fluorescence spectrometry. Fluorescence spectroscopy experiments were performed in pH 8.0 Tris(3-aminomethane)–HCl buffer solution at different temperature to calculate the stability constants (K_S) for the stoichiometric 1:1 inclusion complexes of C4S, C6S, and C8S with BRB. The complex stability constant monotonically increased with the number of phenolic units in the calixarene ring. The thermodynamic parameters at T = 298 K for the inclusion complexes were calculated through Van’t Hoff analysis. The inclusion complexes of CnS with BRB were driven by the favorable enthalpic changes, accompanying negative entropy changes. The stability constants were affected by the acidity of the solution. When pH was 8.0, the stability constants reached the maximum. The complex interaction was mainly attributed to the weak forces including electrostatic interaction and hydrogen bonding.     

Zinc Complexes of Cyclodextrin‐bearing 8‐Hydroxyquinoline Ligands: A Comparative Study

The mounting evidence supporting the role of metal ions in several diseases has turned metal‐ion chelation therapy into a promising treatment strategy. The design of efficient metal‐binding ligands requires in‐depth knowledge of molecular structure and stability constants of the complexes formed. This paper presents an extensive overview on the stability of zinc(II) and copper(II) complexes of a series of cyclodextrin‐8‐hydroxyquinoline conjugates. In order to explain the differences observed in the stability constants between the metal complexes of the 6‐functionalized and 3‐functionalized cyclodextrin isomers, conformational analysis and DFT simulations were also performed. Molecular simulations allowed us to clarify the binding mode and to explain the differences in the stability constants of the metal complexes of these derivatives.     

Metall-Komplexbildung von β-Hydroxythiophenderivaten III

The acidity constants of 2-acetyl-3-hydroxy-thiophene (III) and 3-acetyl-4-hydroxy-thiophene (IV) and the stability constants of their complexes with some bivalent metal ions have been determined. The stability of the chelates is discussed as a function of the respective bond orders of the α–β and β–β′ bonds of the thiophene ring.     

乙腈溶液中对叔丁基杯[4]芳烃与一些脂肪胺间的相互作用

用紫外可见光谱法和电导法研究了乙腈溶液中一些脂肪胺与对叔丁基杯[4]芳烃间的相互作用。考察了它们之间的反应机理,测定了它们之间各步反应的平衡常数及表观复合常数等。由紫外可见光谱得到的表观复合常数和同一方法得到的文献值数量级相同但数值相差几倍。电导测定表明在乙腈溶液中脂肪胺与对叔丁基杯[4]芳烃间的反应分两步进行:首先胺从杯芳烃得到一个质子生成胺正离子和杯负离子,然后离子再进一步包合。其总复合常数远小于其表观复合常数。且在对叔丁基杯[4]芳烃的饱和溶解度以下,质子转移所生成的离子是反应的主要产物。结果与文献中结论相反。     

Kupferkomplexe von Bisamiden: Struktur und Stabilität I

Complex formation between Cu²⁺ and several ligands, each containing two amino and two amide groups, has been studied potentiometrically and spectrophotometrically. A digital computer was used to determine the composition of the complex species formed and to calculate their stability constants. N,N′-diglycyl-1, 2-diaminoethane and its homologues form 5-, 6-, 7-, 8- and 9-membered rings between the two amide groups, respectively. No tendency towards formation of binuclear species has been observed.     

Spectrophotometric Determination of the Stability Constant of the Inclusion Complexes of Some Catechol Derivatives with β‐Cyclodextrin Based on Their Reaction with Iodate

The effects of β‐cyclodextrin (β‐CD) inclusion on the kinetics of the oxidation of several cathechol derivatives, including 4‐tert‐butylcatechol, 3‐methylcatechol and 3‐methoxycatechol, with iodate was studied spectrophotometrically. The rate of the oxidation reactions decreased by increasing β‐CD concentration as a result of inclusion. The stability constants for the inclusion complexes of the investigated compounds were determined based on the changes in the rate constants as a function of β‐CD concentration at pH 3.0. The rate constants for the free and complexed forms and also the stability constants for the inclusion complexes were calculated. The role of the hydrophobic effect was evaluated by studying the influence of the presence of different amounts of ethanol on the β‐CD: guest interaction. In a given H₂O‐EtOH mixture the stability of β‐CD complexes shows the order of 4‐tert‐butylcatechol ≈ 3‐methylcatechol ≈ 3‐methoxycatechol. Increasing ethanol content caused a decrease in the stability constant of the inclusion complexes and an increase in observed rate constants.