Determination of dissociation constants for some pyrogallol azo derivatives and stability constants of their complexes with rare-earth metals

The dissociation constants of some haloazo derivatives of pyrogallol and the stability constants of their complexes with rare-earth metals (La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) are determined by potentiometric titration in aqueous ethanol (3: 7). A correlation between the dissociation constants of the reagents and the stability constants of their complexes is found.     

Metal chelates of phosphonate-containing ligands-IV (Stability of some 1,6-hexamethylenediamine-N,N,N',N'-tetra(methylenephosphonic) acid metal chelates)

The stability constants of the complexes formed between the anion of 1,6-hexamethylenediamine-N,N,N',N'-tetra(methylenephosphonic) acid and some transition and non-transition metal ions have been measured potentiometrically at a temperature of 25 degrees and an ionic strength of 0.1M (KNO(3)). The acid dissociation constants of the ligand and stability constants of the protonated complexes are also reported. Comparisons are made with the acid dissociation constants of the analogous compounds EDTA, ENTMP and HDTA, and possible structural formulae are given.     

HPLC法测定某些高铼酸盐易变配位化合物的稳定常数

根据用柠檬酸盐作流动相时,ReO_4~-在PRP-S柱上保留时间出现异常现象,本文提出用HPLC法测定高铼酸根与柠檬酸、酒石酸和草酸形成的易变配位化合物的稳定常数,在水溶液中分别为123、35.6和45.1。     

柱上衍生反相色谱法测定金属配合物的稳定常数

提出一种计算金属配合物稳定常数的新方法。应用住上衍生反相高效液相色谱法,以二乙基二硫代氨基甲酸钠为配体,测定金属配合物的保留时间,用以推导金属配合物的稳定常数。     

The stability of some lanthanide complexes with methylethyl glycolate and with methylpropyl glycolate

The 4 successive stability constants have been determined for the methyIethyl glycolate and methylpropyl glycolate complexes of some lanthanide elements by potentiometric titration For all the metal ions, except lanthanum, the average ligand number exceeds a value of 3 indicating the formation of uninegative tetra-ligand complexes, ML₄^-, The stability constants are close to the values of the corresponding α-hydroxyisobutyrate complex systems     

镧(Ⅲ)-氨基酸配合物的温度滴定量热法研究

稀土配合物因其特有的性质而日益受到人们的重视 [1] .对于稀土与氨基酸配合物的已有研究 [2 ,3] ,但尚未见到关于镧 ( )与不同种氨基酸配合反应的较系统的报道 .文献 [2 ,3]大多采用 p H电位法或其它非热化学方法 ,且大多只得到反应的平衡常数 ,而用滴定量热法直接测定其配合常数和反应焓变的研究尚未见报道 .用滴定热量法可同时测定配合反应的焓变和熵变 [4 ] ,而且在滴定量热过程中 ,反应体系基本上是一封闭体系 ,除了对体系的温度进行监测外 ,对反应体系没有其它任何干扰 ,因而可以减少外界因素的影响 ,从而减少测定的误差 .本文用滴…     

Formation of mercury(ii) ethylenediaminediacetate and its mixed-ligand complexes with anions

The complexes of mercury(II) with EDDA and the formation of mixedligand complexes with some anions have been investigated spectrophotometrically. Mercury(II) reacts with EDDA to give 1:1 and 1:2 complexes, which have stability constants of 15.4±0.1 and 24.2±0.2 respectively, at ionic strength 0.1. These complexes react with anions (X), such as cyanide, thiocyanate, iodide, bromide and chloride, to form the mixed-ligand 1:1:1 complexes. Hg(EDDA)X. The apparent stability constants (log K_x) of the chloro, bromo, and thiocyanato mixed-ligand complexes are 9.9, 12.0, and 10.8, respectively.     

Determination of UO2(II), Th(IV) and Ce(III) Complexes Formed with Halogen and Nitro Derivatives of 8-Hydroxyquinoline

Proton-ligand stability constants for some iodo and nitro derivatives of 8-hydroxyquinoline were determined by Calvin Bjerrum potantiometric method. The stability constants of the corresponding chelates with UO₂ (II), Th(IV) and Co(III) were studied potentiometrically at 25 °C by applying Irving-Rossotti computing method. The complexes of the nitro-substituted ligands were less stable than the corresponding complexes of the unsubstituted ligands. The stability constants of metal-ligands depend on the ionic radii and ionic charge of metals and also they decrease with steric repulsions of the nitro groups.     

Synthesis,spectroscopy and thermal analysis of copper(II) hydrazone complexes

The chelating behavior of some hydrazones towards Cu(II) has been investigated. The isolated complexes were characterized by elemental analysis, magnetic moment, spectra (electronic, IR and ms) and thermal measurements. The IR spectra showed that the ligands are deprotonated in the complexes as bidentate, tridentate and binegative tridentate. Protonation constants of the ligands and the stability constants of their Cu(II) complexes were calculated. Square-planar, square-pyramidal, tetrahedral and/or distorted octahedral structures are proposed. The TGA data help to confirm the chemical formula of the complexes and indicated the steps of their thermal degradations.     

Copper(II) complexes of bis(amino amide) ligands: effect of changes in the amino acid residue

A family of ligands derived from bis(amino amides) containing aliphatic spacers has been prepared, and their protonation and stability constants for the formation of Cu(2+) complexes have been determined potentiometrically. Important differences are associated to both the length of the aliphatic spacer and the nature of the side chains derived from the amino acid. In general, ligands containing aliphatic side chains display higher basicities as well as stability constants with Cu(2+). In the same way, basicities and stability constants tend to increase when decreasing the steric hindrance caused by the corresponding side-chain. FT-IR, UV-vis and ESI-MS were used for analyzing the complex species detected in the speciation diagram. UV-vis studies showed the presence of different coordination environments for the copper(II) complexes. Complexes with different stoichiometries can be formed in some instances. This was clearly highlighted with the help of ESI-MS experiments.     

Determination of stability constants of some bivalent metal complexes with thiovioluric and diphenylthiovioluric acids

Stability constants of complexes of some bivalent metal ions, viz, Cu(II), Ni(II), Zn(II), Pb(II) and Mg(II) with thiovioluric and diphenylthiovioluric acid have been determined potentiometrically in 50 and 75% dioxan media, respectively. The order of stability constants for the complexes investigated has been found to be: Mn < Ni < Cu > Zn. The stability of lead complexes has been found to be intermediate between Mn(II) and Ni(II) while magnesium forms the least stable complexes.     

Protolitic complexing properties of acylhydrazones of substituted salicylaldehydes and stability constants of their cooper(II) complexes

The acid-base properties of acetyl-and heptoylhydrazones of substituted salicylaldehyde derivatives and the stability of their copper(II) complexes have been studied. For both sets of compounds, the ionization constants of the hydrazones and the stability constants of hydrazone complexes are linear functions of the substituent constants σ. An analogous tendency is found for the antiferromagnetic exchange interaction parameters in dimeric copper(II) nitrate complexes of heptoylhydrazones of substituted salicylaldehyde derivatives. A correlation between the protolytic properties of hydrazones and the magnetic properties of their complexes is suggested.     

Spectrophotometric characteristics of dissociation of Zr and Hf complexes with Methylthymol Blue

Two modifications of the spectrophotometric method for determination of the stability constants of ML and ML(2) complexes are derived and used for determination of the stability constants of Zr and Hf complexes with Methylthymol Blue. The dependence of the degree of dissociation of the complexes on the Zr and Hf concentrations is discussed.     

Stability constants of complexes formed by some metal ions with 2-(phenyliminomethyl)pyridine and 2-(o-hydroxyphenyliminomethyl)pyridine

The stability constants of some metal complexes of these two reagents have been determined.     

Kinetic study of the hydroxide ion attack on and DNA interaction with high spin iron(II) Schiff base amino acid chelates baering ONO donors

Kinetic study of some novel high spin Fe(II) complexes of Schiff base ligands derived from 5-bromsalicyaldehyde and amino acids with the OH^? ion and DNA has been carried out. Based on the kinetic data, the rate law and a plausible mechanism were proposed. Kinetic data of the base catalyzed hydrolysis imply pseudo first-order double stage process due to the presence of mer- and fac-isomers. The observed rate constants k _obs were correlated with the effect of a substituent R in the structure of ligands. The rate constants and activation parameters are in good agreement with stability constants of the studied complexes. Reactivity of the complexes towards DNA correlated well with the reported binding constants.     

极谱配位吸附波测定配合物表观稳定常数的方法研究

对目前利用配位吸附波测定配合物表观稳定常数的常用方法进行了修正,提出了更具有普遍适用性的测定配合物表观稳定常数的理论公式,并对计算方法进行了探讨,获得了预期的满意的结果。     

Stability constants of some metal complexes of triethylenetetraminehexa-acetic acid and complexometric titration of rare earths and other metals

The stability constants of some non-protonated 1:1 metal complexes of triethylenetetraminehexa-acetic acid are reported; log K values are Cd 19.8, Co(II) 20.4, Ni 19.9, Pb 19.5, Sm(III) 24.3, Zn 20.1.     

Ultrafiltration and determination of Zn- and Cu-humic substances complexes stability constants

This study exhibits that size fractionation of humic substances (HS) and their metal complexes by ultrafiltration is an efficient procedure for simultaneous determination of stability constants. Using sequential-stage ultrafiltration and a radiotracer technique the HS–Cu and HS–Zn complexes studied can gently be size-fractionated and their free metal fractions simply be discriminated. The conditional stability constants Ki obtained for size fractions of these HS metal complexes exhibit a clear molecular size dependence. Accordingly, the highest Ki values (6.6 for Zn and 6.4 for Cu) are found in the HS fractions of >105 kDa. Moreover, the overall stability constants K found for Cu (log K=5.5) and Zn complexes (log K=4.5) of the aquatic HS complexes studied are quite comparable to those reported in the literature.     

Polymer complexes XXXIV. Potentiometric and thermodynamic studies of monomeric and polymeric complexes containing 2-acrylamidosulphadiazine

2-Acrylamidosulphadiazine (ASD) was synthesized and characterized by elemental analyses, IR and 1H NMR spectra. Proton-monomeric ligand dissociation and metal-monomeric ligand stability constants of ASD with some metal ions were determined potentiometrically in 0.1 M KCl and 40% (v/v) ethanol-water mixture. In the presence of 2,2^′-azobisisobutyronitrile as initiator, the dissociation and stability constants of ASD were determined in polymeric form (PASD). The influence of temperature on the dissociation of ASD and the stability constants of their complexes in monomeric and polymeric forms were critically studied. The pK₂^H value of PASD was found to be higher than ASD, this means that the vinyl group in the monomeric form decreases the electron density and hence reduces the N-H bond strength. The stability constants of the metal complexes in polymeric form are higher than those of the monomeric form. This is quite reasonable because the ligand in a polymeric form is considered as a better complexing agent.     

Chelating Behaviour of Substituted 3-4 Aryl-Hydrazo-Pentane-2, 4-Dione: Part VI. Potentiometric and Infrared Studies of the Ligands and Their Divalent Metal Complexes

The dissociation constants of 3-phenylhydrazo-pentane-2, 4-dione and its o-, m-, p-carboxy derivatives, and the stability constants of complexes of divalent metal ions with the o-carboxy derivative are determined by pH-metric method. The ir-spectra of the ligands and some divalent metal complexes with the o-derivative are discussed.