Stability constants of complexes of metal ions with peatsoil humic acids under non-acid-conditions

Stability constants of complexes of four divalent metal ions viz. Cu2+, Pb2+,Mg2+ and Cd2+ with humic acids (HA) were determined by potentiometric titration of humic acids with the corresponding salt of the divalent metals in aqueous media under non-acid-condition. The log K (logarithm of the stability constant) ranged from 1.0942 to 2.7471 for metal-humic acid complexes were determined using point-wise computational method. The order of stability constants were obtained as follows: Cu >Pb> Cd > Mg for metal -HA complexes respectively, indicating a higher degree of complexation with Cu metal ion.

Influence of d-Electron Divalent Metal Ions in Complex Formation with L-Tartaric and L-Malic Acids

Binary complexes of α-hydroxy acids (L-Tartaric acid and L-Malic acid) with d-electron metal ions (copper, cobalt, nickel) were investigated. Potentiometric measurements have been performed in aqueous solution with computer analysis of the data for determination of the stability constants of complexes formed in the studied systems. The coordination mode of the complexes was defined using spectroscopic methods: electron paramagnetic resonance (EPR), ultraviolet-visible (UV-Vis), circular dichroism (CD), and infrared (IR). Results of the equilibrium studies have provided evidence for the formation of dimers with copper(II) ions and monomers with cobalt(II) and nickel(II) ions.

Determining Stability Constants of Complexes Between Ester Betulin Derivatives and β-Cyclodextrin by Affinity Capillary Electrophoresis

Inclusion complexes of ester betulin derivatives (pentacyclic lupane triterpenoids) with β-cyclodextrin (β-CD) were studied by affinity capillary electrophoresis. Stability constants were calculated from dependencies of viscosity-corrected effective electrophoretic mobilities on β-CD concentration (0-10 mM) in background electrolytes using nonlinear regression fitting. Logarithms of stability constants at 25 °C for 1:1 and 1:2 β-CD complexes of betulin 3,28-diphthalate, betulin 3,28-disuccinate and betulin 3,28-disulfate (95 % confidence interval) are 4.25 (4.16-4.32) and 7.27 (6.73-7.50), 4.38 (4.26-4.48) and 7.58 (6.90-7.84), 4.04 (4.00-4.08) and 5.91 (4.60-6.20), respectively

Study of complexing properties of mono-derivatives of alkenyl succinic acid with copper(II) and nickel(II) ions.

Mono-derivatives of alkenyl succinic acid are considered in this paper, also their complexes with copper and nickel ions, which structure was studied by IR spectrometry method. Protonization constants and stability constants of complexes of mono-derivatives of succinic acid with copper and nickel ions are calculated by pH-metric titration method. It has been established, that mono-derivatives of succinic acid formed more stable complexes with the copper ion.