Different Complexation of Nd3+ and Sm3+ with L-Malic Acid

Complexation of Nd³⁺ and Sm³⁺ ions with L-malic acid (H₃Mal) in aqueous solutions (I = 0.1 mol/l KCl) was studied by pH-metric titration at the molar concentration ratios of H₃Mal : lanthanide equal to 1 : 2, 1 : 1, 2 : 1 in the pH range 2.8–9.5. Mathematical modeling of composite equilibrium processes was used to determine the compositions and stability constants of Nd(III) and Sm(III) L-malate complexes. It was found that in addition to the 1 : 1 and 1 : 2 complexes with different degree of deprotonation, the protonated L-malate complexes and hydroxo complexes of these metals were also formed. The Sm³⁺ and Nd³⁺ ions were established to behave differently during complexation with H₃Mal.     

Characteristics of Heteroassociates in the System Dimethylformamide-Water,According to Data of <Superscript>1</Superscript>H NMR Relaxation,Refractometry, Densimetry,and Acoustic Spectroscopy

The dimethylformamide-water system was studied by proton spin-spin relaxation (296 K) and refractometry (298 K), and the results in combination with published densimetric data (293 K) and data on the sound velocities (293 K) were used to simulate the associative equilibria. A consistent scheme of heteroassociative equilibria in the dimethylformamide-water system was suggested. The compositions of the heteroassociates were determined, and their stability constants (in the mole fraction scale), relaxation efficiency coefficients, limiting refractive indices, limiting sound velocities, and limiting densities were calculated.     

Complexation of Cerium Group Lanthanides with L-Malic Acid under an Excess of Metal Ions

Complexation of cerium group lanthanide ions (Ce, Pr, Nd, Sm) with L-malic acid in aqueous solutions was studied by pH-metric titration at a malic acid : lanthanide concentration ratio of 1 : 2, in the pH range of 3.0 to 9.0, and at ionic strength of 0.1 mol/l (KCl). The composition and the stability constants of L-malate complexes and hydroxo complexes of lanthanides were determined.     

Influence of Mg2+ Ion on Thermodynamic Parameters of Gd3+ and Ho3+ Complexation with n-Butyric Acid in Aqueous Solutions

Thermodynamic parameters of complexation were determined from data of calorimetric titration of LnCl₃-Hbut-Mg²⁺ and LnCl₃-HBut systems (Hbut is n-butyric acid) at 298 K and ionic strength 1.0 mol/l KCl. The Mg²⁺ ions were found to influence thermodynamic parameters of the lanthanide ion complexation with HBut.