V. M. Nikol’skii

Potentiometric determination of the ionization constants of ethylenediamine-N,N′-diglutaric acid at 298.15 K

Step ionization constants of ethylenediamine-N,N′-diglutaric acid at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO3) are determined by means of potentiometry. The resulting data are extrapolated to zero ionic strength using an equation with one individual parameter, and the thermodynamic ionization constants are calculated. A correlation is made between the obtained results and the corresponding data for related compounds.

Thermal stability of quaternary ammonium hexafluorophosphates and halides

Thermal decomposition of hexafluorophosphates of short-chain tetraalkylammonium salts of the general formula R3R’NPF6, where R3 = R’ = CH3, C2H5, C4H9; R3 = C2H5, R’ = CH2C6H6 or CH2CH=CH2, was studied by thermal gravimetric analysis. Measurements were performed in air in the temperature interval 20–500°C. The thermal stability of halides with the same cations in the same temperature interval was studied for comparison. The effect of cation on the thermal stability of the halides and hexafluorophosphates was examined. The mechanism of thermal decomposition of quaternary ammonium hexafluorophosphates was suggested.

Composition and stability of lead(II) compounds with N-(carboxymethyl)aspartic and N,N-bis(carboxymethyl)aspartic acids in aqueous solutions

The reactions of N-(carboxymethyl)aspartic (H3Y) and N,N-bis(carboxymethyl)aspartic (H4X) acids with Pb2+ ions were studied by potentiometric titration at 298.15 K and I = 0.2, 0.5, and 1.0 (KNO3). The formation of complex species PbY−, PbHX−, and PbX2− was found and their stability constants were calculated.

Physicochemical properties of an N -decylpyridinium tetrachloroferrate ionic liquid

A low-temperature ionic liquid N-decylpyridinium tetrachloroferrate was synthesized. The temperature dependences of density and viscosity of the synthesized ionic liquid, as well as its thermal stability and magnetic properties were studied. The response of N-decylpyridinium tetrachloroferrate to magnetic field was visualized, and its structure was calculated at the DFT/B3LYB/6-31G(d,p) level of theory.

Formation constants and composition of Ga3+ and In3+ complexes with iminodisuccinic acid in aqueous solutions according to potentiometric data

The complexation of Ga3+ and In3+ with iminodisuccinic acid (H4L) at 25°C in 0.1, 0.4, 0.6, and 0.8 M KNO3 supporting solutions was studied by potentiometry and mathematical modeling. The thermodynamic constants of formation of neutral, protonated, and hydroxo complexes were calculated by extrapolating the concentration constants to the zero ionic strength using an equation with one individual parameter.

The thermodynamic characteristics of the formation of Al3+ ion complexes with iminodisuccinic acid in aqueous solutions

Complex formation between Al3+ and iminodisuccinic acid (H4L) was studied at 25°C against the background of 0.1, 0.4, 0.6, and 0.8 N solutions of KNO3 by potentiometry and mathematical modeling. The extrapolation of concentration constants to zero ionic strength was used to calculate the thermodynamic constants of the formation of the AlL−, AlHL, and AlOHL2− complexes using an equation with one individual parameter (logβ0 = 16.48 ± 0.08, 8.93 ± 0.14, and 22.88 ± 0.08, respectively).

Synthesis and some properties of complexones, succinic acid derivatives

Approaches to the synthesis of complexones, succinic acid derivatives, from maleic acid and amino derivatives were considered. Acid-base properties of these complexones were studied.

Stability constants of the complexes of ethylenediamine-N,N′-diglutaric acid with zinc, cadmium, cobalt, and manganese(II) ions

The stability constants of ethylenediamine-N,N′-diglutaric acid complexes with Zn2+, Cd2+, Co2+, and Mn2+ ions at 298.15 K and ionic strength of 0.1 mol/l were determined by potentiometric titration. Potassium nitrate was used as the background electrolyte. The results are compared with the corresponding data on related compounds.

Thermodynamic characteristics of the protolytic equilibria of tetramethylenediamine-N,N,N′,N′-tetraacetic acid

The stepwise dissociation constants of tetramethylenediamine-N,N,N′,N′-tetraacetic acid (H4L) are determined by means of potentiometry at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO3). The heat effects of the dissociation of the betaine groups of the complexone are measured by direct calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H4L are calculated via combined use of the results from thermochemical and potentiometric studies performed under identical experimental conditions. Our results are compared with the corresponding data on relative compounds.

Non-empirical quantum chemical calculations of the structure of a homologous series of N-alkylpyridinium cations

The results of non-empirical quantum chemical calculations of geometric parameters, total energies, partial atomic charges, dipole moments, energies of frontier molecular orbitals obtained within second order Möller-Plesset perturbation theory in the MP2/6-31G(d,p) approximation are presented for a homologous series of N-alkyl pyridinium cations containing from 1 to 16 carbon atoms in the hydrocarbon radical. Differences are found in the electronic structure of lower and higher homologues.