Vol 70, No 6 (2025)

Magnetic Fe₃O₄ nanoparticles were synthesized by alkaline precipitation of aqueous solutions of divalent and trivalent iron salts. Synthesis of Fe_3−xGd_xO₄ nanoparticles (x = 0.05; 0.1) was performed by adding a calculated amount of Gd(NO₃)₃ 6H₂O to the initial solution of iron salt mixture. The phase composition and magnetic properties of the synthesized powders were investigated by X-ray phase analysis, Mössbauer spectroscopy on ⁵⁷Fe isotope and magnetometry at temperatures T = 7, 20 and 300 K. The investigations confirmed the formation of nanoparticles of non-stehiometric Fe_3−δO₄ magnetite, as well as magnetite doped with Gd³⁺ ions. The correlation between the average diameter of nanoparticles of the initial Fe_3−δO₄ powder and doped Fe_3−xGd_xO₄ powder and the salt used in the synthesis, as well as the concentration of Gd (x), respectively, was revealed.

The process of precipitation of bismuth(III) from perchloric acid solutions when malonic acid is added to them has been studied depending on the molar ratio of malonate ions to bismuth in the system. The basic bismuth malonate of the composition BiOH(C₃H₂O₄) (compound I) and two identical in composition but different in structure bismuth malonates containing a water molecule were synthesized: Bi(C₃H₂O₄)(C₃H₃O₄)H₂O (II) and [Bi(C₃H₂O₄)(C₃H₃O₄)] ∙ H₂O (III). The basic bismuth malonate was obtained in X-ray amorphous form, and crystal structures were determined for the other two compounds by X-ray diffraction analysis. In compound II, a water molecule coordinates the bismuth and is a ligand, while in compound III it does not. Both compounds are one-dimensional (1D) coordination polymers. After calcination of compounds II and III at 120°C, anhydrous bismuth malonate of the composition Bi(C₃H₂O₄)(C₃H₃O₄) (IV) is formed by dehydration. All new compounds I–IV were characterized by IR spectroscopy, thermal analysis, powder diffractometry, and their compositions were confirmed by elemental analysis. The structure features of polymers II and III have been discussed, the topological analysis of the electron density of Bi–O contacts has been carried out, and the main and secondary bonds in coordination polyhedra have been identified.

A new efficient method of synthesis of solid electrolyte with high lithium-ion conductivity with NASICON structure of Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) composition is proposed. The advantage of the developed method is the use of liquid-phase precursor based on titanium oxalate complex. It was found that at 750°C a single phase well crystallized LATP is formed. The total ionic conductivity value of LATP after sintering at 900°C measured by impedance spectroscopy was 2.6 × 10⁻⁴ S/cm at room temperature and the activation energy of conductivity was 0.28 eV. The presented synthesis method is promising for scale-up and mass production.

Cobalt(II) complexation with azaheterocyclic ligands L (L = 2,2ʹ-bipyridyl (bipy), 1,10-phenanthroline (phen) and 2,2ʹ-bipyridylamine (bpa)) in the presence of a monohydroxy-substituted derivative of the closo-dodecaborate anion [B₁₂H₁₁OH]^2– has been studied. Depending on the nature of the organic ligand and the synthesis conditions, the coordination compounds [Co^III(bipy)₂Cl₂]₂[B₁₂H₁₁OH], [Co^II(phen)₃][B₁₂H₁₁OH] and [Co^II(bipy)₃][B₁₂H₁₁OH] with the boron cluster anion as a counterion, as well as the mixed-ligand complex [Co^II(bpa)₂Cl₂] of a known structure, have been obtained and structurally characterized. For the first time, a redox reaction leading to the formation of a cobalt(III) complex in air has been observed for a system containing cobalt(II) and a substituted derivative of the boron cluster anion without the introduction of additional oxidizing agents.

Using the nonempirical relativistic augmented cylindrical wave method, the dependences of the electronic structure of single-layer (n₁, n₂) BN nanotubes with n₁ = 7 and 6 ≥ n₂ ≥ 1 on chirality and spin are calculated. All nanotubes are wide-bandgap semiconductors with optical gaps equal to 3.6–4.6 eV and spin-orbit splittings of the top of the valence band and the minimum of the conduction band of 0.15–0.004 meV. The energies of spin splittings in right- and left-handed nanotubes coincide, and the spin directions are opposite. The (7, 1) nanotube is most suitable for selective spin transport of electrons, which can find application in spintronics elements.

The LiCl–LiBr–Li₂SO₄ system was studied by differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Analysis of the phase complex revealed that the liquidus surface of the system consists of Li₂SO₄ crystallization fields and a continuous series of LiCl_xBr_1–x solid solutions. The composition of the minimum point M 457 is determined, in eq. %: LiCl – 18; LiBr – 42; Li₂SO₄ – 40. The crystallization temperature is 457°C, and the specific enthalpy of the phase transition is 248.1 ± 7.5 J/g. To identify phase reactions in the LiCl–LiBr–Li₂SO₄ system, a 3D spatial model was constructed and a separable model of the crystallization volumes of the system phases was modeled, and also, as a demonstration of the possibilities of using a 3D model, a diagram of the material balance of equilibrium coexisting phases was constructed for an arbitrarily selected figurative point of the system under study. To build the model in the COMPAS-3D program, data on melting temperatures and eutectic compositions of smaller–dimensional faceted elements were used, as well as on the polythermal sections of the three–component LiCl–LiBr–Li₂SO₄ system experimentally studied in the work.

The protolytic and complexation properties of some isomeric aromatic amino acids in aqueous solution were studied by a combination of pH-potentiometric and UV-spectrophotometric titration methods at I = 0.1 mol/dm³ (KCl/NaClO₄) and t = (25 ± 1)°С. The acid dissociation constants of ammonium (pKa₀) and carboxyl groups (pKa₁) in the structure of isomeric benzene-carboxylic amino acids were determined: anthranilic acid (L1), meta-aminobenzoic acid (L2) and para-aminobenzoic acid (L3); ammonium groups (pKa₁) in the structure of isomeric benzenesulfonic amino acids: orthanilic acid (L4), methanilic acid (L5), sulfanilic acid (L6). It is shown that the basicity of the amino group in the structure of the reagents decreases in the series of isomers: meta-, para-, ortho-isomer. Despite the fact that ortho-isomers are characterized by lower basicity of the amino group, it is shown that their metal complexes have the highest stability. It was found that anthranilic acid exhibits selective properties towards copper(II) ions, and orthanilic acid – towards silver(I) ions. The spectral characteristics of metal complexes of isomeric benzenesulfonic amino acids with transition metal ions: silver(I), copper(II), nickel(II) and cobalt(II) have been determined.