Vol 69, No 6 (2024)

A method for the synthesis of amidine-closo-dodecaborate based on glycine ethyl ester in the form of sodium salt solvate of high purity and constant composition was proposed in this work. The structure of the obtained solvate was confirmed by X-ray analysis of single crystal. In addition, total and acute toxicity as well as biodistribution in laboratory mice with B16F10 melanoma were determined for the synthesized conjugate Na[B12H11NH=C(NHCH2COOC2H5)CH3].

The process of rearrangement of the octadecahydroeicosaborate anion [trans-B20H18]2– → [iso-B20H18]2– in various solvents (acetonitrile, DMF, DMSO) under UV irradiation in dynamics has been studied using 11B NMR spectroscopy. It has been shown that the time of complete isomeric transition depends on the solvent used. In acetonitrile, complete conversion of the [trans-B20H18]2– anion to the iso form is achieved in 1 h; in DMF, the process takes about 2 h; in DMSO, about 3 h. The reverse process of rearrangement of the macropolyhedral borohydride anion [iso-B20H18]2– → [trans-B20H18]2– has been studied under the influence of temperature in DMF and it has been shown that an increase in the reaction time and an increase in the temperature of the reaction solution is accompanied by degradation of the boron cluster.

By the interaction of silver bromide with (2-bromoethyl)- and vinyltriphenylphosphonium bromides, as well as silver iodide with but-2-ene-1,4-diyl-bis(triphenylphosphonium) diiodide in DMSO, haloargentate complexes [Ph3PCH=CH2]n[Ag2Br3]n (I), [Ph3PCH=CH2]n[Ag5Br6]n (II) and [Ph3PCH2CH=CHCH2PPh3][Ag2I4] (III) were synthesized. The obtained products were characterized by IR spectroscopy and X-ray diffraction analysis (CCDC No. 2173339 (I), 2172944 (II), 1985085 (III)). According to X-ray diffraction data, compounds I–III consist of organyltriphenylphosphonium cations with tetrahedrally coordinated phosphorus atoms and the corresponding haloargentate anions of 1D-polymeric (I, II) or non-polymeric (III) structure. The anions I and II are “cross-linked” from tetrahedral {AgBr4} fragments, while anion III – from two trigonal fragments {AgBr3}. In all the resulting complexes, the Ag centers are additionally connected to each other by argentophilic contacts with Ag···Ag distances in the range of 2.8162(12)–3.371(2) Å.

Synthesis conditions were developed, new compounds of compositions (HOOC(CH2)5NH3)2SiF6 (1) and [Cu(Cpl)2(H2O)2SiF6]·2Cpl (2), where (Cpl – ɛ-caprolactam, ɛ-C6H11NO, (HOOC(CH2)5NH3)+ – cation 5-carboxypentylammonium) were obtained from aqueous solutions and studied by chemical, IR spectroscopic and X-ray diffraction analyses. In the structure of compound 1, the coordination environment of the Si atom is an almost regular octahedron. Crystals are triclinic sistem, space group P$\overline{1}$. During crystallization, caprolactam undergoes a hydration reaction and protonation. In structure 1, hydrogen bonds F...H–N were found between anions and organic cations, as well as “acidic” hydrogen bonds between carboxyl groups of cations. Compound 2 crystallizes in the triclinic system, space group P$\overline{1}$ and has a polymer chain structure. The coordination polyhedron of two independent copper cations is a tetragonally distorted octahedron formed by the O atoms of two Cpl molecules and two F atoms of hexafluorosilicate anions acting as bridges between neighboring cations. The coordination environment of the Si atom is a slightly distorted octahedron. The structure contains hydrogen bonds between the H atoms of coordinated water molecules and the O atoms of uncoordinated Cpl molecules. The geometry of hexafluorosilicate anions in structures 1 and 2 is identical.

Within the framework of the cluster approach using the 6‒31G* basis set and the hybrid density functional (B3LYP), we modeled successive abstraction of H2 from the complexes (Mg(BH4)2∙2NH3)2 and (Mg(BH4)2∙2NH3)4. It was found that the initial stage of dehydrogenation needs overcoming energy barriers ~ 1.5‒1.2 eV, which requires preheating, then the process can go on with energy release until about 10 wt % of H2 is extracted, for a higher degree of conversion, additional energy costs exceeding the combustion heat of H2 will be required when extracting more than 12.5 wt % of H2. Therefore, further dehydrogenation of this compound may turn out to be inexpedient from the energy point of view.

The heat capacity of LaMgAl11O19 with a magnetoplumbite structure was measured in the temperature range of 7–1865 K using relaxation, adiabatic and differential scanning calorimetries. Obtained temperature dependences of the heat capacity are consistent based on adiabatic calorimetry data. Thermodynamic functions (entropy, enthalpy change, reduced Gibbs energy) in the range 0–1865 K are calculated from fitted values. Thermal expansion in the range of 300-1200 K was studied by high-temperature X-ray diffraction and the coefficient of thermal expansion of LaMgAl11O19 was calculated.

The quasi-four-component system LiF–K2CrO4–Rb2CrO4–KF–RbF, which is a stable pentatope of the four-component mutual system Li+,K+,Rb+||F–,CrO, is selected for study. The prediction of non-invariant and monovariant equilibria in the system was carried out using the crystallization scheme: the eutectic equilibrium L ⇄ LiF + KxRb1–xF + α-K2xRb2–2xCrO4 + α-K3xRb3–3xFCrO4, is carried out in the system, which is confirmed by differential thermal analysis. The crystallization scheme makes it possible to predict non- and monovariant equilibria based on the analysis of faceting systems. The composition and melting point of the mixture corresponding to the four-component eutectic E□ 438 were revealed. Based on the data obtained, a 3D computer model of the phase complex of the system in the form of a concentration pentatope is constructed. The computer model clearly demonstrates the phase transformations in the system. The structure of the spatial phase diagram is revealed. In the system, the crystallizing phases are lithium fluoride, three phases of continuous series of solid solutions: based on potassium and rubidium fluorides – KxRb1–xF, based on potassium and rubidium chromates in α-polymorphic modification – α-K2xRb2–2xCrO4, based on potassium and rubidium fluoride chromates in α-polymorphic modification – α-K3xRb3–3xFCrO4.

Sorption properties of thiocarbamoylated polyethylene with respect to silver(I) from multicomponent solutions have been studied. It was found that the synthesized sorbent is characterized by a high sorption capacity and selectivity with respect to silver ions. In the static sorption mode, quantitative extraction is possible from solutions with a concentration of Ag(I) 1 · 10–4 mol/dm3 in the pH range from 1 to 7, with concomitant Ca(II), Mg(II), Cu(II), Fe(III), Zn(II), Cd(II), Ni(II), Mn(II), Co(II), Pb(II) have no effect on the degree of extraction of silver ions. The high selectivity of sorption is maintained under dynamic conditions in the presence of excessive amounts of base metal ions at pH 2. The total dynamic sorption capacity for silver is 0.35 mmol/g (solution transmission rate 2 cm3/min, pH 2, sorbent weight 0.1 g, C = 1 · 10–4 mol/dm3). The composition of the eluents providing the highest values of the degree of desorption of silver from the surface of the sorbent has been determined. It was found that during sorption using a sorbent after the sorption-desorption stage, its silver capacity decreases slightly.

An approach to the functionalization of track-etched membranes (TM) by metal-organic framework consisting of nickel, L-tryptophan, and 1,2-bis(4-pyridyl)ethylene (Ni-MOF) was developed. The effect of TM surface charge on the Ni-MOF self-assembly was studied. It was established that the microstructure of Ni-MOF does not depend on the method of TM modification. It was shown that the Ni-MOF self-assembly on TM modified with chitosan nanofibers is the most promising approach to the creation of a composite of TM and Ni-MOF, because the performance of the membrane do not reduce. Using scanning electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and IR spectroscopy it was shown that the composition and structure of free Ni-MOF (in powder form) and Ni-MOF in the consolidated material are identical. X-ray photoelectron spectra of Ni-MOF powders after its contact with solutions of Cd, Cu, Cs salts and adsorption kinetics study of Cd, Li, Ag, Zn, Mg, Li ions showed that Ni-MOF can be a potential sorbent of metal ions.

We fabricated and studied composites made of titania (TiO2), zinc oxide (ZnO) or graphitic carbon nitride (g-C3N4) nanoparticles (20–100 nm) in polymethylmethacrylate (PMMA). Nanodispersed powders of these semiconductors were mixed with mechanically grinded PMMA at a weight ratio ranging from 1 : 5 to 1 : 20. The mixture was dissolved in acetone and deposited on to the surface of water. Upon solidification and drying in air porous discs as thick as 50–200 μm were formed. They were found to have a mechanical durability at the semiconductor to PMMA ratio above 1 : 20. Scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray difractomenry of the samples demonstrated that semiconducting nanoparticles are quasiuniformly distributed in the polymer matrix. Their crystal structure, the particle size and the composition do not change in comparison to those before synthesis of the composites. Photocatalytic activity of the synthesized composites estimated by decolarization of water solution of the test dye (methylene blue) under UV irradiation was found to be reduced in the sequence TiO2, g-C3N4, ZnO.