Journal of the Belarusian State University. Chemistry
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Molybdenum – vanadium oxide solid solutions used as a tunable redox catalyst for electrochemical growing of nickel-matrix composites
The structure and morphology of electrochemically-derived metal-matrix composite obtained by embedment of redox-active MoO3 : V2O5 oxide particles in the galvanic nickel was investigated. The electron microscopic studies of electrochemically grown composite films and fractal analysis of atomic-force microscopic images provide an evidence that the efficiency of nucleation of matrix metal on the MoO3 : V2O5 particles is dependent on its redox activity yielding fine closely packed crystallites. The resultant composite film Ni – 0.6MoO3 : 0.4V2O5 film demonstrates radically improved (as compared to bare galvanic nickel) wear-resistant and corrosion resistant properties.
Copyright (c) 2026 Journal of the Belarusian State University. Chemistry https://creativecommons.org/licenses/by-nc/4.0
Quantum-chemical study of the activity of glycine, threonine and their dipeptides in relation to free radicals
A methodology for quantum-chemical studies of the antioxidant activity of compounds of various nature has been developed. Reactivity of glycine, threonine and their dipeptides with respect to active species obtained in test systems using peroxyl radicals ${\text{(RO}}{{\text{O}}^ \bullet })$ and cation radicals of 2,2¢-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) ${\text{(ABT}}{{\text{S}}^{ \bullet {\text{ + }}}})$ has been compared with the results of calculations. The most probable sites of hydrogen atom abstraction from amino acids and dipeptides molecules in the gas phase and aqueous solution has been determined by calculating the thermodynamic characteristics of the corresponding radicals. To assess the tendency of compounds to exhibit antioxidant activity via the hydrogen atom transfer mechanism, the Gibbs energies of reactions with \[{\text{HO}}_{\text{2}}^ \bullet \], ${\text{RO}}{{\text{O}}^ \bullet }$ and \[{\text{H}}{{\text{O}}^ \bullet }\] radicals, as well as the activation barriers for the thermodynamically most favourable processes of hydrogen atom abstraction by the \[{\text{HO}}_{\text{2}}^ \bullet \] radical, has been calculated. The ability of the compounds to exhibit antioxidant activity via the single electron transfer mechanism has been assessed by calculating adiabatic ionisation potentials and the energies of the highest occupied molecular orbital. The antioxidant activity series of the studied compounds, constructed based on the calculated descriptors, are consistent with experimental data. Analysis of the electron density distribution in molecules and radicals has made it possible to explain the experimentally observed differences in the antioxidant activity of glycine, glycyl-glycine, threonine and its linear and cyclic dipeptides.
Synthesis of new indole-containing derivatives of 3-acetyl-2H-chromen-2-ones under iodine catalysis and in silico analysis of the biological properties of the obtained compounds
An efficient method for the preparation of 2-(1,1-di-1H-indol-3-ylethyl)-3H-benzo[f]chromen-3-one and 3-[1-(1H-indol-2-yl)-1-(1H-indol-3-yl)ethyl]-6-nitro-2H-chromen-2-one from the corresponding 3-acetyl-2H-chromen-2‑ones and indole in dichloromethane under iodine catalysis was developed. The presence of steric hindrance near the carbonyl group resulted in a mixture of products of unidentified composition. In silico calculations on the PASS Online electronic platform showed that 2-(1,1-di-1H-indol-3-ylethyl)-3H-benzo[f]chromen-3-one and 3-[1-(1H-indol-2-yl)-1-(1H-indol-3-yl)ethyl]-6-nitro-2H-chromen-2-one may have high structural similarity to known compounds exhibiting antiarthritic activity, and also acting as substrates of cytochrome CYP2F1, an enzyme involved in the metabolism of xenobiotics and some drugs.
Barbier allylation using 2-substituted allyl halides in the directed synthesis of natural and bioactive compounds
It is noted that allylation reactions of carbonyl compounds have proven to be a reliable tool in the directed synthesis of natural and bioactive compounds. Among these reactions, Barbier allylation involving 2-substituted functionalised allyl bromides hold a significant place, as they often achieve a high degree of diastereo- and enantioselectivity, providing access to diverse structures and functional groups. This review summarises examples of the use the Barbier allylation of aldehydes as a key step in the synthesis of complex molecules with various types of biological activity. The examples are systematised according to the structure of the aldehydes and the catalytic systems employed.
Thermostable heat-insulating composite materials based on hollow microspheres and solid phosphate binders: development and research
Thermostable heat-insulating composite materials based on solid magnesium phosphate and calcium phosphate binders, fly-ash and glass hollow microspheres have been developed and proposed. Thermal and phase transformations have been studied as well as strength characteristics of the initial composites and products of their thermal treatment up to 1000 °C have been determined. It is shown that the prepared phosphate composites are thermally stable in the temperature range of 20 –1000 °С, have a density 0.4 – 0.6 g/cm3 , thermal conductivity 0.11– 0.19 W/(m ⋅ K) and show sufficiently high strength properties (compressive strength 1.4 –3.2 MPa).
Copyright (c) 2022 Journal of the Belarusian State University. Chemistry
Synthesis, structure and characterisation of late transition metal complexes with 2-(tetrazol-1-yl)pyridine
Complexes [MII(2-pytz)Cl2] (M(II) = Pt, Pd; 2-pytz = 2-(tetrazol-1-yl)pyridine) were synthesised via direct interaction of the corresponding metal chlorides (K2PtCl4 or PdCl2) with 2-pytz under ambient conditions. RuCl3 does not react with 2-pytz under reflux in the protic media, while under reflux in N, N-dimethylformamide in the presence of LiCl, decomposition of the tetrazole cycle occurred leading to the formation of Ru(III)-coordinated N, N-dimethyl-N ′-(pyridin-2-yl)formimidamide derivative Li[RuIII(Py — N =C — NMe2)2Cl2]. The complex [Ru(2-pytz)(DMSO)3Cl2] ⋅ MeOH, where DMSO is dimethyl sulfoxide, was synthesised by reacting a specially prepared precursor cis-[Ru(DMSO)4Cl2] with 2-pytz in methanol under reflux conditions. The complex [Ru(2-pytz)(DMSO)2Cl2] was synthesised by reacting cis-[Ru(DMSO)4Cl2] with 2-pytz in ethanol under reflux conditions. The resulting complexes were characterised by elemental analyses, electrospray ionisation mass-spectrometry with detection of positive and negative ions, infrared spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and simultaneous thermal analysis. The structures of complexes [Pd(2-pytz)Cl2] and [Ru(2-pytz)(DMSO)3Cl2] ⋅ MeOH were investigated by single-crystal X-ray analysis. In the former, 2-pytz shows a N,N-chelating coordination via the pyridine ring N and the tetrazole ring N2 atoms. In the latter, 2-pytz coordinates as a monodentate ligand via the tetrazole ring N4 atom. According to 1H NMR spectroscopy data, in complex [Ru(2-pytz)(DMSO)2Cl2], 2-pytz coordinates as a N, N-chelating ligand via the pyridine ring N and the tetrazole ring N2 atoms.
Phase composition and local environment of iron ions in gadolinium-doped iron oxide nanoparticles
FeO ⋅ Fe2O3 ⋅ nH2O, Fe2.95Gd0.05O4 and Fe2.9Gd0.1O4 powders were obtained by chemical precipitation from aqueous solutions. The phase composition and local environment of iron ions in gadolinium-doped iron oxide nanoparticles were studied by X-ray diffraction analysis and nuclear gamma resonance (NGR) spectroscopy. Interpretation of radiographs and NGR spectra of synthesised samples indicates the presence of a superposition of maghemite γ-Fe2O3 and iron hydroxide α-FeOOH in the samples. It was found that under the deposition of powders in the presence of gadolinium nitrate, an increase in the content of iron hydroxide α-FeOOH is observed, which disappears after annealing at 200 °C.
Synthesis and luminescent properties of strontium aluminates activated with bismuth ions
The Bi-activated strontium aluminates SrAl2O4 and Sr3Al2O6 are synthesised by the solid-phase method; their structural phase and spectral-luminescent properties are studied. The possibility of controlling the luminescence spectrum, its intensity and, consequently, the colour characteristics of the samples by changing the composition of the matrix, the nature of the activator and its concentration are shown.
Green chemistry teaching: Belarusian view through world tendencies
The disciplines curricula on green chemistry and sustainable chemistry available in various universities of the world were analysed. Trends in education development and science in this particular area were described as well as actual green chemistry teaching problems that need to be solved. Analysing the data obtained three approaches defining a trajectory for teaching the basic foundations of green chemistry were identified: British, European, and American. The first one involves in-depth study and the formation of competencies in the field of green chemistry. The second approach implies the inclusion of green chemistry in traditional chemical disciplines (organic, analytical chemistry, etc.). The third approach implies the inclusion of green chemistry as a module in such practice-oriented disciplines as biotechnology, food safety, ecology, etc. The content of the laboratory classes in green chemistry curricula and the usage of a green chemistry metric «green star» for assessment of their safety are discussed. It is proposed to join efforts of different countries for green chemistry ideas promotion and transfer the green chemistry ideas through creation of green chemistry centers of excellence for the use of its principles and methods in scientific research and the educational process.
Synthesis and structure of novel tripodal ligands based on tetrazol-5-thioles
Novel tripodal ligands (R1N4CS)3CH, where R1 = Me, Ph, were synthesised by alkylation of 1-R-tetrazol-5-thioles with iodoform in alkaline media. These ligands were identified based on data of elemental analysis, nuclear magnetic resonance spectroscopy, thermal analysis, and X-ray diffraction analysis of single crystals.
Electrochemical deposition of copper on zinc and its alloys
A new electrolyte composition and deposition conditions of quality (light, densely packed, homogeneous) copper coatings on zinc and its alloys were found. It was established that the electrochemical deposition of copper is possible from an alkaline solution containing propylene glycol. It was shown that the adding of hydroxyethylidene diphosphonic acid in the solution stabilises the electrolyte during operation and storage. The addition of morpholine provided deposition of quality copper coatings on zinc and its alloys in a wide range of current densities.
Synthesis of new multitope tetrazole-containing ligands
Drawing the experience of 5-phenyl- and 5-pyridyltetrazoles, it was shown that classical nitration-reduction methods in combination with typical alkylation reactions of tetrazole derivatives can be used to obtain multitopic polynuclear tetrazole-containing ligands. Methods for the preparation of a number of previously undescribed polynuclear tetrazole derivatives, including those combining both tetrazole and pyridine rings in the molecule, have been developed. The composition and structure of the obtained compounds were determined by elemental analysis, single crystal X-ray diffraction, NMR and IR spectroscopy. For (5-(pyridin-2-yl)tetrazol-2-yl)(5-(pyridin-2-yl)tetrazol-1-yl)methane the crystalline structure was determined and it was found that this compound forms a 3D polymer framework due to non-classical hydrogen bonds. In its crystal structure there is a network of π – π stacking interactions between tetrazole rings of neighbouring molecules, as well as between pyridine rings.
Thermal protective ability of electrochemically deposited nickel and nickel – boron coatings
The thermal protective ability of electrochemically deposited Ni and Ni – B coatings was investigated with the aim of their potential application in the production of lamella-type under-die coolers. It has been established that all studied nickelbased coatings retain thermal stability when heated in an air atmosphere in the temperature range from 500 to 700 °C. At a higher annealing temperature (800 °C), the coatings are oxidised (to the greatest extent the nickel coating) with the formation of an oxide layer up to 7–8 μm thick, the main product of oxidation is Ni0.8Cu0.2O. It is shown that the Ni – B coating with a boron content of 4.5 at. % exhibits the highest thermal stability due to the formation of a film of nickel borate (Ni3(BO3)2) on its surface during annealing. A thin continuous film of borate prevents the contact of atmospheric oxygen with the surface and, accordingly, the formation of mixed oxides of copper and nickel, which are a consequence of the thermal instability of nickel coatings during annealing.
Aggregative stability of colloidal 3D and 2D silver nanoparticles, stabilised by 11-mercaptoundecanoic acid, in the presence of singly charged cations
We studied the aggregative stability of colloidal silver quasi-spherical nanoparticles and two-dimensional nanoplates, stabilised by 11-mercaptoundecanoic acid, in the presence of phosphate buffers containing different singly charged cations (Li+ , Na+ , K+ , Cs+) and tris-HCl at pH 8.0 and concentration 0.02 mol/L which mimics the carbodiimide conjugation conditions of nanoparticles with biomolecules. Aggregation of silver nanoplates occurs in the presence of Na-phosphate buffer whereas at the same conditions the quasi-spherical nanoparticles retain colloidal stability. The difference in colloidal stability between 3D and 2D silver nanoparticles is due to the increase of the apparent acid dissociation constant on the nanoplates’ basal faces and the subsequent increase in specific bridging interactions nanoparticle – cation – nanoparticle which can be eliminated by introducing of non-ionic spacer (11-mercapto-1-undecanol) in the ligand layer. Silver nanoplates with mixed ligand layer have increased colloidal stability across the pH.
Thermodynamic properties of temozolomide in crystalline and gaseous aggregate states
Temozolomide (4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo[4,3,0]nona-2,7,9-triene-9-carboxamide) is an active component of antitumor immunosuppressive alkylating drugs, and it used largely for the treatment of various types of malignant tumors, including malignant gliomas that are difficult to treat by surgery (glioblastoma multiforme and anaplastic astrocytoma). Wide field of temozolomide application dictates the need for its comprehensive thermodynamic study. In this work temperature dependance of the temozolomide heat capacity was obtained using the adiabatic calorimetry method and the standard thermodynamic functions of crystalline temozolomide were calculated in the temperature range 80–370 K. Standard thermodynamic functions of the temozolomide in the ideal gas state were calculated using the statistical thermodynamics approach in the temperature range 0–1000 K. To obtain the standard internal energy and enthalpies of combustion and formation of crystalline temozolomide at T = 298.15 K the combustion bomb calorimetry was used. Standard enthalpy of formation of the gaseous temozolomide was calculated in the framework of the isodesmic reactions method using quantum chemical computing. To calculate standard sublimation enthalpy of temozolomide the electrostatic potential model was applied. The results obtained can find application in solving problems of optimisation of temozolomide production processes and to validate experimentally obtained values of thermodynamic properties of the temozolomide.
Extraction of anabolic steroids with aqueous-organic mixtures from hexanic solutions
The extraction of anabolic steroids (1,4-androstadiene-3,17-dione; 17α-methyltestosterone; 19-norethiocholanolone; 4-hydroxytestosterone; 4-androstene-3,17-dione; 5α-androstane-3β,17β-diol; dehydroepiandrosterone; calusterone; clostebol; methandienone; methyldienolone; nandrolone; testosterone; epitestosterone; tibolone; 19-norandrostenedione; 1-methylene-5α-androstan-3α-ol-17-one) by aqueous-organic mixtures from hexane solutions was studied at the temperature (20 ± 1) °C. Based on the experimental data obtained, the partition ratios of anabolic steroids were calculated, which were used to optimise the standard sample preparation procedure in the process of determining the compounds under study in biologically active dietary supplements and specialised sports nutrition. It was found that the most effective and selective extractants from hydrocarbon solutions are water-acetonitrile mixtures containing from 10 to 20 % by volume of water. An extraction technique has been developed for sample preparation of biologically active dietary supplements for subsequent gas chromatographic determination of anabolic steroids in them using a triple quadrupole mass spectrometric detector. The proposed method is characterised by a standard deviation of 10–15 % and a detection limit about 10 μg/kg of biologically active dietary supplements, which makes it possible to reliably determine impurities of prohibited anabolic steroids in them.
Thin composite polymethyl methacrylate films with silicon dioxide nanoparticles
Techniques for the formation of thin polymer films based on polymethyl methacrylate and composite coatings with silicon dioxide nanoparticles on glass and silicon substrates have been optimised, and their structural characteristics have been studied by atomic force microscopy. The effect of the introduction of silicon dioxide nanoparticles and their content on the structure and wettability of the formed composite coatings is described. Experimental data are presented which prove that the incorporation of SiO2 nanoparticles into the structure of the polymethyl methacrylate polymer matrix leads to changes in the roughness parameters of the coatings.
Copyright (c) 2021 Journal of the Belarusian State University. Chemistry
Sampling and concentration of polycyclic aromatic hydrocarbons from exhaust gases from a plant for synthesis of carbon nanomaterials
Currently, there is an increase in the production of carbon nanomaterials in the world, which is associated with their unique physical and mechanical properties and their use in various fields of science, industry and technology. Investigation of the chemical composition of waste gases from a propane-butane mixture pyrolysis unit during the synthesis of carbon nanomaterials is of scientific and applied value, since it allows one to study both the chemistry of the pyrolysis process of hydrocarbon mixtures and determine the degree of toxicity of waste gas from pyrolysis units. The quantitative determination of polycyclic aromatic hydrocarbons in the gaseous products of pyrolysis of a propane-butane mixture during the synthesis of carbon nanomaterials has shown that when sampling with a small amount of the Supelpak-2 adsorbent, which is widely used in international and domestic methods, efficient capture of multinuclear aromatic hydrocarbons is not ensured. Therefore, an important research issue is the development of a simple and effective method for sampling polycyclic aromatic hydrocarbons with their subsequent GC-MS analysis. The principal essence of the technique is the impregnation of two fiberglass filters with an organic low-volatile solvent – diethylene glycol, tetraethylene glycol or dimethyl sulfoxide. The latter is characterised by the highest extracting power in relation to polycyclic aromatic hydrocarbons. The developed technique makes it possible to increase the efficiency of capturing multinuclear aromatic hydrocarbons (with four or more rings in a molecule) to 96–98 % compared to a solid adsorbent under equal conditions (pyrolysis conditions, weight of adsorbent equal with filters impregnated with a solvent), where the degree of their extraction is 1–5 %. The established values of the degree of recovery of the measured components are explained by the high extracting ability of dimethyl sulfoxide in relation to multinuclear aromatic hydrocarbons.
Preparation and study of thermostable composites based on solid magnesium phosphate and calcium phosphate binders
Thermostable composite materials based on solid magnesium phosphate and calcium phosphate, as well as hybrid calcium magnesium phosphate binders have been developed and investigated. Thermal and phase transformations of the phosphate composites have been studied. Strength characteristics of composite materials have been determined in the temperature range of 20–1000 °C. It is shown that the obtained phosphate composites have high strength properties (compressive strength reaches 120–130 MPa) and are characterised by high thermal stability in the temperature range up to 1000 °С. The low weight loss of the studied composites (no more than 10 %) and the absence of significant thermal effects indicate that they are promising for use as a thermostable matrix for obtaining functional composite materials.
hybrid calcium magnesium phosphate binders
Quantum chemical study of NO reduction mechanism on Ag /Al2O3 catalysts
It was shown that N2O content among NO reduction products increases with an increase of the silver concentration in the catalyst because the nature of the catalytic centers changes and leads to a subsequent change in the mechanism of the reaction. Two reaction mechanisms were proposed and studied by means of quantum chemistry: a two-stage mechanism that proceeds via NO dimer formation on catalysts with high (above 2 wt. %) silver concentration and a parallel mechanism with isocyanates involved on catalysts with low (below 2 wt. %) silver concentration. It was demonstrated that on catalysts with high silver concentration mechanism that involves stepwise NO reduction via N2O to N2 is realised. Moreover, the final stage is complicated by the fact that formed intermediates and N2O are likely to desorb from the catalyst surface. In the case of catalysts with low silver concentration, the formation of both products (N2O and N2) proceeds in parallel and the lower activation barriers of the reaction leading to N2, as well as the thermodynamic profitability of its formation, lead to the predominance of the target product. The competition between the proposed mechanisms was studied in the case of catalytic centers represented by silver dimers. It was shown that activation barriers of reaction proceeding via NO dimer formation are lower than the corresponding barriers of the reaction with isocyanates involved, which confirms the prevalent realisation of the first process and the predominance of N2O among the final products. The obtained results explain the experimental data and are significant for further modelling of the mechanism of nitrogen oxides catalytic reduction considering the Al2O3 support.
Interaction of nitrobenzoxadiazole derivatives of piperazine and aniline with bovine serum albumine in silico and in vitro
Albumin is a globular protein of plasma of mammalian blood participating in transport of hydrophobic metabolites and drugs. Thus, studies devoted to its binding are valuable as a part of evaluation of new potential drugs or fluorescent probes for in vivo usage. Here we describe results concerning synthesis and bovine serum albumin binding assay both in silico (docking) and in vitro (spectrophotometric and spectrofluorimetric titrations) for four new 7-nitrobenzoxadiazol-4-yl (NBD) derivatives of aniline and piperazine. Experimental dissociation constant for NBD-ethynylaniline 4 was calculated to be about 10 µmol/L.
Theoretical description of the ligand function for ionoselective electrodes reversible to metal anion complexes. 3. Modeling of the electrode response in ligand and foreign ions solutions using the multi-species approach model
A description for the ligand function of the tetrathiocyanatozincate selective electrode, has been proposed, using a multi-species approach model. This model takes into account simultaneous phase-boundary, diffusion-controlled, processes of ion exchange between tetrathiocyanatozincate, thyocyanate and foreign ions unable to form zinc complexes, as well as distribution of the neutral zinc complex between phases, partial decomposition of quaternary ammonium tetrathiocyanatozincate salt and stepwise complex formation processes in water phase. The model is based on solving the system of equations describing several interphase and intraphase equilibria, assuming that diffusion flows of all membrane and solution components at the phase boundary are stationary. It provides the adequate description of tetrathiocyanatozincate selective electrode in solutions of the ligand, foreign ions and mixed solutions of the above, and predicts the effect of zinc chloride concentration in the sample solution upon electrode function slopes, lower detection limits and selectivity coefficients.
tetrathiocyanatozincate selective electrode
Adsorption of cefotaxim sodium on activated carbons of various origin
The adsorption of the cephalosporin antibiotic sodium cefotaxime (CEFOT) on two activated carbons in the temperature range 288–313 K was under study. Experimental charcoal AC obtained from hydrolysis lignin was established to be mesoporous. It demonstrates greater CEFOT adsorption activity than the commercially available charcoal OU-A made from wood and characterized by both micro- and mesoporous structure. The surface modification of both activated carbons by a water-soluble polyelectrolyte cellulose acetate sulfate in the form of sodium salt (Na-CAS) leads to an increase in specific adsorption. The multilayer model with saturation (MMS) was used for data analysis. As a result, the number of molecules on the adsorption center, the density of adsorption centers, the total number of formed layers and the energy characteristics of adsorbate – adsorbent interactions at the interface and adsorbate – adsorbate ones within the adsorption layer were estimated.
Copyright (c) 2020 Journal of the Belarusian State University. Chemistry
Synthesis of benzotriazole-intercalated dispersions of molybdenum, tungsten and vanadium oxides for tribochemical applications
The effect of dispersed particles of lamellar molybdenum, tungsten and vanadium oxides on the lubrication properties of mineral oil was investigated. It is shown that in the presence of particles of hexagonal molybdenum oxide the coefficient of friction falls two-fold (from 0.08 to 0.04) exhibiting further decrease under high mechanical load, i. e. molybdenum oxide behaves as an adaptive lubricant. The intercalation of benzotriazole into molybdenum oxide ensures additional reduction of mechanical wearing due to suppressing the tribocorrosion.
Interlaboratory study of the method for direct determination of volatile compounds in alcoholic products using ethanol as internal standard
A collaborative interlaboratory study of the method of direct determination of volatile compounds in spirit drinks and alcoholic products was performed. The proposed method employs ethanol, the major volatile component of an alcoholic product, as an internal standard. For the experiment realization, 9 laboratories from 4 countries – Belarus, Czech Republic, Turkey, Russia – were supplied with standard solutions for gas chromatographic measurements. Five aqueous ethanol 40 % (v/v) standard solutions containing target compounds in concentrations ranging from 10 to 400 mg/L of absolute alcohol were gravimetrically prepared and delivered to the participants. The interlaboratory study was evaluated according to the ISO 5725 standards and the «EuroChem» guide. The repeatability limits (within-laboratory precision) varied between 0.4 and 7.5 % for all samples and compounds, showing a sufficiently high repeatability of the method. The reproducibility limits (between-laboratory precision) were found to vary within a satisfactory range of 0.5–10.0 %. Precision of the method was well within the range predicted by the Horwitz equation for all analytes. In the study experimental estimation of trueness was performed for the first time. Analysis of the obtained results showed that the bias of the method is insignificant at the significance level 5 %. The experimentally determined concentrations of the analytes compared well to the gravimetrical values, thus showing very satisfactory accuracy of the method. The results of the interlaboratory study confirmed that the method «ethanol as internal standard» is robust and reliable and can be used as a standard method for the determination of volatile compounds in water-ethanol samples. Moreover, this method can be validated in any one laboratory without performing additional experimental studies based on the results obtained by validation of the traditional method.
Synthesis and structure of macrocyclic dinickel(II) complex with 5-(4-pyridyl)tetrazolate as coligand
The dinuclear nickel(II) complex [Ni2LmClO4] + , where Lm represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, reacts with 5-(4-pyridyl)tetrazole (PyrCN4H) to give the dinuclear complex [Ni2Lm(PyrCN4)]+ . The new complex was both isolated as perchlorate or tetraphenylborate salts and characterised by elemental analysis and IR spectroscopy. The structure of [Ni2Lm(PyrCN4)]BPh4 ⋅ MeCN was determined by single crystal X-ray diffraction, showing that tetrazolate units are in a N2,N3-bridging mode to generate dioctahedral N3Ni(µ-S)2(µ-N4CPyr)NiN3 core.
Kanamycin complexation with cellulose acetate sulphate: a promissing way from injectable to oral form of antibiotic
Water-insoluble polyelectrolyte complexes of cellulose acetate sulphate in the form of sodium salt (Na-CAS) and aminoglycoside antibiotic (AB) kanamycin (KAN) were obtained by mixing of the components aqueous solutions. The composition of the complexes was determined in accordance with the medium pH and mixing order. The increase of Na‑CAS cellobiose units per mole of AB has been shown to correlate with the decrease of pH value. The complex formation was studied by Fourier transform infrared spectroscopy, thermal analysis, X-ray analysis, laser diffraction, motion trajectory of nanoparticles analysis and scanning electron microscopy. Quantum-chemical study of the relative stability of the protonated forms of KAN in aqueous solution was performed to determine the preferred protonation sites of KAN molecule. The pKa values of KAN were calculated by means of isodesmic reactions method. The structures and binding energy for the KAN dimer and the KAN – CAS complex were also investigated by quantum-chemical methods. Na‑CAS – KAN complex itself and immobilised on the activated carbon was shown to demonstrate in vitro two times antibacterial activity of the standard (injectable) form of KAN against Mycobacterium tuberculosis. It can be recommended for in vivo clinical trials as a new form of aminoglycoside AB for oral administration.
NMR spectroscopy of Cu(II) complexes with acrylamide and sodium acrylate copolymer and ω-amino acids
Macromolecular complexes of acrylamide and sodium acrylate copolymer with microelements, including Cu(II), may form at preparation of crop protection and stimulation compositions, where the copolymer serves as an adhesive, water-retaining and film-forming agent. Preparations for crop production may also contain amino acids that protect plants under stressful conditions (cold, dry, etc.). Carboxylic groups of copolymer, carboxylic and amino groups of amino acids may be involved in mixed Cu(II) ions complexes formation. Number of methylene groups separating carboxylic and amino group of amino acids affects its ability to form a stable chelate cycle and, therefore, ligand composition of mixed Cu(II) ions complexes with acrylamide and sodium acrylate copolymer and amino acid. This work is aimed at determining the ligand composition of mixed macromolecular Cu(II) ion complexes with acrylamide and sodium acrylate copolymer and ω-amino acids (β-alanine, γ-aminobutyric acid, ε-aminocaproic acid). 13C and 1H NMR spectroscopy was used to clarify complexes composition. A complex where carboxylic groups of amino acids are ligands has been found to form in aqueous solutions of Cu(II) ions and ω-amino acid (β-alanine, γ-aminobutyric acid, ε-aminocaproic acid) at molar ratio of Cu(II) ions – amino acid equal to 1 : 6. A chelate complex where both carboxylic and amino groups of β-alanine are involved in coordination has been discovered to form in the solution containing Cu(II) ions, β-alanine, as well as acrylamide and sodium acrylate copolymer at molar ratio of Cu(II) – β-alanine – copolymer COO− equal to 1 : 6 : 30. Carboxylic groups of copolymer participate in complex formation as well. Carboxylic groups of both amino acids and the copolymer have been shown to participate in complex formation in aqueous solutions containing Cu(II) ions, either γ-aminobutyric or ε-aminokaproic acid and also acrylamide and sodium acrylate copolymer.
acrylamide and sodium acrylate copolymer
Dynamics of cavitation zone development during sonication of suspensions of magnesium particles
The cavitation activity during ultrasonic treatment of magnesium particles has been investigated. The cavitation activity recorded in a continuous mode of ultrasonic treatment altered in a wide range at constant output parameters of the generator. The rate and nature of cavitation activity variation depended on the mass fraction of particles in the suspension. It has been demonstrated that during the ultrasonic treatment of magnesium aqueous suspensions it is possible to determine the following stages: growth of cavitation activity, reaching a maximum followed by a decrease and reaching a plateau (or repeated cycles of increasing or decreasing cavitation activity). The complex nature of the cavitation activity dynamics is associated with the participation of hydrogen released as a result of the chemical interaction of magnesium particles with water in the formation of the cavitation zone. The magnesium particles modified with ultrasound were characterised with the use of scanning electron microscopy, X-ray phase analysis and thermal analysis. It has been found that ultrasonic treatment of magnesium particles resulted in the formation of magnesium hydroxide and magnesium hydride phases.
Research of the adsorption of a methylene blue enterosorbents of various nature
The results of the adsorption study of methylene blue dye as the low molecular weight toxins marker from its aqueous solutions by carbon, silicon and polymer enterosorbents are presented. It has been shown that the activated carbons modification by water-soluble cellulose polyelectrolyte makes it possible to increase their adsorption capacity. The applicability of Langmuir, Freundlich, Temkin and Redlich – Peterson adsorption models for the approximation of experimental adsorption isotherms of methylene blue on the enterosorbents has been estimated. It has been established that the three-parameter Redlich – Peterson equation describes this process better than others. This was evident from the comparison of the regression coefficients, constants and parameters values of these equations.