Mendeleev University of Chemical Technology of Russia
Recent publications
For the synthesis of porous sorbents based on silicon dioxide, the method of induction flow levitation was used for the first time, which makes it possible to carry out the direct synthesis of various types of silica in a continuous mode with high productivity. Induction levitation of silicon was achieved by applying two-stage heating, since the conductivity of semiconductors increases exponentially with increasing temperature. The developed method of synthesis made it possible to evaporate atoms from the silicon sample, which were stripped from the surface by an argon flow with the formation of atomic vapor. All obtained samples were carefully characterized by various physicochemical methods. On the basis of the obtained silicas, catalytic systems based on ionic liquids were synthesized, which showed high catalytic activity in the trichlorosilane disproportionation reaction, the main reaction of the ‘union-carbide’ process for the production of poly- and monocrystalline silicon. The developed method makes it possible to obtain nanospherical and nanostructured silicon dioxide with a capacity of up to 100 g/h in a continuous noncontact mode, significantly exceeding the previously developed methods for the synthesis of silica and is a promising method for the production of catalyst supports with high surface areas and functionalization possibilities by organic and inorganic active sites for heterogeneous catalysis.
New promising optical glasses containing cobalt ions in tetrahedral coordination have been synthesized, their mechanical and optical properties, as well as their characteristic temperatures, have been studied. High-quality glasses of the composition (70-x)ZnO–10SiO2-(20 + x)B2O3 (x = 0; 5; 10 wt%) doped with 0.1, 0.3, and 0.6 wt% CoO have been synthesized for the first time. The selected glass compositions were close to the eutectic one in the ZnO–SiO–B2O3 system. This made it possible to reduce the glass synthesis temperature from the 1350–1500 °C, described in the literature for similar zinc borosilicate glasses, to the 1170 °C. The presence of tetrahedral cobalt ions (CoO4) was identified by the absorption bands at 17000 cm⁻¹ (⁴A2(⁴F) → ⁴T1(⁴P)) and at 6954 cm⁻¹ (⁴A2(⁴F) → ⁴T1(⁴F)). Then the intense absorption bands in the visible region have been attributed to the ⁴A2(⁴F) → ²A1(²G), ⁴A2(⁴F) → ⁴T1(⁴P), ⁴A2(⁴F) → ²T2(²G), ⁴A2(⁴F) → ²T1(²G) and ⁴A2(⁴F) → ²E(2G) transitions. The most intense absorption band of octahedral cobalt ions (CoO6) corresponds to the ⁴T1(F) → ⁴T1(P) transition and is located in the region of 18000–20000 cm⁻¹. According to analysis of Co²⁺ absorption spectra, the tetrahedral Co²⁺ ions concentration increased with increasing the CoO concentration in glasses. To study the nature of the bond between cobalt ion and ligands, the values of the splitting force of the ligand field (10Dq) and Racah parameter B were determined.
The orientation behavior has been investigated for previously non-studied signals in the EPR spectra of the ⁵³Cr:Y2SiO5 crystal grown by Czochralski method. These signals are assigned to two Gd³⁺ centers replacing yttrium ions in two physically nonequivalent triclinic sites. The spin Hamiltonian (SH) parameters have been determined both in the laboratory and in local coordinate systems, in which the second-rank fine structure tensor becomes diagonal.
Continuous wave and pulse X-band electron paramagnetic resonance spectroscopy are used to determine structure, magnetic and relaxation properties of paramagnetic centers formed by impurity ytterbium ions in forsterite (Mg2SiO4) single crystals. It is found that Yb3+ ions substitute Mg2+ ions both as single ions and as dimeric associates with nearby magnesium vacancy. For all ytterbium centers, magnetic properties are characterized by the strong easy plane anisotropy. Measurements in temperature range 5–15 K showed that spin–lattice relaxation of the Yb3+ ions in Mg2SiO4 is due to joint action of direct one-phonon process, Raman two-phonon process and resonance two-phonon Aminov–Orbach process.
A series of new cross-linked polysiloxane polymers based on functionalized cyclo- and oligosiloxane precursors was prepared by UV-induced hydrothiolation “click”-reaction using DMPA as the initiator and their physico-mechanical properties were studied. The study of a morphology of prepared polymers by scanning electron microscopy (SEM) shows that the microstructure of all samples is homogenous. The mechanical properties of all the samples were studied by the tension and compression tests. It was shown that mechanical properties of studied materials, which significantly depends on precursors nature, can be fine-tuned by changing the structure of the initial vinyl precursor. The Young's modulus varies in the range of 4.5–117 MPa in the tension test and in the rage of 6.3–209 MPa in the compression test. The tensile strength varies in the range of 0.3–3.9 MPa in the tension test and in the rage of 2.3–28 MPa in the compression test. The thermal stability of the samples was evaluated by thermal gravimetric analysis (TGA). The weight loss was observed in the range of 275–333 °C in air and 322–370 °C in argon for prepared samples. All samples were characterized by DSC method. It was shown that only DSC curves for polymers 1 and 3 contain transitions related to glass formation (−78 and −35 °C, respectively). All polymer samples have a similar water contact angle in the range of 90–102°.
The possibility of increasing the basic properties of concrete products by using Portland cement with additions of sulfated clinkers as a binder is considered. It was found that when the binder is hydrated, aluminate and ferruginous ettringite are formed, which reinforce the hardening structure of the stone, increase its strength properties and resistance to the corrosive effect of sulfates.
In this work, the effect exerted by the type of polysaccharide support for immobilization and encapsulation on the stability of chemotrypsin was studied. The synthesized biocatalysts were compared with respect to their proteolytic activity. The highest proteolytic activity equal to 192 U/g was observed for the cellulose-chitosan composite. It was found that immobilization slightly shifts the temperature and pH optima of chemotrypsin; however, they are substantially expanded toward higher temperatures and alkaline pH values. A relative increase in the activity of immobilized chemotrypsin was most pronounced in the case of cellulose-chitosan composite. After a 24 month storage of cellulose-chitosan and cellulose-alginate composites, a decrease in chemotrypsin activity did not exceed 45–50 %. The study revealed that the optimal support for immobilization of chemotrypsin is the cellulose-chitosan composite.
Oxidative stress, to which many modern people are subjected, promotes the development of neurodegenerative, cardiovascular, inflammatory, oncological and other socially important diseases. The antioxidant system consisting in the endogenous and exogenous antioxidants exists in the body to regulate the action of free radicals and reactive oxygen species. The main source of exogenous antioxidants is food and this conditions an increase in the demand for functional foods. The market of functional drinks based on teas, cereal products, fruit and vegetable juices is developing especially actively. Drinks based on oat flakes with addition of plant components are distinguished by the high nutrition value being a rich source of dietary fibers, vitamins, minerals and antioxidants. During the experiment, a functional drink based on oat flakes and enriched with bananas, blueberry berries and a powder of elder (Sambucus nigra L.) berries recognized for the high content of anthocyanins was developed. The antioxidant potential of the experimental product was assessed by measuring the total antioxidant capacity (TAC) by the FRAP method and determining the antiradical activity (ARA) by the DPPH method. The TAC values for the aqueous and methanol extracts were 807.3±18.0 µmol quercitin equivalents /L and 948.7±47.9 µmol quercitin equivalents/L, respectively, which significantly exceeded the similar values in the control sample (by 2.44 and 1.69 times, respectively). The ARA of the methanol extract of the experimental drink was 86.49±2.01%, which was 1.9 times higher than the ARA of the control sample. It was established that about 10% of fat-soluble antioxidants are lost upon preparation of oat-based functional drinks with addition of elder berries.
Microbubbles are routinely used ultrasound contrast agents in the clinic. While a soft protein shell is commercially preferable for imaging purposes, a rigid polymer shell demonstrates prolonged agent stability. Hence, combining polymers and proteins in one shell composition can advance microbubble properties. We formulated the hybrid "protein−copolymer" microbubble shell with a complex of bovine serum albumin and an amphiphilic copolymer of N-vinyl-2-pyrrolidone and acrylic acid. The resulting microbubbles demonstrated advanced physicochemical and acoustic properties, preserving in vitro biocompatibility. Adjusting the mass ratio between protein and copolymer allowed fine tuning of the microbubble properties of concentration (by two orders, up to 10 10 MBs/mL), mean size (from 0.8 to 5 μm), and shell thickness (from 28 to 50 nm). In addition, the minimum air−liquid surface tension for the "protein−copolymer" solution enabled the highest bubble concentration. At the same time, a higher copolymer amount in the bubble shell increased the bubble size and tuned duration and intensity of the contrast during an ultrasound procedure. Demonstrated results exemplify the potential of the hybrid "protein−polymer" microbubble shell, allowing tailoring of microbubble properties for image-guided applications, combining advances of each material involved in the formulation.
Studies on the reduction of aqueous solutions of titanium tetrachloride were performed to give titanium trichloride. Experimental data on the anodic dissolution of aluminum in 2.5–10.0 % aqueous solutions of titanium tetrachloride were obtained. It was shown that the reduction of titanium tetrachloride in aqueous solutions increases the pH value and the consumption of the aluminum electrode over the stoichiometric level. It is concluded that it is expedient to use the obtained solutions for wastewater treatment after electrodeposition and effective removal of chromium (VI) compounds at the level of 90–95 % of the stoichiometric amount due to additional effects of coagulation and polycondensation of titanium compounds.
A new method for the synthesis of Pt(Mo2C) catalysts using the redox reaction between Mo2C and solution containing potassium tetracholoplatinate (II) is proposed. The obtained catalyst samples are characterized by SEM, XRD, XPS, and CV methods. As shown by microscopic studies, platinum nanoclusters are dispersed over the surface of carbide particles. The synthesized catalysts demonstrate a high catalytic activity towards hydrogen evolution reaction (HER) in 0.5 M sulphuric acid solution. Such activity is observed even at very low platinum loadings.
We report the comparison of the electrochemical performances of α-MnO2 and δ-MnO2 produced by hydrothermal treatment. The structure and morphology of these materials were analyzed by SEM, HRTEM, XRD, and XPS, while their electrochemical properties were tested in the 1 M Na2SO4 aqueous electrolyte by cyclic voltammetry, galvanostatic charge–discharge measurements, and electrochemical impedance spectroscopy. The specific capacitance of δ-MnO2 at 1 mV·s⁻¹ was 4.8 times higher than that of α-MnO2 (211 vs. 44 F·g⁻¹) because of the layered structure of δ-MnO2 that provided better availability of the electrode surface for electrolyte ions during charge–discharge cycles and pseudocapacitance behavior attributed to faradaic redox reactions. Moreover, δ-MnO2 revealed high electrochemical stability (more than 98% of the initial capacitance after 5000 charge/discharge cycles) confirming its good performance as an electrode material for pseudocapacitors. The contributions of surface and diffusion capacitances were analyzed by the differentiation method.
A method for the preparation of 4,5‐disubstituted 3‐halo‐ (chloro‐, bromo‐) isoxazolines was developed. Acetyl bromide was found to be a convenient reducing agent for 3‐halosubstituted isoxazoline N‐oxides affording target deoxygenated derivatives in good yields. Compared to the literature examples, presented approach for the synthesis of 3‐haloisoxazolines is regioselective and does not require the use of hazardous phosgene oximes. Selective transformations of the obtained products were demonstrated. A method for the regioselective preparation of 3‐haloisoxazolines is described. Its key step is a reduction of the corresponding N‐oxides with acetyl bromide that acts as both an activating and a reducing agent.
A method for the thermal cyclization of tetrazol-5-ylamino-1,2,4,5-tetrazine has been developed, leading to the formation of a new heterocyclic system based on 1,2,4-triazole and 1,2,4,5-tetrazine, a fused tricyclic compound, from which a number of other tricyclic derivatives containing nitramine, nitro, and keto groups have been obtained. Based on experimental studies and quantum-chemical calculations enthalpies of formation of the new fused energetic materials in the solid state have been found. The enthalpy of formation of the new fused tricyclic compound bis[1, 2, 4]triazolo[1,5-b:5',1'-f][1,2,4, 5]tetrazine-2,7-diamine, DATC, (3505 kJ kg⁻¹) exceeds the enthalpies of formation of diaminotetrazine (2652 kJ kg⁻¹) and 5-aminotetrazole (2442 kJ kg⁻¹), which makes the resulting framework one of the most energetic heterocyclic compounds. In addition, DATC and its derivatives turned out to be low-sensitivity and thermally stable explosives, the stability of which is comparable to the known thermostable explosives TATB and TACOT, but with higher detonation characteristics. N,N'-(bis([1, 2, 4]triazolo)[1,5-b:5',1'-f][1, 2, 4,5]tetrazine-2,7-diyl)dinitramide was used as a starting acid to obtain salts with organic bases. The hydroxylamine salt, H2DNATC, turned out to be the most powerful compound, comparable in detonation characteristics (D = 9020 m s⁻¹) to HMX, but having a higher burning rate (54 mm s⁻¹ at 10 MPa), and therefore it may be of interest as a high-energy fast-burning filler for composite propellants and gunpowder. Thermocouple-aided studies in the H2DNATC combustion wave made it possible to estimate the enthalpy of dissociation of the salt into gaseous components and to establish the combustion mechanism. The demonstrated thermal cyclization method for the preparation of fused tricyclic tetrazines provides new insights into the design of HEDMs, which may be useful for practical applications.
The aim of the study was to prepare and investigate structure and properties of a new series of stable nitronyl nitroxides bearing N-fluoroalkylpyrazolyl substituents. According to cyclic voltammetry data, a paramagnet with a difluoromethyl substituent can reversibly undergo electrochemical oxidation and reduction. In contrast, radicals with fluorinated ethyl substituents are electrochemically oxidized reversibly, but their electrochemical reduction is quasi-reversible. Molecular and crystal structures of the nitroxides were confirmed by single-crystal X-ray diffraction analysis. The crystal structures of the radicals were studied quantitatively in terms of pairwise interaction energies and energy framework analysis. Analysis of the energies of molecular pairs revealed that in crystalline phases of all nitroxides, the binding is the strongest in dimers assembled via C–H…O interactions of nitroxide O atoms with pyrazole and/or alkyl H atoms. Other dimers are formed predominantly by C–H…π interactions, and in some cases, their binding energy is almost equal to that for the aforementioned ones. The above contacts are complemented short contacts C–H…A and others, which predetermine the final crystal packing of radicals. A consequence of their packing is the geometry of relative arrangement of nitroxide groups and, above all, distances O…O between the oxygen atoms of the paramagnetic centers. These distances were found to exceed the sum of van der Waals radii; consequently, in solid phases of the paramagnets, weak antiferromagnetic exchange interactions are predominant (|J/kB| ≤ 2.74 K, H = –2J•S1S2.
In this work, we have proposed a new strategy of the synthesis of norbornene-type monomers with Si–O–C structural motifs via a straightforward and selective dehydrogenative addition reaction between 5-norbornene-2-methanol and trialkylsilanes. As a result, a set of monomers with various trilalkylsiloxy groups (alkyl – CH3, C2H5, and n-C3H7) was synthesized with the yields of 89–90%. These monomers exhibited a high reactivity in both metathesis and vinyl-addition polymerization, affording high-molecular-weight products in yields up to 90%. The metathesis polymers were rubbery with glass transition temperatures from −29 to +23 °C, while related isomeric vinyl-addition polynorbornenes were glassy polymers. Permeability (P) and diffusion (D) coefficients for these polymers were systematically evaluated for permanent gases (He, H2, O2, N2, and CO2) and C1–C4 alkanes. Studying their gas transport properties allowed to establish new structure-property relationships. Particularly, the length of alkyl fragments in trilalkylsiloxy group affected differently gas permeability of metathesis (rubbery) and vinyl-addition (glassy) polymers. Besides, it was shown that the method of linking the Si–O–C-containing group to the main chains of polymers played very important role: Alk3SiO-substituted polynorbornenes are more permeable than isomeric (AlkO)Alk2Si-substituted ones. For the metathesis polynorbornenes, P(CO2) were in the range of 152–226 Barrer, and ideal selectivity (α) of CO2/N2 – 13-16; for the vinyl-addition polynorbornenes, P(CO2) = 230–500 Barrer, and α(CO2/N2) = 14–17. Among studied polymers, promising results for ethane/methane separation was demonstrated by metathesis polynorbornene bearing tri(n-propyl)siloxymethyl substituents: P(C2H6) = 138 Barrer and α(C2H6/CH4) = 2.4. The obtained polymers were also characterized by using TGA, WAXD, and nitrogen adsorption-desorption methods.
The search for effective pharmacophores to treat ischemic stroke is precipitated by the prevalence and high mortality of the condition. Optimization of preclinical scenarios for promising neuroprotectants by mathematical modeling using up-to-date computational platforms is a well-defined and urgent task. This study aimed to develop a drug-oriented model represented by an ordinary differential equation system to study pharmacokinetics of 25Mg2+-releasing porphyrin-fullerene nanocationite PMC16 in silico using MATLAB and adjust computating model's adequatness using in vivo rat model. The developed five-compartment model predicts the distribution of nanoparticles in organs and tissues (e.g. the brain, the heart and the liver) for the purpose of experimental parameters optimization. The in silico produced pharmacokinetic curves show good agreement with the data obtained using in vivo rat model of ischemic stroke. The in silico and in vivo results indicate that PMC16 nanoparticles effectively cross the blood-brain barrier.
The two novel conglomerates were obtained by crystallization of racemic (2'S,3aS,6aR)/(2'R,3aR,6aS) (glycoluril-1-yl)-3-methylbutanoic acid and (2'R,3aR,6aR)/(2'S,3aS,6aS) (4,6-dimethylglycoluril-1-yl)pentanoic acid synthesized by highly diastereoselective condensation of 4,5-dihydroxy- imidazolidin-2-ones with racemic ureido acids. The differences in the molecular geometry of synthesized racemates were studied by X-ray diffraction that showed them to crystallize as conglomerates in non-centrosymmetric space groups Pna21 and P212121, respectively
The synthesized compound was characterized by 31P, 13C, and 1H NMR spectroscopy and MALDI-TOF mass spectroscopy. According to DSC data, the compound was initially crystalline, but the crystal structure was defective. The crystals suitable for X-ray diffraction study were prepared by slow precipitation of the compound from a solution by a vapor of another solvent. A study of the single crystal obtained in this way demonstrated that the phosphazene ring has a flattened chair conformation. It was found that the sphere circumscribed around the compound molecule has a diameter of 2.382 nm.
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560 members
Alexander Tikhomirov
  • Department of Organic Chemistry
Vladimir G Tsirelson
  • Department of Quantum Chemistry
N. P. Tarasova
  • Institute of Chemistry and Problems of Sustainable Development
Mikhail I. Shtilman
  • Scientific Educational Center of Biomaterials
Sergey Lotarev
  • International Laboratory of Functional Glass-Based Materials
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Address
Miusskaya sq., 9, 125947, Moscow, Russia
Head of institution
Prof. Alexander G. Majouga, Ph.D., Dr. Sci.
Website
http://muctr.ru