Vol 67, No 9 (2018)

This review addresses the key principles underlying the formation of liquid crystalline phases based on wedge-shaped and cone-shaped dendrons of different chemical nature. Despite rich phase diversity of the above systems, the development of a mesophase can be reliably predicted by the geometric model, which compares the shape of a wedge dendron with the radial density distribution in the relevant Voronoi polyhedra. 2D columnar phases formed by chiral [7]-heterohelicene molecules with long aliphatic side chains are described in detail. The as-formed columnar aggregates are shown to possess a helical 13₂ symmetry and are composed of thirteen blocks, and each block involves six molecules. In this case, the internal structure of the first-level (lower) supramolecular aggregate appears to be different from that of the helical supramolecular structure.

Concerted cycloaddition reactions were studied by the method of intersecting parabolas (M3IP) and quantum chemical calculations. Experimental data were processed within the framework of the M3IP method and an algorithm for calculating the activation energies (E) and rate constants (k) for reactions from the enthalpies of reactions was developed. The parameters E and k for twelve cycloaddition reactions not studied previously were calculated. Factors affecting the activation energies were established and evaluated; these include the enthalpy of reaction, substituents, and the molecular structure of reactants. Quantum chemical modeling and topological analysis of transition states (TS) of six concerted cycloaddition reactions were performed. Depending on structure of the starting olefins, the TS of reactions can have either a symmetric or asymmetric geometry. This influences their electronic structures, the energies of chemical bonds, and the activation energies of reactions. A comparison of the activation energy values obtained from the M3IP and DFT(B3lyp/6-311++G** ) calculations revealed good agreement between them.

The mechanism of aniline oxidation by singlet oxygen was studied by the DFT-PBE/L2 method. According to the calculations, aniline endoperoxide cannot participate in the reaction because of its energy instability. The addition of ¹O₂ to aniline proceeds with the simultaneous proton transfer to the oxygen molecule from the NH₂ group (for the syn-approach of oxygen) or from the aromatic ring (for the anti-approach). For the syn-approach of the ¹O₂ molecule, the HNC₆H₄(H)OOH intermediate is formed, whose decomposition leads to aniline p-hydroperoxide (predominantly) or p-iminoquinone. In the case of the anti-approach, the ¹O₂ molecule is inserted at the C–H bond to form aniline p-hydroperoxide (H₂NC₆H₄OOH). The decomposition of aniline p-hydroperoxide with the formation of p-aminophenol and H₂O₂ molecule proceeds via concerted mechanism.

Theoretical estimation of the efficiency factors of solid propellants whose components are CHNO compounds designed from various combinations of four structural motifs, namely pyrazole and tetrazole rings, nitro group, and trinitromethyl moiety, was performed. The positional isomerism was shown to have effect on the properties of the compounds and the energy characteristics of solid composite propellants (SCPs) on their basis. The use of these components in metal-free SCP compositions can allow one to achieve a specific impulse of 258–263 s, neither toxic HCl nor condensed products being produced upon their combustion, i.e., they are superior in energy and environmental indices to SCP formulations based on ammonium perchlorate.

Adsorption properties of amine-functionalized mesoporous silica NH₂-SBA-15, zeolite-like imidazole framework ZIF-8, and amine-functionalized metal-organic polymer NH₂-MIL-53 have been investigated. Non-modified mesoporous adsorbent SBA-15 has a higher sorption capacity for CO₂ than microporous ZIF-8, although microporous sample is characterized by a larger surface area and the values of total pore volume are close. When amine groups are present on the surface of the adsorbents, the chemical adsorption contributes more then the physical one. The adsorption capacity increases with increasing concentration of the functional groups which, in its turn, correlates with adsorbent surface area. Among the studied samples, the best adsorption properties demonstrate amine-functionalized adsorbents, aminefunctionalized mesoporous silica NH₂-SBA-15, and amine-functionalized metal-organic polymer NH₂-MIL-53.

The characteristic features of extraction of chloride acido complexes of iron(III), thallium(III), indium, and gallium in water–oxyethylated nonylphenol (neonol AF-9-12)–salting-out agent systems are studied. The role of temperature, nature of the salting-out agent, and its salting-out ability is shown.

A method for the quantification of small amounts (0.01–0.03 mol L^–1) of ionic liquids (IL) [BMIM]Br, Bu₄NBr, and Bu₄NHSO₄ in solutions using CHN analysis was proposed. The sample preparation procedure is based on evaporating the volatile components from the solution and concentrating of IL in an inert porous material (SiO₂). Prior to preparation and analysis, the solid samples were heated at a temperature selected based on DTA data. This procedure can be used to determine the content of IL in solutions and catalytic mixtures.

The mutual solubility of the components in the epichlorhydrin–water–sodium chloride system was studied in the temperature range of 20–90 °С. It was found that epichlorohydrin is salted out as the concentration of NaCl increases. The Sechenov coefficient was determined to be equal to 0.29. It was found that epichlorohydrin reacts with an aqueous solution of sodium chloride to form glycerol dichlorohydrins. Alkali formed during this reaction catalyzes the hydrolysis of epichlorohydrin to glycerol monochlorohydrin, acts as a reagent in the glycidol formation and accelerates its subsequent conversion to glycerol.

The possibility of preparing magnetic particles with the “core–shell” structure was demonstrated. The procedure is based on the treatment of carbonyl iron particles with polydimethylsiloxanes (PDMS) containing terminal or distributed over the chain carboxyl groups attached via the alkyl or aryl spacer. The presence of carboxyl-containing PDMS grafted to the surface of carbonyl iron particles was revealed by electron microscopy. Magnetorheological fluids and magnetic elastomers containing magnetic particles with the “core–shell” structure were obtained, and their rheological properties were studied.

3,3-Bis(2-nitroxyethyl) derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) were synthesized by either nucleophilic substitution of the bromine atoms of parent 3,3-bis(2- bromoethyl) compounds or nitration of structurally related 3,3-bis(2-hydroxyethyl) derivatives. The synthesized compounds comprise two different NO donating moieties, namely, oxytriaz- 1-ene 2-oxide and nitrate groups, and, therefore, can be regarded as a new type of NO-donating agents.

Polymerization of methyl methacrylate in bulk in the presence of 4-ethynylcoumarin and 4-butadiynylcoumarin (AIBN, 60 °C) leads to the formation of fluorescent polymers. A hypsochromic shift of fluorescence band maxima of polymer solutions is observed in dichloromethane. It was suggested using the quantum chemical calculations that 4-ethynylcoumarin is attached to the macroradical via the terminal carbon atom of the ethynyl group. The samples of fluorescent organic glasses were prepared. It was established that the addition of coumarins do not influence the microhardness of organic glass.

Representatives of the new heterocyclic system, pyrimido[5’,4’:3,4]pyrrolo[1,2-f]phenanthridine, were obtained via the intramolecular C–H-arylation of 6-aryl-5-(2-bromophenyl) pyrrolo[3,4-d]pyrimidine-2,4-diones catalyzed by palladium complexes with N-heterocyclic carbene ligands (Pd/NHC).

Reversed-phase HPLC on chiral stationary phases was used to study the influence of the structure of purine and 2-aminopurine conjugates with chiral heterocyclic amines on the retention times. The optimum conditions for separation of enantiomers were found. The best parameters of separation of stereoisomers of all the compounds examined were achieved on a (S,S)-Whelk-O1 column in weakly alkaline aqueous methanol systems.

A series of novel 3-substituted 7-phenylimidazo[1,2-b][1,2,4,5]tetrazines was synthesized via the reaction of 3-R-amino-1,2,4,5-tetrazines with 2-aminoacetophenone. The structural features and possibilities of modification of 7-phenylimidazotetrazine system in the reactions with nucleophiles were studied.

The combined effects of external weak magnetic fields and nuclear spins of the magnetic isotope ⁶⁷Zn on vital functions of E. coli bacterial cells were proved experimentally. Metabolism of the major elements in E. coli depends on the intensity of the external static magnetic field and zinc isotopes contained in the nutrient medium. The combined effects of the external static magnetic field and zinc magnetic isotope ⁶⁷Zn are observed in a change in the number of colony-forming units of E. coli bacteria in a range of 25–35 mT and in the content of Na, Ca and Mg in a range of 65–80 mT. The obtained data confirm magnetic sensitivity of intracellular enzymatic processes to the static magnetic field and magnetic moments of atomic nuclei.

Tetraphenylphosphonium salts of N-phosphorylated thioureas and bio-thioureas were synthesized by the reactions of their sodium salts with PPh₄Br in 96% aqueous EtOH. The structures of compounds obtained were studied by IR spectroscopy, ¹H and ³¹P{¹H} NMR spectroscopy, and electrospray ionization mass spectrometry; their compositions were confirmed by elemental analysis.