Vol 67, No 1 (2018)

Literature data on structural rearrangements taking place in amorphous glassy polymers upon their plastic deformation are analyzed. This deformation is shown to be primarily accompanied by polymer self-dispersion into fibrillar aggregates composed of oriented macromolecules with a diameter of 1—10 nm. The above structural rearrangements proceed independently of the deformation mode of polymers (cold drawing, crazing, or shear banding of polymers under the conditions of uniaxial drawing or uniaxial compression). Principal characteristics of the formed fibrils and the conditions providing their development are considered. Information on the properties of the fibrillated glassy polymers is presented, and the pathways of their possible practical application are highlighted.

The radial distribution functions (RDFs) of aqueous solutions of ytterbium chloride were calculated using previously collected X-ray diffraction data for a wide range of solution concentrations under ambient conditions. Different solution structure models were constructed. Theoretical RDFs were calculated for each model. The optimum models for all systems studied were chosen based on the best fit between the theoretical and experimental RDFs. Quantitative characteristics of the nearest environment of Yb³⁺ and Cl^– ions in solutions, namely, the coordination number, interparticle distances, and types of ion pairs were determined. The average number of water molecules in the first coordination sphere of the cation decreases from 8.2 to 6.0 as the solution concentration increases. The structure of all systems investigated is governed by non-contact ion associates throughout the concentration range studied.

For developing new composite systems (substrate—catalyst) for hydrogen storage, the activities of Pt and Pd catalysts on various supports were compared in reversible meta-terphenyl hydrogenation and perhydro-meta-terphenyl dehydrogenation. The microstructure of the catalysts was studied. Carbon-supported catalysts are more efficient in both reversible reactions than alumina-supported systems.

The homochiral coordination polymers [Cu₄(CH₃OH)(H₂O)₄(Hbtb)(S-mal)₂]•4H₂O and [Cu₄(CH₃OH)(H₂O)₄(Hbtb)(R-mal)₂]•4H₂O were synthesized by heating S- or R-malic acid (H₃mal), 4,4′,4″-benzene-1,3,5-triyltris(benzoic acid) (H₃btb), and copper(II) acetate in an aqueous methanolic solution. The reaction with copper(II) nitrate in aqueous dioxane afforded the coordination framework [Cu₆(C₄H₈O₂)₃(H₂O)₃(btb)₄]•4C₄H₈O₂•10H₂O, which does not contain chiral ligands. The compositions and crystal structures of the new compounds were determined by single-crystal X-ray diffraction and confirmed by X-ray powder diffraction, IR spectroscopy, thermogravimetric and elemental analysis.

The reaction of equimolar amounts of ytterbocene (C₅Me₄H)₂Yb(THF)₂ and iminopyridine 2,6-Prⁱ₂C₆H₃N=CH(C₅H₄N) accompanied by the one-electron oxidation of the ytterbium ion produced the unique lanthanide complex (C₅Me₄H)₂Yb^III[2,6-Prⁱ₂-C₆H₃NCH(C₅H₄N)]–• with the iminopyridine radical-anionic ligand. The structure of the complex in the crystalline state was established by X-ray diffraction and its magnetic properties were studied in the temperature range of 1.8—300 K.

Alkali metals form mutinuclear compounds with redox-active singly and doubly reduced derivatives of sterically of hindered о-benzoquinones. Complexes [Na₆(Cat)₃(THF)₇]•4THF, [Na₅(Cat)₂(SQ)(THF)₅], [Na₄(SQ)₄(THF)₄]•THF•C₆H₁₄, [Na₄(3,5-SQ)₄(THF)₄], [K₄(SQ)₄(THF)₄]•4THF and [Li₃(SQ)₃(THF)₃]•THF (Cat is catecholate, SQ is semiquinonate) possessing high sensitivity to atmospheric oxygen were synthesized and their structures were determined. Magnetochemical measurements and quantum chemical calculations revealed that variation of the alkali metal and/or change in the structure of the polymetallic core significantly affect the energy of exchange interaction between the unpaired electrons of the paramagnetic ligands framing the polynuclear metal core formed by s-elements.

The palladium complexes of the Pd-PEPPSI type with N-heterocyclic carbenes of the 1,2,4-triazole series were synthesized in 76—99% yields by the reactions of PdCl₂ with 1,4-di- alkyl-1,2,4-triazolium salts in pyridine in the presence of KBr or KI as sources of halide ions and tetrabutylammonium salts as phase-transfer catalysts. The obtained complexes can be used as efficient catalysts for the Suzuki—Miyaura cross-coupling and are not inferior to the commercially available Pd-PEPPSI catalysts in activity.

A convenient one-pot synthesis of nitro derivatives of 2,1,3-benzothiadiazole 1-oxides by the reaction of o-nitroanilines with sulfur monochloride was developed. The structural features of 4-nitrobenzothiadiazole and its N-oxide were considered. High in vitro release of nitric oxide (69%) was found for a 6-nitro-2,1,3-benzothiadiazole sample by the Griess assay, which indicated good prospects for this class of compounds.

Biologically active dicycloalkyl di- and trisulfides were prepared by the reactions of cycloalkanes C₅—C₇ with H₂S and S₈ under the anodic (cathodic) activation of hydrogen sulfide. In dichloromethane, the electrochemical activation of H₂S in the presence of sulfur can generate sulfur-centered radical intermediates that react with cycloalkanes at room temperature. The current yield of di- and trisulfides depends on the method of redox activation of hydrogen sulfide, the concentration of sulfur, and the time of electrosynthesis. The anodic activation of hydrogen sulfide in the synthesis of dicycloalkyl di- and trisulfides in an excess S8 is more efficient than the cathodic activation. In the series of cycloalkanes C₅—C₇, the highest yield of sulfur-containing products is observed for cycloheptane.

New norbornene type monomer bearing reactive triethoxysilyl group was synthesized, and its addition homo- and copolymerization with 3-trimethylsilyltricyclonon-7-ene was studied. The target monomer was obtained using regio- and stereospecific [2σ+2σ+2π] cyclo-addition of quadricyclane with vinyltrichlorosilane followed by the reaction of the formed cycloadduct with ethanol in the presence of triethylamine. Addition polymerization was investigated over the three-component Pd-containing catalytic system (Pd complex, Na+[B(3,5-(CF₃)₂C₆H₃)₄]–(cocatalyst) and tricyclohexylphosphine). The N-heterocyclic carbene Pd complex (SIPrPd(cinn)Cl) with high activity and tolerance to the Si—O—C moieties was used as a catalyst. The yields of the homo- and copolymers were 24—68% depending on the monomer (comonomer): Pd: B: PCy₃ ratio. The obtained addition polymers are high-molecular-weight amorphous products, the glass transition temperature of which exceeds 300 °C. The presence of reactive Si(OC₂H₅)₃ groups in the homo- and copolymers made it possible to carry out a hard-to-realize cross-linking involving side substituents and followed by the formation of insoluble polymers.

N-(2-Aminoethyl)-N-(2-hydroxy-2-phenylethyl)carboxamides were synthesized from styrene oxide by ring opening with N,N-disubstituted ethylenediamines followed by N-acylation. Synthesized compounds have pronounced antiarrhythmic activity and low toxicity.

Positive and negative ion high-resolution electrospray ionization mass spectra (MS and MS₂) of cyclooligo-β-(1→6)-D-glucosamines and cyclooligo-β-(1→6)-N-acetyl-D-glucosamines were acquired and interpret. It was shown that the cleavages of glycosidic bonds are the main processes in the decay of protonated and metallated molecules. In addition, elimination of the water molecules (and ammonia for cyclooligo-β-(1→6)-D-glucosamines) was observed along with other processes including the unknown skeletal rearrangement. A primary fragmentation of the negatively charged ions (deprotonated molecules) differed from that of the positively charged ones.

Selenium and silver nanobiocomposites were synthesized based on potentially metabolizable for microbes polysaccharides arabinogalactan and starch, as well as based on humic compounds obtained from peloids (therapeutic muds) and brown coals of Mongolia. Their influence on the phytopathogenic bacterium Clavibacter michiganensis subsp. sepedonicus was studied. The absence of a negative effect of nanocomposite precursors (arabinogalactan, starch, and humic compounds) on the bacterial growth was demonstrated. All the nanocomposites studied were found to reduce the bacterial growth. Vital dyes were used to reveal that after 24 h of incubation, the examined nanobiocomposites caused changes in the morphology of the cells: the bacteria grew shorter and thicker, which led to their death. The nanoselenium composite in starch and the nanosilver composite in humic substances possessed the greatest effects. The results obtained indicate the presence of bacteriostatic and bactericidal effects in a number of nanocomposites studied.

3-Ethoxy-4,4,4-trifluorobut-2-enenitrile was synthesized by the Wittig reaction of ethyl trifluoroacetate and (cyanomethylidene)triphenylphosphorane and was separated to individual E- and Z-isomers by rectification. Each isomer undergoes stereospecific 1,3-dipolar cycloaddition to N-methyl(methaniminio)-N-methylide generated in situ to give E- and Z-isomers of 4-cyano-3-ethoxy-3-trifluoromethyl-1-methylpyrrolidine.