Том 65, № 6 (2016)

The synthesis and structure of mesoporous chromium(III) oxoterephthalate MIL-101, examples of its functional properties, and various methods of its modification are considered. The potential uses of mesoporous metal-organic framework structures for applications in various areas are analyzed. Particular attention is given to the fundamental questions of gas sorption, catalytic properties of MIL-101, as well as its potential for the development of proton exchange membranes and application in other areas.

Data on three mechanisms of aromatic electrophilic substitution in azole series have been presented. First of them is similar to an ordinary addition–elimination mechanism including the formation of a cationic σ-complex (Wheland intermediate). The second mechanism is realized according to the elimination–addition scheme and includes a protonation or a formation of a complex on the “pyridine” N atom, proton abstraction from the C atom adjacent to the above N atom, and addition of a cationoid reagent to the ylide (carbene) formed. The third mechanism proposed by the present authors can be realized for azoles having three and two N atoms of the pyridine type. It does not require the preliminary N-protonation or complex formation and occurs due to a strong electron withdrawing effect of several “pyridine” atoms, resulting in the CH-deprotonation followed by the interaction of the carbanion formed with a cation under mild conditions.

We consider the static and dynamic characteristics of interatomic bonding in the region of nonvalent interactions of a nitro group in the crystal of complex [Fe(NO)₂(SC₆H₄NO₂)]₂. Based on results obtained by modeling vibrations within the framework of the density functional theory and those of multitemperature X-ray diffraction studies, a purely vibrational nature of the abnormally large atomic displacement ellipsoid of one of the O atoms of the nitro group was revealed and a model for the influence of peculiar features of intermolecular bonding on the observed dynamics was suggested. Using topological analysis of the experimental electron density function, we studied the nature of nonvalent intermolecular interactions of the nitro group and evaluated their strength and directionality in the equilibrium state. The dependence of the “pseudodegeneracy” region of atom—atom interaction on the nature of the interaction revealed and a method for determining the vibrational smearing of interactions was suggested, which allows one to analyze the stability of the connectivity graph of the crystal.

Reduction of digallane (dpp-bian)Ga—Ga(dpp-bian) (1) (dpp-bian is the 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene dianion) with metallic sodium in THF leads to the formation of gallylsodium (dpp-bian)Ga—Na(thf)₄ (2). Reduction of digallane 1 with dicyclopentadienyltetracarbonyldiiron, vanadocene, and nickelocene furnishes the corresponding gallyl complexes (dpp-bian)Ga—FeCp(CO)₂ (3), (dpp-bian)Ga—VCp₂ (4) and [(dpp-bian)Ga]₂NiCp (5). The reaction of 1 with Cp₂Mn gives a gallium-free complex (dpp-bian)MnCp(dme) (6). Carbonylates [{(dpp-bian)Ga—M(CO)₅}{Na(thf)₂}]₂ (M = Cr (7), W (8)) and [{(dppbian)Ga}₂FeCp(CO)][Na(dme)₃] (9) were obtained by the reaction of carbonyls Cr(CO)₆, W(CO)₆, and [CpFe(CO)₂]₂ with compound 2. Diamagnetic derivatives 3, 7, 8, and 9 were characterized by ¹H NMR spectra. The structures of products 3—9 were established by single crystal X-ray diffraction.

Combined experimental and computational study of the Rh-BenzP*-catalyzed asymmetric hydrogenation (BenzP* is 1,2-bis(tert-butylmethylphosphino)benzene) of five structurally different enamides showed significant diversity in the mechanism of hydrogen activation. In neither case, the mode of the coordination of the C=C double bond or the structure of the most reactive species corresponded to the stereochemical outcome of the reaction product. This fact proved the loss of the chiral information acquired in the resting state and/or in the oxidative addition step and determination of the stereoselection on a later stage of the catalytic cycle. Quantum chemical computations showed that in all cases the stereoselection takes place on the stage of the coordination of the C=C double bond to Rh in a Rh^III non-chelating octahedral complex. The sense of enantioselection is determined via the relative easiness of the chelate cycle formation in a less hindered quadrant of the catalyst. In the case of phenyl-, 4-nitrophenyl-, and 3,5-di(trifluoromethyl)-substituted enamides, the formation of the α-dihydride intermediate in the less hindered quadrant is directed by C—H...π interaction of the tert-butyl group of the catalyst and the aryl substituent of the enamide leading to high R-enantioselectivity. In the case of the tert-butyl-substituted enamide, the formation of α-dihydride is strongly disfavored by steric hindrance and the formation of β-dihydride in the less hindered quadrant results in high S-enantioselectivity. Comparative quantum chemical computations of the asymmetric hydrogenation of the classic system DIPAMP-Rh—methyl (Z)-α-acetamidocinnamate (DIPAMP is 1,2-bis[(2-methoxyphenyl)(phenylphosphino)]ethane) revealed essentially the same mechanism of enantioselection. Early experimental results received alternative rationalization according to our computational data.

Catalytic olefination of tetrafluoroterephthalic aldehyde hydrazone was studied. Dienes with a tetrafluorophenylene bridge containing different substituents at the double bonds were obtained. Stereochemistry of the reaction, as well as molecular structure and crystal packing of the dienes were studied.

New chromatographically pure monoand hexamethanofullerenes C₆₀ and C₇₀ containing active allylic groups were synthesized by Bingel—Hirsch reaction. These compounds are promising for the studies of biological activity, as well as for obtaining on their basis new fullerenecontaining materials. The purity and composition of the synthesized compounds were confirmed by MALDI-TOF mass spectrometry and HPLC, their structure was established by ¹H and ¹³C NMR spectroscopy and X-ray diffraction.

The first example of 12-vertex metallapolyhedra, namely, tris-phosphorus-containing closo-metallacarborane ruthenium(II) cluster , was synthesized and structurally studied. A principal possibility of the use of aliphatic amines as one-electron reducing agents converting carborane ruthenium(III) complexes to structurally close ruthenium(II) compounds was experimentally demonstrated.

Detailed studies of properties of new 3-substituted 5-anilino-1,2,4-thiadiazoles containing different substituents at position 3 of the thiadiazole ring were carried out, in particular, their esterase profile and antioxidant properties. It was found that the presence in the molecule of 2-aminopropyl fragment determines an efficient and selective inhibition of butyrylcholinesterase as compared to acetylcholinesterase and carboxylesterase, with radical-scavenging activity being weak. The compounds containing a 2-aminopropenyl fragment possess a high radicalscavenging activity, weakly inhibit cholinesterases, and exhibit anticarboxylesterase activity. A wide spectrum of activity of 3-substituted 5-anilino-1,2,4-thiadiazoles as inhibitors of cholinesterases and highly efficient scavengers of free radicals gives a basis for the optimization of structure and development in this series of original agents for therapy of neurodegenerative diseases.

In this report, the data are presented on the use of synthetic biotinylated oligosaccharides corresponding to different fragments of capsular polysaccharides (CP) from S. pneumoniae serotypes 3 and 14 for evaluation of the level of vaccine-induced antibodies in the serum of mice immunized with conjugates of oligosaccharide ligands with bovine sera albumin (BSA). The level of antigen-specific antibodies assessed by enzyme-linked immunosorbent assay (ELISA) using biotinylated oligosaccharides immobilized on the surface of streptavidin precoated ELISA plates was substantially higher than that assessed using conventional ELISA plates with the bacterial CP as a coating antigen. Hence, the ELISA protocol using biotinylated oligosaccharides is much more sensitive as compared to the conventional protocol, and it can be used for the detection of antibodies in highly diluted antisera. The highest antibody titer against biotinylated oligosaccharides was detected in the antisera of mice immunized with the conjugates of BSA with tetrasaccharide ligands related to fragments of CP of two pneumococcal serotypes under study. The antigen-binding ability of antibodies to tetrasaccharides related to one and two repeating units of CP from S. pneumoniae types 14 and 3, respectively, was higher than that of antibodies to BSA conjugated with oligosaccharides of other chemical structure in the reaction of biotinylated oligosaccharides and in the bacterial agglutination test with live cells on the glass slide but not in the inhibition of ELISA with bacterial CP. This research provided a rationale for the choice of tetrasaccharide ligands for the design of the third generation vaccines against S. pneumoniae types 3 and 14 and showed the validity of the ELISA protocol with biotinylated oligosaccharides as coating antigens for the assessment of the level of neoglycoconjugate-induced antibodies.

Aiming at creation of the chemical basis for serotyping of strains of Yersinia spp., we studied the O-specific polysaccharide (OPS) of Yersinia frederiksenii H56-36/81 belonging to serotype O:60. A branched polysaccharide was obtained by mild alkaline degradation of the lipopolysaccharide (LPS) isolated from bacterial cells by the phenol—water extraction and found to contain d-ribose, l-rhamnose, and 4-deoxy d-arabino-hexose (d-ara4dHex). The last monosaccharide occurs rarely in nature and earlier has been found only in OPS of Citrobacter spp. Mild acid hydrolysis of the LPS resulted in cleavage of the d-ara4dHex side-chains to give a linear polysaccharide. Structure of the hexasaccharide repeating unit of the OPS was established by studies of both isolated polysaccharides by 1D and 2D ¹H and ¹³C NMR spectroscopy.

The possibility of rapid manufacturing of customized chemical labware and reactionware by three-dimensional (3D) printing is discussed. The advantages and disadvantages of this approach to the design of chemical equipment from different engineering plastics were demonstrated and the suitability of some materials for chemical applications was estimated: PP > PLA > > ABS > PETG (PP is polypropylene, PLA is polylactide, ABS is acrylonitrile butadiene styrene, and PETG is polyethylene terephthalate glycol). The procedure described is a powerful tool for the production of both typical and unique chemical labware; to date, the fused deposition modeling (FDM) method is already available for the everyday use in chemical laboratories. The examples of successful application of 3D-printed products were demonstrated: solvent resistance and impermeability were assessed, as well as Pd(OAc)₂-catalyzed cross-coupling between p-bromotoluene and phenylboronic acid and Ni(acac)₂-catalyzed hydrothiolation of alkyne with thiophenol were performed.