Vol 68, No 9 (2019)

Reactions of concerted decomposition of cyclic molecules (Diels—Alder retro-reactions) were studied using quantum chemical modeling and the method of intersecting parabolas (M3IP model). According to results of quantum chemical calculations and topological analysis of transition states (TSs) of five concerted decomposition reactions of cyclic molecules, all TSs represent six-membered rings in which the bonds being cleaved are weak covalent ones. The presence of ring heteroatoms (N, O, or S) has a strong impact on the TS geometry and on the energy characteristics of the reactions. The M3IP model was used to process the experimental results to develop an algorithm for calculating the activation energies (E) of the reactions in question and the classical potential barriers to thermally neutral reaction (E_e⁰). Factors influencing the energies E were determined and assessed. These include the enthalpy of reaction, substituents, ring heteroatoms, the force constants of bonds, and the bond dissociation energies. A comparison of the activation energies E and the enthalpies of reaction ΔH obtained from the M3IP and density functional B3LYP/6-311++G** calculations revealed good agreement between them.

Various routes of phenylacetylene and styrene hydrogenation on the Pd(100) surface were studied by the DFT-PBE density functional method. The three-layer model of the Pd₅₃ cluster was used for the description of the Pd(100) surface. The Gibbs activation energy of hydrogenation of a phenylacetylene molecule adsorbed according to the di-σ type was shown to be 21.7 kcal mol⁻¹, whereas that of a styrene molecule was 23.4 kcal mol⁻¹. The Gibbs activation energy for the strongly adsorbed di-μ-structure of phenylacetylene is significantly higher (35.2 kcal mol⁻¹). The difference in Δ^≠G₂₉₈ values of the reaction of phenylacetylene and styrene hydrogenation explains the enhanced selectivity to styrene, but this difference is lower than the earlier calculated value for the Pd(111) surface. According to the calculations, a low coverage of the Pd(100) surface should favor the formation of stable fourfold site di-μ-structures of adsorbed phenylacetylene, which can result in a sharp decrease in the phenylacetylene hydrogenation rate and a decrease in the selectivity of hydrogenation to styrene.

A procedure was developed for the synthesis of mononuclear first row transition metal coordination compounds with adamantane-1-carboxylate (AdCO₂), which allowed the synthesis of complexes NBu₄[M(AdCO₂)₃], where M^II = Mn, Ni, Co, Zn. The X-ray diffraction study showed that all AdCO₂ act as chelating ligands, which is the main distinguishing structural feature of the synthesized compounds. The formation of four-membered metallocycles leads to a small O—M—O angle (58.4–63.0°), resulting in the distorted trigonal-prismatic environment of the central atom in the coordination anions [M(AdCO₂)₃]⁻. Under similar conditions of the synthesis, Cu^II forms the complex (NBu₄)₂[Cu(AdCO₂)₂(SO₄)] existing in two differently colored modifications (green and light blue), which is due to a small difference in the environment of Cu^II in the solid state. Upon heating above 150°C, the light blue modification is transformed into the green modification. Using 1,3-diphenyltriazene (HL), it was demonstrated that the developed synthetic approach is applicable to the preparation of compounds, in which the coordination anions [ML₃]⁻ also contain only four-membered chelate metallocycles with the N—M—N angle tightened at the metal atom. The compounds NBu₄[ML₃], where M^II = Co and Ni, were isolated in individual state and were structurally characterized.

The photophysical processes and photochemical reactions of 4-[(E)-2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-benzohexaoxacyclooctadecyn-18-yl)vinyl]-1-ethylpyridinium perchlorate and its complexes with cucurbit[7]uril in water in the absence and in the presence of lead perchlorate were studied by absorption, luminescence, and laser kinetic spectroscopy. Intersystem crossing to the triplet state and trans—cis-photoisomerization of the dye were established. The formation of an inclusion complex of the dye with cucurbit[7]uril was found.

Two series of new N-{4,6-bis[2-(het)arylvinyl]pyrimidin-2-yl}-substituted aromatic polycyclic imides were synthesized. The synthesized chromophores were characterized by UV and fluorescence spectroscopy, cyclic voltammetry, and quantum chemical density functional theory calculations. A change in the nature of aryl (hetaryl) moieties was found to cause changes in the optical properties of both solutions of these compounds and thin films prepared from these compounds. The replacement of the phthalimide moiety by the 1,8-naphthalimide one has led to a significant increase in the lowest unoccupied molecular orbital energy.

A series of biologically active metallatranes and hydrometallatranes was synthesized via the reaction of biogenic triethanolamine with salts or oxides of the essential metals; their toxicity was determined, and the immunotropic and cytotoxic properties were evaluated. Compounds causing immunostimulatory, immunosuppressive, and also competing effects on the immune response were revealed. A pronounced immunosuppressant, 1-oxovanadatran, exhibits a high and selective cytotoxic effect, inhibiting the growth of B16 melanoma cells by 39–80%, but does not affect the tumor cells of L1210 lymphocytic leukemia, P815 mastocytoma, and Lewis lung carcinoma.

The structures of individual polystyrene microspheres obtained in the presence of organosilicon surfactants were studied by transmission electron microscopy. The density of the macro-molecule distribution over the cross section of particles was determined. The synthesized latex particles have a core—shell structure.

Hydrophobic porous polymer materials were synthesized by one-step visible light polymerization from compositions consisting of phthalate-containing oligoester di(meth)acrylate MDP-2, methanol, and alkyl methacrylate (butyl methacrylate, ethylhexyl methacrylate, iso-decyl methacrylate, lauryl methacrylate, and stearyl methacrylate) compositions. The highest hydrophobization effect is observed for stearyl methacrylate. The maximum MDP-2 block photopolymerization rate is by 16–50 times higher than that of alkyl methacrylates. The specific surface areas of the synthesized porous polymers reach 4.2 m² g⁻¹, and the pore size ranges from 5.5 to 17 µm. The addition of stearyl methacrylate to the composition leads to the pore size distribution narrowing. The principal possibility of using these photopolymerizable compositions as stationary phases for liquid chromatography is shown.

Some O-polysaccharides (O-antigens) of the lipopolysaccharides of bacteria of the genus Cronobacter contain 3-deoxy-d-manno-oct-2-ulosonic acid. O-Polysaccharides of Cronobacter turicensis G3874 and Cronobacter muytjensii G3886 containing this unit were found to be structurally related to each other and to those of Cronobacter dublinensis HPB 3169 and Cronobacter sakazakii G2706 (serotype O5) studied earlier. The O-polysaccharides differ in the N-acyl group on a 3-amino-3,6-dideoxy-d-glucose residue [(R)-3-hydroxybutanoyl vs. acetyl] or in the presence or absence of the O-acetyl group on an l-rhamnose residue only. Structures of the new O-antigens were established by chemical methods and by 1D and 2D ¹H and ¹³C NMR spectroscopy applied to polysaccharides and pentasaccharides obtained by mild alkaline O-deacylation and mild acid hydrolysis of the isolated lipopolysaccharides, respectively.

The paper presents the results concerning the use of the supercomputer docking program SOL-P, which performs a search for low-energy minima of protein—ligand complexes in the MMFF94 force field without using a grid of precalculated potentials for protein—ligand interactions. The SOL-P docking program can be applied to the generalized docking of ligands with a large number of internal rotational degrees of freedom (torsions). This program is based on a tensor train global optimization algorithm. The SOL-P program was successfully applied to the docking of oligopeptide ligands consisting of 3–6 amino acid residues and having 18–25 internal rotational degrees of freedom.

Using allyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranoside as a model substrate, it was shown that the degree of orthogonality of N-phthaloyl and O-allyl protective groups under the conditions of hydrazinolysis of the phthalimide group depends on the amount of atmospheric oxygen in the reaction mixture during the reaction and during the work-up procedure.

A reaction of 5-amino-6-(tert-butyl-NNO-azoxy)-1,2,3,4-tetrazine 1,3-dioxide with nitronium tetrafluoroborate affords 5-amino-6-(nitro-NNO-azoxy)-1,2,3,4-tetrazine 1,3-dioxide, which can be of interest as an energetic compound. A plausible mechanism of its formation involves substitutive nitration of the tert-butyl group.