Vol 88, No 12 (2018)

Formation of nanocrystalline bismuth titanate Bi₂Ti₂O₇ with pyrochlore structure obtained via thermal decomposition of a co-precipitated product has been studied. The onset of vigorous formation of Bi₂Ti₂O₇ has been shown to correlate with the melting point of the surface phase based on bismuth oxide. The upper temperature limit of the region of nanocrystalline Bi₂Ti₂O₇ stability has been found. Technological parameters of synthesis of Bi₂Ti₂O₇ with average crystallite size of 75–130 nm have been determined.

The La_1–yGd_yAlO₃ (y = 0.01–0.15) solid solutions have been studied using the magnetic dilution method. Antiferromagnetic exchange between gadolinium atoms located in the lanthanum sites has been revealed.

Kinetics and mechanism of esterification of dichloromaleic anhydride with C₁–C₄ alcohols in the presence of zeolitic catalysts have been studied. The stage-by-stage Langmuir–Hinshelwood mechanism of heterogeneous catalysis at acidic active surface sites of zeolites has been suggested. The kinetic model has been elaborated, the parameters of the experimental data fitting have been calculated.

2-Iodomethyl-2,3-dihydro[1,3]oxazolo[3,2-a]pyridinium triiodide was synthesized by the reaction of 1-allylpyridin-2(1H)-one with hydrogen iodide in the presence of hydrogen peroxide or with iodine in acetone. The title compound reacted with palladium(II) iodide in DMSO to give crystalline bis(2-iodomethyl-2,3-dihydro[1,3]oxazolo[3,2-a]pyridinium) di-μ2-iodido-tetraiodidodipalladate(II) whose structure was proved by X-ray analysis. The reaction of 2-iodomethyl-2,3-dihydro[1,3]oxazolo[3,2-a]pyridinium triiodide with sodium iodide in acetone afforded 2-iodomethyl-2,3-dihydro[1,3]oxazolo[3,2-a]pyridinium iodide which decomposed into initial 1-allylpyridin-2(1H)-one and iodine on heating in methanol.

1-(3,5-Di-tert-butyl-4-hydroxyphenyl)propane-1,2-dione dioxime and 3,5-di-tert-butyl-4-hydroxybenzohydrazide showed a high antioxidant efficiency in comparison to the known inhibitors 2,6-di-tertbutylphenol, 2,6-di-tert-butyl-4-mercaptophenol, and 2,6-di-tert-butyl-4-methylphenol (BHT), in model nonenzymatic human erythrocyte membrane lipid peroxidation.

An efficient one-pot procedure has been proposed for the synthesis of 8-methyl-5-[(methylsulfanyl) methyl]-3-thiabicyclo[3.3.1]non-7-en-6-one from accessible natural raw materials. A stable complex of the title compound with gold(III) has been obtained by the extraction method, and the mode of its coordination to the metal ion has been determined by IR and NMR spectroscopy.

The effect of triethylamine and pyridine on the kinetics and mechanism of ferrocenylboric and ferrocenylcarboxylic acids oxidation with hydrogen peroxide in water and aqueous-organic media has been studied. The addition of amines has accelerated the oxidation of ferrocenylboric acid both by hydrogen peroxide and by oxygen. Triethylamine has slowed down the oxidation of ferrocenylacetic acid and stabilized the formed zwitter-ion Fc⁺CH₂COO^–. Ferrocenylcarboxylic acid has not been oxidized by H₂O₂. The mechanism of the reaction has been suggested.

A new azomethine compound, 2-{(E)-[2-(4-hydroxybutylamino)benzimidazol-1-yl]iminomethyl}- phenol, and its cobalt(II) and copper(II) complexes were synthesized and characterized by IR, ¹Н NMR, and X-ray photoelectron spectroscopy and quantum-chemical calculations. The crystal and molecular structures of the cobalt complex were established by X-ray diffraction analysis. The oxidation state of the cobalt ion in the complex after its crystallization from the solution was defined more exactly by X-ray photoelectron spectroscopy.

The derivatives of methyl 2,4-dihydroxybenzoate containing fragments of different organic acids in position 4 have been synthesized. Their mesomorphic properties have been investigated. Lanthanide complexes of the prepared compounds have been obtained. Their spectral properties have been studied.

The model of the complex formation in a DNA oligonucleotide solution in the presence of TMPyP4 porphyrine has been recognized using a matrix method basing on the experimentally observed composition-property features. The experimental data on UV spectroscopic titration of G4 Tel22 oligonucleotide by TMPyP4 porphyrine have been interpreted in terms of equilibrium complex formation of the ligand with the macromolecule at four independent binding sites (coordination vacancies). The suggested matrix model has considered the mutual influence of the ligands bound at each of the Tel22 coordination vacancies. Sequential attachment of the TMPyP4 ligand to the Tel22(TMPyP4)_n complex has affected the shape of the UV absorption spectrum of the earlier bound ligands. The cross-validation of the conventional stepwise complex formation model and the matrix binding model has confirmed the validity of the new interpretation.

Some new derivatives of 3-amino-1-aryl-N-butyl-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]- phthalazine-2-carboxamide are synthesized via in situ Knoevenagel condensation of aromatic aldehydes with N-butyl-2-cyanoacetamide, which leads to 3-aryl-N-butyl-2-cyanoacrylamides. This is followed by the reaction with phthalhydrazide upon refluxing in ethanol under catalyst-free conditions. The products are characterized on the basis of IR, ¹H and ¹³C NMR spectral data.

A novel series of bis-1,2,4-oxadiazole fused benzothiazole derivatives 9a–9j are synthesized, and their structures are confirmed by ¹H and ¹³C NMR, and mass spectral data. All products are evaluated in vitro for their anticancer potential against a panel of four human cancer cell lines such as lung cancer (A549), breast carcinoma (MCF-7), melanoma (A375), and colon cancer (HT-29). The combretastatin-A4 is used as standard drug. All compounds 9a–9j exhibit significant anticancer activity with IC₅₀ values ranging from 0.11±0.01 to 14.6±3.89 μM. Among these, compounds 9a–9d, 9h, 9i demonstrate more potent activity than the control.

A thiophene contained imidazo phenanthroline ligand TIP {TIP = 2-(thiophen-2-yl)-1H-imidazo-[4,5-f][1,10]phenanthroline{ and its mononuclear Ru(II) polypyridyl complexes [Ru(phen)₂TIP]²⁺ (1) (phen = 1,10-phenanthrolene) and [Ru(bpy)₂TIP]²⁺ (2) (bpy = 2,2'-bipyridyl), are synthesized and characterized by UVVis, IR, ¹H and ¹³C NMR, and ESI-MS spectra. Interaction of these complexes with CT-DNA is studied using UV-Vis and florescence spectra, viscosity measurements and molecular docking studies. The latter supports binding ability of complexes with stability constants deduced from UV-Vis and florescence spectra. The studies reveal that both Ru(II) polypyridyl complexes bind to DNA predominantly by intercalation, and the binding constant of complex 1 is greater than that of complex 2. Complexes 1 and 2 cleave the pBR 322 DNA under UV light.

A group of new analogs of 1,3,4-trisubstituted pyrazoles functionalized 2-thioxoimidazolidinones and fused heterocyclic systems are synthesized. Their tests of antimicrobial activity against several bacterial and fungal strains indicated relatively high activity. The composition of the novel products was elucidated from spectroscopic data.

Synthesis of new 8-alkyl-5-aryl-1,3-dimethyl-5,7-dihydro-2H-pyrimido[5′,4′:5,6]pyrano[2,3-d]- pyrimidine-2,4,6(1H,3H)-triones by the high yield reaction of 7-amino-5-aryl-1,3-dimethyl-2,4-dioxo-1,3,4,5- tetrahydro-2H-pyrano[2,3-d]pyrimidine-6-carbonitriles with aliphatic carboxylic acids in the presence of POCl3 is presented. It is probable that synthesis of these new products proceeds via the tandem intramolecular Pinner–Dimroth rearrangement. The products are characterized by FT-IR, ¹H, and ¹³C NMR spectra and evaluated for their antibacterial activity against gram +ve bacteria (Staphylococcus aureus and Staphylococcus epidermidis) and gram–ve bacteria (Escherichia coli and Pseudomonas aeruginosa) using the disc diffusion method.

A series of novel benzofuran-isoxazole 7a–7j hybrid heterocyclic molecules are synthesized. The structures of compounds 7a–7j are assessed by IR, NMR, MASS spectroscopy and elemental analysis. The target compounds 7a–7j are screened for their antibacterial activity and demonstrated excellent to moderate activity against gram-positive and gram-negative bacteria.

Sulfuric acid immobilized on silica gel is used as an efficient catalyst in the synthesis of N-substituted pyrrole derivatives by the Clauson–Kaas pyrrole synthesis. The solvent free reaction mixture is stirred by grinding. Within very short reaction time the process leads to the corresponding products without any decomposition recorded.

The results of investigation of the electrochemical properties of cryptand 222 from the macropolycyclic ligands group and its complexes with cations were summarized. Emphasis was placed on the properties of the adsorbed layers of these substances at the electrode/solution interface. Adsorption parameters of the compounds studied were calculated in the framework of the Frumkin–Damaskin theory of adsorption of organic substances using the regression analysis. Comparative analysis of the data obtained was carried out.

The response Pd–SiO₂–Si and Pd–Ta₂O₅–SiO₂–Si metal‒insulator‒semiconductor (MIS) sensors to H₂, H₂S, NO₂, C₂H₅SH, NH₃, and Cl₂ in air was studied. The static and dynamic characteristics of the MIS sensors were obtained. The minimum detectable concentrations of the test gases were determined. It is shown that the MIS sensors are highly sensitive to the studied gases.

The electrochemical properties of photochromic compounds from the classes of diarylethenes, fulgides, quinones, spiropyrans, and dihydropyrenes exhibiting photoelectrochromic properties were analyzed for the first time. It was demonstrated that, depending on the structure and on the nature of the substituents, these compounds can exhibit electrochromic transformations under reversible oxidation of both the initial and photoinduced forms. Photochromic and electrochromic properties displayed by a number of organic compounds make them promising candidates for development of new dual-mode photo- and electrocontrolled switches for various applications.

Results of own investigations on photochromic systems bleaching reversibly under sun light depending on the intensity of excitant radiation are described. The results are aimed to be used for the development of camouflage coatings and civil cloths with photoinduced dynamic automatic color change.

The results of research on the aging of glass-filled polycaproamide materials are reviewed. The data on the influence of the type and concentration of glass fillers, stabilizers, and modifiers of different chemical structures, used in the manufacture of glass-filled polyamides, on the formation of the supramolecular structure of polyamides and porous structure of complex composites are summarized. Irreversible changes in the performance and mechanical properties of glass-filled polyamides are shown to be caused by damage accumulation on the glass-fiber–polyamide interface. This damage manifests itself in an increase in the volume and surface area of pores and a decrease in their average size due to crystallization and re-crystallization processes, which occur during initial storage time (1–3 years) and involve changes in crystallinity and ratio between different crystallinity forms in polyamide-6, as well as due to seasonal and daily temperature changes during further storage periods. A strong impact of storage conditions (temperature and humidity) on the level of polymer degradation and structural transformations is revealed. The mechanism of humidity (as a climatic factor) effect is established. A change of the relaxation mechanism at temperatures above 140°C (transition from the kinetic to diffusion region) is demonstrated. The main fields of practical application of the results presented in this paper are outlined.

The intramolecular cycloaddition of homoallyl alcohols to carbocyclic compounds in the presence of molecular and hypervalent iodine leads to the formation of propyne(ene)oxy-substituted spirotetrahydrofurans.

The reactions of tropylium salts with 2,5-diamino-1,3,4-thiadiazol, 3,5-diamino-1,2,4-thiadiazol, and 2,6-diaminopyridine have given novel products of substitution of hydrogen atoms of two amino groups in thiadiazols and of hydrogen atoms at С³ and С⁵ positions in 2,6-diaminopyridine.

A formulation superior in absorption compared to any biological tissue, including bone one, has been obtained by immobilization of radiopaque substance iodixanol on the surface of magnetic nanoparticles.

Affilation of M. V. Sangaranarayanan should read as follows: Department of Chemistry, Indian Institute of Technology, Madras Chennai, 600036 India.