New naphtho[1,8-ef]perimidines: synthesis, fluorescence studies and application for detection of nitroanalytes

A rational approach to the synthesis of substituted naphtho[1,8-ef]perimidines based on SNH methodology and cyclization reaction in the series of condensed azines with naphthalene substituents was presented. Photophysical properties of the obtained fluorophores were studied, in particular, green fluorescence in the 485–536 nm range with quantum yield up to 32.4% was detected. HOMO-LUMO energy values and distributions for the new compounds were calculated by the DFT method in comparison with nitroanalytes and perylene. Based on the data obtained, as well as on the results of fluorescence titration, the possibility of using the new diazaperylenes as potential chemosensors for the visual detection of nitro-containing explosives was shown.

New 2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-2,2’-bipyridine-based co-polymer, synthesis, photophysical properties and response to metal cations

A new co-polymer based on fragments of 2-(2-pyridyl)monoazatriphenylene and 2,5-bis (2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione was prepared by using the Sonogashira reaction. The photophysical properties of the polymer were studied. The presence of a strong bathochromic shift of the absorption and emission maxima in comparison with the previously described monomer units is shown. The polymer exhibits an intense “turn-off” response toward Cu2+ cations.

Benzo[de]naphtho[1,8-gh]quinolines: synthesis, photophysical studies and nitro explosives detection

A rational synthetic approach to substituted naphtho[1,8-gh]quinolines using intramolecular cyclization in the presence of potassium in the series of (naphthalen-1-yl)isoquinolines is described. The photophysical properties of the obtained compounds were studied; in particular, fluorescence emission was detected in the range 454 - 482 nm with a quantum yield of up to 54%. We also calculated the HOMO-LUMO energies and optimized molecular structures for the resulting fluorophores. Based on the results of fluorescence titration, the Stern-Volmer constants (up to 21587 M-1) and the detection limits of nitroanalytes (up to 1.4 ppm) were calculated, confirming the possibility of their use as potential chemosensors for the visual detection of nitro-containing explosives.

Efficiency of ultrasonic treatment of polysaccharide from brown algae

Ultrasonic exposure can be used for depolymerization of brown algae polysaccharides. However, its effectiveness depends on several factors, including cavitation activity in the treatment medium. Therefore, the purpose of the work was to determine the cavitation activity and the effectiveness of the ultrasonic exposure to fucoidan in order to optimize the processing processes of polysaccharide from brown algae. A change in cavitation activity was revealed depending on the composition of the processing environment, as well as on the intensity of ultrasonic exposure with a constant frequency of the ultrasonic wave. Similar dynamics of change of cavitation activity were established at the intensity of ultrasonic treatment of 100 and 133 W/cm2 with amplification of electric signal at the increase of ultrasound intensity. The use of SDS in the processing medium led to an increase in cavitation activity to 14.9±0.47 mV. Treatment of the fucoidan solution for 40 minutes under various conditions allowed to obtain fractions with a change in the average hydrodynamic particle diameter from 113 nm (100 W/cm2) to 85 nm (200 W/cm2) and 124 nm (SDS).

Composite materials based on dental acrylic plastic and chitosan

Chitosan and poly(methyl methacrylate) (PMMA) composites were synthesized by polymerization with heating and mechanochemical method. The obtained polymer composites were analyzed by the ATR FT-IR spectroscopy method. The presence of intermolecular hydrogen bonds and hydrophobic interactions in formation of PMMA and chitosan polymer composites was shown.

New triple molybdate and tungstate Na5Rb7Sc2(XO4)9 (X = Mo, W)

New compounds of the composition Na5Rb7Sc2(XO4)9 (X = Mo, W) were obtained via the ceramic technology. The sequences of chemical transformations occurring during the formation of these compounds were established, and their primary characterization was performed. Both Na5Rb7Sc2(XO4)9 (X = Mo, W) were found to melt incongruently at 857 K (X = Mo) and 889 K (X = W). They are isostructural to Ag5Rb7Sc2(XO4)9 (X = Mo, W), Na5Cs7Ln2(MoO4)9 (Ln = Tm, Yb, Lu) and crystallize in the trigonal crystal system (sp. gr. R32). The crystal structures were refined with the Rietveld method using the powder X-ray diffraction data. The thermal expansion of Na5Rb7Sc2(WO4)9 was studied by high-temperature powder X-ray diffraction; it was shown that this triple tungstate belongs to high thermal expansion materials.

Synthesis of highly stable luminescent molecular crystals based on (E)-2-((3-(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2-yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid

The synthesis of (E)-2-((3-(ethoxycarbonyl)-5-methyl-4-phenylthiophen-2-yl)amino)-4-oxo-4-(p-tolyl)but-2-enoic acid was performed. This organic compound was used as a building block for the organic molecular crystals with highly stable photoluminescence at ambient conditions, which has been established during 10 years of exploitation.

Obtaining cyclopentanone in the presence of metal oxides

The possibility of obtaining cyclopentanone by pyrolysis of calcium adipate at different temperatures was considered. The pyrolysis proceeded with the formation of cyclopentanone and cyclopentene. The use of metal salts and metal oxide catalysts for the dehydrogenation of lower alkanes makes it possible to increase the yields of the target products. The best results were achieved in the presence of a «K-16u» catalyst.

Silica gel functionalized with imidazolium group via click chemistry – new stationary phase for ion chromatography

This manuscript describes the preparation of a simple effective ion-exchange material based on silica gel, on the surface of which methylimidazolium bromide is fixed using a click reaction. The resulting material was used as a stationary phase for the separation and determination of Cl–, NO2–, NO3–, I–, and SO42– using ion exchange chromatography. The separation efficiency and retention factors for the selected anions were studied in the pH range 3.5–6.5. The proposed material was used for the determination of Cl–, SO42– in water and can be suggested for successful use in real water samples.

Deoxydichlorination of aldehydes catalyzed by Diphenyl sulfoxide

The diphenyl sulfoxide-catalyzed conversion of aldehydes to 1,1-dichlorides is reported. The reaction proceeds via a sulfurous (IV)-catalysis manifold in which diphenyl sulfoxide turnover is achieved using oxalyl chloride as a consumable reagent.