Synthesis, IR, UV/vis-, (1)H NMR and DFT study of chelatophore functionalized 1,3-benzoxazinone spiropyrans

Six novel functionalized spiropyran's derivatives of 2H-1,3-benzoxazinone series were synthesized by introducing the substituents with chelating ability into 2H-chromene part of the 8'-formyl-7'-hydroxy-3-methyl-4-oxo-3,4-dihydro-2H-1,3-benzoxazine-2-spiro-2'-[2H]-chromene (I) by condensation with 2-aminophenol, 2-amino-4-methylphenol, 2-amino-4-nitrophenol, 2-amino-1-methylbenzimidazole, 4-amino-4H-1,2,4-triazole, N-(4-aminophenyl)acetamide. (1)H NMR, UV/vis, IR spectroscopy combined with quantum-chemical calculations employing density functional theory (DFT) were used to study their structure. All substances, except 2-amino-4-nitrophenol derivative exist in solid state and in solution solely in closed spiroform, while the mentioned one undergoes partial spiropyran ring opening. In DMSO solution NMR spectra show ratio of 2:1 of closed and opened form, correspondingly.     

Synthesis of <Superscript>28</Superscript>SiC from <Superscript>28</Superscript>SiF<Subscript>4</Subscript> and Methane in Radiofrequency (13.56 MHz) Arc Hydrogen Plasma

Some features of atmospheric-pressure radiofrequency (13.56 MHz) arc discharge and its use for obtaining bulk samples of isotope-enriched silicon carbide via the reaction between SiF₄ and methane in a hydrogen medium have been considered. It has been shown that power in this type of discharge is released mainly in the near-electrode regions. The deposition of silicon and graphite occurs in a layer-by-layer mode, so that the product carbide contains up to 40% free carbon; therefore, the process requires optimization. At the same time, the proposed type of RF arc discharge with the product deposition zone localized at the ends of the electrodes makes it possible to avoid not only additional heating of the reactor space and walls, but also the loss of expensive isotope-enriched silicon fluoride.     

Effect of Technological Parameters of Interaction between SiF4 and CaH2 on the Nature of Filtration Combustion

Interaction of silicon tetrafluoride and calcium hydride in a metallic vertical flow-through reactor in the filtration combustion mode was studied. It was shown that the stationary course of the process requires that the reactor should be heated to 100°C, and the ignition furnace, to 150°C. If the reactor is heated to more than 110°C, and the ignition furnace, to more than 170°C, the stationary mode of the process is disrupted and the reaction front is doubled. If a porous phase of varied dispersity is charged, a standing combustion wave is formed.

     

Synthesis and spectral studies of photochromism of 1,3-benzoxazinone spiropyrans

Photochromism of the spiropyran derivatives of the 1,3-benzoxazinone series was studied. A relationship between the structure of substituents and photochromic properties of the compounds was revealed.     

Synthesis and study of compounds of the general formula MIITh(VO4)2 (MII = Mn, Cd, Ca, Sr, Pb, or Ba)

Double vanadates of thorium and bivalent metals with r(M^II) ?? 0.96 ? were prepared by high-temperature solid-phase reactions. Manganese and barium derivatives were obtained for the first time. The compounds crystallize in three structural types: zircon for manganese, cadmium, calcium, strontium, and lead derivatives; scheelite for the lead phase; and monazite for the compounds containing lead and barium. Thus, two morphotropic transitions are observed in the series of the compounds studied; and for double thorium vanadates of lead, strontium, and barium, phase transitions are observed. The bands in the IR spectra were assigned. The incongruent melting points of the compounds were determined by differential scanning calorimetry. Compounds ??-PbTh(VO₄)₂ and BaTh(VO₄)₂ were studied by high-temperature X-ray diffraction.     

Investigation of complexation of functionalized 1,3-benzoxazinone spiropyrans with metal ions

For the first time, complexation between the metal ions and the molecules of photochromic benzooxazine spiropyrans was found and studied. The observed spectral-kinetic changes are explained by the complex formation between molecules of the merocyanine type, resulted from the dissociation of -C-O- bonds, and by electrostatic interaction between complex components depending on the compound structure and the metal ion nature.     

Generation of a quasimonoenergetic electron beam using a single laser pulse

The results of experiments are presented for a single laser pulse interaction with a very low density gas target under conditions when the generated wake wave is below the wave-breaking threshold and the laser pulse power is lower than the critical power for relativistic self-focusing. A quasimonoenergetic electron beam is found to be stably generated for various laser pulse intensity values by controlling the acceleration length.     

Nonlinear evolution of a relativistically strong electromagnetic wave in self-created electron-positron plasma

The nonlinear interaction between the electron-positron pairs produced by an electromagnetic wave in plasma and the wave leads to damping of the wave, frequency upshift, change of polarization, and particle acceleration. The case of a circularly polarized wave is investigated in the framework of the relativistic Vlasov equation with a source term based on the Schwinger formula for the pair creation rate.