Theoretical and Experimental Chemistry最新文献

The inverse phase transfer process of catalytic benzoylation of α-amino acids (on the example of alanine) in a two-phase water–dichloromethane system in the presence of pyridine derivatives as catalysts is investigated. The effect of the initial concentration of alanine, its form in solution, and the initial catalyst concentration on the reaction rate and the composition of the products is studied. It is established that using 4-methyl- and 4-methoxy pyridine N-oxides combined with a double excess of the sodium salt of alanine makes it possible to obtain 2-benzamidopropionic acid with a yield of more than 80%.

The adsorption capacity of carbon adsorbent KARBON™ for tryptophan and phenylalanine from the individual solutions, their mixtures, and in the presence of leucine, isoleucine, and valine has been studied. It is established that, at the adsorption from the mixture of these amino acids, the overall removal of tryptophan and phenylalanine is an order of magnitude exceeding the removal of aliphatic analogues. Maximum removals (>90%) of tryptophan and phenylalanine are achieved at concentrations of 2.0-2.8 mmol/L, as the concentrations increase to 20-24 mmol/L, the efficiency of the removal of these amino acids is decreased approximately twice. The obtained data show that the enterofraction of the adsorbent KARBON™ can be used as an alternative to amino acid therapy for various diseases.

It has been shown by single crystal X-ray diffraction analysis that the salicylideneimine fragment of Tp^PyLn(sch)₂(H₂O) (Ln = Eu, Tb; Tp^Py– = tris(3-[2′-pyridyl]pyrazolyl)borate; schH = p-schH, m-schH are carboxylate Schiff bases prepared by the reaction of 4- and 3-aminobenzoic acids, respectively, with salicylaldehyde) is not coordinated to the metal ion. The obtained Tb³⁺ complexes exhibit ligand-centered emission, while in the luminescence spectra of Eu³⁺ compounds narrow bands of characteristic emission of Eu³⁺ are also observed. It is found that when the complexes are irradiated with UV light, the transformations of carboxylate ligands in the coordination compounds occur.

Different approaches to the development of promising photosensitizers based on polymethine dyes (PD) for photodynamic therapy are systematized, summarized, and analyzed. PD of the near-IR spectral range has drawn special attention. The influence of a heavy atom (chalcogens, halogens, and noble metals), the chromophore interaction, electron transfer, and free radicals on the singlet oxygen generation by PD is discussed. The PD photodynamic activity mechanisms under hypoxia conditions are considered. The PD structural modifications that ensure their targeted delivery to cancer cells are analyzed.

It is shown that H-forms of hierarchical aluminosilicate zeolites MOR, BEA, and MFI exhibit catalytic activity in the process of cracking n-hexane, while the introduction of nickel nanoparticles with an average size in the range of 2.3-5.5 nm changes the reaction direction towards isomerization. This opens up the prospects in creating catalysts based on Ni-containing zeolites for the reaction of the hydroisomerization of linear hydrocarbons.

It has been found that composites based on Co,N,S-doped carbon and Co₉S₈ can act as catalysts for the hydrogenation of quinoline and its monomethyl derivatives providing the formation of 1,2,3,4-tetrahydroquinolines with 75-99% yields. The high efficiency of these systems is caused first of all with the presence of Co-N_x sites in their composition, which are formed as a result of the pyrolysis of cobalt salts and poly-5-aminoindole. The use of highly dispersed Vulcan XC72R carbon black as a component of the reaction mixture during the composite catalyst preparation by the pyrolysis contributes to a greater extent to the formation of active Co-N_x sites in them, compared to graphene oxide or in the case when a carbon component is not added.

A number of CsPbBr₃/h-BN nanocomposites with different contents of inorganic halide perovskite (IHP) nanoparticles, which are characterized by bright photoluminescence (PL) in the green region of the spectrum, were obtained by mechanochemical synthesis. It is shown that the use of a mechanochemical approach leads to a significant delamination of boron nitride (both at the stage of preliminary grinding of h-BN with cesium bromide and in the process of mechanochemical production of nanocomposites), the degree of which decreases in the range of CsBr/h-BN = 1:10 > 1 :50 > 1:100 > 1:250. The increase in the content of boron nitride in the reaction mixture during the mechanochemical synthesis of CsPbBr₃/h-BN nanocomposite contributes to a reduction of the size of the formed perovskite nanoparticles leading to a significant increase in the PL intensity (I_PL). Optimal content of IHP in the synthesized nanocomposites (~25 wt.%) for obtaining the material with the highest PL intensity has been estimated from the extreme dependence between the I_PL value of CsPbBr₃/h-BN nanocomposites and their CsPbBr₃ content.

Modified nickel composites based on stabilized zirconia as prototypes of anode materials of solid oxide fuel cells (SOFC) showed high catalytic activity and stability in the oxidative reforming of alkanes (tri-reforming of methane and steam-(oxygen) reforming of butane). Modification of Ni-10Sc1CeSZ composite with Cu and CeO₂ increases its resistance to carbonization, and doping with platinum or palladium (0.1 wt.%) increases the resistance to H₂S poisoning. Structured Ni-(CeO₂, La₂O₃)-Al₂O₃/cordierite catalysts are characterized by high activity and stability in the oxidative reforming of C₁-C₃ alkanes into syngas and can be effective in an external processor integrated with SOFC. Bench tests of the fuel cell showed the achievement of acceptable electrical characteristics.

On the basis of quantum-chemical analysis, it has been shown that the formation of silicon carbide nanoclusters can occur due to the chemical reaction between two CH₃SiCl₃ molecules on the first step of the process with the subsequent reaction between CH₃SiCl₃ and the formed clusters, rather than due to the homolytic C–Si bond rupture in the CH₃SiCl₃ molecule. Cases where a chlorine atom of a CH₃SiCl₃ molecule interacts with one hydrogen atom of another CH₃SiCl₃ molecule or cluster, and three chlorine atoms of a methyltrichlorosilane molecule form a three-center complex with three hydrogen atoms of a cluster have been considered. It is shown that the second case leads to the formation of SiC nanoparticles.