Theoretical and Experimental Chemistry最新文献

It is established that the effeciency of the hydrogen evolution from water–acetonitrile solutions of benzyl alcohol and a number of its derivatives under the action of visible light with the participation of crystalline graphite-like carbon nitride increases when electron-donating ability of the substituent in the para position of benzyl alcohol increases. The highest H₂ evolution rate, 720 μmol·h^–1·g^–1 (quantum yield Φ = 22% at 405 nm), is achieved in solutions of 4-methoxybenzyl alcohol in the presence of 0.1 M HCl at 40 °C.

It is shown that zinc oxide synthesized by combustion of jellied precursor forms well-crystallized micro-sized particles when treated at 600 °C. It is shown that these particles reveal high photocatalytic activity in rhodamine B dye and metronidazole degradation processes in an aqueous medium, exceeding the activity of commercial nano-sized samples of ZnO. The activity increase of the synthesized sample is connected with the presence of oxygen vacancies, which provides to formation of the charged oxygen species and OH groups on the oxide surface. The formation of zinc oxide microcrystals contributes to the separation of photogenerated charges and reduces the probability of their recombination.

The requirements for high-quality microwave (MW) dielectrics, which are used in the development of cellular communication devices (radio filters, solid-state generators, etc.) for the transition from 3G to 5G communication, are considered. The results of studies on important classes of MW dielectrics based on complex oxide systems of different crystal structures, such as potassium tungsten bronze, perovskite, pucherite, dreyerite, scheelite, as well as high-quality MW dielectrics with different permittivities, are systematized.

The formation heats for a number of gemini fluorocarbon surfactants have been estimated using density functional theory (DFT), the values of air/water interface formation energies (IFE) have been compared. It is shown that the fluorocarbon surfactants can efficiently reduce the surface tension of the air/water interface. One of the representatives of the surfactants, possessing the highest IFE value (in absolute value), has been prepared and its critical micelle concentration and the corresponding surface tension have been experimentally determined.

It is shown that new benzo[cd]indole-based heptamethinecyanines (HMCs) have an ultrashort lifetime τ of the photoexcited state and a high intensity of light absorption in the generation range of practically important neodymium lasers. The electronic structure and types of electronic transitions in HMCs are analyzed by the DFT and TD-DFT methods. The influence of vibronic and intermolecular interactions on τ is considered. The advantages of HMCs for passive mode locking of lasers over known dyes with ultrashort τ are demonstrated. The advantages of HMCs to implement passive mode locking of lasers over known dyes with ultrashort τ are demonstrated.

Series of ZrAl- and SnAl-silicate hierarchical zeolites of the BEA structural type have been synthesized by hydrothermall method, and their acidic and catalytic properties in the reaction of cyclohexanone oxidation with hydrogen peroxide have been investigated. For SnAl-BEA zeolites, the conversion of cyclohexanone into ε-caprolactone increases as the tin content in the samples increases in the range of 0.83-2.5 mole%Sn and the concentration of Lewis acid sites increases, while for ZrAl-BEA zeolites, the maximum value of conversion (80%) is achieved for the sample with 1.33 mole % Zr.

The regulation of redox and acid–base properties of MgO-Al₂O₃ systems has been carried out during the synthesis by introducing bifunctional additives of molybdate and tungstate ions. Doping with Mo and W compounds leads to an increase in the activity of Mg-Al-oxide catalysts and the selectivity of 1-butanol formation in the ethanol condensation process due to an increase in the concentration of the sites of ethanol dehydrogenation and acetaldehyde aldol condensation.

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.