Theoretical and Experimental Chemistry最新文献

Current hypotheses and experimental data concerning the origin of biological homochirality, a phenomenon in which living systems predominantly use L-amino acids and D-sugars, are analyzed in the review. Various physical and chemical factors that may lead to the formation of an enantiomeric excess are considered.

Monocrystalline nanoplates of metallic silver with a thickness of 8 nm have been obtained by galvanic reduction of Ag⁺ on nickel nanoparticles (NiNPs) in aqueous solutions. It is found that under the studied conditions, the amount of reduced silver does not depend on the initial Ni:Ag ratio, which may indicate the passivation of NiNP surface during the process. The obtained Ni-Ag materials have been used as catalysts for the oxidation of methylene blue with hydrogen peroxide. It is shown that UV irradiation accelerates the catalytic oxidation of the dye by more than 100 times.

Binary heterostructures based on Co₃O₄ and red phosphorus have been synthesized, and their morphology and spectral characteristics have been analyzed. According to SEM data, the formation of heterostructures is accompanied by the localization of an amorphous phase of red phosphorus (P_red) on the surface of cobalt oxide. It is determined that the incorporation of 15 wt.%. of P_red into Co₃O₄ results in a CO photoconversion efficiency of 81% after 3 h of irradiation. A nonlinear dependence of the system’s photoactivity on light flux intensity is established. The effect of oxygen concentration on the efficiency of photocatalytic CO oxidation is studied.

Using EPR spectroscopy, dynamic light scattering, chromato-mass spectrometry in situ, and DFT calculations, it has been shown that the reaction of a Re(CO)₅Br dispersion in n-hexane with triethylaluminum (Et₃Al) leads to the formation of a paramagnetic low-spin (S = 1/2) rhenium complex with a square-pyramidal geometry. The reaction is accompanied by the release of CO, C₂H₄, and C₂H₆.

By pyrolysis of homobinuclear hexamethylenediaminetetraacetate complexes of cobalt or nickel sorbed on activated carbon AG-3 together with potassium tetrachloropalladate, composite electrocatalysts for oxygen reduction have been synthesized. It is shown that in addition to a carbon support, the obtained materials contain nanosized particles of palladium, cobalt, or nickel, as well as mixed cobalt oxide, PdNi alloy, and palladium-cobalt particles, depending on the used precursors. As a result of polarization measurements in an alkaline solution on a “floating” gas diffusion electrode, surface-modified with such composite materials, it is established that a palladium-cobalt electrocatalyst is the most active. Its activity exceeds that of the palladium catalyst on a carbon support.

It is found that during UV irradiation of α-substituted β-ethoxyvinyltrifluoromethylketones C₂H₅O-CH=C(R)-COCF₃ (R = H, F, CH₃) isolated in an argon matrix, interconversion processes of the corresponding conformers occur as a result of the hindered rotation of various functional groups around formally single bonds. At the same time, rotation is absent around the formally double C=C bond.

Based on the analytical and numerical analysis of the reaction-diffusion equation with a nonlinear reaction term, it is shown that the derivation of the concentration dependence of the effectiveness factor (ratio between the process rate under internal diffusion limitations and the intrinsic process rate) allows discriminating of a rate-determining step of a heterogeneous catalytic process that follows Langmuir–Rideal mechanism. The applicability of this approach is demonstrated for the identification of the rate-determining step for the process of methanol dehydration over alumina.

A method for the evaluation of intermolecular interactions between drug molecules and biomolecule fragments is proposed based on binding energy as a descriptor that quantitatively characterizes the affinity of potentially active molecules. A fragment-to-fragment approach was proposed to calculate the binding energy. This approach served as the next stage of substrate interaction modeling with biological targets after the molecular docking method. Quantum-chemical modeling was performed within the framework of the non-empirical DFT method. The approach can be recommended for preliminary affinity assessment at the molecular design stage of new biologically active heterocyclic compounds.

A review of the current state and prospects for the study of compositionally complex oxide (CCO) materials containing high-entropy oxides (HEO) and medium-entropy mixed oxides (MEMO) as dielectrics for microwave applications is presented. Fundamental approaches to the formation of stable solid solutions are considered, in particular, selection criteria for the structural type (perovskite, spinel, and garnet), cationic composition, as well as thermodynamic formation conditions. Experimental data on CCO dielectric properties in different dielectric constant ranges (ε) compared to traditional microwave dielectrics are analyzed. It is shown that CCO systems exhibit a unique combination of phase stability, controllable parameters ε, Qf, and frequency temperature stability τ_f, and also have the potential for development of next-generation microwave components. Considerable attention is paid to methods for predicting stability and dielectric properties, such as thermodynamic, quantum-chemical, and methods with elements of machine learning.

Two-stage mechanochemical treatment (MCT) of initial vanadium oxide and vanadyl hydrogen phosphate hemihydrate (VO(HPO₄)·0.5H₂O) permits to obtain the catalysts of ethane oxidative dehydrogenation (ODE) to ethylene with higher product yield and productivity. The V₂O₅, VO(HPO₄)·0.5H₂O samples (both initial and after MCT in air and ethanol) have been characterized by XRD, SEM, XPS and nitrogen adsorption technique. Activation of the catalysts by the reaction mixture leads to vanadyl pyrophosphate (VO)₂P₂O₇ (VPP) obtaining. After activation of VO(HPO₄)·0.5H₂O (MCT in air), the VPP mainly forms with an orientation along the (001) plane. These catalysts demonstrate higher results in ODE: 28-30% yield of ethylene and 0.15-0.16 g/(g·h) product productivity.