Theoretical and Experimental Chemistry最新文献

The main prerequisites necessary for the construction of molecular motors, in particular, organic compound-based light-driven motors, are considered and universal requirements for their operation are formulated. Various types of Brownian motors differing in the forms of directed motion are analyzed. Development prospects and molecular design strategies are provided for such nanodevices.

According to the analysis of literature data and our experimental results, a kinetic equation for the low-temperature conversion of carbon monoxide with water vapor over a highly active copper–zinc–aluminum oxide catalyst is proposed. It is shown that the obtained kinetic parameters can be used to calculate the reaction rate and optimize the process.

The theoretical principles of a spin transition phenomenon in pseudo-octahedral iron(II) complexes are summarized. The intrinsic transfer of electrons between d-orbitals of a central ion under the action of external factors and the corresponding changes in the structural, spectral, and magnetic characteristics of matter are considered. Cooperative interactions that lead to the appearance of hysteresis of physical properties have been studied in detail. Perspective areas of practical applications of compounds with spin transitions have been provided.

MnNaW/SiO₂ oxide system based on a mesoporous silica matrix synthesized using tetraethoxysilane and cetyltrimethylammonium bromide as precursors were prepared and characterized by SEM/EDS, XRD, EPR, N₂ adsorption-desorption measurements and studied in the oxidative conversion of methane (OCM). It is shown that MnNaW/SiO₂ catalyst consists of MnO_x, Na₂WO₄, MnWO₄, and SiO₂ phases. At the reaction temperature of 750-850°C the molten Na₂WO₄ phase covers the surface of crystalline SiO₂, and the interaction of MnO_x, Na₂WO₄ and SiO₂ matrix forms “liquid glass”. It is assumed that Na_1–yMnO_x particles formed as a result of the interaction of the system components during catalyst formation and characterized by the presence of ion-radical lattice oxygen are catalytically active sites in the OCM process.

It is established that the change in molar ratio (X) of NH₄(HF₂) and Ti(BuO)₄ precursors in the reaction mixture affects the crystallite sizes of the prepared co-doped C,N,F-TiO₂ nanostructures, their S_BET, S_meso, interstitial carbon content and photocatalytic activity in the doxycycline photodegradation processes under UV light irradiation. At small X (X ≤ 0.05) co-doped anatase/brookite heterostructures with the highest photocatalytic activity are formed under visible light irradiation.

Reaction pathways of catalytic conversion of ethanol into propene are considered. It is shown that the highest propene yield is achieved over catalysts that direct the process in the following reaction pathway: ethanol → acetaldehyde → acetone → propene. A new promising propene production method that involves a two-stage process is discussed; ethanol is converted into acetone in the first stage while acetone is converted into propene in the second stage.

The ability of copper(II) complexes with 4-phenylthiosemicarbazide and amino acid anions to act as initiators of polymerization of methyl methacrylate and styrene is shown. It was found that the activation energies of polymerization and initiation in the presence of copper(II) complexes are significantly reduced in comparison with the process of thermal initiation. It is established that polymerization of methyl methacrylate initiated by the studied complexes resulted in the formation of syndiotactic polymer.

2D PLS QSPR models for analyzing substance permeability across the blood-brain barrier (BBB) using PAMPA (artificial membrane permeability assay) are developed. Physico-chemical and structural interpretation of the constructed models is performed. It is shown that nitrogen-containing fragments and a significant part of oxygen-containing functional groups negatively affect the permeability of compounds across BBB. At the same time, aromatic fragments and halogens positively affect permeability. It is found that electrostatic factors have the highest effect on BBB permeability.

The photocatalytic properties of layered semiconductors, namely KNb₃O₈, and a product of its acid treatment, namely K₃H₃Nb_10.8O₃₀ in the reduction reaction of silver ions with the formation of the corresponding metal-semiconductor nanostructures are established. Electron microscopy has shown that silver nanoparticles are deposited mainly on the edges of niobate rods and plates when potassium niobate suspensions are irradiated with UV light in the presence of AgNO₃. Silver nanoparticles of 10-30 nm are formed when K₃H₃Nb_10.8O₃₀ is used as a photocatalyst; they are deposited on the niobate surface and practically do not have a surface plasmon resonance band in the visible range of the spectrum, which may be associated with the formation of Ag₂O on the surface of silver nanoparticles or the formation of their chain aggregates.

Available approaches for quantitative description of the complexation processes on the surfaces of oxides in solutions are analyzed. The equilibrium constants for adsorption interactions of a number of amino acids with titanium and cerium dioxides in aqueous solutions are determined using these approaches. The mechanism of sorption of amino acids on TiO₂ and CeO₂ is proposed and features of protein sorption on the oxide sorbents are specified.