Theoretical and Experimental Chemistry最新文献

It has been shown that the structure of coordination polymers formed by a macrocyclic zinc complex and aromatic carboxylates significantly affects the luminescent properties of their composites with fluorescein. It was found that the obtained materials are characterized by energy transfer between coordination and organic luminophores, resulting in their bimodal luminescence.

A chronovoltammetric method for studying the kinetics of trans-cis isomerization of coordination metal compounds is proposed, using the example of a bis(glycinate) complex of palladium(II). It is shown that the isomerization of trans-[Pd(gly)₂] to cis-[Pd(gly)₂] is described by first-order kinetics; the rate constant (k = 1.08·10^–4 s^–1) and the half-life (t_1/2 = 107 min) were determined. It has been established that isomerization follows an intramolecular mechanism characteristic of square planar complexes, without changing the coordination number.

The catalytic activity of nanocomposites based on carbon nanotubes and alumina in the process of dehydration and dehydrogenation of methanol to dimethyl ether and formaldehyde has been investigated. It is shown that the incorporation of carbon nanotubes into an alumina matrix leads to an increase in the catalyst activity in the methanol dehydrogenation reaction due to the hydrogen spillover effect.

For the first time, a graphene-like material functionalized with nitrogen- and oxygen-containing groups (gBN_f) with a developed surface was obtained by mechanochemical treatment of bulk boron nitride and ammonium carbonate with subsequent thermal exfoliation. It is established that ultrasonic delamination of gBN_f in water leads to the formation of mainly single- and double-layer boron nitride nanoparticles. It is shown that the use of ammonium carbonate for the exfoliation of hBN significantly changes its morphology, which contributes to an increase in its specific surface area. Due to the binding of folic acid (FA) molecules to functional groups on the surface of gBN_f nanoparticles, a gBN_fFA nanocomposite has been obtained, in which gBN_f nanoparticles enhance the photoluminescence intensity of folic acid by ~20 times, promoting the possible use of this material as a marker for the diagnosis of cancer cells.

The kinetics of the reaction of glycerol with acetone in the presence of natural aluminosilicates modified with arenesulfonic acid fragments has been studied. The influence of the molar ratio of the reagents, reaction temperature, and the catalyst mass fraction on glycerol conversion and a rate of the accumulation of the main product (solketal) is established. The kinetic parameters of the reaction are determined.

A method for the synthesis of protic ion-crosslinked polymeric ionic liquids (PILs), which consists in neutralization of oligosilsesquioxanes (OSS) containing secondary aliphatic amino groups and imidazole heterocycles in an organic framework with telechelic oligoethylene oxide containing terminal sulfonic acid groups, has been developed. The OSS component determines the amorphous structure of OSS-PILs. Changing the degree of neutralization allows to regulate the content of ionic groups and the mechanism of proton movement while maintaining close values of glass transition temperature (~ –27°C) with the reaching of a single-ion proton conductivity of 4.3∙10^–4 S/cm at 100°C in the absence of moisture. The OSS-PILs are promising proton-conducting media for electrochemical devices.

It is shown that the adsorption of Rhodamine 6G (Rh6G) onto a composite material obtained by oxidative chlorophosphorylation of polybutadiene rubber and bentonite with subsequent hydrolysis is satisfactory described with using the models containg at least three parameters. The need to use such multi –parametric models for description of Rh6G adsorption can be a sign of its multilayered adsorption on the adsorbent, as well as the cooperative effect. The high adsorption capacity of the composite towards Rh6G can be caused by its electrostatic binding with phosphate and phosphonate functional groups on the surface.

It has been established that crystalline carbon nitride obtained by heat treatment of g-C₃N₄ in molten KCl and LiCl salts exhibits photocatalytic activity in the oxidative esterification of benzaldehyde in methanol and ethanol solutions. The reaction proceeds only in the presence of palladium ions, which are reduced with the alcohols in situ, and acid, which promote benzaldehyde acetalization. A probable mechanism of the photocatalytic process is proposed, which involves the oxidation of acetal by a superoxide ion radical, the subsequent interaction of the formed acetal radical with an oxygen molecule, the formation of a tickle organic peroxide and its fragmentation according to the Russell mechanism with the formation of benzoate.

A new sorbent for the extraction of metal ions has been obtained by immobilization of 1,10-phenanthroline derivatives on the silica surface, which significantly exceeds analogues obtained by adsorption immobilization of 1,10-phenanthroline on the surface in terms of sorption properties. The developed sorbent selectively removes Fe(II) at pH = 1.0; at pH > 4, on the contrary, preferentially adsorbs Fe(III). The sorption kinetic of Fe(II) and Fe(III) ions is described by a pseudo-second-order equation corresponding to their chemisorption on the sorbent surface. The distribution coefficients of Fe(II) ions on the obtained sorbent reach to 10⁴-10⁵ cm³/g, which reveal the prospects of its using for the selective removal of Fe(II) ions from aqueous solutions in the presence of macrocomponents of natural waters, as well as for the determination of Fe(II) and Fe(III) ions in environmental and drinking waters at the maximum permissible level and below.

The samples with titanium implanted on aluminum foil surface (Ti/Al) treated in air at different temperatures (25-500°C) have been studied using atomic force microscopy (AFM), X-ray diffraction, sclerometry, low temperature krypton adsorption. The AFM method data reveal that titanium implantation leads to formation of secondary porous structure, accompanied by a simultaneous increase in the surface area (from 0.004 up to 0.3 m²/g) and mechanical strength of surface layer (from 1.5 up to 3.3 GPa) in comparison with initial aluminum foil. Maximum values of specific surface area (1.3 m²/g) and mechanical strength of surface layer (5.2 GPa) are obtained after treatment of implant at 400 °C, which is associated with the formation of a larger number of mesopores in the surface layer. The prospect of using such a sample as catalysts support is shown.