Doklady Chemistry最新文献

The presented paper introduces in silico treatment for 34 commercially available pesticides in order to predict new compounds that may act as pesticides based on acetylcholinesterase inhibition. Theoretical treatments using density functional theory, (DFT) and quantitative structure–activity relationship, (QSAR) suggested two statistically significant models for the median lethal dose of Mus musculus, (MLD50) and Homo sapiens, (HLD50). The MLD50 model consisted of only two descriptors including the number of hydrogen bond donor (NHBD) and ovality (OVA) in addition to the correction term (ZOM) with the value of 0.905 for both square correlation coefficient (r²) and cross-validation (q²). The model of HLD50 was only depending on three descriptors including NHBD, OVA, and Wiener index (WI) in addition to ZOM with r² and q² equal to 0.853 and 0.777. The proposed equations showed a physical meaning which could help in understanding the factors affecting the action of pesticides. A special and unique feature was introduced in this study by exploiting both developed models of MLD50 and HLD50 in predicting new more effective pesticides with less toxicity to humans. This new approach was established by the correlation between those models which in turn seven new specific compounds that might be usable as new pesticides were introduced.

The effect of calcium hypophosphite dispersion on the morphology and composition of the products of its oxidation by atmospheric oxygen has been studied by simultaneous thermal analysis (STA), FTIR spectroscopy, and X-ray powder diffraction analysis. It has been found that the factor influencing the heat and mass transfer in the oxidation processes of calcium hypophosphite is the amorphization of the products due to the formation of the glass phase of calcium pyrophosphate Ca₂P₂O₇.

Alkyltriphenylphosphonium nitrates [Ph₃PCH₂С(O)Me]NO₃ (1) and [Ph₃PCH₂CH=CHCH₂PPh₃][NO₃]₂ · 2H₂O (2) have been synthesized by reacting, respectively, acetonyl-triphenylphosphonium and trans-2-butene-1,4-bis(triphenylphosphonium) chlorides with nitric acid. The compounds have been characterized by IR spectroscopy and single-crystal X-ray diffraction. According to XRD data, acetonyltriphenylphosphonium nitrate (1) (C₂₁H₂₀NO₄P, FW = 381.35; monoclinic, space group С2/с; a = 14.301(13) Å, b = 12.756(11) Å, c = 21.40(2) Å; α = 90.00°, β = 90.66(3)°, γ = 90.00°, V = 3904(8) ų, Z = 8; ρ_X = 1.298 g/cm³; GOOF = 1.034; R = 0.0631) and trans-2-butene-1,4-bis(triphenylphosphonium) dinitrate dihydrate (2) (C₄₀H₄₀N₂O₈P₂, FW = 738.68; triclinic, space group P–1; a = 9.259(7) Å, b = 9.514(6) Å, c = 12.247(9) Å; α = 68.43(4)°, β = 72.47(5)°, γ = 84.06(3)°, V = 956.7(12) ų, Z = 1; ρ_X = 1.282 g/cm³; GOOF = 1.029; R = 0.0493) have ionic structure and consists of organyltriphenylphosphonium cations with a somewhat distorted tetrahedral coordination of the phosphorus atom (the CPC angle vary within 104.99(11)°−112.25(12)° for 1 and 107.61(11)°−111.28(11)° for 2; the P–C distances are 1.792(3)–1.802(3) Å and 1.792(2)–1.815(2) Å, respectively) and planar trigonal nitrate anions (the sums of the ONO angles are 359.5° and 360°, respectively). Complete tables of atomic coordinates and bond lengths and angles of nitrates 1 and 2 have been deposited with the Cambridge Crystallographic Data Centre (CCDC 2155176 (1), 2335887 (2); deposit@ccdc.cam.ac.uk; http://www.ccdc.cam.ac.uk).

Multifractal analysis is one of the tools for studying complex systems with a self-similar structure, e.g., disperse polymetallic systems. This paper studied the application of multifractal analysis to describe and evaluate the characteristics of disperse polymetallic systems (Fe–Al–Co, Fe–Al–Cr, Fe–Al–Mo) obtained by galvanic substitution. The study resulted in the identification of important aspects, such as the distribution of fractal dimensions, which allows for a deeper understanding of the mechanisms of formation and development of structures in polymetallic systems. The presented results can be useful for the development of new materials and technologies, as well as for improving existing methods of analysis and quality control of polymetallic systems. It was shown that the spectrum of generalized fractal dimensions of Fe–Al–Co is similar to the spectrum of the Sierpinski dodecahedron—an S-shaped descending curve. The calculated generalized fractal dimension is 1.662, which indicates a lower complexity of the structure of the Fe–Al–Co sample compared to the model Sierpinski dodecahedron. A micrograph of a particle of a synthesized dispersed sample of the Fe–Al–Cr system shows an agglomerated structure of micron sizes, which, in turn, is formed from interconnected spherical formations with a size of 50–200 nm. The spectrum of generalized fractal dimensions of Fe–Al–Cr also represents an S-shaped ascending curve. The generalized fractal dimension in this case is 1.881, which is higher than that of the sample of the disperse Fe–Al–Co system. The results obtained showed that the multifractal spectrum and the distribution of fractal dimensions can serve as tools for analyzing the mechanisms of formation and evolution of the structure of polymetallic systems. This opens new opportunities for the development of innovative materials with specified properties and the improvement of existing technologies and quality control of materials.

Reactions of alkyltriphenylphosphonium bromides with 2,4-dinitrobenzenesulfonic acid in water lead to the formation of ionic alkyltriphenylphosphonium 2,4-dinitrobenzenesulfonates [Ph₃PAlk][OSO₂C₆H₃(NO₂)₂-2,4] (Alk = cyclo-C₃H₅ (1), (CH₂)₂OH (2), CH₂OH (3), and CH₂С(O)Me (4). Crystals of 1 (C₂₇H₂₃N₂O₇PS, FW 550.50; monoclinic system, space group P-1; unit cell parameters: a = 9.354(11) Å, b = 9.764(10) Å, c = 15.416(17) Å; α = 106.29(4)°, β = 94.67(5)°, γ = 97.98)6)°, V = 1328(3) ų, Z = 2; ρ_X = 1.377 g/cm³), 2 (C₂₆H₂₃N₂O₈PS, FW 554.49; monoclinic system, space group P2₁/c; unit cell parameters: a = 13.049(7) Å, b = 14.816(10) Å, c = 13.261(7) Å; α = 90.00°, β = 93.901(15)°, γ = 90.00°, V = 2558(2) ų, Z = 4; ρ_X = 1.440 g/cm³), 3 (C₂₅H₂₁N₂O₈PS, M 540.47; triclinic system, space group P-1; unit cell parameters: a = 9.086(14) Å, b = 10.95(2) Å, c = 13.17(2) Å; α = 86.20(9)°, β = 71.93(6)°, γ = 89.51(11)°, V = 1243(4) ų, Z = 2; ρ_X = 1.444 g/cm³), and 4 (C₂₇H₂₃N₂O₈PS, FW 566.50; triclinic system, space group P-1; unit cell parameters: a = 9.746(10) Å, b = 11.371(11) Å, c = 13.657(10) Å; α = 66.78(3)°, β = 86.30(3)°, γ = 74.46(5)°, V = 1339(2) ų, Z = 2; ρ_X = 1.405 g/cm³). According to X-ray diffraction data, the phosphorus atoms in cations 1–4 have a distorted tetrahedral coordination, while the sulfonate anions have a normal geometry with a tetrahedral sulfur atom. The P–C bond lengths vary in the range 1.768(3)−1.830(3) Å; the CPC bond angles are within 105.54(9)°−112.42(9)°. In the arenesulfonate anions of the complexes, the S–C distances are close to each other (1.794(2)–1.807(3) Å), and the S–O bond lengths are similar (1.363(4)–1.495(4) Å). The structural organization in complexes 1–4 is mainly due to weak intermolecular contacts of the O···H type 2.31–2.71 Å (1), 2.35–2.64 Å (2), 2.38–2.70 Å (3), and 2.24–2.90 Å (4).

The dependence of thermophysical and thermomechanical properties of the coating on the average molecular weight and molecular weight distribution of polyvinyl acetate was studied by the example of an intumescent fire-retardant composite containing the ammonium polyphosphate–pentaerythritol–melamine–titanium dioxide system and homopolymer PVA as a binder. It was found that, for homopolymer PVA, there is an optimal value of the average molecular weight, at which the maximum fire protection efficiency of the studied fire-retardant coating is achieved at optimal values of its thermal expansion ratio.

The article provides an overview of the methods for producing silicon dioxide. Attention is focused on the most relevant method, sol–gel synthesis. The influence of reagents, the hydrogen index of the medium, the solvent, and other parameters on the properties of silicon dioxide is described. It is concluded that this method has advantages over other methods of production due to multiple parameter control, but there are subtleties of synthesis that require further study.

An effective method of fire protection of metal structures is coating with intumescent fire-retardant materials, among which two-component systems based on epoxy binders are widely used. A notable disadvantage of such systems is their flammability, which can cause a decrease in the fire protection efficiency of coating. One of the methods for reducing flammability is the introduction of fire-retardant functional groups into the polymer structure, in particular, halogen-containing fragments, which can affect the nature of thermal destruction of the material and increase its fire-retardant efficiency. The paper investigates the relationship between the chlorine content in the binder, which is a mixture of chlorine-containing epoxy resin and halogen-free resin in various ratios, and material properties such as flammability, fire-retardant efficiency, adhesion to a steel substrate, and thermal expansion degree, as well as the nature of decomposition under heat treatment.

Quantum-chemical calculations of the acidity indices of Cu(II) aqua ions were performed using the B3LYP, PBE0, and ω-B97XD functionals in combination with the 6-311++G(d,p), aug-cc-pVDZ, and def2-TZVP atomic basis sets. In the molecular-continuum model, the Cu(H₂O)(_{{18}}^{{2 + }}) aqua complex (six H₂O molecules in the first and 12 molecules in the second hydration sphere) was taken to be the reference Cu(II) aqua ion. Its interaction with the dielectric environment in the solution was considered in the polarized continuum model. In the initial aqua complex, protons were sequentially removed, and the resulting Cu(II) aquahydroxo complexes were subjected to full geometry optimization. The Gibbs free energies of ionization processes were calculated as the difference between the total Gibbs energies of the reaction products and the initial reagents. Free energies for intermediate aquahydroxo complexes were obtained from thermochemical analysis, and for the proton in an aqueous solution ({text{H}}_{{({text{aq}})}}^{ + }), the free energy was calculated by a special approach using the experimental Gibbs energy of hydration. Analysis of the calculation results showed that the B3LYP/aug-cc-pVDZ and ω-B97XD/aug-cc-pVDZ combinations provided a satisfactory agreement with the experimental values for all four stages of ionization (hydrolysis) of Cu(II) aqua ions. Therefore, it can be concluded that these combinations of the density functional theory level and the atomic basis set can be recommended for calculating the formation constants of Cu(II) complexes in aqueous solutions. Along with this, it is noted that for the first stage of ionization of the Cu(II) aqua ion, from which the primary reconstruction of the aqua complex begins, satisfactory pK_a1 values are achieved at almost all calculation levels. Therefore, other calculation levels used may also prove satisfactory for calculating the formation constants of Cu(II) complexes in aqueous solutions.

This study presents a green and efficient method utilizing BiFe_0.9Zn_0.1O₃ (zinc-substituted bismuth ferrite) nanoparticles as a reusable catalyst for the chemoselective reduction of aromatic nitro compounds. Employing ethanol as the reaction medium at ambient temperature, the protocol facilitates the selective conversion of nitro groups to amino groups, even in the presence of other reducible functional groups such as halo, alkoxy, carbonyl, and cyanide. This approach consistently yields the desired products with exceptional selectivity and quantitative yields approaching 100%. Furthermore, the catalyst’s magnetic properties enable straightforward recovery and reuse, making this a sustainable and highly efficient strategy for industrial and synthetic applications.