Doklady Chemistry最新文献

An approach to designing the structure of Eu²⁺-containing silicate glass-crystalline materials was implemented for the first time, using which a rare-earth activator is introduced into Ba-containing silicates formed during glass crystallization. Eu²⁺-activated fluorine-containing glasses and glass-ceramics in the MgO–BaO–ZrO₂–SiO₂ system were synthesized, and their crystal structure and luminescence properties were studied. It was shown that the simultaneous incorporation of Eu into several different silicate crystals formed during the crystallization of glasses yields a material with a broad luminescence band in the visible part of the spectrum. A study of the luminescence excitation and emission spectra of glass demonstrated the possibility of excitation energy transfer from Eu²⁺ ions to Eu³⁺ ions. The approach proposed for the first time to designing the structure of glass-crystalline materials is quite promising for the further creation of new optical media used in high-power light-emitting diodes.

Mg_3 – nNi_nBPO₇ samples (n = 0–3) were synthesized by gel combustion followed by annealing at 980°C, cooled under inertial-thermal conditions, and then studied by X-ray powder diffraction analysis, IR spectroscopy, and X-ray fluorescence spectrometry. A crystalline phase of Ni₃BPO₇ with the β-Zn₃BPO₇ structure was experimentally obtained for the first time. When varying the composition of the samples from Mg₃BPO₇ to Ni₃BPO₇, in borophosphate, a region of coexistence of α‑Mg₃BPO₇ and β-Ni₃BPO₇ was discovered. Analysis of diffuse reflectance spectra of Mg_1.5Ni_1.5BPO₇ showed the presence of Ni²⁺ cations in an environment different from the symmetrical octahedral or tetrahedral environment.

An efficient approach to the synthesis of (+)-camphor and (–)-fenchone anils has been developed, which involves the reaction of the corresponding bicyclic monoterpenoid ketones with substituted anilines in the presence of in situ prepared (i-PrO)₂Ti(OTf)₂·(i-PrOH)₂ complex, as a homogeneous catalyst, and (i-PrO)₄Ti, as a dehydrating agent. The advantage of the suggested method lies not only in obtaining target products in good yield and high purity, but also in a simplified procedure for their isolation. These products are of interest as potential pharmacologically active compounds, antioxidants for rubber mixtures, and components of 3D-printing formulations.

Here, we report the synthesis of a single-atom alloy Pd₁Ag₆/Al₂O₃ catalyst with an egg-shell distribution of the active component over the catalyst granules for the selective hydrogenation of acetylene traces in ethylene. The formation of an egg-shell structure has been confirmed by electron probe microanalysis, which demonstrates that metals are predominantly localized at a depth of 130–160 µm from the granule surface. Transmission electron microscopy and X-ray photoelectron spectroscopy have provided evidence of the formation of a PdAg substitutional solid solution with electron density transfer from Ag to Pd. The formation of Pd₁ single sites has been confirmed by IR spectra of adsorbed CO. In the selective hydrogenation of acetylene, the synthesized single-atom alloy Pd₁Ag₆/Al₂O₃ with an egg-shell distribution shows high selectivity, which radically exceeds the selectivity of the palladium counterpart.

A number of new derivatives of octahydro-2H-chromene based on monoterpenoid (–)-isopulegol has been synthesized. The composition and structure of the products have been established using NMR spectroscopy, high-resolution mass spectrometry, and X-ray diffraction analysis. It has been shown that the majority of obtained compounds show high analgesic activity in vivo. (4S)‑Diastereomers of morpholinoacetamide derivatives of octahydro-2H-chromene showed the highest efficiency in both tests (acetic acid-induced writhing test and hot plate test).

Effect of temperature on the efficiency of deuterium introduction into a new biologically active compound salicylcarnosine (SC) has been studied. Gaseous deuterium and heavy water were used as deuterium sources. The synthesis of labelled SC by a solid-phase method at 190°C leads to formation of [D]SC in 53% yield and deuterium content about 4.8 atoms per molecule. It has been shown that isotope exchange between SC protons and deuterium water proceeds more efficiently after preliminary treatment of catalyst with gaseous deuterium at ambient temperature. [D]SC forms in 46% yield and contains about 7.3 deuterium atoms per molecule. The preparative synthesis of labelled SC by this procedure at 190°C results in [D]SC yield of 60–70% at deuterium content about 6.2 atoms per molecule. The new procedure for the activation of deuterium inclusion in peptides opens additional opportunities for preparing highly labelled compounds.

Permeable nickel metallic and nickel oxide ceramic materials with nanostructured surface and multilevel hierarchical porosity were created by cyclic redox post-treatment of biporous nickel(II) consolidated in the sintering–dissolution process. Additional levels of intraparticle porosity—Kirkendall pores and shrinkage nanopores—were formed during the stages of high-temperature oxidation in air and reduction in hydrogen, respectively.

A promising strategy in the synthesis of functional compounds with a cage structure is the use of 1,3-dehydroadamantane (tetracyclo[3.3.1.1.^3,7.0.^1,3]decane; 1,3-DHA; bridging [3.3.1]propellane) and its derivatives that are capable of restoring the adamantane structure in their reactions. The review provides information on the methods for the synthesis of 1,3-DHA, spectral characteristics, probable intermediates generated from propellanes, and the advantages of their using: low-stage syntheses of difficult-to synthesize adamantane derivatives, atomic precision, and “green chemistry.” The reactions of 1,3-DHA with a wide range of organic compounds are considered, and its reactivity with respect to CH-, NH-, OH-, and SH-acids, as well as arenes, hydantoins, and heterocyclic compounds, is compared. New chemo- and regioselective methods for the one-step introduction of a 1-adamantyl group into the molecules of various substrates are classified. Particular attention is paid to the reactions of 1,3-DHA with various C–H acids, which enable the easy formation of C–C_Ad bonds to give hard-to-synthesize adamantane derivatives. The influence of pK_a of the substrate on the selectivity of the reactions is demonstrated. Low-step methods for the synthesis of new adamantane derivatives, which have shown high activity as hsEH epoxide hydrolase inhibitors and antitumor agents, are described.

Cesium-promoted cobalt spinel is promising as a catalyst for the low-temperature decomposition of nitrous oxide for use in the second stage of a single-reactor unit for the combined removal of nitrogen oxides. This work studied the effect of the conditions for the preparation of granular and block bulk catalysts based on Co₃O₄ by extrusion molding.