Formation and pharmacological activity of silicon—chitosan-containing glycerohydrogels obtained by biomimetic mineralization

The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.     

Complex Compounds Based on 1-Isopropenylimidazoles and -pyrazole

With respect to Co²⁺, Ni²⁺, Zn²⁺,Cd²⁺, Cu²⁺, Pd²⁺, and Sn⁴⁺ salts, 1-isopropenyl-substituted imidazole, 2-methylimidazole, and pyrazole behave as monodentate ligands with only one coordination center on the N¹ and N² atoms, respectively; 1-isopropenylpyrazole under complex-formation conditions is dealkylated to form pyrazole complexes. The reaction with HCl leaves the unsaturated substituent in 1-isopropenylimidazole intact and yields corresponding hydrochlorides by the N³ atom of the heterocycle. The least basic 1-isopropenylpyrazole takes up HCl also by the double bond of the alkenyl group.     

Crystal and molecular structures of the complexes of cobalt dichloride with 1-isopropenylimidazole and 1-vinylimidazole

The crystal and molecular structures of bis(1-isopropenylimidazole)dichlorocobalt (C₁₂H₁₆Cl₂·N₄Co) [R 0.036 (R _W 0.089) for 3229 unique reflections with I > 2σ(I)] and tetra(1-vinylimidazole)dichlorocobalt (C₂₀H₂₄Cl₂N₈Co) [R 0.031 (R _W 0.072) for 1863 unique reflections with I > 2σ(I)] were determined. In these molecular complexes, the monodentate terminal 1-alkenylimidazole ligands coordinate to the metal via a “pyridine” nitrogen atom. In C₁₂H₁₆Cl₂N₄Co, the Co atom has a distorted tetrahedral 2N,2Cl coordination. The coordination polyhedron of cobalt in C₂₀H₂₄Cl₂N₈Co is a strongly elongated 4N,2Cl octahedron. The Co-N and Co-Cl bonds [Co-N 2.015(2) and 2.032(4) Å; Co-Cl 2.229(2) Å] in the tetrahedral complex C₁₂H₁₆Cl₂N₄Co are shorter than those in the octahedral complex C₂₀H₂₄Cl₂N₈Co [Co-N 2.134(2) and 2.157(2) Å; Co-Cl 2.518(1) Å]. In the structures of both complexes there are short contacts involving the Cl atoms.     

Reactions of 1-Allenylpyrazole and 1-Allenyl-1,2,4-triazole with Hydrogen Chloride and Metal Chlorides

1-Allenylpyrazole and 1-allenyl-1,2,4-triazole react with hydrogen chloride via proton addition at the pyridine-like nitrogen atom (N² and N⁴, respectively). In the reaction with 1-allenylpyrazole, 1-[(E)-3-chloro-1-propenyl]pyrazole is also formed via regio- and stereoselective addition of hydrogen chloride to the propadienyl group. 1-Allenylpyrazole and 1-allenyl-1,2,4-triazole act as unidentate ligands with respect to Co, Ni, Cu, Zn, Cd, Pd, and Sn, the donor centers being N² and N⁴, respectively. Apart from mononuclear coordination compounds, 1-allenylpyrazole gives rise to polymeric complexes which contain units and blocks formed by the free ligand.     

Selective methanation of CO in the presence of CO<Subscript>2</Subscript> in hydrogen-containing mixtures on nickel catalysts

The screening of commercial nickel catalysts for methanation and a series of nickel catalysts supported on CeO₂, γ-Al₂O₃, and ZrO₂ in the reaction of selective CO methanation in the presence of CO₂ in hydrogen-containing mixtures (1.5 vol % CO, 20 vol % CO₂, 10 vol % H₂O, and the balance H₂) was performed at the flow rate WHSV = 26000 cm³ (g Cat)⁻¹ h⁻¹. It was found that commercial catalytic systems like NKM-2A and NKM-4A (NIAP-07-02) were insufficiently effective for the selective removal of CO to a level of <100 ppm. The most promising catalyst is 2 wt % Ni/CeO₂. This catalyst decreased the concentration of CO from 1.5 vol % to 100 ppm in the presence of 20 vol % CO₂ in the temperature range of 280–360°C at a selectivity of >40%, and it retained its activity even after contact with air. The minimum outlet CO concentration of 10 ppm at 80% selectivity on a 2 wt % Ni/CeO₂ catalyst was reached at a temperature of 300°C.     

Specifics of reactions of cerium sulfate and europium sulfate with hydrogen

Reactions of cerium sulfate and europium sulfate with hydrogen have been studied. Diagrams showing the evolution of phase composition of the polycrystalline products of reaction between europium sulfate and hydrogen are constructed. The reaction of Ce₂(SO₄)₃ with hydrogen at 600°С consecutively yields Ce₂O₂S and Ce₂O₃ phases. At 800°С the batch is >95 mol % Ce2O3. At 480-500°С, a single-phase sample of EuSO4 is prepared; at 600-1000°С, Eu₂O₂S is prepared; and at 1050°С, the batch is >95 mol % Eu₂O₂S and up to 5 mol % Eu₂O₃. Atomic-force microscopy shows that europium sulfate grains, which represent agglomerates of particles 10-20 μm in size, are degraded upon reaction with hydrogen into individual ovalshaped particles sized 40-60 × 130-200 nm.     

Assembling of Complex Heterocyclic Ensembles, Schiff Bases, from 5-Amino-3-[2-(4,5,6,7-tetrahydroindolyl)]pyrazoles and 1-Vinyl(ethyl)-2-formylimidazoles

Condensation of 5-amino-3-(2-pyrrolyl)pyrazoles with 1-vinyl(ethyl)-2-formylimidazoles afforded complex heterocyclic ensembles: Schiff bases containing pyrrole, pyrazole, and imidazole rings. The cis,trans-orientation of CH = N and CH₂ = CH groups and E-isomeric structure of the Schiff bases under study with respect to the imine fragment, and also the presence of intra- and intermolecular hydrogen bonds were established.     

Metal Complexes of 1-Allenylimidazoles

Monomeric complexes ML _n X _m , where M = Co^{2 +}, Ni^{2 +}, Zn^{2 +}, Cd^{2 +}, Cu^{2 +}, Pd^{2 +}, Sn^{4 +}; L = 1-allenylimidazole, 1-allenyl-2-methylimidazole, 1-allenylbenzimidazole; n = 2, 4; m = 1, 2, 4; X = Cl, OCOCH3, was prepared for the first time, and their structure was studied by NMR and IR spectroscopy. In the complexes, 1-allenylimidazoles act as monodentate ligands coordinating via the heteroring ^N3atom, and the CH2 = C = CH group is stabilized by coordination of the azolyl ring with the metal, which hinders elec- tron transfer from the heteroring to the allenyl fragment. The prospective use of the complexes of Zn(OCOCH3)2 with 1-allenyl imidazole derivatives as antidotes and antihypoxants was demonstrated.