Journal of Structural Chemistry最新文献

4-Acetyl-N,N,N-trimethylanilinium iodide (1) is obtained by the N-alkylation reaction of 4-((trimethylsilyl) ethynyl)aniline. The structure of compound 1 is solved using the single crystal X-ray diffraction analysis for the first time. 4-Acetyl-N,N,N-trimethylanilinium iodide has the layered packing. The layers, in which cations and anions alternate, are parallel to each other. In the IR spectrum of compound 1, absorption bands at 1676 cm^–1, 2949 cm^–1, and 3021 cm^–1 correspond to C=O and C–H stretching vibrations (aliphatic and aromatic). Compound 1 decomposes in two distinct steps. At the first step (172-200 °C), 4-acetyl-N,N,N-trimethylanilinium iodide decomposes with a removal of methyl iodide (i.e., inverse methylation reaction). At the second step (200-285 °C), 1-(4-(dimethylamino)phenyl)ethanon formed evaporates. Judging by the absence of the carbon residue, evaporation proceeds without decomposition.

The structure of trans,trans-[Pt(py)₂(N₃)₂(OH)₂]·2H₂O is studied by single crystal X-ray diffraction. The crystallographic data are: a = 9.8240(2) Å, b = 17.2178(3) Å, c = 9.5248(2) Å, β = 97.777(1)°, space group P2₁/c, Z = 4, ρ_cal = 2.11 g/cm³. The crystal structure of the complex consists of molecular layers perpendicular to the c direction. The transformation process of the dehydrate to the anhydrous complex is analyzed by thermal gravimetry. The previously published synthesis procedures of trans,trans-[Pt(py)₂(N₃)₂(OH)(SuccH)] and trans,trans-[Pt(py)₂(N₃)₂(OH)(Succ-NH-TEMPO)] complexes from trans,trans-[Pt(py)₂(N₃)₂(OH)₂] are modified. The optimization of synthesis conditions and the product isolation procedure increases the product yield and substantially improves the purity of the obtained compounds.

IR spectroscopy and quantum chemical methods are applied to study the compositions, structures, and energy parameters of acid-basic complexes formed in three-component solutions of 3,5-dimethylpyrazole (DMP)–trifluoroacetic acid (TFAA)–N,N-dimethylformamide (DMF) at DMP:TFAA molar ratios of 1:1 and 1:2. The DMP·TFAA·DMF trimer is found to be the structure-forming fragment in the 1:1:1 solution, and in 1:1:≥2 solutions, it is the DMP·TFAA·2DMF tetramer. Both complexes have the cyclic structures and contain quasi-ionic pairs in which protons of TFAA molecules move away from them but do not transfer to DMP molecules. Cyclic tetramer DMP·2TFAA·DMF with alternating acid and base molecules is the structure-forming fragment in the DMP–TFAA–DMF triple system with DMP:TFAA = 1:2 in the entire concentration range. It consists of two quasi-ionic pairs with O⋯H⋯O and N⋯H⋯O hydrogen bridges (the TFAA molecule proton passes to the DMP molecule in it). The obtained results can be used to predict the catalytic activity of multicomponent acid solutions.

Fine crystal samples of terbium oxide C-Tb₂O₃ (space group (Iabar{3}), Z = 16) are grown from the solution-melt, which are differently colored - colorless and pale brown. No significant differences are revealed by the single crystal X-ray diffraction analysis. The unit cell parameters are refined using the external standard at T = 300 K with relative error Δa/a = 2·10^–5. Values a = 10.7302(2) Å and 10.7296(2) Å are obtained for the colorless sample and the pale brown one respectively. Dependence a(T) is studied in the range of 90-490 K for the colorless crystal. Experimental points are described by the polynomial: a = 10.716 + 2.7· ·10^–5T + 7.2·10^–8T².

New platinum(II) acetylacetonate and lead(II) hexafluoroacetylacetonate heterometallic complexes, [(Pt(acac)₂)₅(Pb(hfac)₂)₄] (1) and [Pt(acac)₂Pb(hfac)₂] (2), are prepared and characterized. Crystal data for 1: a = 13.8795(6) Å, b = 15.0201(6) Å, c = 17.2442(7) Å, α = 105.6503(14)°, β = 110.7887(14)°, γ = 99.0552(14)°, (Pbar{1}) space group, Z = 4, d_calc = 2.380 g/cm³; for 2 a = 16.810(6) Å, b = 30.960(12) Å, c = 18.260(7) Å, β = 105.19(2)°, C2/c space group, Z = 16, d_calc = 2.204 g/cm³. The main structural motifs of these compounds are same-type 1D coordination polymers stabilized by Pt⋯Pt and Pb–O contacts.

The structure of a new phase of a volatile Pt(ktf)₂ complex, where ktf = CF₃–C(O)–CH–C(NH)–CH₃, is determined by single crystal X-ray diffraction. The crystallographic data for C₁₀H₁₀F₆N₂O₂Pt are as follows: a = 12.1716(7) Å, b = 8.5581(7) Å, c = 19.9966(15) Å, β = 96.840(3)°, space group P2₁/c, Z = 6, R = 0.046. The compound is a 2:1 mixture of cis- and trans-isomers. The square environment of the platinum atom consists of oxygen and nitrogen atoms of two bidentately bonded ketoiminate ligands, resulting in the PtO₂N₂ coordination core. The difference in Pt–O (2.005 Å) and Pt–N (1.990 Å) bond lengths is 0.015 Å in the trans-isomer; the O–Pt–N chelate angle is 93.6°. In the cis-isomer, the average Pt–O and Pt–N bond lengths are 2.002 Å and 1.967 Å respectively; the chelate angle is 94.8°. The molecules are packed into infinite stacks with Pt⋯Pt distances of 4.096 Å and 4.159 Å.

Due to its unique electronic and optical properties, ternary indium–gallium–zinc oxide (IGZO) is applied in flexible and transparent electronics, including in particular thin-film transistors. The IGZO physical properties depend on the synthesis conditions and the ratio of its main constituents (indium, gallium, zinc, and oxygen) and various dopants. A method to synthesize samples of the In_1–2xGaSn_xZn_1+xO₄ series (x = 0.05, 0.10, 0.15) by nitrate-organic gel combustion is described. In this approach, the synthesis can be carried out in a shorter time and at lower temperatures compared to alternative methods reported in the literature. The resulting samples are studied by powder X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The homogeneity of the samples is proved at x = 0.05 and 0.10.

The 3D structure of proteins and protein–ligand complexes is determined by protein crystallography methods. In order to make the protein precipitate and prepare a complex, additional substances, including cosolvents, are added to the solution during the crystallization. However the presence of such additives can affect the structure of the protein and/or the complex, so that the XRD result will differ markedly from the structure of the complex in water and in physiological conditions. In the present study, we verify the presence of such influence on the example of a dimer of the SARS-Cov-2 main protease and a ligand exhibiting activity against SARS-CoV-2. An MD simulation of the complex in water and in 5% and 10% solutions of DMSO and dioxane in water is presented. It is shown that changes in the environment do not affect the structure of the protease dimer, but do significantly affect the interaction of the protein with the ligand. The sites of stable ligand bonding depend on the specific environment the complex is placed in. Thus, protein crystallography data should be treated very carefully: results obtained for one medium will not be necessarily true for another medium of a different composition.

Slow evaporation of a solution of 5,6-dicyano[1,2,5]selenodiazolo[3,4-b]pyrazine (1) and 18-crown-6 (2) in tetrahydrofuran (THF) yields the 1₄·2₃ THF₂ (3) molecular crystal complex. The composition of 3 differs from the 1:1 stoichiometry typical for molecular complexes of 1,2,5-chalcogenadyazole derivatives with crown ethers. The structure of 3 is determined by single crystal X-Ray diffraction. The crystal packing of 3 is formed by π-stacking interactions between the molecules of 1 and by strongly shortened Se⋯O contacts between the molecules of 1 and 2. The Se⋯O contacts meet the geometric criteria of chalcogen bonding.

Two salts of 1,4-diazabicyclo[2.2.2]octane (dabco) are synthesized. The first is dabco diacetylenedisalicylate (1) and is characterized by the formation of 1D triple helices. In them, doubly protonated dabco cations link diacetylene disalicylate anions into zigzag-like helices by hydrogen and ionic bonds, and water molecules combine these three single chains into triple ones via hydrogen bonds formed. Rigid anions are drastically bent in the structure of 1 because of skirting around bulky dabco cations. The structure of the second salt (dabco nitrate (2)) contains hydrogen bonds between single protonated dabco molecules and nitrate anions. The second nitrogen atom is not protonated, obtained nitrate is single-substituted basic dabco salt, and a network of hydrogen bonds is absent in it. The ion packing of 2 can be described by a model of 0D ion pairs rather than the space ionic lattice.