Journal of Structural Chemistry最新文献

The shape of ions of quaternary ammonium bases should be known to correctly interpret the properties of their salts; however, there is almost no available numerical data on geometric parameters of their molecules. We report ab initio (HF/6-31G) calculation data on the structure of an all-atom model of the cluster containing one ion pair of tetrabutylammonium bromide TBA⁺Br^– in a vacuum and in a water environment. The same calculations are performed for its neutral structural analogue tetrabutylmethane (TBM). The following geometric parameters are reported: distances from the central atom to the terminal carbon and hydrogen atoms; distances between terminal atoms; excess charges on hydrogen atoms and angles between atoms characterizing the structure; volumes of structures approximating real species; average numbers and lengths of hydrogen bonds in water molecules depending on the distance to the central atom of the species. It is shown that the determined shapes correspond to irregular tetrahedra with densely packed hydrocarbon radicals. The shape and size of TBA⁺ and TBM are almost identical and do not depend on the environment or the electric charge on the central atom.

The effect of fluorination of boron nitride fullerene B₁₂N₁₂ on its activity towards the favipiravir molecule (a drug against the COVID-19 virus) is studied by the density functional theory. Two types of fullerene fluorination are considered: external doping with the formation of the B₁₂N₁₂F₂ structure and endohedral doping with the formation of the F^–@B₁₂N₁₂ complex. It is shown that fluorinated clusters can attach favipiravir by the same mechanism as initial fullerene. It is found that the interaction between the drug and the endohedral complex is too weak, while external doping by fluorine increases the binding energy between the cluster and the drug.

We report a two-step synthesis of benzyl diffractate ethers through the preparation of intermediate benzyl diffractate ethers with an alkyl substituent containing a terminal bromine atom. A series of new diffractaic acid based ethers are synthesized by replacing the bromine atom with various N- and S-nucleophiles. It is shown that benzyl diffractate derivatives exhibit pronounced antiviral in vitro activity against the strain A2 respiratory syncytial virus in a low micromolar concentration range. The dependence of the antiviral activity and cytotoxicity on the compound structure is determined. The analysis of biological activity data revealed two compounds of the active antiviral agents category with the selectivity indices 11.0 and 31.3.

A universal technique is described for producing nanostructured indium, gallium, and zinc oxides by the sol-gel method from respective metal nitrates with ethylene glycol as a complexing agent. The powder X-ray diffraction analysis of the samples obtained evidences that they do not contain noticeable concentrations of impurities, and their unit cell parameters are typical of these compounds. The microstructures of the samples are studied by electron microscopy. The band gap is determined based on diffuse reflectance of the samples using the Kubelka–Munk method, and it is shown that its boundaries correspond to the available literature data.

The [Ni(L1)₂(H₂O)₂](BF₄)₂(1-H₂O) and [Ni(L2)₂](BF₄)₂ (2) bis-chelate nickel(II) complexes based on 1,5-N,O-ligands, namely, (diisopropyl(pyridin-2-ylmethyl)phosphine oxide L1 and diisopropyl(quinolin-2-ylmethyl)phosphine oxide L2) are prepared. The structure and composition of 1-H₂O and 2 are confirmed by mass spectroscopy, IR spectroscopy, thermogravimetric analysis, and elemental analysis. The compounds dissociate in solutions so that aqualigands in 1-H₂O are replaced by acetonitrile to form the [Ni(L1)₂(CH₃CN)₂](BF₄)₂(1-CH₃CN) complex and phosphine oxide ligands in 2 are replaced by six water molecules to form the [Ni₂(L2)₄(H₂O)₁₂](BF₄)₂ hydrogen-bonded hexaaquanickel(II) agglomerate (3). The structure of 1-H₂O, 1-CH₃CN, and 3 in crystals are determined by XRD. Cytotoxic properties of the synthesized nickel(II) complexes against M-HeLa and HuTu80 cancer cells and normal Chang Liver cell lines are studied.

The dependence of unit cell parameters (UCPs) of LnCrO₃ (Ln = La–Lu, Y) orthochromites on effective ionic radii of Ln³⁺ cations is analyzed. It is shown that these dependences can be described by the following equations: (a = {69}.{831}R_{text{Ln}}^{3}-{223}.{91}R_{text{Ln}}^{2}text{+} {238}.{76}{{R}_{text{Ln}}}-{79}.{162}) Å; b = 1.5893R_Ln + 5.9242 Å, c = 1.8469 R_Ln + 3.3691 Å, and V = 121.85R_Ln + 93.97 Å³, where R_Ln is the effective ionic radius of the Ln³⁺ cation with a confidence probability of 0.775, 0.989, 0.998, and 0.990, respectively. The obtained equations can be use in a priory calculations of the UCPs of isovalent solid substitution solutions of REE orthochromites (including high-entropy ones) using average effective radii of substituted Ln³⁺ cations. The tolerance factors of REE-, bismuth-, thallium-, and indium orthochromites are calculated. The possibility that an orthorhombic perovskite structure can be formed by the interaction of REE orthochromites with non-isostructural BiCrO₃ and ScCrO₃ chromites is considered.

Ethyl-2-amino-1-(hetarylamido)-4-oxo-5-(2-oxo-2-phenylethylidene)-4,5-dihydro-1H-pyrrole-3-carboxylates are synthesized, their antiradical and antioxidant activities are studied, and the quantum chemical calculations are performed. The nitrogen atom position in the pyridine moiety of the derivatives is found to change the toxicity of synthesized compounds and to affect the ability to bind free radicals. The results can facilitate the further determination of the structure – activity relationship in the considered types of the biological activity.

Metal-organic coordination polymer {[Zn₇O₂(tr₂btd)₂(1,4-ndc)₆]·2tr₂btd}_n representing an inclusion compound of free ligand molecules in the pores of the 3D framework is synthesized by the interaction of zinc 4,7-di(1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole (tr₂btd) nitrate and 1,4-naphthalene dicarboxylic acid (1,4-H₂ndc). Features of the interaction of guest molecules with the framework are investigated by single crystal X-ray diffraction, IR spectroscopy, and quantum chemical calculations. The study of the luminescent properties of compounds shows a bathochromic shift of the emission maximum that is unusual for coordination polymers with tr₂btd as a linker. Quantum chemical calculations at the density functional theory level reveals charge transfer between the guest molecule and the framework during emission.

We discuss the methodological questions of measuring unit cell parameters of small crystals in Bond’s scheme on a commercial diffractometer equipped with a three-circle goniometer and a 2D detector. The effect of the sample eccentricity on the positions of X-ray diffraction reflections during rotation about φ and ω axes is examined. The approach is developed to eliminate the effect of the sample eccentricity related to rotation about the φ axis by positioning one of the crystallographic directions along the ω axis. The unit cell parameters are measured for the reference Si and Ge single crystals used in this work with relative error Δa/a no worse than 6.5·10^–5.

New complexes of magnesium with asymmetric fluorinated β-diketones are synthesized: pentafluoropropionyl (Hpfpac, 6,6,6,5,5-pentafluorohexane-2,4-dione) and heptafluorobutyrylacetone (Hhfbac, 7,7,7,6,6,5,5-heptafluoroheptane-2,4-dione). The [Mg(H₂O)(EtOH)(pfpac)₂] 1 and [Mg(H₂O)₂(hfbac)₂]·H₂O 2 phases are characterized by a number of methods. The structures of crystals of 1, 2, and [Mg(EtOH)₂(hfbac)₂] 3 are determined by the single crystal X-ray diffraction analysis. Magnesium atoms have a distorted octahedral environment, and neutral ligands are in the trans-position. Molecules are involved in systems of OH⋯O_dik hydrogen bonds, forming layers (2) or chains (1, 3). A relative evaluation shows that 2 is more volatile than 1. Structures of molecules and packing characters are compared with those of a series of related β-diketonate complexes. The effect of an increase in the ligand perfluoroalkyl chain (L = tfac, trifluoroacetylacetonate ion), including isoformular [Mg(H₂O)₂(L)₂]·H₂O, is shown.