Vol 59, No 7 (2018)

The electronic structure of lithium metaborate in monoclinic and tetragonal phases is studied using the density functional theory (DFT) method. The band spectra, total and partial densities of states are calculated for both modifications. Deformation electron density maps in LiBO₂ crystals are obtained. Participation of oxygen atoms in chemical bonding due to trigonal BO₃ and tetragonal BO₄ groups in monoclinic and tetragonal phases, respectively, is studied.

Three molecular adducts of the antituberculosis drug isoniazid (INH) are synthesized with γ-resorcylic acid (γRA), phloroglucinol (PG), and gallic acid (GA). The new solid phases are preliminarily characterized by the thermal analysis (DSC/TGA) and powder X-ray diffraction. The formation of new solid phases is confirmed by single crystal X-ray diffraction, infrared (FT-IR) and Raman spectroscopy. All three new solid crystalline forms are stabilized by various hydrogen bonding interactions such as N⁺···H–O^–, N···H–O, O···H–O, and π–π stacking. The FT-IR analysis puts forward that the solid form of INH1 is a salt whereas the INH2 and INH3 molecular complexes are cocrystals. We have also investigated the density of states (DOS), band structure, and atomic orbit projected density of state (PDOS) of title compounds by adopting the density functional theory (DFT) technique in the local density approximation (LDA). The electronic structure calculations show that energy states are delocalized in the k-space due the hydrogen and covalent bonds in the crystals. The frontier molecular orbital (FMO) analysis reveals that charge transfer takes place within the compounds. The Hirshfeld analysis shows that H–H and N⋯H–O hydrogen bonding interactions are dominant in all three molecular adducts of INH.

The 3D QSAR analysis using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques is performed on novel nalidixic acid based 1,2,4-triazole derivatives suggested earlier as antibacterial agents. The CoMFA and CoMSIA models employed for a training set of 28 compounds gives reliable values of Q² (0.53 and 0.52, respectively) and R² (0.79 and 0.85, respectively). The contour maps produced by the CoMFA and CoMSIA models are used to determine a three-dimensional quantitative structure-activity relationship. Based on the 3D QSAR contours new molecules with high predicted activities are designed. In addition, surflex-docking is performed to confirm the stability of predicted molecules in the receptor.

Human African trypanosomiasis (HAT) is a neglected tropical disease, and some drugs treating HAT have been used for even more than 60 years. Currently, a series of benzyl phenyl ether diamidine derivatives are discovered, which exhibit high antiprotozoal activities and low cytotoxicity, leading to good development prospects. The comparative molecular field analysis (CoMFA) and the comparative molecular similarity indices analysis (CoMSIA) are used to study the relationship between the structure and antiprotozoal activities. The established 3D QSAR model shows not only significant statistical quality, but also satisfies predictive ability: the best CoMFA model had r² = 0.958 and q² = 0.766, the best CoMSIA model had r² = 0.957 and q² = 0.812, the predictive ability of CoMFA and CoMSIA model were further confirmed by a test set which had 11 compounds, giving the correlation coefficient Q_ext² of 0.792, 0.873, respectively. The contour maps and contribution maps show important features that can improve the antiprotozoal activity: position 3 from substituent R4 should be a low electronegativity group, position 4 from substituent R₄ should have higher electronegativity, substituent R₂ should be selected to a low electronegativity and small bulk group. Together these results may offer some useful theoretical information in designing potential inhibitors.

According to X-ray diffraction data, crystalline 3-(benzoxazol-2-ylthio)-3-phenyl-2-propenonitrile is a substantially nonplanar Z-isomer. The resulting single crystal has layered structure as a result of π–π stacking. ¹H NMR data testify small amounts of E-isomer in the samples dissolved in chloroform.

Following our previous work, we synthesized N-(7-methyl-5,6-diphenyl-2-m-tolyl-7H-pyrrolo[2,3-d]pyrimidin-4-yl)benzensulfonamides to study the sulfonylimine-sulfonamide tautomerism. This goal is performed using the density functional theory (DFT). Four plausible isomers including the keto and enol sulfonamide as well as Z and E sulfonimide are considered for each of compounds. The DFT calculations are carried out at the B3LYP/6-31+G(d,p) level of theory. The optimized geometric parameters such as bond lengths and bond angles are calculated. The computed IR vibrational frequencies and ¹H NMR chemical shifts are in good agreement with the experimental data. The structure of all compounds is confirmed on the basis of their full spectral data. In all three compounds, the Z-sulfonimide form is more stable than the other isomers. A high energy gap between the frontier orbitals confirms the stability of the compounds.

Binuclear centrosymmetric copper(II) complex of the formula bipyCu(L)₄Cubipy, where bipy = 2,2′- bipyridine and L = 4-methoxy-2-phenyl acetate, is synthesized and characterized by FT-IR, UV-Visible, ESR and mass spectroscopy, electrochemical, thermogravimetric, and single crystal XRD techniques. The complex contains two differently oriented molecules per unit cell stabilized via intermolecular interactions. Geometry around each Cu(II) was found to be square pyramidal affected by asymmetrically bridging oxygen atoms occupying the apical position of one square pyramid and the axial position of another in the same binuclear molecule. The square base is formed by two oxygen atoms from two carboxylate ligands and two nitrogen atoms from the bipyridine moiety. TGA shows that the complex is stable up to 170 °C followed by stepwise loss of coordinated ligands, which was supported by GC-MS data as well. A broad absorption spectrum indicated ²B_1g as the ground state and single electron occupancy of the dx²–y² orbital, which was confirmed by the ESR spectrum. The electrochemical study gives two oxidation curves corresponding to Cu(II)/Cu(III) and Cu(I)/Cu(II) and a reduction signal corresponding to the Cu(II)/Cu(I) process. The robust complex represents an interesting contribution to the understanding of coordination chemistry.

Manganese-gallium samples with cation ratios Mn:Ga = 1:2, 1.5:1.5, and 2:1 are synthesized by coprecipitation with subsequent annealing in air in a temperature range 600–1200 °C. Powder XRD, TEM, and BET methods are used to study the physicochemical characteristics of the samples. It is found that in the air at the annealing temperature of 600 °C finely dispersed low-temperature Mn_3–xGa_xO₄ spinels primarily form in all series, but in the whole temperature range (600–1200 °C) the system is multiphase. Annealing at 800–1200 °C leads to an increase in the concentration of simple oxides (β-Mn₃O₄ and β-Ga₂O₃). Only simple α-Mn₂O₃ and β-Ga₂O₃ oxides exist in a Mn:Ga = 2:1 series at 800 °C. In the sample with a cation ratio Mn:Ga = 1.5:1.5 annealed in air at 1000 °C, the formation of a superstructure based on the spinel structure is found.

The crystallographic analysis of the orthorhombic (Pnma) structure of Sr₃B₂SiO₈ ≈ (Sr(B,Si)O_2.67) shows that its experimentally found symmetry is determined by the geometry of the Sr sublattice where the anion radical without this symmetry simulates it by the statistical averaging of four variants of real configurations. With a reduced fraction of heavy atoms in the triclinic (Р1) structure of Ba₃B₆Si₂O₁₆, the Ba and Si cations whose sublattice determines the presence of additional pseudosymmetry form the skeleton of the structure.

The molecular and crystal structures of 1-(4-fluorophenyl)-1,4-dihydro-1H-tetrazole-5-thione (I) and its complex with cadmium(II) (II) are studied by single crystal XRD. Free ligand I is thione; it has a nonplanar structure (the torsion angle between the tetrazole and benzene rings is 54.99(7)°) and forms H-bonded centrosymmetric dimers via two N–H…S hydrogen bonds in the crystal. The dimers contain a central planar eight-membered {S=C–N–H…S=C–N–H…} ring. Complex II has a chain structure with the composition [(C₇H₄N₄FS)₂Cd]_n. The environment of the Cd(II) atom consists of two nitrogen atoms and two sulfur atoms from four ligands I and represents a distorted tetrahedron. When complex II forms, ligand I converts into the thiol form. Infinite 1D chains contain eight-membered {←S=C–N–Cd←S=C–N–Cd} rings in a chair conformation. The chains in the crystal are arranged in layers parallel to the (101) plane due to secondary intermolecular F…F and π–π-stacking interactions.

We have previously reported the synthesis, structure and urease inhibitory activity of a complex [Cu₂(L)₄DMSO₂]·2DMSO (HL = (E)-3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)acrylic acid), and we found the complex to show a strong inhibitory activity against jack bean urease [1]. In this study, the interaction of the complex and urease is studied by fluorescence spectroscopy. We find that the fluorescence quenching mechanism of the complex with urease is static quenching. The quenching rate constant (K_q) is 1.6·10¹² l/mol·s^–1, the quenching constant (K_sv) is 1.6×10⁴ l/mol, the association binding constant (K) is 3.55·10⁴ l/mol, and the binding site number (n) is 1.22.

A zinc coordination polymer with the formula {[Zn(npa)(L¹)]·2H₂O}_n (1) (L¹ = bis(4-(1H-imidazol-1-yl)phenyl)methanone, H₂npa = 4-nitrophthalic acid) is synthesized and characterized by IR, elemental analysis, and single crystal X-ray diffraction. The Zn²⁺ ion has a distorted tetrahedral environment with two O atoms from two npa ligands and two N atoms from two L¹ ligands. Each L¹ acts as a bridging ligand to link the neighboring [Zn(npa)]₂ dimers to form a 1D ladder.

A review of current works on XANES spectroscopy applied for the determination of parameters of a threedimensional local atomic structure of nanostructured materials is given. Special attention is paid to a new method based on the theoretical analysis of XANES spectra by means of multivariate interpolation. The uniqueness of the technique consists not only in the highly accurate (up to 0.01 Å) determination of interatomic distances in materials without a long-range order in the atomic arrangement but also the estimation of the angular distribution of atoms (i.e. chemical bond angles) in any condensed materials. Several types of nanostructured materials, including coordination compounds, semiconductor quantum dots, nanosized structures in quasicrystals and extraterrestrial materials are given as examples.

The data on the dynamics of structural changes in the composite cathode material based on iron(III) fluoride studied by the operando synchrotron X-ray spectroscopy and diffraction combined with the density functional theory (DFT) are reported. Based on the FeF₃ structure determined by X-ray crystallography the crystal structure of Li_xFeF₃ for 0 < x < 0.5 is modeled by the geometry optimization. The crystal structure models for 0.5 < x < 1 are predicted using the evolutionary algorithms. The Fe K-edge X-ray absorption spectra are calculated for these models and compared with the experimental data.

In this work, we report the synthesis, characterization, and catalytic evaluation of Ni–Cu–Zn ferrite using tragacanth gum as a biotemplate and metal nitrates as the metal source by the sol-gel method without using any organic chemicals. The sample is characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The powder XRD analysis reveals the formation of cubic-phase ferrite MNPs with an average particle size of 20 nm. The magnetic analysis reveals that the Ni–Cu–Zn ferrite nanoparticles have ferromagnetic behavior at room temperature with a saturation magnetization of 52.76 emu/g. The catalytic activity of Ni–Cu–Zn ferrite MNPs is evaluated for the synthesis of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazatetracyclo [5.5.0.05,9.03,11]dodecane (HBIW) under ultrasonic irradiation. Mild reaction conditions, short reaction times, the use of an economically convenient catalyst, and excellent product yields are the advantageous features of this method. The catalyst could be easily recycled and reused few times without a noticeable decrease in the catalytic activity.

The worldwide energy demand is expected to be double of the current consumption in the near future. This huge energy demand increases the importance of energy conversion and storage devices. A fuel cell needs an electrolyte which can be used under high temperature conditions for increasing the system efficiency. In the case of rechargeable batteries, the ion-conducting properties of the electrolyte should possess long-term sustainability. However, available electrolytes for a fuel cell can efficiently work only at temperatures below 100 °C. On the other hand, commercially used electrolytes are usually liquids and may cause serious leakage and safety problems, thus their sustainability is limited for Li-ion battery applications. Although their ionic conductivities are relatively low, solid and gel type electrolytes are safer and therefore become more favorable. More recently, compatible hybrid organic-inorganic polyhedral oligomeric silsesquioxane (POSS) derivatives have attracted much attention of researchers in order to obtain solid or gel type electrolytes. These materials combine the intrinsic mechanical and thermal properties owing to the inorganic core and the compatibility owing to the organic coronae. Therefore POSS derivatives are a promising family that can allow the design of alternative energetic materials. Here, the objective is to increase the awareness of the role of POSS-based materials for fuel cell and rechargeable battery applications.

In the original publication the name of one of the authors had been misspelled. The correct name is T. Saemian.