Vol 64, No 7 (2019)

A new rubidium salt, Rb[Cr(C₅H₇NO₄)₂] (C₅H₇NO₄ = mida, methyliminodiacetate), was prepared and its molecular structure was determined from synchrotron X-ray data at 173 K. The complex crystallizes in the space group C2/c of the monoclinic system with four mononuclear formula units in a cell with dimensions a = 16.905(3) Å, b = 6.483(2) Å, c = 13.906(3) Å, and β = 113.95(3)°. The Cr atom is located in a center of symmetry with one independent Cr–N bond length of 2.081(2) Å and two Cr–O bond lengths of 1.9534(18) and 1.9628(18) Å. The Cr(III) ion is coordinated by two N atoms and four O atoms of symmetrical-facial mida ligands, displaying a distorted octahedral geometry. Hirshfeld surface analysis with 2D fingerprint plots revealed that the O···H, H···H, and O···Rb interactions are the main intermolecular interactions. The crystal structure is stabilized by the O···H, H···H, and O···Rb interactions among rubidium cation, the H atoms and the O atoms of carboxylate group from neighboring mida groups.

A new polynuclear silver complex Ag₆(W₂O₅)(Cid)₂ based on citric acid is obtained by hydrothermal method and studied by single crystal X-ray diffraction compound The compound crystallizes in triclinic space group P\(\bar {1}\), Z = 1. The structure solution is complicated by two component non-merohedral twinning. The structure feature is a 3D framework containing 1D infinite [Ag]_∞ chains. Ag atoms are connected by metal–metal bonding interaction with the Ag–Ag distances of 2.849(3)–3.218(2) Å.

2-Chloro-3-((3-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (1) and 2-chloro-3-((4-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (2) were obtained according to the method reported previously. The crystal structures of both compounds were determined by the single crystal X-ray diffraction method. The molecules are non-planar: torsion angles around the N–C(naphthoquinone) bond are 32.62° and 30.61° for 1 and 2, respectively. In both crystals, hydrogen bonds N–H···O and N–H···Cl exist.

A new co-crystal compound of 4,4'-bipyridine and phenylsuccinic acid was synthesized and characterized by elemental analysis, infrared and ultraviolet–visible spectroscopy, and X-ray single crystal diffraction. Crystallographic data for the compound was collected at 150(2) K. The synthesized compound is crystallized in the monoclinic system with the space group P2₁/n and unit cell parameters a = 9.3668(4), b = 18.5075(9), c = 11.1156(5) Å, β = 113.892(2)°. Complicated hydrogen bonding network (O–H···N, C–H···O) accompanied with the C–H···π stacking interaction leads to the formation of 3D supramolecular structure.

The crystal structure of the title compound is determined by single crystal X-ray structure analysis. The structure was solved by direct method and refined to a final R-value of 0.0469 for 2826 observed reflections. The benzocoumarin ring system is planar. The central ring of 4-azaphenantrene moiety has a half chair conformation, phenyl substituent forms dihedral angle of 56.46° with the mean plane of 4-azaphenantrene system. The coumarin system is rotated relative to the latter by 15.48(2)°. This orientation is stabilized by two weak intramolecular C–H···N hydrogen bonds.

Three new Cu(II) complexes, Cu(1,3-bip)(Ac)₂ (I), {[Cu(H₂O)₂(1,3-bip)₂] · (NO₃)₂}_n (II), {[Cu(1,3-bip)(1,4-bdc)]₂ · H₂O · MeOH}_n (III), where 1,3-bip is 1,3-bis(imidazole)propane and 1,4-bdc is terephthalic acid, have been synthesized and characterized by single crystal and powder X-ray diffraction, Fourier transform infrared spectroscopy, and elemental analysis. Single crystal X-ray diffraction reveals that the complex I shows a zero-dimensional architecture, the complex II shows a one-dimensional loop-like chain, and the complex III shows a two-dimensional (4,4) grid layer structure. In addition, the thermal stability of complexes was investigated.

Two mononuclear tetra-coordinated cobalt(II) complexes with molecular formula [Co(L)₂(SCN)₂] (L = 1-methylbenzimidazole (mbim), 1; L = 1-methyl-2-aminobenzimidazole (mabim), 2) were prepared and characterized by IR, EA, and single crystal X-ray diffraction. The central Co(II) ion is tetrahedrally coordinated by two nitrogen atoms of benzimidazole-based ligands and two nitrogen atoms of two thiocyanato ligands. In the crystal structure of 1 and 2, molecules are linked through intermolecular hydrogen bonds and π···π interactions forming a 3D network.

A zinc coordination polymer with V-shaped ligands, [L¹Zn(npa)]_n (L¹ = bis(4-(2'-methylimidazol)phenyl)sulfone, H₂npa = 4-nitrophthalic acid) has been synthesized under solvothermal conditions. The structure has been determined by single-crystal X-ray diffraction analysis and characterized by IR spectra, and elemental analyses. In crystal adjacent [Zn₂(npa)₂] units linked by four bridging ligands L¹ form 2D layers, which are entangled between each other giving inclined interpenetration with the angle of 52.9°, thus resulting in a complicated 3D unique network. Moreover, luminescent properties of the title compound have been investigated.

A coordination polymer, {[Co(bib)₃](BF₄)₂}_n, was prepared for the first time at room temperature via the reaction between cobalt(II) chloride and flexible linker ligand, 1,4-bis(imidazolyl)butane (bib), in the presence of sodium tetrafluoroborate using a three layers method. The compound was characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction. It crystallizes in the triclinic sp. gr. \(P\bar {1}\) with the unit cell parameters a = 9.8124(2), b = 22.1804(4), c = 26.9233(5) Å and α = 71.910(2)°, β = 89.418(2)°, γ = 86.992(2)°. In the polymeric structure of the compound, the cobalt(II) ions have the CoN₆ octahedral geometry and six bib-ligands are coordinated to one metal ion to form an open 3D 2-fold interpenetrated framework (α-polonium-type net, pcu).

A new supramolecular complex [Cd(dcbpy)(im)₂(H₂O)₂] · 3H₂O (H₂dcbpy = 4,4'-dicarboxy-2,2'-bipyridine, im = imidazole) has been prepared under hydrothermal conditions. Its crystal structure is determined with single crystal X-ray diffraction. Cd²⁺ atom is six-coordinated by one dcbpy ligand, two imidazole and two water molecules. Each [Cd(dcbpy)(im)₂(H₂O)₂] unit is connected to neighboring units through intermolecular O–H···O hydrogen bonds to form a three-dimensional supramolecular network structure. A topology method has been used to simplify the network. The stability and luminescent properties of the complex obtained have been investigated.

The allyl 6-amino-5-cyano-4-(4-fluorophenyl)-2-methyl-4H-pyran-3-carboxylate, C₁₇H₁₅FN₂O₃, compound adopts a triclinic crystal system with the sp. gr. \(P\bar {1}\), Z = 2. The 4H-pyran ring adopts a boat conformation with their respective parameters (Q = 0.2384(26) Å, θ = 99.46(65)°, Φ = 10.3(7)°). The fluorophenyl ring is essentially planar. The dihedral angle between fluorophenyl and pyran rings is found to be 85.81(15)°. The structure is stabilized by intermolecular interaction. The N–H···N and N–H···O interactions form a graph set motifs of R\(_{2}^{2}\) (12) and R\(_{4}^{2}\) (20), respectively.

Many pathogenic gram-negative bacteria including Salmonella typhi utilize type III secretion systems (T3SSs) to inject bacterial proteins into host cells and to initiate infections. One of the essential components of the T3SS is the tip protein known as SipD, translocon component via the type III secretion system SPI-1. Here, recombinant SipD is produced and crystallized; the details of cloning, expression, and crystallization are reported. Crystals of SipD are obtained by sitting-drop vapour diffusion method. X-ray diffraction data are collected up to 3.8 Å resolution. Single crystals belong to the monoclinic sp. gr. P2; unit-cell parameters: a = 70.86, b = 103.70, c = 89.28 Å, β = 107.63°.

Sortases are membrane-associated cysteine transpeptidases found mainly in Gram-positive bacteria. They have been intensely studied in pathogenic strains as they play a key role in covalent attachment of various virulence-associated surface proteins including pili to the cell wall and also in biogenesis of pili. The recent identification of sortase genes in some members of gut microbiota indicates their likely role in establishing interaction with the human gastrointestinal tract for probiotic traits. While the structural information about sortases thus far is limited to pathogenic bacteria, here we have the produced recombinant form of housekeeping (SrtA) and pilin-specific (SrtC1) sortases from gut-adapted probiotic strain Lactobacillus rhamnosus GG and crystallized them. The crystals of SrtA and SrtC1 diffracted to a resolution of 1.9 Å and belonged to monoclinic and tetragonal crystal forms respectively.

Urate oxidase catalyzes the oxidative degradation of uric acid to allantoin via peroxide formation by a radical recombination mechanism. Here the crystal structure of urate oxidase (residues 4-310) from Bacillus subtilis 168 (BsUOX) was solved at 2.6 Å resolution. Both crystal structure and small angle X-ray scattering data confirmed that the BsUOX adopts a tetrameric conformation. Comparative analysis of BsUOX structure alignment with crystal structure of urate oxidase complexed with uric acid from Aspergillus flavus (PDB entry 4D12) showed some conserved BsUOX amino acid residues, Thr69, Ser243, Gln245, and Asn271, in the active site region that can potentially bind uric acid. Residues Ile244 and Gln299 are also predicted to interact with the uric acid via hydrophobic interactions but needs further confirmation. This work will be helpful for further functional and biochemical studies of the enzyme for future drug design and development against gout and hyperuricemia.

Uniaxial compression of n-type silicon under joint impact of temperature and constant electric current revealed a significant increase in its plasticity in comparison with the deformation performed only at high temperatures. The electrical conductivity of n-Si samples is found to increase with a rise in plastic deformation. The surface microstructures of deformed samples are studied, and possible explanation of the observed effects is proposed.

The effects of material surface characteristics on the morphology and size of calcium carbonate crystals nucleating under cold wall pipe flow conditions were studied. We found that high surface energy materials could accelerate the conversion of crystals from vaterite to calcite, and the crystal size increased. Aragonite was found to be absent throughout the experiment. The deposition of calcium carbonate crystals is a layer-over-layer formation process. In the initial deposition period, the crystals are large and continue to grow until covering the material surface. At subsequent stages, the crystals forming on the existing fouling become much smaller. Studying the influence of material surface on the morphology and size of calcium carbonate crystals is important both for the reasonable selection of industrial materials and for the synthesis of calcium carbonate crystals with certain morphology and size.

In this study, ZnO particles were grown at different ethanol–water concentrations by using a simple hydrothermal method at 97°C. The changes in structure and morphology of particles were investigated by varying the ethanol concentration. Scanning electron microscope images indicated that ethanol concentration was the main factor affecting the morphology and size of the ZnO particles. X-ray diffractometer pattern showed that crystal structures of the ZnO particles changed with the change in ethanol concentration of the starting solution. Zinc hydroxide phases rather than zinc oxide phases were found in ethanol-rich solutions during hydrothermal synthesis. Photovoltaic properties of the as-synthesized ZnO nanocrystals, as photoanode materials, were tested in dye-sensitized solar cells. Dye-sensitized solar cells were fabricated using a natural black carrot dye, and the performances of these cells were investigated for the electrode materials produced at different ethanol–water concentrations. The best solar energy conversion was obtained with ZnO electrodes fabricated at 100% ethanol concentration.