Home – Home – Jornals – Advanced Search

The optimal structures and the vibrational frequencies of H-bonded complexes formed from one-two CBr₃COOH molecules or the CBr₃CO anion with water molecules are calculated by density functional theory (B3LYP/6-31++G( d , p )). The comparison of the obtained results with the known Raman spectra of the CBr₃COOH-H₂O and NaCBr₃CO ×H₂O solutions (with component molar ratios of £1:16) shows that they include stable hydrates: CBr₃COOH×H₂O and CBr₃CO ×(H₂O)₆. The first one has a cyclic form, and the second has a cubic globular form. The vibrational band frequencies of the CBr₃COOH molecule and the CBr₃CO anion in the spectra of both solutions are almost completely determined by the mutual arrangement of units in these hydrates.

The work studies a partial tungsten substitution for cobalt in the structure of nonstoichiometric SrCo_0.8Fe_0.2O_3-d (SCF) perovskite with mixed oxygen electron conductivity. It is shown that samples of the composition SrCo_{0.8- x} Fe_0.2W _x O_3-d (SCFW) at x ³ 0.03 undergo the endotaxial phase separation with the formation of nanosized domains with a structure of ordered Sr₂CoWO₆ double perovskite, which are distributed in the matrix of nonstoichiometric SrCo_{0.8- x} Fe_0.2W _x O_3-d perovskite. For the materials with 0.02 < x < 0.1, a decrease in the oxygen stoichiometry is accompanied by nanostructuring of the matrix: the formation of nanosized domains in which oxygen vacancies are ordered with the formation of the brownmillerite-like structure.

Two dinuclear complexes [Zn(m-L)(NO₃)(H₂O)]₂ (1) and [Cu₂(m-L)₂(HL)₂](NO₃)₂(C₁₂H₈Br₂)_0.5××H₂O (2), (HL = 3-(2-pyridyl)pyrazole, C₁₂H₈Br₂ = 4,4¢-dibromobiphenyl) are synthesized under hydrothermal conditions and characterized by elemental analysis and X-ray single crystal diffraction. Crystal data for 1: triclinic, P , a = 8.8478(7) Å, b = 15.0550(11) Å, c = 16.4310(12) Å, a = 107.588(4)°, b = 112.498(3)°, g = 115.595(3)°, V = 2099.8(9) ų, Z = 2; for 2: triclinic, P , a = 7.2870(15) Å, b = 8.6840(17) Å, c = 9.3290(19) Å, a = 107.588(4)°, b = 112.498(3)°, g = 115.595(3)°, V = 528.77(18) ų, Z = 1. Complex 1 and 2 are both dinuclear structures which are further packed into a 1D supramolecular chain and a 3D supramolecular framework via weak C-H⋯O hydrogen bond interactions respectively.

The syntheses and crystal structures of the layered coordination polymers M(C₈H₈NO₂)₂ [M = Mn (1), Co (2), Ni (3) and Zn (4)] are described. These isostructural compounds contain centrosymmetric trans -MN₂O₄ octahedra as parts of infinite sheets; the ligand bonds to three adjacent metal ions in m³-N,O,O¢ mode from both its carboxylate O atoms and its amine N atom. In each case, weak intra-sheet N-H⋯O and C-H⋯O hydrogen bonds may help to consolidate the structure. Crystal data: 1, C₁₆H₁₆MnN₂O₄, M _r = 355.25, monoclinic, P 2₁/ c (No. 14), a = 10.6534(2) Å, b = 4.3990(1) Å, c = 15.5733(5) Å, b = 95.1827(10)°, V = 726.85(3) ų, Z = 2, R ( F ) = 0.026, wR ( F ²) = 0.067. 2, C₁₆H₁₆CoN₂O₄, M _r = 359.24, monoclinic, P 2₁/ c (No. 14), a = 10.6131(10) Å, b = 4.3374(4) Å, c = 15.3556(17) Å, b = 95.473(4)°, V = 703.65(12) ų, Z = 2, R ( F ) = 0.041, wR ( F ²) = 0.091. 3, C₁₆H₁₆N₂NiO₄, M _r = 359.02, monoclinic, P 2₁/ c (No. 14), a = 10.6374(4) Å, b = 4.2964(2) Å, c = 15.2827(8) Å, b = 95.9744(14)°, V = 694.66(6) ų, Z = 2, R ( F ) = 0.028, wR ( F ²) = 0.070. 4, C₁₆H₁₆N₂O₄Zn, M _r = 365.68, monoclinic, P 2₁/ c (No. 14), a = 10.6385(5) Å, b = 4.2967(3) Å, c = 15.2844(8) Å, b = 95.941(3)°, V = 694.89(7) ų, Z = 2, R ( F ) = 0.038, wR ( F ²) = 0.107.

A novel coordination polymer [Co₅(OH)₂(dnbpdc)₄(H₂O)₆]×16H₂O (1) (dnbpdc = 6,6¢-dinitro-4,4¢-biphenyl-dicarboxylic acid) is obtained from a hydrothermal reaction. The structure of complex 1 is characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction analysis. The title compound (C₅₆H₇₀Co₅N₈O₅₆, M _r = 2045.85) crystallizes in the triclinic space group P -1 with a = 11.9349(2) Å, b = 12.1895(2) Å, c = 15.420(2) Å, a = 109.390(7)°, b = 94.786(1)°, g = 108.027(9)°, V = 1968.4(4) ų, Z = 1, D _c = 1.726 g/cm³, F (000) = 1045, m(Mo K _a) = 1.154 mm^-1, T = 133(2) K, the final R = 0.0316 and wR = 0.0692 for 7032 observed reflections with I > 2s( I ). The coordination polymer is built of a pentanuclear Co(II) cluster, four dnbpdc ligands, two hydroxyl groups, six coordination water and sixteen crystal water molecules. Ligand oxygen atoms exhibit three types of coordination modes (monodentate, syn-syn bridging bidentate and bridging tridentate). Moreover, the infinite three-dimensional supra-molecular network is generated by coordination and hydrogen bonds. The thermal stability of complex 1 is evaluated by differential scanning calorimetry and thermogravimetric analysis.

The crystal structure of α-(N-benzoxazoline-2-one) acetic acid is studied in the following forms: hydrate, solvate with formic acid, organic monoethanolammonium salt (NН₂(CH₂)₂OH) in two polymorphs produced by minor changes in the crystallization temperature, and also its ethylenediammonium salt (NН₂(CH₂)₂NH₂) in the 2:1 ratio, where amino groups participate in the deprotonation of two molecules of α-(N-benzoxazoline-2-one) acetic acid. Weak intermolecular hydrogen and dative bonds in the crystals consisting of different molecules are analyzed.

The molecular structures of 5,7-di(tert-butyl)-2-(6,8-dimethyl-4-piperidinoquinoline-2-yl)-3-hydroxytropone and 5,7-di(tert-butyl)-2-(5,8-dimethyl-4-piperidinoquinoline-2-yl)-3-hydroxytropone are determined by the single crystal X-ray diffraction analysis.

The method of single crystal X-ray diffraction (XRD) is used to study the crystal structures of the following trinitromethyl derivatives of 1,3,5-triazine: 2,4-diazido-6-trinitromethyl-1,3,5-triazine (1), 2,4-dimethoxy-6-trinitromethyl-1,3,5-triazine (2), 2,4-bis(N,N-dimethylamino)-6-trinitromethyl-1,3,5-triazine (3). Some features of the structure (geometry) of the trinitromethyl group and its location relative to the 1,3,5-triazine ring is determined.

Two mononuclear manganese(III) complexes, [MnL¹(OH₂)(CH₃OH)]×ClO₄ (1) and [MnL²] (2), where L¹ and L² are the deprotonated forms of N,N¢-bis(5-chloro-2-hydroxybenzylidene)ethane-1,2-diamine and tris{2-[(3,5-dichlorosalicylidene)amino]ethyl}amine, respectively, are obtained by the reaction of Schiff bases with manganese perchlorate in methanol. The complexes were characterized by elemental analysis, IR spectra, and single crystal X-ray determination. In both complexes, Mn atoms are in the octahedral coordination. In the crystal structure of complex 1, the complex molecules are linked by water ligands through intermolecular O-H⋯O hydrogen bonds to form dimers. The perchlorate anions are linked to the complex molecules through intermolecular O-H⋯O hydrogen bonds. In the crystal structure of complex 2, the molecules are stacked along the y axis through p⋯p interactions. The catalytic oxidation on olefins of the complexes is studied.

The method of grazing incidence X-ray diffraction (GIXRD) is used to study the hexagonal boron nitride (h-BN) films produced by plasma-enhanced chemical vapor deposition (PECVD) from borazine and ammonia or helium mixtures. The diffraction patterns of boron nitride layers aligned vertically on the substrate are obtained for the first time. The films deposited consist of the amorphous phase and the nanocrystalline h-BN phase. The nanocrystallite sizes in the films obtained from the mixtures of borazine (B₃N₃H₆) with both ammonia and helium increase with an increase in the synthesis temperature. Nanocrystallites are heteraxial and have a layered structure with the interplanar spacing of ~0.35 nm.