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18 citations found for Yakovenko, A

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In the title compound, [Hg3(C6F4)3(C3H8O2)2], two O atoms from one 2-meth­oxy­ethanol ligand and one O atom from the second 2-meth­oxy­ethanol ligand coordinate three HgII atoms [Hg-O = 2.765 (7)-2.890 (8) Å] in the trimeric organomercurial Lewis acid (o-C6F4Hg)3. The hy­droxy groups are involved in formation of intra- and inter­molecular O-H...O hydrogen bonds; the latter link two mol­ecules into centrosymmetric dimers. An extensive net of weak inter­molecular C-H...F inter­actions further consolidates the crystal packing.

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Acta Cryst. (2014). A70, C994
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Since the discovery of metallic conductivity in the TTF-TCNQ complex, the charge transfer (CT) complex materials have been studied for such properties as semiconductivity or superconductivity. The synthesis of new CT materials using trimeric perfluoro-ortho-phenylene mercury (Hg3) as electron acceptor compound was done first by Haneline and Gabaï [1]. A series of studies of CT materials containing Hg3 and tetrathiafulvalene (TTF) or dithieno thiophene (DTT) as an electron donor compounds was carried out by different methods. Co-crystalzation with TTF gave a larger variety of co-crystals than with DTT, producing three polymorphs and one pseudo-polymorph. One pot crystal growth of TTF and Hg3 in a 1:1 mixture of solvents dichloromethane (DCM) and dichloroethane (DCA) has led to the formation of TTF polymorphs 1 and 2 with same 1:1 donor acceptor ratio [Hg3·TTF] as well a pseudopolymorph [Hg3·TTF·DCA] 3 that contains the solvent DCA in the asymmetric unit. Slow evaporation in a 1:1 mixture of dichloromethane and carbon disulfide was used to obtain the previously reported CT [(Hg3)2·TTF] (4)1. By slow evaporation as well in pure dichloromethane was obtained the CT material [Hg3·DTT·DCM] 5. All these five CT co-crystals contain mixed donor acceptor stacks, however only in 3, 4 and 5 these stacks are parallel to each other. In the packing of 1 and 2 these stacks are in herringbone arrangement. Polymorphs 1 and 2 differ in crystal shape and color. Contacts Hg···S shorter than the sum of the Van Der Walls radii were observed in the five CTs materials reported, however only 1, 2, 3, and 5 have extended short donor acceptor molecular associates. Moreover only 3, and 5 has these extended donor acceptor associates along one direction.

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Acta Cryst. (2014). A70, C1175
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Mixtures of Cu-Fe oxides are used for numerous industrial catalytic processes including the Water-gas shift reaction (WGS: CO + H2O -> CO2 + H2). In this work we measure the structural changes of CuFe2O4 under redox (oxidizing and reducing) and WGS reaction conditions. A key component associated with the catalytic properties of this material is the reversible transfer of Cu in and out of the spinel structure during the reaction. The WGS reaction is the most active when Cu is metallic and on the surface of the spinel which has become Fe3O4. The reversible nature of the Cu migration preserves the activity of the catalyst and protects the Cu species from deactivation. We investigate the cation migration process from the octahedral site inside the spinel to the surface as Cu metal, using modulation measurements that perturb the dynamic structural properties of the spinel structure in a time resolved manner. The experiments termed MED [1] involve the switching of co-reactants (i.e. CO -> O2 -> CO -> O2) so that the residence time of specific adsorbates can be controlled, thus we can probe directly the role of the reactant and the redox sensitivity in the migration of the Cu cation. We demonstrate how distinguishable this technique is from previous steady-state measurements. The powder patterns are averaged over several cycles of gas (CO/H2/O2) variations. Phase-sensitive detection is applied to demodulate the data, picking up structural changes which occur in phase with reactant in-flow variations. Oscillations of the diffracted signal can be observed at the stimulation frequency [omega], but also at the harmonic 2[omega]. Therefore the Fourier analysis of the components provides selective access to partial diffraction contributions otherwise merged into one average diffraction signal. This work is supported by the BNL LDRD program and experiments were performed at the APS and at the NSLS.

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Acta Cryst. (2017). A73, C352
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Area detector calibration can be improved greatly by translating the detector to multiple distances from the sample.

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Pressure, temperature and deuteration-dependent phase transition in the ammonium copper salt, (NH4)2[Cu(H2O)6](SO4)2, was studied using neutron and X-ray diffraction on single crystal and powder samples.

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A monoclinic modification of chlorido­mercurioferrocene, [FeHgCl(C5H4)(C5H5)], was found on its crystallization from acetonitrile. A triclinic form of the title compound [Sunkel & Kiessling (2001). J. Organomet. Chem. 637, 796-799] was crystallized from chloro­form. Both forms have two molecules per asymmetric unit. In the monoclinic form, both mol­ecules have an eclipsed conformation, while in the triclinic form one of them has an eclipsed and the other a staggered conformation. In the monoclinic crystals, mol­ecules form infinite ribbons due to inter­molecular secondary coordination between Hg and Cl atoms, while in the triclinic form mol­ecules are arranged in tetra­mers.


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A double-crystal monochromator composed of a meridionally bent Bragg crystal and a sagittally bent Laue crystal is proposed for bi-directional focusing of high-energy X-ray beams.

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An ortho­rhom­bic (space group Pbcn) polymorph of the title compound, C18H22O7S2, was obtained from a methanol solution to complement the known monoclinic (space group C2/c) phase. No phase transition has been found between the two systems in the temperature range 120-296 K. The central O atom of the mol­ecule has site symmetry 2.

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The low-temperature study of the title compound, (C36H30NP2)2[Cu2Br4], revealed the nature of rotational disorder which has been observed at room temperature for the [Cu2Br4]2- anion. The centrosymmetric anion has a planar structure with slightly distorted trigonal coordination of the Cu atoms.

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High-pressure synchrotron powder diffraction studies of the magnetic molecular framework cobalt(II) dicyanamide, Co(dca)2, revealed a reversible orthorhombic to monoclinic transformation at 1.1 GPa and negative linear compressibility over the measured pressure range up to 4.2 GPa.

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A new metal-organic framework-specific method for structure envelope construction is proposed. Structure solution from powder X-ray diffraction data of metal-organic frameworks has been demonstrated on activated and as-synthesized samples of HKUST-1 and an activated sample of PCN-200.

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The title diadduct, C16H16O2, has been redetermined by X-ray diffraction methods at 120 K. In this work, we report more exact values of bond and angles.

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