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Mérida, Venezuela

Delgado G.E.,Laboratorio Of Cristalografia | Fernandez J.,Laboratorio Of Analisis Of Quimico Y Estructural Of Materiales | Silva P.,Venezuelan Institute for Scientific Research | Villegas J.,Venezuelan Institute for Scientific Research
Revista Latinoamericana de Metalurgia y Materiales

This paper reports the synthesis, structural and magnetic characterization of the alloy 0.67Cr 0.33S 2. The sample was synthesized using the technique of direct fusion of the constituent elements. Chemical analysis (EDX) allowed establishing the stoichiometric ratios for this alloy. The powder diffraction pattern was indexed and the main phase crystallizes with tetragonal symmetry and unit cell parameters a = 5.3410(1) Å, c = 10.4154(2) Å. This material is isomorphic with the chalcopyrite structure which crystallizes in space group I 4̄2d. Measurements of magnetic susceptibility and electronic paramagnetic resonance, depending on temperature, were performed in a SQUID magnetometer and a Bruker EMX Xband, respectively. The alloy exhibits a ferrimagnetic ordering with Néel temperature ∼ 40 K. The EPR linewidth shows a paramagnetic behavior between 100 and 600 K, while the resonance field and the g factor show a slight variation with temperature. © 2012 Universidad Simón Bolívar. Source

Santi E.,Quimica Inorganica DEC | Viera I.,Quimica Inorganica DEC | Mombru A.,Laboratorio Of Cristalografia | Castiglioni J.,Fisicoquimica DETEMA | And 2 more authors.
Biological Trace Element Research

Five new copper and zinc heteroleptic complexes with saccharin and aminoacids with general stoichiometry Na 2[M(sac) 2(aa) 2]·nH 2O (M denotes Cu or Zn, sac the saccharinate ion, and aa the aminoacids) were synthesized and characterized by elemental and thermogravimetric analysis, conductimetric measurements and IR, Raman and UV-vis spectroscopies. In all the complexes, copper and zinc ions coordinated with the aminoacids through the terminal amine and carboxylate residues and with saccharin through the heterocyclic nitrogen atom. Besides, the superoxide dismutase-like activity of the heteroleptic copper complexes was evaluated and compared with the homoleptic copper amino acid complexes with the aim to observe the influence of the saccharin coordination. © 2011 Springer Science+Business Media, LLC. Source

Bustos C.,Austral University of Chile | Alvarez-Thon L.,Andres Bello University | Carcamo J.-G.,Austral University of Chile | Ibaez A.,Laboratorio Of Cristalografia | Sanchez C.,Austral University of Chile
Acta Crystallographica Section E: Structure Reports Online

The mol-ecular structure of the title compound, C21H 15ClN2O2, features one strong intra-molecular N - H⋯O resonance-assisted hydrogen bond (RAHB). In the crystal, mol-ecules form inversion-related dimers via pairs of weak inter-molecular N - H⋯O contacts. These dimers are further stabilized via three weak C - H⋯O contacts, developing the three-dimensional structure. Source

Torres J.,Catedra de Quimica Inorganica | Morales P.,Catedra de Quimica Inorganica | Dominguez S.,University of La Laguna | Gonzalez-Platas J.,University of La Laguna | And 4 more authors.
Journal of Molecular Structure

The stoichiometric reaction of copper(II) chloride with iminodiacetic acid (H2ida), and lanthanide(III) chloride in water yields the heteropolynuclear complexes [Ln2Cu3(ida) 6]·xH2O. In this work, the synthesis and full characterization of those complexes with Ln = Ce, Ho is presented. The structures are based on [Cu(ida)2] building blocks, linked by the Ln ions via carboxylate bridges. The formation of nanochannels along the crystallographic c axis is verified. The comparison with analogous complexes containing other Ln ions, shows that the channels are perfectly tuneable in size along the series. These chemical systems were also investigated in solution (25.0 °C, I = 0.5 M Me4NCl) by potentiometry. The same kind of polynuclear species have been found in aqueous solution. © 2011 Elsevier B.V. All rights reserved. Source

Delgado G.E.,Laboratorio Of Cristalografia | Mora A.J.,Laboratorio Of Cristalografia | Contreras J.E.,Laboratorio Of Cristalografia | Betancourt L.,University of Los Andes, Venezuela
Bulletin of Materials Science

Mn2SnTe4 was synthesized by direct fusion using the anneal method. X-ray powder diffraction analysis indicated that this material crystallizes in the olivine-type structure, space group Pnma, Z = 4, with unit cell parameters: a = 14.020(2) Å, b = 8.147(1) Å, c = 6.607(1) Å, V = 754.7(2) Å3. The Rietveld refinement converged to the figures of merit, Rp = 6.9%, Rwp = 8.5%, R exp = 6.0%, χ2 = 2.0 and S = 1.4. © Indian Academy of Sciences. Source

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