Examinando por Autor "Vega, Andres"

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    Ítem
    2-(2-pyridylamino)pyridinium tetrachloridozincate(II)
    (International Union of Crystallography, 2008-06-01) Venegas-Yazigi, Diego; Castillo, Carolina; Paredes-Garcia, Veronica; Vega, Andres; Spodine, Evgenia
    The structure of the title compound, (C10H10N3)(2)[ZnCl4], is composed of C10H9N3H+ ( DPAH(+)) cations and [ ZnCl4](2-) anions. The two pyridyl rings of DPAH+ are approximately coplanar, with a dihedral angle of 7.2 ( 2)degrees between their corresponding least-squares planes. The proton is disordered in a one-to-one ratio over the two chemically equivalent pyridyl N atoms. An intramolecular hydrogen bond is formed between the pyridinium H atom and the pyridyl N atom of the other pyridyl ring. The Zn atom lies on a twofold rotation axis. There are also some weak N-H center dot center dot center dot Cl hydrogen bonds. These interactions lead to the formation of an alternating zigzag chain in the solid state. The results clearly show that reducing agents normally used in hydrothermal syntheses, such as metallic zinc employed here, are also active in terms of coordination chemistry.
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    Ítem
    9,10-dihydroxy-4,4-dimethyl-5,8-dihydroanthracen-1(4H)-one
    (International Union of Crystallography, 2008-07-01) Ramirez-Rodriguez, Oney; Martinez-Cifuentes, Maximiliano; Ibanez, Andres; Vega, Andres; Araya-Maturana, Ramiro
    In the title molecule, C16H16O3, the ring system is planar and an intramolecular hydrogen bond is present. The molecular packing is dominated by an intermolecular hydrogen bond and by pi-stacking interactions [interplanar separation 3.8012 angstrom].
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    Ítem
    Azide-Based High-Energy Metal-Organic Frameworks with Enhanced Thermal Stability
    (ACS Omega, 2019-09-10) Chi-Duran, Ignacio; Enríquez, Javier; Manquian, Carolina; Fritz, Ruben Alejandro; Vega, Andres; Serafini, Daniel; Herrera, Felipe; Singh, Dinesh Pratap
    We describe the structure and properties of [Zn(C6H4N5)N3]n, a new nonporous three-dimensional high-energy metal-organic framework (HE-MOF) with enhanced thermal stability. The compound is synthesized by the hydrothermal method with in situ ligand formation under controlled pH and characterized using single-crystal X-ray diffraction, elemental analysis, and Fourier transform infrared. The measured detonation temperature (Tdet = 345 °C) and heat of detonation (Î"Hdet =-0.380 kcal/g) compare well with commercial explosives and other nitrogen-rich HE-MOFs. The velocity and pressure of denotation are 5.96 km/s and 9.56 GPa, respectively. Differential scanning calorimetry analysis shows that the denotation of [Zn(C6H4N5)N3]n occurs via a complex temperature-dependent mechanism.
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    Ítem
    Crystal structure and Hirshfeld surface analysis of tris(2,2′-bipyridine)nickel(II) bis(1,1,3,3-tetracyano-2-ethoxypropenide) dihydrate
    (Acta Crystallographica Section E: Crystallographic Communications, 2019) Chi-Duran, Ignacio; Setifi, Zouaoui; Setifi, Fatima; Jelsch, Christian; Morgenstern, Bernd; Vega, Andres; Herrera, Felipe; Pratap Singh, Dinesh; Hegetschweilerf, Kaspar; Boyaalah, Rabab
    The title compound, [Ni(C10H8N2)3](C9H5N4O)2 2H2O, crystallizes as a racemic mixture in the monoclinic space group C2/c. In the crystal, the 1,1,3,3- tetracyano-2-ethoxypropenide anions and the water molecules are linked by O—H N hydrogen bonds, forming chains running along the [010] direction. The bpy ligands of the cation are linked to the chain via C—H (cation) interactions involving the CH3 group. The intermolecular interactions were investigated by Hirshfeld surface analysis and two-dimensional fingerprint plots.
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    Ítem
    Electronic and Photophysical Properties of Re I (CO) 3 Br Complexes Modulated by Pyrazolyl-Pyridazine Ligands
    (ACS Omega, 2019-03-04) Saldías, Marianela; Guzmán, Nicolas; Palominos, Franco; Sandoval-Altamirano, Catalina; Gunther, German; Pizarro, Nancy; Vega, Andres
    The direct reaction of a series of substituted (1H-pyrazol-1-yl)pyridazine (L I : 6-(1H-pyrazolyl)pyridazine; L II : 3-chloro-6-(1H-pyrazole-1-yl)-pyridazine; L III : 6-(1H-3,5-dimethylpyrazolyl)pyridazine-3-carboxylic acid; L IV : 3,6-bis-N-pyrazolyl-pyridazine; and L V : 3,6-bis-N-3-methylpyrazolyl-pyridazine) with the bromotricarbonyl(tetrahydrofuran)-rhenium(I) dimer leads to the monometallic complexes [(L X )Re(CO) 3 Br] (I-V), which displays a nonregular octahedral geometry around the Re I center and a fac-isomerism for the carbonyl groups, whereas pyridazine and pyrazolyl rings remain highly coplanar after coordination to rhenium. Cyclic voltammetry shows one irreversible oxidation and one irreversible reduction for each compound as measured in N,N-dimethylformamide. Oxidation ranges from 0.94 V for III to 1.04 V for I and have been attributed to the Re I /Re II couple. In contrast, the reductions are ligand centered, ranging from -1.64 V for II to -1.90 V for III and V. Density functional theory calculations on the vertical one electron oxidized and one electron reduced species, using the gas-phase optimized geometry for the neutral complex confirm this assignment. Compounds I-V show two absorption bands, one around 410 nm (metal-to-ligand charge transfer (MLCT), Re dπ → π∗) and the other at ∼300 nm (intraligand, π → π∗). Excitation at 400 nm at 77 K leads to unstructured and monoexponential emission with large Stokes shift, whose maxima vary between 570 (III) and 636 (II) nm. The quantum yields for these emissions in solution are intensified strongly going from air to argon equilibrated solution. Singlet oxygen quantum yields change from 0.03 (III) to 0.21 (IV). These data are consistent with emission from 3 MLCT. The emission undergoes a bathochromic shift when R 1 is a π-donating group (Cl or N-pyrazolyl) and a hypsochromic shift for a π-acceptor (COOH). The bimolecular emission quenching rate constant by triethylamine (TEA) for II, IV, and V is 1.09, 0.745, and 0.583 × 10 8 M -1 s -1 , respectively. Photolysis in dichloromethane-CO 2 saturated solution with TEA as a sacrificial electron donor leads in all cases to formic acid generation.
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    Ítem
    Síntesis de nuevas 1,5 benzodiazepinas mono y di-acetiladas
    (Universidad Andrés Bello, 2010) Orellana Vera, Jorge Cristobal; Vega, Andres; Mercedes Tello, Maria; Pérez L., Patricia; Fuentealba C., Mauricio; Facultad de Medicina; Escuela de Química y Farmacia
    Durante este trabajo se encontró una metodología, basada en la protección por puentes de hidrógeno para la protección regioselectiva del grupo amino presente en la 4-(2-hidroxifenil )-2-fenil-2,3-dihidro- 1 H- l,5-benzodiazepina. Cuando la 4-(2-hidroxifenil)-2-fenil-2,3-dihidro-1H1 - 1,5 -benzodiazepina se hace reaccionar con un exceso de un electrofilo (tal como el anhídrido acético) se espera que la reacción no sea regioselectiva i.e. que se obtenga el producto N- y O-acetilado (diacetilado). Sin embargo, el puente de hidrógeno formado entre el grupo hidroxifenil y el N-5 de la benzodiazepina antes mencionada, ha permitido diferenciar entre los dos centros nucleofilicos de la molécula (OH y N-5), posibilitando así, la introducción regioselectiva del grupo acetilo en el N-5 (mono acetilado) Se ha demostrado que este efecto es dependiente de la temperatura de reacción, así, esta característica ofiece un efecto de protección utilizable para el grupo OH, lo que permite realizar una N-acetilación regioselectiva a temperatura ambiente. Tanto el compuesto mono acetilado como el di acetilado fueron preparados y caracterizados completamente por métodos espectroscópicos y por difracción de Rayos X.