Chiral Templating Activity of Tris(bipyridine)ruthenium(II) Cation in the Design of Three-Dimensional (3D) Optically Active Oxalate-Bridged {[Ru(bpy) 3 ][Cu 2 x Ni 2(1 - x ) (C 2 O 4 ) 3 ]} n (0 ≤ x ≤ 1; bpy = 2,2‘-bipyridine): Structural, Optical, and Magnetic Studies

Three-dimensional oxalate-based {[Ru(bpy)3][Cu2xNi2(1-x)(ox)3]}n (0≤ x ≤ 1, ox = C2O42-, bpy = 2,2‘bipyridine) were synthesized. The structure was determined for x = 1 by X-ray diffraction on single crystal. The compound crystallizes in the cubic space group P4132. It shows a three-dimensional 10-gon 3-connected (10,3) anionic network where copper(II) has an unusual tris(bischelated) environment. X-ray powder diffraction patterns and their Rietveld refinement show that all the compounds along the series are isostructural and single-phased. According to X-ray absorption spectroscopy, copper(II) and nickel(II) have an octahedral environment, respectively elongated and trigonally distorted. As shown by natural circular dichroism, the optically active forms of {[Ru(bpy)3][CuxNi2(1-x)(ox)3]}n are obtained starting from resolved Δ- or Λ-[Ru(bpy)3]2+. The Curie−Weiss temperatures range between −55 (x = 1) and −150 K (x = 0). The antiferromagnetic exchange interaction thus decreases when the copper contents increases in agreement with the crystallographic structure of the compounds and the electronic structure of the metal ions. At low temperature, the compounds exhibit complex long-range ordered magnetic behavior.

Structural Studies of Transition Metal Complexes with 4,5-Bis(2-pyridylmethylsulfanyl)-4‘,5‘-ethylenedithiotetrathiafulvalene: Probing Their Potential for the Construction of Multifunctional Molecular Assemblies

Three divalent transition metal complexes of 4,5-bis(2-pyridylmethylsulfanyl)-4‘,5‘-ethylenedithiotetrathiafulvalene have been prepared and crystallographically characterized. The isostructural Co(II) and the Ni(II) complexes show octahedral geometries around the metal ions with the coordination sites occupied by the pyridyl nitrogen atoms and the thioether sulfur atoms of the ligand and cis coordination of the halide ions. Cyclic voltammetry reveals that the complexation leads to a small anodic shift in the first oxidation potential of the TTF system.

Reações de 1,2-dicloro-4,5-dinitrobenzeno com aminas: monossubstituição de nitro e dissubstituição de cloro e nitro

1,2-dichloro-4,5-dinitrobenzene (DCDNB) reacts with primary and secondary amines, in acetonitrile, at room temperature, to give a monosubstituted nitro product with a yield of 85 to 95%. The chloro-nitro-disubstituted product is formed with excess amine under reflux. Piperidine, pyrroline, dimethylamine and methylamine were the most reactive reagents in both mono- and disubstitution.

Theoretical study of the structure and stability of NbxOy, and NbxOy+ (x = 1-3; y = 2-5, 7, 8) clusters

Geometric, thermodynamic and electronic properties of cluster neutrals NbxOy and cations NbxOy+ (x = 1-3; y = 2-5, 7, 8) have been characterized theoretically. A DFT calculation using a hybrid combination of B3LYP with contracted Huzinaga basis sets. Numerical results of the relative stabilities, ionization potentials and band gaps of different clusters are in agreement with experiment. Analysis of dissociation channels supports the more stable building blocks as formed by NbO2, NbO2+ NbO3 and NbO3+ stoichiometries. The net atomic charges suggest that oxygen donor molecules can interact more favorably on central niobium atoms of cluster cations, while the interaction with oxygen acceptor molecules is more favorable on the terminal oxygen atoms of neutral clusters. A topological analysis of the electron localization function gradient field indicates that the clusters may be described as having a strong ionic interaction between Nb and O atoms. Published by Elsevier B.V. B.V.

Studies on the reduction of the nitro group in 3-aryl-2-methylene-4-nitro-alkanoates afforded by the Baylis-Hillman adducts: Synthesis of 4-aryl-3-methylene-2-pyrrolidinones and 3-(1-alkoxycarbonyl-vinyl)-1H-indole-2-carboxylates

The formation of substituted 2-pyrrolidinones and indoles by the reduction of the secondary nitro group in appropriate 3-aryl-2-methylene-4-nitroalkanoates afforded by Baylis-Hillman chemistry via different reducing agents is described. The 3-aryl-2-methylene-4-nitroalkanoate obtained from SN2 nucleophilic reaction between the acetate of Baylis-Hillman adducts and ethyl nitroacetate upon reduction with indium-HCl furnishes a mixture of cis and trans substituted phenyl-3-methylene-2-pyrrolidinones. In contrast, similar reductions of analogous substrates derived from nitroethane stereoselectively furnished only the trans substituted phenyl-3-methylene-2-pyrrolidinones. On the other hand the SnCl2.2H2O-promoted reductions of substrates derived from nitro ethylacetate give oxime derivatives while the ones obtained from nitroethane yield a mixture of cis and trans 4-aryl-3-methylene-2-pyrrolidinones. Alternatively, the SnCl2.2H2O-promoted reduction of substituted 2-nitrophenyl-2-methylene-alkanoate furnished from ethyl nitroacetate yields 3-(1-alkoxycarbonyl-vinyl)-1H-indole-2-carboxylate while indium-promoted reaction of this substrate leads to a complex mixture. Analogous reactions with SnCl2.2H2O of substituted 2-nitrophenyl-2-methylene-alkanoate obtained from nitroethane yield 4-alkyl-3-methylene-2-quinolones in moderate yields

Benzo1,2-b:4,5-b 'difuran-based sensitizers for dye-sensitized solar cells

Two BDF-based organic sensitizers, as first examples for their use in dye-sensitized solar cells, are prepared and characterized. They yield promising power conversion efficiencies of up to 5.5 and high open circuit voltages up to 0.82 V. This work demonstrates that the BDF chromophore acts as an effective donor in organic sensitizers.

Uber 1.3-Diketo-2.4-tetrachlorhydronaphtalin und dessen Umwandlungsprodukte.

Thesis (doctoral)--Universitat Marburg.

MÉTODO ALTERNATIVO PARA A SÍNTESE E MECANISMO DE 2-(1,3-DITIANO-2-ILIDENO)-ACETONITRILA

We report an alternative method for the synthesis of 2-(1,3-dithian-2-ylidene)-acetonitrile using 3-(4-chlorophenyl)-3-oxopropanenitrile and carbon disulfide as starting materials. The methanolysis of the intermediate 3-(4-chlorophenyl)-2-(1,3-dithian-2-ylidene)-3-oxopropanenitrile occurs via three possible intermediates, leading to the formation of the product at a 75% overall yield. Molecular modeling simulation of the reaction pathway using B3LYP 6-311G++(2df,2p) justified the proposed reaction mechanism.

The tautomerism, solvatochromism and non-linear optical properties of fluorescent 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine

The Schiff base, 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine, was synthesized by the condensation of 3-hydroxyquinoxaline-2-carboxaldehyde with 4-aminoantipyrine. HPLC, FT-IR and NMR spectral data revealed that the compound exists predominantly in the amide tautomeric form and exhibits both absorption and fluorescence solvatochromism, large stokes shift, two electron quasireversible redox behaviour and good thermal stability, with a glass transition temperature of 104oC. The third-order non-linear optical character was studied using open aperture Z-scan methodology employing 7 ns pulses at 532 nm. The third-order non-linear absorption coefficient, b, was 1.48 x 10-6 cm W-1 and the imaginary part of the third-order non-linear optical susceptibility, Im c(3), was 3.36 x10-10 esu. The optical limiting threshold for the compound was found to be 340 MW cm-2.

The tautomerism, solvatochromism and non-linear optical properties of fluorescent 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine

The Schiff base, 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine, was synthesized by the condensation of 3-hydroxyquinoxaline-2-carboxaldehyde with 4-aminoantipyrine. HPLC, FT-IR and NMR spectral data revealed that the compound exists predominantly in the amide tautomeric form and exhibits both absorption and fluorescence solvatochromism, large stokes shift, two electron quasireversible redox behaviour and good thermal stability, with a glass transition temperature of 104 oC. The third-order non-linear optical character was studied using open aperture Z-scan methodology employing 7 ns pulses at 532 nm. The third-order non-linear absorption coefficient, b, was 1.48 x 10-6 cm W-1 and the imaginary part of the third-order non-linear optical susceptibility, Im c(3), was 3.36x10-10 esu. The optical limiting threshold for the compound was found to be 340 MW cm-2.

Oxford reading tree. Teacher's guide 2 : stages 4-5.

Explicaciones detalladas de cómo sacar el máximo provecho de cada etapa. Las ideas y sugerencias de esta guía mantienen y amplían la filosofía de la lectura, y el programa, según la propuesta de métodos de enseñanza establecidos en la guía del primer nivel, que ayudarán a dar a los niños la confianza, y las habilidades necesarias para hacer frente a historias con textos más extensos y complejos. Contiene actividades de apoyo a una serie de estrategias de lectura, recursos fotocopiables, actividades tranversales de los contenidos curriculares, evaluación con hojas de registro. También incluye material adicional.

Structural characterization of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) powders

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate-lead titanate (PMN-50PT). Ab initio study of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) ceramic powders, with x = 0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic-tetragonal phases in the system. It was verified that even for 40 mol% of barium, it was possible to obtain pyrochlore-free PMN-PT powders. The increase of the lattice parameters of PMN-PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120 nm for 40 mol% of barium against 167 mn for the pure sample. Although high barium content (40 mol%) was deleterious for a dense ceramic, contents up to 20 mol% allowed 95% density when sintered at 1100 degrees C for 4 h. (c) 2007 Elsevier Ltd. All rights reserved.