Search results for "Zen"
showing 10 items of 3479 documents
Reversible Dimerization of Tetraureas Derived from Calix[4]Arenes
1999
Calix[4]arene derivatives, substituted at the wider rim by four urea functions are easily available in great variety. In apolar solvents like benzene or chloroform they dimerize via NH…O=C hydrogen bonds encapsulating a single solvent molecule as guest. The exclusive formation of dimers has been proved in solution by NMR, while their shape has been characterized by single crystal X-ray analysis. The kinetic stability and the rate of the guest exchange have been studied by NOESY experiments using a derivative with lower symmetry.
3-(2-Fluorophenyl)-6-(phenoxymethyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole
2008
The crystal structure of the title compound, C16H11FN4OS, was synthesized in the course of our studies on 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles as inhibitors of p38 mitogen-activated protein kinase (MAPK). The three-dimensional data obtained were used to generate a three-dimensional pharmacophore model for in silico database screening. The dihedral angles between the central heterocylic system and the fluorophenyl and phenyl rings are 20.21 (3) and 5.43 (1)°, respectively; the dihedral angle between the two benzene rings is 15.80 (4)°.
N-{4-[(3-Methyl-phen-yl)sulfamo-yl]phen-yl}benzamide.
2011
In the title compound, C20H18N2O3S, the dihedral angle between the central benzene ring and the amide group is 24.1 (3)° and that between this ring and the aromatic ring of the tolyl group is 68.2 (16)°. In the crystal, adjacent molecules are linked by N—H...O hydrogen bonds into a linear chain running along [100]. Weak C—H...O contacts also occur. Extensive weak π–π interactions exist from both face-to-face and face-to-edge interactions occur between the aromatic rings [centroid–centroid distances = 3.612 (2) and 4.843 (2) Å].
3-(2,4-Dimethoxyanilino)-8-methoxydibenz[b,e]oxepin-11(6H)-one
2011
In the title compound, C23H21NO5, the two benzene rings of the tricyclic unit are oriented at a dihedral angle of 37.5 (8)°. The 2,4-dimethoxyanilino residue is oriented at a dihedral angle of 60.2 (8)° towards the phenoxy ring. In the crystal, the central carbonyl O atom accepts two hydrogen bonds from the N—H and C—H groups. A further intermolecular C—H...O interaction involving one of the methoxy O atoms is also observed.
3-(2,4-Difluoro-anilino)-9-nitro-dibenzo[b,e]oxepin-11(6H)-one.
2011
In the title compound, C20H12F2N2O4, the two benzene rings of the tricyclic unit are oriented at a dihedral angle of 30.6 (1)°. The 2,4-difluoroanilino residue is oriented at a dihedral angle of 68.2 (1)° with respect to the phenoxy ring. In the crystal, N—H...O hydrogen bonds between the amino group and the carbonyl O atom of the oxepinone ring link the molecules into infinte chains along the c axis.
1-[2-(2,4-Dichlorophenyl)pentyl]-1H-1,2,4-triazole
2009
The title compound, C13H15Cl2N3, also known as penconazole, crystallizes as a racemate. The dihedral angle between the benzene and triazole rings is 24.96 (13)°. In the crystal structure, molecules are linked into chains running parallel to the c axis by intermolecular C—H...N hydrogen-bonding interactions.
Guest-Host Systems of 1,3,5-Tristyrylbenzenes
2003
(E,E,E)-1,3,5-Tris(3,4,5-trimethoxystyryl)benzene (1a) forms monoclinic crystals of the space group P21/c. Incorporation of three transoid diacetyl guest molecules between the three arms leads to triclinic crystals of the space group P1. The styryl groups, originally present in a nonsymmetrical conformation, are simultaneously transformed to a C3 arrangement. (E,E,E)-1,3,5-Tris- (3,4,5-tripropoxystyryl)benzene (1b) forms monoclinic crystals of the space group P21/c. The C3 arrangement of the styryl groups is present in the first, the unsymmetrical arrangement in the second modification. Incorporation of two acetone guests in the largest and the middle-sized angle space between the styryl ar…
Dimeric capsules of tetraurea calix[4]arenes. MD simulations and X-ray structure, a comparison
2002
The single crystal X-ray structure of a homodimer of a tetra(tolylurea) calix[4]arene including a tetraethylammonium cation as guest shows an expansion of the capsule and a distortion of its shape, in comparison to the structure of a similar dimer with an encapsulated benzene molecule. Thus, only 8 of 16 possible hydrogen bonds are present in the hydrogen bonded belt holding together the two hemispheres. The encapsulated cation is disordered over two equivalent positions with two methyl groups pointing to the equator, while two methyl groups pointing to the poles form CH–π interactions with the inner surfaces of the calixarene cavities. MD simulations are in agreement with the distorted X-r…
Education for democratic citizenship in a digital culture
2011
Asumiendo la importancia de las nuevas tecnologías en las aulas, especialmente en las actuales sociedades de la información y la comunicación, y siguiendo las recomendaciones de la Unión Europea a favor de la alfabetización mediática, el presente trabajo reflexiona acerca de la necesidad de educar no solo en los usos técnicos y eficientes de las tecnologías comunicativas, sino también en el uso responsable y cívico de las mismas, favoreciendo así los procesos participativos y deliberativos que son el sustento de una democracia viva. El sueño griego de la «isegoría», del igual derecho de todos al uso de la palabra, puede hacerse realidad en la cultura digital, si bien es cierto que un uso hi…
Las migraciones coloniales del Caribe a Estados Unidos y Europa Occidental : colonialidades diferenciadas en cuatro centros del sistema-mundo / Colon…
2017
Resumen: Este artículo compara cuatro migraciones caribeñas hacia las cuatro metrópolis que dominan el Caribe hoy. Se trata de las migraciones desde territorios no-independientes del Caribe: desde Martinica/Guadalupe hacia Francia, Puerto Rico hacia los Estados Unidos, Surinam/Caribe Holandés hacia Holanda y Caribe Británico hacia el Reino Unido. El artículo no solamente compara los procesos de emigración sino también los procesos de incorporación al llegar a las cuatro metrópolis. La comparación nos da una idea fundamental acerca de las diferencias entre estas metrópolis en términos de ciudadanía, mito fundacional de nación, racismo, y política pública hacia las minorías racializadas.Palab…