Search results for " sphere"
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Educación para la ciudadanía democrática en la cultura digital
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…
Cu(II) and Cu(I) complexes with 1,2-dithiosquarate as a ligand; from molecular compounds to supramolecular network structures
2008
Abstract Four new complexes of copper(II) and/or copper(I) with 1,2-dtsq as a ligand have been synthesized and characterized by single crystal X-ray diffraction methods, [CuII(terpy)(1,2-dtsq)] (1), [CuII(dmen)(1,2-dtsq)]n (2), {[CuII(dmen)2][CuI(1,2-dtsq)]2}n·2nH2O(3) and {[CuII(men)2][CuI (1,2-dtsq)]2}n·nH2O (4) (1,2-dtsq = 1,2-dithiosquarate, dianion of 3,4-dimercapto-1-cyclobutene-1,2-dione; dmen = N,N-dimethylethylenediamine; men = N-methylethylenediamine, terpy = 2,2′:6,2″-terpyridine). Compound 1 consists of neutral [CuII(terpy)(1,2-dtsq)] mononuclear units which are held together by O⋯H–C and van der Waals interactions. Compound 2 is built of neutral [CuII(dmen)(1,2-dtsq)] entities …
X-X through-cage bonding in Cu, Ni, and Cr complexes with M3X2 cores (X=S, As).
2008
Density functional calculations on trinuclear complexes bridged by two sulfur atoms, [(tmeda)(3)Cu(3)(mu-S)(2)](3+), [(tmeda)(3)Ni(3)(mu-S)(2)](2+), and [(tmeda)(3)Ni(3)(mu-S(2))](4+), as well as on the formation of [(tmeda)(3)Cu(3)(mu-S)(2)](3+) from a dinuclear [(tmeda)(2)Cu(2)(mu-S(2))](2+) complex and a mononuclear [(tmeda)Cu(eta(2)-S(2))](+) fragment, are reported. A qualitative orbital analysis of the M(3)X(2) framework bonding is presented for the case in which each metal atom M has a square planar coordination sphere completed by one bidentate or two monodentate ligands (that is, [(L(2)M)(3)X(2)] compounds). It is concluded that a framework electron count (FEC) of 12 corresponds to …
Organotin(IV) complexes with tetraethyl ethylene- and propylene-diphosphonates
1995
The series of organotin halide complexes with tetraethyl ethylene- and propylene-diphosphonates R n SnX 4-n .L [n=0, X=Cl; n=1, R=Me, X=Cl, Br; n=1, R=Ph, X=Cl; n=2 R=Me, Et, Bu, X=Cl, Br; n=2, R=Ph, X=Cl; L=(EtO) 2 P(O)CH 2 CHR'P(O)(OEt) 2 , R'=H, Me] were synthesized and characterized by means of NMR and Mossbauer spectroscopy. The crystal structure of the complex of diphenyltin dichloride with propylenediphosphonate was determined. The complex consists of polymer chains with bridging bidentate ligands and an octahedral tin environment containing two types of phosphoryl fragments. All of the R 2 SnX 2 adducts have trans-R 2 SnX 4 geometries of tin coordination octahedra according to the q…
Exchange Coupling Mediated by N–H···Cl Hydrogen Bonds: Experimental and Theoretical Study of the Frustrated Magnetic System in Bis(o-phenylenediamine…
2012
The title compound crystallizes in the monoclinic P2(1)/c space group with a = 11.2470(3) A, b = 5.9034(2) A, c = 12.0886(3) A, β = 115.143(1)°, and V = 726.58(4) A(3) and consists of discrete monomeric NiCl(2)(o-phenylendiamine)(2) molecules. Each o-phen ligand coordinates in a bidentate mode with the chloride ions occupying trans positions in the resulting tetragonally distorted octahedral coordination sphere. Two discrete sets of N-H···Cl hydrogen bonds link the octahedral molecules into a two-dimensional network, with type 1 interactions linking adjacent monomers along the c axis and type 2 interactions linking monomers along the diagonals in the bc plane. Analysis of the magnetic data …
Anion-Directed Self-Assembly of Unusual Discrete and One-Dimensional Copper(II) Complexes of 3,6-Bis(2′-pyridyl)pyridazine
2012
The preparation and crystal structures of six new copper(II) compounds of formula [Cu(dppn)2(ClO4)]ClO4 (1), [Cu2(dppn)(OH)(ClO4)3(H2O)3]·H2O (2), [Cu2(dppn)2(H2O)2](ClO4)4 (3), [Cu2(dppn)2(ClO4)4] (4), {[Cu2(dppn)(N3)4]·H2O/[Cu2(dppn)(N3)4(H2O)]}n (5) and {[Cu2(dppn)(OH)(dca)3]·H2O}n (6) [dppn = 3,6-bis(2′-pyridyl)pyridazine and dca = dicyanamide] are reported. 1 is a mononuclear complex where two bidentate dppn molecules and a monodentate perchlorate build an intermediate square pyramidal/trigonal bipyramidal (sp/tbp) five-coordinate environment around the copper(II) ion, the overall positive charge being balanced by a free perchlorate anion. 2–4 are dinuclear complexes with either one (2…
X-ray crystal structure and antimony-121 Mössbauer spectrum of catecholato bis(1,10-phenanthroline)antimony(III) tetraphenylborate
1985
The crystal structure of the title compound was solved by means of X-ray diffraction at room temperature. The salt consists of a tetrahedral tetraphenylborate anion and a complex cation containing a catecholatoantimony(III) unit chelated by two 1,10-phenanthrolines. The three bidentate ligands are essentially arranged in one half of the Sb coordination sphere, leaving ample space to accomodate the lone pair of electrons. The Mossbauer parameters of the title compound and of the complex (C6H4O2)SbF·Phen were measured and their rationalization accomplished in the light of their respective molecular structures.
Hard-sphere fluids in annular wedges: density distributions and depletion potentials.
2009
We analyze the density distribution and the adsorption of solvent hard spheres in an annular slit formed by two large solute spheres or a large solute and a wall at close distances by means of fundamental measure density functional theory, anisotropic integral equations and simulations. We find that the main features of the density distribution in the slit are described by an effective, two--dimensional system of disks in the vicinity of a central obstacle. For large solute--solvent size ratios, the resulting depletion force has a straightforward geometrical interpretation which gives a precise "colloidal" limit for the depletion interaction. For intermediate size ratios 5...10 and high sol…
Synthesis, crystal structure, electrochemical and magnetic properties of (NBu4)[ReCl5(L)] with L=pyrimidine and pyridazine
2008
Abstract Two novel rhenium(IV) compounds, namely (NBu4)[ReCl5(pym)] (1) and (NBu4)[ReCl5(pyd)] (2) (pym = pyrimidine, pyd = pyridazine and NBu4 = n-tetrabutylammonium cation), have been obtained by reaction of [ReCl6]2− and the diazine in dmf, and their crystal structures determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of [ReCl5(pym)]− or [ReCl5(pyd)]− anions and NBu 4 + cations held together by electrostatic forces and van der Waals interactions. Stacking interactions are present only in 1. The coordination sphere of the ReIV ion is defined by five chloride anions and one nitrogen atom of a monodentate diazine, resulting in a distorted octahedral environme…
Automated Electron Diffraction Tomography
2012
Ab-initio structure analysis by electron diffraction is hampered by two major problems: insufficient number of reflections sampled and an intensity alteration by dynamical scattering contribution or beam damage. Thus, in recent years the principles of automated diffraction tomography (ADT) allowing systematic reciprocal space sampling and automated data analysis were developed. Here the basic ideas of ADT and its general applicability will be discussed along with some examples of solved structures.