Search results for "Cuba"
showing 10 items of 340 documents
Assembling Magnetic Blocks: A Strategy to Control the Nuclearity and Magnetic Properties of Polynuclear Complexes
1996
Synthetic strategies dealing with the polymerization of either di-μ-hydroxocopper(II) complexes or 2,2′-bipyrimidine (bpym)-containing first row transition metal ions allow the preparation of polynuclear compounds whose structures and magnetic properties are presented here. The influence of structural and chemical parameters on the magnitude of the singlet-triplet energy gap (J) in di-μ-hydroxocopper(II) complexes [LCu(OH)2CuL]2+ with L = 2,2′-bipyridine (bpy) and bpym is analyzed and discussed. Special attention is devoted to nature of the counterion which allows the preparation of hydroxo-bridge copper(II) cubane and double cubane type complexes where all the intramolecular magnetic inter…
Ferromagnetic coupling in a one-dimensional molecular railroad copper(II) azido compound containing a defective double cubane motif.
2001
The compound [Cu2(bpm)2(N3)4]n (bpm = bis(pyrazol-1−yl)methane) shows three unique coordination modes (μ1,1-, μ1,1,1-, μ1,1,3-N3) and ferromagnetic interaction between the copper(II) ions. The structure of the compound exhibits a one-dimensional railroad polymer made up of repeating defective dicubane-type units linked by μ1,1,3-N3 bridges.
The Receptor Functions of Endogenous C1q, a Subcomponent of the First Component of Complement, on Peritoneal Macrophages
1982
Abstract C1q, the Fc recognizing subcomponent of the first complement component was shown to be synthesized by peritoneal macrophages. Evidence is presented that C1q serves during the secretion phase as Fc binding protein on the membrane of these macrophages. A dose-dependent inhibition of Fc rosette formation occured when the macrophages were pretreated with anti-C1q -F(ab') 2 . The C3b rosette formation was not affected. In addition, preincubation of peritoneal macrophages with anti-C1q -F(ab') 2 abolished specifically the polyanion mediated stimulation to secrete dose and time dependently lysosomal enzymes. There was no polyanion-induced enzyme release after incubation of polyanions with…
Virazole (Ribavirin) a Cytostatic Agent
1978
Virazole (1-β-D-ribofuranosyl-1,2,4-triazole-3carboxamide,ribavirin) is a synthetic triazol nucleoside with a broad spectrum of antiviral activity. But virazole affects the metabolism not only of virus infected cells. Virazole strongly inhibits the cell proliferation of mouse lymphoma cells (L 5178y), which were not infected with DNA- or RNA-viruses. Starting with 3 × 103 cells/ml and an incubation period of 72 hr, the drug reduces the cell proliferation to 50% (= ED50 concentration) in a concentration of 4,7 μM.
ChemInform Abstract: Cobalt Clusters with Cubane-Type Topologies Based on Trivacant Polyoxometalate Ligands.
2016
Four novel cobalt-substituted polyoxometalates having cobalt cores exhibiting cubane or dicubane topologies have been synthesized and characterized by IR, elemental analysis, electrochemistry, UV–vis spectroscopy, X-ray single-crystal analysis, and magnetic studies. The tetracobalt(II)-substituted polyoxometalate [Co4(OH)3(H2O)6(PW9O34)]4– (1) consists of a trilacunary [B-α-PW9O34]9– unit which accommodates a cubane-like {CoII4O4} core. In the heptacobalt(II,III)-containing polyoxometalates [Co7(OH)6(H2O)6(PW9O34)2]9– (2), [Co7(OH)6(H2O)4(PW9O34)2]n9n– (3), and [Co7(OH)6(H2O)6(P2W15O56)2]15– (4), dicubane-like {CoII6CoIIIO8} cores are encapsulated between two heptadentate [B-α-PW9O34]9– (in…
The Chemistry of the [1,2,3]Triazolo[1,5-a]pyridines: An Update
2010
Publisher Summary This chapter discusses the recent advancement in the chemistry of [1,2,3] triazolo[1,5-a]pyridines. It describes new discoveries in the physical properties and theoretical chemistry, focusing on synthesis of [1,2,3]triazolo[1,5-a]pyridine system, synthesis of novel aryltriazolopyridines, chiral ligands from [1,2,3]triazolo[1,5-a]pyridines, pyridylcarbene formation from triazolopyridines, ring-chain isomerization on [1,2,3]triazolo[1,5-a]pyridines, and novel pyridylcarbonylpyridines. All triazolopyridines have interesting ligand properties to form polynuclear complexes with different metal ions. X-ray single-crystal studies, magnetic, photo-magnetic, and colorimetric measur…
Synthesis, structure, spectral characterization and DNA binding affinity of new water soluble trinuclear copper(II) complexes with partial cubane Cu3…
2015
Two new water soluble trinuclear copper(II) complexes, [Na 6 (H 3 O) 4 ][Cu 3 (cbal) 3 (μ 3 -OH)(H 2 O) 3 ] 4 (ClO 4 ) 6 ·3H 2 O ( 1 ) and [K(H 2 O) 2 ][Cu 3 (cbal) 3 (μ 3 -OH)(H 2 O)]·3.75H 2 O ( 2 ) have been synthesized in good yield via the reaction of an unsymmetrical amino dicarboxylic ligand, N-(2-carboxybenzomethyl)-β-alanine (H 2 cbal), Cu(ClO 4 ) 2 ·6H 2 O and NaOH/K 2 CO 3 in methanol at room temperature. Complexes 1 and 2 have been characterized by elemental analysis, room temperature magnetic susceptibility measurements, FTIR, UV–Vis, mass spectrometry and single crystal X-ray crystallography. Both complexes contain a partial cubane [Cu 3 O 4 ] core consisting of the trinuclear…
La constitución cubana de 2019: un análisis crítico
2019
En julio de 2018, la Asamblea Nacional del Poder Popular (ANPP) de Cuba inició el trámite de discusión de un anteproyecto de nueva Constitución cubana. Entre el 13 de agosto y el 15 de noviembre de 2018, la ANPP convocó una fase de consulta popular entre la ciudadanía destinada a la discusión y recogida de propuestas, previa al debate para su consideración en la cámara y su posterior ratificación en referéndum en febrero de 2019. La nueva Constitución cubana es la concreción jurídico-formal de un proceso constituyente material que viene refundando las relaciones económicas y sociales de la isla desde inicios de la década de los 90 hasta hoy. El presente trabajo analizará cuales han sido est…
Large Magnetic Polyoxometalates Containing the Cobalt Cubane ‘[CoIIICo3II(OH)3(H2O)6–m(PW9O34)]3− (m = 3 or 5) as a Subunit
2018
A synthetic procedure is presented to construct new magnetic polyoxometalates (POMs) containing one or two subunits of ‘[CoIIICo3II(OH)3(H2O)6−m(PW9O34)]3−' (m = 3 or 5). The substitution of the water ligands present in these subunits by oxo or hydroxo ligands belonging to other POM fragments, gives rise to four, larger POM anions: [Co7(OH)6(H2O)6(PW9O34)2]9− (2), [Co7(OH)6(H2O)4(PW9O34)2]n9n- (2′), [Co11(OH)5(H2O)5(W6O24)(PW9O34)3]22− (3) and [{Co4(OH)3(H2O)(PW9O34)}2{K⊂(H2W12O41)2}{Co(H2O)4}2]17− (4). The crystal structures, magnetic characterization and stabilities in aqueous solutions of these POM derivatives are also presented.
A tetranuclear cubane-like nickel(II) complex with a tridentate salicylideneimine Schiff base ligand: tetrakis[μ3-4-methyl-N-(2-oxidophenyl)salicylid…
2016
The tetranuclear title complex, [Ni4(C14H11NO2)4(CH3OH)4]·0.8CH3OH, has a distorted cubane topology shaped by four Schiff base ligands. The cubane [Ni4(μ3-O4)] core is formedviathe O atoms from the Schiff base ligands. The octahedrally coordinated NiIIions occupy alternating vertices of the cube. Each NiIIion is coordinated by oneO,N,O′-tridentate dianionic ligand, two O atoms of oxidophenyl groups from adjacent ligands and the O atom of a coordinating methanol molecule. The cubane core is stabilizedviaan intramolecular O—H...O hydrogen bond between the hydroxy group of the coordinating methanol molecules and the phenolate O atom of the aldehyde Schiff base fragment. Additional stabilizatio…