Search results for "Pyrazine"
showing 10 items of 325 documents
Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing copper(II) complexes
2008
The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(pyim)(tcm)(2)](n) (1), [Cu(bpy)(tcm)(2)](n) (2), [Cu(4)(bpz)(4)(tcm)(8)] (3), {[Cu(terpy)(tcm)].tcm}(n) (4) and {[Cu(2)(tppz)(tcm)(4)].3/2H(2)O}(n) (5) [pyim = 2-(2-pyridyl)imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2''-terpyridine and tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complexes, 1, 2 and 4 are uniform copper(II) chains with single- (1 and 4) and double-(2) micro-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) A (4). Each copper atom …
Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(II) complexes: preparation, X-ray structure and magnetic properties.
2009
The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(2)(tppz)(H(2)O)(2)(CF(3)SO(3))(4)] (1), [Cu(tppz)(CrO(4))](n) x 3nH(2)O (2) and [Cu(4)(tppz)(4)(H(2)O)(4)(MoO(4))(2)](CF(3)SO(3))(4) x 7 H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where…
Mono- and polynuclear complexes of Pt(II) with polypyridyl ligands. Synthesis, spectroscopic and structural characterization and cytotoxic activity.
2007
Abstract An array of poly- and mononuclear complexes of Pt(II) with polypyridyl ligands is reported. The framework complexes [(PtCl 2 ) 2 (bpp) 2 (μ-PtCl 2 )](H 2 O) 2 [bpp = 2,3-bis(2-pyridyl)pyrazine], [PtCl 2 (μ-tptz)PtClNCPh]Cl [tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine], and mononuclear PtCl 2 (NH 2 dpt) [NH 2 dpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole] have been prepared and structurally characterized. Both neutral and ionic complexes are present, with bifunctional and monofunctional Pt(II) moieties, whose size and shape enable them to behave as novel scaffolds for DNA binding. Pt(II) complexes were tested for their biological activity. Cell viability assay and flow cytometric …
Magneto-structural correlations in dirhenium(iv) complexes possessing magnetic pathways with even or odd numbers of atoms
2017
The employment of pyrazine (pyz), pyrimidine (pym) and s-triazine (triz) ligands in ReIV chemistry leads to the isolation of a family of complexes of general formula (NBu4)2[(ReX5)2(μ-L)] (L = pyz, X = Cl (1) or Br (2); L = pym, X = Br (3); L = triz, X = Br (4)). 1-4 are dinuclear compounds where two pentahalorhenium(iv) fragments are connected by bidentate pyz, pym and triz ligands. Variable-temperature magnetic measurements, in combination with detailed theoretical studies, uncover the underlying magneto-structural correlation whereby the nature of the exchange between the metal ions is dictated by the number of intervening atoms. That is, the spin-polarization mechanism present dictates …
Pharmacological activity of PF-904 in guinea pig in vivo, and on human bronchus and neutrophils in vitro.
1997
The effects of PF-904 (4-amino-1-ethyl-6-methylpyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxide), a pyrazinothiadiazine derivative, were examined in guinea-pig airways in vivo, in human isolated bronchus and human polymorphonuclear leukocytes. PF-904 (12.5-200 mg/kg, intraduodenal) reduced bronchoconstriction in response to histamine, arachidonic acid, platelet-activating factor (PAF) and methacholine. PF-904 (50-200 mg/kg) prevented PAF-induced airways hyperreactivity and inhibited antigen-induced bronchoconstriction, airway microvascular leakage and eosinophil lung accumulation, but antigen-induced airways hyperresponsiveness was not reduced. PF-904 (1 microM-1 mM) produced complete inhibiti…
Inhibition of Proteasomal Glucocorticoid Receptor Degradation Restores Dexamethasone-Mediated Stabilization of the Blood–Brain Barrier After Traumati…
2013
To establish the molecular background for glucocorticoid insensitivity, that is, failure to reduce edema formation and to protect blood-brain barrier integrity after acute traumatic brain injury.Controlled animal study.University research laboratory.Male C57Bl/6N mice.Mechanical brain lesion by controlled cortical impact.Our study demonstrates that 1) proteasomal glucocorticoid receptor degradation is established in brain endothelial cells after traumatic brain injury as a form of posttranslational glucocorticoid receptor modification; 2) inhibition of the proteasomal degradation pathway with bortezomib (0.2 mg/kg) in combination with the glucocorticoid dexamethasone (10 mg/kg) by subcutane…
De novo Synthesis of Chemical Defenses in an Aposematic Moth.
2018
Abstract Many animals protect themselves from predation with chemicals, both self-made or sequestered from their diet. The potential drivers of the diversity of these chemicals have been long studied, but our knowledge of these chemicals and their acquisition mode is heavily based on specialist herbivores that sequester their defenses. The wood tiger moth (Arctia plantaginis, Linnaeus, 1758) is a well-studied aposematic species, but the nature of its chemical defenses has not been fully described . Here, we report the presence of two methoxypyrazines, 2-sec-butyl-3-methoxypyrazine and 2-isobutyl-3-methoxypyrazine, in the moths’ defensive secretions. By raising larvae on an artificial diet, …
Pulsed-laser switching in the bistability domain of a cooperative spin crossover compound: a critical study through calorimetry
2015
The photoswitching from the low spin (LS) to high spin (HS) state and the reverse process in the bistability domain of spin crossover (SCO) compounds is a promising function to be used in molecular electronic devices, and evidenced mainly through spectroscopy. The phenomenon, and in particular its mechanism, is however still under debate since some controversial experimental results have been reported. Here we present a calorimetric experimental study of the photoswitching of the [Fe(pyrazine)Pt(CN)4] SCO material by a nanosecond-pulsed green laser. Our results confirm that the single laser pulse of varying energies results in significant LS to HS transformations and show that calorimetry p…
Influence of the pyrazine substituent on the structure and magnetic properties of dicyanamide-bridged cobalt(ii) complexes.
2019
Substituted pyrazines were successfully used to prepare two new coordination polymers of formulas {[Co(dca)2(NH2pyz)2]·H2O}n (1) and [Co3(dca)6(HOpyz)5(H2O)2]n (2) [dca = dicyanamide, NH2pyz = 2-aminopyrazine and HOpyz = 2-hydroxypyrazine] whose structures were determined by single-crystal X-ray crystallography. The structure of 1 consists of a two-dimensional rhombus grid of cobalt(II) ions where the dca ligand adopts the μ1,5 bridging mode with trans-positioned monodentate NH2pyz molecules completing the six-coordination around each metal ion. Compound 2 exhibits a stair-like two-dimensional structure where the intralayer connections are performed by the dca and HOpyz groups exhibiting μ1…
Tetrakis(oxadiazolylphenyl)pyrazines: New St. Andrew's Cross-Shaped Liquid Crystals.
2019
π-Conjugated molecules with the shape of St. Andrew's cross have been synthesized via fourfold Huisgen reaction. Four 2,5-diaryl-1,3,4-oxadiazol arms are attached to a central pyrazine nucleus. These fluorescent stars, when decorated with a rim of eight alkoxy side chains are discotic liquid crystals. Depending on the substitution pattern, the width of the liquid phase varies within a broad range of 25 °C to 250 °C. In their liquid crystalline phase, the molecules assemble in a typical hexagonal columnar supramolecular arrangement.