RESUMO
The crystal structure of the dimeric title compound, C(19)H(22)O(5), is dominated by a head-to-head hydrogen-bonding interaction between centrosymmetrically related carboxyl groups in each monomer. The result is a dimeric axis of unusual length (ca 34 A), but still shorter than what could be expected for a fully extended chain, owing to two turning points in the oligoethoxy ends. This allows for an explanation of the structure of the smectic mesophase exhibited by this compound and at the same time fully validates former geometric estimations based on PM3 calculations.
RESUMO
Three isostructural Cu 2Ln 2 1-D polymers [Cu 2Ln 2L 10(H 2O) 4.3H 2O] n where Ln = Gd ( 1), Er ( 2), and Y ( 3) and HL= trans-2-butenoic acid, were synthesized and characterized by X-ray crystallography, electron paramagnetic resonance, and magnetic measurements. Pairs of alternate Cu 2 and Ln 2 dinuclear units are combined into a linear array by a set of one covalent eta (2):eta (1):mu 2 carboxylate oxygen and two H bonds, at Cu...Ln distances of ca. 4.5 A. These units exhibit four eta (1):eta (1):mu 2 and two eta (2):eta (1):mu 2 carboxylate bridges, respectively. Magnetic measurements between 2 and 300 K, fields B 0 = mu 0 H between 0 and 9 T, and electron paramagnetic resonance (EPR) measurements at the X-band and room temperature are reported. The magnetic susceptibilities indicate bulk antiferromagnetic behavior of the three compounds at low temperatures. Magnetization and EPR data for 1 and 3 allowed evaluation of the exchange couplings between both Cu and Gd ions in their dinuclear units and between Cu and Gd neighbor ions in the spin chains. The data for the isolated Cu 2 units in 3 yield g || = 2.350 and g [symbol: see text] = 2.054, J Cu-Cu = -338 (3) cm (-1) for the exchange coupling [ H ex(1,2) = - J 1-2 S1 x S2], and D 0 = -0.342 (0.003) cm (-1) and E 0 = 0.003 (0.001) cm (-1) for the zero-field-splitting parameters of the triplet state arising from anisotropic spin-spin interactions. Considering tetranuclear blocks Gd-Cu-Cu-Gd in 1, with the parameters for the Cu 2 unit obtained for 3, we evaluated ferromagnetic interactions between Cu and Gd neighbors, J Cu-Gd = 13.0 (0.1) cm (-1), and between Gd ions in the Gd 2 units, J Gd-Gd = 0.25 (0.02) cm (-1), with g Gd = 1.991. The bulk antiferromagnetic behavior of 1 is a consequence of the antiferromagnetic coupling between Cu ions and of the magnitude, |J Cu-Gd|, of the Cu-Gd exchange coupling. Compound 2 displays a susceptibility peak at 15 K that may be interpreted as the combined result from antiferromagnetic couplings between Er (III) ions in Er 2 units and their coupling with the Cu 2 units.
Assuntos
Cobre/química , Crotonatos/química , Elementos da Série dos Lantanídeos/química , Polímeros/química , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Ligação de Hidrogênio , Ligantes , Magnetismo , Modelos Químicos , Modelos Moleculares , Compostos Organometálicos/químicaRESUMO
Three analogs of neuroactive steroids were prepared (4-6) in which 1,11- or 11,19-oxygen bridges give a constrained conformation. Their 3D structures were obtained by ab initio calculations and in the case of 3alpha-hydroxy-11,19-epoxypregn-4-ene-20-one (4), confirmed by X-ray analysis. Biological activity of the synthetic steroids was assayed in vitro using t-[(3)H]butylbicycloorthobenzoate as radiolabeled ligand for the GABA(A) receptor. The activity of compound 4 was similar to that of allopregnanolone (1). 1alpha,11alpha-Epoxypregnanolone (6) was more active than pregnanolone (2).
Assuntos
Neurônios/efeitos dos fármacos , Oxigênio/química , Receptores de GABA-A/metabolismo , Esteroides/síntese química , Esteroides/farmacologia , Animais , Masculino , Modelos Moleculares , Estrutura Molecular , Ratos , Ratos Sprague-Dawley , Esteroides/químicaRESUMO
The new compound [Ru(bpy)(tpm)NO](ClO4)3 [tpm = tris(1-pyrazolyl)methane; bpy = 2,2'-bipyridine] has been prepared in a stepwise procedure that involves the conversion of [Ru(bpy)(tpm)Cl]+ into the aqua and nitro intermediates, followed by acidification. The diamagnetic complex crystallizes to exhibit distorted octahedral geometry around the metal, with the Ru-N(O) bond length 1.774(12) A and the RuNO angle 179.1(12) degrees , typical for a {RuNO}6 description. The [Ru(bpy)(tpm)NO]3+ ion (I) has been characterized by 1H NMR and IR spectroscopies (nu(NO) = 1959 cm(-1)) and through density functional theory calculations. Intense electronic transitions in the 300-350-nm region are assigned through time-dependent (TD)DFT as intraligand pi --> pi for bpy and tpm. The dpi --> pi(bpy) metal-to-ligand charge-transfer transitions appear at higher energies. Aqueous cyclic voltammetric studies show a reversible wave at 0.31 V (vs Ag/AgCl, 3 M Cl-), which shifts to 0.60 V in MeCN, along with the onset of a wave of an irreversible process at -0.2 V. The waves are assigned to the one- and two-electron reductions centered at the NO ligand, leading to species with {RuNO}(7) and {RuNO}(8) configurations, respectively. Controlled potential reduction of I in MeCN led to the [Ru(bpy)(tpm)NO]2+ ion (II), revealing a significant downward shift of nu(NO) to 1660 cm(-1) as well as changes in the electronic absorption bands. II was also characterized by electron paramagnetic resonance, showing an anisotropic signal at 110 K that arises from an S = 1/2 electronic ground state; the g-matrix components and hyperfine coupling tensor resemble the behavior of related {RuNO}7 complexes. Both I and II were characterized through their main reactivity modes, electrophilic and nucleophilic, respectively. The addition of OH- into I generated the nitro complex, with k(OH) = 3.05 x 10(6) M(-1) s(-1) (25 degrees C). This value is among the highest obtained for related nitrosyl complexes and correlates with ENO+/NO, the one-electron redox potential. Complex II is a robust species toward NO release, although a conversion to I was observed in the presence of O2. This reaction afforded a second-order rate law with k = 3.5 M(-1) s(-1) (25 degrees C). The stabilization of the NO radical complex is attributed to the high positive charge of the precursor and to the geometrical and electronic structure as determined by the neutral tpm ligand.
Assuntos
2,2'-Dipiridil/química , Metano/análogos & derivados , Rutênio/química , Cristalografia por Raios X , Eletroquímica , Espectroscopia de Ressonância de Spin Eletrônica , Metano/química , Conformação Molecular , Óxidos de Nitrogênio/química , Pirazóis/químicaRESUMO
Sulfur-bridged pregnanes 6,19-epithioprogesterone, 21-hydroxy-6,19-epithioprogesterone, and the corresponding sulfoxides and sulfones were synthesized and tested as blockers of the immunosuppresive activity of dexamethasone in rat thymocytes. A new one-pot procedure is described for the preparation of 6,19-epithioprogesterone and related compounds by iodocyclization of a 19-sulfanylpregn-5-ene. Antiimmunosuppresive activity was evaluated by the ability of the different steroids to block dexamethasone-mediated apoptosis in thymocytes and dexamethasone-mediated inhibition of the NFkappa-B transcription factor activity. DNA fragmentation and annexin V-FITC positive cells were taken as parameters of apoptosis whereas NFkappa-B activity was tested by the expression of the reporter vector kappaB-luciferase by TNF-alpha in Hela cells. 21-Hydroxy-6,19-epithioprogesterone S,S-dioxide had improved activity in both parameters, while 21-hydroxy-6,19-epithioprogesterone had improved activity only in blocking dexamethasone-induced programmed cell death.
Assuntos
Desoxicorticosterona/análogos & derivados , Glucocorticoides/antagonistas & inibidores , Tolerância Imunológica/efeitos dos fármacos , Progesterona/análogos & derivados , Progesterona/síntese química , Sulfetos/síntese química , Animais , Apoptose/efeitos dos fármacos , Células COS , Chlorocebus aethiops , Desoxicorticosterona/síntese química , Desoxicorticosterona/farmacologia , Dexametasona/farmacologia , Células HeLa , Humanos , Técnicas In Vitro , Masculino , Camundongos , Conformação Molecular , Estrutura Molecular , NF-kappa B/antagonistas & inibidores , Progesterona/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Progesterona/antagonistas & inibidores , Receptores de Progesterona/genética , Estereoisomerismo , Relação Estrutura-Atividade , Sulfetos/farmacologia , Timo/citologia , Timo/efeitos dos fármacos , Fator de Necrose Tumoral alfa/fisiologiaRESUMO
The bis-pyridine tridentate ligands (6-R-2-pyridylmethyl)-(2-pyridylmethyl) benzylamine (RDPMA, where R = CH(3), CF(3)), (6-R-2-pyridylmethyl)-(2-pyridylethyl) benzylamine (RPMPEA, where R = CH(3), CF(3)), and the bidentate ligand di-benzyl-(6-methyl-2-pyridylmethyl)amine (BiBzMePMA) have been synthesized and their copper(I) complexes oxidized in a methanol solution to afford self-assembled bis-micro-methoxo-binuclear copper(II) complexes (1, 2, 4, 6) or hydroxo- binuclear copper(II) complexes (3). Oxidation of the nonsubstituted DPMA (R = H) in dichloromethane gives a chloride-bridged complex (5). The crystal structures for [Cu(MeDPMA)(MeO)](2)(ClO(4))(2) (1), [Cu(RPMPEA)(MeO)](2)(ClO(4))(2) (for 2, R= Me, and for 4, R = CF(3)), [Cu(BiBzMePMA)(MeO)](2)(ClO(4))(2) (6), [Cu(FDPMA)(OH)](2)(ClO(4))(2) (3), and [Cu(DPMA)(Cl)](2)(ClO(4))(2) (5) have been determined, and their variable-temperature magnetic susceptibility has been measured in the temperature range of 10-300 K. The copper coordination geometries are best described as square pyramidal, except for 6, which is square planar, because of the lack of one pyridine ring in the bidentate ligand. In 1-4 and 6, the basal plane is formed by two pyridine N atoms and two O atoms from the bridging methoxo or hydroxo groups, whereas in 5, the bridging Cl atoms occupy axial-equatorial sites. Magnetic susceptibility measurements show that the Cu atoms are strongly coupled antiferromagnetically in the bis-methoxo complexes 1, 2, 4, and 6, with -2J > 600 cm(-)(1), whereas for the hydroxo complex 3, -2J = 195 cm(-)(1) and the chloride-bridged complex 5 shows a weak ferromagnetic coupling, with 2J = 21 cm(-)(1) (2J is an indicator of the magnetic interaction between the Cu centers).
Assuntos
Cobre/química , Compostos Organometálicos , Cristalografia por Raios X , Ligantes , Magnetismo , Modelos Químicos , Estrutura Molecular , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Oxirredução , TemperaturaRESUMO
Azorella cryptantha yielded the diterpenes, azorellolide and the dihydroderivative, dihydroazorellolide, together with the known yaretol and 1alpha,10beta,4beta,5alpha-diepoxy-7alpha-germacran-6beta-ol. Both possess a carbon skeleton type that may originate from rearrangement of the mulinane skeleton.
Assuntos
Apiaceae/química , Diterpenos/isolamento & purificação , Diterpenos/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estrutura MolecularRESUMO
We report the structure and the magnetic properties of a cobalt(II) compound with the amino acid l-threonine, Co(C(4)H(8)NO(3))(2)(H(2)O)(2). It crystallizes in the orthorhombic chiral space group C222(1), with a = 5.843(5) A, b = 10.120(10) A, c = 22.36(3) A, and Z = 4. The Co(II) ion is in a deformed octahedral environment on a 2-fold symmetry axis parallel to the crystallographic axis b. It is bonded to two threonine molecules in a bidentate fashion, via one oxygen from the carboxylate end and the alpha-amino nitrogen. A water molecule occupies the third independent site. The Co(II) ions are arranged in layers with intralayer and interlayer distances of 5.84 and 11.18 A, respectively. Magnetic measurements data reflect the molecular character of a compound with weak exchange interactions. EPR measurements in polycrystalline and single-crystal samples indicate a distorted axial symmetry around the Co(II) ion, as expected from the structural results. Eigenvalues and eigenvectors of the g tensor are determined. The measured principal g values (5.81, 4.56, and 2.23) reflect a high-spin Co(II) ion, as suggested by the type of ligands and the molecular symmetry. From the incomplete collapse of the hyperfine structure we estimate 0.25 < |J| < 1.2 cm(-1) between neighboring Co(II) ions within a layer, transmitted through H-bonds. A higher limit |J'| < 0.07 cm(-1) is estimated for the exchange interactions between Co(II) ions in neighboring layers. From a global fit of a spin Hamiltonian with spin (3)/(2) to magnetization and EPR data we obtain a zero field splitting delta approximately 231 cm(-1) between the two lowest doublet states. The results are discussed in terms of the molecular and electronic structure of the compound.
Assuntos
Cobalto/química , Compostos Organometálicos/química , Treonina/química , Cristalização , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Ligação de Hidrogênio , Magnetismo , Modelos Moleculares , Conformação Molecular , Treonina/análogos & derivadosRESUMO
Both thiosemicarbazone groups of the derivative 1 of 3-deoxy-D-erythro-hexos-2-ulose underwent, on acetylation, a heterocyclization process to give (5R,5'R)-2,2'-diacetamido-4,4'-di-N-acetyl-5'-(1-deoxy-2,3,4-tri-O-acetyl-D-erythritol-1-yl)-5,5'-bis(1,3,4-thiadiazoline) (2) as a major product. The X-ray diffraction data of a single crystal of 2 indicated the R,R configuration for the stereocenters of the thiadiazoline rings (C-5 and C-5'). In the solid state, 2 adopts a sickle conformation (by clockwise rotation of the C-2-C-3 axis of the sugar chain) which has a S//O 1,3-parallel interaction. In solution, as determined by (1)H NMR spectroscopy which included NOE experiments, a similar sickle conformation was observed. From the reaction mixture of acetylation of 1 was isolated the bis(thiadiazoline) 3 as a by-product. The configuration of the C-5 and C-5' stereocenters of 3 were respectively assigned as S,R by comparison of the physical and spectroscopic data of this compound with those of 2.