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Synthesis, cytotoxicity, antibacterial and antileishmanial activities of imidazolidine and hexahydropyrimidine derivatives

De Carvalho, Gustavo S. G.; Dias, Rafael M. P.; Pavan, Fernando R.; Leite, Clarice Q. F.; Silva, Vânia L.; Diniz, Cláudio G.; De Paula, Daniela T. S.; Coimbra, Elaine S.; Retailleau, Pascal; Da Silva, Adilson D.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 351-359
ENG
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); This paper describes the synthesis and in vitro biological activities of imidazolidine and hexahydropyrimidine derivatives against bacteria (Escherichia coli, Staphylococcus aureus and Mycobacterium tuberculosis) and Leishmania protozoa. Out of sixteen heterocyclic derivatives tested, none were cytotoxic against mammalian cells. The compounds showed significant bacterial effects and leishmanicidal activity. Compounds 4a and 4c were active against S. aureus and E. coli, respectively. Compounds 3a-3f, 4h and 4i presented promising results against M. tuberculosis, with MIC values ranging from 12.5 to 25.0 μg/mL, comparable to the first and second line drugs used to treat tuberculosis. Compounds 4a, 4c and 4e were active against L major. Three of them were structurally characterized by single-crystal X-ray diffraction. © 2013 Bentham Science Publishers.

Síntese e caracterização de redes metalo-orgânicas de fármacos

Martins, Marta Sofia Pranto
Fonte: Instituto Politécnico de Lisboa Publicador: Instituto Politécnico de Lisboa
Tipo: Dissertação de Mestrado
Publicado em /07/2013 POR
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O desenvolvimento de novas formas de princípios farmacologicamente ativos (PFA) é um tema que tem recebido especial atenção nos últimos anos, tentando melhorar as propriedades físico-químicas e o desempenho do fármaco. A sua coordenação a metais permite não só realizar com êxito essa tarefa mas desenvolver novos materiais bio-inspirados, Redes Metalo-Orgânicas (RMOs), que podem ser utilizadas em novos métodos de transporte e libertação dos fármacos. Após um rastreio de vários PFAs disponíveis, selecionaram-se aqueles que, numa primeira análise, se mostraram mais promissores na coordenação a diferentes metais de baixa toxicidade: a dapsona, o ácido nalidíxico e o ácido azelaico. Novos compostos e redes de coordenação foram desenvolvidos ao longo deste trabalho, através de métodos sintéticos clássicos, a síntese solvotérmica, e técnicas amigas do ambiente, a síntese mecanoquímica. Foi também efetuado um estudo de polimorfismo no ácido azelaico. Quando possível, os compostos foram caracterizados por técnicas de difração de raios-X de pós e de monocristal, calorimetria diferencial de varrimento, microscopia de placa quente e espectroscopia de infravermelho. Os compostos obtidos com os três PFA e diferentes metais mostraram ser bastante promissores...

Combined experimental powder X-ray diffraction and DFT data to obtain the lowest energy molecular conformation of friedelin

Oliveira,Djalma Menezes de; Mussel,Wagner da Nova; Duarte,Lucienir Pains; Silva,Grácia Divina de Fátima; Duarte,Hélio Anderson; Gomes,Elionai Cassiana de Lima; Guimarães,Luciana; Vieira Filho,Sidney A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
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Friedelin molecular conformers were obtained by Density Functional Theory (DFT) and by ab initio structure determination from powder X-ray diffraction. Their conformers with the five rings in chair-chair-chair-boat-boat, and with all rings in chair, are energy degenerated in gas-phase according to DFT results. The powder diffraction data reveals that rings A, B and C of friedelin are in chair, and rings D and E in boat-boat, conformation. The high correlation values among powder diffraction data, DFT and reported single-crystal data indicate that the use of conventional X-ray diffractometer can be applied in routine laboratory analysis in the absence of a single-crystal diffractometer.

Synthesis and characterization of heptacoordinated tin(IV) complexes. X-ray crystal structure of [nBu2Sn(dappt)]·(Me 2CO)0.5 [H2dappt = 2,6-diacetylpyridine bis(4-phenylthiosemicarbazone)]

Sousa,Gerimário F. de; Deflon,Victor M.; Niquet,Elke; Abras,Anuar
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2001 EN
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The reactions of the 2,6-diacetylpyridine bis(4-phenylthiosemicarbazone) ligand, H2dappt, with R4-mSnXm (m = 2, 3; R = Me, nBu, Ph and X = Cl) led to the formation of four new heptacoordinated organotin(IV) complexes, which were characterized by microanalyses and by IR and Mössbauer spectroscopies. The n-butyl derivative [nBu2Sn(dappt)]·(Me 2CO)0.5 was also analyzed by a single crystal X-ray diffraction study. It crystallized in the monoclinic system with a space group C2/c, with a = 36.164(14), b = 9.7050(15), c = 26.194(11) Å, beta = 132.00(2)º, Z = 8. The structure determination revealed a neutral complex of Sn(IV) in a distorted pentagonal bipyramidal (PBP) geometry, with the equatorial plane defined by the SNNNS donor system of the ligand and with the two n-butyl groups in the axial positions. Also, a correlation between Mössbauer and X-ray data based on the point-charge model is discussed.

Structural study and fluorescent property of a novel organic microporous crystalline material

Cheng,Zhao; Yang,Bingqin; Yang,Meipan; Zhang,Binglin
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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75.67%
A novel microporous organic material [(2-{2-[2-(bis-methoxycarbonylmethylamino)phenoxy]ethoxy}-4-benzimidazole-phenyl)methoxycarbonylmethylamino]acetic acid methyl ester 6 was synthesized and characterized by single crystal X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), electron spray ionization-mass spectrometry (ESI-HRMS), X-ray powder diffraction (PXRD), ¹H and 13C NMR. 6 crystallizes in the centrosymmetric monoclinic space group C2/c, with unit cell parameters a = 35.648(3) Å, b = 14.3240(12) Å, c = 15.3693(13) Å, α= 90.00, β= 94.8190(10), γ = 90.00, V = 7820.16 ų and Z = 8 at 296(2) K. As indicated by crystal packing, the molecular conjugation planes arrange along the c axis to form micropores due to the hydrogen bonds. In addition, the fluorescent spectrum and luminescence lifetime were studied for 6.

Redetermination of LaZn5 based on single crystal X-ray diffraction data

Oshchapovsky, Igor; Zelinska, Oksana; Rozdzynska-Kielbik, Beata; Pavlyuk, Volodymyr
Fonte: International Union of Crystallography Publicador: International Union of Crystallography
Tipo: Artigo de Revista Científica
Publicado em 03/12/2011 EN
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The crystal structure of the already known binary title compound LaZn5 (lanthanum penta­zinc) (space group P6/mmm, Pearson symbol hP6, CaCu5 structure type) has been redetermined from single-crystal X-ray diffraction data. In contrast to previous determinations based on X-ray powder data [Nowotny (1942). Z. Metallkd. 34, 247–253; de Negri et al. (2008). Inter­metallics, 16, 168–178], where unit-cell parameters and assignment of the structure type were reported, the present study reveals anisotropic displacement parameters for all atoms. The crystal structure consists of three crytallographically distinct atoms. The La atom (Wyckoff site 1a, site symmetry 6/mmm) is surrounded by 18 Zn atoms and two La atoms. The coordination polyhedron around one of the Zn atoms (Wyckoff site 2c, site symmetry -6m2) is an icosa­hedron made up from three La and nine Zn atoms. The other Zn atom (Wyckoff site 3g, site symmetry mmm) is surrounded by four La and eight Zn atoms. Bonding between atoms is explored by means of the TB–LMTO–ASA (tight-binding linear muffin-tin orbital atomic spheres approximation) program package. The positive charge density is localized around La atoms, and the negative charge density is around Zn atoms...

The single crystal X-ray structure of β-hematin DMSO solvate grown in the presence of chloroquine, a β-hematin growth-rate inhibitor

Gildenhuys, Johandie; le Roex, Tanya; Egan, Timothy J.; de Villiers, Katherine A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Single crystals of solvated β-hematin were grown from a DMSO solution containing the antimalarial drug chloroquine, a known inhibitor of β-hematin formation. In addition, a kinetics study employing biomimetic lipid-water emulsion conditions was undertaken to further investigate the effect of chloroquine and quinidine on the formation of β-hematin. Scanning electron microscopy shows that the external morphology of the β-hematin DMSO solvate crystals is almost indistinguishable from that of malaria pigment (hemozoin) and single crystal X-ray diffraction confirms the presence of μ-propionato coordination dimers of iron(III) protoporphyrin IX. The free propionic acid functional groups of adjacent dimers hydrogen bond to included DMSO molecules, rather than forming carboxylic acid dimers. The observed exponential kinetics were modeled using the Avrami equation, with an Avrami constant equal to 1. The decreased rate of β-hematin formation observed at low concentrations of both drugs could be accounted for by assuming a mechanism of drug adsorption to sites on the fastest growing face of β-hematin. This behavior was modeled using the Langmuir isotherm. Higher concentrations of drug resulted in decreased final yields of β-hematin, and an irreversible drug-induced precipitation of iron(III) protoporphyrin IX was postulated to account for this. The model permits determination of the equilibrium adsorption constant (Kads). The values for chloroquine (log Kads = 5.55 ± 0.03) and quinidine (log Kads = 4.92 ± 0.01) suggest that the approach may be useful as a relative probe of the mechanism of action of novel antimalarial compounds.

Reinvestigation of trilithium divanadium(III) tris­(orthophosphate), Li3V2(PO4)3, based on single-crystal X-ray data

Kee, Yongho; Yun, Hoseop
Fonte: International Union of Crystallography Publicador: International Union of Crystallography
Tipo: Artigo de Revista Científica
Publicado em 19/01/2013 EN
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85.68%
The structure of Li3V2(PO4)3 has been reinvestigated from single-crystal X-ray data. Although the results of the previous studies (all based on powder diffraction data) are comparable with our redetermination, all atoms were refined with anisotropic displacement parameters in the current study, and the resulting bond lengths are more accurate than those determined from powder diffraction data. The title compound adopts the Li3Fe2(PO4)3 structure type. The structure is composed of VO6 octa­hedra and PO4 tetra­hedra by sharing O atoms to form the three-dimensional anionic framework ∞ 3[V2(PO4)3]3−. The positions of the Li+ ions in the empty channels can vary depending on the synthetic conditions. Bond-valence-sum calculations showed structures that are similar to the results of the present study seem to be more stable compared with others. The classical charge balance of the title compound can be represented as [Li+]3[V3+]2[P5+]3[O2−]12.

Single-crystal structure determination of (Mg,Fe)SiO3 postperovskite

Zhang, Li; Meng, Yue; Dera, Przemyslaw; Yang, Wenge; Mao, Wendy L.; Mao, Ho-kwang
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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65.77%
Knowledge of the structural properties of mantle phases is critical for understanding the enigmatic seismic features observed in the Earth’s lower mantle down to the core–mantle boundary. However, our knowledge of lower mantle phase equilibria at high pressure (P) and temperature (T) conditions has been based on limited information provided by powder X-ray diffraction technique and theoretical calculations. Here, we report the in situ single-crystal structure determination of (Mg,Fe)SiO3 postperovskite (ppv) at high P and after temperature quenching in a diamond anvil cell. Using a newly developed multigrain single-crystal X-ray diffraction analysis technique in a diamond anvil cell, crystallographic orientations of over 100 crystallites were simultaneously determined at high P in a coarse-grained polycrystalline sample containing submicron ppv grains. Conventional single-crystal structural analysis and refinement methods were applied for a few selected ppv crystallites, which demonstrate the feasibility of the in situ study of crystal structures of submicron crystallites in a multiphase polycrystalline sample contained within a high P device. The similarity of structural models for single-crystal Fe-bearing ppv (∼10 mol% Fe) and Fe-free ppv from previous theoretical calculations suggests that the Fe content in the mantle has a negligible effect on the crystal structure of the ppv phase.

Redetermination of Dy3Ni from single-crystal X-ray data

Levytskyy, Volodymyr; Babizhetskyy, Volodymyr; Kotur, Bohdan; Smetana, Volodymyr
Fonte: International Union of Crystallography Publicador: International Union of Crystallography
Tipo: Artigo de Revista Científica
Publicado em 26/10/2013 EN
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85.71%
The classification of the title compound, tridysprosium nickel, into the Fe3C (or Al3Ni) structure type has been deduced from powder X-ray diffraction data with lattice parameters reported in a previous study [Lemaire & Paccard (1967 ▶). Bull. Soc. Fr. Mineral. Cristallogr. 40, 311–315]. The current re-investigation of Dy3Ni based on single-crystal X-ray data revealed atomic positional parameters and anisotropic displacement parameters with high precision. The asymmetric unit consists of two Dy and one Ni atoms. One Dy atom has site symmetry .m. (Wyckoff position 4c) and is surrounded by twelve Dy and three Ni atoms. The other Dy atom (site symmetry 1, 8d) has eleven Dy and three Ni atoms as neighbours, forming a distorted Frank–Kasper polyhedron. The coordination polyhedron of the Ni atom (.m., 4c) is a tricapped trigonal prism formed by nine Dy atoms.

Phosphine, isocyanide, and alkyne reactivity at pentanuclear molybdenum/tungsten-iridium clusters

Simpson, Peter V; Randles, Michael D; Gupta, Vivek; Fu, Junhong; Moxey, Graeme J; Schwich, Torsten; Morshedi, Mahbod; Cifuentes, Marie P; Humphrey, Mark G
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica Formato: 13 pages
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The trigonal bipyramidal clusters M2Ir3(μ-CO)3(CO)6(η(5)-C5H5)2(η(5)-C5Me4R) (M = Mo, R = Me 1a, R = H; M = W, R = Me, H) reacted with isocyanides to give ligand substitution products M2Ir3(μ-CO)3(CO)5(CNR′)(η(5)-C5H5)2(η(5)-C5Me4R) (M = Mo, R = Me, R′ = C6H3Me2-2,6 3a; M = Mo, R = Me, R′ = (t)Bu 3b), in which core geometry and metal atom locations are maintained, whereas reactions with PPh3 afforded M2Ir3(μ-CO)4(CO)4(PPh3)(η(5)-C5H5)2(η(5)-C5Me4R) (M = Mo, R = Me 4a, H 4c; M = W, R = Me 4b, H), with retention of core geometry but with effective site-exchange of the precursors’ apical Mo/W with an equatorial Ir. Similar treatment of trigonal bipyramidal MIr4(μ-CO)3(CO)7(η(5)-C5H5)(η(5)-C5Me5) (M = Mo 2a, W 2b) with PPh3 afforded the mono-substitution products MIr4(μ-CO)3(CO)6(PPh3)(η(5)-C5H5)(η(5)-C5Me5) (M = Mo 5a; M = W 5b), and further reaction of the molybdenum example 5a with excess PPh3 afforded the bis-substituted cluster MoIr4(μ3-CO)2(μ-CO)2(CO)4(PPh3)2(η(5)-C5H5)(η(5)-C5Me5) (6). Reaction of 1a with diphenylacetylene proceeded with alkyne coordination and C≡C cleavage, affording Mo2Ir3(μ4–η(2)-PhC2Ph)(μ3-CPh)2(CO)4(η(5)-C5H5)2(η(5)-C5Me5) (7a) together with an isomer. Reactions of 2a and 2b with PhC≡CR afforded MIr4(μ3–η(2)-PhC2R)(μ3-CO)2(CO)6(η(5)-C5H5)(η(5)-C5Me5) (M = Mo...

Préparation de réseaux organiques covalents monocristallins par polymérisation de composés polynitroso aromatiques.

Beaudoin, Daniel
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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65.78%
La construction modulaire est une stratégie émergente qui permet la fabrication de matériaux ordonnés à l’échelle atomique. Elle consiste en l’association programmée de sous-unités moléculaires via des sites réactifs judicieusement sélectionnés. L’application de cette stratégie a d’ores et déjà produit des matériaux aux propriétés remarquables, notamment les réseaux organiques covalents, dans lesquels des atomes de carbone et d’autres éléments légers sont liés de manière covalente. Bien que des matériaux assemblés par des interactions non-covalentes puissent être préparés sous la forme de monocristaux macroscopiques de cette façon, ceci n’était pas possible dans le cas des réseaux organiques covalents. Afin de pallier cette lacune, nous avons choisi d’étudier des réactions de polymérisation réversibles ayant lieu par un mécanisme d’addition. En effet, l’hypothèse de départ de cette thèse suppose qu’un tel processus émule le phénomène de cristallisation classique – régi par des interactions non-covalentes – et favorise la formation de monocristaux de dimensions importantes. Pour tester la validité de cette hypothèse, nous avons choisi d’étudier la polymérisation des composés polynitroso aromatiques puisque la dimérisation des nitrosoarènes est réversible et procède par addition. Dans un premier temps...

Crystal chemistry of the jarosite group of minerals - solid solution and atomic structures

Basciano, Laurel C.
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 3083148 bytes; application/pdf
EN; EN
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75.75%
The jarosite group of minerals is part of the alunite supergroup, which consists of more than 40 different mineral species that have the general formula AB3(TO4)2(OH, H2O)6. There is extensive solid-solution in the A, B and T sites within the alunite supergroup. Jarosite group minerals are common in acid mine waste and there is evidence of jarosite existing on Mars. Members of the jarosite - natrojarosite – hydronium jarosite (K,Na, H3O)Fe3(SO4)2(OH)6 solid-solution series were synthesized and investigated by Rietveld analysis of X-ray powder diffraction data. The synthesized samples have full iron occupancy, where in many previous studies there was significant vacancies in the B site. Well-defined trends can be seen in the unit cell parameters, bond lengths A – O and Fe - O across the solid-solution series in the synthetic samples. Based on unit cell parameters many natural samples appear to have full iron occupancy and correlate well with the synthetic samples from this study. In addition, the infrared spectra of the samples were analyzed. The atomic structure of ammoniojarosite, (NH4)Fe3(SO4)2(OH)6, has been solved using single-crystal X-ray diffraction to wR 3.64% and R 1.4%. The atomic coordinates of the hydrogen atoms of the NH4 group have been located and it was found that the ammonium group has two different orientations with equal probability. Samples in the ammoniojarosite – hydronium jarosite solid-solution series were synthesized and analyzed using powder X-ray diffraction and Rietveld refinement. It was found that an incomplete solid-solution series exists between jarosite and plumbojarosite...

Estudo Cristaloquimico de dois derivados Naftoquinônicos pela aplicação de difração de raios X: 4,5-Diidro-6,6-Dimetil-6h-2-(3 -Metilfenil)-Furan[B-4,3] Nafto[1,2-D] Imidazol (Nppn3171) E 4,5-Diidro-6,6-Dimetil 6h-2 (Fenil)-Piran [B-4,3]-Nafto[1,2-D]-Imidazol (Nppn3073); Crystallo chemical study of two naphtoquinone derivativis by the application of x-ray diffraction: 4,5-dihydro-6,6-dimethyl-6H-2-(3 -methylphenyl)-furan[B-4,3] napht [1,2-D] imidazale (NPPN3171) and 4,5-dihydro-6,6-dimethyl-6H-2 (phenyl)-piran [B-4,3] napht [1,2-D] imidazale (NPPN3073)

Silva, José Atalvanio da
Fonte: Universidade Federal de Alagoas; BR; Química; Biotecnologia; Programa de Pós-Graduação em Química e Biotecnologia; UFAL Publicador: Universidade Federal de Alagoas; BR; Química; Biotecnologia; Programa de Pós-Graduação em Química e Biotecnologia; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
65.8%
This study aimed to perform the collection of the intensities of diffracted X-ray beam, solving the crystal structures, refine the collected data to compare the molecular structures obtained, the proposals submitted by the group of the Pesquisa em Produtos Naturais (NPPN) da Universidade Federal do Rio de Janeiro (UFRJ) and to characterize the crystal packing identifying possible interactions of hydrogen. In Chapter I, has an introduction to organic compounds as potential pharmaceutical and distribution of Chagas disease in the world and in Brazil, highlighting data from the State of Alagoas. In Chapter II presents a theoretical foundation of X-rays as well as the concept of crystal, followed by Chapter III, using materials and methods and in Chapter IV, are the results and discussions. The compounds studied in this work were 4,5-dihydro-6 ,6-dimethyl-6H-2-(3'-methylphenyl)-furan [B-4,3] naphtha [1,2-D] Imidazole (NPPN3171) and 4,5-dihydro-6 ,6-dimethyl-6H-2 (phenyl)-piran [B-4, 3]-naphtha [1,2-D]-imidazole (NPPN3037). The single crystal samples were courtesy of NPPN/ UFRJ, in the person of Professor Antonio Ventura Pinto. The crystals were selected, glued on glass fibers and set the goniometric head. Data were collected using an automatic diffractometer Kappa CCD. The structures were solved using the software package contained in the WinGX v1.70.01. The compound NPPN3171crystallizes in monoclinic crystal system...

In-situ X-ray diffraction snapshotting: Determination of the kinetics of a photodimerization within a single crystal

Hu, Fei-Long; Wang, Shu-Long; Lang, Jian-Ping; Abrahams, Brendan F.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 29/10/2014 EN
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65.81%
In a single-crystal-to-single-crystal (SCSC) transformation, a preformed three-dimensional coordination polymer,[Ni3(oba)2(bpe)2(SO4)(H2O)4]·H2O (H2oba = 4,4′-oxydibenzoic acid; bpe = (E)-1,2-di(pyridin-4-yl)ethane) (1), was shown to undergo a [2+2] cycloaddition reaction upon exposure to UV irradiation. The kinetics of this reaction were followed by taking “snapshots” of the solid state transformation using in situ single crystal X-ray crystallography; a first order process was indicated. The reaction rate was influenced by many factors such as the separation of the sample from the UV light source, the heat produced by the UV irradiation, the light flux of the UV lamp used, the size of the single-crystal and the powder samples. The investigation of the kinetics was complemented by 1H NMR studies. The results clearly demonstrate that in situ single-crystal X-ray diffraction is able to provide useful insights into the gradual formation of the photoproducts and the reaction processes. The work also offers a clear indication that it is possible to use the technique to study the kinetics of other photocycloaddition reactions and SCSC processes in general.

Estudo Cristaloquimico de dois derivados Naftoquinônicos pela aplicação de difração de raios X: 4,5-Diidro-6,6-Dimetil-6h-2-(3 -Metilfenil)-Furan[B-4,3] Nafto[1,2-D] Imidazol (Nppn3171) E 4,5-Diidro-6,6-Dimetil 6h-2 (Fenil)-Piran [B-4,3]-Nafto[1,2-D]-Imidazol (Nppn3073); Crystallo chemical study of two naphtoquinone derivativis by the application of x-ray diffraction: 4,5-dihydro-6,6-dimethyl-6H-2-(3 -methylphenyl)-furan[B-4,3] napht [1,2-D] imidazale (NPPN3171) and 4,5-dihydro-6,6-dimethyl-6H-2 (phenyl)-piran [B-4,3] napht [1,2-D] imidazale (NPPN3073)

Silva, José Atalvanio da
Fonte: Universidade Federal de Alagoas; BR; Química; Biotecnologia; Programa de Pós-Graduação em Química e Biotecnologia; UFAL Publicador: Universidade Federal de Alagoas; BR; Química; Biotecnologia; Programa de Pós-Graduação em Química e Biotecnologia; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
65.8%
This study aimed to perform the collection of the intensities of diffracted X-ray beam, solving the crystal structures, refine the collected data to compare the molecular structures obtained, the proposals submitted by the group of the Pesquisa em Produtos Naturais (NPPN) da Universidade Federal do Rio de Janeiro (UFRJ) and to characterize the crystal packing identifying possible interactions of hydrogen. In Chapter I, has an introduction to organic compounds as potential pharmaceutical and distribution of Chagas disease in the world and in Brazil, highlighting data from the State of Alagoas. In Chapter II presents a theoretical foundation of X-rays as well as the concept of crystal, followed by Chapter III, using materials and methods and in Chapter IV, are the results and discussions. The compounds studied in this work were 4,5-dihydro-6 ,6-dimethyl-6H-2-(3'-methylphenyl)-furan [B-4,3] naphtha [1,2-D] Imidazole (NPPN3171) and 4,5-dihydro-6 ,6-dimethyl-6H-2 (phenyl)-piran [B-4, 3]-naphtha [1,2-D]-imidazole (NPPN3037). The single crystal samples were courtesy of NPPN/ UFRJ, in the person of Professor Antonio Ventura Pinto. The crystals were selected, glued on glass fibers and set the goniometric head. Data were collected using an automatic diffractometer Kappa CCD. The structures were solved using the software package contained in the WinGX v1.70.01. The compound NPPN3171crystallizes in monoclinic crystal system...

Lattice and magnetic instabilities in CaFe2As2: A single crystal neutron diffraction study

Goldman, A. I.; Argyriou, D. N.; Ouladdiaf, B.; Chatterji, T.; Kreyssig, A.; Nandi, S.; Ni, N.; Bud'ko, S. L.; Canfield, P. C.; McQueeney, R. J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
75.63%
Neutron diffraction measurements of a high quality single crystal of CaFe2As2 are reported. A sharp transition was observed between the high temperature tetragonal and low temperature orthorhombic structures at TS = 172.5K (on cooling) and 173.5K (on warming). Coincident with the structural transition we observe a rapid, but continuous, ordering of the Fe moments, in a commensurate antiferromagnetic structure is observed, with a saturated moment of 0.80(5)muB/Fe directed along the orthorhombic a-axis. The hysteresis of the structural transition is 1K between cooling and warming and is consistent with previous thermodynamic, transport and single crystal x-ray studies. The temperature onset of magnetic ordering shifts rigidly with the structural transition providing the clearest evidence to date of the coupling between the structural and magnetic transitions in this material and the broader class of iron arsenides.; Comment: submitted to PRB

Single-crystal neutron diffraction study of β-Cs_3(HSO_4)_2[H_(2-x)(S_xP_(1-x)O_4] (x ≃ 0.5) at 15 K

Haile, S. M.; Klooster, W. T.
Fonte: International Union of Crystallography Publicador: International Union of Crystallography
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /06/1999
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65.74%
The structure of β-Cs_3(HSO_4)_2[H_(2-x)(S_xP_(1-x)O_4] has been examined by single-crystal neutron diffraction at 15 K. The compound crystallizes in space group C2/c and contains four formula units in the unit cell, with lattice parameters a = 19.769(9), b = 7.685(2), c = 8.858 (3) Å and β = 100.60 (4)°. Refinement of P, S and H site occupancies indicated that the value of x (in the stoichiometry) is 0.500 (6). This, together with the unit-cell volume of 1322.8(14) Å^3, implies a density of 3.463 Mg m^(-3). The structure contains zigzag rows of XO_4 anions, where X = P or S, that alternate, in a checkerboard fashion, with zigzag rows of Cs cations. Moreover, there is one proton site, H(3), with an occupancy of 0.25 and one X-atom site, X(1), that is occupied by 0.5 P and 0.5 S. These features are in general agreement with a previous X-ray structure determination carried out at 298 K. In contrast to the X-ray study, however, it was found that two different structural models adequately fit the diffraction data. In the first model, the proton vacancies and the P atoms were assumed to be randomly distributed over the H(3) and X(1) sites, respectively, and to have no impact on the local structure. In the second model, several atoms were assigned split occupancies over two neighboring sites...

A combined temperature-dependent electron and single crystal X-ray diffraction study of the fresnoite compound Rb2V4+V25+O8

Withers, Raymond; Hoche, Thomas; Liu, Yun; Esmaeilzadeh, Saeid; Keding, Ralf; Sales, Brian
Fonte: Academic Press Publicador: Academic Press
Tipo: Artigo de Revista Científica
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High-purity Rb2V3O8 has been grown and temperature-dependent electron and single-crystal X-ray diffraction used to carefully investigate its fresnoite-type reciprocal lattice. In contrast to other recently investigated representatives of the fresnoite family of compounds, Rb2V3O8 is not incommensurately modulated with an incommensurate basal plane primary modulation wave vector given by q∼0.3 〈110〉*. A careful low-temperature electron diffraction study has, however, revealed the existence of weak incommensurate satellite reflections characterized by the primitive primary modulation wave vector q1∼0.16c*. The reciprocal space positioning of these incommensurate satellite reflections, the overall (3+1)-d superspace group symmetry, as well as the shapes of the refined displacement ellipsoids determined from single-crystal XRD refinement, are all consistent with their arising from a distinct type of condensed rigid unit modes (RUMs) of distortion of the Rb2V3O8 parent structure.

Mixed-metal cluster chemistry XII: isocyanide derivatives of [CpWIr3(CO)11]; X-ray crystal structure of [CpWIr3(CO)9(CNC6H3Me2-2,6)2]

Waterman, Susan; Humphrey, Mark; Hockless, David
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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Reactions of [CpWIr3(CO)11] (1) with stoichiometric amounts of isocyanides afford the clusters [CpWIr3(CO)11-n(CNR)n] [R = Xy (C6H3Me2-2,6), n = 1 (2), 2 (3), 3 (4); R = tBu, n = 1 (5), 2 (6), 3 (7)] in good to excellent yields (47-63%). The products exhibit ligand fluxionality in solution, with the 13C-NMR spectra of 4-6 revealing that the carbonyls are undergoing fast exchange at 143 K. A single-crystal X-ray study of [CpWIr3(CO)9(CNXy)2] (3) reveals that the coordination sphere of the cluster has an all-terminal ligand geometry, the first for a ligand substituted derivative of 1. The two iridium-ligated 2,6-dimethylphenylisocyanide ligands are coordinated to the same iridium vertex, the second example of this coordination geometry for a transition metal cluster.