Crystal structures and magnetic properties of CuX2(pdmp)2 complexes (X = Br, Cl)

We report the synthesis and the structural and magnetic characterization of two new compounds: dibromobis-(pdmp)copper(II), CuBr2C22H24N4 (1), and dichlorobis(pdmp)copper(II), CuCl2C22H24N4 (2), where pdmp = 1-phenyl-3,5-dimethylpyrazole. The structures were refined by full-matrix least-squares techniques to R1 = 0.0620 and 0.0777, respectively. Compound 1 belongs to the space group P21/n with a = 8.165(5) Å, b = 10.432(3) Å, c = 13.385(4) Å, β = 100.12(4)̊, and Z = 2. Compound 2 belongs to the space group P21/c with a = 8.379(2) Å, b = 22.630(2) Å, c = 12.256(2) Å, β= 98.43(3)°, and Z = 4. It has the same molecular formula as a compound reported previously but a different crystal structure. Detailed single-crystal EPR measurements were performed for single-crystal samples of 1 and 2 at 9 and 35 GHz and at room temperature. The positions and line widths of the EPR lines were measured as a function of the magnetic field orientation in three orthogonal planes. The data were used to study the electronic properties of the copper ions and to evaluate the exchange interactions between them. Our results are discussed in terms of the electronic pathways for superexchange between copper ions, which are provided by the stacking of pyrazole and phenyl rings of neighboring molecules and by hydrogen-halogen bonds. © 1999 American Chemical Society.

Crystal structure of BaBi2Ta2O9

The crystal structure of the Aurivillius compound Bi2BaTa2O9 prepared via the chemical route was determined by direct methods using EXPO97, and refined using the Rietveld method with conventional X-ray diffraction data. The structure was found to be tetragonal (space group I4/mmm, number 139) and Z = 2, isomorphic of the Bi2BaNb2O9 reported by Blake and co-workers in the literature (1997). Two refinements were performed using the two asymmetry functions of DBWS-9807 (release 20/May/99). The unit cell for each case are: a = 3.932 22(6) Å, c = 25.5053(6) Å (RA) and a = 3.93250(7) Å, c = 25.5069(6) Å (RCF). The differences for atom positions, interatomic distances and angles are in the range of one standard deviation. Final agreements factors are: Rwp = 7.97%, S = 1.84, RBragg = 4.28%(RA), Rwp = 7.98%, S = 1.84, RBragg = 4.30% (RCF). The occupancies of Ba and Bi in site 2b were refined but constrained to have their summation equal to 1.00. The same constraints were applied to the Ba and Bi of the 4e site. The results show that on site 2b there are 70% of Ba and 30% of Bi and on the site 4e there are 82% of Bi and 18% of Ba. The charge equilibrium is maintained for one standard deviation of the site occupancies. © 2000 International Centre for Diffraction Data.

Structure and properties of donor doped barium titanate prepared by citrate process

Niobium doped barium titanate was prepared using two procedures. First, doped barium titanate was prepared starting from citrate solutions of all components and second, pure barium titanate powder was obtained from the citrate solutions and after that doped. Besides niobium, a small amount of manganese, as acceptor dopant was added. Phase composition, crystal structure, microstructure and dielectric properties were reported. The influence of powder processing on the properties of niobium doped barium titanate was analysed. The grain growth and the concentration of dopants on the dielectric properties were considered. © 2002 Taylor & Francis.

Electronic structure and magnetic properties of FeWO 4 nanocrystals synthesized by the microwave-hydrothermal method

This communication reports that FeWO 4 nanocrystals were successfully synthesized by the microwave-hydrothermal method at 443 K for 1 h. The structure and shape of these nanocrystals were characterized by X-ray diffraction, Rietveld refinement, and transmission electron microscopy. The experimental results and first principles calculations were combined to explain the electronic structure and magnetic properties. Experimental data were obtained by magnetization measurements for different applied magnetic fields. Theoretical calculations revealed that magnetic properties of FeWO 4 nanocrystals can be assigned to two magnetic orderings with parallel or antiparallel spins in adjacent chains. These factors are crucial to understanding of competition between ferro- and antiferromagnetic behavior. © 2012 Elsevier Inc.

Crystal structure of Jararacussin-I: The highly negatively charged catalytic interface contributes to macromolecular selectivity in snake venom thrombin-like enzymes

Snake venom serine proteinases (SVSPs) are hemostatically active toxins that perturb the maintenance and regulation of both the blood coagulation cascade and fibrinolytic feedback system at specific points, and hence, are widely used as tools in pharmacological and clinical diagnosis. The crystal structure of a thrombin-like enzyme (TLE) from Bothrops jararacussu venom (Jararacussin-I) was determined at 2.48 Å resolution. This is the first crystal structure of a TLE and allows structural comparisons with both the Agkistrodon contortrix contortrix Protein C Activator and the Trimeresurus stejnegeri plasminogen activator. Despite the highly conserved overall fold, significant differences in the amino acid compositions and three-dimensional conformations of the loops surrounding the active site significantly alter the molecular topography and charge distribution profile of the catalytic interface. In contrast to other SVSPs, the catalytic interface of Jararacussin-I is highly negatively charged, which contributes to its unique macromolecular selectivity. © 2012 The Protein Society.

Influence of monomeric and polymeric structure on the physical properties of thermoplastic polyesters derived from hydroxy fatty acids

The physical properties of three vegetable oil derived medium and long chain poly(-hydroxy fatty ester)s (P(Me--OHFA)s), namely poly(-hydroxynonanoate) [P(Me--OHC9)], poly(-hydroxytridecanoate) [P(Me--OHC13)] and poly(-hydroxyoctadecanoate) [P(Me--OHC18)] (n = 8, 12 and 17, respectively), of the [-(CH2)(n)-COO-](x) polyester homologous series are presented. The effect of M-n (M-n 10-40 kg mol(-1)) and n on the crystal structure and thermal and mechanical properties of the P(Me--OHFA)s were investigated by wide-angle X-ray diffraction (WAXD), TGA, DSC, dynamic mechanical analysis (DMA) and tensile analysis and are discussed in the context of the [-(CH2)(n)-COO-](x) polyester homologous series, contrasted with linear polyethylene (PE). For all P(Me--OHFA)s the WAXD data indicated an orthorhombic crystal phase reminiscent of linear PE with crystallinity (X-c = 50%-80%) depending strongly on M-n. The glass transition temperature and Young's modulus for P(Me--OHFA)s increased with X-c. The DSC, DMA and TGA studies for P(Me--OHFA)s (n = 8, 12 and 17) indicated strong correlations between the melting, glass transition and thermal degradation behavior and n. The established predictive structure relationships can be used for the custom engineering of polyester materials suitable for specialty and commodity applications. (c) 2014 Society of Chemical Industry

Elucidating the crystal structure of the antimalarial drug (+/-)-mefloquine hydrochloride: a tetragonal hydrated species

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Local structure and hybridization states in Ba0.9Ca0.1Ti1-xZrxO3 ceramic compounds: Correlation with a normal or relaxor ferroelectric character

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal growth and photoluminescence of europium-doped strontium titanate prepared by a microwave hydrothermal method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reaction of pentacarbonyliron with a nitrogen heterocycle. X-ray crystal structure of bis[(carbonyl)(quinoline-2-thiolate-N,S)]iron(II)

The monomeric compound bis[(carbonyl)(quinoline-2-thiolate-N,S)]iron(II) was synthesized and studied by IR and Mossbauer spectroscopy, cyclic voltammetry and X-ray diffraction. The molecule has two terminal carbonyl groups and two quinoline-2-thiolate anions coordinated as N,S-donor chelates, and the iron atom shows an octahedral coordination geometry.

Crystal structure of mature 2S albumin from Moringa oleifera seeds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of Staphylococcus aureus exfoliative toxin D-like protein: structural basis for the high specificity of exfoliative toxins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Investigation of the relationship between the structure and function of Ts2, a neurotoxin from Tityus serrulatus venom

Scorpion toxins targeting voltage-gated sodium (NaV) channels are peptides that comprise 6076 amino acid residues cross-linked by four disulfide bridges. These toxins can be divided in two groups (a and beta toxins), according to their binding properties and mode of action. The scorpion a-toxin Ts2, previously described as a beta-toxin, was purified from the venom of Tityus serrulatus, the most dangerous Brazilian scorpion. In this study, seven mammalian NaV channel isoforms (rNaV1.2, rNaV1.3, rNaV1.4, hNaV1.5, mNaV1.6, rNaV1.7 and rNaV1.8) and one insect NaV channel isoform (DmNaV1) were used to investigate the subtype specificity and selectivity of Ts2. The electrophysiology assays showed that Ts2 inhibits rapid inactivation of NaV1.2, NaV1.3, NaV1.5, NaV1.6 and NaV1.7, but does not affect NaV1.4, NaV1.8 or DmNaV1. Interestingly, Ts2 significantly shifts the voltage dependence of activation of NaV1.3 channels. The 3D structure of this toxin was modeled based on the high sequence identity (72%) shared with Ts1, another T. serrulatus toxin. The overall fold of the Ts2 model consists of three beta-strands and one a-helix, and is arranged in a triangular shape forming a cysteine-stabilized a-helix/beta-sheet (CSa beta) motif.

Stoichiometry, structure, and transport in the quasi-one-dimensional metal Li0.9Mo6O17

A correlation between lattice parameters, oxygen composition, and the thermoelectric and Hall coefficients is presented for single-crystal Li0.9Mo6O17, a quasi-one-dimensional (Q1D) metallic compound. The possibility that this compound is a compensated metal is discussed in light of a substantial variability observed in the literature for these transport coefficients.

Structure and antimycobacterial activity of the novel organometallic [Pd(C-bzan)(SCN)(dppp)] compound

The organometallic compound [Pd(C-bzan)(SCN)(dppp)] {bzan = N-benzylideneaniline, dppp = 1,3-bis(diphenylphosphino)propane} was synthesized and characterized by elemental analyses, infrared and H-1 and P-31(H-1) NMR spectroscopies. The crystal and molecular structures of the title complex were determined by single-crystal X-ray diffraction techniques. In vitro antimycobacterial evaluation demonstrated that the compound [Pd(C-bzan)(SCN)(dppp)] displayed a MIC of 5.15 mu M, which is superior than those values found for some commonly used anti-TB drugs and other Pd(II) complexes. (C) 2012 Elsevier B.V. All rights reserved.