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991.
Enrique Murillo Yesury Mosquera Tibor Kurtán Gergely Gulyás‐Fekete Veronika Nagy József Deli 《Helvetica chimica acta》2012,95(6):983-988
From the ripe fruits of red mamey (Pouteria sapota), two new carotenoids, 3′‐deoxycapsorubin and 3,3′‐dideoxycapsorubin, were isolated and identified based on their UV/VIS, CD, 1H‐NMR, and mass spectral data. 相似文献
992.
Cristina Serrano María L. Cerrada Marta Fernández-García Jorge Ressia Enrique M. Vallés 《European Polymer Journal》2012,48(3):586-596
Nanocomposites obtained from incorporation of TiO2 nanoparticles in different amounts, ranging from 0.5 to 5 wt.%, into an isotactic polypropylene (iPP) matrix are achieved via a straightforward and cost-effective melting process. These materials exhibit a powerful germicide capability over a wide variety of regular bacteria and other microorganisms widely present in the environment that cause infections and serious illness. The iPP-TiO2 nanocomposites show similar or improved structural characteristics than those of the pure iPP matrix and aspects as important as processability and final mechanical performance seem to be not affected because of the incorporation of these TiO2 nanoparticles. Validation of time–temperature superposition of the molten polymers is observed within the temperature range analyzed. On the other hand, the α polymorph is the one primarily attained for these specimens. Crystallinity and most probable crystallite size are slightly dependent on TiO2 content, both increasing as oxide composition is enlarged. 相似文献
993.
Rosales A Muñoz-Bascón J López-Sánchez C Álvarez-Corral M Muñoz-Dorado M Rodríguez-García I Oltra JE 《The Journal of organic chemistry》2012,77(8):4171-4176
The unprecedented homolytic opening of ozonides promoted and catalyzed by titanocene(III) is reported. This novel reaction proceeds at room temperature under neutral, mild conditions compatible with many functional groups and provides carbon radicals suitable to form C-C bonds via both homocoupling and cross-coupling processes. The procedure has been advantageously exploited for the straightforward synthesis of the natural product brittonin A. 相似文献
994.
The formal [8 + 2] cycloaddition reaction between alkynyl Fischer carbene complexes and tropothione leads to the regioselective formation of novel 3aH-cyclohepta[b]thiophene carbene complexes. Computational DFT calculations indicate that the process proceeds stepwise via antiaromatic zwitterionic intermediates. 相似文献
995.
Molecularly imprinted solid-phase extraction (MISPE) combined with MEKC was used for clean-up, preconcentration and determination of digoxin in the presence of its aglycon digoxin (digoxigenin) in human urine samples. In addition, the use of an in-capillary sample concentration electrophoretic technique by sweeping was investigated to enhance the concentration sensitivity in MEKC. The highly selective, fast and effective sample pretreatment by MISPE along with the preconcentration by sweeping could overcome the low sensitivity of the highly efficient capillary electrophoresis separation with UV detection. The optimization of the variables affecting the separation as well as MISPE conditions procedure was carried out to select the best conditions of selectivity and sensitivity to determine digoxin at low concentration levels in urine. To demonstrate the suitability of the developed method several analytical characteristics (selectivity, linearity, accuracy, precision, and LOD) were evaluated. Satisfactory results were obtained in terms of linearity (r > 0.99), recovery (95.4-96.5% with RSD from 1.3% to 2.6%), precision (RSD from 0.3% to 1.7% for migration times and from 2.1% to 7.3% for corrected peak areas), and sensitivity (LODs of 6 μg/L with 5 mL of sample or 1.2 μg/L with 25 mL). The proposed MISPE-MEKC method was satisfactorily applied to the analysis of spiked human urine samples achieving a concentration factor up to 7500-fold. 相似文献
996.
We have examined the effects of crystallization kinetics of poly(3‐hexylthiophene) and poly[2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno(3,2‐b)thiophene] on microstructure and charge transport. Rapid crystallization increases the density of tie molecules in polythiophenes. As a consequence, ordered regions are better connected resulting in higher charge carrier mobilities. Our results suggest that controlling the crystallization kinetics might be an important factor for maximizing the charge mobility in semicrystalline polythiophene thin films. 相似文献
997.
Costes JP Duhayon C Vendier L Colacio E Mota Ávila AJ Suarez Varela J 《Inorganic chemistry》2012,51(2):1011-1019
The copper template effect allows the preparation of tridentate ligands that chelate copper ions, leaving unoccupied the fourth basal coordination position and at least one axial position of the copper coordination polyhedron. Two such cationic complexes, [LCu](+) and [L(1)Cu](+) (L(-) = 2-{(E)-[(2-aminoethyl)imino]methyl}phenoxo] and L(1-) = 2-{(E)-[(2-aminopropyl)imino]methyl}phenoxo), react with diamagnetic polycyanometalate tectons such as Ni(CN)(4)(2-) or Ag(CN)(2)(-) to yield different neutral 1D complexes. In {[(LCu)(2)Ni(CN)(4)]}(n) (1) the four cyano nitrogen atoms are involved in coordination with copper ions in such a manner that each copper atom is pentacoordinated and linked to two cyano functions that occupy axial and equatorial coordination positions. Two L(1)Cu(+) cationic entities are linked, through their equatorial plane, to two trans cyano groups of the Ni(CN)(4)(2-) tecton in complex [(L(1)Cu)(2)Ni(CN)(4)] (2), the two uncoordinated cyano groups being involved in hydrogen bonds. 2 is a racemate, a S stereoisomer being associated with a R one in each [(L(1)Cu)(2)Ni(CN)(4)] unit. Zigzag Cu-Ag chains are present in [(LCu)Ag(CN)(2)] (3), where the copper centers are pentacoordinated and connected to the cyano groups in an alternate axial-equatorial coordination scheme. A bidimensional structure is developed by interchain argentophilic interactions. In complex 4, {(L(1)CuMeOH)(L(1)Cu)[Ag(CN)(2)](2)}, two L(1)Cu units are connected by a NC-Ag-CN bridge in an equatorial position. These resulting units exhibit argentophilic interactions with [Ag(CN(2))](-) entities that are monocoordinated in the equatorial position to the next unit, ultimately leading to a chain. Weak Cu-Cu magnetic interactions are detected in the four compounds, antiferromagnetic in the case of equatorial-equatorial copper interactions, ferromagnetic for orthogonal interacting copper orbitals (axial-equatorial interactions), while axial-axial bridges are characterized by an absence of interaction. The presence of weak ferromagnetic interactions through large NC-Ni-CN or NC-Ag-CN bridges (Cu···Cu distances larger than 10 ?) furnishes experimental evidence for the existence of next-nearest-neighbor interactions through diamagnetic centers. DFT calculations do confirm the existence of these magnetic transmission pathways through the diamagnetic metal bridge. 相似文献
998.
F. M. Fernández N. Aquino A. Flores‐Riveros 《International journal of quantum chemistry》2012,112(3):823-828
We calculate the ground‐state energy and other physical properties of the hydrogen atom inside a spherical box with an impenetrable wall. We apply the variational method and show that the total, kinetic, and potential energies for the moving nucleus model are greater than those for the case in which the nucleus is clamped at the box center. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
999.
Fernández de Luis R Mesa JL Urtiaga MK Larrea ES Rojo T Arriortua MI 《Inorganic chemistry》2012,51(4):2130-2139
The hydrothermal treatment of Ni(NO(3))(2)·6H(2)O, NaVO(3), and Bpa (1,2-Di(pyridyl)ethane) (C(12)H(12)N(2)) at 120 °C during 3 days leads to green single crystals of the title compound. The single crystal X-ray diffraction reveals that [{Ni(3)(H(2)O)(3)(Bpa)(4)}(V(6)O(18))]·8H(2)O crystallizes in the monoclinic system, P2(1)/c space group, with a = 13.5536 (2), b = 19.0463 (2), c = 27.7435 (3) ?, β = 112.3880 (10)°, V = 6622(3) ?(3), with R1(obs) = 0.0558, wR2(obs) = 0.1359, for 10278 observed reflections. The complexity of the crystal structure is based on different points, as the existence of: both "gauche" and "trans" conformations of the organic ligand, the [V(12)O(36)](-12) cycles, formed by 12 corner-sharing VO(4) tetrahedra, and, finally, the combination of both three-dimensional metal-organic and inorganic substructures, giving rise to a self-catenated highly connected net. The crystallization water molecules are semi-encapsulated in the channels along the [100] direction, and their loss gives rise to a dynamical and reversible structural contraction. Moreover, after the removal of the crystallization water molecules, the compound exhibits a negative thermal behavior in the 85-155 °C temperature range, and irreversible structural transformation due to the loss of coordinated water molecules up to 200 °C. The IR and UV-vis spectra were determined for the as-synthesized sample, after the removal of crystallization water molecules and after the irreversible transformation due to the loss of coordinated water molecules. The thermal evolution of χ(m) was adjusted to a magnetic model considering an isotropic dimer plus two Ni(II) d(8) isolated octahedra. 相似文献
1000.
Palacios MA Mota AJ Ruiz J Hänninen MM Sillanpää R Colacio E 《Inorganic chemistry》2012,51(13):7010-7012
The first examples of pentanuclear heterotrimetallic [(LnNi)(2)Ru] [Ln(3+) = Gd (1) and Dy (2)] complexes were prepared and magnetostructurally characterized. They exhibit ferromagnetic interactions, leading to a high-magnetic-moment ground state. 相似文献