Search results for "Single crystal"

Above-bandgap ordinary optical properties of GaSe single crystal

2009

We report above-bandgap ordinary optical properties of ε-phase GaSe single crystal. Reference-quality pseudodielectric function 〈ε(E)〉 = 〈ε1(E)〉+i〈ε2(E)〉 and pseudorefractive index 〈N(E)〉 = 〈n(E)〉+i〈k(E)〉 spectra were measured by spectroscopic ellipsometry from 0.73 to 6.45 eV at room temperature for the light polarization perpendicular to the optic axis (math⊥math). The 〈ε〉 spectrum exhibited several interband-transition critical-point structures. Analysis of second-energy derivatives calculated numerically from the measured data yielded the critical-point energy values. Carmen.Martinez-Tomas@uv.es

High-pressure structural and elastic properties of Tl2O3

2014

The structural properties of Thallium (III) oxide (Tl2O3) have been studied both experimentally and theoretically under compression at room temperature. X-ray powder diffraction measurements up to 37.7 GPa have been complemented with ab initio total-energy calculations. The equation of state of Tl2O3 has been determined and compared to related compounds. It has been found experimentally that Tl2O3 remains in its initial cubic bixbyite-type structure up to 22.0 GPa. At this pressure, the onset of amorphization is observed, being the sample fully amorphous at 25.2 GPa. The sample retains the amorphous state after pressure release. To understand the pressure-induced amorphization process, we h…

Constrained formation of 2-(1-(arylimino)ethyl)-7-arylimino-6,6-dimethylcyclopentapyridines and their cobalt(ii) chloride complexes: synthesis, chara…

2015

A series of 2-(1-(arylimino)ethyl)-7-arylimino-6,6-dimethylcyclopentapyridine derivatives (L1-L5) was synthesized, and individually reacted with cobalt(II) chloride to form the corresponding cobalt chloride complexes (C1-C4). These compounds were characterized, and the single crystal X-ray diffraction for two representative cobalt complexes was carried out. The molecular structures indicate that 2,7-bis(arylimino)cyclopentapyridines act as tridentate ligands; however, one of the Co-N coordinative bonds is weak due to the spatial separation of nitrogen atoms. Upon activation with either MAO or MMAO, all cobalt complexes exhibit catalytic activities toward ethylene. Polymerization takes place…

Synthesis, structural analysis, and magnetic properties of ethylmalonate-manganese(II) complexes

2011

12 páginas, 10 figuras, 6 tablas.-- et al.

2-(N,N-Diethylaminomethyl)-6,7-trihydroquinolinyl-8-ylideneamine-Ni(ii) chlorides: application in ethylene dimerization and trimerization

2020

A series of Ni(II) complexes with the general formula [2-((NEt2)Me)-8-{N(Ar)}C9H8N]NiCl2, where Ar = 2,6-Me2C6H3 in Ni1, 2,6-Et2C6H3 in Ni2, 2,6-i-Pr2C6H3 in Ni3, 2,4,6-Me3C6H2 in Ni4, 2,6-Et2-4-MeC6H2 in Ni5, and 2,4,6-t-Bu3C6H2 in Ni6, has been prepared using a one-pot reaction of 2-(N,N-diethylaminomethyl)-6,7-dihydroquinolin-8(5H)-one with the corresponding aniline and nickel dichloride hexahydrate. The resultant complexes were characterized using elemental analysis and FT-IR spectroscopy, while the mononuclear Ni1 and Ni3 were also the subject of single-crystal X-ray diffraction study. On activation with MMAO, the complexes Ni1–Ni6 displayed good activity in ethylene oligomerization, f…

High pressure EXAFS on GaTe single crystal including polarization

1999

Selective derivatisation of resorcarenes: Part 7. The reason for the diastereoselectivity of Mannich reactions with chiral amines

2001

The formation of tetrakis(benzo-3,4-dihydro-1,3-oxazines) 2 by condensation of resorcarenes 1 with various primary amines and an excess of formaldehyde is not only regioselective but, in the case of (R)- or (S)-1-phenylethylamine and their para-substituted (Br, Me) derivatives, also completely diastereoselective. The reaction with the structurally similar (R)-1-aminoindane and (S)-1-(1-naphthyl)ethylamine, on the other hand, produced only a slight excess of one of the two possible epimers 2 and with (R)-1-cyclohexylethylamine no diastereoselectivity was found at all. The presence and the ratio of both diastereomeric structures can be clearly determined by NMR spectroscopy. Inspection of par…

Synthesis, characterization and thermal properties of new aromatic quaternary ammonium bromides

2004

Series of new aromatic R 2R′ 2N +Br - (R=benzyl, 4-methylbenzyl, 2-phenylethyl, 3-phenylpropyl; R′=ethyl, methyl, isopropyl) or RR′ 2NH +Br --type (R=benzyl, R′=isopropyl) quaternary ammonium bromides were prepared by using novel synthetic route in which a formamide (N,N-diethylformamide, N,N-dimethylformamide, N,N-diisopropylformamide) is treated with aralkyl halide in presence of a weak base. The compounds were characterized by 1H-NMR and 13C-NMR spectroscopy and mass spectrometry. Structures of the crystalline compounds were determined by X-ray single crystal diffraction, and in addition the powder diffraction method was used to study the structural similarities between the single crysta…

Halogen and Hydrogen Bonded Complexes of 5-Iodouracil

2013

Three derivatives of 5-iodouracil were prepared, and their complexation properties, supplemented by 5-iodouracil under the same conditions, were studied with and without halogen bond acceptors in N,N-dimethylformamide, N,N-diethylformamide, N-methylformamide, formamide, dimethylsulfoxide, and water. The intermolecular halogen and hydrogen bonding interactions observed in the solid state were investigated using single crystal X-ray diffraction and quantum chemical calculations, and the acquired data were contrasted with bonding interactions previously reported for 5-iodouracil in the Cambridge Structural Database. It was found that the polarized iodine atom and the amidic NH functionality ac…

DC electrical resistivity of Nb-Doped BaTiO3 and EPR measurements

1992

DC electrical resistivity measurements along the c-axis of Nb-doped BaTiO3 single crystals are presented in a wide range of temperature, covering the four phases, with special attention to the rhomboedral one. The temperature dependence of the conductivity leads to convincing arguments in favour of a polaronic mechanism. Below the orthorhombic-rhomboedral transition point, a strong increase of the resistivity is observed. The correlation of this behavior with EPR analysis in the same temperature range, is consistent with a sharp trapping of the ''free'' electrons, when the temperature decreases.