On components of the Auslander-Reiten quiver of trivial extensions of 2-fundamental algebras which contain projective modules

Trivial extensions of a certain subclass of minimal 2-fundamental algebras are examined. For such algebras the characterization of components of the Auslander-Reiten quiver which contain indecomposable projective modules is given.      

Synthesis and structural investigation of the cyclochiral boron resorcinarenes obtained from l-amino acids and phenylboronic acid

A diastereoselective synthesis and structural investigation of novel boron derivatives of resorcinarenes from l-amino acids and phenylboronic acid is described.     

Zinc-mediated allylation of aldoxime esters

A facile zinc-mediated Barbier-type allylation of aromatic aldoxime esters, producing the corresponding protected homoallylic hydroxylamines, which are readily converted into homoallylic hydroxamic acids, is described.     

Tricarbonyl rhenium complexes of bis(pyrazol-1-yl)methane and bis(3,5-dimethylpyrazol-1-yl)methane – Synthesis,spectroscopic characterization,X-ray structure and DFT calculations

Two novel tricarbonyl rhenium complexes based on the bidentate heterocyclic N–N ligands [bis(pyrazol-1-yl)methane(bpzm) and bis(3,5-dimethylpyrazol-1-yl)methane(bdmpzm)] have been synthesized by heating at reflux [Re(CO)₅Cl] with the appropriate N–N ligand in toluene. The compounds have been characterized by IR and UV–Vis spectroscopy and X-ray analysis. Density functional theory (DFT) and time-dependent (TD) DFT calculations have been carried out for the [Re(CO)₃(bdmpzm)Cl] complex.     

Copolymerization of ethylene with 1‐hexene over metallocene catalyst supported on complex of magnesium chloride with tetrahydrofuran

The study of ethylene/1‐hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂)/methylaluminoxane (MAO), anchored on a MgCl₂(THF)₂ support was carried out. The influence of 1‐hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethlaluminum (AlMe₃), or diethylaluminum chloride (Et₂AlCl)] on the behavior of the MgCl₂(THF)₂/Cp₂ZrCl₂/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp₂ZrCl₂ compound on the complex magnesium support MgCl₂(THF)₂ resulted in an effective system for the copolymerization of ethylene with 1‐hexene. The modification of the support as well as the kind of organoaluminum compound used as a modifier influenced the activity of the examined catalyst system. Additionally, the profitable influence of immobilization of the homogeneous catalyst as well as modification of the support applied on the molecular weight and molecular weight distribution of the copolymers was established. Finally, with the successive self‐nucleation/annealing procedure, the copolymers obtained over both homogeneous and heterogeneous metallocene catalysts were heterogeneous with respect to their chemical composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2512–2519, 2004     

New tetraaza[14]annulene receptors derived from 2,3-diaminonaphthalene: synthesis and crystal structures

The first synthesis of the bis(2-hydroxybenzoyl)dinaphthotetraaza[14]annulene ligand and its O,O-bis-alkylated derivatives containing a decanedioxy bridging moiety, pendant bis-alkoxy groups as well as dicationic butoxypyridinium substituents is reported. The synthetic procedures, full analytical and spectroscopic characterisation (NMR, MS and IR) and crystal structures of the new products are described. The crystal structures show that naphthylene moieties incorporated into the investigated derivatives provide additional opportunities for non-covalent interactions between the molecules.     

Comparative Structural and Electrical Studies of V2O3 and V2—xNixO3 (0 < x < 0.75) Solid Solution

V₂O₃ room and low temperature structures have been refined using PXRD and Rietveld procedures. At 15 K, in addition to the umbrella like opening of V—O bonds associated to the typical large V—V distance through the face shared octahedra (V—V_fsh) we have observed three different V—V distances through the edge shared octahedra (V—V_edsh) : 2.985Å, 2.908Å, and 2.847Å. This splitting is a consequence of the rotation of V—V pairs in a plane itself rotated out of the ( ac ) one which appears to be the origin for the well‐known rhombohedral to monoclinic distortion. Ni for V substitutions drive to a V_2—xNi_xO₃ solid solution with a wide homogeneity range (0 < x < 0.75). Structure refinements on selected compositions show that at both room and 15 K temperatures the typical V₂O₃ corundum type is kept. At 300 K, the main Ni effect is a drastic decrease of the c parameter associated to a flattening of the octahedra but also to an increase of the M—M_fsh distance without rotation of the M—M pairs. This explains the absence of the monoclinic transition in the whole homogeneity and temperature ranges and shows clearly that a large M—M_fsh distance is not necessarily associated with the monoclinic form. Despite this large distance observed in the whole temperature range, the electric behavior exhibits a conductor to insulator transition. It is explained in terms of semi conduction via an electron hopping process between V³⁺ and V⁴⁺ cations which depends on Ni amounts. This last result implies also that a large M—M_fsh distance is not associated with an insulating behavior.     

Effect of rehydration conditions on the catalytic activity of hydrotalcite-derived Mg-Al oxides in aldolization of acetone

Summary Mg-Al hydrotalcite-derived oxides with a varying Mg/Al molar ratio, ranging from 2.6 to 3.2, were rehydrated in the vapor phase at different temperatures (20-90°C). The catalytic performance of the materials obtained was studied in the aldol condensation of acetone. The initial activity of the rehydrated catalysts depended strongly on the Mg/Al molar ratio and the activation temperature. It was found that the re-arrangement of active sites, leading to the reconstruction of hydrotalcite-like phase, occurred during the catalytic test.     

Separation of synthetic food colourants in the mixed micellar system. Application to pharmaceutical analysis

The paper presents a rapid method for the determination of commonly used synthetic food dyes by micellar electrokinetic capillary chromatography. Detection and separation conditions allowing complete resolution of 15 synthetic food colourants were investigated. The effect of different surfactants on the analytes mobility in relation to their structure was tested. After optimization procedure a dual micellar system was selected. All food dyes were separated in less then 20 min using a fused silica capillary in the borate/dodecylsulfate/deoxycholate buffer containing acetonitrile as organic modifier. The detection wavelength was set at 210nm. The method was successfully validated by determination of linearity ranges, detection limits, precision and repeatability for all colourants tested. In order to apply the method for pharmaceutical analysis a sample pretreatment procedures were found. Liquid pharmaceuticals were used as it or just after dilution with water. From tablets or capsules the colourants were isolated by adsorption on acidic aluminium oxide. The method was used for identification and if possible for quantification the synthetic food dyes in pharmaceuticals. The analytes are detectable at a concentration level 0.3-0.8 microg ml(-1).