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71.
Basurto S García S Neo AG Torroba T Marcos CF Miguel D Barberá J Ros MB de la Fuente MR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(18):5362-5376
Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic structure. Although the molecules have rigid aromatic cores, they lack terminal tails and instead the polarizable atoms (S, halogens) or polar groups (CN, CO) act as unusual soft parts. On the basis of many structurally related materials, we conclude that for this type of compound molecular stacking in the solid state is a prerequisite for the appearance of a columnar mesophase, although other intermolecular interactions within the layers are also important in establishing liquid-crystalline order. The behavior reported for these mesomorphic molecules opens up new possibilities in the search for related molecular interactions that might be useful for the construction of supramolecular architectures with particular properties. 相似文献
72.
[reaction: see text] A simple and efficient stereoselective synthesis of aziridine-2-phosphonate 3, and -phosphine oxide 5 by diastereoselective addition of Grignard reagents to 2H-azirine phosphonate 1 and -phosphine oxide 4 is reported. Similarly, the addition of heterocyclic amines and benzenethiol to aziridines 1 and 4 yielded functionalized aziridines 10, 11, and 18. These aziridines are used as intermediates for the regioselective synthesis of beta-aminophosphine oxides 6 and beta-aminophosphonates 7, as well as alpha- aminophosphonates 8. Phenylsulfenyl-substituted alpha-aminophosphorus derivatives 15 and 19 are obtained directly from benzenethiol and 2H-azirine phosphonates 1 and -phosphine oxides 4. 相似文献
73.
M. Jesús Rodríguez M. Isabel Fernndez Ana M. Gonzlez‐Noya Marcelino Maneiro Rosa Pedrido Miguel Vzquez Bruno Donnadieu Manuel R. Bermejo 《无机化学与普通化学杂志》2005,631(11):2161-2166
M(HL)(H2O)n complexes have been obtained by the electrochemical reaction of Fe, Co, Ni, Cu, Zn and Cd anodes with the potentially pentadentate and trianionic asymmetrical Schiff base 3‐aza‐N‐{2‐[1‐aza‐2‐(5‐nitro‐2‐hydroxylphenyl)‐vinyl]phenyl}‐4‐(5‐nitro‐2‐hydroxyphenyl)but‐3‐enamide (H3L), containing a hard amido donor atom. The complexes have been characterized by elemental analysis, mass spectrometry, IR and 1H NMR spectroscopies, magnetic measurements and molar conductivities. Co(HL)(H2O) ( 2 ) has been found to rearrange in DMF solution into a crystallographically solved octahedral complex, CoL1(H2O)2 ( 7 ) [where H2L1 is the symmetrical Schiff base ligand N,N′‐(1,2‐phenylene)‐bis(5‐nitro‐3‐hydroxysalicylidenimine)]. A hydrolysis mechanism is discussed to explain this rearrangement. 相似文献
74.
A semi-continuous dilatometer for measuring excess volume is described. Excess volumes of p-xylene +n-hexane + n-octane, +n-decane, +n-dodecane, +n-tetradecane, and +n-hexadecane have been measured at 298.15 K as a function of composition. 相似文献
75.
Methodology based on the cloud-point phenomenon was applied to the comparative study of 3 different polyoxyethylene nonionic surfactants in order to extract and preconcentrate a group of phenolic derivatives in water samples; these phenolic compounds, which were determined by liquid chromatography with UV detection, included 11 pollutants given priority by the U.S. Environmental Protection Agency. The optimum conditions for the extraction and preconcentration of phenolic compounds were established for each surfactant. The surfactant that gave the best extraction and preconcentration of the analytes under study was polyoxyethylene 6 lauryl ether (C12E6) with detection limits of <3.5 microg/L for all the phenolic compounds tested. The method was applied to seawater and depurated wastewater samples. 相似文献
76.
Uranium(VI and IV) and thorium(IV) give cathodic indentations in supporting electrolytes prepared from 0.1M perchloric acid, 0.5 M ammonium thiocyanate and 5·10-3M cupferron (solution A) or from 0.1 M succinic-succinate buffer pH 4, 0.1 M sodium chloride, 10-3M cupferron and 0.05% gelatine (solution B). The uranium indentation on the dE/dt = f(E) curve (Q=0.75 and 0.73) permits its detection at the 3·10-7M level. The thorium indentation (Q=0.78) permits its detection at the 4·10-7M level in solution B. Methods for the elimination of interfering ions for the uranium determination are described. In the determination of thorium, Ga(III), Fe(III), Ti(IV) and U(VI) interfere. 相似文献
77.
Matilde Fondo Ana M. García Deibe Noelia Ocampo Manuel R. Bermejo Jesús Sanmartín 《无机化学与普通化学杂志》2005,631(11):2041-2045
The heptadentate Schiff base H3L reacts with cobalt(II) acetate in methanol to form the discrete dinuclear complex Co2L(OAc)2(OMe)(H2O)2 ( 1 ·2H2O). The reaction of 1 ·2H2O with NMe4OH·5H2O in methanol gives rise to displacement of the acetate by methanolate groups, yielding Co2L(OMe)3(H2O) ( 2 ·1H2O). Recrystallizations of the Schiff base, 1 ·2H2O and 2 ·H2O in different solvents, produce single crystals of H3L, 1 ·2.5H2O and 2 ·2MeOH, respectively. The crystal structures of 1 ·2.5H2O and 2 ·2MeOH show the cobalt atoms double bridged by and endogenous phenol oxygen atom and an exogenous methanolate oxygen donor, giving rise to Co2O2 cores with Co···Co distances of ca. 2.87 Å. 相似文献
78.
Ana M. Reverdito Liliana Orelli Mnica Dalmaso Isabel Perillo Beatriz M. Fernndez 《Journal of heterocyclic chemistry》1991,28(2):273-281
Reaction of 1,2-diaryl-3-methyl-1,4,5,6-tetrahydropyrimidinium iodides 1a-i with alkaline solutions afforded N-aroyl-N-aryl-N'-methyltrimethylenediamines 2a-i . Compounds 2 are stable under acid conditions but in neutral or alkaline media spontaneously rearrange giving N-aroyl-N'-aryl-N-methyltrimethylenediamines 3a-i . Treating compounds 3 with concentrated acids reverse reaction takes place. Kinetic studies were performed on this intramolecular N → N' aroyl transfer over the Ho-pH range -0.9 to 2.30. Compounds 3 undergo acyl transfer to give 2 by a mechanism which involves a change in the rate determining step from formation to acid-catalysed decomposition of a six-membered heterocyclic intermediate on going from Ho to pH values. The existence of maxima in the pH rate profile allow to determine apparent pKa values of the hexahydropyrimidine intermediates which gave good correlation with the Swain F substituent constants. Stability of these heterocycles was also predicted by determination of thermodinamic parameters. Comparisons are made with the behaviour of five-membered heterocyclic intermediates (imidazolidine derivatives) which were studied in an earlier paper. 相似文献
79.
Antonilêni F. D. Medeiros Ana Flávia O. Santos F. S. de Souza I. D. B. Júnior J. Valdilânio J. V. V. Procópio D. P. de Santana R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,89(3):775-781
Compatibility studies between active drugs and excipients are substantial in the pharmaceutical technology. The objective
of the present work was to develop pre-formulated mixtures of metronidazole (MT) obtained by spray drying (SPDR) and their
thermoanalytical characterization. Dynamic and isothermal TG, conventional DSC and DSC coupled to a photovisual system were
used. DSC experiments with both techniques confirmed the homogeneity of the conventional and pre-formulated mixtures. The
TG data made possible the comparison the thermal stability of the different mixtures. Similar thermal stabilities were found
of the conventional and pre-formulated mixtures, with slower particles sizes of MT. 相似文献
80.
Rauter AP Martins A Borges C Ferreira J Jorge J Bronze MR Coelho AV Choi YH Verpoorte R 《Journal of chromatography. A》2005,1089(1-2):59-64
The anti-hyperglycemic flavonoid extract obtained from Genista tenera was first studied by liquid chromatography (LC)-diode array detection (DAD) which showed the presence of two major compounds. One of them was identified as genistein-7-O-glucoside. Luteolin-7-O-glucoside was detected as a minor constituent, while luteolin-7,3'-di-O-glucoside and rutin were found in trace amounts. LC-DAD-ESI-MS and NMR were used to confirm the structure of these compounds and allowed the elucidation of the structure of the unknown major compound, which is the flavonoid 5,7,4'-trihydroxyisoflavone-8-C-glucoside. 相似文献