Functional Carbazole Liquid‐Crystal Block Codendrimers with Optical and Electronic Properties

The synthesis and characterisation of a family of block codendrimers consisting of highly versatile mesogenic and carbazole‐containing 2,2‐bis(hydroxymethyl)propionic acid (bis‐MPA) dendrons are reported. The liquid‐crystal behaviour was investigated by means of differential scanning calorimetry, polarised‐light optical microscopy and X‐ray diffraction. Depending on the chemical structure of the constituent dendrons, the codendrimers show lamellar or columnar mesophases. On the basis of the experimental results, models both at the molecular level and in the mesophase are proposed. The physical properties of the block codendrimers derived from the presence of the carbazole moiety in their structure were investigated: photoluminescence in solution and in the mesophase, electrochemical behaviour and hole transport. Electrodeposition of carbazole dendrons afforded a globular supramolecular conformation in which the mesogenic molecular side plays a key role.     

Residual currents and corridor of flow in the Rio de la Plata

The Rio de la Plata is a large and shallow water body that discharges onto the Atlantic Ocean. The main driving forces for the river flow are the bathymetry, tides, the outflow from the Paraná and Uruguay rivers and the winds. A numerical model covering the entire river was set up with the objective of increasing our understanding of the hydrographical features and morphological dynamics in the Estuary. The simulations revealed a counter-clockwise residual circulation in the Samborombón Bay and an eastward net flow near the Uruguayan coast. The residual flow is forced by both the tides and the bathymetry. The residence time for the entire river ranges from 40 to 80 days. However, residence times above 120 days was found in the Samborombón Bay. Three corridors of flow have been identified.     

Application of micellar electrokinetic chromatography to the quality control of a pharmaceutical preparation containing three bronchodilators

Theophylline(1,3-dimethylxanthine), dyphylline [7-(2,3-dihydroxypropyl)theophylline] and proxyphylline [7-(beta-hydroxypropyl)theophylline] are three bronchodilators administered jointly in a single pharmaceutical preparation used against asthma. A micellar electrokinetic chromatography (MEKC) method for their resolution using a background electrolyte consisting of 20 mM tetraborate at pH 8.5 and 100 mM sodium dodecyl sulfate is proposed. The method was used to determine the three active principles in a pharmaceutical preparation. The small amount of sample required and the expeditiousness of the procedure allow content uniformity to be determined in individual tablets. The values of the validation parameters for the method (viz. selectivity, linearity, accuracy, precision, limit of detection, limit of quantitation and robustness) are reported. A complete factor design (2(3)x2) including pH, the surfactant concentration and the ionic strength of the background electrolyte as factors was used to estimate robustness. Based on the results, the method is robust enough for quantitation purposes.     

A new synthetic route to bulky "second generation" tris(imidazol-2-ylidene)borate ligands: synthesis of a four coordinate iron(II) complex

A bulky tripodal tris(carbene)borate ligand, prepared from 1-tert-butylimidazole, is cleanly transferred to iron(II) by a magnesium reagent.     

Synthesis of new isoxazoles derivatives attached to sugar moieties

This work reports the synthesis of isoxazoles linked to sugar derivatives in different positions of furanosidic rings, by intramolecular oxidative cyclization of α,β‐unsaturated oximes with iodine, potassium iodide and sodium hydrogen carbonate. These oximes were obtained from aldehyde‐sugar derivatives.     

Indirect bromometric microdetermination of nitrate and perchlorate,using nitron as reagent

Summary An indirect bromometric method for the determination of nitrate or perchlorate is described. A known excess of standard nitron acetate solution is added to the sample solution to precipitate the anion to be determined; the excess of reagent is then determined in the supernatant liquid by bromatometric titration. The relative standard deviation of the method is 0.7% for nitrate and 0.5% for perchlorate. Sulphate, phosphate and fluoride do not interfere and chloride does not interfere up to a concentration of 0.1 M. Bromide, iodide, chromate, nitrite and chlorate interfere but can be eliminated.

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Zusammenfassung Ein indirektes bromatometrisches Verfahren zur Bestimmung von Nitrat oder Perchlorat wurde beschrieben. Ein gemessener Überschuß einer Nitronacetatlösung bekannter Konzentration wird zur Fällung des Anions der Probe zugesetzt und im Überstand bromatometrisch zurücktitriert. Die rel. Standardabweichung beträgt 0,7% für Nitrat und 0,5% für Perchlorat. Sulfat, Phosphat und Fluorid stören nicht; Chlorid stört nicht bis zu 0,1-m Konzentration. Bromid, Jodid, Chromat, Nitrit und Chlorat stören zwar, können aber eliminiert werden.

     

HETEROCYCLIZATION OF AMINOTHIAZOLES

Several new 2-arylidinoamino-4-(3-coumaryl)thiazole derivatives were synthesized via the reaction of 2-amino-4-(coumaryl)thiazole with aromatic aldehydes and other reagents. Structural elucidations were based on elementary analysis and spectral data studies.