Neue methoden zur herstellung von trialkylphosphan-alkadien-eisen(0)-komplexen

Mono(1,3-diene)tris(PR₃)iron(0) complexes and bis(1,3-diene)mono(PR₃)iron(0) complexes can be synthesized by reduction of FeCl₂ with magnesacyclopent-3-ene or activated Mg in the presence of 1,3-dienes and the appropriate PR₃ (R = Me, Et, Prⁿ, Cy) ligand. How the various substituted bis(1,3-diene)PR₃Fe⁰ complexes can be obtained from the thermally unstable 1,3-butadiene-tris(PR₃)Fe⁰ complexes by addition of 1,3- or 1,5-dienes is shown. The NMR spectra of these complexes indicate that they are square-pyramidal. This geometry was confirmed by a crystal structure analysis of 1,5-COD-1,3-butadiene-iron(0)-PEt₃. The probable mechanism of formation of these novel iron(0) complexes is discussed and their characteristic properties are described.     

Striking presence of Egyptian blue identified in a painting by Giovanni Battista Benvenuto from 1524

Egyptian blue has been identified in a painting from 1524 by the Italian artist Ortolano Ferrarese (Giovanni Battista Benvenuto). Egyptian blue is the oldest known synthetic pigment, invented by the Egyptians in the fourth dynasty (2613–2494 bc) of the Old Kingdom and extensively used throughout Antiquity. From about 1000 a.d., it disappeared from the historical record and was only reinvented in the late nineteenth and early twentieth century. The discovery of Egyptian blue in Ortolano Ferrarese’s painting from 1524 shows that Egyptian blue was in fact available in the period from which it is normally considered not to exist. The identification of Egyptian blue is based on optical microscopy supported by energy-dispersive spectroscopy and visual light photon-induced spectroscopy, and finally confirmed by Raman microspectroscopy.     

Bis(tetraphenylcyclobutadien)palladium(0)

Tetraphenylcyclobutadienepalladium dichloride reacts with 1,2,3,4-tetraphenyl-1,4-dilithiumbutadiene or with sodium with abstraction of halide to give the sandwich compound bis(tetraphenylcyclobutadiene)palladium(0). The structure of the latter is elucidated by spectroscopic methods and its reactions with Br₂, H₂, K and HNO₃ are described.     

Ein zweikerniger tetraphenylcyclobutadien-nickel(0)-komplex mit cyclooctatetraen als brückenligand

Tetraphenylcyclobutadiene(η⁴-cyclooctatetraene)nickel(0) reacts with a variety of reagents, e.g. lithium, CpCo(C₂H₄)₂ or benzonitrile, to give the binuclear complex bis(tetraphenylcyclobutadiene-nickel(0))-μ₂-η⁴-cyclooctatetraene, which structure has been assigned using IR, UV, ¹H NMR and mass spectral methods, also the properties and reactions have been investigated.     

Eine einfache methode zur herstellung von bis(tetraphenylcyclobutadien)nickel

Bis(tetraphenylcyclobutadien)nickel (III). Eine Suspension aus 4.3 g (7.5 mmol) Tetraphenylcyclobutadien-nickeldibromid (I) und 2.8 g (7.5 mmol) 1,2,3,4-Tetraphenyl-1,4-dilithiumbutadien (II) in 250 ml Toluol wurde bei 20°C 4 Tage kräftig gerührt, wobei allmählich eine Verfärbung nach braun-violett eintrat. Nach Abziehen des Lösungsmittels wurde der Rückstand in einem Soxhlet-Extraktor 3 Tage mit 250 ml Benzol extrahiert; die Extraktionslösung wurde bis zur Trockne eingedampft, der Rückstand (3.5 g) in 500 ml Toluol gelöst und bei -20°C umkristallisiert. Erhalten: 2.7 g (47.0%) III. Das Produkt ist laut Elementaranalyse und NMR-Spektrum mit dem bereits beschriebenen [3] identisch.     

Modelling the metabolic action of human and rat CYP1A2 and its relationship with the carcinogenicity of heterocyclic amines

Cytochrome P450 (CYP) is a family of enzymes responsible for organism detoxification. However, some of the members of the CYP1A subfamily also catalyse the activation of heterocyclic amines (HAs), present in cooked meat, to carcinogenic compounds which have been shown to increase the risk of breast, colorectal and lung cancer. In humans, CYP1A2 is the enzyme with the most significant action in HA metabolism but in rodents CYP1A1 is also important in this biotransformation. Understanding the metabolic action of these enzymes is essential to predict the factors that enable the formation of the carcinogenic products. We have built two models of CYP1A2, one for the human enzyme and one for the rat homologue. The templates chosen include the only X-ray structure published to date for a mammal CYP, a quimeric C2A5 from rabbit, as well as CYPs belonging to Bacillus megaterium (CYPBm-3), Pseudomonas putida (CYPcam), Pseudomonas sp. (CYPterp), and Saccharopolyspora erythraea (CYPeryf). Two HAs, MeIQ (2-amino-3,4-dimethylimidazo[4,5-?]quinoline) and MeIQx (2-amino-3,8-dimethylimidazo[4,5-?]quinoxaline), known substrates of human and rat CYPIA2, were docked in the active site of the models, providing information regarding the different catalytic rates associated with the metabolisms in both enzymes. This is important for analysing the behaviour of animal models concerning the testing of anticancer drugs.     

Optical Fiber Sensor Technology in Portugal

Abstract

A general overview of the R&D activity in fiber optic sensing developed over the last fifteen years in Portugal is given. Different topics are addressed, including interferometric, intensity and Bragg grating based fiber optic sensors, signal processing and multiplexing techniques, optical current sensors, together with some references to field trials and applications. Possible guidelines for present and future national R&D activity on this subject are outlined.