The relationship between the structures of Cu(ii) coordination compounds and their thermal decomposition

A study was made of the influence of the composition of the Cu(II) coordination sphere on the course of the thermal decomposition of the complexes Cu₄O(X+Y)₆L₄, whereX andY were Cl and Br, andL was piperidine or morpholine. The tetrahedral unit Cu₄O with the oxygen atom in its centre was found to be the thermally weakest part of the complex. The decomposition temperatures of the complexes were strongly influenced by the anionsX andY and by the ligandL. The temperature at which decomposition started was found to be the lower, the more chloride anions were substituted by bromide anions. The complexes containing piperidine as ligandL exhibited higher decomposition temperatures than those with morpholine as ligand. The decompositions of all the studied complexes were accompanied by redox reactions. The only compounds identified among the decomposition intermediates by X-ray diffraction were copper(I) halides. Copper(I) bromide underwent oxidation on further heating and a mixture of CuO and CuBr was obtained as the final decomposition product.

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Zusammenfassung Bei der thermischen Zersetzung von Komplexen der Formel Cu₄O(X+Y)₆L₄ mitX,Y=Cl bzw. Br undL= Piperidin oder Morpholin wurde der Einfluß der Zusammensetzung der Cu(II)-Koordinationssphäre auf den Verlauf der thermischen Zersetzung untersucht. Als thermisch schwächstes Glied des Komplexes wurde die tetraedrische Einheit Cu₄O mit dem Sauerstoffatom im Zentrum befunden. Die Zersetzungstemperaturen der Komplexe werden durch die AnionenX undY sowie durch die LigandenL wesentlich beeinflußt. Die Temperatur, bei der die Zersetzung einsetzt liegt um so niedriger, je mehr Chloridanionen durch Bromidanionen ersetzt werden. Komplexe mit Piperidin als Ligand zeigen höhere Zersetzungstemperaturen als mit dem Ligand Morpholin. Die Zersetzung aller Komplexe ist von Redoxreaktionen begleitet. Die einzigen Verbindungen, die unter den Zersetzungsprodukten mittels Röntgendiffraktion identifiziert wurden, waren Kupfer(I)-halogenide. Kupfer(I)-bromid unterliegt bei weiterem Erhitzen einer Oxidation und man erhält letztendlich ein Gemisch aus CuO und CuBr als Zersetzungsprodukt.

     

Binary superlattices of PbSe and CdSe nanocrystals

In this paper we show that self-organization of colloidal PbSe and CdSe semiconductor nanocrystals with a size ratio of 0.57 leads to binary structures with a AB2 or a cuboctahedral AB13 lattice. The type of superlattice formed can be regulated by the relative concentration of both nanocrystals in the suspension.     

Cost-effective sulphur emission reduction under uncertainty

The problem of reducing SO₂ emissions in Europe is considered. The costs of reduction are assumed to be uncertain and are modeled by a set of possible scenarios. A mean-variance model of the problem is formulated and a specialized computational procedure is developed. The approach is applied to the trans-boundary air pollution model with real-world data.     

Equivalence of structure constants in non-Kolmogorov and Kolmogorov spectra

We find the equivalence of the structure constants in non-Kolmogorov and Kolmogorov spectra in a turbulent atmosphere. As the reference point, the spherical wave scintillation index in a non-Kolmogorov medium is used. Relations of the structure constants are found to be functions of the power law of the turbulence spectrum and the Fresnel zone. It will be useful to employ the equivalence of the structure constants in making performance comparisons found with non-Kolmogorov and Kolmogorov spectra.     

Chromatographic Determination of Total Cholesterol in Human Lung Healthy and Cancer Tissues of the Same Patient

JPC – Journal of Planar Chromatography – Modern TLC - Cholesterol is an essential component of mammalian cells, but its role in cancer is unclear. We have determined the total...     

Synthesis of magnetic noble metal (nano)particles

Noble metal particles can be made strongly ferromagnetic or diamagnetic provided that they are synthesized in a sufficiently strong magnetic field. Here we outline two synthesis methods that are fast, reproducible, and allow broad control over particle sizes ranging from nanometers to millimeters. From magnetometry and light spectroscopy, it appears that the cause of this anomalous magnetism is the surface anisotropy in the noble metal particles induced by the applied magnetic field. This work offers an elegant alternative to composite materials of noble metals and magnetic impurities.     

Conformational Transmission in 5′-PV and 5′-PV TBP Phosphorylated Nucleosides. Implications For DNA Structure and Dynamics

Abstract

Specific conformational changes in DNA and RNA can be induced via a transient pentacoordination of the phosphorus atoms in the helix backbone. The details of this conformational transmission mechanism are discussed briefly, using experimental data that were obtained with a set of 5′-pIV and 5′-pV phosphorylated tetrahydrofurfuryl systems. A conformational study on the more realistic model system, the dinucleotide 2 in which a stabilized pentacoordinated phosphorus forms the internucleoside linkage, is presented. Furthermore, it has been found that methylation of the phosphate groups in d(T_pT_pT_pT_pT_pT) results in the formation of a non-Watson & Crick type parallel duplex DNA structure, in which the two strands are joined via hydrogen bonding between the thymidine bases. Various physico-chemical techniques (e.g. NMR methods and UV hyperchromicity) were used to elucidate the structural details of the parallel duplex. Characteristic properties (parallellity, slimness, symmetry) are presented.