New Building Blocks for the Design of Oligonuclear Copper Complexes Based on Amino Carbohydrates

Remarkably high magnetic coupling and O(2)-activation ability analogous to that of catechol oxidase are characteristics of the first structurally defined, low-symmetry oligonuclear copper complexes of tridentate beta-oxoenamine ligands based on amino carbohydrates (the structure of a bis(acetylbutenonylaminoglucosidato)bis(μ-acetato)tricopper(II) complex is shown).     

Notiz über den Chloraufschluß niobhaltiger Substanzen

In an investigation on the decomposition of oxide minerals containing Ti, Nb, Fe, U and Y mixtures of TiO₂, Nb₂O₅, Fe₂O₃, U₃O₈ and Y₂O₃ have been heated in streaming Cl₂ containing SOCl₂. In order to avoid the formation of NbOCl₃, which is highly disturbing the distribution pattern of the chlorides, the reaction boat was covered with carbon powder. TiCl₄ was absorbed in sulphuric acid; NbCl₅, FeCl₃ and UCl₄ were condensed in the reaction tube and were separated by usual methods; YCl₃ remained in the reaction boat.     

Bücherbesprechungen

Ohne Zusammenfassung     

Chemistry of thienopyridines. XXXII. Direct introduction of C-substituents gamma to the heteronitrogen atom in the thieno[2,3-b]pyridine system

Treatment of the N-oxide 1a of thieno[2,3-b]pyridine ( 1 ) with either (a) acetic anhydride and ethyl cyanoacetate or (b) benzoyl chloride and an enamine of cyclohexanone (Hamana reactions) serves to introduce a C-substituent at the 4-position of 1 . In case (a) one obtains a yellow, isolable vinylogous N-ylide 5 (23% yield), which undergoes facile transformation into ethyl 2-(4-thieno[2,3-b]pyridyl)cyanoacetate ( 1e ) (88–93 %). Acetic anhydride reconverts 1e to 5 (95%). Case (b) produces 2-(4-thieno[2,3-b]pyridyl)cyclohexanone (39%), hydrolyzable to 6-(4-thieno[2,3-b]pyridyl)hexanoic acid (45%). The hydrochloride of 1a is also reported. Structural formulations are based on spectral studies (including ¹³C nmr data for 1 and 1e ) and chemical transformations. Major contrasts (plus some similarities) between the systems 1 and quinoline in the Hamana reactions are discussed.     

The neutralinos of theSU(N,1) minimal supergravity model and standard cosmology

We discuss the effect of the lightest supersymmetric particle (LSP), a Higgsino, and of the gravitino of theSU(N,1) minimal SUGRA model in the standard big bang theory. The freeze out of the LSP depends on the gravitino mass and on the top mass and leads to restrictive lower bounds for these parameters in the model. The decay of a gravitino with mass in the few TeV range leads to a delay in the cooling of the universe before nucleosynthesis. This constitutes the main bound on the gravitino mass of the model. The results are compared with the more standard “simultaneous decay approximation”.     

Electromagnetic response of unconventional superconductors

The magnetic field penetration depth, surface resistance and far infrared reflectivity are calculated for two anisotropic order parameters having either points or lines of nodes in the energy gap. Resonant impurity scattering is taken into account for a wide range of scattering rates. Comparison with experimental results on heavy Fermion superconductors shows that the order parameter cannot be deduced unambiguously from the temperature dependence of the penetration depth. Fits to surface resistance measurements on UBe₁₃ are best in the Born approximation, rather than the unitarity limit. Experiments on high-T _c materials are largely inconclusive, offering little support for the applicability of BCS theory and providing no evidence against novel pairing interactions leading to unusual order parameters.     

The insertion and extrusion of heterosulfur bridges. VIII. Dibenzothiophene from biphenyl and derivatives

Sulfur bridging of biphenyl ( 4 ), 4-methylbiphenyl, and the biphenylthiol isomers ( 7 ) to yield dibenzothiophene ( 3 ) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide-molybdic oxide-alumina (CMA-1) catalyst at 450° in a flow system. Alumina also catalyzes a number of these transformations. The possibility that compounds 7 (especially the 2-isomer) are intermediates in the conversion 4 → 3 is noted.     

New approach to unravel the structure–property relationship of methylcellulose

In the present paper we suggest a new concept to overcome some of the so far unsolved problems of the structure–property relationship of methylcellulose, the most important nonionic cellulose ether industrially produced in large scale. Not only from the viewpoint of scientific understanding, but also from that of the peculiar and application-determining behavior, the aggregation in aqueous solution and phase separation on heating are the most important questions. As a part of the concept, we had prepared amphiphilic block co-oligomers of tri-O-methylated and unmodified cello-oligosaccharides as structural models of typical sequences in methylcellulose chains. Now static and dynamic light scattering measurements and transmission electron microscopy (TEM) were carried out using solutions of the oligomers in water. Ellipsoidal particles with dimensions of about 50 nm for the semi-major axis and of circa 25 nm for the semi-minor one could be detected. These findings agree with the radii of gyration and the hydrodynamic radii, determined by static and dynamic light scattering. The data preliminary obtained demonstrate the strong aggregation tendency of block-like methylated cello-oligosaccharides.