Zink-Koordinationsverbindungen mit Imidazolin- und Imidazol-Donorliganden

Zinc Coordination Compounds with Imidazoline and Imidazole Donor Ligands . By reaction of the two bidentate bisimidazoline ligands 1,2-bis(2-imidazoline-2-yl)ethan (BIE) and 1,2-bis(2-imidazoline-2-yl)benzene (BIB) with zinc bromide under various reaction conditions the complexes [ZnBr₂(BIE)] ( 1 ), [ZnBr₂(BIB)] ( 2 ), [Zn(BIE)₂]Br₂ ( 3 ) and [Zn(BIB)₂](BPh₄)₂ ( 4 ) were synthesized and characterized. In all compounds the zinc atom is tetrahedrally coordinated, either by a bidentate ligand and two bromine ligands, or by two of the chelate ligands. Zn? N? bond distances for 1 – 4 range from 1.966(2) to 2.013(3) Å, and the Zn? Br distances from 2.372(1) to 2.403(1) Å. [3-(imidazole-1-yl)-1-oxopropyl]benzene (IOB) was prepared as a novel imidazole ligand which carries a keto-O atom in 1,5-position to the pyridine-N atom. The zinc in [ZnCl₂(IOB)₂] ( 5 ) is coordinated by two ligands and two Cl atoms forming a distorted tetrahedral ZnN₂Cl₂ unit (Zn? N: 2.013(3) and 2.029(2) Å; Zn? Cl: 2.226(1) and 2.242(1) Å). The colourless compounds 1 – 5 were characterized by IR, ¹H-NMR, X-ray absorption spectra and single-crystal X-ray structure analysis. Space groups and structural data: 1 : P2₁/c, a = 7.717(2), b = 22.814(5), c = 8.026(2) Å, β = 117.58(2)° (140 K), R = 0.0283; 2 : Cc, a = 11.831(3), b = 11.677(1), c = 11.846(1) Å, β = 114.55(2)°, R = 0.0237; 3 : P4₂/n, a = 7.931(1), c = 16.945(1) Å, R = 0.0312; 4 : P2₁/c, a = 18.666(2), b = 16.615(2), c = 19.786(2) Å, β = 99.17(1)°, R = 0.0472; 5 : P2₁/c, a = 9.173(2), b = 9.230(1), c = 28.357(3) Å, β = 96.63(1)°, R = 0.0317.     

Untersuchungen an oxidischen Katalysatoren. XVII. Zum Zusammenhang zwischen elektrischen und katalytischen Eigenschaften dotierter Zinkoxidkatalysatoren

Studies on Oxide Catalysts. XVII. On the Relations between Electric and Catalytic Properties of Doped Zinc Oxide Catalysts The electric conductivity and thermo EMF of zinc oxide catalysts doped with Li₂O, Ga₂O₃ and Fe₂O₃, and, on the other hand, their activity of dehydrogenation in the catalytic decomposition of isopropanol have been studied. The electric measurements were carried out preferably in an atmosphere of isopropanol. In washed single-phase catalysts doped with Li₂O (n-type semiconductors) the relation between the catalytic activity of dehydrogenation and the FERMI level position postulated by VOL'KEN?TEJN was verified quantitatively. The absorption of the isopropanol is considered to be the rate-determining acceptor step. In unwashed zinc oxide catalysts doped with Li₂O, however, the inversion from n- to p-type (between 0.3 and 0.5 mole-% Li₂O) causes a change in the character of the rate-determining step from an acceptor to a donor step. For the two-phase and three-phase solid systems of ZnO? Ga₂O₃ and ZnO? Fe₂O₃, respectively, it was not possible to find quantitative relations according to the electron theory of catalysis.     

Adsorption to metal oxides of the Pseudomonas aeruginosa siderophore pyoverdine and implications for bacterial biofilm formation on metals

The initiation of biofilm formation is poorly understood, and in particular, the contribution of chemical bond formation between bacterial cells and metal surfaces has received little attention. We have previously used in situ infrared spectroscopy to show, during the initial stages of Pseudomonas aeruginosa biofilm formation, the formation of coordinate covalent bonds between titanium dioxide particle films and pyoverdine, a mixed catecholate and hydroxamate siderophore. Here we show using infrared spectroscopy that pyoverdine can also form covalent bonds with particle films of Fe2O3, CrOOH, and AlOOH. Adsorption to the metal oxides through the catechol-like 2,3-diamino-6,7-dihydroxyquinoline part of pyoverdine was most evident in the infrared spectrum of the adsorbed pyoverdine molecule. Weaker infrared absorption bands that are consistent with the hydroxamic acids of pyoverdine binding covalently to TiO2, Fe2O3, and AlOOH surfaces were also observed. The adsorption of pyoverdine to TiO2 and Fe2O3 surfaces showed a pH dependence that is indicative of the dominance of the catechol-like ligand of pyoverdine. Infrared absorption bands were also evident for pyoverdine associated with the cells of P. aeruginosa on TiO2 and Fe2O3 surfaces and were notably absent for genetically modified cells unable to synthesize or bind pyoverdine at the cell surface. These studies confirm the generality of pyoverdine-metal bond formation and suggest a wider involvement of siderophores in bacterial biofilm initiation on metals.     

A rapid surface plasmon resonance (SPR) biosensor immunoassay for screening of somatotropins in injection preparations

The use of growth hormones (recombinant somatotropins (rSTs)) is approved in several countries, e.g. the USA, Brazil and Australia to enhance growth or lactating performances of livestock. Their use in the EU is banned, however, due to the widespread application, the illegal use within the EU cannot be excluded. To screen for rSTs in injection preparations, a biosensor immunoassay (BIA) using surface plasmon resonance (SPR) technology was developed. Compared to existing analysis methods for rSTs, like radio immunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), this technique provides a rapid (7 min) alternative. A direct BIA was compared to an indirect (inhibition) BIA and the performances of several antibodies against (r)STs were compared in the indirect BIA. In the final inhibition assay, using rabbit anti-bovine rST, extracts from several injection preparations were shown to contain bovine rST (rbST). The limit of detection for rbST in the assay is 0.008 microg mL(-1) which is far below the expected concentrations in injection preparations. Although the cross-reactivities for STs of other species were low, screening of injection preparations for porcine, equine and human ST was feasible through the analysis of less diluted extracts. Tryptic digestion followed by nano-electrospray liquid chromatography-ion trap tandem mass spectrometry (nano-LC-MS/MS) was used to identify STs.     

Beeinflussung der katalytischen Eigenschaften von Al2O3?SiO2-Katalysatoren durch Alkalivergiftung

Effect of Alkali Contamination on the Catalytic Properties of Al₂O₃? Si₂ Catalytic properties of amorphous Al₂O₃? SiO₂ catalysts containing different amounts of Al₂O₃ in dehydration of isopropanol and cracking of cumene were examined after a defined contamination of the acid centers by sodium ethylate from alcoholic solution. In both reactions, the catalytic activity is decreased by treatment with sodium ethylate, the cracking of cumene being suppressed at a lower alkali concentration than the dehydration of isopropanol. In dehydration of isopropanol, the dependence of the catalytic activity on the alkali content is influenced strongly by the Al₂O₃ content of the catalysts. In the cracking of cumene, strongly acid Brönsted centers are active, whereas the dehydration of isopropanol proceeds by joint action of acid Lewis or Brönsted centers, respectively, with basic centers at the surface of the catalyst (hydroxide groups or oxygen anions).     

Decentralized Control of an Industrial Robot with Elastic Gears

Today's robots, especially for industrial applications, regularly appear on the market in new shapes, various sizes and challenging configurations. In a certain number of interesting cases, the need for a satisfying joint control will arise, even if the system dynamics is not completely known. Furthermore, despite the fact that most robots' dynamics may be modeled very precisely, the use of complex model based control methods is often not applicable because of considerably high time delays to the distributed drives. Consequently, this contribution describes an independent joint control approach based on the method of nonlinearity estimation and compensation. In contrary to centralized control structures, industrial servo drives, powering synchronous motors, control independently their elastic joints with high sampling frequencies. Focusing not only on simulations, but also on laboratory experiments, detailed results for an industrial robot with six degrees of freedom with elastic gears are presented. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)