Influence of initial oxygen coverage and magnetic moment on the NO decomposition on rhodium (111)

In this study, density functional theory calculations were performed to investigate the influence of oxygen preoccupation on the nitrogen oxide decomposition on rhodium. Besides gauging the coverage dependence of the adsorption energy of NO on the (111) rhodium facet, the influence of the initial oxygen coverage on the kinetics and thermodynamics of the nitrogen oxide decomposition reaction was also studied. The results are discussed with respect to a novel NOx decomposition catalyst. Furthermore, the influence of spin effects on the adsorption geometry as well as the adsorption energy is examined. It will be addressed why spin effects only have a minor influence on the behavior of NO on a rhodium surface.     

Thermochemistry of adducts of some bivalent transition metal bromides with 4-chloroaniline

The compounds [MBr₂(p-clan)₂] (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II); p-clan = 4-chloroaniline) were synthesized and characterized by melting points, elemental analysis, thermal analysis and electronic and IR spectroscopy. The enthalpies of solution of the adducts, metal(II) bromides and 4-chloroaniline in methanol, 1.2 M aqueous HCl or 25% (v/v) 1.2 M aqueous HCl in methanol were measures and by using thermochemical cycles, the following thermochemical parameters for the adducts have been determined: the standard enthalpies for the Lewis acid/base reactions (Δ_rH°), the standard enthalpies of formation (Δ_fH°), the standard enthalpies of decomposition (Δ_DH°), the lattice standard enthalpies (Δ_MH°) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Δ_rH°(g)). The mean bond dissociation enthalpies of the metal(II)-nitrogen coordinated bonds and the enthalpies of adduct formation in the gaseous phase have been estimated.     

Stoffwechselprodukte von Mikroorganismen. 177. Mitteilung. Avilamycin C

From cultures of the Avilamycin (Avilamycin A) producing organism, Streptomyces viridochromogenes, strain ETH 23575, a second antibiotic, Avilamycin C, C₆₁H₉₀Cl₂O₃₂ could be isolated in crystalline form. Both Avilamycins belong to the group of the Orthosomycins. By IR., ¹H- and ¹³C-NMR. spectroscopy and by transformation to a common derivative it could be proven that Avilamycin A is a methyl ketone, Avilamycin C the corresponding methyl carbinol.     

Synthese und Reaktionen von Bicyclo[6.4.0]dodecan-3-carbonsäure-Derivaten

Synthesis and Reactions of the Bicyclo[6.4.0]dodecane-3-carboxylic Acid Derivatives The synthesis and some consecutive reactions of the compounds 5-8 , derivatives of bicyclo[6.4.0]dodecane-3-carboxylic acid ( 1 ), are described. The esters 7 and 8 can be obtained by Baeyer-Villiger oxidation of 2-hydroxy-8-methyltricyclo[7.3.1.0^2,7]tridecan-13-one ( 4 ) and subsequent hydrolysis of the lactone 5 . The structure and configuration of these compounds has been evaluated by spectroscopic techniques (mainly 2D-NMR methods). The formation of 7 via 1,2-H shift and subsequent isomerization to 8 has been studied. The esters 11 and 13 are formed stereospecifically from 7 and 8 .     

Polysulfonylamine. CLX [1] Kristallstrukturen von Metall‐di(methansulfonyl)amiden. 10 [2] Die dreidimensionalen Koordinationspolymere M[(CH3SO2)2N] mit M = Kalium,Rubidium, Caesium (isotype Strukturen für M = K,Rb)

Polysulfonylamines. CLX. Crystal Structures of Metal Di(methanesulfonyl)amides. 10. The Three‐Dimensional Coordination Polymers M[(CH₃SO₂)₂N], where M is Potassium, Rubidium, Cesium (Isotypic Structures for M = K, Rb) Low‐temperature X‐ray crystal structures are reported for KA (monoclinic, space group P2₁/c, Z′ = 1), RbA (isotypic and isostructural with KA), and CsA (monoclinic, P2₁/n, Z′ = 1), where A^— denotes the anion obtained by deprotonation of the strong nitrogen acid (MeSO₂)₂NH. In KA and RbA, the anion is distorted into a rare C₁ conformation, whereas the standard C₂ conformation is retained in the cesium complex. The structures consist of three‐dimensional coordination networks, in which each cation adopts an irregular (O₆N)‐heptacoordination by forming close contacts to one (O, N)‐chelating, one (O, O)‐chelating and three κ¹O‐bonding ligands; however, the coordination number for Cs⁺ is effectively increased to 8 by a very short Cs···Cs contact distance of 422.5 pm. The crystal packings of the isotypic compounds KA and RbA display lamellar layer substructures that involve six independent ligand‐metal bonds and comprise an internal cation lamella and peripheral regions built up from anion monolayers; the 3D framework is completed by one independent M—O bond cross‐linking the layer substructures. In contrast, CsA features anion monolayers that intercalate planar zigzag chains of cations (Cs···Cs alternatingly 422.5 and 487.5 pm, Cs···Cs···Cs 135.7°), whereby each chain is surrounded and coordinated by four anion stacks and each anion stack connects two cation chains. All structures exhibit close C—H···A interanion contacts consistent with weak hydrogen bonding.     

Combinatorial organic materials research (COMR): design,synthesis and screening of a 225-membered materials library of liquid crystalline fluorinated p-quaterphenyls

The rapid solution phase synthesis of novel liquid crystalline materials is demonstrated by utilising combinatorial and parallel methods for the preparation of a library of 225 differently fluorinated 4,4"-dipropyl-p-quaterphenyls. Chemical diversity was introduced into the growing oligomers via a convergent synthetic sequence of iodinations and Suzuki cross-couplings by using various fluorinated phenyl building blocks. A highly efficient rapid parallel purification method was developed that provided HPLC-pure library members in amounts sufficient for the characterization of bulk properties.     

Solid-phase development of chiral phosphoramidite ligands for enantioselective conjugate addition reactions

The development of a method for the optimization of chiral ligands for the steric steering of enantioselective Cu-catalyzed conjugate additions of Znalkyls to enones is described. The method is based on combinatorial principles and solid-phase techniques. It includes the combinatorial synthesis of chiral bispidine-derived ligands embodying a phosphoramidite group on the solid phase and their investigation in immobilized form in the conjugate addition of ZnEt2 to cyclohexenone as test reaction. The best identified ligands were also synthesized separately and investigated in its soluble form. The results obtained for the polymer-bound ligands correctly mirrored the performance of the soluble ligands. The library embodied members giving ee values varying between 3 and 67%. The "positional scanning" approach proved to be invalid for the study of the ligand system, indicating that this approach in general should be applied with care. Taken together, the method allowed for rapid and efficient optimization of the ligands and led to the development of the first enantioselective, Cu-catalyzed conjugate addition reaction with a polymer-bound ligand.     

New membrane materials for potassium-selective ion-sensitive field-effect transistors

Several polymeric materials were studied as membrane materials for potassium-selective ion-sensitive field-effect transistors (ISFETs) to overcome the problems related with the use of conventional plasticized poly(vinyl chloride) membranes casted on ISFET gate surfaces. Several acrylate materials, such as ACE, Epocryl and derivatives, showed no reproducible results. Three room-temperature vulcanizing (RTV)-type silicone rubbers were tested. The addition-type RTV-2 silicone rubber was not suitable as a membrane material, but the condensation-type RTV-1 and especially the RTV-2 silicone rubber showed good results. ISFETs with a Silopren membrane showed a durability of at least 2 months.