Zum Aufbau von RbNa5Be8O11

On RbNa₅Be₈O₁₁ For the first time RbNa₅Be₈O₁₁ was obtained by annealing intimate mixtures of the binary oxides (Rb:Na:Be = 1.1:5.5:8, Ni-cylinder, 650°C, 21d). The compound crystallizes triclinic (P 1 ) with a = 1 063.4 pm, b = 645.6 pm, c = 948.8 pm, α = 110.2º, β = 114.9º, γ = 90.8º, Z = 2. The crystal structure was solved by four-circle-diffractometer data [Siemens AED2, 3099 I₀ (hkl), R = 5.1%, R_w = 3.8%]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, are calculated.     

Ein neuer Perowskit mit Lücken im Anionenteil: Ba4[Na2W2O11]

A New Perowskite with Deficiencies in the Oxygen Part: Ba₄[Na₂W₂O₁₁] For the first time colourless single crystals of Ba₂NaWO_5.5 were prepared by reaction of Na₄WO₅ [2] and ?BaO₂”? [Ba:Na:W = 4:4:1, Ni-cylinder, 725°C, 35 d]. Single crystal data [432 of 505 I₀ (hkl), Four-circle-diffractometer Siemens AED2, MoKα , R = 6.1%, R_w = 5,6%] verify the space group P mmm with a = 579.16(8), b = 580.85(8), c = 859.4(1) pm, Z = 1. The structure is based upon the CaTiO₃-type of structure. Ba²⁺ take the place of Ca²⁺ meanwhile Ti⁴⁺ is substituted alternately by W⁶⁺ and Na⁺. Complete occupation of all lattice positions would lead to a deficite of positive charge. This is compensate by deficiencies in the oxygen part of the lattice. Related to [Na(1)₁Na(2)₁W(1)₁W(2)₁O(1)₄O(2)₂O(3)₂O(4)₃] these deficiencies are statistically distributed on O(4). Structural relations are deduced by Schlegel-Diagrams. The Madelung Part of Lattice Energie, MAPLE, Effektive Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Fluoride mit zweiwertigem Silber. Zur Kenntnis der Verbindungen AgII[MF6] mit M = Ge,Sn, Pb,Ti, Zr,Hf, Rh,Pd, Pt.

Fluorides with divalent Silver. On the compounds Ag^II[MF₆] with M = Ge, Sn, Pb, Ti, Zr, Hf, Rh, Pd, Pt. For the first time AgTiF₆, AgGeF₆, AgSnF₆ AgPbF₆ (all light-blue), AgRhF₆ (black), AgPdF₆ (d.brown), AgPtF₆ (brownviolet) as well as AgZrF₆ and AgHfF₆ (both deeply blueviolet) are prepared. AgSnF₆, AgPbF₆ and AgPdF₆ obey the Curie-Weiss Law (m? = 2,0 m?_B, small θ-value). In the case of AgZrF₆ and AgHfF₆ there is a strong magnetic exchange between Ag²⁺ ions; this may be the cause for the unexpected deep colour.     

Revelation of the nature of the reducing species in titanocene halide-promoted reductions

The fundamental nature of Ti(III) complexes generated in tetrahydrofuran by reduction of Cp(2)TiCl(2) has been clarified by means of cyclic voltammetry and kinetic measurements. While the electrochemical reduction of Cp(2)TiCl(2) leads to the formation of Cp(2)TiCl(2)(-), the use of metals such as Zn, Al, or Mn as reductants affords Cp(2)TiCl and (Cp(2)TiCl)(2) in a mixture having a dimerization equilibrium constant of 3 x 10(3) M(-)(1), independent of the metal used. Thus, we find it unlikely that the trinuclear complexes or ionic clusters known from the solid phase should be present in solution as previously suggested. The standard potentials determined for the redox couples Cp(2)TiCl(2)/Cp(2)TiCl(2)(-), (Cp(2)TiCl)(2)(+)/(Cp(2)TiCl)(2), Cp(2)TiCl(+)/Cp(2)TiCl, and Cp(2)Ti(2+)/Cp(2)Ti(+) increase in the order listed. However, the reactivity of the different Ti(III) complexes is assessed as (Cp(2)TiCl)(2) greater, similar Cp(2)TiCl approximately Cp(2)Ti(+) > Cp(2)TiCl(2)(-) in their reactions with benzyl chloride and benzaldehyde. None of the reactions proceed by an outer-sphere electron transfer pathway, and clearly the inner-sphere character is much higher in the case of Cp(2)Ti(+) than for (Cp(2)TiCl)(2), Cp(2)TiCl, and in particular Cp(2)TiCl(2)(-). As to the electron acceptor, the inner-sphere character increases, going from benzyl chloride to benzaldehyde, and it is suggested that the chlorine atom in benzyl chloride and the oxygen atom in benzaldehyde may function as bridges between the reactants in the transition state.     

Das erste quinquinäre Oxoaurat(I) K6Na[IO6][AuO]2 = K6[NaIO6][AuO2/2]2 [1]

Inhaltsübersicht. Bei Versuchen zur Darstellung unbekannter Phasen im System A/Au/I/O (mit A = Alkalimetall) entstanden durch Erhitzen eines Gemenges (2,2 K₂O + 1,0 NaIO₄; Au-Rohr; 700°C, 59 d) farblose, transparente Einkristalle von K₆NaAu₂IO₈, das nach Einkristalldaten (Vierkreisdiffraktometerdaten, 2465 I_o(hkl), AgKα, R = 6,8% und R_w = 5,6%) monoklin in P2/c mit a = 707,4 pm; b = 977,3 pm; c = 1199,4 pm; β = 122,9°; Z = 2 kristallisiert. Charakteristisch sind die hier erstmals gefundenen, HgO-analogen Zickzackketten [AuO_2/2] längs [001]. Daneben prägen, den NaIO₆-Teil der Struktur betreffend, Ketten aus [IO₆]-Oktaeder, über Na in prismatischer Koordination verknüpft, den Aufbau. The First Quinquinary Oxoaurate(I). K₆Na[IO₆][AuO]₂ = K₆[NaIO₆][AuO_2/2]₂ Attempting to synthesize unknown phases in the system A/Au/I/O by heating a mixture of K₂O and NaIO₄ (K: Na = 2.2:1.0, sealed gold tube, 700°C) we obtained colourless, transparent single crystals of K₆NaAu₂IO₆, a new type of Oxoaurate(I). According to single crystal data K₆NaAu₂IO₈ crystallizes in a monoclinic form with a = 707.4 pm, b = 977.3 pm, c = 1199.4 pm β = 122.9° (Z = 2, space group P2/c). Essential part of the structure are chains NaIO₆ and zigzag chains AuO_2/2, both along [001]. The Madelung part of the lattice energy, MAPLE, and effective coordination numbers, ECoN, are calculated and discussed.     

Determination of inorganic arsenic in white fish using microwave-assisted alkaline alcoholic sample dissolution and HPLC-ICP-MS

An analytical method for the determination of inorganic arsenic in fish samples using HPLC-ICP-MS has been developed. The fresh homogenised sample was subjected to microwave-assisted dissolution by sodium hydroxide in ethanol, which dissolved the sample and quantitatively oxidised arsenite (As(III)) to arsenate (As(V)). This allowed for the determination of inorganic arsenic as a single species, i.e. As(V), by anion-exchange HPLC-ICP-MS. The completeness of the oxidation was verified by recovery of As(V) which was added to the samples as As(III) prior to the dissolution procedure. The full recovery of As(V) at 104±7% (n=5) indicated good analytical accuracy. The uncertified inorganic arsenic content in the certified reference material TORT-2 was 0.186±0.014 ng g^–1 (n=6). The method was employed for the determination of total arsenic and inorganic arsenic in 60 fish samples including salmon from fresh and saline waters and in plaice. The majority of the results for inorganic arsenic were lower than the LOD of 3 ng g^–1, which corresponded to less than one per thousand of the total arsenic content in the fish samples. For mackerel, however, the recovery of As(III) was incomplete and the method was not suited for this fat-rich fish.     

In situ STM imaging and direct electrochemistry of Pyrococcus furiosus ferredoxin assembled on thiolate-modified Au111 surfaces

We have addressed here electron transfer (ET) of Pyrococcus furiosus ferredoxin (PfFd, 7.5 kDa) in both homogeneous solution using edge plane graphite (EPG) electrodes and in the adsorbed state by electrochemistry on surface-modified single-crystal Au111 electrodes, This has been supported by surface microscopic structures of PfFd monolayers, as revealed by scanning tunneling microscopy under potential control (in situ STM). Direct ET between PfFd in phosphate buffer solution, pH 7.9, and EPG electrodes is observed in the presence of promoters. Neomycin gives rise to a pair of redox peaks with a formal potential of ca -430 mV (vs SCE), corresponding to [3Fe-4S]1+/0. The presence of an additional promoter, which can be propionic acid, alanine, or cysteine, induces a second pair of redox peaks at approximately -900 mV (vs SCE) arising from [3Fe-4S]0/1-. A robust neomycin-PfFd complex was detected by mass spectrometry. The results clearly favor an ET mechanism in which the promoting effect of small organic molecules is through formation of promoter-protein complexes. The interaction of PfFd with small organic molecules in homogeneous solution offers clues to confine the protein on the electrode surface modified by the same functional group monolayer and to address diffusionless direct electrochemistry, as well as surface microstructures of the protein monolayer. PfFd molecules were found to assemble on either mercaptopropionic acid (MPA) or cysteine-modified Au111 surfaces in stable monolayers or submonolayers. Highly ordered (2 radical 3 x 5)R30 degrees cluster structures with six MPA molecules in each cluster were found by in situ STM. Individual PfFd molecules on the MPA layer are well resolved by in situ STM. Under Ar protection reversible cyclic voltammograms were obtained on PfFd-MPA/Au111 and PfFd-cysteine/Au111 electrodes with redox potentials of -220 and -201 mV (vs SCE), respectively, corresponding to the [Fe3S4]1+/0 couple. These values are shifted positively by 200 mV relative to homogeneous solution due to interactions between the promoting layers and the protein molecules. Possible mechanisms for such interactions and their ET patterns are discussed.     

Ein Oxostannat neuen Strukturtyps: Cs4[SnO4]

An Oxostannate of a New Structure Type: Cs₄[SnO₄] In order to prepare Cs₃LiSnO₄ by heating of a well ground mixture of the binary oxides [CsO_0.67, Li₂O, SnO₂; Cs:Li:Sn = 3.3:1.0:1.0; 450°C; 28 d; Ni-tube] colourless, monoclinic single crystals of Cs₄[SnO₄] have been yielded for the first time: space group P2₁/c with a = 1180.8 pm. b = 728.2 pm, c = 1166,7 pm, β = 111.79°, Z = 4. The crystal structure was solved by fourcycle-diffractometer data [Siemens AED2, 2299 from 2708 I₀(hkl), R = 7.0%, R_w = 5.6%], parameters see text. Characteristic for the complicated structure are “isolated” [SnO₄]^4? tetrahedra. Mean Fictive Ionic Radii, MEFIR, Effective Coordination Numbers, ECoN and the Madelung Part of Lattice Energy, MAPLE, have been calculated.     

Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction-tools for probing lipopolysaccharide and lipid a membranes from gram-negative bacteria

FT-IR and X-ray techniques were used to get an insight into the structure of synthetic Salmonella lipid A membranes. While FT-IR was sensitively providing structure information at the molecular level from different parts of the molecule, X-ray scattering gave data on long-range order phenomena and on fatty acid chain packing pattern. The lipid A membranes exhibited lamellar structures throughout the temperature range of 4°C to 60°C and showed up to three temperature induced transitions. The main transitionT ₃ at 47°C was assigned to anL –L transition. The weak features atT ₁ andT ₂ localized between 15 and 40°C seemed to be connected to packing phenomena of lipid A aggregates within the distorted lattice.     

Zur Konstitution von Ba2WO3F4 und Ba2MoO3F4

On the Structure of Ba₂Wo₃F₄ and Ba₂MoO₃F₄ Ba₂[WO_2/2O₂F₂]F₂ has been prepared for the first time as colourless single crystals (from powder, Au-tube, 680°C, 90 d). It crystallizes in the monoclinic (C c) crystal system with a = 1151.1, b = 938.2, c = 718.8 pm, ß = 126.17°, Z = 4. d_x = 6.17, d_pyk = 6.13 g · cm^?3. (Fourcirclediffractometer PW 1100, Fa. Philips, MoKα-, ω-2Θ-scan, 1832 I₀(hkl) R = 8.3, R_w = 7.4%). Parameters see in the text. The isotypic Ba₂MoO₃F₄ has been prepared as powder (a = 1147.5, b = 937.0, c = 725.1 pm, ß = 126.42°). The structure shows chains of (WO_2/2O₂F₂) groups along [001]. To establish O^2? and F^? on the positions IR and Raman Spectra are employed. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.