Untersuchungen an Kobalt-Zink-Hydroxid,Co3Zn2(OH)10, 2H2O

A new cobalt-zinc-hydroxide with the composition Co₃Zn₂(OH)₁₀ · 2 H₂O is described. The X-ray powder diffraction pattern can be indexed with a monoclinic cell, a = 5.49 Å, b = 6.22 Å, c = 15.45 Å, β = 100.7º. A possible structure of this new compound, with cobalt ions in octahedral and zinc ions in tetrahedral coordination, is proposed.     

Kinetics of aquation and anation of ruthenium(II) arene anticancer complexes, acidity and X-ray structures of aqua adducts

The aqua adducts of the anticancer complexes [(eta(6)-X)Ru(en)Cl][PF(6)] (X=biphenyl (Bip) 1, X=5,8,9,10-tetrahydroanthracene (THA) 2, X=9,10-dihydroanthracene (DHA) 3; en=ethylenediamime) were separated by HPLC and characterised by mass spectrometry as the products of hydrolysis in water. The X-ray structures of the aqua complexes [(eta(6)-X)Ru(en)Y][PF(6)](n), X=Bip, Y=0.5 H(2)O/0.5 OH, n=1.5 (4), X=THA, Y=0.5 H(2)O/0.5 OH, n=1.5 (5 A), X=THA, Y=H(2)O, n=2 (5 B), and X=DHA, Y=H(2)O, n=2 (6), are reported. In complex 4 there is a large propeller twist of 45 degrees of the pendant phenyl ring with respect to the coordinated phenyl ring. Although the THA ligand in 5 A and 5 B is relatively flat, the DHA ring system in 6 is markedly bent (hinge bend ca. 35 degrees ) as in the chloro complex 3 (41 degrees ). The rates of aquation of 1-3 determined by UV/Vis spectroscopy at various ionic strengths and temperatures (1.23-2.59x10(-3) s(-1) at 298 K, I=0.1 M) are >20x faster than that of cisplatin. The reverse, anation reactions were very rapid on addition of 100 mM NaCl (a similar concentration to that in blood plasma). The aquation and anation reactions were about two times faster for the DHA and THA complexes compared to the biphenyl complex. The hydrolysis reactions appear to occur by an associative pathway. The pK(a) values of the aqua adducts were determined by (1)H NMR spectroscopy as 7.71 for 4, 8.01 for 5 and 7.89 for 6. At physiologically-relevant concentrations (0.5-5 microM) and temperature (310 K), the complexes will exist in blood plasma as >89 % chloro complex, whereas in the cell nucleus significant amounts (45-65 %) of the more reactive aqua adducts would be formed together with smaller amounts of the hydroxo complexes (9-25 %, pH 7.4, [Cl(-)]=4 mM).     

Structural and morphological changes characterizing reversible de-ammination/re-ammination processes in NiPt(CN)4(NH3)2

The topotactic structural mechanism of de- and re-ammination of single-crystalline NiPt(CN)₄(NH₃)₂ is characterized by means of structural, morphological and thermoanalytical studies. Structural investigations give evidence that the two-dimensional structural motif [NiPt(CN)₄]_∞ determines the mechanism and the kinetics of both processes. It is shown that the degree of reversibility, in particular the exothermic re-ammination, is governed by the conservation of the two-dimensional structural element [NiPt(CN)₄]_∞. Indeed, only one type of bond has to be broken, and reformed, i.e. the two Ni?NH₃ bonds per Ni. Microscopic studies reveal that by starting with single crystals with average dimensions of few tenths of a mm, each cycle of de-and re-ammination leads to a continuous decrease of the size of crystalline domains until an optimum geometry is reached for the given experimental conditions. By semi-quantitative measurements it can be shown that this direction-dependent kinetic course of the overall reaction is controlled by the diffusion of ammonia along the [NiPt(CN)₄]_∞ layers. If the macroscopic size of these layer fragments is very small, i.e. after several cycles of the reversible reaction, this diffusion control becomes negligible. The reaction is controlled by the availability of reactive Ni sites and ammonia, i.e. its partial pressure.     

Die Struktur von Cyclosporin C

The Structure of Cyclosporin C The structure of cyclosporin C ( 2 ), a minor antifungal metabolite from Trichoderma polysporum (Link ex Pers.) RIFAI has been elucidated. Hydrolytic cleavage and spectroscopic evidence show that cyclosporin C is a neutral oligopeptide of 11 amino acids linked together in a 33-membered ring. Cyclosporin C ( 2 ) differs from the main metabolite cyclosporin A ( 1 ) [2] [4] only by containing L-threonine in the place of L-α-aminobutyric acid as has been shown by the conversion of 2 into 1 . ¹³C-NMR. spectra and study of molecular models suggest that cyclosporin C ( 2 ) has the same molecular conformation as 1 , which is best described as a twisted β-pleated sheet held together in a conformationally stable form by intramolecular hydrogen bonding.     

Non-destructive depth profile analysis using synchrotron radiation excited XPS

We have used synchrotron radiation as excitation source in an X-ray photoelectron spectroscopy (XPS) experiment to analyse surface-near element depth profiles non-dectructively. By tuning the photon energy one can vary the kinetic energy of the photoelectrons and in turn the information depth of the measurement. To quantify the sample geometry (e.g. layer thicknesses) model calculations similar as for angle-resolved XPS (ARXPS) measurements are necessary. We have successfully applied this technique to several samples. We will show how to calculate the relative intensities of the peaks, using photoionization cross sections and an experimentally determined analyzer transmission function and the procedure to quantify the geometry for a model sample: natively oxidized Ta covered by carbon contamination. At Sn-doped indium oxide samples we found a sub-monolayer of segregated Sn at the surface which was expected from previous investigations.     

Die Kristallstrukturen von Mn5O8 und Cd2Mn3O8

The crystal structures of Mn₅O₈ and Cd₂Mn₃O₈ are determined from single crystal and high resolution X-ray powder data. Both structures have very similar monoclinic unit cells, space group C–C2/m, and are isotypic: Hence, the true formula of Mn₅O₈ is MnMnO₈. The crystal structure consists of pseudohexagonal Mn^IV sheets (bc) with similar oxygen sheets on either side, giving a distorted octahedral coordination to the Mn^IV. As every fourth Mn^IV is missing in these “main layers”, their composition becomes Mn₃O₈, and chains of coordination octahedra linked by common edges become distinct. Above and below the empty Mn^IV sites are either Mn^II or Cd^II completing the composition MnMnO₈ or Cd₂Mn₃O₈ respectively. Examples of similar “double layer” structures are given.     

Über die spektrale Sensibilisierung von Zinkoxid: I. Sorptionsverhalten von o,o′-Dihydroxyazofarbstoffen

o,o′-Dihydroxyazo compounds are spectral sensitizers for the photosemiconductor properties of zinc oxide. It is shown that 1-(2-hydroxyphenylazo-)-2-naphthol (II) forms a 1:1 Zn complex on the surface of ZnO particles if adsorbed from toluene solution. With most samples of ZnO a Langmuir type adsorption isotherm is obtained. The concentration of the dye at saturation relative to the BET surface of the ZnO particles correponds to a slightly oblique edge-on arrangement of the dye molecules on the surfaces. In the case of ZnO pretreated with propionic acid and having taken up dye in excess of a monolayer, it can be shown by electron microscopy that tail-like complexes (zinc: dye ratio = 1:1) are formed, and that these complexes contain zinc which was originally on the particle surfaces.     

Chemie des 2-Aminospiro[indan-1,3′-pyrrolidin]-Systems

The chemistry of the 2-aminospiro[indan-1,3′-pyrrolidine]system 2-Aminospir[indan-1,3′-pyrrolidines] 1 are easily synthesized from the α-hydroxyiminoketones 6 and 19 (Schemes 2 and 3, and 6 respectively). Removal of the N-acetyl group in the intermediate 8 of the trans series induces transposition to the 3a-aminomethyl-indano[2,1-b]pyrrolidine system. The configurations of all compounds have been determined by ¹H-NMR. spectroscopy.     

Crystal structure of a novel tertiary phosphine coordination complex: dichlorobis(tribenzylphosphine)nickel(II)

The title compound dichlorobis(tribenzylphosphine)nickel(II), Ni[P(CH₂C₆H₅)₃]₂Cl₂, belongs to a type of tertiary phosphine coordination complex, M(PR₃)₂X₂. There are two molecules in the unit cell which do not appear to interact chemically. Both molecules have a trans-square planar configuration with each nickel atom on a center of symmetry. Three benzyl groups are bonded to each phosphorus atom as rotors in a propeller, and the threefold axis is along the P—Ni bond, which has a mean length of 2.23(1) Å. Crystal data: C₄₂H₄₂Cl₂NiP₂, Triclinic, space group , a = 10.4892(15) b = 10.5249(12) c = 19.453(2) Å, = 83.872(8), = 76.839(9), = 62.241(8)°, V = 1850.5(4) ų, Z = 2. There is an intramolecular hydrogen bond between the C3 and C11 atoms.