Synthesis,Crystal Structure and Characterization of the Copper Iron Phosphate Cu8Fe2O5(PO4)4

The system CuO‐Fe₂O₃‐P₂O₅ has been investigated by means of the solid state reaction between CuO, Fe₂O₃ and (NH₄)₂HPO₄ in quartz crucibles at 900 °C. The powder samples were characterized by X‐ray diffraction, IR spectroscopy and TG/DTA. Single crystals of a new quaternary phase Cu₈Fe₂P₄O₂₁ were achieved by cooling from the melt of the compound in a sealed, evacuated quartz ampoule. Cu₈Fe₂O₅(PO₄)₄ crystallizes in the monoclinic space group C2/m (No 12) with a = 15.9733(8) Å, b = 5.9438(3) Å, c = 9.5530(5) Å, β = 113.76(1)°, Z = 2. The three‐dimensional framework consists of [FeO₆] octahedra, three different [CuO₅] polyhedra and [PO₄] tetrahedra. Cu₈Fe₂P₄O₂₁ exhibits an incongruently melting point at 945 °C.     

Structure and dynamics of a fluid phase bilayer on a solid support as observed by a molecular dynamics computer simulation

Simulations of a 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine lipid bilayer interacting with a solid surface of hydroxylated nanoporous amorphous silica have been carried out over a range of lipid-solid substrate distances. The porous solid surface allowed the water layer to dynamically adjust its thickness, maintaining equal pressures above and below the membrane bilayer. Qualitative estimates of the force between the surfaces leads to an estimated lipid-silicon distance in very good agreement with the results of neutron scattering experiments. Detailed analysis of the simulation at the separation suggested by experiment shows that for this type of solid support the water layer between surfaces is very narrow, consisting only of bound waters hydrating the lipid head groups and hydrophilic silica surface. The reduced hydration, however, has only minor effects on the head group hydration, the orientation of water molecules at the interface, and the membrane dipole potential. Whereas these structural properties were not sensitive to the presence of the solid substrate, the calculated diffusion coefficient for translation of the lipid molecules was altered significantly by the silica surface.     

Chemical accuracy in ab initio thermochemistry and spectroscopy: current strategies and future challenges

The current state of the art in wavefunction-based electronic structure methods is illustrated via discussions of the most important effects incorporated into a selection of high-accuracy methods chosen from the chemical literature. If one starts with a high-quality correlation treatment, such as provided by the CCSD(T) coupled cluster method, the leading effects include convergence of the results with respect to the 1-particle basis set, (outer)core/valence correlation, scalar relativistic effects and a number of smaller effects. For thermochemical properties such as the heat of formation, the zero-point vibrational energy also becomes important, introducing its own set of difficulties to the computational approach. Changes in the various components as the chemical systems incorporate heavier elements and as the size of the systems grows are also considered. Finally, challenges arising from the desire to extend existing methods to transition metal and heavier elements are considered.     

Synthesis and structure of (Ph4P)2MCl6 (M = Ti, Zr, Hf, Th, U, Np, Pu)

High-purity syntheses are reported for a series of first, second, and third row transition metal and actinide hexahalide compounds with equivalent, noncoordinating countercations: (Ph(4)P)(2)TiF(6) (1) and (Ph(4)P)(2)MCl(6) (M = Ti, Zr, Hf, Th, U, Np, Pu; 2-8). While a reaction between MCl(4) (M = Zr, Hf, U) and 2 equiv of Ph(4)PCl provided 3, 4, and 6, syntheses for 1, 2, 5, 7, and 8 required multistep procedures. For example, a cation exchange reaction with Ph(4)PCl and (NH(4))(2)TiF(6) produced 1, which was used in a subsequent anion exchange reaction with Me(3)SiCl to synthesize 2. For 5, 7, and 8, synthetic routes starting with aqueous actinide precursors were developed that circumvented any need for anhydrous Th, Np, or Pu starting materials. The solid-state geometries, bond distances and angles for isolated ThCl(6)(2-), NpCl(6)(2-), and PuCl(6)(2-) anions with noncoordinating counter cations were determined for the first time in the X-ray crystal structures of 5, 7, and 8. Solution phase and solid-state diffuse reflectance spectra were also used to characterize 7 and 8. Transition metal MCl(6)(2-) anions showed the anticipated increase in M-Cl bond distances when changing from M = Ti to Zr, and then a decrease from Zr to Hf. The M-Cl bond distances also decreased from M = Th to U, Np, and Pu. Ionic radii can be used to predict average M-Cl bond distances with reasonable accuracy, which supports a principally ionic model of bonding for each of the (Ph(4)P)(2)MCl(6) complexes.     

Regioselective reactions of mesyloxymethylazetidinones with nucleophiles I. Cleavage of the azetidinone ring,azetidinone‐aziridine ring transformations

The reaction of 4‐mesyloxymethylazetidin‐2‐one derivatives 3 with ammonia and sodium methoxide was investigated. The two electrophilic centers of the substrate reactesuccessively, resulting in cleavage of the lactam bond and formation of a new aziridine ring. The resulting type 6 and 8 aziridinylacetic acid derivatives are related to the novel 2‐(aziridin‐2‐yl)‐3‐phenylpropionic acid type carboxypeptidase A inhibitors and, as such, potential drug candidates.     

Elaboration and Characterization of Starch/ Poly(caprolactone) Blends

A starch-based biodegradable material was prepared in two steps. Firstly, starch was chemically modified by using formic acid at 20°C to obtained degrees of substitution of about 1.2. The level of destructuration was also assessed using dynamic rheological measurements. Native starch or starch ester were then mixed with poly(caprolactone) and different polyester oligomers were added as compatibilisers and plasticizing agents. PCL oligomers were found to be the most efficient ones. A significant improvement of the elongation at break of starch formate/PCL/oligo PCL blends was achieved.     

Conductive polymer composites (CPC): influence of processing conditions,shear rate and temperature on electrical properties of poly(butylene terephthalate)/poly(amide12-b-tetramethyleneglycol) – carbon black blends

Conductive Polymer Composites (CPC) have been obtained by blending two immiscible polymers, poly(butylene terephthalate) (PBT) and poly(amide12-b-tetramethyleneglycol) (PEBAX) with carbon black (CB). The extrusion process allows to obtain anisotrope co-continuous structures of various morphologies depending on composition and experimental conditions. It is possible to enhance CPC conductivity with appropriate processing temperature (T_p) and screw speed (Ω), without changing the composition of the blend. The best results are obtained with Ω =5 rpm and T_p=260°C. PBT/PEBAX-CB resistivity evolution with T_p and Ω doesn't follow a linear law as expected from previous studies with poly(butylene terephthalate)/poly(ethylene)-CB and poly(butylene terephthalate)/poly(ethylene-co-ethyl acrylate)-CB systems. CB distribution has a more important impact on conductivity than polymers phase morphology. A good control of these parameters is essential to reproduce and optimize electrical properties.     

The influence of selected synthetic aluminium silicates on physicochemical properties of emulsion paints

Synthetic aluminium silicates (AS) consist of amorphous particles with diameters between 5 and 10 μm. They are suited as spacers between the dispersed titanium dioxide pigment particles in emulsion paints, thereby providing an excellent distribution of the pigment. This effect makes a partial replacement up to 50% of titanium dioxide pigments by AS possible. In general the whiteness and the contrast ratio of an AS containing emulsion paints are improved, as well as the scrub resistance in particular cases. The usage of AS also has a favourable influence on the chroma and the brilliance of coloured systems. All these positive effects are primarily controlled by the particle size, porosity, and oil adsorption of the AS. For this reason synthetic aluminium silicates are not just ordinary fillers, but real functional pigment extenders.     

Improvement of the Chemometric Variety Characterization of Wines by Improving the Detection Limit for Aroma Compounds

Headspace–SPME followed by capillary gas chromatography/mass spectrometry was used to investigate 90 German wines originating from different grape varieties, vintages, and growing areas. Aromagrams obtained in single ion monitoring (SIM) and in the full scan detection mode (SCAN) of quadrupole mass spectrometer were compared. Detection limits, reproducibility, and linearity for some aroma relevant substances were estimated over a wide concentration range. The advantages of SIM data set (lower detection limit, better reproducibility and linearity in the smaller concentration ranges) should be reflected in more reliable results in classification of wines. To verify these expectation, classification of variety by discriminant analysis was performed with cross validation using both SIM and SCAN data sets including 19 aroma compounds, respectively.     

Coexistent Phases and their Electrical and Structural Behaviour in the Ternary Re/Mo/O System

In order to complete and improve phase diagrams of transition metal oxides the existence and properties of compounds in the Re/Mo/O system have been investigated. Single crystalline solid solutions Re_1-xMo_xO₂ (0 < x < 0.37) and Mo_1-yRe_yO₂ (0 < y < 0.42) were prepared by Solid State Reactions and Chemical Transport Reactions (CTR) and characterized by means of X-ray-diffraction, ICP-AES, and EPMA. In addition, it was shown that the trioxides Re_1-xMo_xO₃ or Mo_1-yRe_yO₃ respectively, do not prove a distinct solubility. First results on Re-doped Magneli phases of Mo are also discussed. There were found two series of solid solutions Mo_4-zRe_zO₁₁ (0 < z < 0.40) which derive from γ-Mo₄O₁₁ and η-Mo₄O₁₁. The other Magneli phases did not show a significant Re content. Using X-ray diffraction, AFM and optical microscopy the structure and morphology of single crystals has been studied. It was steated that the dioxide solid solutions were very homogeneous and structural phase transitions depending on x or y did not occur. That is in good agreement with measurements of electrical conductivity σ in the temperature range from 20 K to 300 K in which the samples showed the behaviour of metals with lattice defects. The Magneli phases Mo₈O₂₃ and Mo₉O₂₆ turned out to be “narrow gap semiconductors” in the low temperature range with activation energies of less than 0.1 eV. The γ-Mo₄ O_11- and γ-Mo₄O₁₁ crystals, the pure and Re-doped ones, were found as metallic conductors at higher temperatures and below a transition temperature they show a semiconductive behaviour.