Tetrakis(acetonitrile)‐dibromo‐nickel(II)‐di‐acetonitrile, [Ni(CH3CN)4Br2]·2CH3CN

[Tetrakis(acetonitrile)‐dibromo‐nickel(II)]‐di‐acetonitrile was obtained from a solution of nickel(II) dibromide in acetonitrile at 258 K. The crystal structure [monoclinic, P2₁/n (no.14), a = 1005.5(5), b = 831.3(5) , c = 1131.7(5) pm, β = 106.263(5)°, V = 908.1(8)·10⁶ pm³, Z = 2, R₁ for 1580 reflections with I₀>2σ(I₀): 0.0505] contains sixfold coordinated Ni^II atoms. Two trans coordinating bromide anions and four equatorial acetonitrile molecules form an elongated octahedron around the central Ni^II atom. [Ni(CH₃CN)₄Br₂] octahedra are connected via hydrogen bonds to neighboring octahedra as well as to solvate acetonitrile molecules.     

Synthese und Kristallstruktur von Cs3AuO2

Synthesis and Crystal Structure of Cs₃AuO₂ Bright orange single crystals of Cs₃AuO₂, sensitive to moisture and atmosphere, are obtained by reacting CsAu with a 1 : 1 molar mixture of Cs₂O and CsO₂ (CsAu : Cs₂O : CsO₂ = 3 : 2 : 2) in sealed silver crucibles under argon atmosphere at 380 °C for a period of 6 days. The crystal structure (Pearsoncode mP72, P2₁/n, a = 1019.6(3), b = 1984.3(7), c = 1028.5(4) pm, β = 93.96(1)°, Z = 12, 2562 reflections mit I_o > 2σ(I), R₁ = 0.0662, wR₂ = 0.1660) is characterized by the presence of dumb‐bell‐shaped [O–Au–O]‐moieties (d(Au–O) = 200,8(2) pm), a common feature of oxoaurates(I).     

Elimination of Hot Cracking in Laser Beam Welding

Hot cracking is one of the big problems in laser beam welding. By multi‐beam welding, first suggested in the 70‐s (cf. [1], [4]), hot cracking can be avoided. Hereby two additional laser beams are employed. These beams generate a compression which compensate for the critical tensile strain in the solid‐liquid region of the weld induced by the main laser beam. However, hot cracking can only be prevented if the positions, sizes, and powers of the additional laser beams are suitably chosen, i.e. are optimized. Non‐optimal values can even enhance hot cracking. Until now these quantities have been found either by trial and error or by prescribing them intuitively. In the present paper a constrained nonlinear programming problem is formulated to solve the problem of hot crack initiation by minimizing the accumulated transverse strain, i.e. the opening displacement, in the solid‐liquid region. This approach is based on the so‐called strip expansion technique, cf. [2]. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Technological Changes in Wheat-Based Breads Enriched with Hemp Seed Press Cakes and Hemp Seed Grit

Hemp and hemp seed press cake—a by-product of hemp oil production—are high-protein, gluten-free raw materials that are often used to enhance the nutritional value of breads. The addition of hemp materials, however, often negatively impacts the technological parameters of breads. Consequently, this study investigated whether and how much the addition of various by-products of hemp seed press cakes to wheat bread mixtures adversely affects the texture and colour profile. The texture profile and colour were determined using a texture analyser and tristimulus measurements. The particle size of raw materials was also measured. Principal component analysis was then used to visualise the correlation between all measured values as well as nutritional parameters. The results showed that the addition of only 1% of some hemp raw materials caused significant technological changes (p > 0.05). Hemp raw materials increased bread hardness and decreased elasticity. The colour of breads containing 1% hemp was also visibly darker than the reference bread. The addition of more hemp led to further darkening and the deterioration of the technological parameters of the products. Consequently, while various hemp materials have high nutritional value, a balance with sensory properties, e.g., textural and colour, has to be reached.     

β-SrNH und β-SrND – Synthese und Kristallstrukturbestimmung mittels Röntgen- und Neutronenbeugung an Pulvern

β-SrNH and β-SrND – Synthesis and Crystal Structure Determination by X-Ray and Neutron Powder Diffraction By reaction of strontium with NH₃ in a flow tube at 750 °C a novel modification of strontium imide, β-SrNH, was obtained as a dark yellow powder. According to X-ray powder diffractometry und crystal structure determination by direct methods β-SrNH and β-SrND adopt a highly distorted variant of the NaCl type of structure (Pnma, a = 757.70(1), b = 392.260(4), c = 569.652(9) pm, Z = 4, wR_p = 0.098, R_p = 0.075, R_F = 0.044). Temperature dependent neutron powder diffraction of β-SrND revealed the position of the D atoms which in contrast to α-SrND are crystallographically ordered. At higher temperatures β-SrNH transforms to α-SrNH.     

Migration Modeling as a Valuable Tool for Exposure Assessment and Risk Characterization of Polyethylene Terephthalate Oligomers

Polyethylene terephthalate (PET) is one of the most widely used food contact materials due to its excellent mechanical properties and recyclability. Migration of substances from PET and assessment of compliance are usually determined by experimental testing, which can be challenging depending on the migrants of interest. Low concentrations and missing reference standards, among other factors, have led to inadequate investigation of the migration potential of PET oligomers. Migration modeling can overcome such limitations and is therefore a suitable starting point for exposure and risk assessment. In this study, the activation energy-based (E_A) model and the A_P model were used to systematically evaluate the migration potential of 52 PET oligomers for 12 different application scenarios. Modeling parameters and conditions were evaluated to investigate their impact and relevance on the assessment of realistic exposures. Obtained results were compared with safety thresholds known from the concept of toxicological thresholds of concern. This allowed the evaluation and identification of oligomers and/or applications where migration or exposure levels may be associated with a potential risk because they exceed these safety thresholds. Overall, this study demonstrated that migration modeling can be a high-throughput, fast, flexible, and suitable approach for comprehensive exposure assessment.     

Non-Directed C−H Arylation of Anisole Derivatives via Pd/S,O-Ligand Catalysis

Non-directed C−H arylation is one of the most efficient methods to synthesize biaryl compounds without the need of the prefuctionalization of starting materials, or the installment and removal of directing groups on the substrate. A direct C−H arylation of simple arenes as limiting reactants remains a challenge. Here we disclose a non-directed C−H arylation of anisole derivatives as limiting reagents with aryl iodides under mild reaction conditions. The arylated products are obtained in synthetically useful yields and the arylation of bioactive molecules is also demonstrated. Key to the success of this methodology is the use of a one-step synthesized S,O-ligand.     

Chemical and Genetic Studies on the Formation of Pyrrolones During the Biosynthesis of Cytochalasans

A key step during the biosynthesis of cytochalasans is a proposed Knoevenagel condensation to form the pyrrolone core, enabling the subsequent 4+2 cycloaddition reaction that results in the characteristic octahydroisoindolone motif of all cytochalasans. In this work, we investigate the role of the highly conserved α,β-hydrolase enzymes PyiE and ORFZ during the biosynthesis of pyrichalasin H and the ACE1 metabolite, respectively, using gene knockout and complementation techniques. Using synthetic aldehyde models we demonstrate that the Knoevenagel condensation proceeds spontaneously but results in the 1,3-dihydro-2H-pyrrol-2-one tautomer, rather than the required 1,5-dihydro-2H-pyrrol-2-one tautomer. Taken together our results suggest that the α,β-hydrolase enzymes are essential for first ring cyclisation, but the precise nature of the intermediates remains to be determined.