Silver(I) Clusters Stabilized by the Carba-closo-dodecaboranylethynyl Ligand with O-Donor Coligands and Template Ions

Large silver(I) clusters stabilized by the dianionic carba-closo-dodecaboranylethynyl ligand were obtained. Crystallization of polymeric {Ag₂(12-C≡C-closo-1-CB₁₁H₁₁)}_n from dimethyl sulfoxide afforded [Ag₁₄(12-C≡C-closo-1-CB₁₁H₁₁)₇(DMSO)₁₂] · DMSO that contained an Ag^I₁₀ cage augmented by four Ag^I ions. Crystals of [Ag₁₆(12-C≡C-closo-1-CB₁₁H₁₁)₈(THF)₁₂] · 2THF were obtained from anhydrous THF and {Ag₂(12-C≡C-closo-1-CB₁₁H₁₁)}_n. In the presence of moisture the similar but water-containing complex [Ag₁₆(12-C≡C-closo-1-CB₁₁H₁₁)₈(THF)₁₂(H₂O)₂] · 2.5THF was identified. Both silver(I) clusters are composed of a central octahedral Ag^I₆ unit and ten further silver(I) ions bonded via argentophilic interactions. [Ag₁₄(12-C≡C-closo-1-CB₁₁H₁₁)₇(DMSO)₁₂] · DMSO and [Ag₁₆(12-C≡C-closo-1-CB₁₁H₁₁)₈(THF)₁₂] · 2THF were characterized by elemental analysis and vibrational (IR and Raman) as well as NMR spectroscopy. In addition, the crystal structures of [Ag₂₅(12-C≡C-closo-1-CB₁₁H₁₁)₁₂(CH₃CN)_13.5(OH)] · 0.5CH₃CN and [Ag₂₅(12-C≡C-closo-1-CB₁₁H₁₁)₁₂{(CH₃)₂CO}_13.5(H₂O)Cl] · 15(CH₃)₂CO were determined. Both compounds contain Ag^I₁₄ rhombic dodecahedrons augmented by eleven silver(I) ions. A hydroxide or a chloride template ion is present in the center of the rhombic dodecahedron, respectively.     

Factors Controlling Leaching of Polycyclic Aromatic Hydrocarbons from Petroleum Source Rock Using Nonionic Surfactant

The extraction of polycyclic aromatic hydrocarbons (PAHs) from petroleum source rock by nonionic surfactants with the assistance of microwave irradiation was investigated and the conditions for maximum yield were determined. The results showed that the extraction temperatures and type of surfactant have significant effects on extraction yields of PAHs. Factors such as surfactant concentration, irradiation power, sample/solvent ratio and mixing surfactants (i.e., mixture of surfactant at specific ratio) also influence the extraction efficiencies for these compounds. The optimum temperature for microwave-assisted nonionic surfactant extraction of PAHs from petroleum source rock was 120 °C and the best suited surfactant was Brij 35. The new method showed extraction efficiencies comparable to those afforded by the Soxhlet extraction method, but a reduction of the extraction times and environmentally friendliness of the new nonionic surfactant extraction system are clear advantages. The results also show that microwave-assisted nonionic surfactant extraction is a good and efficient green analytical preparatory technique for geochemical evaluation of petroleum source rock.

     

Solvent-free microextraction techniques in gas chromatography

Microextraction techniques represent a major part of modern sample preparation in the analysis of organic micropollutants. This article provides a short overview of recent developments in solvent-free microextraction techniques. From the first open-tubular trap techniques in the mid-1980s to recent packed-needle devices, different implementations of in-needle packings for microextraction are discussed with their characteristic benefits, shortcomings and possible sampling modes. Special emphasis is placed on methods providing full automation and solvent exclusion. In this context, in-tube extraction and the needle trap are discussed, with an overview of current research on new sorbent materials, together with the requirements for more efficient method development.     

Liquefaction in fluid-saturated soils

Liquefaction phenomena can be observed if fluid-saturated soils are subjected to transient loading conditions, as they arise, for instance, during earthquakes. The term “liquefaction” comprises more specific liquefaction phenomena, such as flow liquefaction, which is an instability phenomenon in loose soils, and cyclic mobility, which is associated with medium-dense to dense soils, where, in contrast to flow liquefaction, the overall stability of the granular assembly is maintained. However, soil liquefaction is always associated with a pore-pressure build-up, which consequently reduces the intergranular frictional forces, and thus, the load bearing capacity of the fluid-saturated soil. In order to model these particular liquefaction phenomena, we proceed from a continuum-mechanical framework based on the Theory of Porous Media (TPM), where the solid skeleton is described as an elasto-(visco)plastic material with isotropic hardening and a stress-dependent failure surface. The numerical solution of the resulting coupled system of partial differential equations is carried out by the finite-element method (FEM). (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Compact high-power end-pumped Nd:YAG laser

We present a compact diode- and end-pumped Nd:YAG laser for material processing with an output power of 238 W, an optical-to-optical efficiency of 48% and a slope efficiency of 60%. This is to the best of our knowledge the highest optical efficiency for a high-power end-pumped Nd:YAG laser.     

Numerical investigation of vacuum-assisted resin transfer moulding (VARTM) within deformable fibre fabrics

The VARTM procedure is a manufacturing step in the production line when building parts made of fibre-reinforced plastics (FRP), such as glass- or carbon fibre-reinforced plastics acronymed GFRP or CFRP, respectively. In the VARTM process, an initially dry (gas-saturated) fibre-fabric is gradually impregnated by resin, where the flow process is, besides the driving injection pressure, governed by the mutual interactions between the fabric, the resin and the ambient air. To predict the mechanical properties of the manufactured structure, simulations are vital. Within the present contribution, the simulation model proceeds from the macroscopic Theory of Porous Media (TPM), which intrinsically accounts for the interplay between the individual components, in particular, the fibre-network, the ambient air and the resin, where the latter two simultaneously percolate through inter-fibrous pore space. The underlying holistic modelling approach allows, on the one hand, for a continuous transition from the fully gas-saturated towards the fully resin-saturated state and, on the other hand, the consideration of the so-called spring-back effect. The presented simulation example investigates the model behaviour within a practically relevant application scenario. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Difunctionalized {closo‐1‐CB11} Clusters: 1‐ and 2‐Amino‐12‐ethynylcarba‐closo‐dodecaborates

Carba‐closo‐dodecaborate anions with two functional groups have been synthesized via a simple two‐step procedure starting from monoamino‐functionalized {closo‐1‐CB₁₁} clusters. Iodination at the antipodal boron atom provided access to [1‐H₂N‐12‐I‐closo‐1‐CB₁₁H₁₀]^? ( 1 a ) and [2‐H₂N‐12‐I‐closo‐1‐CB₁₁H₁₀]^? ( 2 a ), which have been transformed into the anions [1‐H₂N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀]^? (R=H ( 1 b ), Ph ( 1 c ), Et₃Si ( 1 d )) and [2‐H₂N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀]^? (R=H ( 2 b ), Ph ( 2 c ), Et₃Si ( 2 d )) by microwave‐assisted Kumada‐type cross‐coupling reactions. The syntheses of the inner salts 1‐Me₃N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀ (R=H ( 1 e ), Et₃Si ( 1 f )) and 2‐Me₃N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀ (R=H ( 2 e ), Et₃Si ( 2 f )) are the first examples for a further derivatization of the new anions. All {closo‐1‐CB₁₁} clusters have been characterized by multinuclear NMR and vibrational spectroscopy as well as by mass spectrometry. The crystal structures of Cs 1 a , [Et₄N] 2 a , K 1 b , [Et₄N] 1 c , [Et₄N] 2 c , 1 e , and [Et₄N][1‐H₂N‐2‐F‐12‐I‐closo‐1‐CB₁₁H₉]?0.5 H₂O ([Et₄N ]4 a ?0.5 H₂O) have been determined. Experimental spectroscopic data and especially spectroscopic data and bond properties derived from DFT calculations provide some information on the importance of inductive and resonance‐type effects for the transfer of electronic effects through the {closo‐1‐CB₁₁} cage.