Polymorphism of [Zn(2,2′‐bipy)(H2PO4)2]2

Two polymorphs of a zero‐dimensional (molecular) zinc phosphate with the formula [Zn(2,2′‐bipy)(H₂PO₄)₂]₂ have been synthesized by a mild hydrothermal route and their crystal structures were determined by single crystal X‐ray diffraction (triclinic, space group (No. 2), Z = 2, α‐form: a = 8.664(1), b = 8.849(2), c = 10.113(2) Å, α = 97.37(2)°, β = 100.54(2)°, γ = 100.98(2)°, V = 737.5(3) ų; β‐form: a = 7.5446(15), b = 10.450(2), c = 10.750(2) Å, α = 67.32(3)°, β = 81.67(3)°, γ = 69.29(3)°, V = 731.4(3) ų). Both structures consist of distorted trigonal‐bipyramidal ZnO₃N₂ units condensed with PO₂(OH)₂ tetrahedra through common vertices giving rise to dimers [Zn(2,2′‐bipy)(H₂PO₄)₂]₂. The structures are stabilized by extensive inter‐ and intramolecular hydrogen bond interactions. Both modifications display subtle differences in their packing originating from the hydrogen bond interactions as well as π…π interactions between the organic ligands.     

Adsorption and adhesion studies of PdSn‐nanoparticles on protonated amine and carboxylic acid‐terminated surfaces

Electroless plating of acrylonitrile‐butadiene‐styrene‐terpolymers (ABS‐plastics) is used for decorative applications and relies on the immobilization of catalytic palladium‐tin nanoparticles. We used chemical force microscopy to measure the adhesion force of palladium‐tin nanoparticles on a patterned amine and carboxyl‐terminated surface prepared by micro‐contact printing. The kinetics of the adsorption process and the population density of the nanoparticles on amine and carboxyl‐terminated surfaces were monitored by quartz crystal microbalance with dissipation analysis. The surface chemistry was investigated by means of polarization‐modulated infrared reflection absorption spectroscopy and X‐ray photoelectron spectroscopy. Enhanced adhesion and population density of PdSn nanoparticles on protonated amine‐terminated surfaces compared with carboxyl‐terminated surfaces is observed. Copyright © 2016 John Wiley & Sons, Ltd.     

Optically active zwitterionic lambda(5)Si,lambda(5)Si'-disilicates: syntheses, crystal structures, and behavior in aqueous solution

The zwitterionic lambda(5)Si,lambda(5)Si'-disilicates 1-8 were synthesized and characterized by solid-state and solution NMR spectroscopy. In addition, compounds 26 H(2)O, 32 CH(3)CN, 45/2 CH(3)CN, 6CH(3)OH, 7, and 8CH(3)OHCH(3)CN were studied by single-crystal X-ray diffraction. The optically active (Delta,Delta,R,R,R,R)-configured compounds 1-8 contain two pentacoordinate (formally negatively charged) silicon atoms and two tetracoordinate (formally positively charged) nitrogen atoms. One (ammonio)alkyl group is bound to each of the two silicon centers, and two tetradentate (R,R)-tartrato(4-) ligands bridge the silicon atoms. Although these lambda(5)Si,lambda(5)Si'-disilicates contain SiO(4)C skeletons, some of them display a remarkable stability in aqueous solution as shown by NMR spectroscopy and ESI mass spectrometry.     

Characterization of local environments in crystalline borophosphates using single and double resonance NMR

(11)B and (31)P magic-angle spinning as well as (11)B{(31)P} and (31)P{(11)B} rotational echo double resonance (REDOR) NMR have been applied to characterize the local environments in the crystalline borophosphates K(3)[BP(3)O(9)(OH)(3)], NH(4)[ZnBP(2)O(8)] and Rb(3)[B(2)P(3)O(11)(OH)(2)]. Dipolar second moment values extracted from the REDOR curves at short evolution times (DeltaS/S(0) < or = 0.2) are in reasonable agreement with those calculated from the internuclear distances in the corresponding crystal structures. In particular, the method is found to be useful for distinguishing between boron and phosphorus local environments with different numbers of B-O-P connectivities, making REDOR a well-suited tool for medium-range order investigations in glasses.     

Speckle characteristics of a broad-area VCSEL in the incoherent emission regime

We present a technique to reduce the speckle contrast of a NIR broad-area VCSEL based on the spatially incoherent emission regime that can be obtained when using the proper driving conditions. We evaluate the efficiency of this technique to reduce the speckle contrast by comparing it with the speckle characteristics in multimode emission under cw operation. Depending on the illumination setup, the incoherent emission regime can lead to a strongly reduced speckle contrast down to 1.3%. This is in agreement with estimates of the expected speckle contrast reduction when three contrast reducing effects are taken into account. These low contrast values make the investigated sources attractive for several applications that suffer from speckle noise.     

Qualitative and quantitative analysis of carbohydrates in green juices (wild mix grass and alfalfa) from a green biorefinery by gas chromatography / mass spectrometry

Green juices from biorefinery original raw material (wild mix grass and alfalfa after wet fractionation and protein separation) have been investigated by gas chromatography/mass spectrometry. The carbohydrates, involved in the green juices, were derivatized and identified by both their retention times in the gas chromatogram and EI mass spectra compared to those of pure reference compounds. Additionally, chemical ionization mass spectra were recorded for better characterizing the carbohydrates present. The carbohydrates which could thus be identified, were quantified by response signals with respect to that of the internal standard β-phenyl-D-glucopyranoside.     

Aromatic Xanthates and Dithiocarbamates for the Polymerization of Ethylene through Reversible Addition–Fragmentation Chain Transfer (RAFT)

Aromatic xanthates and dithiocarbamates were used as chain‐transfer agents (CTAs) in reversible addition–fragmentation chain‐transfer (RAFT) polymerizations of ethylene under milder conditions (≤80 °C, ≤200 bar). While detrimental side fragmentation of the intermediate radical leading to loss of living chain‐ends was observed before with alkyl xanthate CTAs, this was absent for the aromatic CTAs. The loss of living chain‐ends was nevertheless detected for the aromatic xanthates via a different mechanism based on cross‐termination. Narrow molar‐mass distributions with dispersities between 1.2 and 1.3 were still obtained up to number average molar masses M_n of 1000 g mol^?1. The loss of chain‐ends was minor for dithiocarbamates, yielding polyethylene up to M_n=3000 g mol^?1 with dispersities between 1.4 and 1.8. While systems investigated showed significant rate retardation, the dithiocarbamates are the first CTAs giving polyethylene with a high livingness via RAFT polymerization.     

Über das Verhalten von Potenzreihen mit zwei und drei Veränderlichen an der Konvergenzgrenze

Ohne Zusammenfassung     

Diethoxymethane as tailor-made fuel for gasoline controlled autoignition

Within the cluster of excellence “Tailor-Made Fuels from Biomass”  diethoxymethane (DEM) was identified as a promising fuel candidate from a production perspective. Synthesized by combining a bio-based feedstock and $C{O}_2$ as carbon source together with “green hydrogen” from water electrolysis DEM is defined as “bio-hybrid fuel” . To determine the molecules general applicability to a combustion system and to develop up combustion models a rapid screening of the ignition characteristics is performed in a rapid compression machine and a shock tube. Those suggest DEM being a potential fuel for gasoline controlled autoignition (GCAI) because of a relatively wide range of temperature independent ignition delay, a good autoignition behavior compared to conventional gasoline fuel and a multi-stage ignition behavior. To test the suitability of those molecules as a fuel and determine possible improvements to the production side, DEM was used in a single cylinder research engine operated in GCAI combustion mode. Compared to GCAI combustion with conventional RON95 E10 fuel, DME shows a significantly decreased ignition delay. As a consequence, the internal residual gas fraction, whose enthalpy is used to initiate autoignition, can be reduced and combustion stability is increased. Starting from similar combustion phasing using external exhaust gas recirculation to align the ignition behavior of DEM and RON95 E10, a variation of the intake temperature reveals that DEM has the potential to reduce the sensitivity of the combustion system.