Efficient CO2 Insertion and Reduction Catalyzed by a Terminal Zinc Hydride Complex

The terminal zinc hydride complex [Tntm]ZnH ( 2 ; Tntm=tris(6‐tert‐butyl‐3‐thiopyridazinyl)methanide) is an efficient hydrosilylation catalyst of CO₂ at room temperature without the need of Lewis acidic additives. The inherent electrophilicity of the system leads to selective formation of the monosilylated product (MeO)₃SiO₂CH (at room temperature with a TOF of 22.2 h^?1 and at 45 °C with a TOF of 66.7 h^?1). In absence of silanes, the intermediate formate complex [Tntm]Zn(O₂CH) ( 3 ) is quantitatively formed within 5 min. All complexes were fully characterized by ¹H and ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction analyses. Density functional theory (DFT) calculations reveal a high positive charge on zinc and the increased preference of the ligand to adopt a κ³‐coordination mode.     

Surface treatment of polymers by an ultraviolet laser to improve adhesion quality

The results of studies on the use of an excimer laser with a wavelength of 193 nm are presented for the treatment of surface of polymers to improve adhesion. It is shown that the radiation of coherent waves in the ultraviolet range leads to a change in surface topography and increase in its specific area, which contributes to increasing the mechanical adhesion; in addition, laser exposure activates the surface of the polymers, intensifying adsorption adhesive interaction.     

Charge-symmetry-breaking nucleon form factors

A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon??s strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for ⁴He.     

How close can you get? Studies of ultrafast light-induced processes in ruthenium-[60] fullerene dyads with short pyrazolino and pyrrolidino links

Two pyrazoline- and one pyrrolidine-bridged Ru(II)bipyridine-[60]fullerene dyads have been prepared and studied by ultrafast time-resolved spectroscopy. A silver-assisted synthesis route, in which Ag(I) removes the chlorides from the precursor complex Ru(bpy) 2Cl 2 facilitates successful coordination of the [60]fullerene-substituted third ligand. Upon light excitation of the ruthenium moiety, the emission was strongly quenched by the fullerene. The main quenching mechanism is an exceptionally fast direct energy transfer ( k obs > 1 x 10 (12) s (-1) in the pyrazoline-bridged dyads), resulting in population of the lowest excited triplet state of fullerene. No evidence for electron transfer was found, despite the extraordinarily short donor-acceptor distance that could kinetically favor that process. The observations have implications on the ongoing development of devices built from Ru-polypyridyl complexes and nanostructured carbon, such as C 60 or nanotubes.     

Analysis of high-molecular-weight fructan polymers in crude plant extracts by high-resolution LC-MS

The main water-soluble carbohydrates in temperate forage grasses are polymeric fructans. Fructans consist of fructose chains of various chain lengths attached to sucrose as a core molecule. In grasses, fructans are a complex mixture of a large number of isomeric oligomers with a degree of polymerisation ranging from 3 to >100. Accurate monitoring and unambiguous peak identification requires chromatographic separation coupled to mass spectrometry. The mass range of ion trap mass spectrometers is limited, and we show here how monitoring selected multiply charged ions can be used for the detection and quantification of individual isomers and oligomers of high mass, particularly those of high degree of polymerization (DP > 20) in complex plant extracts. Previously reported methods using linear ion traps with low mass resolution have been shown to be useful for the detection of fructans with a DP up to 49. Here, we report a method using high-resolution mass spectrometry (MS) using an Exactive Orbitrap MS which greatly improves the signal-to-noise ratio and allows the detection of fructans up to DP = 100. High-sugar (HS) Lolium perenne cultivars with high concentrations of these fructans have been shown to be of benefit to the pastoral agricultural industry because they improve rumen nitrogen use efficiency and reduce nitrous oxide emissions from pastures. We demonstrate with our method that these HS grasses not only contain increased amounts of fructans in leaf blades but also accumulate fructans with much higher DP compared to cultivars with normal sugar levels.     

Liposome electrokinetic capillary chromatography in the study of analyte-phospholipid membrane interactions. Application to pesticides and related compounds

Interactions between low-molar mass analytes and phospholipid membranes were studied by liposome electrokinetic capillary chromatography (LEKC). The analytes were pesticides, some degradation products, and compounds associated with the manufacture of pesticides. Negatively charged liposome dispersions with different zwitterionic lipids (PC) were applied to the determination of retention factors (k) of 15 charged and uncharged compounds. The liposome dispersions consisted of 80:20 mol% of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/POPS, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/POPS. Retention factors were calculated from the effective electrophoretic mobilities of the analytes under LEKC and CZE conditions and from the effective electrophoretic mobilities of the liposomes, determined by CZE with a polyacrylamide-coated capillary. Determining the liposome mobilities in this way proved to be a good alternative to the conventional method employing a liposome marker compound. The log k values of the analytes for the different liposome dispersed phases were correlated with one another. In addition, correlation curves were determined between log k and calculated octanol-water partition coefficients. The results showed that the zwitterionic phospholipid in the liposome has a major impact on the interactions between the tested compounds and the lipid membranes.