Alkyne-functionalized metallocene complexes: Synthesis, structure, and catalytic ethylene polymerization

Reactions of phenylethynyl lithium with substituted cyclopentenones gave the corresponding pendant phenylethynyl substituted cyclopentadienes. Subsequent deprotonation and transmetallation with TiCl₄·2THF, ZrCl₄, and Cp^∗ZrCl₃ yielded the alkyne-functionalized metallocene complexes [C₅Me₄(CCPh)]₂MCl₂ [M = Ti (1), Zr (2)], Cp^∗[C₅Me₄(CCPh)]ZrCl₂ (3), and Cp^∗[C₅H₂R′₂(CCPh)]ZrCl₂ [R′ = Me (4), Ph (5)]. These complexes were fully characterized by ¹H NMR, ¹³C NMR, MS spectra, and elemental analysis. The molecular structure of 2 was determined by single crystal X-ray diffraction analysis. Ethylene polymerization was studied with these complexes in the presence of methylaluminoxane (MAO).     

Synthesis of sulfated dendrimers and studies of their anticoagulant and antiinflammatory activity

Three hyperbranched dendrimers (polyglycidols) and the corresponding sulfated derivatives, differing in the average molecular weight, were synthesized. The compounds obtained were characterized in detail by mass spectrometry and ¹H and ¹³C NMR spectroscopy, enabling estimation of the sizes of the corresponding molecules. Assignment of signals and identification of key structural blocks were performed using 2D homo- and heteronuclear spectroscopy (COSY, HSQC). The spectra of the sulfated derivatives showed the absence of the signals for the glycerol moiety with the free OH groups, that confirms exhaustive sulfation. The studies of antiinflammatory and anticoagulant activities of the polyanionic samples showed that all the compounds manifest weak antiinflammatory activity, however, their anticoagulant activity displayed in preliminary trials seems to be considerable. The results obtained indicate that it is reasonable to study in more detail biological activity of sulfated dendrimers of this type in terms of their anticoagulant properties.     

GO-P25@SA gel beads with excellent separation performance for photocatalytic degradation of rhodamine B

Research on Chemical Intermediates - Photocatalytic treatment of water pollutants has attracted extensive attention due to its low energy consumption, low cost and the avoidance of secondary...     

Synthesis of γ-Aminobutyric Acid-Modified Chitooligosaccharide Derivative and Enhancing Salt Resistance of Wheat Seedlings

Salinity is one of the major abiotic stresses limiting crop growth and productivity worldwide. Salt stress during germination degenerates crop establishment and declines yield in wheat, therefore alleviating the damage of salt stress to wheat seedlings is crucial. Chitooligosaccharide (COS) was grafted with γ-aminobutyric acid based on the idea of bioactive molecular splicing, and the differences in salt resistance before and after grafting were compared. The expected derivative was successfully synthesized and exhibited better salt resistance-inducing activity than the raw materials. By activating antioxidant enzymes such as superoxide dismutases (SOD), catalase (CAT) and phenylalanine ammonia-lyase (PAL) and subsequently eliminating reactive oxygen species (ROS) in a timely manner, the rate of O⁻₂ production and H₂O₂ content of wheat seedlings were reduced, and the dynamic balance of free radical metabolism in the plant body was maintained. A significantly reduced MDA content, reduced relative permeability of the cell membrane, and decreased degree of damage to the cell membrane were observed. A significant increase in the content of soluble sugar, maintenance of osmotic regulation and the stability of the cell membrane structure, effective reduction in the salt stress-induced damage to wheat, and the induction of wheat seedling growth were also observed, thereby improving the salt tolerance of wheat seedlings.     

Nodal Type Bound States for Nonlinear Schrödinger Equations with Decaying Potentials

In this paper, we are concerned with the existence of nodal type bound state for the following stationary nonlinear Schrödinger equation $$-Δu(x)+V(x)u(x)=|u|^{p-1}u, x∈ R^N, N ≥ 3,$$ where 1 < p < (N+2)/(N-2) and the potential V(x) is a positive radial function and may decay to zero at infinity. Under appropriate assumptions on the decay rate of V(x), Souplet and Zhang [1] proved the above equation has a positive bound state. In this paper, we construct a nodal solution with precisely two nodal domains and prove that the above equation has a nodal type bound state under the same conditions on V(x) as in [1].     

Novel thermoresponsive and pH-responsive aggregates from self-assembly of triblock copolymer PSMA-b-PNIPAAm-b-PSMA

A series of novel triblock copolymers of poly(stearyl methacrylate)-b-poly(N-isopropylacrylamide)-b-poly(stearyl methacrylate) (PSMA-b-PNIPAAm-b-PSMA) with different molecular weights was synthesized through carboxyl-terminated trithiocarbonates as a highly efficient RAFT agent via reversible addition-fragmentation chain transfer (RAFT) polymerization. The resultant polymers were characterized by 1H NMR, FT-IR spectroscopy, and GPC. By varying the organic solvent used in the self-assembly procedure and adjusting the copolymer composition, multiple morphologies ranging from vesicles and core-shell spherical aggregates with different dimensions to pearl-necklace-like aggregates were obtained. The aggregates showed thermoresponsive and pH-responsive properties through the lower critical solution temperature (LCST) of PNIPAAm and the two carboxyl end groups of the copolymer.     

Parallel-oriented fibrogenesis of a beta-sheet forming peptide on supported lipid bilayers

Peptide self-assembly on substrates is currently an intensively studied topic that provides a promising strategy for fabrication of soft materials and is also important for revealing the surface chemistry of amyloidogenic proteins that aggregate on cell membranes. We investigated the fibrogenesis of a beta-sheet forming peptide Abeta(26-35) on supported lipid bilayers (SLBs) by in situ atomic force microscopy (AFM), circular dichroism (CD), and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The results show that the Abeta(26-35) nanofilaments' growth is oriented to a specific direction and formed a highly ordered, large-scale, parallel-oriented surface pattern on membranes. The parallel-oriented fibrogenesis of Abeta(26-35) was able to occur on different lipid membranes rather than on solid substrates. It implies that the parallel-oriented fibrogenesis was associated with the distinct properties of lipid membranes, such as the fluid nature of lipid molecules on membranes. The membrane fluidity may allow the peptide assemblies to float at the water-membrane interface and easily orient to an energetically favorable state. These results provide an insight into the surface chemistry of peptide self-assembly on lipid membranes and highlight a possible way to fabricate supramolecular architectures on the surface of soft materials.     

Thermal degradation properties of LDPE insulation for new and aged fine wires

Journal of Thermal Analysis and Calorimetry - ZnO–SnO2 nanostructures are of great interest in practical applications such as optoelectronic devices, gas sensors and catalyst supports due to...     

Synthesis, Crystal Structure and Magnetic Behaviour of {[Yb(1,4-BDC)1.5(H2O)4]·H2O}n (1,4-BDC?=?1,4-benzenedicarboxylate)

Abstract  

The title complex {[Yb(1,4-BDC)_1.5(H₂O)₄]·H₂O}_n (1) (1,4-BDC = 1,4-benzenedicarboxylate) has been hydrothermally synthesized and structurally characterized by the single crystal X-ray diffraction. Crystals of compound 1 belongs to the triclinic crystal system, space group P-1; a = 7.549(3) ?, b = 10.072(4) ?, c = 10.470(4) ?, α = 87.810(4)°, β = 82.531(4)°, γ = 86.306(4)°, V = 787.3(5) ?³, Z = 2. The Yb(III) atoms are linked by the deprotonated 1,4-BDC ligands in two kinds of bridging modes. Four Yb(III) atoms at each corner (nodes) and four 1,4-BDC ligands at each edge (spacers) form a edge–sharing 36-membered rings. The rhombohedral Yb₄(1,4-BDC)₄ arranged in an alternating fashion to construct a 1D ladder-like chain along the c axis. Two neighboring chains are linked to each other in a parallel fashion to construct 3D supramolecular structure by O–H···O hydrogen bonds and π–π stacking interactions. In addition, the properties of thermogravimetric analysis and magnetic behaviors of the complex have been also discussed.     

The Improvement of Superconductivity in PbxBi2-xSr2CaCu2Oy

In this paper we present the results of recent studies on the improvement of superconductivity in Pb_xBi_2-xSr₂CaCu₂O_y single crystals by preventing impurities incorporation, employing ZrO₂ crucible for crystal growth and post annealing the as-grown crystals in vacuum or argon. It is realized that the superconductivity of as-grown crystals is improved.