Photoluminescence properties of the composite of porous alumina and poly (2,5-dibutoxy-1,4 phenylenevinylene)

The spin coating method was used to assemble polymer (Poly (2,5-dibutoxy-1,4-phenylenevinylene)) (DBO-PPV) into the pores of porous alumina which was prepared by anodization. Four peaks in the photoluminescence (PL) spectra of the composite, with contributions from the DBO-PPV and porous alumina, were found. It was also found that the light emitting from the porous alumina could excite the photoluminescence of DBO-PPV. The nanometer effect of the porous alumina can lead to a blue shift of 90 nm of the PL peaks of DBO-PPV.     

A density functional study on a biomimetic non-heme iron catalyst: insights into alkane hydroxylation by a formally HO-FeV=O oxidant

The reactivity of [HO-(tpa)Fe(V)=O] (TPA=tris(2-pyridylmethyl)amine), derived from O-O bond heterolysis of its [H(2)O-(tpa)Fe(III)-OOH] precursor, was explored by means of hybrid density functional theory. The mechanism for alkane hydroxylation by the high-valent iron-oxo species invoked as an intermediate in Fe(tpa)/H(2)O(2) catalysis was investigated. Hydroxylation of methane and propane by HO-Fe(V)=O was studied by following the rebound mechanism associated with the heme center of cytochrome P450, and it is demonstrated that this species is capable of stereospecific alkane hydroxylation. The mechanism proposed for alkane hydroxylation by HO-Fe(V)=O accounts for the experimentally observed incorporation of solvent water into the products. An investigation of the possible hydroxylation of acetonitrile (i.e., the solvent used in the experiments) shows that the activation energy for hydrogen-atom abstraction by HO-Fe(V)=O is rather high and, in fact, rather similar to that of methane, despite the similarity of the H-CH(2)CN bond strength to that of the secondary C-H bond in propane. This result indicates that the kinetics of hydrogen-atom abstraction are strongly affected by the cyano group and rationalizes the lack of experimental evidence for solvent hydroxylation in competition with that of substrates such as cyclohexane.     

铌酸锂单晶光纤包层研究

通过镁离子内扩散铌酸锂单晶光纤，以改变晶纤表层的折射率，首次在国内实现了沿不同轴向生长、不同掺杂的铌酸锂单晶光纤的芯－包层波导结构。通过匹配扩散温度、扩散时间、ＭｇＯ膜厚等扩散参数及选择合适的晶纤直径，实现了晶纤具有阶跃和抛物折射率分布的包层，并对包层晶纤的模式特性进行了观察，得到低次模传输。     

Application of high-field NMR and cryogenic probe technologies in the structural elucidation of poecillastrin a,a new antitumor macrolide lactam from the sponge poecillastra species

Poecillastrin A (1), a new polyketide-derived macrolide lactam, was isolated from a deep-water collection of the marine sponge Poecillastra species. The structure of poecillastrin A (1) was assigned using NMR data acquired at 500 MHz with an inverse-detection cryogenic probe and at 800 MHz with a room-temperature probe.     

棕榈油中脂肪酸的GC/MS定性分析

本文介绍了进口棕榈油中的脂肪酸的色-质联用分析方法。其中,特别检测了油中的奇碳数脂肪酸,并和其它食用油中的脂肪酸作了比较。     

Mechanistic studies on the formation and reactivity of dioxygen adducts of diiron complexes supported by sterically hindered carboxylates

Dioxygen activation by enzymes such as methane monooxygenase, ribonucleotide reductase, and fatty acid desaturases occurs at a nonheme diiron active site supported by two histidines and four carboxylates, typically involving a (peroxo)diiron(III,III) intermediate in an early step of the catalytic cycle. Biomimetic tetracarboxylatodiiron(II,II) complexes with the familiar "paddlewheel" topology comprising sterically bulky o-dixylylbenzoate ligands with pyridine, 1-methylimidazole, or THF at apical sites readily react with O(2) to afford thermally labile peroxo intermediates that can be trapped and characterized spectroscopically at low temperatures (193 K). Cryogenic stopped-flow kinetic analysis of O(2) adduct formation carried out for the three complexes reveals that dioxygen binds to the diiron(II,II) center with concentration dependences and activation parameters indicative of a direct associative pathway. The pyridine and 1-methylimidazole intermediates decay by self-decomposition. However, the THF intermediate decays much faster by oxygen transfer to added PPh(3), the kinetics of which has been studied with double mixing experiments in a cryogenic stopped-flow apparatus. The results show that the decay of the THF intermediate is kinetically controlled by the dissociation of a THF ligand, a conclusion supported by the observation of saturation kinetic behavior with respect to PPh(3), inhibition by added THF, and invariant saturation rate constants for the oxidation of various phosphines. It is proposed that the proximity of the reducing substrate to the peroxide ligand on the diiron coordination sphere facilitates the oxygen-atom transfer. This unique investigation of the reaction of an O(2) adduct of a biomimetic tetracarboxylatodiiron(II,II) complex provides a synthetic precedent for understanding the electrophilic reactivity of like adducts in the active sties of nonheme diiron enzymes.     

Copper(II) complexes of pyridyl-appended diazacycloalkanes: synthesis, characterization, and application to catalytic olefin aziridination

As part of an ongoing effort to rationally design new copper catalysts for olefin aziridination, a family of copper(II) complexes derived from new tetradentate macrocyclic ligands are synthesized, characterized both in the solid state and in solution, and screened for catalytic nitrene transfer reactivity with a representative set of olefins. The pyridylmethyl-appended diazacycloalkane ligands L6(py)2, L7(py)2, and L8(py)2 are prepared by alkylation of the appropriate diazacycloalkane (piperazine, homopiperazine, or diazacyclooctane) with picolyl chloride in the presence of triethylamine. The ligands are metalated with Cu(ClO4)(2).6H2O to provide the complexes [(L6(py)2)Cu(OClO3)]ClO4 (1), [(L7(py)2)Cu(OClO3)]ClO4 (2), and [(L8(py)2)Cu](ClO4)2 (3), which, after metathesis with NH4PF6 in CH3CN, afford [(L6(py)2)Cu(CH3CN)](PF6)2 (4), [(L7(py)2)Cu(CH3CN)](PF6)2 (5), and [(L8(py)2)Cu](PF6)2 (6). All six complexes are characterized by X-ray crystallography, which reveals that complexes supported by L6(py)2 and L7(py)2 (1, 2, 4, 5) adopt square-pyramidal geometries, while complexes 3 and 6, ligated by L8(py)2 feature tetracoordinate, distorted-square-planar copper ions. Tetragonal geometries in solution and d(x2 - y2), ground states are confirmed for the complexes by a combination of UV-visible and EPR spectroscopies. The divergent flexibility of the three supporting ligands influences the Cu(II)/Cu(I) redox potentials within the family, such that the complexes supported by the larger ligands L7(py)2 and L8(py)2 (5 and 6) exhibit quasi-reversible electron transfer processes (E1/2 approximately -0.2 V vs Ag/AgCl), while the complex supported by L6(py)2 (4), which imposes a rigid tetragonal geometry upon the central copper(II) ion, is irreversibly reduced in CH3CN solution. Complexes 4-6 are efficient catalysts (in 5 mol % amounts) for the aziridination of styrene with the iodinane PhINTs (in 80-90% yields vs PhINTs), while only 4 exhibits significant catalytic nitrene transfer reactivity with 1-hexene and cyclooctene.     

Room-temperature multiferroic properties of Co-doped KNbO3 ceramics

KNb_0.95Co_0.05O₃ (KN–Co) ceramic was prepared via a solid-state reaction method, and the effect of cobalt dopant on the structural, electric, and magnetic properties was studied. The KN–Co ceramic with polycrystalline perovskite structure exhibited ferromagnetic and ferroelectric properties simultaneously at room temperature, and the coupling of them was confirmed by a large magnetocapacitance effect (about 13%) near the Curie temperature. The possible causes for the magnetism and magnetoelectric properties are discussed.