聚甲基苯基硅氮硅氧烷-鈀络合物结构的X-射线光电子能谱(XPS)研究

<正> 近年来,高分子金属催化剂由于其特殊的高分子效应引起人们广泛关注,目前在国外市场上已有高分子金属催化剂商品供应,它较低分子有机金属催化剂活性更高,选择性更好,并已广泛用于加氢,硅氢加成,转化,醛化,分解,齐聚,聚合和不对称合成等很多反应中,然而对其结构的研究至今报道甚少。     

Interaction of zinc finger ZNF191(243—368) and its I323 W and R327W mutants with oligonucleotides by florescence spectrum

Two mutants of the zinc finger protein, ZNF191 (243–368) I323W and R327W, are successfully obtained by site-directed mutagenesis. The fluorescence spectrum is used to study the interaction between these two mutants and the oligonucleotides. The influence of the mutation on the interaction has been studied using ethidium bromide (EB) as the fluorescence probe. The binding constants of the I323W-DNA and R327W-DNA have been calculated and the possible binding models have been discussed.     

Kinetic mechanism of methanol decomposition on Ni(111) surface: a theoretical study

The decomposition of methanol on the Ni(111) surface has been studied with the pseudopotential method of density functional theory-generalized gradient approximation (DFT-GGA) and with the repeated slab models. The adsorption energies of possible species and the activation energy barriers of the possible elementary reactions involved are obtained in the present work. The major reaction path on Ni surfaces involves the O-H bond breaking in CH(3)OH and the further decomposition of the resulting methoxy species to CO and H via stepwise hydrogen abstractions from CH(3)O. The abstraction of hydrogen from methoxy itself is the rate-limiting step. We also confirm that the C-O and C-H bond-breaking paths, which lead to the formation of surface methyl and hydroxyl and hydroxymethyl and atom hydrogen, respectively, have higher energy barriers. Therefore, the final products are the adsorbed CO and H atom.     

甲烷在Ni表面及La薄膜上激活解离化学吸附

利用分子束技术改变甲烷的平动能E_k来研究E_k及其法向分量E_n对甲烷在Ni表面及La薄膜上激活解离吸附的影响。对CH_4/Ni及CH_4/La系统, 当甲烷的平动能E_k分别低于58.5 kJ·mol~(-1)及52.3 kJ·mol~(-1)时, 没观察到甲烷的解离吸附。当甲烷的平动能超过此阈值时, 即对CH_4/Ni系统, 当Ek=58.5增至63.8 kJ·mol~(-1)时, 初始沾着几率s_0由0至0.54线性增加; 对CH_4/La系统, 当E_k=52.3增至63.8 kJ·mol~(-1)时, S_0由0至0.49线性增加。这些结果表明, 两个系统的化学吸附是不经过前趋态的直接化学吸附。最后求出CH_4/Ni, CH_4/La系统的表观活化能分别为46.8 kJ·mol~(-1)和38.1 kJ·mol~(-1)。     

SYNTHESIS AND CHARACTERIZATION OF A NOVEL BLUE LIGHT EMITTING ROD-COIL DIBLOCK OLIGOMER

Four new rod-coil diblock molecules, which had well-defined para-phenylene oligomers (PPP, from biphenyl toquinquephenyl) as rigid segments and poly(ethylene oxide) (PEO, M_w ca. 750) as flexible segments, were synhesized. Thechemical structure and the number of repeating unit in PEO coil and PPP rod were characterized by ~1H-NMR and MALDI-TOF mass spectromeny. The diblock oligomers showed good solubility in common organic solvents and aggregated in wateras characterized by a blue shift in UV-vis absorption spectra, a red shift in emission spectra, quenching of the fluorescenceand formation of the microfibrilla and fractal-like structures. The formation of different supramolecular structures meant thatthis effort might lead to commercial important highly organized functional materials.     

Effects of hydrothermal post-treatment on microstructures and morphology of titanate nanoribbons

Titanate nanoribbons were prepared via a hydrothermal treatment of rutile-type TiO₂ powders in a 10 M NaOH solution at 200 °C for 48 h. The as-prepared titanate nanoribbons were then hydrothermally post-treated at 150 °C for 12-36 h. The titanate nanoribbons before and after hydrothermal post-treatment were characterized with FESEM, XRD, TEM, UV-VIS and nitrogen adsorption-desorption isotherms. The results showed that the hydrothermal post-treatment not only promoted the phase transformation from titanate to anatase TiO₂, but also was beneficial to the removal of Na⁺ ions remained in the titanate nanoribbons. After hydrothermal post-treatment, the TiO₂ samples retained the one-dimensional structure feature of the titanate nanoribbons and showed an obvious increase in the specific surface area and the pore volume.     

聚醚桥连二异羟肟酸单核和双核过渡金属配合物催化PNPP水解

Two polyether bridged dihydroxamic acids and their mono-and binuclear manganese(Ⅱ), zinc(Ⅱ) complexes have been synthesized and employed as models to mimic hydrolase in catalytic hydrolysis of p-nitrophenyl picolinate (PNPP). The reaction kinetics and the mechanism of hydrolysis of PNPP have been investigated. The kinetic mathematical model for PNPP cleaved by the complexes has been proposed. The effects of the different central metal ion, mono-and binuclear metal, the pseudo-macrocyclic polyether constructed by polyethoxy group of the complexes, and reactive temperature on the rate for catalytic hydrolysis of PNPP have been examined. The results showed that the transition metal dthydroxamates exhibited high catalytic activity to the hydrolysis of PNPP, the catalytic activity of binuclear complexes was higher than that of mononuclear ones, and the pseudo-macrocyclic polyether might synergetically activate H20 coordinated to metal ion with central metal ion together and promote the catalytic hydrolysis of PNPP.     

Evaluation of an on-line coupled continuous flow liquid membrane extraction and precolumn system as trace enrichment technique by liquid chromatographic determination of bisphenol A

An on-line coupled continuous flow liquid membrane extraction (CFLME) and C₁₈ precolumn system was developed for sample preconcentration in liquid chromatography determination. After preconcentration by CFLME, which is based on the combination of continuous flow liquid–liquid extraction and supported liquid membrane, bisphenol A (BPA) was enriched in 960 μl of 1 mol l⁻¹ NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C₁₈ precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto a C₁₈ analytical column for separation and detected at 220 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor, and enrichment time were optimized. The proposed method presents a detection limit of 0.03 μg l⁻¹ (S/N=3) when 60 ml samples was enriched with an enrichment time of 30 min. Compared with C₁₈ based column-switching procedure, this proposed procedure presents similar sample throughput and lower detection limits. The proposed method was successfully applied to determine BPA in tap water, river water, and municipal sewage effluent samples.     

DNA Interactions of a Dinuclear Ruthenium(II) Complex Bridged by 1,3-bis(1,10-phenanthroline[5,6-d]imidazol-2-yl)benzene

A novel dinuclear ruthenium(II) complex [(phen)₂Ru(mbpibH₂)Ru(phen)₂]⁴⁺ [phen = 1,10-phenanthroline; mbpibH₂ = 1,3-bis(1,10-phenanthroline[5,6-d]imidazol-2-yl)-benzene] has been synthesized and characterized. The DNA-binding behavior of this complex has been studied by spectroscopic and viscosity measurements. Results suggest that the dinuclear ruthenium(II) complex intercalates into DNA base pairs via its bridging moiety. It has also been found that the dinuclear ruthenium(II) complex displays the enantiopreferential DNA-binding after equilibrium dialysis.     

Interactions of Some Amino Acids with Aqueous N,N-Dimethylacetamide Solutions at 298.15 and 308.15 K: A Volumetric Approach

The apparent molar volumes, V _φ , of glycine, L-alanine and L-serine were obtained in aqueous 0 to ∼4 mol⋅kg⁻¹ N,N-dimethylacetamide (DMA) solutions from density measurements at 298.15 and 308.15 K. The standard partial molar volume, V _φ ^o, and standard partial molar volumes of transfer, Δ_tr V _φ ^o, were determined for these amino acids. It has been shown that hydrophilic-hydrophilic interactions between charged groups of the amino acids and the —CON= group of DMA are predominant in the case of glycine and L-serine, but for L-alanine the interactions between its side group (—CH₃) and DMA are predominant. An increase in temperature increases the standard partial molar volumes but decreases the transfer volumes of the amino acids. The results have been interpreted in terms of cosphere overlap model.