氢键构筑的新颖微孔配位聚合物[Co2(Hisor)2·(4,4′-bpy)2(H2O)2]·4,4′-bpy的合成与结构

A novel microporous coordination polymer [Co2(Hisor)2(4,4′-bpy)2(H2O)2]·4,4′-bpy was synthesized by hydrothermal reaction and characterized by single crystal X-ray diffraction, elemental analysis and IR spectrum. The crystal belongs to the monoclinic system and space group is P2/n with a=1.040 6(3) nm, b=1.138 8(4) nm, c=1.854 7(6) nm, β=102.991(6)°, V= 2.141 6(12) nm3, Z=2, Dc=1.443 Mg/m3, Mr=930.62, μ=0.842 mm-1, F(000)=952, GOF= 1.072, R=0.065 4, wR=0.146 8[I>2σ(I)]. There are two crystallographically independent Co(Ⅱ) ions in the title complex. The Hisor2- and 4,4′-bpy link the metal ions into 2D grids with dimension of 0.522 3 nm×1.138 8 nm. There are O—H…O and N—H…O hydrogen bonds in the complex resulting in the formation of 3D network with 1D channels, in which are free 4,4′-bpy molecules.     

ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE

The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here.     

去溶温度对微波诱导等离子体原子吸收光谱法分析性能影响的研究

本文研究了超声雾化微波诱导等离子体原子吸收光谱法(UN-MIP-AAS)中,去溶温度对选择载气流量、微波前向功率等因素的影响,并定量考察了去溶效果。通过改善去溶条件,提高了UN-MIP-AAS的分析性能。     

Isolation of New Disilanylene-bridged Bis（cyclopentadienyl）tetracarbonyldiiron Complexes and Molecular Structure of [η^5, η^5-C5H4SiMe（SiMePh2）C5H4]Fe2（CO）2（μ-CO）2

1,2-Diphenyl-1,2-dimethyldisilanylene-bridged bis-cyclopentadienyl complex[η~5,η~5-C_5H_4PhMeSiSiMePh-C_5H_4]Fe_2(CO)_2(μ-CO)_2(1)was synthesized by a modified procedure,from which the trans-isomer 1b that was pre-viously difficult to obtain has been isolated for the first time.More interestingly,two new regio-isomers[η~5,η~5C_5H_4SiMe(SiMePh_2)C_5H_4]Fe_2(CO)_2(μ-CO)_2(2)and [η~5,η~5-C_5H_4Me_2SiSiPh_2C_5H_4]Fe_2(CO)_2(μ-CO)_2(3)were occa-sionally obtained during above process,the novel structures of which opened up new options for further study ofthis type of Si—Si bond-containing transition metal complexes.The molecular structure of 2 has been determinedby the X-ray diffraction method.     

Copper‐Bismuth Bimetallic Microspheres for Selective Electrocatalytic Reduction of CO2 to Formate

Electrocatalytic carbon dioxide reduction holds great promise for reducing the atmospheric CO₂ level and alleviating the energy crisis. High‐performance electrocatalysts are often required in order to lower the high overpotential and expedite the sluggish reaction kinetics of CO₂ electroreduction. Copper is a promising candidate metal. However, it usually suffers from the issues of poor stability and low product selectivity. In this work, bimetallic Cu‐Bi is obtained by reducing the microspherical copper bismuthate (CuBi₂O₄) for selectively catalyzing the CO₂ reduction to formate (HCOO^–). The bimetallic Cu‐Bi electrocatalyst exhibits high activity and selectivity with the Faradic efficiency over 90% in a wide potential window. A maximum Faradaic efficiency of ~95% is obtained at –0.93 V versus reversible hydrogen electrode. Furthermore, the catalyst shows high stability over 6 h with Faradaic efficiency of ~95%. This study provides an important clue in designing new functional materials for CO₂ electroreduction with high activity and selectivity.     

STUDY ON THE SWELLING BEHAVIOUR OF COPOLYMER HYDROGEL

The states of water in poly (N-vinylpyrrolidone-methylmethacrylate) and poly (N-vinylpyrroli-done-2-hydroxyethyl methacrylate) hydrogels have been studied by means of DSC. The effect ofpolmer structure on equilibrium swelling extent of water has been examined. It was found that thestate of water and the water content in different hydrogels were dependent on the kind of monomer used,the component of copolymer, the sequence distribution of the monomer unit and the degree of cross-linking (including chemical and physical) to a great extent. The equilibrium water content of thehydrogel may be regarded as the sum of the different state of swollen water contents of the hydrogel.Based on these, a semiempirical formula used to estimate the equilibrium water content of the copolymerhydrogels was presented.     

Determination of trace levels of mercury in water samples based on room temperature phosphorescence energy transfer

A novel method has been developed for the sensitive determination of mercury in aqueous media by room temperature phosphorescence (RTP). The measurement principle is based on the energy transfer (ET) from a phosphor molecule (acting as a donor) to a Hg-sensitive dye (acceptor). To our acknowledgment this is the first RTP method for mercury measurement developed so far. α-Bromonaphthalene (BrN) was selected as the phosphorescent donor molecule (BrN can produce significant RTP emission in aqueous media in a β-cyclodextrin rigid microenvironment without deoxygenation).The absorption spectrum of the complex formed between mercury and the dithizone dye possesses a desirable spectral overlap with the RTP emission spectrum of the donor (BrN), giving rise to a nonradiative ET from the phosphor molecules to the mercury complex. An increase in the concentration of Hg(II) causes an increase on the concentration of the dithizone complex (acceptor) with the subsequent increase of the absorbance and, therefore, resulting in a decrease of the RTP emission. Both, RTP intensities and triplet lifetimes of the BrN decreased with increases on the Hg(II) concentration.Possible interferences present in natural waters, including different cations and anions, which could affect the analytical response, were evaluated and the analytical performance characteristics investigated. The use of phosphorescence measurements (low background noise signals) resulted in an improvement on the sensitivity of the Hg(II) detection higher than five times as compared to the molecular absorption spectrophotometric method for Hg(II) detection based on dithizone as Hg-indicator. A detection limit (D.L.) of 14 ng ml⁻¹ of Hg(II) was obtained by RTP with a precision of ±4.8% for five replicates of 300 ng ml⁻¹ of Hg(II). The usefulness of the method was successfully evaluated by the determination of Hg(II) in spiked natural water samples.     

Baeyer-Villiger单加氧酶在有机合成中的应用

综述了Baeyer-Villiger单加氧酶在有机合成中的应用.较之传统的化学反应, 氧化酶催化剂反应有较好的选择性、可控性和经济性. 环己酮加氧酶是一种还原型辅酶I (NADPH)依赖型氧化酶, 是最早被报道能够催化Baeyer-Villiger氧化的酶. 这些重要反应产生了合成化学家很感兴趣的扩环产物. 环己酮加氧酶也是有用的生物催化剂, 由于辅酶再生的问题已被工程菌克服了, 所以能像全细胞催化剂那样使用. 对酮包括杂环酮进行Baeyer-Villiger氧化和动态动力学拆分, 放大这种反应作为合成路线是很有前途的.     

Influence of amino acid side chain packing on Fe-methionine coordination in thermostable cytochrome C

Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability.     

Controlled ring‐opening polymerization of propylene oxide catalyzed by double metal‐cyanide complex

A double metal‐cyanide catalyst based on Zn₃[Co(CN)₆]₂ was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. ¹³C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002