Synthesis and characterization of perfluorohexylated poly(3,4-ethylenedioxythiophene)

The perfluorohexylated 3,4-ethylenedioxythiophene 5 was prepared via Mitsunobu reaction of perfluorohexylatyed diol 2 with diethyl 3,4-dihydroxythiophenedicarboxylate followed by decarboxylation. The polymerization of 5 was conducted with both oxidative chemical and electrochemical polymerizations. The polymers were characterized by cyclic voltammogram, UV, IR, TGA and DSC.     

反相高效液相色谱法的多波长同时测定预混合饲料中的脂溶性维生素A，α－E，D_3，K_3

反相高效液相色谱法的多波长同时测定预混合饲料中的脂溶性维生素Ａ，α－Ｅ，Ｄ＿３，Ｋ＿３李桂凤，李缙扬，郝征红，聂燕，孟兆宏，李学春（山东省农业科学院中心实验室济南２５０１００）１前言对脂溶性维生素的分析，被许多国内外分析专家认为是高难度的分析项目。本...     

Structure, Stability and Vibrational Spectra of LaC_5~n(n=-1,0,+1) Clusters

用密度泛含方法研究了ＬａＣ５ｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性及振动光谱，对这个六原子体系提出了三种可能构型，点群结构为Ｃ２ｖ对称性．第一个构型为Ｌａ接在弯曲的Ｃ５链上，第二个是Ｌａ通过二个键与Ｃ５环相连第三个是Ｌａ通过一个键与Ｃ５环相连；结果表明，第一个构型即当Ｌａ接在弯曲的Ｃ５链上时能量最低．振动光谱分析指出，当ｎ＝－１时，第二个构型为局域极小值；当ｎ＝＋１时，第一个和第二个构型为局域极小值；对ｎ＝０，局域极小值没有找到．     

用共振电离飞行时间质谱仪分析土壤中超痕量气态金

采用激光共振电离飞行时间质谱技术（简称ＲＩＳ－ＴＯＦ技术）对土壤中超痕量气态金的含量进行了分析研究。ＲＩＳ－ＴＯＦ谱仪具有极高的灵敏度和很强的选择性，避免了对样品的预富集过程。本文给出了该谱仪对金元素的检测限和６５个土壤中气态金样品的分析结果，以及用中子活化法随机抽样检查的结果。     

真空下X2 (X=Cl、Br)与AgOCN气-固反应机理

在真空条件下完成了X2 (X=Cl、Br)与AgOCN间的气-固异相反应，利用紫外光电子能谱（PES）仪，探测与确定反应产物是XNCO (X=Cl、Br)，并推断其可能为一过渡态反应，生成中间络合物，新键产生与旧键断裂同时进行.     

Preparation and electrochemistry of azobenzene self-assembled monolayers on gold--long range tunneling and end-group hydrogen bonding effect

A series of thiol-functionalied azobenzene derivatives (RAzoCnSH: R=H for n=3-6, abbreviated as AzoCnSH; R=CH(3)CONH for n=4, abbreviated as aaAzoC4SH) on gold electrodes were prepared and their self-assembly and electrochemical properties were studied by cyclic voltammetry. They all formed uniform and reproducible self-assembled monolayers (SAMs) on gold and showed well-behaved voltammetric responses in aqueous solution. Both the length of the alkyl chain spacer and the H-bonding of the end acetamino group had effects on the stability and the electrochemical kinetics of the SAMs, and the effect of the H-bonding was dominant. The surface coverage of the SAMs (AzoCnSH) is gradually increased with an increase of the alkyl chain spacer length, whereas the presence of the terminal acetamino group leads to a greater increase of the surface coverage. At a low scan rate, voltammetric responses corresponding to an irreversible two-electron, two-proton reduction/oxidation of the trans-azobenzene redox center were obtained in the range of +300 mV and -800 mV, which exhibited very large peak-to-peak splitting. At a high scan rate of 500 mV/s, two steps of reversible one-electron, one-proton reduction/oxidation corresponding to the cis-isomer in azobenzene-thiol SAMs (n is odd) was clearly observed between +300 and -200 mV. The apparent electron-transfer rate is decreased with increasing distance between the azobenzene redox center and the gold electrode. The existence of the end acetamino group which restricted the conformational change during the redox process also led to a decrease of the standard rate constant, and this restriction effect is more predominant than the distance effect.     

Morphological effect on spectral property of poly(9,9-dihexylfluorene-alt-2,5-dihexyloxybenzene) films

In this study the optical property and film morphology of a conjugated polymer, poly(9,9-dihexylfluorene-alt-2,5-dihexyloxybenzene) (PF6OC6), are investigated. It is found that the intensity of the 0-1 emission relative to the 0-0 emission in the PL spectra and the full width at the half-maximum (fwhm) of PL spectra of the PF6OC6 films decrease firstly and then increase with increasing the annealing temperature. The polymer films also exhibit different morphological features after annealing at different temperatures. The optical and morphological results suggest that the vibronic structure of PF6OC6 is closely related to the film morphology, and its formation is enhanced in the amorphous (or less ordered) films and inhibited in the ordered films.     

Assembled dendritic titanium catalysts for enantioselective hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene

A new type of dendritic 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN)-derived Schiff-base ligands have been synthesized and applied to the titanium-catalyzed hetero-Diels-Alder reaction of Danishefsky's diene with aldehydes. These reactions afforded the corresponding 2-substituted 2,3-dihydro-4H-pyran-4-ones in quantitative yields and with excellent enantioselectivities (up to 97.2 % ee). The disposition of the dendritic wedges and the dendron size in the ligands were found to have significant impact on the enantioselectivity of the reaction. The recovered dendritic catalyst could be reused without further addition of the Ti source or a carboxylic acid additive for at least three cycles, retaining similar activity and enantioselectivity. The high stability of this type of assembled dendritic titanium catalyst may be attributed to the stabilization effect of large-sized dendron units in the catalyst molecule. The other important phenomenon observed with this catalyst system is that a higher degree of asymmetric amplification has been achieved by attachment of the dendron unit to the chiral ligand, which represents a new advantage of dendrimer catalysts for asymmetric reactions using chiral ligands of lower optical purity.