Migration behavior and enantioseparation of hydrobenzoin and structurally related compounds in capillary zone electrophoresis with a dual cyclodextrin system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-cyclodextrin and beta-cyclodextrin

Migration behavior and enantioseparation of racemic hydrobenzoin and structurally related compounds, including benzoin and benzoin methyl ether, in CZE with a dual CD system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-CD (SI-S-beta-CD) and beta-CD as chiral selectors in the presence and absence of borate complexation at pH 9.0 were investigated. The results indicate that enantioseparation of hydrobenzoin is mainly governed by CD complexation of hydrobenzoin-borate complexes with SI-S-beta-CD when SI-S-beta-CD concentration is relatively high. Whereas CD complexation of hydrobenzoin-borate complexes with beta-CD plays a significant role in enantioseparation when SI-S-beta-CD concentration is comparatively low. The (S,S)-enantiomer of the hydrobenzoin-borate complex was found to interact more strongly than the corresponding (R,R)-enantiomer with both SI-S-beta-CD and beta-CD. These two types of CD show the same chiral recognition pattern, but they exhibit opposite effects on the mobility of the enantiomers of hydrobenzoin-borate complexes. Enantiomer migration reversal of hydrobenzoin occurred in the presence of borate complexation when varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. Binding constants of the enantiomers of benzoin-related compounds to beta-CD and those of hydrobenzoin-borate complexes to SI-beta-CD were evaluated; the mobility contributions of all complex species to the effective mobility of the enantiomers of hydrobenzoin as a function of beta-CD concentration in a borate buffer were analyzed. In addition, comparative studies on the enantioseparation of benzoin-related compounds with SI-S-beta-CD and with randomly sulfate-substituted beta-CD were made.     

Comparative study of electrochemically directed assembly versus conventional self-assembly of thioacetyl-terminated oligo(phenylene ethynylene)s on gold and platinum surfaces

The assembly of thioacetyl-terminated oligo(phenylene ethynylene)s (OPEs) on Au and Pt surfaces under an electric potential (electrochemical assembly, EA) was compared to assembly at an open circuit (conventional self-assembly, CSA). Cyclic voltammetry and ellipsometry were used to characterize the adsorption kinetics of self-assembled monolayers formed by these two techniques. The adsorption rate of the EA was remarkably faster at positive potentials but slower at negative potentials than that of the CSA, The EA at 400 mV proceeded about 800 times faster than the CSA when exposed to the same solution concentrations. The adsorption rates of both EA and CSA were found to be dependent on the molecular structures of OPEs. OPEs containing electron-donating groups assemble faster than those with electron-withdrawing groups. The amount of time that the thioacetyl-terminated OPE is in the presence of the base, for removal of the acetyl group to generate the thiolate, is called the deprotection time. Deprotection times play a critical role in achieving the maximum difference in adsorption rates between the EA and the CSA. The assembly must be initiated no later than 5 min after the basic deprotection is commenced so that the thiolate concentration remains low. The difference in the adsorption rates between EA and CSA might enable selective deposition of certain OPEs onto specific electrodes.     

The first mu3-oxalato-bridged copper complex with tridentate Schiff base ligand N-ethyl-N'-salicylidene-1,2-diaminoethane: synthesis,structure, and magnetic properties

The first mu(3)-oxalato-bridged copper(II) complex, [[Cu(3)(L)(3)(mu(3)-C(2)O(4))][Cu(L)(H(2)O)](ClO(4))(2)] x 0.5(H(2)O) x 0.5(CH(3)OH), where HL = N-ethyl-N'-salicylidene-1,2-diaminoethane, has been synthesized and characterized by variable-temperature magnetic susceptibility measurement. The complex exhibits ferromagnetic coupling between the oxalato-bridged copper atoms and antiferromagnetic coupling between the oxygen-bridged copper atoms.     

A facile electrochemical synthesis of caffeic acid derivatives in the presence of acetylacetone or methyl acetoacetate in aqueous medium

The anodic oxidation of caffeic acid in the presence of acetylacetone or methyl acetoacetate in aqueous solution has been studied by cyclic voltammetry and controlled-potential electrolysis techniques. The result showed that caffeic acid was oxidized to the corresponding o-benzoquinone, which underwent further Michael-addition with acetylacetone or methyl acetoacetate to produce caffeic acid derivative 3,4-dihydroxy-6-(1-acetylacetone)-yl cinnamic acid 4a or 3,4-dihydroxy-6-(1-acetyl-methylacetate)-yl cinnamic acid 4b.     

Synthesis and characterization of second-order nonlinear optical polyurethane with high thermal stability

A second-order nonlinear optical polyurethane was formed with an X-type multi-dimensional charge-transfer (CT) chromophore (DNPIPDHPI) and 3,3^′-dimethoxy-4,4^′-diphenyl diisocyanate. Simultaneous poling and polymerization and in situ second harmonic generation (SHG) measurement technique was carried on to evaluate the thermal stability of the poling induced orientation. The SHG signal of the poled polymer film was not decay below 150 °C and remains 90% of relative d₃₃ value at 200 °C, which is better than the results reported in literature. Comparison of thermal stability indicates that the X-type chromophores possess better property in controlling the decay of the SHG activity than classic chromophores.     

硫化物/Ru(II)络合物复合敏化TiO2纳米多孔膜

用光电化学方法研究了ＣｄＳ,ＰｄＳ和Ｒ１１Ｌ２（ＮＣＳ）２,（Ｌ＝２,２′－ｂｉｐｙｄｉｎｅ－４,４′－ｄｉｃａｒｂｏｘｙｌｉｃａｃｉｄ）复合敏化ＴｉＯ２纳米晶电极的光电化学行为,结果表明,采用复合敏化比用Ｒ１１（ＩＩ）络合物单独敏化ＴｉＯ２纳米晶电极效果好,大大提高了光电转换效率,主要原因是采用复合敏化,可防止ＴｉＯ２导带上由光注入产生的电子的反向转移,避免了电子的损失。     

Synthesis and characterization of new soluble poly（aryl ether nitrile）s containing phthalazinone moiety

A series of novel poly（aryl ether nitrile）s containing phthalazinone moiety were synthesized by the nucleophilic displacement reaction of bisphenol-like monomers （I） with 2,6-difluorobenzonitrile. The inherent viscosities ranged from 0.46 to 1.07 dL g^-1. The glass transition temperatures were in the range of 277-295℃, and the temperatures for 10% weight loss in nitrogen atmosphere were found between 495 and 527 ℃. The structures of these resultant polymers were confirmed by FT-IR and 1^H NMR. Moreover, the properties of poly（aryl ether nitrile）s including solubility and crystallinity were also studied.     

Graft copolymerization of methyl acrylate onto potato starch initiated by ceric ammonium nitrate

A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO₃) (1.08, 5.0 × 10^?3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: R_p = Kk_d [STOH] [Ce⁴⁺] + Kk_pk_d/k_t[STOH][M], where K, k_d, k_p, and k_t are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc.     

Synthesis and antiangiogenic activities of 5-amino-1,3-dihydro-1, 3-dioxo-2H-isoindole-2-propanoic acid derivatives

Based on the structure-activity relationships and antiangiogenic mechanism of RGD-containing peptides,a series of 5-amino- 1,3-dihydro-1,3-dioxo-2H-isoindole derivatives were synthesized.The structures were characterized by ~1H NMR,MS and elementary analysis.There ability to inhibit angiogenesis were evaluated by chick embryo chorioallantoic membrane assay at 10~(-5) mol/L.Compounds 7a and 7b displayed obvious antiangiogenic activity.     

Ni^2—交换蒙脱石中的镍物种及焙烧温度影响研究

对一组自制Ｎｉ＾２＋交换蒙脱石样品中镍物种的存在在形及焙烧温度影响进行了ＴＰＲ和ＸＲＤ考察结果表明，样品中镍负载量等于或小于Ｎｉ＾２＋的交换量时，镍主要以难还原听可交换性阳离子Ｎｉ（ＯＨ）＾ｑ＋ｘ和易还原的自由态镍Ｎｉ（ＯＨ）２或ＮｉＯ两种形式存在。