Photoinduced reversible pH change in aqueous solution of azoaromatic poly(carboxylic acid)

To regulate the pH value of an aqueous solution containing polyelectrolyte by photoirradiation, an azoaromatic poly(carboxylic acid), acrylic acid(AA)-p-phenylazoacrylanilide (PAAn) copolymer was synthesized and the photoresponse of the polymer solution was investigated. AA-PAAn copolymer, which takes a compact form in the ordinary state owing to the presence of azoaromatic side chains, is transformed into an extended form when azoaromatic moieties are isomerized by photoirradiation. Thus, the pH value of the solution can be reversible regulated by irradiation and interruption of light through a change in polymer conformation. The range of the pH change was about 0.15. These phenomena can be explained on the basis of polarity change induced by the photoisomerization of azoaromatic side chains.     

Monotone explicit iterations of the finite element approximations for the nonlinear boundary value problem

Summary In this paper, we consider monotone explicit iterations of the finite element schemes for the nonlinear equations associated with the boundary value problem u=bu ², based on piecewise linear polynomials and the lumping operator. These iterations construct the monotonically decreasing and increasing sequences, and convergence proofs are given. Finally, we present some numerical examples verifying the effectiveness of the theory.     

Regioselective hydroxylation of the xylyl linker in a diiron(III) complex having a carboxylate-rich ligand with H2O2

Reaction of a diiron(III) complex having a xylta4- ligand (N,N,N',N'-m-xylylenediamine tetraacetate) with H2O2 resulted in regioselective hydroxylation of the m-xylyl linker. The reaction mimics the self-hydroxylation of a phenylalanine side chain found for ribonucleotide reductase (R2-W48F/D84E).     

等离子体聚合膜的电学性质研究：Ⅰ.TCNQ聚合膜的结构和电学性质

本文采用内部电极、电容耦合式钟罩型射频等离子体聚合装置,首次进行了四氰代对二次甲基苯醌(TCNQ)的等离子体聚合,得到了电导率为10~(-8)～10~(-6)Scm~(-1)的聚合物半导体薄膜。由这些聚合物薄膜制备的Al/聚合膜/ITO(铟锡氧化物透明电极)夹层元件显示出整流特性和光生伏打效应。这种聚合物薄膜还具有光电导性质。红外光谱(IR)、紫外光谱(UV)的研究结果表明,优良的半导体特性归因于聚合膜中存在有较大范围的π电子共轭结构。     

Mechanism of the axial ligand substitution reactions on the head-to-tail alpha-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex with olefins

Reactions of the head-to-tail alpha-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex having equivalent two platinum atoms, Pt(N(3)O), with p-styrenesulfonate and 4-penten-1-ol were studied kinetically. Under the pseudo first-order reaction conditions in which the concentration of the Pt(III) dinuclear complex is much smaller than that of olefin, a consecutive basically four-step reaction was observed for the reaction with p-styrenesulfonate, but for the reaction with 4-penten-1-ol, the reaction was three step. The olefin pi-coordinates to one of the two equivalent Pt atoms in the first step (step 1), followed by the second pi-coordination of another olefin molecule to the other Pt atom (step 2). In the next step (step 3), the nucleophilic attack of water to the first pi-coordinated olefin initiates its pi-sigma bond conversion on the Pt atom, and the second pi-bonding olefin molecule on the other Pt atom is released. Finally, dissociation of the alkyl group on the Pt(N(3)O) and reduction of the Pt(III) dinuclear complex to the Pt(II) dinuclear complex occur (step 4). The first water substitution with olefin (step 1) consists of two paths, the reaction of the diaqua dimer complex (path a) and the reaction of the aquahydroxo dimer complex (path b), whereas the second substitution (step 2) proceeds through three reaction paths: the normal path of the direct substitution of H(2)O (path c), the path of the coordinated OH(-) substitution (path d), and the path via the coordinatively unsaturated five-coordinate intermediate (path e). The reaction with p-styrenesulfonate proceeds through paths c, d, and e, whereas the reaction with 4-penten-1-ol proceeds through paths c and d. The third step (step 3) for the reaction with p-styrenesulfonate involves the coordinatively unsaturated intermediate, but that for the 4-pentene reaction does not. The reactivities of the HH dimer and HT dimer with olefins are compared and discussed.     

A sequential highly stereoselective hydroboration and Suzuki-Miyaura cross-coupling reaction of fluoroalkylated internal acetylenes: a practical one-pot synthesis of fluoroalkylated trisubstituted alkenes

The one-pot synthesis of trisubstituted alkenes starting from fluoroalkylated internal alkynes was investigated. Hydroboration of the alkynes proceeded in a highly regio- and stereoselective manner to give the corresponding vinylboranes in excellent yields. Without isolation, treatment of the vinylboranes with various aryl halides under the Suzuki-Miyaura cross-coupling conditions gave the fluoroalkylated trisubstituted alkenes in high yields with complete retention of the olefinic geometry.     

Cell separation in microcanal coated with electrically charged phospholipid polymers

To separate the cell population in whole blood using microcanal, the surface was covered with a polyion complex (PIC) composed of electrically charged phospholipid polymers. The phospholipids polymers were prepared by the polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butyl methacrylate with 3-(methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit. The PIC was formed at the solid-liquid interface, that is, first, the cationic polymer was coated on the substrate and an aqueous solution containing the anionic polymer with different concentrations was applied to the polymer-coated substrate. The formation of the PIC was followed using a quartz crystal microbalance (QCM), and the PIC surfaces were analyzed by both zeta-potential measurement and X-ray photoelectron spectroscopic measurement. The surface electrical potential on the PIC was controllable from +40 to -40 mV by increasing the amount of the adsorbed anionic polymer. The PIC surface was prepared in microcanal. The surface electrical potential was sequentially changed. When the whole blood was introduced into the microcanal, the cells adhered on the positively charged surface, but could not adhere to the negatively charged surface. Even when the cells adhere to the surface, the morphology of cells was maintained. This is due to MPC units at the surface, which show a good biocompatibility. These results indicated that the change in the surface electrical potential will be a useful method to separate the cells from whole blood.     

A first regioselective synthesis of 3-fluoroalkylated benzofurans via palladium-catalyzed annulation of fluorine-containing internal alkynes with variously substituted 2-iodophenol

The palladium-catalyzed annulation reaction of a variety of fluorine-containing internal alkynes with 2-iodophenol derivatives was investigated. The use of P(t-Bu)₃ as a ligand on palladium was found to be crucial in this annulation reaction, resulting in the exclusive formation of 3-fluoroalkylated benzofurans in high yields. ¹⁹F NMR analysis of the reaction mixture revealed that the addition of phenol to the fluoroalkylated alkynes was followed by intramolecular Heck reaction, giving to the corresponding 3-fluoroalkylated benzofurans.     

The fluorine-containing pi-allylmetal complex. The transition metal-catalyzed allylic substitution reaction of fluorinated allyl mesylates with various carbon nucleophiles

The allylic substitution reaction of [small alpha]-fluoroalkylated allyl mesylates with various carbon nucleophiles in the presence of transition metal catalyst (Pd and Mo) proceeded with high regioselectivity to give the corresponding [gamma]-fluoroalkylated products in excellent yields.     

Reaction of triphenylsulfonium salt with organolithium reagents

The reaction of triphenylsufonium trifluoromethanesulfonate with various nucleophilic, organolithium reagents gave ligand coupling products and the corresponding diaryl or di-heteroaryl sulfides. Moreover, ligand exchange reaction did not give any noticeable product in each reaction. Therefore, it was found that only the ligand coupling reaction proceeds in this reaction system.Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1053–1058,. August, 1995. Original article submitted August 19, 1995.