Optical rotation inversion of porphyrin-DNA complexes

A porphyrin-DNA complex in which helical porphyrin assemblies were stacked as π-stacked aggregates on a DNA scaffold was found. The complex indicates the inversions of optical rotation by only the control of ionic equilibrium without any structural changes of DNA scaffold.     

Cross-metathesis of vinyl aromatic heterocycles with 1-octene in the presence of a Schrock catalyst

Metathesis of 2-vinyl aromatic heterocycles such as furan, thiophene, pyrrole and pyridine in the presence of a molybdenum-based Schrock catalyst has been investigated from a synthetic point of view. The self-metathesis of 2-vinyl aromatic heterocycles was not successful. However, in cross-metathesis of thiophene, furan and styrene with 1-octene, the cross-metathesis product, heterodimer, was readily obtained selectively, together with only small amounts of the two corresponding self-metathesis products. The origin of the surprisingly high selectivity of heterodimer formation was elucidated through metallacyclobutane intermediate mechanism, observations of carbenes by in situ ¹H NMR, and reaction products.     

Silicon hydrides and nickel complexes : III. Hydrosilylation of olefins with dichloro[1,2-bis-(dimethylphosphino)-1,2-dicarba-closo-dodecaborane]-nickel(II) as catalyst

The hydrosilylation of olefins catalyzed by nickel(II) chloride complexed with 1,2-bis(dimethylphosphino)-1,2-dicarba-closo-dodecaborane produces terminal and internal adducts in comparable amounts. This unusual feature of the reaction is explained in terms of the electron-accepting nature of the carboranyl group.     

Syntheses and electrical conductivity of polyamides containing tetrathiafulvalene moieties in the main chain

Novel polyamides that contain tetrathiafulvalene (TTF) moieties were synthesized by direct polycondensation of Δ^2,2′ -bi-1,3-dithiole-4,4′(5′)-dicarboxylic acid with aromatic diamines in the presence of triphenylphosphine, hexachloroethane, and pyridine. Complexes of these polyamides with bromine were TTF cation radical () salts which resulted from the charge transfer of TTF moieties to bromine. The electrical conductivity of undoped polyamides increased with a decrease in diamine length. By doping the bromine the conductivity of the polyamides was enhanced by 3–5 orders of magnitude and reached 10^?5–;10^?9S cm^?1. Maximum conductivity was observed at the doping ratio of [Br]/[repeat unit] < 1. The electrical conduction in the bromine complexes may be attributed to the hopping of odd electrons of between TTF moieties.     

Indium triflate-catalyzed vinylation of beta-ketoesters with acetylene gas

[reaction: see text]. An In(OTf)(3)-catalyzed addition of a beta-ketoester to acetylene in the presence of molecular sieves produces a alpha-vinylated ketoester in good to excellent yield. The vinylation reaction proceeds without any loss of elements in starting molecules under solvent-free conditions and allows the use of welding-grade acetylene, providing a practical method for synthetic utilization of acetylene gas.     

Electrochemical control of CO/NO ligand exchange in a triruthenium cluster monolayer assembled on a gold electrode surface

A highly selective ligand exchange reaction is realized in the self-assembled monolayer (SAM) of a triruthenium cluster on a gold electrode surface under precise electrochemical potential control. CO as well as NO molecules, which are known to play key roles in many chemical, biological, and environmental systems, can be efficiently introduced into the SAM by electrochemically tuning the electronic state of the Ru site. These unique surface reactions are more convenient and efficient than conventional ligand exchange reactions in solution and could be used for the elucidation of the electron-transfer mechanism in a biological system as well as in the development of molecular sensors and devices.     

Effect of polycondensation methods on molecular weight distribution of nylon 610

Polycondensation methods greatly influence the molecular weight distribution of poly(hexamethylene sebacamide) (nylon 610) as determined by gel permeation chromatography (GPC). The ratio of weight average molecular weight to number average molecular weight (M_w/M_n) was used as a measure for estimating the molecular weight distribution. The M_w/M_n ratios of nylon 610 obtained from melt, solid phase, and high temperature polycondensation methods were 2 to 3.5, which were expected values for the most probable distribution. However, those for polymers obtained from the direct polycondensation in the presence of triphenylphosphine, interfacial polycondensation and low temperature polycondensation using an acid chloride varied over a wide range from 3.5 to 8.5. The effect of the kind of organic solvents in the interfacial method on the M_w/M_n ratios was especially large, and the molecular weight distribution could be controlled to some extent by selecting an appropriate solvent.     

Recent progress of high-power negative ion beam development for fusion plasma heating

A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D⁻ ion beam. In the preliminary experiment using one ion source, a D⁻ ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D⁻ beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/I_D⁻ < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H⁻ ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator.     

Pre-irradiation induced grafting of styrene into crosslinked and non-crosslinked polytetrafluoroethylene films for polymer electrolyte fuel cell applications. II: Characterization of the styrene grafted films

Crosslinked and non-crosslinked polytetrafluoroethylene films (RX-PTFE and V-PTFE films, respectively) were irradiated by γ-ray and then grafted with styrene in liquid phase. Microscope FT-IR spectroscopy, TGA, solid state ¹³C CP/MAS and high resolution HS/MAS NMR spectroscopy, wide-angle X-ray diffraction (WAXD) study were used to get the structural information of the styrene grafted RX-PTFE and V-PTFE films. From microscope FT-IR spectra of the grafted RX-PTFE films, the “grafting front mechanism” was proved. TGA analysis showed that the grafted films have a small degradation step and two main degradation steps. In the ¹³C CP/MAS NMR spectra of the non-grafted films, there are no signal due to the absence of the hydrogen atom. While in the spectra of the grafted films, there are signals attributed to the polystyrene grafts. In the ¹³C HS/MAS NMR spectra of the grafted films, the relative intensity of the peaks attributed to the polystyrene grafts increased while the relative intensity of the peak attributed to PTFE matrix decreased with the increase in the DOG. From WAXD patterns, the intensity of the crystalline peak decrease with the increase in the DOG. The grafted films were sulfonated by chlorosulfonic acid and the results of highest IEC value exceeded 3.0. Those results will be reported in the near future.     

Correlation between the structure of water in the vicinity of carboxybetaine polymers and their blood-compatibility

The structure and hydrogen bonding of water in the vicinity of carboxybetaine homopolymer (poly[1-carboxy-N,N-dimethyl-N-(2'-methacryloyloxyethyl)methanaminium inner salt] (PolyCMB), and a random copolymer of CMB and n-butyl methacrylate, Poly(CMB-r-BMA), with various molecular weights were analyzed in their aqueous solutions and thin film with contours of O-H stretching of Raman and attenuated total reflection infrared (ATR-IR) spectra, respectively. The relative intensity of the collective band (C value) corresponding to a long-range coupling of O-H stretchings of the Raman spectra for aqueous solution of Poly(CMB-r-BMA) was very close to that for pure water, which is in contrast with the smaller C value in aqueous solution of ordinary polyelectrolytes. The number of hydrogen bonds collapsed by the presence of one monomer residue (N(corr) value) of PolyCMB and Poly(CMB-r-BMA) (CMB, 45 mol %) (M(w), 1.14 x 10(4) and 1.78 x 10(4), respectively) could be calculated from the C value. The N(corr) values were much smaller than those for ordinary polyelectrolytes and close to those for nonionic water-soluble polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone). Furthermore, a water-insoluble Poly(CMB-r-BMA) with a large BMA content (M(w) = 347 kD, CMB 27 mol %) could be cast as a thin film (thickness, ca. 10 microm) on a ZnSe crystal for the ATR-IR analyses. At an early stage of sorption of water into the Poly(CMB-r-BMA) film, the O-H stretching band of IR spectra for the water incorporated in the film was similar to that for free water, which is in contrast with the drastic change in the O-H stretching band of water incorporated in polymer films such as poly(methyl methacrylate) (PMMA) and poly(n-butyl methacrylate) (PBMA). The theoretical vibrational frequency for water molecules hydrating a betaine molecule calculated by using a density functional method supported the experimental results. The adhesion of human platelets to Poly(CMB-r-BMA) films was much less than that to PMMA and PBMA. With an increase in the content of CMB residue, the number of platelets adhered to the Poly(CMB-r-BMA) film drastically decreased and then gradually increased, probably due to the increase in the roughness of the film surface. These results suggest that the carboxybetaine monomer residues with a zwitterionic structure do not significantly disturb the hydrogen bonding between water molecules in both aqueous solution and thin film systems, resulting in the excellent blood-compatibility of the carboxybetaine polymers.