Effect of Water Vapor on Benzene Decomposition Using a Nonthermal-Discharge Plasma Reactor

The effect of water vapor on benzene decomposition in air was investigatedusing a nonthermal-discharge plasma reactor packed with ferroelectricmaterials. The conversion of benzene was found to decrease with an increaseof water concentration. On the other hand, the selectivity to CO₂ in thedecomposition products increased with an increase of water concentration. Acomparison between the benzene conversion to CO and CO₂ suggested that COformation was suppressed by water to a greater extent than was CO₂formation. N₂O formation also decreased with an increase of waterconcentration. These results suggest that the activity of oxygen speciesresponsible for the formation of CO and N₂O is reduced by water.     

Synthesis and anti-HIV activity of sulfated astragalus polysaccharide

Sulfated astragalus polysaccharide (sulfated astragalan, SA) was prepared by chemical modification of astragalus polysaccharide abstracted from an astragalus menbranceus used as a Mongolia herbal medicine. Anti-HIV activity of SA was assayed in vitro and the results indicated that the SA showing high anti-HIV activity and lower cytotoxity. Sulfation of astragalan was carried out by using sulfur trioxide-pyridine complex in a mixture of dimethylsulfoxide (DMSO) to give sulfated astragalan with degree of substitution (DS) of 1.14–1.20 and a number average molecular weight (M_n) of 1.27–1.46 × 10⁴. Copyright © 2003 John Wiley & Sons, Ltd.     

Raman spectroscopic study on NpO2 +–Ca2+ interaction in highly concentrated calcium chloride

Coordination circumstance of neptunyl ion in concentrated CaCl₂ solutions was analyzed by Raman spectrometry. Besides the symmetric stretch (ν₁) mode of NpO₂ ⁺ and NpO₂ ²⁺, the asymmetric stretch (ν₃) mode of NpO₂ ⁺ was found. The Raman intensity of the ν₃ mode increased with the concentration of CaCl₂ in the system. This would be attributable to the cation–cation interaction between Np(V) and Ca(II).     

Iridium-catalyzed [2+2+2] cycloaddition of α,ω-diynes with alkynyl ketones and alkynyl esters

We found that the combination of [Ir(cod)Cl]₂ and rac-BINAP served as an efficient catalyst for the [2+2+2] cycloaddition of 2,7-nonadiyne derivatives and related compounds with alkynyl ketones and alkynyl esters. The corresponding products were obtained in high yields under mild reaction conditions.     

One-pot photochemical synthesis of novel thienobis[1]benzothiophene with an angularly-fused structure that promotes unique intermolecular S⋯S contacts in the crystalline state

4,8-Di(thien-3-yl)thieno[2,3-g:5,4-g′]bis[1]benzothiophene (8a), a member of a new class of angularly-fused thienobis[1]benzothiophenes (TBBTs), was synthesized by using a one-pot photocyclization–dehydrogenation reaction of 2,5-bis[2,2-di(thien-3-yl)ethenyl]thiophene (7a). The results of absorption and emission spectroscopy, and cyclic voltammetry studies suggest that the effective conjugation length of 8a is shorter than that of 7a. X-ray crystallographic analysis revealed that the core TBBT framework of 8a is slightly twisted. In the crystalline state, molecules of 8a are arranged in stacked columns that interact with the adjacent stacked columns via S?S contacts. Moreover, a 1:1 charge-transfer complex between 8a and 7,7,8,8-tetracyanoquinodimethane (TCNQ) forms crystals that have an alternating stacked columnar structure with both 8a and TCNQ being aligned in individual ribbon-like motifs. The crystal properties of these substances suggest that the angularly-fused TBBT framework might be a useful platform for the construction of electrically interesting materials.     

(Dibenzoylmethanato)boron Difluoride Derivatives Containing Triphenylamine Moieties: A New Type of Electron‐Donor/π‐Acceptor System for Dye‐Sensitized Solar Cells

(Dibenzoylmethanato)boron difluoride derivatives containing triphenylamine moieties were synthesized as a new type of electron‐donor/π‐acceptor system. These new compounds exhibited long‐wavelength absorptions in the UV/Vis spectra, and reversible oxidation and reduction waves in cyclic voltammetry experiments. Their amphoteric redox properties are based on their resonance hybrid forms, in which a positive charge is delocalized on the triphenylamine moieties and a negative charge is localized on the boron atoms. Molecular orbital (MO) calculations indicate that their HOMO and LUMO energies vary with the number of phenylene rings connected to the difluoroboron‐chelating ring. This is useful for optimizing the HOMO and LUMO levels to an iodine redox (I^?/I₃^?) potential and a titanium dioxide conduction band, respectively. Dye‐sensitized solar cells fabricated by using these compounds as dye sensitizers exhibited solar‐to‐electric power conversion efficiencies of 2.7–4.4 % under AM 1.5 solar light.     

Combined use of two membrane-potential-sensitive dyes for determination of the Galvani potential difference across a biomimetic oil/water interface

The fluorescence behavior of anionic membrane-potential-sensitive dyes, bis-(1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC₄(3)) and bis-(1,3-diethylthiobarbituric acid)trimethine oxonol (DiSBAC₂(3)), at a biomimetic 1,2-dichloroethane (DCE)/water (W) interface was studied by the mean of potential-modulated fluorescence (PMF) spectroscopy. The respective dyes gave a well-defined PMF signal due to the adsorption/desorption at the DCE/W interface. It was also found that the potentials where the two dyes gave the PMF signals were different by about 100 mV. We then attempted a combined use of the two dyes for determination of the Galvani potential difference across the DCE/W interface. When 40 μM DiBAC₄(3) and 15 μM DiSBAC₂(3) were initially added to the W phase, distinctly different spectra were obtained for different interfacial potentials. The ratio of the PMF signal intensities at 530 and 575 nm (the fluorescence maximum wavelengths for the respective dyes) showed a clear dependence on the interfacial potential. These results suggested the potential utility of the combined use of two dyes for the determination of membrane potentials in vivo.

Raman Spectroscopic Study of Rare Earth Chlorides in Alkali Chloride Eutectic Melts

Raman spectra of rare earth (REE: rare earth elements) trichloride (REE = Y, La, Ce, Pr, Sm, Gd, Dy, or Yb) dissolved in alkali chloride eutectic melts (LiCl‐KCl, LiCl‐RbCl, and LiCl‐CsCl) were measured at 793 K. The spectra showed polarized peaks centered around 240–270 cm^–1, which were identified as the totally symmetric stretching vibration (ν₁) of the octahedral REECl₆^3–. The ν₁ frequency increased with the polarizing power of the trivalent REE ions. The change in the ν₁ frequency was found to be larger for lighter lanthanides. This was attributable to the distortion of the O_h symmetry of REECl₆^3–.     

Living Cationic Polymerization of α-Methylstyrene. 2. Synthesis of Block and Random Copolymers with 2-Chloroethyl Vinyl Ether and End-Functionauzed Polymers†

Abstract

Both AB and BA block copolymers of α-methylstyrene (αMeSt) and 2-chloroethyl vinyl ether (CEVE) were synthesized by the sequential living cationic polymerization initiated with the HCl-CEVE adduct (1a)/SnBr₄ system in CH₂Cl₂ at -78°C. αMeSt-CEVE (AB) block copolymers with narrow molecular weight distributions ([Mbar]_w/[Mbar]_n ～ 1.15) were obtained when αMeSt was polymerized first, followed by addition of CEVE to the resulting αMeSt living polymer solution. The reverse order of monomer addition, from CEVE to αMeSt, also led to a BA-type block copolymer. In the polymerization of a mixture of the two monomers, almost random copolymers were obtained. Living polymerizations of αMeSt were also induced with functional initiating systems, HCl-functionalized vinyl ether adducts (1b-1d)/SnBr₄, to give end-function-alized poly(αMeSt)s with a methacrylate, an acetate, or a phthalimide terminal.