Polybenzimidazoles containing anthracene photodimer

Polybenzimidazoles that contained anthracene photodimer were prepared. The molecular weights of the polymers prepared by the photopolymerization of bis-anthrylbenzimidazoles were limited by the precipitation of the resulting polymers from the reaction organic solvents. Higher molecular weight polymers were obtained by the photopolymerization of bis-anthryl-Schiff's bases, followed by the oxidation of the resulting polymers. These polymers were soluble in acidic solvents such as formic and sulfuric acids but were insoluble in organic solvents.     

Reactivities of Stable Rotamers: XLIV. Ring-Opening Reactions of 1-(9-Fluorenyl)-2-(2-methyl-2-oxiranyl)naphthalene Rotamers With Acids and the Structure of Oxiranes

X-ray crystallography of the ap-form of the 1-(9-fluorenyl)-2-(2-methyl-2-oxiranyl)naphthalene has revealed that the carbon atom of the oxirane which is connected to the naphthyl group in this compound is almost planar. The specific structural features of the epoxy ring in this compound are caused by sterical effects and by the presence of a -system in the immediate vicinity of the oxirane ring. Certain differences have been found also in reactivity of rotational isomers of 2-X-substituted 1-[1-(9-fluorenyl)-2-naphthyl]ethyl cations (X = O, S, Se). At X = O arose more deprotonation product from the -position of the oxygen than in reactions of sulfur and selenium-containing analogs. Reactions of epoxides with zinc chloride almost exclusively gave the corresponding aldehydes.     

Platinum-catalyzed intramolecular vinylchalcogenation of alkynes with beta-phenylchalcogeno conjugated amides

Platinum-catalyzed intramolecular vinylthiolation and -selenation of internal alkynes with vinylchalcogenides 1 having a carbamoyl group on cis-beta-position of vinyl moiety was developed. The conjugated six-membered lactam framework 2 was constructed in high yields. Density functional theory calculations for alkyne insertion processes suggest seven-membered platinacycle 3 is a kinetically favored intermediate of this catalytic system.     

Palladium-catalyzed selenoacylation of allenes leading to the regioselective formation of functionalized allyl selenides

Palladium-catalyzed regio- and stereoselective selenoacylation of allenes with selenol esters proceeded to produce functionalized allyl selenides with the acyl moiety at the inner carbon and the SePh group at the terminal carbon in high yields. A mechanism accounting for the observed regio- and stereoselectivities is proposed based on the results of DFT calculations.     

Photoinduced electron transfer catalysis of titania particles modified with a Ru(2,2′-bipyridyl)3 2+-grafted polymer by visible light

 The preparation and photocatalysis of colloidal titania modified with Ru(2,2′-bipyridyl)₃ ²⁺-grafted polyacrylate were investigated. Visible light irradiation of the Ru(2,2′-bipyridyl)₃ ²⁺-tethered titania in pH 7.0 buffer solution gave electron transfer to methyl viologen to form the cation radical via electron migration from the Ru(II) complex to the titania surface. Received: 16 September 1999 Accepted: 24 November 1999     

Microdosimetry of in-flight pi-beams (author's transl)

Microdosimetry of in-flight pi-beams was performed at the T1 channel of National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. Distributions of lineal energy (y) in-flight pi-beams having six momentum values from 120 MeV/c to 1000 MeV/c were measured with an LET counter which simulates 2 micron sphere of soft tissue filled with the methane base tissue equivalent gas. Frequency spectra were obtained in the range of 1.6 less than y less than 430 keV/micron. Fractional dose y . d(y), cumulative dose D(y), and mean lineal energy were calculated from these spectra; then momentum dependences were investigated. These absolute values have little physical application because of the lack of data for y less than 1.6 keV/micron. However, the general trends of y distribution in momentum dependence were found, qualitatively. As the momentum becomes smaller, the rate of high y component in the dose increased.