Stereocontrolled synthesis and optical properties of all-cis poly(phenylene vinylenes) (PPVs): a method for direct patterning of PPVs

Geometrically pure, all-cis poly(phenylene vinylenes) (PPVs) are synthesized by Suzuki-Miyaura-type polycondensation of 2,5-dioctyloxy-1,4-benzenediboronic acid with (Z,Z)-bis(2-bromoethenyl)benzenes, which are prepared by ruthenium-catalyzed (Z)-selective double hydrosilylation of diethynylbenzenes, followed by bromodesilylation of the resulting (Z,Z)-bis(2-silylethenyl)benzenes with N-bromosuccinimide. The all-cis PPVs thus obtained undergo one-way photoisomerization to the corresponding trans-PPVs both in solution and in the solid. This phenomenon is applied to direct microscale patterning of PPVs onto a quartz substrate.     

Shortcut synthesis of beta-cyclomannin from beta-cyclodextrin

Beta-cyclomannin, a cyclic oligosaccharide consisting of seven alpha-D-mannosides connected together by the (1-->4) glycoside linkage, has been efficiently synthesized by the OsO4 oxidation of heptakis(2,3-didehydroxy)-beta-cyclodextrin which was prepared from beta-cyclodextrin by a five-step transformation. The novel cyclooligosaccharide not only showed water solubility high enough to meet the requirement for drug formulation but also demonstrated strong binding ability toward guest molecules. [reaction: see text]     

Formation processes of particulates in helium-diluted silane RFplasmas

Particulate formation processes in SiH₄ RF plasmas are studied using two laser light scattering (LLS) methods and a newly developed Langmuir probe method together with a discharge-modulation method. From the experiments, the following results are obtained: particulates tend to appear around the plasma/sheath boundary of the RF electrode in their early growing phase and, in the subsequent rapid growing phase, grow there at a rate of a few tens nm/s high compared to the film deposition rate; after the rapid growing phase, the growth rate decreases considerably; size and density of particulates amount to 60~180 nm and 10⁸~10⁸ cm^-3; spatial distributions of subnanometer-size particles detected by the probe method are similar to those of particulates of above a few tens nm in size observed by the LLS methods. These results suggest that short lifetime neutral radicals primarily contribute to particulate nucleation and subsequent early growth; the particulate growth rate during the rapid growing phase can be explained by taking into account the contribution of positive-ion and/or neutral radical fluxes to the particulate surface. Furthermore, the considerable decrease in the growth rate after the rapid growing phase may suggest that the positive ions mainly contribute to the rapid growth     

Enhanced absorption and fluorescence efficiency of silylethynyl-functionalized oligothiophenes and thieno[3,2-b]thiopahene

Silylethynyl-substituted oligothiophenes and thieno[3,2-b]thiophene were synthesized by the Sonogashira coupling reaction. The absorption and fluorescence maxima of these compounds shifted to longer wavelength, and they exhibited higher absorption coefficients and quantum yields than the corresponding unsubstituted molecules and tert-butylethynyl derivatives. From the DFT calculation, the energy band gap between HOMO and LUMO decreases by the introduction of a silicon atom. Thus, silyl groups can play important role in enhancing the quantum efficiency and decreasing the band-gap of chromophores. Hence, Silylethynyl group can serve as a highly efficient auxiliary for use in optical devices.     

Plasma interactions with aminoacid (l-alanine) as a basis of fundamental processes in plasma medicine

Plasma interactions with l-alaine have been studied as a basis of fundamental processes in plasma medicine. The plasma interactions with l-alaine have been examined for investigations of molecular degradations induced by direct exposures with Ar plasma and exposures with UV–VUV photons emitted from the Ar plasma via chemical bonding states analyses using X-ray photoelectron spectroscopy (XPS). The direct Ar-plasma exposure resulted in significant degradations of COOH group and CNH₂ group. Separate experiments via irradiation with photons in UV and VUV regions from the Ar plasma showed that the molecular degradation via irradiation with photons in VUV region was much more significant than via irradiation with photons in UV region. These experiments have indicated that the causality of the molecular degradation of the l-alanine during the Ar plasma exposure is considered to be significant in the following order; ions > VUV photons > UV photons ～ meta-stable radicals. Furthermore, the exposure with Ar–O₂ mixture plasma resulted in insignificant change in the XPS C1s spectra for variation of the exposure time ranging from 30 s to 300 s, indicating that the surface etching process is much more considerable than the chemical degradation process.     

Hybrids of Copolymers of Fluorene and C60‐Carrying‐Carbazole with Semiconducting Single‐Walled Carbon Nanotubes

Three different copolymers of C₆₀‐carrying‐carbazole and fluorene units with different copolymer composition ratios were designed and synthesized. On the basis of photoluminescence, atomic force microscopy, and Vis‐NIR and Raman spectroscopic analysis, we found that these copolymers solubilize only semiconducting single‐walled carbon nanotubes (sem‐SWNTs) to form copolymer/sem‐SWNT hybrids, in which energy transfer from the copolymer/C₆₀ moieties to the SWNTs was revealed. By comparing two possible hybrid structures with molecular‐mechanics simulations, the greatest stabilization was found when the C₆₀ moieties lay on the sem‐SWNT surfaces.     

Anharmonic temperature factors of atoms with 4mm and 42m site symmetries

The anharmonic temperature factors of atoms with 4mm and $\text{4}$2m site symmetries were formulated following the method of Matsubara, and the formulate were incorporated into a conventional full-matrix least-squares program for structure refinement. In the present treatment, anharmonic terms up to the third order in effective one-particle potentials were taken into account and Boltzmann statistics was employed.