The photochemical reactions of 5H-benzo[a]phenothiazin-5-one with alkylthiols and thiophenol

6-Alkylthio- and 6-phenylthio-5H-benzo[a]phenothiazin-5-ones were prepared by the photochemical reaction of 5H-benzo[a]phenothiazin-5-one with alkylthiols and thiophenol. The structures of newly prepared compounds were determined by elemental analysis, spectroscopic methods (ir, nmr and ms) and comparison with a sample prepared by an alternate route.     

Direct evidence for root growth of vertically aligned single-walled carbon nanotubes by microwave plasma chemical vapor deposition

The root growth mode of extremely dense and vertically aligned single-walled carbon nanotubes (SWNTs) synthesized by microwave plasma chemical vapor deposition was clarified by a new method, marker growth, which does not require transmission electron microscopy. SWNT layers were grown intermittently on a substrate, and a line between the layers was used as a marker to identify the growth mode. Micro-Raman spectroscopy revealed that the SWNT layers have the same diameter distribution.     

Molecular design, chemical synthesis and biological evaluation of quinoxaline-carbohydrate hybrids as novel and selective photo-induced DNA cleaving and cytotoxic agents

The quinoxaline moiety in antitumor quinoxaline antibiotics cleaved double stranded DNA at the 5′ side guanine of the 5′-GG-3′ site upon irradiation with UV light with a long wavelength and without any additive. The quinoxaline-carbohydrate hybrid system was very effective for the DNA cleavage. Furthermore, the quinoxaline-carbohydrate hybrids exhibited strong and selective cytotoxicity against cancer cells with photoirradiation.     

The Effect of Side Chain Association on Thermal and Viscoelastic Properties: Cellulose acetate based polycaprolactones

Cellulose acetate-based polycaprolactones (CAPCL's) were synthesized by the polymerization of -caprolactone which was initiated by non-substituted OH group in cellulose acetate. The CL/OH (mol mol^–1) ratios of the CAPCL's were changed from 2 to 20. Thermal and viscoelastic properties of the CAPCL sheets were studied by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Glass transition, cold crystallization and melting were determined by DSC. Dynamic modules (E'), dynamic loss modules (E') and tan were measured in a temperature range from –150 to 50°C by DMA. Apparent activation energy of a dispersion was calculated from the frequency dependency of E' peak temperature. It was found that the main chain motion of both CA and PCL is observed in a CL/OH ratio from 0 to 10 mol mol^–1. However, when CL/OH ratio exceeds 10 mol mol^–1, the crystalline region which is rearranged by the PCL chain association is observed and only the main chain motion of PCL can be detected.This revised version was published online in November 2005 with corrections to the Cover Date.     

INHIBITORY EFFECT OF CONTINUOUS FAR-RED PREIRRADIATION ON CHLOROPHYLL ACCUMULATION OF PHARBITIS NIL COTYLEDONS

Abstract The effect of continuous far-red (FR) preirradiation on the accumulation of chlorophyll (Chi) during a white light (WL; 500 lx) period was examined using Pharbitis nil cotyledons. The saturation level of accumulated Chi attained after prolonged exposure to WL was always lowered by continuous FR irradiation preceding the WL. The rate of Chi accumulation during the rapid increase phase (operationally defined as the amount of Chi accumulated during a 24-h WL period) was enhanced by preirradiation with up to 36 h of FR. However, when the FR preirradiation lasted longer, the rate was reduced below the dark control level. Even FR preirradiation of up to 36 h fully reduced the rate of Chi accumulation under WL when 36 h or longer darkness was spaced between the FR and the WL period.     

Evaluation of the efficiency of the photocatalytic one-electron oxidation reaction of aromatic compounds adsorbed on a TiO2 surface

The TiO2 photocatalytic one-electron oxidation mechanism of aromatic sulfides with a methylene bridging group (-(CH2)n-, n=0-4) between the 4-(methylthio)phenyl chromophore and the carboxylate binding group on the surface of a TiO2 powder slurried in acetonitrile (MeCN) has been investigated by time-resolved diffuse reflectance (TDR) spectroscopy. The electronic coupling element (H(DA)) between the hole donor and acceptor, which was estimated from the spectroscopic characteristics of the charge transfer (CT) complexes of the substrates (S) and the TiO2 surface, exhibited an exponential decline with the increasing of the methylene number of S. The determined decay factor (beta) of 9 nm(-1) also supports the fact that the 4-(methylthio)phenyl chromophore is separated from the TiO2 surface. The efficiency of the one-electron oxidation of S adsorbed on the TiO2 surface, which was determined from the relationship between the amount of adsorbates and the concentration of the generated radical cations, significantly depended on the H(DA) value, but not on the oxidation potential of S determined in homogeneous solution.     

An expeditious synthesis of bistratamide H using a new fluorous protecting group

A total synthesis of bistratamide H has been achieved using a new ‘highly’ fluorous amino protecting group, tris(perfluorodecyl)silylethoxylcarbonyl (^FTeoc) group. The synthetic intermediates were easily isolated by liquid-liquid extraction with fluorous solvent. The fluorous protecting group was demonstrated to be recycled.     

Thermally induced structural transformation in a hydrogen-bonded supramolecular single-crystal

The thermally induced structural transformation of a hydrogen-bonded crystal formed from an amphoteric molecule of 6-[2-methoxy-4-(pyridylazo)phenoxy]hexanoic acid MeO was studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction measurement (XRD). Crystal form of the hydrogen-bonded crystal was measured by single crystal four circle diffractometer (Mo-K_α radiation). As a result, the crystal of MeO was stabilized by many C–H⋅⋅⋅O hydrogen bonds, and the C–H⋅⋅⋅O hydrogen bonds were broken by thermal energy reversibly. After transformation the supramolecular architecture was composed of supramolecular polymer including free-rotation pentamethylene main chains.