Contraction of supramolecular double-threaded dimer formed by alpha-cyclodextrin with a long alkyl chain

A double-threaded dimer bearing a long substituent part and a large stopper group has been prepared and showed a conformational change with increased solvent polarity. [structure: see text]     

Reverse photochromic behavior of an iron-magnesium complex

We have obtained a novel heterobimetallic iron-magnesium complex, (THF)4Mg(mu-Br)2FeBr2 (THF = tetrahydrofuran), which showed reverse photochromism in THF. The response exhibited in this system is associated with d-orbital splitting of the Fe atom and a change in the molecular aggregation state (dimerization).     

Preparation and properties of rotaxanes formed by dimethyl-beta-cyclodextrin and oligo(thiophene)s with beta-cyclodextrin stoppers

Novel cyclodextrin rotaxanes with oligothiophene as an axis molecule have been prepared by the Suzuki coupling reaction of 6-O-(4-iodophenyl)-beta-CD (6-I-Ph-beta-CD) with di(1,3,2-dioxaborolan-2-yl)-oligothiophene (oligothiophene diboric ethylene glycol esters) in aqueous solutions of dimethyl-beta-cyclodextrin (DM-beta-CD). These reactions gave [2]rotaxanes and [3]rotaxanes, which were isolated by reversed phase chromatography. The fluorescence intensities of rotaxanes are higher than those of dumbbell-shaped molecules (without DM-beta-CD) in aqueous solutions. The inclusion ratio and chain length of rotaxanes have been found to relate to the emission properties and emission intensities of oligothiophene. In aqueous solutions, fluorescence quantum yields of rotaxanes are higher than those of dumbbell-shaped molecules. The increase in the fluorescence efficiency of rotaxane is caused by suppression of intermolecular interactions, indicating the effect of insulated oligothiophene with DM-beta-CD. beta-CD at the both ends of rotaxanes functions not only as bulky stoppers but also as the recognition site for guest molecules, as verified by fluorescence quenching experiments.     

Variation of atmospheric tritium concentrations in three different chemical forms in Fukuoka, Japan

Atmospheric tritium concentrations of tritiated water vapor (HTO), tritiated hydrogen (HT) and tritiated hydrocarbons (primarily tritiated methane, CH₃T) have been measured in Fukuoka prefecture, Japan from 1984 to the present to establish a general database on the behavior of atmospheric tritium. HTO concentrations expressed in Bq/l-H₂O vary within a range of 1.19 to 2.45, giving an overall average value of 1.86±0.077. HTO concentrations expressed in-mBq/m³-air vary within a range of 7.8 to 46.1 and have a strong correlation with the atmospheric humidity, being high in the summer and low in winter. In the case of HT and CH₃T, no seasonal variations were observed with average monthly values of 23.1 to 61.0 mBq/m³-air and 8.3 to 23.9 mBq/m³-air, respectively. The present HTO concentrations are already close to the tritium level before nuclear testings. However, the present HT and CH₃T concentrations are still higher by a factor of about 140 and 30, respectively, than those before the testings. Specific activities are estimated to be 14.6–16.7 TU for HTO, 5.5·10⁵–1.0·10⁶ TU for HT and 3.2·10⁴–4·10⁴ TU for CH₃T. The apparent difference in the specific activities suggests a very slow transformation of these species in the atmosphere or a continuous supply of HT and CH₃T with high specific activity. Residence time for atmospheric HT was found to be 6.5 years over the period 1988–92 and 10 years for 1988–95. These times are longer than 4.8 years given by Mason and Östlund in the 1970s, and thus indicate a supply to the atmosphere of HT from various tritium sources.     

Development of Submillimeter Wave Catheter Transmitting a Gyrotron Output for Irradiation on Living Bodies

The development of a millimeter and submillimeter wave catheter for irradiation on living bodies using a gyrotron as the radiation power source is described. The GYROTRON FU-IV, optimized for such applications was used in the development. It was operated in both CW and pulsed regime at TE₀₃ and TE₃₂ modes with frequencies 302 GHz and 238 GHz respectively. Irradiation tests were made on thermal papers, beefs and liver of living rats.     

Kinetic studies of specific solvent effect on the thermal isomerization of palladium dithizonate in toluene‐alcohol mixtures

The kinetics of the thermal isomerization of palladium dithizonate (Pd(HD_Z)₂) in the binary mixture of toluene and alcohols has been studied. In the solvent effects on the Pd(HD_Z)₂ isomerization rates, we found that the maximum lies in the range x = 0.02 ∼ 0.2 (x represents the mole fraction of alcohols). The experimental kinetic data for the specific solvent effect with maximum can be reproduced well by taking into account hydrogen bonding and coordination of alcohols with Pd(HD_Z)₂. The rate constants for the thermal isomerization of Pd(HD_Z)₂ involving hydrogen bonding and the coordinate interaction with 1‐butanol are evaluated. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 542–547, 2000     

Cover Picture

The cover picture shows how protein matrices can regulate the spatial arrangement and orientation of a heme-based donor (Zn-heme: ZnPP)-sensitizer (Ru²⁺(bpy)₃)-acceptor (cyclic viologen: BXV⁴⁺) triad. A U-shape conformation of the triad without protein matrix changes into a triangle arrangement by incorporation into apocytochrome b₅₆₂ (Cyt-b₅₆₂), or into a further extended conformation by apomyoglobin (Mb) matrix. The electron transfer pathways and the lifetimes of the photoinduced charge-separated states were remarkably affected by the protein wrapping effect.     

Synthesis of nickel nanoparticles supported on hollow samaria-doped ceria particles via the solution-spray plasma technique: Anode catalysts for SOFCs

Aiming at SOFC anode applications, we have synthesized nanometer-sized nickel catalysts supported on hollow spherical particles of samaria-doped ceria (Ni/SDC) by spraying a mixed solution of nickel, samarium, and cerium nitrates into an atmospheric pressure plasma. The as-prepared particles consisted of SDC (average diameter d_SDC = ca. 0.8 µm) and uniformly dispersed nanometer-sized NiO particles. When reduced in H₂ at 800 °C or 1000 °C, Ni nanoparticles (average diameter d_Ni = 34 nm) were found to be embedded uniformly into the SDC surface.     

Chemical and Genetic Study of Ligularia cyathiceps in Yunnan Province of China

Root chemicals and evolutionarily neutral DNA regions in L. cyathiceps samples collected in the Zhongdian (Shangrila) County of Yunnan, P. R. China, were examined. Twenty compounds were isolated, including three new ones, 1β,10β‐epoxy‐6β‐(propionyloxy)furanoeremophilan‐9‐one ( 6 ), 1β,10β‐epoxy‐8α‐ethoxyeremophila‐6,11‐diene ( 14 ), and 11αH‐6β‐isobutyryloxy‐1β,10β,7β,8β‐diepoxyeremophilan‐12,8α‐olide ( 15 ). The chemical diversity was found to be limited, with cacalol ( 1 ) and 6‐(acyloxy)furanoeremophilan‐9‐ones ( 4 and/or 5 ) being major components in all the samples. The nuclear ribosomal RNA gene was also found to harbor little variation, although two distinct sequence types were found for the plastid atpB‐rbcL intergenic region.