Anthracene derivatives and the corresponding dimers with TEMPO radicals

Anthracene derivatives with several TEMPO radicals (2-4, 10) were prepared, and each photodimerization reaction was investigated. Although the photodimerization was unsuccessful in obtaining the dimers of anthracenes 2 and 3, which could be alternatively prepared in a stepwise manner, the photodimers of anthracenes 4 and 10 were available by the direct photoreaction. The dissociation reaction of the dimers proceeded well by heating them in solution to give the corresponding monomers in each case, and thus the reversible system could be constructed in the latter two systems. While no large difference was observed in their magnetic behaviors between the monomer/dimer pair of 4 and 8, an intriguing difference was found in the magnetic behaviors for the pair of 10 and 11 from ferromagnetic interactions in 10 to the variable magnetic interactions in 11 depending on the solvent molecules incorporated in the crystals.     

Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses

By moving silica glass in a preprogrammed structure, we directly produced three-dimensional holes with femtosecond laser pulses in single step. When distilled water was introduced into a hole drilled from the rear surface of the glass, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. Straight holes of 4-mu;m diameter were more than 200 microm deep. Three-dimensional channels can be micromachined inside transparent materials by use of this method, as we have demonstrated by drilling a square-wave-shaped hole inside silica glass.     

Liquid–Liquid Equilibria of Oxygenate Fuel Additives with Water at 25°C: Ternary and Quaternary Aqueous Systems of Methyl tert-Butyl Ether and tert-Amyl Methyl Ether with Methanol or Ethanol

Experimental tie-line data have been determined for the ternary system water + methyl tert-butyl ether + tert-amyl methyl ether and the quaternary systems water + methanol + methyl tert-butyl ether + tert-amyl methyl ether, and water + ethanol + methyl tert-butyl ether + tert-amyl methyl ether at 25°C and ambient pressure. The experimental results have been satisfactorily correlated using the modified UNIQUAC and extended UNIQUAC models with ternary and quaternary, in addition to binary parameters.     

High-pressure NMR study of cis-1,n-disubstituted[n]paracyclophanes. Effect of increased pressure on the hindered internal rotation.

The effect of hydrostatic pressure on the rate of internal rotation of title compounds has been examined by the DNMR method. Quartz pressure-resisting NMR cells were used to realize the high-pressure experiments up to 390 (line shape measurements) and 450 MPa (chemical shift measurements). Application of hydrostatic pressure was found to accelerate the rotation of the benzene ring, while pressure-induced low-frequency chemical shifts of bridge methylene protons indicated that there is a considerable shrinkage of the methylene bridge structure upon pressurization.     

Catalytic effects of dioxygen on intramolecular electron transfer in radical ion pairs of zinc porphyrin-linked fullerenes.

Dioxygen accelerates back electron transfer (BET) processes between a fullerene radical anion (C60) and a radical cation of zinc porphyrin (ZnP) in photolytically generated ZnP.+-C60.- and ZnP.+-H2P-C60.- radical ion pairs. The rate constant of BET increases linearly with increasing oxygen concentration without, however, forming reactive oxygen species, such as singlet oxygen or superoxide anion. When ferrocene (Fc) is used as a terminal electron donor moiety instead of ZnP (i.e., Fc-ZnP-C60), no catalytic effects of dioxygen were, however, observed for the BET in Fc+-ZnP-C60.-, that is, from C60.- to the ferricenium ion. In the case of ZnP-containing C60 systems, the partial coordination of O2 to ZnP.+ facilitates an intermolecular electron transfer (ET) from C60.- to O2. This rate-determining ET step is followed by a rapid intramolecular ET from O2.- to ZnP.+ in the corresponding O2.--ZnP.+ complex and hereby regenerating O2. In summary, O2 acts as a novel catalyst in accelerating the BET of the C60.--ZnP.+ radical ion pairs.     

Diastereoselective synthesis of (2R,4R)-2-aryl-4-hydroxypyrrolidine: preparation of the side chain of novel carbapenem.

Improved synthesis of the trans-3,5-disubstituted pyrrolidin-3-ylthio side-chain of the novel carbapenem 1 was achieved via stereoselective reduction of the 1-aryl-1-butanone derivative 5 and successive intramolecular cyclization of the resulting chiral alcohol 6. The 1-aryl-1-butanone derivative 5 was obtained by a coupling reaction of protected 4-hydroxy-2-pyrrolidone with aryl-Grignard reagent.     

Lithium insertion to ReO3-type metastable phase in the Nb2O5–WO3 system

Lithium insertion to distorted ReO₃-type metastable solid solution Nb_xW_1−xO_3−x/2 (0≤x<0.25) has been studied by chemical and electrochemical methods. In the course of lithium insertion into tetragonal compounds, transition to a cubic phase was found to occur in the region where values of y (in Li_yNb_xW_1−xO_3−x/2) fall between 0.2 and 0.3, and the phase transition was found to depend on the conditions of the reaction. Changes in OCV and lattice parameters in tetragonal region (y<0.2) were discussed from the viewpoint of the ordering of lithium ions. Also, the component diffusion coefficient of lithium in tetragonal compounds Li_0.1Nb_xW_1−xO_3−x/2 (0≤x≤0.23) was found to increase with niobium content when x≤0.10, and to saturate at 4×10⁻⁹ cm²/s.     

Nanoscopic measurements of the electrostriction responses in P(VDF/TrFE) ultra-thin-film copolymer using atomic force microscopy

Atomic force microscopy (AFM) has been used as a new method to perform nanoscale measurements of the electrostriction coefficients in the lamellae structure of the ferroelectric P(VDF/TrFE) 73/27 copolymers. The result found shows that the electrostriction coefficient inside (in the middle of) the lamella crystals is 6×10^-19 (m²V^-2), which is three times larger than that at the boundary, 2×10^-19 (m²V^-2). To explain the dependence of the electrostriction coefficients with those two regions, some suggestions are proposed. By heat treatment at 140 °C during 2 h, the sample changed its morphology as well as its crystallinity; the amorphous phase is much reduced and the degree of the crystallinity inside the lamellae is higher than that in the border. Also, it is suggested that in the lamellae’s boundary the macromolecular chains come to an end, or one monolayer folds over the other layer. In this case, the electrostriction was suppressed due to the loss of surface energy in the lamellae’s boundary. The achievements will supply a guideline to develop new and better devices for electromechanical and actuator applications. Received: 23 June 2000 / Accepted: 23 August 2000 / Published online: 5 October 2000