Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 72 , Issue 12
Showing 1-28 articles out of 28 articles from the selected issue
  • Yoshiharu Mukouyama, Shuji Nakanishi, Yoshihiro Nakato
    1999 Volume 72 Issue 12 Pages 2573-2590
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Electrochemical reduction of H2O2 on Pt electrodes shows a variety of oscillations, depending on the electrode potential, electrode illumination, the atomic-level flatness of the electrode surface, and the presence or absence of metal atoms and halogen atoms adsorbed to submonolayer amounts on the electrode surface. This is a unique feature of this oscillating system, helpful for deeper understanding of oscillation phenomena. In this article, the fundamental behavior and mechanism of oscillations, named oscillations A and B, for polycrystalline Pt electrodes are first described. A mathematical simulation for oscillation A shows clearly the presence of a positive feedback mechanism and an important role of adsorbed hydrogen atoms, called upd-H. The behavior of oscillation A, especially the oscillation period, is changed by electrode illumination, application of weak external potential pulses, and coupling with other oscillation systems. The oscillation period is also altered by adsorption of foreign metal atoms such as Cu, Ag, Au, and Ru on Pt to sub-monolayer amounts. New-type oscillations called oscillations C and D appear when small amounts of halide ions are added to the solution. The appearance of oscillations C and D is explained by assuming a catalytic effect of adsorbed halogen atoms and an autocatalytic effect of adsorbed OH group on the H2O2 reduction. Another new-type oscillation is observed when an atomically-flat single-crystal Pt(111) electrode is used. These results clearly show an important role of atomic-level structures of the electrode surface in electrochemical oscillations.
  • Tamotsu Takahashi, Martin Kotora, Ryuichiro Hara, Zhenfeng Xi
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2591-2602
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    This account describes recent development in carbon–carbon bond cleavage reactions and selective transformation of 5-membered zirconacycles, including zirconacyclopentanes, zirconacyclopentenes, and zirconacyclopentadienes. These zirconacycles can be prepared by coupling of unsaturated compounds such as alkenes and/or alkynes, but the zirconacycles also undergo β,β′-C–C bond cleavage, which has been further applied to organic transformation reactions. Combination of the β,β′-C–C bond cleavage and the C–C bond formation on zirconocene provided a highly selective and novel transformation. Vinylzirconation of alkynes, regioselective allylzirconation of alkynes, and coupling of alkynes with nitriles or ketones were achieved by this method. Zirconacyclopentadienes prepared symmetrically or unsymmetrically were converted into naphthalene, diene, and benzene derivatives. Preparation of benzene derivatives from three different alkynes was performed by combination of C–C bond cleavage and C–C bond formation on zirconocene in one-pot in high yield with excellent selectivity.
  • Masaru Aoyagi, Kumar Biradha, Makoto Fujita
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2603-2606
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The formation of ···Pt(II)···Br–Pt(IV)··· mixed-valence complexes was utilized for the assembly of square compounds, [(en)M(4,4′-bpy)]4(NO3)8 (1·(NO3)8; a: M = Pt(II), b: M = Pd(II), 4,4′-bpy = 4,4′-bipyridine), into higher ordered infinite complexes. The reaction of 18+ with cationic Pt(IV) complex, [PtBr2(en)2]2+ (22+), afforded a 1 : 3 complex 1a·(2)314+. Crystallographic analysis of this complex showed that two moieties of 22+ bridged at the cis corner of 1a8+ making a stair-like infinite network, whereas another moiety of 22+ was accommodated in the cavity of 1a8+. On the other hand, complexation of 1b with anionic Pt(IV) complex, PtX62− (32−; a: X = Cl, b: X = Br), afforded a 1 : 4 complex 1·(3)4. UV-vis observations suggested the formation of a linear tube structure, in which each corner of 18+ is bridged by the linear X–Pt–X motif of 32−.
  • Yoshihiro Sasaki
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2607-2615
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The chaotic response of the minimal chemical oscillator stimulated by a sinusoidal perturbation was studied by a computer-simulation method. Chaotic phase diagrams were obtained and two types of chaos were estimated. One was neighbored by fundamental 1/2 and fundamental 1/3 entrainment regions, and was followed by a quasiperiodic region. It contained two chaotic modes (relatively large-amplitude mode and relatively small-amplitude one on the Poincaré section (cos ωpt = 1)) and coexisted with the fundamental 1/3 harmonic mode. Other chaotic regions appeared when fundamental 1/1 and fundamental 1/2 entrainment regions came into contact with each other, and these were not in contact with any quasiperiodic regions. In this case Hopf bifurcations from the fundamental 1/1 harmonic mode to the 1/n (n/n) (n: integer) harmonic modes occurred first, and were followed by chaotic modes between the harmonic modes and the 1/n ((n−1)/n) harmonic ones. The coexistence of the chaotic mode and the 1/3 harmonic mode and the existence of two chaotic modes were compared with the behaviors of a one-dimensional dynamical system having a piecewise linear map.
  • Toshihito Ohtake, Noriyuki Sonoyama, Tadayoshi Sakata
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2617-2623
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Electrochemical luminescence properties and mechanism of ZnGa2O4 and ZnGa2O4 : Mn (ZnGa2O4 doped with Mn) were studied. ZnGa2O4 disk showed an n-type semiconductor property after reduction in H2 atmosphere. Under cathodic polarization, the emission in a ZnGa2O4 electrode showed a broad peak at 485 nm in Na2S2O8 electrolyte solution. ZnGa2O4 : Mn exhibited a sharp emission peak at about 500 nm based on Mn2+, and a broad peak of ZnGa2O4 was also observed with increasing the cathodic bias. Under anodic polarization in Na2SO4 electrolyte, electrochemical luminescence was observed from the ZnGa2O4 electrode surface at +12.5 V (vs. Ag/AgCl) with two emission peaks at about 500 and 700 nm. The emission mechanism based on avalanche breakdown and impact excitation of emission centers by injected electrons is proposed. By adding K4[Fe(CN)6], KI, and KBr as reducing agents to the Na2SO4 electrolyte, the emission intensity was increased in the order KBr < KI < K4[Fe(CN)6]. Temperature dependence of the emission intensity suggests that electron transfer at the ZnGa2O4/electrolyte interface occurs equi-energetically from the occupied energy level of each reducing agent to the conduction band of ZnGa2O4.
  • Akio Kawai, Tetsuya Yamamoto, Tetsuo Okutsu, Kinichi Obi
    1999 Volume 72 Issue 12 Pages 2625-2632
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Chemically induced dynamic electron polarization (CIDEP) spectra of radicals produced in the photoreduction reaction of aromatic ketone/triethylamine systems were measured by time resolved ESR method. Anion radicals with net absorption (Abs) CIDEP were produced in ethanol with a base such as KOH, while ketyl type radicals with net emissive (Em) CIDEP have been formed in cyclohexane and benzene. Laser power dependence measurement indicates that net Em CIDEP of ketyl radicals is generated by a two-photon process while the production of ketyl radical itself is by one-photon process. Therefore, it was concluded that net Em CIDEP is generated through radical-triplet pair mechanism (RTPM) between the triplet state aromatic ketone and the produced ketyl radical. While RTPM is reasonably considered as an origin of net Em CIDEP for ketyl radicals, it is difficult to determine the CIDEP mechanism of the net Abs polarization of anion radicals in the present systems. Possible mechanisms were tentatively proposed for the present net Abs CIDEP generation.
  • Yo-ichi Ishikawa, Yoshitaka Matsumoto, Tomohiro Wakabayashi
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2633-2641
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    A multiphoton dissociation (MPD) of volatile metal carbonyl was applied for pulse production of neutral transition metal dimers in a gas-phase kinetic study. Its feasibility was discussed in the reaction systems of Mo2 with small molecules (O2, CO, NO, H2, SF6, NH3, and C2H4). Some potential problems, such as disturbances to the dimer production mechanism from the reactant addition and to neutral reaction kinetics from ionic species inevitably produced in the MPD of metal carbonyls, were experimentally examined. The transient concentration of Mo2 (X 1Σg+, ν = 0) produced by 266-nm MPD of Mo(CO)6 was measured by a laser-induced fluorescence (LIF) at 518.60 nm (A 1Σu+, ν″ = 0 ← X 1Σg+, ν′ = 0). The pseudo-first order decay rates of Mo2 were found to increase with increasing the concentration of some reactive species (O2, NO, and NH3). Our results obtained from time-resolved measurements were found to be almost consistent with the observations of Lian et al. (J. Phys. Chem., 98, 11637 (1994)) who prepared Mo2 by laser vaporization and measured its depletion in a fast-flow reactor.
  • Youzhu Yuan, Kiyotaka Asakura, Huilin Wan, Khirui Tsai, Yasuhiro Iwasa ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2643-2653
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The adsorption of CO and H2 on a SiO2-supported Au6Pt cluster [(AuPPh3)6Pt(PPh3)](NO3)2 (1) has been studied by means of FTIR, TPD, and EXAFS. CO adsorbed on 1/SiO2 to form a CO-adduct complex, which exhibited an IR band at ca. 1972 cm−1. The adsorbed CO was desorbed below 403 K, showing a peak maximum at 363 K in TPD. There was little change in the coordination number of Pt–Au in Pt L3-edge EXAFS upon CO adsorption, but the coordination number of Au–Au in Au L3-edge EXAFS slightly increased and the peak ascribed to Pt–(Au)–P in the Pt L3-edge EXAFS Fourier transform remarkably increased. The increase in the intensity of the Pt–(Au)–P peak was interpreted by the multiple scattering effect owing to the change of Pt–Au–P bond angle. The original EXAFS oscillations at both Pt and Au L3-edges were regenerated after evacuation of the CO-adsorbed sample for 2 h at 353 K, indicating the recovery of the original cluster structure. This is entirely different from the case of the cluster 1 in solution, where the cluster framework is fragmented by the CO adsorption-desorption process. The adsorption of H2 on 1/SiO2 was totally reversible at room temperature; it provided no contribution to the EXAFS oscillation.
  • Toshie Harazono, Ryuji Adachi, Naoto Kijima, Tokuko Watanabe
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2655-2664
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    89Y MAS (Magic angle spinning) NMR has been investigated to study the local environment of Y sites in a red phosphor, Eu doped-Y2O2S (Eu–Y2O2S), with varying the Eu content. Despite the presence of paramagnetic Eu3+ ions, high resolution spectra were acquired and a number of local environments were detected. The assignment of the resonances to different Y local environments was made on the basis of signal intensities, chemical shifts, and spin-lattice relaxation times (T1) in conjugation with the crystal structural data which were obtained by the Rietveld method. Besides the main peak in pure Y2O2S, four peaks caused by the –Eu species and ten peaks caused by the Eu––Eu species were distinguished in Eu–Y2O2S, where Y1 is the next nearest-neighbor Y site for the doped Eu atom, and –Eu and Eu––Eu are substituted by one and two Eu, respectively. Y atoms (Y2, Y3, ··· Yn), which are further from the second and more nearest-neighbors from Eu were observed at the same resonance position for all samples investigated with that of pure Y2O2S.
    The T1 values of the 89Y signal were reduced from 6.6 h for pure Y2O2S to 230 s (10 mol% Eu–Y2O2S) for Yn (n ≥ 2), to several tens of seconds for Y1–Eu and to several seconds for Eu–Y1–Eu in Eu–Y2O2S. The Eu content to Y in the region where Eu atoms are randomly isolated was estimated from the intensity ratio of the total intensities of the four Y1 peaks to the main peak. T1 reduction and a line-broadening due to paramagnetic Eu3+ ions are discussed in relation to the distribution of Eu ions.
  • Kunihito Hoki, Yukiyoshi Ohtsuki, Hirohiko Kono, Yuichi Fujimura, Shir ...
    1999 Volume 72 Issue 12 Pages 2665-2671
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    A quantum control of photodissocation of NaI to neutral atom fragments, NaI → NaI* → Na + I, was theoretically studied by using a locally optimized control method. The purpose of this control was to obtain as many neutral fragments as possible within one cycle of the nuclear vibration. The control was based on a pump-and-dump scheme. Weak and strong laser-field cases were used. The optimal dump pulses in both cases were shown to be of a linear time-dependent up-chirp type by analyzing their time- and frequency-resolved power spectra. This confirms the result predicted using a non-optimal control method in a previous paper (Chem. Phys. Lett., 231, 50 (1994)). The nuclear wavepacket propagations were also analyzed to see how photodissociation takes place when controlled pulses are used.
  • Masahiko Hashimoto, Takeshi Nakamura, Kazuhiko Tsukagoshi, Riichiro Na ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2673-2679
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    A flow-type chemiluminescence detection cell using optical fiber was designed for capillary electrophoresis. The capillary was set up straight to the optical fiber with a certain distance in a Teflon® tube. Hydrogen peroxide was delivered through a three-way joint by a syringe pump and mixed with analytes at the capillary outlet. Luminol chemiluminescence was adapted for use with this detection cell. Analytical conditions, such as hydrogen peroxide flow rate, distance between the capillary and the fiber, and the reagent concentrations, were examined in detail with the cell. The present flow-type system provided a CL signal with high sensitivity, resolution, and reproducibility. The detection limit (S/N = 3) for luminol was 7.6 × 10−9 M (28 amol; 3.7 nl injected) with theoretical plate numbers of 130000—160000 and a relative standard deviation of 3.3% for the peak height (n = 10). A mixture sample of glycine, glycylglycine, and glycylglycylglycine, which were labeled with isoluminol isothiocyanate (2,3-dihydro-6-isothiocyanato-1,4-phthalazinedione), was also subjected to the present system. They were sensitively detected and represented with high resolution.
  • Makoto Handa, Mayumi Watanabe, Daisuke Yoshioka, Seiichiro Kawabata, R ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2681-2686
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Adducts of rhodium(II) pivalate with pyrazine (pyz), 4,4′-bipyridine (4,4′-bpy), and 1,4-diazabicyclo[2.2.2]octane (dabco), triethylamine (tea), and pyridine (py) have been prepared. The adducts with pyz, 4,4′-bpy, and dabco are polymers formulated as [Rh2(O2CCMe3)4(L)]n, (L = pyz, 4,4′-bpy, and dabco). A polymer structure with an alternating arrangement of the rhodium(II) dimer and ligands was confirmed by an X-ray structure analysis of the 4,4′-bpy adduct. The Rh–Rh bond distance is 2.395(1) Å which is in the range of those reported for the adducts of rhodium(II) carboxylates with axial aromatic nitrogen-donor ligands. The structure of the adduct dimers, [Rh2(O2CCMe3)4(L)2] (L = tea and py), was also confirmed for a tea-coordinated complex, which has considerably long axial Rh–N (2.391(8) Å) and Rh–Rh (2.413(1) Å) bonds. The reflectance-spectral and thermogravimetric data of all the adducts were obtained to examine the axial interaction between the rhodium(II) dimer core and the ligands.
  • Ken Tsutsumi, Tomohiro Kawase, Kiyomi Kakiuchi, Sensuke Ogoshi, Yuji O ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2687-2692
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Some cationic η3-propargylpalladium complexes were prepared upon treatment of the corresponding η1-propargyl- or η1-allenylbis(triphenylphosphine)palladium(II) chloride with Ag[BF4] or Na[BPh4]. The effectiveness of the latter reagent suggests that a η1-propargyl- or η1-allenyl(chloro)palladium complex equilibrates with a cationic η3-propargylpalladium complex with the liberation of a Cl ligand. A qualitative comparison of trends in a series of analogous equilibrium systems suggests that the η3-coordination mode is favored to a greater extent when (i) propargyl ligands have an alkyl substituent at the propargylic position, (ii) phosphine ligands are bidentate, such as dppe, (iii) polar solvents are used, and (iv) the liberating ligand is a Cl one. A possible implication of η3-coordination of propargyl ligands in a catalytic cycle of Pd-catalyzed transformations of propargylic or allenylic substrates is presented.
  • Qiu-quan Wang, Ben-li Huang, Kin-ichi Tsunoda, Hideo Akaiwa
    1999 Volume 72 Issue 12 Pages 2693-2697
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The possible extracted species of rare earth elements (REE) in bis(1,1,3,3-tetramethylbutyl)phosphinic acid (Hmbp)/cyclohexane–HNO3 system was proposed by a log–log plot analysis and a saturated extraction method as being [M(mbp)3(Hmbp)3] (M = REE). It was also verified by IR, 1H NMR spectra and element analysis of lutetium–Hmbp extracted species. The effective mutual separation of REEs was achieved on the Hmbp modified C-18 column by a pH gradient elution. Moreover, the degree of the mutual separation of europium(III) from gadolinium(III) was remarkably improved by adding glycollic acid in the mobile phase. A fine concentrate of Sm2O3, Eu2O3, and Gd2O3 from a rare earths smeltery was analyzed by the present method with the spectrophotometric detection after postcolumn derivatization with Arsenazo III.
  • Haruo Naruke, Toshihiro Yamase
    1999 Volume 72 Issue 12 Pages 2699-2702
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The pyrolysis of a polyoxovanadate solid, (NH4)12[V18O42(H2O)]·nH2O (n ≈ 11), at 300 °C in an Ar+NH3 atmosphere gave a mixed-valence vanadium oxide, (NH4)xV3O7 (x ≈ 0.6), isostructural with Cs0.37V3O7. The crystal structure of (NH4)xV3O7 was refined by the Rietveld method (hexagonal, P63/m, a = 9.8436(6), c = 3.6165(1) Å, V = 303.47(3) Å3, Z = 2). (NH4)xV3O7 comprises edge- and corner-sharing VIV/VO5 square-pyramids with an approximate ratio of VIV : VV ≈ 0.49 : 0.51, to form a columnar cavity along the c-axis, in which ammonium N atoms are hydrogen-bonded to apical O atoms of the VIV/VO5 square-pyramids. A reflux of the (NH4)xV3O7 powder in a 0.6 M LiOH/2-methoxyethanol solution brought about Li-insertion into the columnar cavity without any structural change in the {V3O7} framework.
  • Meri Yamada, Shinya Suganuma, Ichiro Tanaka, Tatsuya Sekine
    1999 Volume 72 Issue 12 Pages 2703-2711
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The rate and equilibrium of solvent extraction of gallium(III) from aqueous perchlorate solutions into toluene with 2-thenoyltrifluoroacetone (Htta) was measured in the absence and presence of trioctylphosphine oxide (TOPO). A synergistic enhancement of the extraction was found when TOPO was added. When a correction was made for the association of Htta and TOPO in the organic phase which decreased their concentrations available for the extraction, the extracted adducts was found to be in the form of Ga(tta)3(TOPO)2. The rate of extraction was not high and it was dependent on the second order with respect to Htta and the inverse second order with respect to H+ in both the absence and the presence of TOPO. The rate was accelerated by addition of TOPO; the enhancement of the rate was proportional to the TOPO concentration.
  • Toshio Ishioka, Tatsuya Uchida, Norio Teramae
    1999 Volume 72 Issue 12 Pages 2713-2717
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    A measurement system for time-resolved surface-enhanced Raman spectroscopy with a submillisecond time resolution was developed using a step-scan near-infrared Fourier-transform spectrometer and was applied to analyze a redox reaction of 9,10-phenanthrenequinone (PQ) adsorbed on a polycrystalline gold electrode. In the time-resolved surface-enhanced Raman spectra, both quinone and hydroquinone forms of PQ were recognized, but the intermediate species, semiquinone radicals, were not. It was suggested that the lifetime of the intermedeate species was shorter than 0.5 ms, which was the time resolution of the developed system.
  • Hideya Miwa, Nagao Kobayashi, Kazue Ban, Kazuchika Ohta
    1999 Volume 72 Issue 12 Pages 2719-2728
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Triple-decker sandwich complexes, which consist of two cerium ions and three strip-like diarylporphyrins, have been synthesized and their spectroscopic and electrochemical properties and mesomorphism are reported and compared with those of the corresponding double deckers and the parent monomers. The Soret band of the triple-deckers lies at longer and shorter wavelengths than those of the double-deckers and monomers, respectively, while a sequence of small absorptions is observed in the Q band region. These are interpreted on the basis of knowledge of triple-deckers made from tetraphenylporphyrin and octaethylporphyrin. Magnetic circular dichroism (MCD) spectroscopy suggests that the Soret bands of the triple-deckers are a superimposition of at least two transitions to orbitally degenerate states. In the MCD spectra, Faraday A-terms are observed corresponding to each absorption band, suggesting that these triple-deckers take D4h or more plausibly D4d structures. Triple-deckers containing dialkoxyphenyl groups at the 5,15-positions of their parent porphyrin show a mesophase possessing both lamellar and columnar structures at lower temperatures and a columnar mesophase at higher temperatures, which differ in stacking distances. On the other hand, those containing tetraalkoxylated terphenyl groups at the 5,15-positions of their parent porphyrin show only a columnar mesophase with a single stacking distance. These differences in the mesomorphism are explained by differences of the magnitude of the steric hindrance of the side chains for rotation along the axis connecting the center of the three porphyrins.
  • Satoshi Kawaguchi, Takeshi Kajikawa, Mariko Kaneko, Takahiro Koshimizu ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2729-2736
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    In the presence of a catalytic amount of lanthanide cations (Ln3+), the amide of 6-benzoylamino-6′-L-phenylalanylamino-2,2′-bipyridine (1a) was efficiently cleaved at 30 °C to give L-phenylalanine ester in methanol almost quantitatively. The reaction proceeded in the manner of the Michaelis–Menten type via the 1 : 1 1a–Ln3+ complex ([1a]/[Ln3+] molar ratio = 1); the half-life time of the scissile amide bond of the complex was as short as 2 min for the 1a–Dy3+ system. The reactions were highly specific to the structure of the substrates, requiring 2,2′-bipyridine having two acylamino side chains at the 6,6′-positions and an amino group at the α-position of the scissile carbonyl. The formation and structures of the less-reactive 6,6′-bis(benzoylamino)-2,2′-bipyridine (1d) with lanthanide cations were studied spectrophotometrically. They formed 1 : 1 complexes, and the formation constants (Ka) were on the order of 103—105 mol−1 dm3 in methanol at 30 °C. Coordination of the bipyridine nitrogens and the carbonyl oxygens was indicated in chloroform. However, coordination of the carbonyl oxygens was not observed in methanol. Detailed structures of the complexes are discussed in relation to their reactivity.
  • Hiroaki Ohtake, Yasushi Imada, Shun-Ichi Murahashi
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2737-2754
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Tungstate-catalyzed oxidation of N-alkyl-α-amino acids with 30% H2O2 solution under phase-transfer conditions gives nitrones regioselectively in good yields. Using this method, stereodivergent synthesis of (R)- and (S)-4-(t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-17a and (S)-17a) was achieved. In addition, (R)- and (S)-3-(t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-45 and (S)-45) were prepared by catalytic oxidation of the corresponding chiral pyrrolidines in a regioselective manner. These chiral cyclic nitrones, 17 and 45 are versatile intermediates for the synthesis of optically active nitrogen heterocycles, since stereoselective additions of carbon nucleophiles to these chiral nitrones can be readily performed. Typically, ZnI2-mediated addition of ketene t-butyldimethylsilyl methyl acetal (29a) to (R)-17a gave the cis-adduct, methyl (2R,4R)-[1,4-bis(t-butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (cis-30). In contrast, the addition of lithium acetylides 34 to the nitrone (R)-17a gave the trans-adducts, (2S,4R)-2-(1-alkynyl)-4-(t-butyldimethylsilyloxy)-1-hydroxypyrrolidines trans-35. These adducts are useful intermediates for syntheses of the nitrogen heterocycles (3R,5R)-1-aza-3-hydroxybicyclo[3.3.0]octane (37) and (6R,8R)-1-aza-8-hydroxybicyclo[4.3.0]nonane (38), respectively. The ZnI2-mediated addition of ketene silyl acetal 29a to the nitrone (R)-45 gave methyl (2S,3R)-[1,3-bis(t-butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (trans-50a), which was used for asymmetric synthesis of the Geissman–Waiss lactone ((−)-49).
  • Yutaka Takabayashi, Takeshi Yusa, Masahiro Minabe, Takao Kimura, Motoh ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2755-2760
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The liquid crystallinity of the title compounds was studied in order to design a stable liquid crystal used at low temperature. The Schiff base derived from 1- or 3-fluoreneamine scarcely shows liquid crystallinity. The propionyl group is effective for lowering the melting point of the mesophase compared to the acetyl group in a series of the title substances. The liquid crystallinity of the title compounds was compared with that of biphenyl homologues. A mesophase of the title substances was observed over a wider range of temperatures than in the case of biphenyl derivatives in a series of propionyl groups.
  • Tadashi Okuyama, Hiroshi Yamataka, Masahito Ochiai
    1999 Volume 72 Issue 12 Pages 2761-2769
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Solvolysis of (E)- and (Z)-2-methyl-5-phenyl-1-pentenyl(phenyl)iodonium tetrafluoroborate (1·BF4) was carried out in various alcohols, acetic acid, and aqueous solutions at 60 °C. Products (after acid hydrolysis) include iodobenzene and 2-methyl-5-phenylpentanal as well as rearranged ones: 6-phenyl-2-hexanone, 6-phenyl-3-hexanone, 6-phenyl-2-hexyne, 6-phenyl-1,2-hexadiene, and 6-phenyl-2,3-hexadiene. The products of α-elimination, including 1-methyl-3-phenyl-1-cyclopentene, were also obtained in methanol and ethanol. Solvolysis of the E isomer (E)-1 is faster than that of (Z)-1 in every solvent examined. The percentage of rearrangement is higher with (E)-1 than with (Z)-1, and the main rearranged products are those of migration of the alkyl group trans to the iodonio group, but migration of the cis alkyl group is also involved. Theoretical calculations suggest that interconversion between the secondary vinylic cations by 1,2-hydride shift is rapid. These results show that a major heterolysis reaction occurs with β-alkyl participation to directly give a secondary vinylic cation, but stereochemistry of the unrearranged substitution products suggests that formation of the primary vinylic cation is also involved in less nucleophilic solvents like acetic acid and 2,2,2-trifluoroethanol.
  • Tsuyoshi Kaneko, Tatsuya Tokue, Kanji Kubo, Tadamitsu Sakurai
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2771-2780
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The benzophenone-sensitized photolysis of the title hydroxylamine (1) in hexadecyltrimethylammonium chloride (HTAC) micelles was found to give benzoyloxy(2,3)- and phenyl(4,5)-migrated products, along with fragmentation products, 1-naphthanilide (6) and benzoic acid (7), which were obtained exclusively from the sensitized reaction in organic media. An analysis of the effects of added benzyl alcohol on the quantum yields for the reaction in HTAC micelles showed that the benzoyloxy-migrated products are derived from the amidyl-benzoyloxyl radical pair (that is present at the micellar surface), whereas the amidyl-phenyl radical pair (that is penetrated deeply into the micellar interior) is responsible for appearance of the phenyl-rearranged products. This effect of benzyl alcohol also confirmed that the hydrogen abstraction of the amidyl and benzoyloxyl radicals takes place in competition with the spin inversion of these triplet radicals. These interpretations were substantiated by the finding that the critical micelle concentration for HTAC is reduced in the presence of benzyl alcohol, but that the alcohol exerts only its very small effect on the aggregation number. On the other hand, the use of hexadecyltrimethylammonium bromide (HTAB) micelles instead of HTAC resulted in 2 and 3 in negligible quantum yields with increased quantum yields for the formation of 47. This intriguing result was explained in terms of (1) much less efffective hydrogen-bonding solvation of the assumed hot triplet radical pair in the more hydrophobic HTAB micellar surface as well as (2) heavy-atom effects on the intersystem crossing from the singlet amidyl-benzoyloxyl radical pair to the triplet one. Based on the quantum yields for the triplet-sensitized photolysis of 1 in HTAC–HTAB mixed micelles, it was demonstrated that the hydrogen-bonding solvation described above plays a major role in suppressing the benzoyloxy photorearrangement reaction in the HTAB micelle cage.
  • Shigehisa Akine, Kei Goto, Takayuki Kawashima, Renji Okazaki
    1999 Volume 72 Issue 12 Pages 2781-2783
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    Two conformationally frozen isomers (cone and 1,2,3-alternate) of a water-soluble calix[6]arene were synthesized and found to show the critical micelle concentrations quite different from each other, which was explained in terms of their monomer structures with different arrangements of the charged groups.
  • Kazuo Ogawa, Ikuo Hirai, Choichiro Shimasaki, Toshiaki Yoshimura, Shin ...
    1999 Volume 72 Issue 12 Pages 2785-2790
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    To develop a simple method to determine the degree of substitution (dS) for starch ester, we prepared starch acetate with various dS values (0—3) and examined the mode of starch-iodine complex formation for the starch acetate by monitoring the ultraviolet-visible (UV-vis) spectra and their Fourier-transform infrared (FT-IR) spectral changes. The effect of acetylation on the formation of the starch-iodine complex was investigated by monitoring the decrease in absorbance at 680 nm (blue value). The blue value decreased by increasing the standard dS value determined by NMR for starch acetate, but two different correlations between the blue values and the dS values were observed for the low- and highly-substituted starch acetate. The FT-IR spectra for starch acetate particles were measured using a diffuse reflection method. The peak areas and absorbances of the bands assigned to the acetyl group showed a poor correlation with standard dS values from the NMR. On the other hand, the FT-IR peaks assigned to sodium acetate produced by saponification of the starch acetate could be detected using the ATR (attenuated total reflection) method; they showed a good correlation with the standard dS values from the NMR. From these results, it was concluded that the ATR method should be available for the dS determination of starch acetate.
  • Hiroyuki Nishide, Yoko Suzuki, Eishun Tsuchida
    1999 Volume 72 Issue 12 Pages 2791-2794
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    5,10,15,20-Tetrakis(α-o-pivalamidophenyl)porphyrinatocobalt(II) (CoP) complexed with N-tritylimidazole in the solid state quickly and reversibly absorbed oxygen from air (14 cm3 O2/g), which was ascribed to a Co/dioxygen 1/1 adduct formation. The adduct formation was an exothermic reaction, and the absorbed oxygen was released above 65 °C. A disk (e.g., diameter 2 cm × 2 mm) was prepared with powders of the oxygen-absorbing, but electrically insulating, CoP complex and of electrically conductive carbon. The application of 1.5 V to the disk induced a temperature elevation in the disk, which momentarily released the absorbed oxygen. The oxygen-releasing and -absorbing cycle could be repeated more than 100 times, with a 5-min switching on-off interval under ambient conditions.
  • Masami Yanagida, Atsushi Takahara, Tisato Kajiyama
    1999 Volume 72 Issue 12 Pages 2795-2802
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    A Langmuir–Blodgett (LB) film for a optical planar waveguide with a low optical propagation loss could be constructed from highly organized fatty acid monolayers prepared by a cooling multi-step creep method. The cooling multi-step creep method is the novel preparation technique to form a defect-diminished monolayer on the water surfaces on the basis of both the structural relaxation induced by area-creep and the control of thermal molecular motions in the monolayer. The fatty acid monolayer prepared by the cooling multi-step creep method was morphologically homogeneous and mechanically stable, even at a high surface pressure where the monolayer prepared by a conventional continuous compression method easily collapsed. The crystallographical and structural regularities of the monolayer and the LB film prepared by the cooling multi-step creep method were remarkably improved, compared with those of the monolayer and the LB film prepared by the conventional continuous compression method. The LB film waveguides prepared by the cooling multi-step creep method were morphologically homogeneous and structurally regular and could propagate incident light with a low optical propagation loss.
  • Shigeru Kunugi, Hiroyuki Yamamoto, Miki Makino, Tomoko Tada, Yukiko Ue ...
    Type: Accounts
    Subject area: AI
    1999 Volume 72 Issue 12 Pages 2803-2806
    Published: 1999
    Released: June 01, 2005
    JOURNALS RESTRICTED ACCESS
    The pressure and temperature dependence of the hydrolytic rate of carboxypeptidase Y was studied in the range of 5—40 °C and 0.1—400 MPa. The iso-activity contours have more or less positive slopes. The pressure apparently disactivates the enzyme at a constant temperature, and the apparent activation volume (ΔV) became smaller with increasing temperature; ΔVapp = − 46 ml mol−1 at 10 °C and −11 ml mol−1 at 40 °C. At a constant pressure, the activity increased with increasing temperature, and the evaluated activation enthalpy (ΔH) increased with an increase in pressure from 13 kcal mol−1 at 0.1 MPa to 25 kcal mol−1 at 400 MPa.
    The intrinsic fluorescence spectrum changed with temperature and pressure and the highest intensity was recorded at ambient pressure and the lowest temperature, while the intensity decreased with increasing temperature or pressure. The intensity also decreased with decreasing temperature under elevated pressure, while the peak wavelength shifted to the red side according to the increase in pressure and temperature.
    The disactivation of the catalysis and the decrease in the fluorescence peak intensity at a higher pressure and lower temperature were considered to be the so-called pressure-assisted cold-denaturation of the enzyme protein. Pressure can be a perturbation agent to “increase” the transition temperature above 0 °C.
feedback
Top