Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 75 , Issue 11
Showing 1-30 articles out of 30 articles from the selected issue
  • Yo Fujimura, Hiroshi Tsurumaki, Okitsugu Kajimoto
    Type: Accounts
    Subject area: TP
    2002 Volume 75 Issue 11 Pages 2309-2336
    Published: 2002
    Released: November 15, 2002
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    Studies on stereodynamics of the gas-phase elementary reactions of atomic oxygen, O(1D) and O(3P), with simple molecules are reviewed. The angular correlations among the relative velocity vectors of reactants (k) and products (k′), and the product rotational angular momentum vector (j′) have been investigated via Doppler-resolved polarization spectroscopy. In the O(1D) reactions with hydrocarbons and water, OH products are scattered into wide angular range and rotate mainly in the kk′ scattering plane. These angular distributions suggest the formation of an H–O–X (X = C or O) bond in reactive intermediates. By contrast, the NO products of the O(1D) reaction with N2O have isotropic angular distribution of j′, which indicates the participation of the out-of-plane motion in addition to the in-plane motions within the complex. These trends of O(1D) reactions are consistent with the feature of product-state distribution of the individual reactions. Similar analyses for the reactions of O(3P) atom with hydrocarbons have revealed that these reactions are not always dominated by the simple rebound abstraction mechanism based on the triatomic picture, which has long been assumed. As a background of the titled study, this account reviews the progress in the studies on gas-phase chemical reaction dynamics and presents the theory and techniques to investigate the stereodynamics of bimolecular reactions.
  • Minoru Ueda, Noboru Takada, Shosuke Yamamura
    Type: Accounts
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2337-2347
    Published: 2002
    Released: November 15, 2002
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    Most leguminous plants close their leaves in the evening, as if to sleep, and open them early in the morning. This circadian rhythm is known to be controlled by the biological clock of such plants. Extensive studies on other nyctinastic plants led to the isolation of a variety of leaf-closing and leaf-opening substances. And we found that the circadian rhythmic leaf-movement of these plants is controlled by a biological clock that regulates the balance of concentration between leaf-opening and -closing substances.
  • Kohji Yoshinaga
    Type: Accounts
    Subject area: AM
    2002 Volume 75 Issue 11 Pages 2349-2358
    Published: 2002
    Released: November 15, 2002
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    The polymer modifications of inorganic colloidal particles, mainly silica, and the stabilization and functionalization were described. The polymer grafting procedures on colloidal silica via covalent bond bindings in order to stabilize and functionalize were presented along with the modification of inorganic particle powder. In the modifications, the reaction of the surface hydroxy groups with polymeric trialkoxysilane was effective for grafting the polymer in terms of controlling the attachment and of successive introduction of functional groups. Especially, the grafting of poly(maleic anhydride-co-styrene) (P(MA-ST)) onto colloidal silica by the reaction with P(MA-ST)-trimethoxysilane gave stable and dispersible composite particles (P(MA-ST)/SiO2) in organic solvent. The introduction of secondary polymer to P(MA-ST)/SiO2 successfully controlled the dispersion in organic solvent and ζ-potential in aqueous or highly polar solvents. The modification of colloidal titania with Ru(II)-(2,2′-bipyridyl) complex-tethered polymer gave a photo-active catalyst that exhibited photoinduced electron transfer to a donor by visible light irradiation. Moreover, colloidal crystallization was observed in the suspension of monodisperse, polymer-modified silica in organic solvent, which was a good polar solvent for grafted polymer. The colloidal crystallization of the modified silica took place through close-packing under the electrostatic repulsion among the particles, as well as the crystallization of unmodified silica in aqueous solution.
  • Katsuyuki Ogura, Rui Zhao, Hiroyuki Yanai, Kazuhiro Maeda, Ryo Tozawa, ...
    Type: Headline
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2359-2370
    Published: 2002
    Released: November 15, 2002
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    The derivatives of 1-phenyl-2-(2-thienyl)-5-[5-(tricyanoethenyl)-2-thienyl]pyrrole (1a) formed crystals with gold-like or bronze-like metallic luster. When a small substituent is located at the para position of the 1-phenyl group, gold-like lustrous crystals were formed. In contrast, the derivatives of 1 having a longer alkyl chain at the para position of the 1-phenyl group gave bronze-like crystals. The gold-like lustrous crystals have a sheet structure. In the sheet, the molecules of 1 are close to each other via the intermolecular interaction of cyano nitrogen with the hydrogen of the nearest thiophene or pyrrole ring, which enables the side-by-side interaction of the cyano group with the nearest thiophene and pyrrole rings. The bronze-like crystals have a lamella structure of the long alkyl chains that is sandwiched by two π-electron walls. In the wall, the 2-(2-thienyl)-5-[5-(tricyanoethenyl)-2-thienyl]pyrrole moieties are arranged in a ribbon structure to interact to each other. The relationship of the arrangement of the 2-(2-thienyl)-5-[5-(tricyanoethenyl)-2-thienyl]pyrrole moieties with the metallic color of the crystals is discussed.
  • Sanyo Hamai
    Type: Article
    Subject area: TP
    2002 Volume 75 Issue 11 Pages 2371-2377
    Published: 2002
    Released: November 15, 2002
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    In pH 10.1 buffers, the interactions of tetrakis(4-carboxyphenyl)porphyrin (TCPP) with γ-cyclodextrin (γ-CD), heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD), and 1,1′-diheptyl-4,4′-bipyridinium dibromide (HB) have been examined by studying absorption, fluorescence, and induced circular dichroism spectra of TCPP. TCPP has been found to form inclusion complexes with γ-CD and TM-β-CD. The stoichiometries of the γ-CD–TCPP and TM-β-CD–TCPP inclusion complexes are 1 : 1 and 2 : 1, respectively. Because the equilibrium constant for the formation of the 2 : 1 TM-β-CD–TCPP inclusion complex is exceedingly large (4.34 × 1018 mol−2 dm6), the TM-β-CD–TCPP inclusion complex is quantitatively formed in TCPP solutions containing two equivalents of TM-β-CD. TCPP also forms an organic cation–organic anion complex with HB. In the presence of γ-CD, the TCPP–HB complex forms a 1 : 1 : 1 γ-CD–TCPP–HB inclusion complex, although TM-β-CD causes the dissociation of the TCPP–HB complex into its components. The equilibrium constant for the formation of the γ-CD–TCPP–HB inclusion complex from the TCPP–HB complex and γ-CD has been evaluated to be 905 mol−1 dm3.
  • Ichiro Uechi, Masao Fujiwara, Yoshihisa Fujiwara, Yohsuke Yamamoto, Yo ...
    Type: Article
    Subject area: TP
    2002 Volume 75 Issue 11 Pages 2379-2382
    Published: 2002
    Released: November 15, 2002
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    External magnetic fields (≤ 6 kG) significantly increase yields of I3 and H2 as well as oxidation currents in anodic oxidation of potassium iodide. The Lorentz force on ions in the solution induces convection of solution, resulting in acceleration of the entire reaction rate. This is further confirmed from the observation that reddish-brown streams of I3 in the solution, moving downward at zero field, undergo turbulent motion in magnetic fields.
  • Kazumasa Honda
    Type: Short Articles
    Subject area: TP
    2002 Volume 75 Issue 11 Pages 2383-2384
    Published: 2002
    Released: November 15, 2002
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    The crystal structure of the photodimer of 2-benzyl-5-benzylidenecyclopentanone was determined using a recrystallized crystal. It was identical to that of an as-photoirradiated dimer crystal obtained by a single-crystal-to-single-crystal photoreaction of the monomer. This suggests that the starting material already possesses the most favored crystal phase for the products.
  • Akinori Ito, Shishin Yamada, Takuya Higuchi, Yuzo Ishikawa, Yoko Nagat ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2385-2391
    Published: 2002
    Released: November 15, 2002
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    Anthropogenic emissions of methane (CH4) from major sources such as landfills, automobiles, and rice paddy fields in the Nagoya metropolitan area were estimated using several emission process parameters such as emission factors and activity data for the decade from 1988 to 1997. The sum of CH4 amounts emitted from these three major sources was calculated to be 4.93 Gg of CH4 in 1988 and 5.19 Gg of CH4 in 1997. Methane emissions from the 12 landfill sites located around the Nagoya metropolitan area gradually increased until 1996 and then decreased in 1997, while those from automobiles and rice paddy fields continuously declined for the same decade. The total amount of CH4 emitted from the 12 landfills was much larger than those from other two sources. In 1993, for example, the amount was estimated as 3.26 Gg of CH4, 58% of which was generated from the largest landfill site. The excess CH4 concentration in the urban atmosphere, which was estimated from the difference between the CH4 concentration at the urban site and the background CH4 concentration at the Mauna Loa observatory, Hawaii, USA, showed the long-term trends similar to the CH4 emission from the largest landfill site. As a result, we conclude that the CH4 emission from the largest landfill dominantly impacted on the excess CH4 concentration due to the major sources in the Nagoya metropolitan area.
  • Taro Tsubomura, Mitsuru Ito, Tomochika Fujita
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2393-2402
    Published: 2002
    Released: November 15, 2002
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    The conformations of metal complexes of 18-membered tetraimino macrocycles have been studied. A correlation between the bond length of the metal–nitrogen bond and the conformation of the macrocycle has been found in the published X-ray data. Molecular mechanics (MM) calculations based on the Points-On-a-Sphere (POS) method reproduce the correlation. The effect of the MM force constants on the conformation of the ligand has been extensively studied. The MM study clarified that the conformation of the macrocycle is principally determined by the length of the coordination bond and that the methyl groups substituted at the imine carbon plays an important role in the conformation of the macrocycles. Two X-ray crystal structure analyses of macrocycle LH complexes, [Ba(LH)(ClO4)2Ba(LH) (H2O)(ClO4)-(μ-ClO4)] and [Sr(LH)(ClO4)2], were included in the study to complement the structural data.
  • Yasuzo Sakai, Norihiro Kato, Misako Arai, Fujio Takahashi, Yuichi Nish ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2403-2406
    Published: 2002
    Released: November 15, 2002
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    The properties of cationic surfactant-clay mixtures were examined by measurements of the electric conductivity, absorption spectra, and X-ray diffraction patterns. The orientation of N-[[4-(aminoiminomethyl)amino]butyl]dodecanamide (DAG) as a intercalated cationic surfactant and the thickness of the interlayer space of clay using Na-saponite (Sumecton SA) were investigated. DAG molecules were intercalated in a 1 nm gap in the interlayer space of clay. It is speculated that alkyl groups of the surfactant molecules are placed not parallel, but inclined slightly vertical to the internal surface of Na-saponite.
  • Yoshihiro Mitsutsuka, Nobuhiko Nawa, Shuji Yoshizawa, Hirofumi Yajima, ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2407-2413
    Published: 2002
    Released: November 15, 2002
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    From single crystals of trans(Cl)-[CoCl2(NH3)3(H2O)]Cl, thin sections with different orientations and different thicknesses were prepared, and their polarized absorption spectra were examined in the 350–850 nm region using a microspectrophotometer. Two absorption peaks, caused by the (x2y2xy)-type transitions of the d-electrons of Co, were found: a 15750 cm−1 peak was assigned to overlapping A2 ← A1 and B2 ← A1 type transitions of the complex ion with C2v symmetry; a 19210 cm−1 peak was assigned to a B1 ← A1 type transition. The molar extinction coefficients (ε) were determined at each of these peaks: ε(||c) = 104 and ε (⊥c) = 16 l cm−1 mol−1 at 15750 cm−1, and ε(||c) = 5 and ε(⊥c) = 54 l cm−1 mol−1 at 19210 cm−1. These ε values were explained by taking distortions of the d-electron orbitals into consideration, that are partly caused by the oxygen atom coordination and partly by some vibronic couplings between the d-electron orbitals and cobalt-ligand stretching vibrations.
  • Yoshiro Honma
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2415-2421
    Published: 2002
    Released: November 15, 2002
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    In order to explore the cause of a distinctive extraction behavior of Cr(VI) in the dithiocarbamate formation-solvent extraction systems, extracted chromium compounds were investigated and relationships between the formation of the compounds and the extraction behavior were studied. Chromatographic separation and spectroscopic analyses showed that two kinds of chromium(III) dithiocarbamates (i.e. tris(1-pyrrolidinecarbodithioato)chromium(III) and bis(1-pyrrolidinecarbodithioato)[1-pyrrolidinecarbothio(thioperoxoato)]chromium(III)) were formed and extracted in an ammonium 1-pyrrolidinecarbodithioate (APCD)/diisobutyl ketone (DIBK) solvent extraction system. The two products comprised most of the extracted chromium. Concentrations of the two dithiocarbamates in extracts were determined using double wavelengths analysis. The dependence of concentration ratio of the two complexes on pH was also investigated. The results of the investigation clarified that a major extract obtained under high pH condition was the thioperoxo complex and that the percentage of the tris complex increased with decreasing pH. Furthermore, it was clarified that the unusual extraction behavior of chromate was distinguished by the formation of thioperoxo complex. In order to elucidate the formation mechanism of the thioperoxo complex, the origin of an oxygen atom in the molecule of the thioperoxo complex was determined with an isotope labeling technique. The labeling experiments clarified that the source of the oxygen atom of the complex molecule was chromate ion and that the oxygen atom was fixed to chromium atom prior to the rate determination step of the formation of the thioperoxo complex.
  • Yutaka Yoshikawa, Kenji Kawabe, Makoto Tadokoro, Yuka Suzuki, Naohisa ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2423-2432
    Published: 2002
    Released: November 15, 2002
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    Twelve new amino acid derivatives/Zn(II) complexes were prepared by the reactions of ZnSO4 and nine tetradentate ligands, Gly, Ala, Val, Leu, Ser and His derivatives and three pentadentate ligands, Asp and His derivatives. The X-ray structure analysis of [Zn3(N-pyridylmethyl-His)3(H2O)2](ClO4)3·2H2O revealed the formation of a trinuclear complex, in which three tetradentate ligands and two water molecules coordinate to three Zn(II), but the complex in an aqueous solution is present as a monomeric complex ion. Several Zn(II) complexes were found to have in vitro insulinomimetic activity which was estimated by the inhibition of free fatty acid release in isolated rat adipocytes treated with epinephrine. It was revealed that the insulinomimetic activities of Zn(II) complexes with the stability constants (log β) less than 11 were higher than that of VOSO4 and were comparable to that of ZnSO4 as positive controls except in the cases of two complexes with Gly derivatives, Zn(N,N-dipyridylmethyl-Gly)+ and Zn(N,N′-trimethylene-bis-Gly).
  • Takayoshi Suzuki, Takashi Kuchiyama, Shinobu Kishi, Sumio Kaizaki, Mas ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2433-2439
    Published: 2002
    Released: November 15, 2002
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    Mixed-ligand bis(2,2′-bipyridine)ruthenium(II) complexes containing a hybrid donor-type P–N ligand of 8-(diphenylphosphino)quinoline (Ph2Pqn) or 2-(diphenylphosphino)pyridine (Ph2Ppy), [Ru(bpy)2(Ph2Pqn or Ph2Ppy)](PF6)2 (1 or 2; bpy = 2,2′-bipyridine), have been prepared. The X-ray crystal structure analyses of 1 and 2 revealed that Ph2Pqn and Ph2Ppy act as a bidentate ligand to form a five- and four-membered chelate ring, respectively. The four-membered chelate ring formed by Ph2Ppy has a very small bite angle (P(1)–Ru–N(1): 68.4(1)°), but the RuII(bpy)2 moiety in 2 has a typically strain-free structure. On the other hand, in the Ph2Pqn complex 1, one of the bpy planes is skewed remarkably from the Ru coordination plane due to an intramolecular steric interaction with a phenyl ring of Ph2Pqn. The redox potentials and the 1MLCT transition energies of the Ph2Pqn and Ph2Ppy complexes (1 and 2) were not so different from the averaged values of those of the corresponding 1,2-bis(diphenylphosphino)benzene (dppb) and 1,10-phenanthroline (phen) complexes, [Ru(bpy)2(dppb or phen)](PF6)2 (3 or 4). These facts indicate that the electronic asymmetry inherently present in Ph2Pqn and Ph2Ppy does not affect remarkably the ground state properties of the complexes. However, unlike complexes 24, the Ph2Pqn complex 1 in EtOH/MeOH (4 : 1) glass at 77 K exhibited a novel dual emission, giving a biexponential emission decay. The shorter-lived (τ = 10.8 µs) emission is attributable to the bpy-based 3MLCT emission, similar to the other RuII-polypyridine complexes, while the longer-lived (τ = 62.1 µs) emission can probably be assigned as arising from the quinoline-based 3(π–π*) excited state.
  • Yonezo Maeda, Akiko Ishida, Masaaki Ohba, Shinji Sugihara, Shinya Haya ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2441-2448
    Published: 2002
    Released: November 15, 2002
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    Mixed-valence dinuclear iron(II,III) complexes, [FeIIFeIII(bpmp)(L)2](BF4)2, have been prepared, and the structures, electrochemical properties and rates of intramolecular electron transfer of the complexes have been examined, where Hbpmp represents 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol and L is 2-methoxybenzoate (omb), 3-methoxybenzoate (mmb), 4-methoxybenzoate (pmb), 3,5-dimethoxybenzoate (dmb), 3,4,5-trimethoxybenzoate (tmb) or 4-biphenylcarboxylate (bpc). It turns out from the Mössbauer spectra that the valence states of iron atoms of [FeIIFeIII(bpmp)(omb)2](BF4)2, [FeIIFeIII(bpmp)(pmb)2](BF4)2, [FeIIFeIII(bpmp)(tmb)2](BF4)2 and [FeIIFeIII(bpmp)(bpc)2](ClO4)2 are localized at 78 K and delocalized at 293 K. The temperature dependence of the spectra is interpreted by assuming intramolecular electron transfer between two energetically equivalent vibronic states FeAIIFeBIII and FeAIIIFeBII. The Mössbauer spectra of [FeIIFeIII(bpmp)(dmb)2](BF4)2 show the superposition of the relaxation spectrum between iron(II) and iron(III), and of the spectrum of the average valence states at 293 K; the average valence states are partly observed even at 78 K. The valence states of [FeIIFeIII(bpmp)(mmb)2](BF4)2 are localized over the temperature range from 78 K to 293 K. The single-crystal X-ray structure of [FeIIFeIII(bpmp)(bpc)2](ClO4)2 was determined at 293 K. The complex crystallizes in the orthorhombic space group Fdd2, which has a unit cell of a = 27.056(1) Å, b = 42.652(0) Å, c = 12.151(0) Å and Z = 8. A refinement was performed with 2340 unique reflections [I > 3σ(I)] to give R = 0.085, Rw = 0.099. The two iron atoms are located symmetrically to a C2 axis, which presents in the molecule, and are crystallographically equivalent. The mean Fe–O length is intermediate between the FeII–O and FeIII–O values, indicating that both iron atoms are in an averaged valence state.
  • Mohammed Enamullah, Miki Hasegawa, Yutaka Fukuda, Wolfgang Linert, Tos ...
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2449-2453
    Published: 2002
    Released: November 15, 2002
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    2,2,2-Tris(diphenylphosphinomethyl)ethane (triphos) coordinates to Co(BF4)2·6H2O to synthesis the red-violet cationic complex of [Co(triphos)(solv)2]2+ (solv: solvent) in THF/EtOH at room temperature. Addition of 2-hydroxy-2-D-carboxylic acids (L) into the cationic solution as co-ligands yields the red-brown complexes of [Co(L-2-hydroxy-2-methylacetato)(triphos)] (I), (Co(D-2-hydroxy-2-phenylacetato)(triphos)] (II), (Co(L-2-hydroxy-2-phenylacetato)(triphos)] (III) and [Co(D-2-hydroxy-2-phenyl-2-methylacetato)(triphos)] (IV). The complexes are characterized by elemental analysis, IR-, UV-vis.-, NMR- and Mass-spectroscopy. All complexes are paramagnetic. Variable temperature studies on magnetic susceptibilities (χM) measurements show the spin-crossover behaviors of the complexes with ΔHsc = −5.3 to −6.8 kJ mol−1 and ΔSsc = −31 to −36 J mol−1 K−1 in methanol.
  • Yoshitaka Doi, Takayuki Ishida, Takashi Nogami
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2455-2461
    Published: 2002
    Released: November 15, 2002
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    Antiferromagnetic phase transitions of M(N3)2(pm) were observed at 51, 39, 41, and 46 K for M = Mn, Fe, Co, and Ni, respectively; here pm denotes pyrimidine. Single-crystal X-ray crystallographic analysis for M = Mn, Fe, and Co and powder X-ray diffraction measurements for M = Ni revealed that they were isomorphous. The N3 and pm moieties contribute μ-1,3-bridged two-dimensional and μ-1,3-bridged one-dimensional structures, respectively, thus forming a three-dimensional framework. Antiferromagnetic couplings through the bridging ligands are consistent with superexchange mechanisms based on the coordination geometry determined. Small spin canting was observed below the transition temperature for M = Mn and Fe. The cant angles are estimated to be 0.06 and 0.13°, respectively, from the spontaneous magnetization at 10 K.
  • Tomoaki Ise, Takayuki Ishida, Takashi Nogami
    Type: Article
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2463-2468
    Published: 2002
    Released: November 15, 2002
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    We report here the structures and magnetic properties of hnn and hin complexes with copper(II) and manganese(II) hexafluoroacetylacetonates, [{Cu(hfac)2(H2O)}2(μ-hnn)] (1), [Cu(hfac)2(hin)2] (2), and [Mn(hfac)2(hin)2] (3). X-ray crystallographic analysis of 1 revealed that 1 was a dinuclear complex containing an hnn bridge. Magnetic measurements of 1 indicate the presence of intramolecular ferromagnetic coupling between copper and radical spins. The data were analyzed as a metal-radical-metal three-spin system, giving 2J/k = +16.2 K (H = −2J(S1S2 + S2S3)). The ferromagnetic interaction can be explained in terms of the axial coordination of the hnn nitrogen to Cu(II). Complexes 2 and 3 were revealed to be isomorphous mononuclear complexes possessing two hin ligands. Although the molecules have a radical-metal-radical system, the magnetic data of 3 could not be analysed only with intramolecular interactions. Strong intermolecular antiferromagnetic interactions (2|J|/k >> 300 K) were suggested among the hin ligands because the interatomic O···N distances (2.41–2.51 Å) were shorter than the sum of the van der Waals radii for 2 and 3. These strong interactions are successfully introduced to metal-radical hybrid systems owing to the choice of small ligands, although the complexes do not possess polymeric networks.
  • Toshi Nagata, Koji Tanaka
    Type: Short Articles
    Subject area: AI
    2002 Volume 75 Issue 11 Pages 2469-2470
    Published: 2002
    Released: November 15, 2002
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    Syntheses of a new planar terdentate ligand, 6-(3,5-diphenyl-2-pyrrolyl)-2,2′-bipyridine (L1H) and its ruthenium(II) complex ([Ru(L1)2]) are reported. The X-ray structure of [Ru(L1)2] showed the distorted octahedral Ru(II) center similar to the structures of terpyridine complexes. The cyclic voltammograms revealed that [Ru(L1)2] was more easily oxidized than [Ru(terpy)2]2+ by 1.10 V.
  • Gerardo. R. Echevarría Gorostidi, José G. Santos, Andrea ...
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2471-2476
    Published: 2002
    Released: November 15, 2002
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    The apparent rate constants of the formation (k1) and hydrolysis (k2) of the Schiff bases formed by pyridoxal 5′-phosphate with L-tryptophan and their methyl and n-butyl esters at a variable pH, 25 °C, and an ionic strength of 0.1 M were determined, along with the equilibrium constant (KpH). The individual rate constants of formation and hydrolysis of the Schiff bases of systems corresponding to different chemical species present in the medium as a function of its acidity were also determined, as were the pK values for the Schiff bases. The influence of the α-carboxyl group on the formation and hydrolysis constants of the Schiff bases, and also on their pK values, is demonstrated.
  • Young-Dae Gong, Soo-Kyung Kim, Sung-eun Yoo, Mark J. Kurth
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2477-2480
    Published: 2002
    Released: November 15, 2002
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    An efficient and diastereoselective route for the synthesis of 2,5,6,7-tetrasubstituted-1H-pyrrolo[1,2-c]imidazoles has been developed using intramolecular azomethine ylide cycloaddition and carbanilide cyclization. Ab initio calculations at the 6-31G (d,p) basis set reveal that the thermal stability of diastereomers determine the epimerization during the intramolecular carbanilide cyclization (→ hydantoin). These stereochemical results are consistent with an endo-like cycloaddition of a trans,anti-azomethine ylide followed by base-mediated C7a-H epimerization (C7a-Hβ → C7a-Hα) to deliver the thermodynamically preferred trans,anti,trans-(Ha-Hb, Hb-Hc, Hc-Hd)-pyrrolidine stereochemistry (3) which is ca. 20.1 kJ/mol more stable than the trans,anti,cis-pyrrolidine stereochemistry. In the case of 2-hydroxy-1-naphthaldehyde, naphthalene ring steric effects result in a different stereochemical arrangement about each pyrrolidine ring.
  • Wafaa Mahmoud Abdou, Mounir Abdou Ibrahim Salem, Ashraf Ahmed Sediek
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2481-2485
    Published: 2002
    Released: November 15, 2002
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    3,5-Di-tert-butyl-1,2-benzoquinone 1-oxime (1b) reacted with ester ylides 2a,b to give the corresponding 2H-1,4-benzoxazin-2-ones 9a,b along with the 3H-indol-3-one 11, whereas with keto ylides 12a,b, 2,3-dihydrobenzoxazoles 13a,b were isolated. Conversely, the reaction of 1b with moderated phosphonium salt 15 proceeded under phase-transfer catalysis conditions to afford the 2H-1,4-benzoxazine derivative 19, instead of the expected Wittig reaction product.
  • Majjigapu Janaki Ram Reddy, Uppalanchi Srinivas, Kolupula Srinivas, Vu ...
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2487-2495
    Published: 2002
    Released: November 15, 2002
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    Several (16) 9-anthraceneacrylic esters were synthesized in order to study photochemical E(trans)–Z(cis) isomerization. All of the compounds 16 underwent selective E-to-Z isomerization upon direct excitation (> 400 nm) in organic solvents, leading to the formation of a thermodynamically less stable Z isomer over 96%. Triplet sensitized isomerization selectively produces the Z-to-E isomer in over 98%. The higher quantum yield of isomerization observed in the triplet-sensitized Z-to-E isomerization process informs us that a “quantum chain” process is in operation. Fluorescence data generated on all compounds indicate that the E-to-Z isomerization process involves a charge-transfer or polar singlet excited state.
  • Takeshi Hanamoto, Kumiko Handa, Tomonori Mido
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2497-2502
    Published: 2002
    Released: November 15, 2002
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    We have found that tributyl(1-fluorovinyl)stannane (2) could be readily prepared from the reaction of (1-fluorovinyl)methyldiphenylsilane1 (1) and bis(tributyltin) oxide in the presence of a catalytic amount of CsF in DMF in good yields. The palladium-catalyzed carbonylative cross-coupling reaction of 2 with aryl iodides bearing various functional groups smoothly proceeded giving the corresponding aryl 1-fluorovinyl ketones in good yields under an atmospheric pressure of carbon monoxide. A similar carbonylative cross-coupling reaction of 2 with aryl triflates was also accomplished in the presence of tetrabutylammonium iodide (Bu4NI) as an additive.
  • Sadayuki Matsuda
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2503-2507
    Published: 2002
    Released: November 15, 2002
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    The conformation changes of S-100a.a′ and S-100b caused by Mg2+-binding were determined by several methods. The fluorescence intensity of the Ca2+-bound S-100a.a′ was enhanced by the Mg2+-binding. The conformation changes in Ca2+/S-100a.a′ and Ca2+/S-100b caused by Mg2+-binding were also detected using a fluorescence environmental probe, 2-p-toluidinonaphthalene-6-sulfonate (TNS). The reactivities of the cysteine (Cys) residues in S-100a.a′ and S-100b to a thiol-specific reagent, 2,2′-dinitro-5,5′-dithiodibenzoic acid (DTNB), were increased by the Mg2+-binding, regardless of the Ca2+-binding.
  • Yoko Sugiyama, Hiroaki Takahashi, Akio Saito
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2509-2515
    Published: 2002
    Released: November 15, 2002
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    During research to synthesize 13-deoxy-13β-substituted ivermectin aglycons, unexpected unique products, 13β-substituted-14Z ivermectin aglycons, were obtained. We will report the results of that series of studies and a possible reaction mechanism.
  • Rumi Kimura, Tanemasa Nagano, Hideki Kinoshita
    Type: Article
    Subject area: OB
    2002 Volume 75 Issue 11 Pages 2517-2525
    Published: 2002
    Released: November 15, 2002
    JOURNALS RESTRICTED ACCESS
    Ethyl N-Boc- and N-Z-α-tosylglycinates were reacted with a variety of aldehydes in the presence of tributylphosphine and a base to afford the corresponding α,β-didehydroamino acid derivatives with high (Z)-selectivity in good yields. Moreover, ethyl (4S)- and (4R)-2-(N-Boc-amino)-4,5-isopropylidenedioxy-2-pentenoates prepared by the present method were converted to (2S, 4S)- and (2R, 4R)-4-hydroxyprolines, respectively.
  • Xing-Zheng Wu, Takeshi Yamamoto, Masanori Hatashita
    Type: Article
    Subject area: AM
    2002 Volume 75 Issue 11 Pages 2527-2532
    Published: 2002
    Released: November 15, 2002
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    Radiolytic degradation of chlorinated hydrocarbons (chloroform, trichloroethylene, and tetrachloroethylene) in water was carried out. Water solutions of the chlorinated hydrocarbons with different concentrations were irradiated with γ rays. Concentrations of methane, ethane, CO, CO2, H2, and O2 after the irradiation were determined by gas chromatography. Concentration of chloride ion in the irradiated sample was determined by ion chromatography. Experimental results show that radiolytic degradation of the chlorinated hydrocarbon increased with the radiation dose. Methane, ethane, CO2, H2, and Cl concentrations increased with the radiation dose and the sample concentration. On the other hand, O2 concentration decreased with the radiation dose and the sample concentration. When sample concentration was high, dissolved oxygen might be not enough for converting most of the C atoms in the sample into CO2. This resulted in a low decomposition ratio. Addition of H2O2 as an oxygen resource could increase the decomposition ratio greatly. Furthermore, gas chromatography-mass spectroscopy was applied to identify some intermediates of the radiolytic dehalogenation. Radiolytic degradation mechanisms are also discussed.
  • Ken’ichi Aoki, Masaru Nakagawa, Takahiro Seki, Kunihiro Ichimura
    Type: Article
    Subject area: AM
    2002 Volume 75 Issue 11 Pages 2533-2539
    Published: 2002
    Released: November 15, 2002
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    Two ways to control the macroscopic morphology of fibrous organizates of amphoteric azopyridine carboxylic acids by tuning the strength of ππ stacking among the component molecules are presented. The self-organization of the azopyridine carboxylic acids (15) from aqueous solutions is governed not only by carboxyl/pyridyl hydrogen bondings, but also by dipole–dipole and ππ stacking interactions. The level of the latter could be tuned by the substituent structure at the phenyl ring. As a result, whereas leaflet crystals were formed from non-substituted derivative 1, 3 with a propyl substituent gave fibrous assemblages, and needle-like assemblages were obtained from 2, 4, and 5 with methyl, s-butyl, and ethoxy substituents, respectively. The propyl-substitution is likely to enhance an anisotropic growth rate of the intermolecular hydrogen bonds due to efficient suppression of ππ stacking among aromatic cores, leading to the appearance of microfibers with the highest aspect ratio. The second way to control the organization morphology is based on “supramolecular copolymerization”, which is attained by mixing 1 and 3 to modulate the strength of the ππ stacking. The aspect ratio of fibrous materials was significantly influenced by the mixing ratio.
  • Kensuke Naka, Akihiro Kobayashi, Yoshiki Chujo
    Type: Article
    Subject area: AM
    2002 Volume 75 Issue 11 Pages 2541-2546
    Published: 2002
    Released: November 15, 2002
    JOURNALS RESTRICTED ACCESS
    The precipitation of CaCO3 in the absence or the presence of the G4.5 PAMAM dendrimer was carried out by a “carbonate diffusion method”. Formation of crystalline CaCO3 at different feed ratios of the G4.5 dendrimer to calcium ions was studied with the concentration of calcium ions kept at 0.1 M. Although calcite was predominantly formed at the concentration of the G4.5 PAMAM dendrimer corresponding to 2.65 mM of –COONa, the crystal phase of the obtained CaCO3 at the higher concentration of the G4.5 PAMAM dendrimer at 5.3 mM consisted entirely of vaterite. As the concentration of –COONa increased from 5.3 to 10.6 mM, the particle sizes of the spherical vaterites were reduced from 8.7 ± 1.0 to 5.2 ± 3.0 μm determined by SEM observation. The crystal phase of the obtained CaCO3 in the absence of any additives was a mixture of calcite and vaterite. Although vaterite was predominantly formed by the G4.5 dendrimer, relatively high amounts of calcite were observed in the case of the G3.5 and G1.5 dendrimers. These results suggest that the G4.5 dendrimer more effectively induces vaterite formation compared with the earlier generation of the dendrimers.
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