Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 78 , Issue 10
Showing 1-22 articles out of 22 articles from the selected issue
Award Accounts
The Chemical Society of Japan Award for 2003
  • Hiroshi Nakatsuji
    2005 Volume 78 Issue 10 Pages 1705-1724
    Published: 2005
    Released: October 04, 2005
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    A brief summary of the author’s research projects for deepening and extending the quantum principles in chemistry is given. First, the structure of the exact wave function that is the solution of the Schrödinger equation was clarified and a method of calculating it starting from an approximate wave function is given. The singularity problem intrinsic to atoms and molecules was overcome, and a general method of solving the Schrödinger equation in an analytical form has been established. Quantum chemistry of excited states and ionized states is essential since it is difficult with experiments alone to explore this field due to the short lives of these species. The SAC-CI theory developed in the author’s groups offers a powerful method for investigating the chemistry of excited and ionized states. The energy gradient method incorporated into this program is particularly useful for studying geometries and reactions involving these states. The catalysis on a metal surface is a magic process that must be clarified with the help of quantum theory. The author studied it using his dipped adcluster model (DAM) that includes the effects of the free electrons of the bulk metal. The epoxidation reactions of ethylene and propylene were studied with this method. The NMR chemical shifts include much information about the valence electrons of molecular systems. The author clarified that the major electronic mechanisms of the chemical shifts could be attributed to the intrinsic atomic properties that are related to the position of the element in the periodic table. For the chemical shifts induced by heavy ligands, the relativistic effect is sometimes dominant. The spin-orbit effect is most important for light resonant nuclei. For heavier resonant nuclei, other spin-free relativistic effects and the electron correlation effects are also important and they strongly couple with each other, implying an existence of something “unexpected” in the chemistry of heavy elements. Finally, the strategy of the author’s study in quantum chemistry is shortly described.
The Chemical Society of Japan Award for Young Chemists for 2003
  • Hitoshi Miyasaka, Rodolphe Clérac
    2005 Volume 78 Issue 10 Pages 1725-1748
    Published: 2005
    Released: October 04, 2005
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    A magnetically-isolated one-dimensional chain can behave as if “magnet”— this sentence may be opposed to our common sense. In this review, we will show that a “magnet-like” behavior can effectively be found in only a magnetic spin chain. In 2001, which is almost forty years after the pioneering theoretical work of R. J. Glauber [J. Math. Phys., 4, 294 (1963)] on the dynamics of ferromagnetically-coupled Ising spin chains, the first experimental evidence of such behavior has been discovered in a real one-dimensional compound [A. Caneschi et al. Angew. Chem., Int. Ed., 40, 1760 (2001)]. In 2002, we have reported on a one-dimensional compound [Mn2(saltmen)2Ni(pao)2(py)2](ClO4)2 (saltmen2− = N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminato), pao = pyridine-2-aldoximato, and py = pyridine) which can be considered as a chain of ferromagnetically-coupled anisotropic ST = 3 units [J. Am. Chem. Soc., 124, 12837 (2002)]. Magnetic measurements on this compound revealed the presence of slow relaxation and large field-dependent hysteresis of the magnetization at low temperatures. The topology of this chain is very close to the “ideal” chain imagined by Glauber and hence, still to date, the simplest system to probe the Glauber dynamics. By analogy to the Single-Molecule Magnets described in the introduction of this paper, we called this type of material: Single-Chain Magnet (SCM). To obtain simple SCM systems, we have developed a step-by-step synthetic strategy using primary and secondary building blocks to control the chemistry of the targeting materials and the physics of their characteristic magnetic properties. In this review, we will describe this synthetic strategy from the elementary building blocks to the final series of Single-Chain Magnets obtained since 2002. The magnetic properties of all these materials will be discussed in detail. In particular, the experimental SCM behavior will be described and analyzed in relation with the generalization of the Glauber model for real systems.
BCSJ Award Article
  • Seiji Sakamoto, Kazuaki Kudo
    2005 Volume 78 Issue 10 Pages 1749-1756
    Published: 2005
    Released: October 04, 2005
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    Peptides possessing the DNA-binding capability were successfully introduced into myoglobin by a cofactor-reconstitution strategy. We have designed and synthesized an artificial iron–protoporphyrin IX (heme)–peptide conjugate, Heme(br)2, which has covalently conjugated GCN4 basic region peptides at the heme propionate groups as an artificial DNA-binding site. The peptide Heme(br)2 was inserted into apomyoglobin to give a peptide-conjugated myoglobin, Mb(br)2. The UV–vis and circular dichroism spectra of Mb(br)2 were comparable to those of native myoglobin, suggesting that the heme environment and three-dimensional structure of Mb(br)2 were almost identical to those of native myoglobin. The size exclusion chromatography indicated that the Mb(br)2 existed as a monomeric form in an aqueous solution and interacted with its target DNA sequence [c-AMP responsive element (CRE)]. The fluorescence study also revealed that the Mb(br)2 bound CRE DNA effectively with 1/1 stoichiometry [affinity constant; 8.4 (±0.8) × 107 M−1]. Additionally, the CRE DNA-binding enhanced the peroxidase-like activity of Mb(br)2, possibly due to the partial structural perturbation around the heme active-site. These results demonstrate that the chemical modification of prosthetic group with functional peptides can provide a new strategy for the design of semi-artificial proteins with engineered function.
Articles
  • Yasunori Ohashi, Yuya Takeuchi, Mutsumi Hirama, Hisashi Yoshioka, Hiro ...
    2005 Volume 78 Issue 10 Pages 1757-1762
    Published: 2005
    Released: October 04, 2005
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    The reaction rate constants of antioxidants with the hydroxyl radical (HO) were determined by a rapid-flow ESR method. ESR spectra of the antioxidant radical formed by a reaction with HO generated from the Ti3+ + H2O2 system were measured. When an antioxidant and ethanol were mixed with HO, a superposed spectrum of the 1-hydroxyethyl radical and antioxidant radical was obtained. The intensity ratio of the signals of these radicals was calculated from the doubly integrated curve, and then the ratio of the reaction-rate constant of the antioxidant with HO to that of ethanol was obtained. The ratios of pyrogallol, gallic acid, catechol, phloroglucinol, resorcinol, and methanol were 19, 17, 11, 1.5, 1.2, and 0.56, respectively. The dissociation energies of the bonds in antioxidant molecules were obtained by MO calculations, which demonstrated that phenoxy, hydroxymethyl, and 1-hydroxylethyl radicals were formed by the reactions with HO, as expected from their spectra. The relationship between the relative activation energies obtained from the rate constants and the bond-dissociation energies showed that the Evans–Polanyi equation holds in polyphenol series, but the line was shifted from that of alcohols. This suggested that the structures of the transition state of alcohols were stabilized by a polar effect.
  • Naader Alizadeh, Maryam Bordbar, Mojtaba Shamsipur
    2005 Volume 78 Issue 10 Pages 1763-1772
    Published: 2005
    Released: October 04, 2005
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    1H NMR spectroscopy was used to investigate the stoichiometry, stability, and exchange kinetics and mechanism of ligand interchange for Tl+ complexes with hexacyclen (HCY) and hexamethylhexacyclen (HMHCY) in dimethylformamide (DMF) solution. In both cases, a stable complex with a 1:1 stoichiometry was formed in solution. A complete line-shape analysis was used to evaluate the mean exchange times and exchange rates. The two-site chemical exchange between Tl+ and HCY proceeded via a dissociative ligand-interchange mechanism in the temperature range 250–310 K. However, the 1H NMR spectra of the Tl+–HMHCY complex system in DMF, in about the same temperature range, revealed the predominance of a three-site exchange process in the system. The type of exchange was dependent on the Tl+/HMHCY mole ratio, ρ. At ρ < 1, ligand exchange occurs via a dissociative mechanism, while at ρ > 1, a bimolecular metal exchange is the predominate mechanism. In this case, the main factors controlling the exchange rates are the conformational rearrangement of the ligand during a concerted partial decomplexation of a Tl+ cation and partial complexation of a second one. The activation parameters (Ea, ΔH, ΔS, and ΔG) for the exchange processes (i.e. the ligand exchange, metal exchange, and the conformational change of the complex) were determined and compared with those for a two-site exchange for the Tl+–HCY system.
  • Youichi Hosokawa, Suguru Maki, Toshi Nagata
    2005 Volume 78 Issue 10 Pages 1773-1782
    Published: 2005
    Released: October 04, 2005
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    Gold nanoparticles (1.5–1.7 nm) were prepared by use of three tripod thioether oligomers as stabilizing molecules. The particle sizes were independent of the sizes of the stabilizers, and were smaller than those stabilized with simpler thioethers. Molecular dynamics simulations were performed to examine how the stabilizers adsorb on the nanoparticles. Parameters were developed for modeling the interactions between gold and organic molecules. Simulations in explicit chloroform solvent at 300 K revealed multiple-point adsorption of the stabilizers on the nanoparticles.
  • Paramasivam Manisankar, Anandhan Gomathi
    2005 Volume 78 Issue 10 Pages 1783-1790
    Published: 2005
    Released: October 04, 2005
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    The preparation and electrochemical characterization of 9,10-anthraquinones adsorbed clay-modified and anthraquinones–clay composite-modified glassy carbon electrodes (GCEs) were investigated. The influence of the pH on the electrochemical behavior and stability of the clay-modified electrodes (CMEs) were studied by cyclic voltammetry in acidic and neutral aqueous media. For the dioxygen reduction, anthraquinones adsorbed clay-modified electrodes possess good electrocatalytic abilities with overpotential ranging from 174 to 452 mV, lower than the bare GCE in the pH range 4.0–7.0; also, anthraquinones–clay composite-modified electrodes exhibited potent catalytic activities with an overpotential of about 128–421 mV lower than at a bare GCE at pH 7.0–8.0. The diffusion coefficients of mediators in clay films were evaluated by chronoamperometric techniques. Chronocoulometric studies showed the involvement of two electrons in the reduction of anthraquinones and four electrons in dioxygen reduction at the optimum pH. In addition, hydrodynamic voltammetric studies were performed to determine the mass-specific activity of the anthraquinones used, the heterogeneous rate constants for the reduction of O2 at the surface of modified electrodes and the apparent diffusion coefficient of O2 in aqueous O2-saturated buffer solutions.
  • Kazuhiko Tsukagoshi, Naoya Jinno, Kae Toguchi, Riichiro Nakajima
    2005 Volume 78 Issue 10 Pages 1791-1794
    Published: 2005
    Released: October 04, 2005
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    We have proposed competitive immunoassay using capillary electrophoresis (CE) with a chemiluminescence (CL) detector, in which a small amount of sample (ca. 20 μL) is required for analysis. Human serum albumin (HSA) and anti-human serum IgG (anti-HSA) were used for immune reaction as a model. A luminol and hydrogen peroxide CL reaction was adopted, and HSA was labeled with isoluminol isothiocyanate (ILITC) for competitive immunoassay. The reactant after the immune reaction was directly subjected to CE with the CL detector, where the labeled HSA was easily and rapidly separated and detected. The amount of labeled HSA indicated a good relationship to that of HSA as an analyte through the immune reaction. The HSA was determined over the range of 0.2–1.2 μM with a detection limit of 0.1 μM (S/N = 3). The present method features high sensitivity, a small sample volume, and easy and rapid operation. The method also shows the possibility to analyze a specific protein in a serum sample.
  • Reiko Jikido, Hitomi Shiraishi, Kanako Matsufuji, Masaaki Ohba, Hideki ...
    2005 Volume 78 Issue 10 Pages 1795-1803
    Published: 2005
    Released: October 04, 2005
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    Dinuclear metal(II) complexes of 2,6-bis{N-[(2-dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL), [Mn2(L)(AcO)2(NCS)] (1), [Co2(L)(AcO)2]BPh4 (2), [Ni2(L)(AcO)2(MeOH)]BPh4 (3), and [Zn2(L)(AcO)2]BPh4 (4), have been examined as regards their hydrolytic activity toward tris(p-nitrophenyl) phosphate (TNP) and hydrogen bis(p-nitrophenyl) phosphate (HBNP) by means of mass spectrometric methods as well as UV–visible spectroscopic methods. All the complexes hydrolyze TNP to BNP in the relative activity of 4 > 2 > 1 >> 3. It is found that one AcO group of [M2(L)(AcO)2]+ is replaced with BNP, arising from the hydrolysis of TNP, affording [M2(L)(AcO)(bnp)]+ in an equilibrium with [M2(L)(AcO)2]+: [M2(L)(AcO)2]+ + BNP [M2(L)(AcO)(bnp)]+ + AcO. In the reaction of HBNP with 14, [M2(L)(AcO)(bnp)]+ is produced in the equilibrium with [M2(L)(AcO)2]+, and the bound BNP is slowly hydrolyzed in the case of M = Mn and Co. The bound BNP of [Ni2(L)(AcO)(bnp)]+ is barely hydrolyzed and the bound BNP of [Zn2(L)(AcO)(bnp)]+ is practically not hydrolyzed. The relevance of the complexes to phosphotriesterase and phosphodiesterase is discussed.
  • Akira Ohashi, Hirobumi Hoshino, Junichi Niida, Hisanori Imura, Kousabu ...
    2005 Volume 78 Issue 10 Pages 1804-1809
    Published: 2005
    Released: October 04, 2005
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    The solubility of tris(pentane-2,4-dionato)chromium(III) (Cr(acac)3) in supercritical carbon dioxide (SC-CO2) with and without modifiers was investigated by UV–vis spectrophotometry. The influence of some polar and nonpolar modifiers, such as methanol, ethanol, 2,2,2-trifluoroethanol (TFE), acetone, chloroform, and benzene, was studied by changing the temperature, pressure, and concentration of the modifiers. Alcohols, particularly TFE, demonstrated a large solubility enhancement of Cr(acac)3 among these modifiers. In contrast, acetone having a relatively larger polarity gave a lower enhancement effect than chloroform and benzene. The measurement of the IR absorption spectra of TFE in the presence of Cr(acac)3 in SC-CO2 suggested that a drastic solubility enhancement of Cr(acac)3 upon the addition of TFE could be ascribed to the formation of the stable Cr(acac)3–TFE complex through hydrogen bonding. The association constants of Cr(acac)3 with TFE in SC-CO2 could be determined from the relationship of the solubility enhancement against the TFE concentration.
  • Hiroaki Matsumiya, Ryohei Ohkouchi, Masataka Hiraide
    2005 Volume 78 Issue 10 Pages 1810-1813
    Published: 2005
    Released: October 04, 2005
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    A series of 8-quinolinol derivatives has been examined as carriers for the collection of heavy metals with water-in-oil emulsion globules. The emulsion was prepared by dissolving 50 μmol of 8-quinolinol derivative and 30 mg of Span-80 (sorbitan monooleate) in 2.0 cm3 of toluene and vigorously mixing with 0.50 cm3 of 1.0 mol dm−3 hydrochloric acid by ultrasonic irradiation. The resulting emulsion was gradually injected into 25 cm3 of sample solution [containing 0.10 μg each of Fe(III), Co(II), Ni(II), Cu(II), Cd(II), and Pb(II)] at pH 4–8 and dispersed by stirring for 10 min as numerous tiny globules. When working with the parent compound, 8-quinolinol, Fe(III), Co(II), Ni(II), Cu(II), and Cd(II) were effectively transported through the toluene layer into the internal aqueous phase of the emulsion. However, Pb(II) was not transported at all. The derivatives of 5,7-dichloro-, 2-methyl-, and 5-octyloxymethyl-8-quinolinol were not useful for the simultaneous collection of the heavy metals. On the other hand, Kelex-100 (7-dodecenyl-8-quinolinol) allowed a nearly quantitative (more than 90%) collection of all the metals at pH 7–8. The effects of the substituents on the metal-collection efficiency are discussed in terms of the acidity and hydrophobicity of the carriers.
  • Rie Amase, Hitomi Shiraishi, Yuji Miyasato, Masaaki Ohba, Hisashi Okaw ...
    2005 Volume 78 Issue 10 Pages 1814-1820
    Published: 2005
    Released: October 04, 2005
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    Dinucleating compartmental ligands (2,6-bis{N-[(2-dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL1) and 2-{N-[(2-dimethylamino)ethyl]iminomethyl}-6-{N-methyl-N-[2-(dimethylamino)ethyl]aminomethyl}-4-methylphenol (HL2)) have afforded the following dinuclear nickel(II) complexes: [Ni2(L1)(OH)(py)(H2O)](ClO4)2·H2O (1), [Ni2(L2)(OH)(MeOH)(H2O)](ClO4)2·CH3CN (2), and [Ni2(L2)(OH)(dmf)2](ClO4)2 (3). X-ray crystallographic studies for 1 and 3 have clarified a μ-hydroxo-μ-phenolato dinuclear structure in a mixed-spin state with one pseudo octahedral Ni(II) (S = 1) and one planar Ni(II) (S = 0). The urea adducts, [Ni2(L1)(OH)(urea)(H2O)](ClO4)2·H2O (1′) and [Ni2(L2)(OH)(urea)(H2O)](ClO4)2 (2′), were prepared by the reaction of 1 and 2 with urea, respectively, and were structurally characterized to be in the mixed-spin state. The relevance of 1′ and 2′ to urease is discussed.
  • Kazuya Koumoto, Masami Mizu, Takahisa Anada, Takeshi Nagasaki, Seiji S ...
    2005 Volume 78 Issue 10 Pages 1821-1830
    Published: 2005
    Released: October 04, 2005
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    Schizophyllan is a natural β-(1 → 3)-D-glucan existing as a triple helix in water and as a single chain in dimethyl sulfoxide (DMSO), respectively. As we already reported, when a homo-polynucleotide is added to a schizophyllan solution, the single chain of schizophyllan forms a complex with the polynucleotide. One of the potential applications of this novel complex is an antisense-oligonucleotide (AS ODN) carrier. The present paper describes a modification technique that enables us to introduce a cholesterol group only to the side chain of schizophyllan. We prepared four cholesterol-appended schizophyllans with different modification levels. Using these compounds, we made complexes and carried out an in vitro antisense assay, administrating a phosphorothioate AS ODN to the several cell lines to depress their c-myb mRNA. When we used 2.2–2.3 mol % modified schizophyllan as the carrier, the antisense effect was most enhanced among others. The addition of β-cyclodextrin improved the complexation ability as well as the up-take for highly modified samples. Furthermore, the cytotoxicity for these modified schizophyllan samples was negligibly as small as the natural (unmodified) schizophyllan. The present work has thus clarified that schizophyllan can act as a new potential candidate for AS ODN carriers.
  • Kentaro Okuma, Toshiharu Izaki
    2005 Volume 78 Issue 10 Pages 1831-1833
    Published: 2005
    Released: October 04, 2005
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    The reaction of styrenes with triphenylphosphine in the presence of acid gave the corresponding 1-arylethylphosphonium salts in 76–82% yields. Indene also reacted with triphenylphosphine and tetrafluoroboric acid to afford 1-indanyltriphenylphosphonium tetrafluoroborate in 72% yield.
  • Mizue Fujio, Mai Uchida, Ayumi Okada, Md. Ashadul Alam, Ryoji Fujiyama ...
    2005 Volume 78 Issue 10 Pages 1834-1842
    Published: 2005
    Released: October 04, 2005
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    Solvolysis rates of 2-(aryldimethylsilyl)ethyl chlorides were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of aryl substituents at the silyl atom on the solvolysis rates at 50 °C were correlated with essentially nonresonant parameters of r = 0.10 in terms of Yukawa–Tsuno (Y–T) Eq. 1, giving a ρ value of −1.75. Such a high ρ value may be regarded as the effect of aryl ring on the bridged Si in the rate-determining step. The Si-bridging is consistent with the fact that the solvolysis of the unsubstituted substrate with d2-labeled ethylene moiety gave substitution products with label scrambling. The arylsilyl substituent effects were likewise analyzed for several relevant sets of β-silyl systems in order to ascertain significant variations of ρ values from system to system; Y–T Eq. 1 correlated quite excellently with essentially nonresonant sigmas of negligible resonance demand (r 0.10), to exhibit significant variations of ρ from −1.75 to −0.95.
  • Katsunori Tanaka, Marc Pimentel, Nina Berova, Koji Nakanishi
    2005 Volume 78 Issue 10 Pages 1843-1850
    Published: 2005
    Released: October 04, 2005
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    It has been found that nucleophilic reagents, i.e., NaBH4, Grignard reagents, and alkyl lithium, uniquely react with the α-alkoxy- or acyloxy-lactone moieties in ginkgolide and F-seco-ginkgolides to give rise to lactol derivatives. The reaction is rapid and stops at the lactol stage; the strong coordination of Na, Mg, and Li metals to the conformationally rigid cage structure is involved in both the initiation and termination stages. The NaBH4 reduction of F-seco-ginkgolides gives rise to an equilibrium mixture of α- and β-lactols, the separation of which becomes only possible after acylation by p-phenylbenzoic acid. The resulting acyl-lactol stereogenic centers were elucidated by both NOE and the CD/FDCD exciton chirality method utilizing the sterically hindered 7-hydroxyl. On the other hand, the alkylation of ginkgolide B derivatives proceeds regio- and stereoselectively at the C-11 lactone group, resulting from the approach of Grignard and alkyl lithium reagents to the convex face of the cage-shaped ginkgolide molecule. The additional new stereogenic centers of the quaternary lactol hydroxyls have been determined by NOE. This facile alkylation protocol gives rise to a deep-seated skeletal transformation of ginkgolides, resulting in a new class of ball-shaped heptacyclic ginkgolide derivatives via “olefin/olefin” and “olefin/alkyne” ring-closing metathesis.
  • Hiroshi Yamataka, Salai Cheettu Ammal, Tsutomu Asano, Yasushi Ohga
    2005 Volume 78 Issue 10 Pages 1851-1855
    Published: 2005
    Released: October 04, 2005
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    Thermal isomerizations at the C=N double bonds in R1R2C=NC6H4X proceed via an inversion mechanism, in which the C=NC6H4X bond angle is near 180° at the transition state (TS). Available experimental data on the reactions of (CF3)2C=NC6H4X and YC6H4CH=NC6H4X have suggested that the reaction mechanism changes with substituent X. In the present study, HF, B3LYP, and MP2 computations were carried out to analyze the modes of mechanistic change with the substituent for the reactions of (CF3)2C=NC6H4X, YC6H4CH=NC6H4X, and other systems. There are two possible pathways within the inversion mechanistic framework: a planar pathway with the R1R2C=N double-bond plane and the aromatic ring being coplanar at the TS and a perpendicular one with the two planes being perpendicular to each other at the TS. It was found that the mechanistic change is not due to a change in the relative importance of two independent and competitive reaction pathways, but arises from a change of the character of a single TS from planar to perpendicular geometry when the substituent becomes more electron-withdrawing.
  • Tetsuo Ohta, Masahiro Kamiya, Mami Nobutomo, Keisuke Kusui, Isao Furuk ...
    2005 Volume 78 Issue 10 Pages 1856-1861
    Published: 2005
    Released: October 04, 2005
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    Reductions of carboxylic acid derivatives by silanes in the presence of rhodium complexes were studied. Carboxylic esters were reduced to alcohols by diphenylsilane catalyzed by [RhCl(cod)]2/4PPh3 or [RhCl(PPh3)3] at room temperature in up to 99% yields. For example, ethyl decanoate and ethyl phenylacetate were converted to decanol and 2-phenylethanol in 98 and 92% yields, respectively. Carboxylic acids were also reduced by this reducing system to the corresponding alcohols in high yields. Furthermore, N-monosubstituted amides were reduced to secondary amines in moderate to good yields. For sterically hindered amides, the yields were moderate, and imines were produced in competitive yields.
  • Ryoko M. Uda, Keiichi Kimura
    2005 Volume 78 Issue 10 Pages 1862-1867
    Published: 2005
    Released: October 04, 2005
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    A Malachite Green derivative carrying a long alkyl chain has been designed to realize the photoinduced uptake of oily substances based on its photogenerated amphiphilicity. NMR spectroscopy was used to evaluate the solubility of benzene in cetyltrimethylammoium chloride solution with Malachite Green carrying a long alkyl chain. We found that UV irradiation drastically increased the solubility of benzene in the system of Malachite Green carrying a long alkyl chain. The results for the photoinduced solubilization are in good agreement with the photoionization ratio of Malachite Green carrying a long alkyl chain, which can play an important role in the control of molecular assemblies.
  • Daisuke Takeuchi, Kouhei Anada, Kohtaro Osakada
    2005 Volume 78 Issue 10 Pages 1868-1878
    Published: 2005
    Released: October 04, 2005
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    The cobalt and nickel complexes promote addition polymerization of substituted methylenecyclopropanes as well as their copolymerization with ethylene to afford the polymers that contain three-membered rings. The homopolymerization of 2-aryl-1-methylenecyclopropane catalyzed by [CoCl2(L)]–MMAO (L = bis(1-iminoalkyl)pyridine ligand) at −40 °C produces the polymers with a narrow molecular weight distribution. The copolymer of ethylene and 2-aryl-1-methylenecyclopropane is also obtained by using the same catalyst. The ratio of the two monomer units varies in the range from 0 to 0.5 depending on the concentration of ethylene and 2-aryl-1-methylenecyclopropane. 13C{1H} NMR spectrum of the alternating copolymer exhibits a single sharp signal for each carbon of the repeating units. Ethylene and 7-methylenebicyclo[4.1.0]heptane also undergo alternating copolymerization to produce the polymer having the C4 repeating unit containing a bicyclic group. Heating the polymer at 130 °C causes ring-opening isomerization to afford the polymer having a C=C double bond in the main chain. Mixtures of [Ni(π-C3H5)Br]2, a diimine ligand, and cocatalysts such as NaBARF and Et2AlCl, initiate the copolymerization of ethylene with 2-aryl-1-methylenecyclopropane to give a random copolymer with a low molecular weight (Mn = 1000–2000).
  • Cunman Zhang, Qian Liu, Zheng Xu, Keshu Wan
    2005 Volume 78 Issue 10 Pages 1879-1883
    Published: 2005
    Released: October 04, 2005
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    The thermal-degradation process of the mesoporous structure in silica MCM-41 was investigated in the present research via a series of thermal-stability experiments in different atmospheres with varied technique analysis (N2-sorption, XRD, IR, and NMR spectra). The research showed that the atmosphere was also a very important factor to affect the thermal stability of mesoporous silica as well as the temperature and time; the oxygen atmosphere obviously accelerated the degradation process of the ordered pore structure in mesoporous silica. We considered that the thermal vibration of atom groups, silanol condensation, and the reconstruction of bridge oxygen bonds between SiO4 tetrahedra in the mesopore wall can be the main causes resulting in the contraction of the inorganic networks and the degradation of the pore structure in mesoporous silica. The oxygen molecule could play an important role during the heat treatment. The oxygen can not only promote silanol condensation, but also make some original bridge oxygen bonds rupture more easily, and then the ruptured units immediately reconstruct more stable bonds with other ruptured units, SiO4, which results in the contraction of inorganic networks and degradation of the mesoporous structure.
  • Hotaka Yamamuro, Koji Koyanagi, Hiromichi Takahashi
    2005 Volume 78 Issue 10 Pages 1884-1886
    Published: 2005
    Released: October 04, 2005
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    The threadlike micelle of a cationic surfactant: cetyltrimethylammonium chloride (CTAC), containing anionic aromatic substances has been formed with unique rheological properties in strong electrolyte aqueous solutions and slurry using an inorganic powder such as cement. The threadlike micelle can be used as a high-efficiency viscosity agent for cement slurry.
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