Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
79 巻 , 4 号
選択された号の論文の22件中1~22を表示しています
Award Accounts
The Chemical Society of Japan Award for Young Chemists for 2004
  • Masayuki Inoue
    2006 年 79 巻 4 号 p. 501-510
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル フリー
    C-1027 is an extremely potent antitumor agent, and belongs to a family of chromoprotein antitumor antibiotics, which contain a carrier apoprotein and highly unstable enediyne chromophore. The enediyne spontaneously aromatizes to generate p-benzyne biradical, and subsequently abstracts hydrogens from the DNA sugar backbone, resulting in the sequence-selective double-strand cleavage. On the other hand, the C-1027 apoprotein functions as a carrier, and is likely to escort the reactive chromophore through the cells until reaching the target DNA. The excitement surrounding this molecule lies in the complex molecular architecture of the chromophore, the important biological activity, and the fascinating mode of action. In this account, our studies in the chemistry and biology of C-1027 are presented in three parts: (1) synthetic study of the C-1027 chromophore, (2) spin-trapping study of the C-1027-induced DNA cleavage, and (3) rational design of a kinetically stabilized analog of C-1027.
Accounts
  • Kimihisa Yamamoto, Takane Imaoka
    2006 年 79 巻 4 号 p. 511-526
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル フリー
    A series of novel dendrimers composed of dendritic phenylazomethines (DPAs) were synthesized with several types of functional cores. The metal assembling to the DPAs is stepwise by the layers, therefore, they can be used as a scaffold for the precise hybridization between metal ions and organic macromolecules. Because of uniform structure of the dendrimer, there is no structural dispersion in the macromolecule–metal hybrid of the DPAs. Also, the number of metal ions loaded in one dendrimer should have no statistical distribution in principle due to the precise metal assembling. A rigid π-conjugating backbone structure contributes not only to the stepwise metal assembly, but also to the solid-state stability under high temperature. Development of this property without any reduction in solubility in organic media enabled the easy preparation of homogeneous amorphous films in which the metal and macromolecule are precisely hybridized. As a result, the thin solid of the metal-assembling dendrimer acts as an excellent organic semiconductor in the hole-transport layer of a light-emitting diode. Metal-assembling DPAs also enhance the electron-transfer reaction as a protein-like catalyst. The DPA having a cobalt porphyrin core-could catalyze the CO2 reduction at an applied overpotential 1.1 V lower than that needed for the catalysis by a model compound of the porphyrin core (CoTPP). Reversible encapsulation/release of multiple irons is also demonstrated as a mimic of the iron storage protein (Ferritin). The switching between these two coordinating states can be completely controlled by the redox states of the iron (FeII/FeIII). The finding of these unique dendritic ligands will afford new insight into molecular design for finely controlled macromolecule–metal hybrid materials.
BCSJ Award Article
  • Tetsuro Kusamoto, Emiko Fujiwara, Akiko Kobayashi, Hengbo Cui, Takeo O ...
    2006 年 79 巻 4 号 p. 527-536
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル フリー
    Three BDT-TTP [2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene] salts, (BDT-TTP)3[MIICl4](EtOH)x (M = Co, Mn, and Zn; x ≈ 1.0) were prepared. These salts are almost isostructural to one another. The crystals are composed of BDT-TTP columns, “BDT-TTP tapes” that occupy the interstitial positions between BDT-TTP columns, [MIICl4]2− anions and the crystal solvents, respectively. These salts showed weakly metallic conducting behavior down to about 150 K. At low temperature, the resistivities increased gradually with decreasing temperature, but the systems retained fairly high conductivities even at around 30 K. The [ZnIICl4]2− salt indicated temperature independent paramagnetism down to low temperature. While the susceptibilities of the [CoIICl4]2− and [MnIICl4]2− salts showed the coexistence of π conduction electrons and localized high-spins of the magnetic CoII and MnII atoms, no significant π–d interaction was observed. Band structure calculations were performed with taking account of the possibility of inhomogeneous distribution of π electrons over the crystallographically independent three BDT-TTP molecules. The system has wide and narrow one-dimensional bands that originate from BDT-TTP columns and tapes, respectively. However, due to the interaction between BDT-TTP columns and tapes, the system gave a unique two-dimensional electronic band. The calculated energy dispersion curves were consistent with the weakly metallic behavior of the systems.
Articles
  • Shin-ichi Nagaoka, Umpei Nagashima, Joji Ohshita
    2006 年 79 巻 4 号 p. 537-548
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    電子付録
    A detailed examination of the relationship between chemical shifts in ESCA (electron spectroscopy for chemical analysis) and NMR (nuclear magnetic resonance) is presented for two silicon sites of bridged trichlorosilyl-trimethylsilyl molecules [Cl3Si–CnHm–Si(CH3)3 (n = 0–5 and m = 0–10)]. It is shown that the ESCA chemical shift of a silicon site mainly depends on the electronic environment within a mean radius of 1.168 Å of the nucleus and the NMR chemical shift depends on the electronic environment within a radius of more than 1.875 Å.
  • Hiroyuki Tajima, Kazuhiro Shimatani, Takeshi Komino, Masaki Matsuda, S ...
    2006 年 79 巻 4 号 p. 549-554
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    We fabricated biomolecular light-emitting diodes (BIODE) using hemin, and measured the electroluminescence (EL) spectra, current–voltage and EL intensity–voltage characteristics. The current–voltage and EL intensity–voltage characteristics revealed an irreversible transition of hemin for the applied voltage of V ≈ 4.5 V, above which drastic changes of the EL spectra occur. In order to clarify the origin of this voltage-induced transition, we determined the spin state of several compounds containing heme (hemin, myoglobin, and cytochrome c) using magnetic susceptibility and Raman spectra. We clarified the features of the EL spectra of heme compounds both in the oxidized low-spin state and in the oxidized high-spin state. Based on the spectral features thus obtained, we concluded that the voltage-induced transition in hemin is associated with the change of iron from the oxidized high-spin state (S = 5/2) to the oxidized low-spin state (S = 1/2).
  • Riadh Sahnoun, Yuichi Fujimura, Kuninobu Kabuto, Yoshio Takeuchi, Ryoj ...
    2006 年 79 巻 4 号 p. 555-560
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    We confirmed by both canonical molecular orbital analysis and the orbital deletion procedure (ODP) that a hyperconjugative electron-delocalization mechanism is the main factor controlling the conformational preference for cis and trans conformations of fluoroacetaldehyde (FAA) and methyl fluoroacetate (MFA). The quantitative analysis based on the ODP approach shows that the effects of hyperconjugation are more important in the cis conformation than in trans conformation.
  • Yusuke Fujii, Yasunori Tsukahara, Yuji Wada
    2006 年 79 巻 4 号 p. 561-568
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    Changes of the fluorescence spectra of tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and tetrakis(4-carboxyphenyl)porphyrin (TCPP) chemisorbed on TiO2 film in pH-adjusted water have been investigated. TPPS on TiO2 film in pH 6.5 water showed strong fluorescence, while it hardly emitted in pH 1.6 water, demonstrating a fluorescence switching with dramatic intensity changes in the TPPS–TiO2 system. On the other hand, only small changes in the fluorescence were observed for TCPP adsorbed on TiO2 instead of TPPS, although the changes were reversible. Fluorescence switching observed for TPPS and TCPP only in the adsorbed states on TiO2 are discussed on the basis of quenching of the excitation energy caused by molecular arrangements on TiO2 and photoinduced electron injection of excited porphyrin to TiO2.
  • Rajendra N. Goyal, Sham M. Sondhi, Anand M. Lahoti
    2006 年 79 巻 4 号 p. 569-576
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    Electrochemical behavior of a biologically active pyridinylpyrimidine derivative, 1-(3-hydroxy-2-pyridyl)-4,4,6-trimethyl-3,4-dihydropyrimidine-2[1H]-thione (1) has been investigated in aqueous phosphate buffers (1.9–10.6) at a pyrolytic graphite electrode (PGE). The oxidation occurred in a single well-defined oxidation peak, Ia, in the pH range 1.9–10.6. In the pH range 4.9–10.6, a reduction peak, IIc, was noticed in the reverse sweep that formed a quasi-reversible couple with peak IIa observed in the subsequent sweep towards positive potentials. The effect of concentration and sweep rate on peak potential and peak current of peak Ia established adsorption of 1 at the surface of PGE. Controlled potential coulometry experiments revealed the 5e oxidation of 1 in acidic solution and 7e oxidation in a neutral solution by an EC mechanism. UV–vis spectral and kinetic studies suggested formation of different intermediates in acidic and neutral media. The major product of oxidation at pH 2.7 was characterized as 2,2,4-trimethyl-2H-9-oxa-10-thia-1,4a,5-triazaphenanthrene 10,10-dioxide (6). At physiological pH 7.1, 1-(2,5-dioxo-6-pyridyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol (7a) and 1-(3,6-dioxo-3,6-dihydro-2-pyridyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-sulfonic acid (10) were identified as the oxidation products by GC-MS. A mechanism for the electrooxidation of 1 at PGE has also been suggested.
  • Wei Liu, Yuan Ma, Yingwu Yin, Yufen Zhao
    2006 年 79 巻 4 号 p. 577-579
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    The electrochemical cyanation of 1-arylpyrrolidines was carried out in methanol containing sodium cyanide at a platinum anode in a divided cell. The reaction gave the corresponding α-aminonitriles 2, together with the unexpected 1-arylpyrrolidine-2-carboximidic acid methyl esters 3 as byproducts.
  • Kazuhiko Ichikawa, Noriyuki Shimomura
    2006 年 79 巻 4 号 p. 580-587
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    The typical conclusions can be drawn as follows: (1) Since vaterite was only formed on calcium-binding poly(L-aspartate)-coated surface between 15 and 35 °C, the carbonic anhydrase (CA)-arising activity of zinc array (i.e., zinc-coordinated imidazolin-terminated silane monolayer, as shown in Chem. Eur. J. 2003, 9, 3235) prevailed the temperature influence on the polymorph of calcium carbonate. Time evolution of calcium carbonate formation was enhanced by the zinc array. (2) The calcium carbonate crystallized only on imidazolin- and sulfonate-terminated silane membranes has shown a number of microspheres of 1 μm more or less in diameter. (3) The higher temperature and higher pH induced aragonite formation at the sulfonate-terminated Nafion membrane in the presence of the above zinc array. (4) The observed morphology of aragonite or vaterite was similar to the spherulitic aragonite or vaterite formed by biological mineralization in marine organisms.
  • Shan Ji, Yanbei Zhu, Tomoki Yabutani, Akihide Itoh, Hiroki Haraguchi
    2006 年 79 巻 4 号 p. 588-594
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    The concentrations of major-to-ultratrace elements in bittern, which was obtained after seawater concentration in the salt preparation process, were investigated by ICP-AES (inductively coupled plasma atomic emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry) with and without the aid of chelating resin preconcentration. As a result, 34 elements in bittern could be determined in the concentration range from 107 to 10−3 ng mL−1 with good RSDs (less than 5%) for most analyte elements. Based on the experimental results, the concentrations of the elements in bittern were compared with those in seawater. Furthermore, the distribution factors of major-to-ultratrace elements in bittern were estimated to elucidate the partitionings of those elements among the calcium precipitate, the salt and the bittern from coastal seawater. The results suggest that the concentrations of the elements in bittern significantly depended on their chemical forms in seawater. For example, K and Mg in ionic form, V, Mo, W, and U in oxoanion form, and Cu and Zn in complex form with organic molecules in seawater, were much more partitioned in bittern than in salt.
  • Yuko Suetsugu, Yuko Mitsuka, Yuji Miyasato, Masaaki Ohba, Hisashi Okaw ...
    2006 年 79 巻 4 号 p. 595-601
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    The dinuclear copper(II) complex [Cu2(L1)](ClO4)2·CH3OH·2H2O (1) of a macrocyclic ligand H2L1, derived from the cyclic [2:2] condensation of 2,6-diformyl-4-methylphenol and 1,1,1-tri(aminomethyl)ethane, has been prepared as the type 3 copper site for modeling multicopper oxidase: 1 has two auxiliary amino groups on the macrocyclic framework. The condensation of 1 with two molecules of 2-formylpyridine through the amino groups afforded [Cu2(L2)](ClO4)2·2DMF (2). This has a Cu···Cu separation of 4.434(1) Å with no direct bridge between the two copper atoms, owing to the involvement of the auxiliary 2-pyridylmethylimino residue in coordination. The condensation of 1 with two molecules of 3-[N,N-di(2-pyridylmethyl)aminomethyl]-5-methylsalicylaldehyde in the presence of Cu(ClO4)2·6H2O afforded the tetracopper assembly complex [Cu4(L3)](ClO4)4·3H2O (3), which is comprised of a macrocyclic dinuclear Cu2(II,II) unit and two mononuclear Cu(II) units, {Cu(II)–Cu2(II,II)–Cu(II)}. Cyclic voltammograms of 3 exhibit a two-electron redox process at −0.77 V (vs Ag/Ag+) followed by two one-electron redox processes at −0.85 and −1.29 V. Coulometric studies combined with spectroscopic and EPR studies demonstrate that the redox process at −0.77 V involves the reduction of two mononuclear Cu(II) units followed by an intramolecular electron transfer from one of the reduced Cu(I) units to the dinuclear Cu2(II,II) unit: {Cu(II)–Cu2(II,II)–Cu(II)}/{Cu(I)–Cu2(II,II)–Cu(I)} → {Cu(I)–Cu2(I,II)–Cu(II)}. The resulting {Cu(I)–Cu2(I,II)–Cu(II)} species is further reduced to {Cu(I)–Cu2(I,II)–Cu(I)} at −0.85 V and to {Cu(I)–Cu2(I,I)–Cu(I)} at −1.29 V.
  • Naoko Mizuyama, Yoshinori Tominaga, Shinya Kohra, Kazuo Ueda, Shun-ich ...
    2006 年 79 巻 4 号 p. 602-611
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    電子付録
    The absorption and fluorescent properties of newly synthesized 5-aryl-2,2′-bipyridyls were examined both in solution and in the solid state. The 6-methoxy derivatives 5a5c have weak fluorescence, whereas 6-amino derivatives 7a7f showed strong fluorescence. Their spectroscopic properties were computationally analyzed using semi-empirical molecular orbital calculations. The geometries of the ground (S0) and the first singlet excitation states (S1) were optimized and employed to estimate the vertical transition energies. The drastic differences in fluorescent intensities between 5a5c and 7a7f can be qualitatively explained by the relative energy levels S1 and the neighboring triplet level; the energy gaps supposedly regulate the non-radiative intersystem crossing (ISC) probabilities. On the relaxed S1 geometry, 5a5c have quite small S1–triplet energy gaps, whereas 7a7f have no such quasi-degeneracies, leading to their quantitatively different quantum yields.
  • Hitoshi Miyasaka, Toru Izawa, Shinya Takaishi, Kunihisa Sugimoto, Ken- ...
    2006 年 79 巻 4 号 p. 612-620
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    Three diruthenium compounds, [Na(18-crown-6)(thf)2][Ru2(O2CCH3)2(t-Busalpy)2] (1), [K(18-crown-6)(thf)2][Ru2(O2CCH3)2(t-Busal-4-Mepy)2], (2), and [K(18-crown-6)(thf)(H2O)][K(18-crown-6)(thf)(MeO)][Ru2(O2CCH3)2(t-Busal-5-Mepy)2] (3) (18-crown-6 = 1,4,7,10,13,16-hexaoxocyclooctadecane; 18-crown-6-ether), have been synthesized by the ligand substitution reaction of Ru2(O2CCH3)4Cl with newly prepared tridentate bridging/chelating ligands, N-(2-pyridyl)-2-oxido-3,5-di-tert-butylbenzylaminato (t-Busalpy2−), N-(4-methyl-2-pyridyl)-2-oxido-3,5-di-tert-butylbenzylaminato (t-Busal-4-Mepy2−), and N-(5-methyl-2-pyridyl)-2-oxido-3,5-di-tert-butylbenzylaminato (t-Busal-5-Mepy2−), respectively, and isolated using [Na(18-crown-6)]+ or [K(18-crown-6)]+ as the counter cation. The structural features of the anionic parts are very similar to those of the previously synthesized family of [Ru2(O2CCH3)2(5-Rsalpy)2] (R = H, Me, Cl, Br, and NO2); two acetate and two t-Busal-R′py2− ligands are respectively located around the Ru2 unit in a trans fashion, where the t-Busal-R′py2− ligand acts as a tridentate ligand having both bridging and chelating characters to form the M–M bridging/axial-chelating mode. Their Ru–Ru bonded core with an electronic configuration of σ2π4δ2*δ*)3 is axial-capped by the di-t-butylphenolate groups of the t-Busal-R′py2− ligands, and experiences multi-redox properties: a one-electron reduction to Ru24+ and two one-electron oxidations to Ru26+ followed by Ru27+, in addition to t-Busal-R′py2− ligand-centered redox. The strong electron-donating ability of the t-butyl groups compared with the other R-groups leads to negative shifts of the redox potentials according to the Hammett law.
  • Osamu Enoki, Takane Imaoka, Kimihisa Yamamoto
    2006 年 79 巻 4 号 p. 621-626
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    A phenylazomethine dendrimer was developed for the one-step preparation of a platinum nanoparticle–carbon nanocomposite. The dendrimer formed a complex with platinum tetrachloride (PtCl4) in a chloroform–acetonitrile mixed solvent. The coordination behavior between the dendrimer and the platinum salts was confirmed by UV–vis and 1H NMR titration experiments. The obtained dendrimer–PtCl4 complexes were pyrolyzed under a nitrogen atmosphere at 1000 °C, and converted to spherical and dispersed platinum nanoparticles on a pyrolytic graphite identified by transmission electron microscopy (TEM). A high resolution TEM (HR-TEM) image of the products showed some lattice fringes attributed to the presence of Pt(111) in the particles, and X-ray photoelectron spectra (XPS) of the products corresponded to those of Pt(0). These results indicated that PtCl4 was perfectly converted to metallic platinum through this pyrolysis condition. Raman spectra showed that the dendrimer remained as an amorphous carbon after pyrolysis. The electrode modified with the product showed a catalytic activity for dioxygen reduction, which electrochemically confirmed that part of the carbon was porous enough to let the substrate go through and to reach the platinum surface.
  • Takashi Jobashi, Katsuya Maeyama, Keiichi Noguchi, Yasuhiko Yoshida, N ...
    2006 年 79 巻 4 号 p. 627-633
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    電子付録
    The R2O·BF3-mediated dehydrogenative crossed aldol condensation reaction of acyclic aliphatic ethers with benzaldehyde dimethyl acetal to give specifically indene derivatives or α,β-unsaturated carbonyl compounds has been found. When the ethers have bis(β-alkylethyl) ether structures, dehydrogenative formation of enol ether equivalents followed by successive crossed aldol addition to acetal-originated electrophile and intramolecular electrophilic aromatic substitution reactions give annulation products of 1-alkoxy-2-alkylindenes. When the ether has two β- and one or more α-hydrogens, α,β-unsaturated carbonyl compounds are obtained. The structural correlation between deuterated starting materials and the obtained products, the structural requirements for ethers, and the distinct substrate specificity have revealed the reaction routes and mechanisms.
  • Natsuki K. Kubota, Yuka Kobayashi, Hajime Iwamoto, Yoshimasa Fukazawa, ...
    2006 年 79 巻 4 号 p. 634-636
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    Two new halogenated briarane diterpenes, (−)-2-deacetyljunceellin (1) and (−)-3-deacetyljunceellin (2), and five known diterpenoids, junceellin, praelolide, junceellolide A, B, and D were isolated from the Papuan gorgonian coral Junceella fragilis. The structures of the new metabolites were determined by extensive 2D NMR experiments and by chemical conversion. The absolute configuration of 2 was determined through the 1H NMR study of the corresponding ester with a newly developed chiral auxiliary 3a.
  • Usman, Takeshi Kubota, Yasuaki Okamoto
    2006 年 79 巻 4 号 p. 637-643
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    The effect of boron addition was studied on the intrinsic activity of Al2O3-supported cobalt–molybdenum and cobalt–tungsten sulfide catalysts prepared by a CVD technique using [Co(CO)3NO] as a precursor of Co. The catalysts were characterized by means of NO adsorption and Raman spectroscopy. The intrinsic activity of the catalysts are discussed in terms of the turnover frequency (TOF) of the hydrodesulfurization of thiophene, calculated on the basis of the amount of the Co–Mo(W)–S phase. The intrinsic activity on the Co–Mo–S phase and the Co–W–S phase was increased by the addition of boron in a different way depending on the presulfidation temperature. The addition of a proper amount of boron weakened the interactions between molybdenum (tungsten) oxides and the Al2O3 surface, leading to an increase in the TOF on the Co–Mo–S phase and the Co–W–S phase by a factor of 1.6 and 1.3, respectively, when Mo(W)S2/Al2O3 was presulfided at 673 K. As for the catalyst presulfided at 773 K, the addition of boron increased the TOF on both CVD-Co/MoS2/B/Al2O3 and CVD-Co/WS2/B/Al2O3 by a factor of 1.9. A reverse correlation was observed between the strength of the molybdenum (tungsten) oxides–Al2O3 interactions and the intrinsic activity on the Co–Mo(W)–S phase.
  • Jia-Xing Zhou, Fung Fuh Wong, Chun-Yen Chen, Mou-Yung Yeh
    2006 年 79 巻 4 号 p. 644-648
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    電子付録
    Recently, 1,3,4-oxadiazole-based on heterocyclic compounds were investigated as electroluminescent materials. In this work, we first introduce 1,2,3-triazole to synthesize a series of 1,3,4-oxadiazole–1,2,3-triazole hybrids derivatives as potential electroluminescent materials and explore the effect of modification of the 1,2,3-triazole moiety. The λmax values of the UV–vis of 1,3,4-oxadiazole–1,2,3-triazole hybrids are promoted to longer wavelengths (340–350 nm) than the traditional 1,2,3-triazole derivatives (280–330 nm) in solutions and have a bathochromic shift to 350–360 nm in THF solution. The λmax values of the photoluminescence (PL) spectra are in the range 406–480 nm in solutions. Compound 7h evaporated to form films on quartz substrates, had a maximum at 455 nm and showed a red-shift (≈40 nm) with respect to the solution spectrum. The solution fluorescence quantum yields (Φf) were measured, all of which fell into the range 0.65–0.76, and were determined relative to that of 2-phenyl-5-(4-biphenyl)-1,3,4-oxadiazole in benzene (Φf = 0.80). 1,3,4-Oxadiazole–1,2,3-triazole hybrids derivatives show unclearly reversible reduction processes in cyclic voltammogram measurements. Following spectroscopic studies and observation of the electrochemical behaviors, 1,3,4-oxadiazole–1,2,3-triazole derivatives were determined to be highly potential efficient blue electroluminescent materials.
  • Satoshi Sato, Ryoji Takahashi, Toshiaki Sodesawa, Daiji Shin, Naoki Ic ...
    2006 年 79 巻 4 号 p. 649-655
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    SiO2-coated Al2O3 powders were prepared by depositing hydrolyzed tetraethoxysilane (TEOS) on Al(OH)3 and γ-Al2O3 at 40 °C. In the preparation using Al(OH)3 with a specific surface area (SA) of ca. 40 m2 g−1 as a support, loading of silica deposited on the Al(OH)3 was saturated at 80 mg galumina−1. Ammonium nitrate, a catalyst for the hydrolysis of TEOS, increased silica loading linearly with increasing the amount of TEOS charged, while the silica aggregated on the Al(OH)3. At temperatures of >300 °C, the core Al(OH)3 coated with aggregated silica was fragmented into a mixture of small particles of pure alumina and silica–alumina diminishing small particles with a large SA of >400 m2 g−1. The small surface area of the support Al(OH)3 is ineffective in generating active acid sites. In the deposition of silica on γ-Al2O3 with a SA of 450 m2 g−1, however, silica loading increased with increasing the amount of TEOS charged at 40 °C without using ammonium nitrate. Silicate species with thinner layer structures uniformly covered the γ-Al2O3 surface. The SiO2-covered γ-Al2O3 showed higher catalytic activity than the SiO2–Al2O3 prepared from Al(OH)3 did.
  • Shin’ichi Ishimaru, Maki Togawa, Ryuichi Ikeda, Tadashi Shimizu, ...
    2006 年 79 巻 4 号 p. 656-659
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    Measurements of complex impedance and 2H NMR spectra were performed on a layer silicate compound, Na-RUB-18 (sodium octosilicate, NaSi4O8(OH)·nH2O), to investigate hydrogen dynamics in crystals. A high proton conductivity amounting to ca. 10−1 S m−1 was observed at room temperature under 100% relative humidity. Activation energies of the proton conduction were estimated to be 125 and 18 kJ mol−1 below and above 290 K, respectively. 2H NMR spectra observed on a deuterated analog revealed 1-D proton conduction through hydrogen-bond networks formed among silanol groups on the layer surface and water molecules in the interlayer space. This material was discovered to be a new type of solid proton-conductor contributed by very weak acids in contrast to the strong-acid type ones so far reported.
  • Hiroshi Shimada, Naohisa Nishimura
    2006 年 79 巻 4 号 p. 660-662
    発行日: 2006年
    公開日: 2006/04/07
    ジャーナル 認証あり
    ZnCl2 supported on Mg/Al mixed oxides obtained through the thermal decomposition of hydrotalcite showed high catalytic activity in the benzylation of benzene with benzyl chloride at room temperature. The surface properties of hydrotalcite-derived mixed oxides suggested that they increased the catalytic activities of ZnCl2 owing to their high mesoporosity, with pore sizes in the vicinity of 10 nm.
feedback
Top