Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 72 , Issue 6
Showing 1-28 articles out of 28 articles from the selected issue
  • Hiroki Haraguchi
    Type: Accounts
    1999 Volume 72 Issue 6 Pages 1163-1186
    Published: 1999
    Released: May 01, 2004
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    The progress of modern analytical atomic spectrometry is briefly reviewed with emphasis on ICP-AES and ICP-MS; these provide some excellent analytical features such as high sensitivity, wide linear dynamic range, and multielement detection capability. Thus, the multielement determination of the major-to-ultratrace elements from % to sub-ppt (1 ppt = 10−12 g ml−1) level is possible for the biological, geochemical, and environmental samples. The standard or certified reference materials of plant, human blood serum, and the other biological samples were analyzed to establish the reliable analytical methods for the multielement determination by ICP-AES and ICP-MS. The modern analytical methods were applied to: (i) the correlation analysis of the elements in human blood serum, and (ii) the determination of rare earth elements in human blood serum on a personal basis. The speciation of trace elements in natural water was also carried out by the SEC (size exclusion chromatography)/UV absorption detection/ICP-MS combined system after ultrafiltration of the water samples. The SEC chromatograms indicated that most of trace elements in natural water existed as large organic molecule–metal complexes with the molecular weight of > 300000 and 10000—50000. In addition, trace elements in man and in the sea were discussed from the viewpoints of the geochemical classification of the elements on the earth, the Lewis’s acid-base theory, and the principle of HSAB (hard and soft acids and bases). Such multielement information allows the multielement profiling analyses of various samples to elucidate the elemental distributions, physicochemical characteristics, and behaviors of the major-to-ultratrace elements in relation with the biological functions or with the geochemical and environmental phenomena.
  • Tejraj M. Aminabhavi, Virupakshagouda B. Patil, Kamalika Banerjee, Ram ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1187-1195
    Published: 1999
    Released: May 01, 2004
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    Thermodynamic interactions in binary mixtures of styrene with n-alkanes have been studied in terms of excess quantities using the experimental results of density, viscosity, and speed of sound at 298.15 K. Flory as well as Prigogine–Flory–Patterson equations were used to calculate the excess molar volume in addition to enthalpy, entropy, and free-energy mixing functions. The viscosity results were analysed using Bloomfield and Dewan theory to predict viscosity deviations, while the speed-of-sound results were analysed by Benson and Kiyohara theory to predict the deviations in isentropic compressibility. The Prigogine–Saraga theory was used to calculate the deviations in internal pressure of liquids and liquid mixtures. Furthermore, isothermal compressibility values were predicted from the Flory equation of state and compared with the experimentally obtained values. Overall, the computed and experimental results are discussed in terms of thermodynamic interactions between the mixing components.
  • Kaoru Igarashi, Mitsuo Maeda, Takayuki Takao, Yuji Oki, Hideaki Kusama
    Type: Article
    1999 Volume 72 Issue 6 Pages 1197-1202
    Published: 1999
    Released: May 01, 2004
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    Rhodamine 6G/water/alcohol or carboxylic acid systems were studied. Rhodamine 6G molecules, which tend to associate into nonfluorescent dimers in aqueous solution, were prevented from dimerization by mixing them with organic compounds. It was found that additives with smaller dielectric constants prevented the dye molecules from associating to effectively form dimers. It was found that 2-butanol and isobutyric acid were the most effective additives for dissolving Rhodamine 6G dimer and that the amount demanded to obtain the necessary concentration of monomer in aqueous solution was less than 10%.
  • Hiroaki Kikuchi, Kazuhiko Seki, Satoru Kuwajima, Norimasa Okui
    Type: Article
    1999 Volume 72 Issue 6 Pages 1203-1211
    Published: 1999
    Released: May 01, 2004
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    A molecular dynamics (MD) trajectory of 1.0 ns duration has been computed for a methyl-terminated atactic poly(ethyl acrylate) using force field parameters which we determined by ab initio molecular-orbital calculations for small molecules (RHF/6-31G level). Local side chain motions were clarified by analyses of the MD trajectory. The torsional angle autocorrelation functions (TACF) were calculated for each dihedral angle in the side chain. All of the TACF were strongly non-exponential. The entire side chain rotation was an asymmetric 180° jump motion with a rapid torsional oscillation within stable and metastable conformations, while ethyl group motion around the O(non-carbonyl)–CH2 bond in the side chain was characterized by rapid torsional motion in the angle range from 60 to 300°involving an obscure three-site jump motion.
  • Noriko Okumura, Bunji Uno
    Type: Article
    1999 Volume 72 Issue 6 Pages 1213-1217
    Published: 1999
    Released: May 01, 2004
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    Electronic spectra of the active π-electronic dianion of 1,4-benzoquinone and its hydrogen-bonded complex with CH3OH, generated at sequential electroreduction steps, have been discussed from the points of view of the observation techniques and n–σ charge-transfer interaction of the dianion with a weak hydrogen donor. An improved method involving rapid circulation of the electrolyzed solution via a photodiode array detector to avoid comproportionation and side reactions was used for successful measurements of the clear spectra resulting from the dianion generation. CNDO/S-CI calculations well reproduced the longest-wavelength band observed for the dianion, assigning to the benzenoid 1B3u1Ag band under D2h symmetry. The hydrogen-bonding interaction of the 1,4-benzoquinone dianion with CH3OH allows the 1B3u1Ag band to be blue-shifted. This behavior has been well explained in terms of the strong n–σ type charge-transfer interaction of the dianion with CH3OH. These results have been extensively discussed with regard to coupled electron and proton transfer reactions in the quinone–hydroquinone redox system.
  • Toshiyuki Fujii, Jun Inagawa, Kazushige Nishizawa
    Type: Article
    1999 Volume 72 Issue 6 Pages 1219-1223
    Published: 1999
    Released: May 01, 2004
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    Molybdenum isotopes were fractionated in a liquid–liquid extraction system using dicyclohexano-18-crown-6 (DC18C6). The enrichment factors showed a breakdown of the conventional mass-dependent rule. Some unusual and larger isotope effects were observed in the even atomic mass isotopes, 92Mo and 94Mo. The unusual features in the present study were not responsible for the field shift effect, which was regarded as a primary factor of the anomalous isotope effect in the recent theory, but were due to an anomaly on the vibrational levels. The largest isotope effect was observed in the isotope pair of 94Mo–96Mo, it was ε96,94 = 0.0086 ± 0.0007, its initial aqueous phase was 0.91 M molybdenum chloride, and its organic phase was 0.2 M DC18C6 in chloroform: this was 0.0043 ± 0.0004 in terms of the enrichment factor for unit mass difference.
  • Hirohiko Kono, Isao Kawata, Nobuhiro Ohta
    Type: Article
    1999 Volume 72 Issue 6 Pages 1225-1231
    Published: 1999
    Released: May 01, 2004
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    The v th frequency derivative of the Fourier spectrum obtained by the use of tv-windows is proposed with some applications to practical examples. Derivative power spectra have higher resolution and lower base lines than conventional spectra (e.g., v = 0), and are insensitive to the choice of the beginning of the acquisition duration. For extremely large v, the spectrum is not resolved well. The optimal value of v is determined so that the main body of the product of the window tv and the signal is accommodated in the range where the S/N ratio is relatively high. This criterion is successfully applied to a signal generated from a known spectrum and to fluorescence quantum beats in pyrimidine at zero and nonzero magnetic fields.
  • Kenichi Nakashima, Yoshinori Fujimoto, Takayuki Anzai, Jian Dong, Hide ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1233-1238
    Published: 1999
    Released: May 01, 2004
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    Fluorescence and FTIR spectroscopy have been used to investigate the pH-dependent conformational change of poly(methacrylic acid) (PMA) in aqueous solutions. Fluorescence intensity and lifetime, and other fluorescence parameters of the 1-pyrenemethanol probe were measured as a function of pH in PMA aqueous solutions. The fluorescence data obtained show that PMA undergoes a sharp coiling ↔ uncoiling change around pH 5. FTIR spectra of PMA were successfully observed by an attenuated total reflection technique. The FTIR data show that the carboxyl groups of PMA are ionized progressively over the wide pH range from 3 to 8, and that PMA takes an expanded conformation under basic conditions. These results make it clear that although the ionization of the carboxyl groups takes place progressively, the conformational change of PMA is brought about abruptly.
  • Toshio Akai, Masami Okuda, Masaharu Nomura
    Type: Article
    1999 Volume 72 Issue 6 Pages 1239-1246
    Published: 1999
    Released: May 01, 2004
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    X-Ray absorption fine structure (XAFS) studies were performed for cobalt(II) bromo complexes prepared for the ratio Br/Co from 0.0 to 4.0 and for their oxidized complexes with ozone in acetic acid solvent. The multivariate curve resolution method indicates the existence of two kinds of chemical species both before and after the oxidation. Before oxidation, the two species are cobalt(II) acetate and tetrahedral cobalt(II) complex coordinated by Br. The oxidized sample with ozone consists of cobalt(II) acetate and trinuclear cobalt(III) complex; however, cobalt(III) complexes including Br are not detected. The rate of the change from the cobalt(II) complex coordinated by Br to the trinuclear cobalt(III) complex is lower than that from cobalt(II) acetate complex. This indicates that the tetrahedral cobalt(II) complex coordinated by Br is more difficult to be oxidized than the octahedral cobalt(II) acetate complex.
  • Yoshiharu Mukouyama, Hayato Hommura, Shuji Nakanishi, Takashi Nishimur ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1247-1254
    Published: 1999
    Released: May 01, 2004
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    Mechanisms of electrochemical current oscillations of two types, named oscillation A and B, both observed for the H2O2-reduction reaction on Pt electrodes in acidic solutions, have been studied experimentally and by mathematical simulation. Oscillation A appears in a potential region just before hydrogen evolution, while oscillation B appears in a region of hydrogen evolution. A phase diagram we obtained has shown that oscillations A and B appear in limited ranges of the H+ and H2O2 concentrations and their ratio. The oscillation period for oscillation A increases with decreasing H2O2 concentration and negative shift of the electrode potential, mainly determined by the current density in the low-current state. Mathematical simulation by taking account of all plausible interfacial reactions (H2O2 reduction, hydrogen adsorption, and hydrogen evolution) reproduces the essential features of oscillation A, but does not reproduce oscillation B. It is shown that a positive feedback mechanism works in sudden transitions between the high- and low-current states for oscillation A.
  • Mahmut Abla, Takakazu Yamamoto
    Type: Article
    1999 Volume 72 Issue 6 Pages 1255-1261
    Published: 1999
    Released: May 01, 2004
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    Ligand exchange reactions of bis(1,5-cyclooctadiene)nickel(0), Ni(cod)2, with bpy, DMbpy, and TMbpy (bpy = 2,2′-bipyridine, DMbpy = 4,4′-dimethyl-2,2′-bipyridine, TMbpy = 4,4′,5,5′-tetramethyl-2,2′-bipyridine) in THF and DMF have been investigated kinetically. The reaction obeys the pseudo first-order kinetics, R = −d[Ni(cod)2]/dt = kobs[Ni(cod)2], with respect to the concentration of Ni(cod)2 in both the solutions. In THF, the kobs value linearly increases with [L] at a low concentration region of the exchanging ligand L; but it levels off at high concentrations of L and approaches a limiting value (e.g., about 1.0 × 10−4 s−1 at 25 °C). Addition of cod to the THF solution accelerates the exchange reaction. On the other hand, in DMF, the rate of the reaction (R) obeys the second-order rate law, R = k[Ni(cod)2][L], over a wide range of [L]. In DMF, the k value is independent of the concentration of cod added. Based on the kinetic results and NMR analysis, a reaction mechanism involving coordination of bpy, cod, or DMF to Ni(cod)2 to form a 20 e intermediate complex is proposed. DMbpy and TMbpy have a reactivity comparable to that of bpy in THF. In DMF, their reactivity increases in the order of bpy < DMbpy < TMbpy at 25 °C.
  • Nagao Kobayashi, Ryuji Higashi, Kazuyuki Ishii, Kazuaki Hatsusaka, Kaz ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1263-1271
    Published: 1999
    Released: May 01, 2004
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    Zinc and metal-free amphiphilic phthalocyanines (pcs) substituted by four or eight tri(ethylene oxide) chains (3,6,9-trioxadecyloxy groups) {(H2(4EGpc), [Zn(4EGpc)], H2(8EGpc), and [Zn(8EGpc)] in Fig. 1)} have been prepared in order to study their aggregation in water, dioxane, and dioxane/water mixtures, their complexation phenomena with guest molecules in benzene, and mesomorphism in the neat state. In particular, tetra-substituted pcs have C4h symmetry and do not contain other positional isomers. [Zn(8EGpc)] forms aggregates in water and water–organic solvent mixtures; the extent of this was examined by electronic absorption and fluorescence spectroscopy. 1H NMR and fluorescence spectroscopy indicated that H2- and [Zn(8EGpc)] form inclusion complexes with quinones in benzene via hydrogen bonding. Benzoquinones with more hydroxy groups form complexes more effectively, plausibly laterally outside of the pc plane. From the higher field shift of the 1H singals of 2,2′-dihydroxy-1,1′-binaphthyl (BINAP) in the presence of [Zn(8EGpc)], BINAP molecules were suggested to lie above or below the pc plane. The mesomorphism of H2(8EGpc), [Zn(4EGpc)], and H2(4EGpc) was studied. In the case of H2(8EGpc), the discotic hexagonal ordered columnar (Dho) phase was seen in the range of from room temperature to 265 °C. However, liquid-crystalline phases were not observed for H2(4EGpc) and [Zn(4EGpc)].
  • Hirotaka Nagao, Noriharu Nagao, Yasuhiko Yukawa, Dai Ooyama, Yoshinobu ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1273-1284
    Published: 1999
    Released: May 01, 2004
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    The reaction between cis-[Ru(NO)(H2O)(bpy)2]3+ ({RuNO}6) and formic acid gives [{Ru(μ-NO)}2(bpy)4]2+ (2) ({RuNO}8–{RuNO}8), along with some other products species: cis-[Ru(NO)(OCHO)(bpy)2]2+ (1)({RuNO}6), and cis-[Ru(OCHO)(H2O)(bpy)2]+. The μ-nitrosyl complex (2) consists of two cis-Ru(bpy)2fragments connected by two formally negatively charged bridging nitrosyl ligands. Electrochemical study of the complex shows that two successive one-electron oxidation waves to give [{Ru(μ-NO)}2(bpy)4]4+({RuNO}7–{RuNO}7) are found. The generated two-electron oxidation species is disintegrated to afford a one-electron reduction species, cis-[Ru(NO·)(CH3CN)(bpy)2]2+ ({RuNO}7), along with a small amount of an unexpected nitro species, cis-[Ru(NO2)(CH3CN)(bpy)2]+. The characteristics of electrochemically generated one-electron reduction species cis-[Ru(NO·)X(bpy)2](n−1)+ ({RuNO}7) (X = H2O, OCHO) are investigated in the connection. During the degradation process of the one-electron reduction species, a nitrosyl-to-nitro conversion was found to proceed in cis-[Ru(NO·)(H2O)(bpy)2]2+, via the formation of cis-[Ru(NO·) (CH3CN)(bpy)2]2+ mentioned above; this is the first observation which explains the electrochemically-induced nitrosyl-to-nitro conversion observed in the reduction process of {RuNO}6-type complexes.
  • Yasuki Yoshimura
    Type: Article
    1999 Volume 72 Issue 6 Pages 1285-1292
    Published: 1999
    Released: May 01, 2004
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    An interaction of NaBr, NH4Br, Me4NBr, Et4NBr, Pr4NBr, Bu4NBr, and NaBPh4 with mer-(+)-tris(L-alaninato)cobalt(III) (mer-(+)-[Co(L-ala)3]) was examined by estimating the standard enthalpy (ΔHtr°) and entropy of transfer (ΔStr°) of mer-(+)-[Co(L-ala)3] from water to the salt solutions on the basis of the temperature dependence of solubility. A difference in correlation between ΔHtr° and TΔStr° demonstrated that while NaBr and NH4NBr increase the solubility of mer-(+)-[Co(L-ala)3] by hydrophilic interaction, Pr4NBr, Bu4NBr, and NaBPh4 increase the solubility of mer-(+)-[Co(L-ala)3] by hydrophobic interaction. On the basis of this finding, ΔHtr° and TΔStr° of the transfer from water to aqueous Bu4NBr solution for the mer-tris(aniono)cobalt(III) of glycine (glyH), L-alanine (alaH), L-serine (serH), DL-2-aminobutylic acid (abaH), DL-norvaline (nvalH), L-valine (valH), and L-leucine (leuH) led to the conclusion that hydrophobicity of the amino acids increases in the order of glyH < serH < alaH < abaH < nvalH < valH < leuH. This conclusion is compared with the hydrophobicity order reported in the literature.
  • Masaru Kimura, Yuko Shiota, Shinobu Kishi, Keiichi Tsukahara
    Type: Article
    1999 Volume 72 Issue 6 Pages 1293-1299
    Published: 1999
    Released: May 01, 2004
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    The hexacyanoferrate(II) ion ([Fe(CN)6]4−) was rapidly oxidized to [Fe(CN)6]3− by a radical anion, I2−·, which was formed by a reaction between the copper(II) ion and the iodide ion. The oxidation reaction was accelerated by increasing the pH. Under the conditions of lower pH’s, the [Fe(CN)6]3− acted as a retarder to the oxidation reaction. The mechanisms for such reactions are discussed in terms of accounting for the obtained results.
  • Ludovick C. Manege, Toshio Takayanagi, Mitsuko Oshima, Tadashi Iwachid ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1301-1306
    Published: 1999
    Released: May 01, 2004
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    Complex formation constants of six crown ethers, benzo-12-crown-4, benzo-15-crown-5, benzo-18-crown-6, dibenzo-18-crown-6, dibenzo-21-crown-7, and dibenzo-24-crown-8 (B12C4, B15C5, B18C6, DB18C6, DB21C7, and DB24C8, respectively) with alkali and alkaline earth metal cations have been measured in aqueous solutions by capillary zone electrophoresis. The procedure involved the measurement of change in the electrophoretic mobility of the ligands upon increasing the metal ion concentration in the carrier electrolyte solution. A substantial increase in apparent electrophoretic mobility was observed for the crown ethers with increasing concentrations of the metal ions. The variations in increased electrophoretic mobility were attributed to the different stability of the complexes formed between the cations and the crown ether. The complex formation constants obtained with alkali metal cations were in the orders of: K+ > Na+ > Rb+ > Cs+ (B18C6), K+ > Na+ > Rb+ > Cs+ (DB18C6), Rb+ > Cs+ > K+ (DB21C7), and Rb+ > Cs+ (DB24C8); while with alkaline earth metal cations it was: Ba2+ > Sr2+ > Ca2+ (B18C6) and Ba2+ > Sr2+ (DB18C6). All the ligands examined showed no change in their apparent electrophoretic mobility upon changing Li+ and Mg2+ concentrations, indicating less reactivity with the cations. From the results obtained in this study, the electrophoretic method was proved to be preferable for analyzing the reactivity of the crown ethers and the selectivity toward metal cations.
  • Hiroyuki Noda, Hiroaki Ohya, Hitoshi Kamada
    Type: Article
    1999 Volume 72 Issue 6 Pages 1307-1311
    Published: 1999
    Released: May 01, 2004
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    The objective of our research was to establish control of biological functions by the illumination of a photosensitizer of hematoporphyrin that was externally provided in a biological system. We found using an ESR method that the reduction of 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPOL), as a reduction probe, caused by enzyme reactions can be controlled through the photoexcitation of hematoporphyrin adsorbed on the living yeast cells (HP/Yeast system). On the basis of the effects of some electron-transfer blockers through its reduction rate, it has been postulated that the reduction of TEMPOL is mainly conducted through ferredoxin (ferredoxin-NAD(P)+ reductase), which could be controlled through the illumination of HP connected with a mitochondrial electron-transfer system. A possible mechanism for controlling the reduction of TEMPOL is discussed in connection with the energy levels of HP and the redox potentials of the components in yeast cell participating in this phenomenon.
  • Shin Sakai, Yoshihiro Shigemasa, Tomikazu Sasaki
    Type: Article
    1999 Volume 72 Issue 6 Pages 1313-1319
    Published: 1999
    Released: May 01, 2004
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    A novel metal-assisted assembly of mulitivalent carbohydrate ligands is described. A bipyridine-modified N-acetylgalactosamine (bipy-GalNAc) undergoes Fe(II)-induced self-association to form a trimeric GalNAc ligand (FeII(bipy-GalNAc)3). The synthetic GalNAc cluster strongly binds to Vicia villosa B4 lectin and Glycin Max lectin, which recognizes multiple GalNAc residues. The trimeric GalNAc ligand is formed as a mixture of four diastereomeric isomers: Δ-fac, Λ-fac, Δ-mer, and Λ-mer. These stereoisomers are in a dynamic equilibrium at room temperature. The equilibrium allows the spatial arrangement of the three GalNAc residues to change in order to fit into a multivalent carbohydrate binding site of the lectins. Detailed analysis of the kinetic and thermodynamic data for the isomerization can provide structural information of the carbohydrate binding site of the lectins.
  • Toshiya Sasaki, Hideo Kise
    Type: Article
    1999 Volume 72 Issue 6 Pages 1321-1325
    Published: 1999
    Released: May 01, 2004
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    The catalytic activity and circular dichroic (CD) spectra of α-chymotrypsin (CT) were measured in ethanol/water (95/5, v/v) solution containing small amounts of metal salts. Although the catalytic activity of CT increased upon the addition of all the metal salts used, the magnitude of activity increase was different for different metal salts. Especially, calcium acetate accelerated the transesterification of amino acid up to 6 fold at 100 μM. The secondary and tertiary structures of CT were also changed by metal salts, as studied by CD measurements. The effects of metal salts on the stability of CT in ethanol/water were also studied, and it was found that the residual activity of CT after 7 days in ethanol/water in the presence of Ca(OCOCH3)2 was about 20% of the initial activity. The change in activity was closely correlated with the change in the mean residue ellipticity of CT at 208 or 230 nm.
  • Haruhiko Tomoda, Takafumi Hirano, Shojiro Saito, Toshiki Mutai, Koji A ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1327-1334
    Published: 1999
    Released: May 01, 2004
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    In order to search for novel fluorescent organic compounds, 20 derivatives of imidazo[1,2-a]pyridine (1) were synthesized, and their fluorescent properties were studied. Though the parent compound 1 (λfl = 370.5 nm, Φ = 0.57 in ethanol) was in the liquid state at ambient temperature, 2-phenylimidazo[1,2-a]pyridine (5), 2-(2-naphthyl)imidazo[1,2-a]pyridine (16), 7-methylimidazo[1,2-a]pyridine (3), 7-methyl-2-phenylimidazo[1,2-a]pyridine (12), and 7-methyl-2-(2-naphthyl)imidazo[1,2-a]pyridine (17) were found to give thermally stable solid compounds (mp 55—190 °C) without much affecting the fluorescent properties of the parent compound (λfl = 374—381 nm, Φ = 0.50—0.78 in ethanol). Among the 4′-substituted 2-phenyl derivatives, it was found that the introduction of the strong electron-donating amino and dimethylamino groups (2-(4-aminophenyl)imidazo[1,2-a]pyridine (7) and 2-[4-(dimethylamino)phenyl]imidazo[1,2-a]pyridine (8), respectively) caused marked red shift of their fluorescence (λfl = 445 and 446 nm, respectively, in ethanol), thus providing the way for tuning the fluorescence color of the IP derivatives. The observed red shift of the fluorescence of 7 and 8 was ascribed to the contribution of the excited intramolecular charge transfer state.
  • Kazunori Kamijo, Akihiko Otoguro, Kozo Toyota, Masaaki Yoshifuji
    Type: Article
    1999 Volume 72 Issue 6 Pages 1335-1342
    Published: 1999
    Released: May 01, 2004
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    Stabilized thioxophosphine sulfides bearing the 4-t-butyl-2,6-bis(dialkylaminomethyl)phenyl or the 2,4-di-t-butyl-6-(dialkylaminomethyl)phenyl group, as well as their 15N labeled analogs, were prepared. Intramolecular interaction between the nitrogen and the phosphorus atoms was investigated, mainly by means of 31P NMR and 1H NMR spectroscopic studies.
  • Michinori Oki, Hiroshi Ikeda, Shinji Toyota
    Type: Article
    1999 Volume 72 Issue 6 Pages 1343-1349
    Published: 1999
    Released: May 01, 2004
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    The title compound was prepared by treating 4,4,5,5-tetramethyl-1,3-dioxolan-2-yl acetate with cesium fluoride. Rates of ionization of this compound were determined in various solvents by the dynamic NMR technique. While effects due to polarity as well as solvent molecular size were observed in many solvents examined, the rates in solutions of which the solvent is capable of being an acceptor in hydrogen-bond formation with the substrate were unusually small, and this effect is diminished in bulky solvents. Such results are attributed to stabilization of the original state due to hydrogen-bond formation with the acidic C(2) – H group of the substrate in those solvents. The hydrogen-bond formation is hindered by the steric effects in bulkier solvents than in smaller solvents. The rates of contact ion pair and solvent-separated ion pair formations should be independently determined in 2-fluoro-4,4,5,5-tetramethyl-1,3-dioxolane, but so far no clear example which shows that the rate-limiting step is the solvent intervention has been found, even though various bulky solvents were examined.
  • Masato Ushiyama, Atsushi Yoshino, Takeshi Yamamura, Yasuo Shida, Fumio ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1351-1364
    Published: 1999
    Released: May 01, 2004
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    We succeeded in combining multiple-histidine peptides with porphyrins; that is to say, we synthesized three peptide porphyrins consisting of α4-meso-tetrakis(o-aminophenyl)porphyrin, α4-H2TAPP, and amphiphilic peptide, α4-(PepA18)n(AG)4−n-H2TAPP (n = 1, 3, and 4; PepA18 = EEALEKHEKALEKHEKAG), in the liquid phase. These compounds were designed to construct multiple porphyrin systems; in other words, each peptide attached on the H2TAPP was designed to contain two histidines. The stability of the porphyrins, (AG)4-H2TAPP and (AG)1(Boc-AG)3-H2TAPP, as well as the coupling conditions between the porphyrin fragments and the 16-residue peptide, EEALEKHEKALEKHEK, to give α4-(PepA18)n(AG)4−n-H2TAPP (n = 1, 3, and 4) were studied in detail with respect to the temperature, solvents, coupling reagents, additives, and amines. This search revealed that the combination of DMF/benzotriazol-1-yl-oxy-tris(pyrrolidino)phosphonium hexafluorophosphate (PyBOP)/N,N-diisopropylethylamine is suitable for the purpose. The search also clarified that it is possible to synthesize α4-(PepA18)4-H2TAPP and α4-(PepA18)3(AG)1-H2TAPP selectively by choosing the coupling additives 1-hydroxy-7-azabenzotriazole (HOAt) and 1-hydroxybenzotriazole (HOBt), respectively.
    All of the compounds showed 40% helicity in a solution (phospate buffer, pH = 7.0) containing 2,2,2-trifluoroethanol (TFE). The UV-vis and circular-dichroism spectrophotometric titrations of Fe(III) protoporphyrin IX chloride, B, with α4-(PepA18)4-ZnTAPP, A, indicated that up to three equivalents of B were incorporated into A in a buffer solution containing 15% TFE. Sedimentation-equilibrium ultracentrifugation experiments showed that A is a dimer in the solution, and that this dimer is transformed to a trimer when B is incorporated into A. These results suggest that A achieves a 12-porphyrin system consisting of different kinds of metalloporphyrin.
  • Hidemitsu Uno, Nobumasa Nibu, Noboru Misobe
    Type: Article
    1999 Volume 72 Issue 6 Pages 1365-1375
    Published: 1999
    Released: May 01, 2004
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    The coupling reaction of perfluoroalkylated 2-aryl-1,1-dibromoalkenes using zinc and copper(I) bromide gave stereoisomeric mixtures of [3]cumulenes and [4]radialenes. The ratio of [3]cumulenes and [4]radialenes mainly depended upon the reaction temperature and the electronic character of the aryl group. When the coupling reaction was carried out at −40 °C, (E)- and (Z)-[3]cumulenes were obtained in good selectivity and only trace amounts of [4]radialenes were detected by a 19F NMR analysis. On the other hand, a similar reaction at −60 °C afforded a considerable amount of [4]radialene isomers. When the cis-[3]cumulenes were heated at an appropriate temperature, selective isomerization to trans-[3]cumulenes occurred.
  • Wen-Chi Liu, Masato Oikawa, Koichi Fukase, Yasuo Suda, Shoichi Kusumot ...
    Type: Article
    1999 Volume 72 Issue 6 Pages 1377-1385
    Published: 1999
    Released: May 01, 2004
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    Lipid A and its two chemically stable analogues, wherein the glycosidic phosphoryl groups in lipid A is replaced with 2-(phosphonooxy)ethyl or carboxymethyl groups, have been synthesized by an improved and divergent route via a common allyl glycoside intermediate in which the 4-hydroxy group was protected as a benzyl ether. The total yields were more than 20% for 11 or 12 steps starting from allyl 4,6-O-benzylidene-2-deoxy-2-(trichloroethoxycarbonylamino)-D-glucopyranoside. These synthetic chemically stable analogues induce interleukin-6 and tumor necrosis factor α in human peripheral whole blood cells with potencies comparable to those by natural-type synthetic lipid A. The Limulus activities of both analogues were found to be even stronger than the activity of the natural-type one.
  • Masato Nanjo, Akira Sekiguchi, Hideki Sakurai
    Type: Article
    1999 Volume 72 Issue 6 Pages 1387-1393
    Published: 1999
    Released: May 01, 2004
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    The molecular structures of lithiopentamethyldisilane ([LiSiMe2SiMe3]4, 1a), 2-lithio-1,1,2,3,3-pentamethyl-1,3-diphenyltrisilane ([LiSi(SiMe2Ph)2Me]2, 1b), and 2-lithio-1,1,1,3,3,3-hexamethyl-2-phenyltrisilane ([LiSi(SiMe3)2Ph]2, 1c) have been determined by X-ray diffraction. The silyllithium 1a is a tetramer in the solid state with intramolecular Li···CH3 agostic interactions. The silyllithiums 1b and 1c are dimers with intramolecular lithium-phenyl interactions. The latter adopts a molecular structure with not only an intramolecular Li–Ph interaction, but also an intermolecular Li···CH3 agostic interaction. The structures of these organometallic derivatives show novel features not observed in solvent-coordinated lithiosilanes. These features provide valuable insights into structures that differ markedly from those of lithiosilanes containing coordinated donor solvent molecules.
  • Koji Kuruma, Hiro-o Nakagawa, Tatsuro Imakubo, Keiji Kobayashi
    Type: Article
    1999 Volume 72 Issue 6 Pages 1395-1401
    Published: 1999
    Released: May 01, 2004
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    The host compound 2,5-bis(9-hydroxyfluoren-9-yl)thieno[3,2-b]thiophene (1) afforded clathrate crystals represented by the formula (1)(guest)2 for the guests EtOH, n-PrOH, and i-PrOH. Their X-ray crystal analyses revealed that the host frameworks are isostructural. The guest molecules, which are embedded in a channel-type of host void, were exchanged with other guest species by vapor contact. Upon exposure of these crystals to methanol vapor, guest elimination was induced to give the guest-free host 1 crystal [β-form, P1-, a = 13.111(4), b = 13.724(3), c = 9.766(3) Å, α = 97.11(2), β = 98.64(3), γ = 64.56(2)°, V = 1565.3(8) Å3]. The crystal thus obtained is a polymorphic form of the guest-free 1 crystal which is obtained by recrystallization from dichloromethane [α-form, P21/n, a = 17.403(3), b = 20.654(4), c = 8.695(1) Å, β = 99.73(1)°, V = 3080.4(9) Å3]. Once the guest molecules have been lost, gas-sorptive enclathration was not accomplished for either of these polymorphic host crystals; host 1 does not act as an apohost.
  • Naobumi Motohira, Takahiro Takai, Nobuyuki Kamiya, Ken-ichiro Ota
    Type: Article
    1999 Volume 72 Issue 6 Pages 1403-1407
    Published: 1999
    Released: May 01, 2004
    JOURNALS RESTRICTED ACCESS
    The oxidation behavior of Ni in molten carbonate was evaluated by chronopotentiometry. The oxidation of Ni in molten carbonate proceeded in a two-step reaction. The first step of oxidation was independent of the specimens’ nature and depended on PCO2. On the other hand, the second step of oxidation depended on the batch of the specimens, and was independent of PCO2. The corrosion product in both oxidation processes was divalent Ni oxide, namely NiO.
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