Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 80 , Issue 11
Showing 1-23 articles out of 23 articles from the selected issue
Vol. 80 Commemorative Accounts
  • Patricia Y. W. Dankers, E. W. Meijer
    2007 Volume 80 Issue 11 Pages 2047-2073
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS FREE ACCESS
    Supramolecular chemistry is an exciting area of science that plays a central role in bringing different disciplines together, ranging from molecular medicine to nanotechnology. Materials science based on supramolecular interactions is an emerging field, which has made important steps forward in the past ten years. The self-assembly of small synthetic molecules into long-chain architectures gives rise to the careful design of supramolecular polymers or fibers based on highly directional, reversible, non-covalent interactions. Much afford is put into the development of supramolecular (polymeric) materials with true materials properties, both in solution and in the solid state. These supramolecular materials are beginning to reach the market in all kind of applications. The field of regenerative medicine in general and that of tissue engineering in particular is one of the most challenging areas in which supramolecular materials might have a high potential. In tissue engineering, the biological environment and the interactions of cells with the artificial biomaterial is of utmost importance for the functioning of the implant, i.e. the engineered tissue. Ideal biomaterials do not only have to fulfil the biomaterials trinity of tuneable mechanical properties, regulation of the degradability and the ease for bioactivity incorporation, but also have to mimic the natural environment where the materials are brought into. Therefore, a modular, self-assembly approach using several supramolecular building blocks is an exquisite way to produce such “responsive” biomaterials. It is proposed that the artificial materials described in this account have the same type of dynamic ability to adapt its biofunctionality as is so well known for the living cells in the host tissue. This account will highlight two systems, i.e. self-assembling oligopeptide fibers as pioneered by Stupp et al. and Zhang et al., and our hydrogen-bonded supramolecular polymers, to show the potential of a modular approach to dynamic biomaterials for tissue engineering.
    Supramolecular biomaterials can be obtained via a modular, self-assembly approach using hydrogen-bonded supramolecular polymers or self-assembling oligopeptide fibers. This results in materials that fulfil the biomaterials trinity of tuneable mechanical properties, degradability and bioactivity, and importantly are dynamic in nature. Fullsize Image
  • Kazunori Sugiyasu, Timothy M. Swager
    2007 Volume 80 Issue 11 Pages 2074-2083
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS FREE ACCESS
    Conducting organic polymers show great promise as sensory materials. The transport of charge in these systems imparts the ability to attain high sensitivity to analytes of interest. This contribution reviews a number of different mechanisms by which analytes can interact with organic conducting polymers to create changes in their resistivity. New sensor systems based upon triaryl-methyl carbocations are also reported for the first time. The design of specific molecular recognition can impart selectivity in this process and in addition the nature of the conducting polymer can also lead to selectivity for different analytes.
    This contribution reviews a number of different mechanisms by which analytes can interact with conducting polymers to create changes in their resistivity. The design of specific molecular recognition and the nature of the conducting polymer can impart high-selectivity for different analytes. Fullsize Image
Award Accounts
The Chemical Society of Japan Award for Creative Work for 2005
  • Takahiro Seki
    2007 Volume 80 Issue 11 Pages 2084-2109
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS FREE ACCESS
    Light can be used as a precise stimulus by selecting suitable wavelengths, polarization directions, and intensity, allowing non-contact control. When photoresponsive (mostly photochromic) molecular units are combined with polymeric materials and liquid-crystalline materials, various types of smart photofunctions can be created. Smart functions involve photomechanical responses, photoalignment of anisotropic materials, orientational amplifications, photoinduced phase changes, photo-tuning of microphase separated structures in block copolymers, and so forth. This article reviews our research strategies, backgrounds, and topics to put forth smart functions in polymer systems organized in two dimensions. It is anticipated that light-driven smart film systems will find many versatile applications as promising future materials.
    Light can be used as a precise stimulus by selecting suitable wavelengths, polarization directions, and intensity, allowing non-contact control. When photoresponsive molecular units are combined with polymeric materials and liquid-crystalline materials, various types of smart photofunctions can be created. This article reviews our research strategies, backgrounds and topics to add smart functions in polymer systems organized in two dimensions. Fullsize Image
Accounts
  • Itaru Honma, Masanori Yamada
    2007 Volume 80 Issue 11 Pages 2110-2123
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS FREE ACCESS
    Bio-inspired materials or natural biopolymers have attracted much attention for industrial applications as biocompatible materials. Although these materials have been discarded as industrial waste around the world, there is an increasing interest in environmental, engineering, and electrical applications of the biomaterials because of their well-controlled structures and superior conducting properties. The controlled structures of the hydrogen-bonding network in biomolecules, such as bioenergetic proteins, are essential for efficient energy transduction in living systems and application of a biomolecular mechanism could make it possible to prepare efficient electrolytes with superior conducting properties. We report here a recent investigation on the new class and new concept of electrolyte materials with bio-inspired molecular architectures of acid–base pairs for anhydrous proton conduction and its application in intermediate temperature (100–200 °C) polymer electrolyte fuel cells (PEFC). Although some membranes were composed from entirely biomolecular materials, they showed large anhydrous proton conductivities from room temperature to 160 °C, and fuel cells employing biomembranes as a polymer electrolyte produced electrical power under non-humidified H2/O2 condition at 160 °C. These bio-inspired materials may have many potential applications not only because of its superior ion conducting properties, in particular, under anhydrous (water-free) or extremely low-humidity conditions, but also because of its biocompatibility.
    The controlled structure in biomolecules is essential for efficient energy conversion in living systems, and biomolecules may produce efficient electrolytes with superior conducting properties. We prepared bio-inspired membranes that showed high proton conductivity under anhydrous conditions. Fullsize Image
BCSJ Award Article
  • Shinzi Ogasawara, Yoshinaga Yoshimura, Masayuki Hayashi, Isao Saito, K ...
    2007 Volume 80 Issue 11 Pages 2124-2130
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS FREE ACCESS
    Branched oligodeoxyribonucleotides (ODNs) are key molecules in constructing nano-scale structures such as DNA lattices, dendrimer-like DNA as well as DNA devices including DNA walkers, DNA memory, and DNA computer. In this paper, two types of highly efficient methods were used to construct the comb-like DNA by using template-directed reversible DNA photocrosslinking via 5-(2-carbamoylvinyl)-2′-deoxyuridine (cvU). The efficiency and thermodynamic stability of three types of reversible DNA photocrosslinked, linear ODN, single-branched ODN (5′-end) and single-branched ODN (mid) reported previously, were also compared. The results show that the most efficient one of the three is a single-branched ODN (5′-end), despite its low thermodynamic stability. In addition, we also showed that this reversible photocrosslinking method is applicable to nanotechnology by constructing comb-like DNA. This method should have great potential in nanotechnology by serving as a platform for fabrication and synthesis, because their sizes and structures can be changed through the alteration of building blocks. We believe that this method is versatile and may find a myriad of applications in the nano-biotechnology field.
    In this paper, the efficiency and thermodynamic stability for three types of reversible DNA photocrosslinked structures were compared. Moreover, two types of highly efficient methods, where were used to construct the comb-like DNA by using template-directed reversible DNA photocross-linking via 5-carbamoylvinyl-2′-deoxyuridine, are described. Fullsize Image
 
  • Maihemutijiang Jieli, Toshiko Miyake, Misako Aida
    2007 Volume 80 Issue 11 Pages 2131-2136
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    A rooted digraph is regarded as a protonated water (PW) cluster, and a hydrogen bond (H-B) matrix can represent a rooted digraph. All possible topology-distinct patterns corresponding to PW clusters containing up to 8 water molecules were enumerated by using H-B matrices. From close investigation of the structural patterns obtained, we found several restrictions that should be satisfied for a structure of the PW clusters to be stable. The generated H-B matrices of the restrictive rooted digraph were used as the theoretical framework to obtain all the topology-distinct local minima of H3O+(H2O)n−1 (n≤5), at the level of MP2/6-31G∗∗ of ab initio MO method. For PW clusters up to tetramers, the local minimum structures that we generated are same as those in the literatures. For PW pentamers, we found some new local minimum structures, which had not been obtained previously.
  • Yusuke Yasuda
    2007 Volume 80 Issue 11 Pages 2137-2144
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Based on the acceleration of Gibbs free energy, −d2G⁄dt2, a kinetic (or falls) model for a catalyzed CO oxidation was developed. Since GT(t) of the system inevitably decreases during a reaction, it may be regarded as the height of water in the model; −d2GT⁄dt2FT corresponding to gravity, may be regarded as the driving force for the reaction to occur. The reaction mechanism for CO(X)+(1/2)O2(Y)→CO2(Z) can be divided into two parallel transformations, X↔AX↔BX→ZX and Y↔AY↔BY→ZY, which are composed of the three elementary steps accompanied by intermediate A and B. The driving force FX for AX and BX to proceed and also FY for AY and BY were determined separately. Because FT (=FX+FY), FX, and FY were independent of t in a definite period, they (instead of G(t)) are useful for describing coupling among the elementary steps and correlations among the intermediates. The reaction can be written X+Y+@→Z+@, where Z means that Z leaving catalysts has hyperthermal energy and @ denotes the active site where BY (assigned to subsurface oxygen) is located. The present dissipative structure is supported by FT, not by any autocatalytic reaction.
  • Toshimasa Ishida, Hideaki Kanno, Jun-ichi Aihara
    2007 Volume 80 Issue 11 Pages 2145-2148
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Gold fullerenes conform to the 2(N+1)2 skeletal electron counting rule, namely, they attain the maximum degree of kinetic stability when they have 2(N+1)2 mobile electrons. Icosahedral Au32 (N=3) is predicted to possess the highest kinetic stability with the largest minimum bond resonance energy. Thus, gold fullerenes are much less sensitive to local ring structure than carbon fullerenes. In such a situation, the 2(N+1)2 rule works as a rule of kinetic stability rather than as that of spherical aromaticity.
  • Yun-Lei Teng, Ling Jiang, Song Han, Qiang Xu
    2007 Volume 80 Issue 11 Pages 2149-2156
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Reactions of laser-ablated lead and tin atoms with water molecules in excess argon were studied by infrared spectroscopy. Insertion products HMOH and HMO (M=Pb and Sn) formed in the present experiments and characterized using infrared spectroscopy on the basis of the results of isotopic shifts, mixed isotopic splitting patterns, stepwise annealing, changes in reagent concentration and laser energy, and a comparison with theoretical predictions. Density functional theory calculations were performed on these molecules and the corresponding transition states. Agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these molecules from the matrix infrared spectra. Plausible reaction mechanisms have been proposed to account for the formation of these molecules.
  • Yasuo Miki, Makoto Toba, Yuji Yoshimura
    2007 Volume 80 Issue 11 Pages 2157-2160
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Sulfur-containing compounds in straight-run naphtha were separated from coexisting hydrocarbons by means of open-column chromatography. Elution with hexane was continued after outflow of saturated hydrocarbons in the original sample, and aromatic hydrocarbons eluted gradually without any accompanying sulfur-containing compounds. When aromatic hydrocarbons ceased to be observed in the effluent, hexane was changed to benzene. A mixture of thiophenes, disulfides, and thiols then began to elute, followed ultimately by a mixture of sulfides and thiacycloalkanes. The obtained sulfur-containing compounds contained very small amounts of hydrocarbons other than the elution solvent, and their mass spectra could be observed by means of gas chromatograph-mass spectrometry.
  • Hideyuki Murakami, Kunihiko Hayashi, Ikuo Tsukada, Takeshi Hasegawa, S ...
    2007 Volume 80 Issue 11 Pages 2161-2169
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    The preparation and structural characterization of a novel molecular solid Brønsted acid based on the Dawson-type sandwich polyoxometalate (POM) are described. The free-acid form of POM, i.e., 8H+-heteropolyacid with the formula H8[Ti2{P2W15O54(OH2)2}2]·31H2O (1) (H8[1a]·31H2O), was prepared by using three different methods: In Method 1, a cation-exchange resin column was used to separate precursor K14H2[Ti2(P2W15O56)2]·26H2O (2), and in Methods 2 and 3, a traditional ether-extraction method was applied for the other precursors, i.e., isolated or in situ generated compound of the tetrameric Ti–O–Ti anhydride species of trititanium(IV)-substituted Dawson POM, K25[{P2W15Ti3O57.5(OH)3}4Cl]·55H2O (3). Compound 1 was characterized by using complete elemental analysis, thermogravimetric (TG) and differential thermal analysis (DTA), Fourier transform infrared (FT-IR) spectroscopy, (31P, 183W) nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography, and potentiometric titration with n-butylamine. The molecular structure of 1a indicated it to be a di-lacunary species of the saturated sandwich complex, [M4(H2O)2(α-P2W15O56)2]n (M = transition-metal ions). From the pH-varied 31P NMR spectra of 2 in water, the degree of protonation of the oxygen atoms at the lacunary sites significantly affects the 31P NMR chemical shift. A Hammett acidity constant H0 of 1 in CH3CN (−2.72) was estimated to be almost the same as that of the homo-Dawson heteropolyacid H6[P2W18O62]·17H2O (−2.77).
  • Hiroshi Fukuoka, Yuji Miyaki, Shoji Yamanaka
    2007 Volume 80 Issue 11 Pages 2170-2176
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS OPEN ACCESS
    Two new ternary barium chromium sulfides, BaCr4S7 and Ba2Cr5S10, were synthesized by reactions of barium sulfide, sulfur, and chromium metal under high-pressure and high-temperature conditions. Single crystals of BaCr4S7 were obtained from a starting mixture with a molar ratio of Ba:Cr:S = 2:5:10 after reacting at 1200 °C and under a pressure of 5 GPa. It crystallizes in the monoclinic space group P21c (No. 14) with a=6.739(4) Å, b=22.665(9) Å, c=5.907(3) Å, β=90.1(4)°, V=902.2(7) Å3, and Z=4. It contains CrS2 sheets composed of edge-sharing CrS6 octahedra. The sheets are connected by wall-shaped subunits composed of face-sharing CrS6 octahedra to form a tunnel structure. Ba atoms are situated in the tunnels. Single crystals of Ba2Cr5S10 were synthesized by heating a mixture with a molar ratio of Ba:Cr:S = 1:1:3 under a pressure of 5 GPa at 1200 °C. It crystallizes in the triclinic space group (No. 2) with a=5.940(4) Å, b=6.645(5) Å, c=17.39(2) Å, α=95.19(3)°, β=91.67(3)°, γ=90.16(2)°, V=683.1(9) Å3, and Z=2. The structure is composed of CrS2 sheets and the wall-shaped subunits, like as in BaCr4S7, but the subunits do not connect the adjacent CrS2 sheets. It has a two-dimensional structure, and Ba atoms are situated in interlayer regions.
  • Katsunori Tanaka, Andrey V. Struts, Sonja Krane, Naoko Fujioka, Gilmar ...
    2007 Volume 80 Issue 11 Pages 2177-2184
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Efficient synthesis of 11-Z-retinals labeled with 2H at the C5, C9, or C13 methyl groups is described. The 2H-labeled retinals were used to regenerate the visual pigment rhodopsin for structural investigations. Solid-state 2H NMR data provided the orientation of retinal within the rhodopsin binding pocket as well as its conformation. Extension of the approach to other membrane receptors can yield knowledge of their mechanisms of activation as a guide for ligand-based drug design.
  • Le Xin Song, Hai Ming Wang, Yan Yang, Peng Xu
    2007 Volume 80 Issue 11 Pages 2185-2195
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Solid inclusion complexes of β- and γ-cyclodextrin (CD) with guaiacol (Gua) were prepared and characterized using elemental analysis, matrix-assisted laser desorption ionization-time of flight mass spectrometry, powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and nuclear magnetic resonance spectroscopy. Based on the results of elemental analysis and 1H NMR, the host–guest stoichiometry of the two solid complexes was determined to be one-to-one. X-ray diffraction patterns of the inclusion complexes gave peak locations consistent with intermolecular complexations between CDs and Gua as well as shape and diffraction intensity of these peaks. The solubility of γ-CD was much less than that of α-CD in water through the complex formation of CD with Gua. Upon inclusion the thermal decomposition point of β-CD or γ-CD as host only slightly increased. However, the thermal stability of the complexed Gua was obviously higher in Gua–β-CD than in Gua–γ-CD. The inclusion phenomenon was attributed to the different strength of intermolecular interactions between host and guest. According to 1H NMR titration measurements, binding constants between Gua and CDs were determined. Furthermore, 1H NMR results indicated that the complexed Gua was likely to have stayed in the wider rim of the cavity of β- or γ-CD. PM3 calculations clearly showed that Gua–γ-CD had the most negative interaction energy, whereas Gua was near the secondary hydroxy rim of the cavity of γ-CD.
  • Tadashi Mizoguchi, Hitoshi Tamiaki
    2007 Volume 80 Issue 11 Pages 2196-2202
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Bacteriochlorophyll(BChl)-c analogs having several esterifying chains at their 17-propionate were synthesized by two procedures. BChls-c with shorter chains (C1 and C4) on the 17-substituent were synthesized by transesterification under mild basic conditions, while those with longer chains (C8 and C16) were obtained by the method of supplementation of exogenous alcohols in the cultures of Chlorobium tepidum. All the BChl-c analogs self-organized to form their micelle-like aggregates in an aqueous solution containing Triton X-100 as a surfactant. To investigate the effect of the length of the esterifying chains, these micelle-like aggregates were characterized by electronic absorption, resonance Raman and dynamic light scattering measurements, and by chemical dissociation of the aggregates. The results indicated that the length of the esterifying chains affected stabilization of the self-assembly of BChls-c but neither construction of the aggregates nor their overall sizes.
  • Ayumi Kashiwada, Kengo Ishida, Kiyomi Matsuda
    2007 Volume 80 Issue 11 Pages 2203-2207
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    To construct a novel isoleucine zipper polypeptide that undergoes a random to coiled coil transition upon lanthanide ion binding, we designed a 37-residue polypeptide (Pep3) with a γ-carboxy glutamic acid (γ-Gla) as metal binding site. Pep3 was designed based on the sequence of the isoleucine zipper polypeptide (Pep1), forming a triple-stranded coiled coil. The coiled-coil structure was destabilized by ionic repulsions among γ-Gla residues at position 21 (hydrophobic 3a position) of one strand. On the other hand, a stable coiled coil formed in the presence of Eu3+ ions. This structural change in the designed polypeptide was selective toward Eu3+ ion from the circular dichroism (CD) measurements. Furthermore, we designed a lanthanide ion-induced heterotrimeric coiled-coil-assembled system by using two kinds of polypeptides, Pep4 and Pep5. CD spectroscopy, sedimentation equilibrium centrifugation, gel filtration, and HPLC analyses indicate that Pep4 and Pep5 could noncovalently assemble in a 1:2 ratio in the presence of Eu3+ ions.
  • Jui-Hsin Su, Fang-Yee Lin, Chang-Feng Dai, Yang-Chang Wu, Chi-Hsin Hsu ...
    2007 Volume 80 Issue 11 Pages 2208-2212
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Six new steroids, chabrolosteroids D–I (16), were isolated from the organic extract of a Taiwanese soft coral Nephthea chabrolii. The structures of these metabolites were determined on the basis of extensive spectroscopic analysis. Metabolite 6 was found to exhibit weak cytotoxicity against the growth of Hep 3B and A-549 cell lines.
  • Md. Delwar Hossain, Tsugio Kitamura
    2007 Volume 80 Issue 11 Pages 2213-2219
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    The reaction of arenes with elemental iodine, acetic acid, and potassium μ-peroxo-hexaoxodisulfate (K2S2O8) in the presence of concentrated sulfuric acid, efficiently generated the corresponding (diacetoxyiodo)arenes in good yields. Diaryliodonium triflates were directly synthesized by reaction of arenes with elemental iodine in good yields by using K2S2O8, AcOH, and TfOH. Diaryliodonium tosylates were also prepared from arenes and elemental iodine by using K2S2O8, AcOH, H2SO4, and TsOH. The procedure involved mild conditions and a straightforward one-pot synthesis.
  • Toshiaki Murai, Sho Nogawa, Yuichiro Mutoh
    2007 Volume 80 Issue 11 Pages 2220-2225
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Selenoiminium salts generated in situ from selenoamides and MeOTf were reacted sequentially with lithium acetylides and Grignard reagents to give 2-propynyl tertiary amines bearing a tetrasubstituted carbon center. The lithium acetylides used were generated from (trimethylsilyl)acetylene, phenylacetylene, and 1-hexyne. Among them, that obtained from (trimethylsilyl)acetylene most effectively gave the corresponding products in higher yields. As Grignard reagents, alkyl-, vinyl-, allyl-, and benzylmagnesium halides gave the products with high efficiency, whereas the reaction of arylmagnesium halides did not proceed as well. A variety of 4-penteneselenoamides were synthesized by four-component coupling reactions of terminal acetylenes, elemental selenium, allylic bromides, and secondary amines, and subjected to the sequential addition reactions to give 5-amino-1,6-enynes. The diastereoselectivity of the reaction was found to depend on the substituents at the α-position of selenoamides and Grignard reagents. In the reaction of selenoiminium salts with excess Grignard reagents, amines that incorporated two molecules of Grignard reagents were formed in good yields.
  • Tomoko Okamoto, Atsuya Momotake, Yoshihiro Shinohara, Ritsuko Nagahata ...
    2007 Volume 80 Issue 11 Pages 2226-2228
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    The efficiency of cis-to-trans isomerization of stilbene-cored polyphenylene dendrimer with alkyl chain at the pheriphery was one order of magnitude lower in hexane than in benzene, whereas that of trans-to-cis isomerization was slightly higher in hexane than in benzene.
  • Kosuke Motoshima, Akinori Sato, Hideki Yorimitsu, Koichiro Oshima
    2007 Volume 80 Issue 11 Pages 2229-2231
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Treatment of phosphines, phosphites, or sulfides with trialkylborane under air afforded the corresponding oxides in good yields.
  • Yoshihiro Sugi, Hiroyoshi Maekawa, Akira Ito, Chikako Ozawa, Tomoko Sh ...
    2007 Volume 80 Issue 11 Pages 2232-2242
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Alkylation, i.e., isopropylation, s-butylation, and t-butylation, of biphenyl (BP) was examined over one-dimensional twelve-membered (12-MR) zeolites: Mordenite (MOR) and SSZ-24 (AFI) with straight channels, and SSZ-55 (ATS) and SSZ-42 (IFR) with corrugated channels. Types of zeolites and alkylating agents highly influenced the selectivities for dialkylbiphenyl (DABP) isomers. Shape-selective formation of 4,4′-diisopropylbiphenyl (4,4′-DIPB) was observed over MOR and AFI; however, ATS and IFR gave 4,4′-DIPB only in low selectivities at 250 °C: 87% over MOR, 60% over AFI, 20% over ATS, and 30% over IFR. The selectivities for 4,4′-di-s-butylbiphenyl (4,4′-DSBB) in the s-butylation were higher than those for 4,4′-DIPB: 95% over MOR, 85% over AFI, 75% over ATS, and 50% over IFR. The t-butylation afforded selectively 4,4′-di-t-butylbiphenyl (4,4′-DTBB) over the zeolites: 96–97% over MOR and AFI, 90% over ATS, and 80% over IFR. These results in the alkylation indicate the exclusion of 4,4′-DABP from other bulky DABP isomers by steric restriction in zeolite channels is an important key for the high shape-selectivity. Even zeolites with large channels, such as ATS and IFR, can have shape-selective nature if the bulky moieties, such as s-butyl and t-butyl groups, are large enough to differentiate the transition state of the least bulky 4,4′-DABP from those of the other isomers inside their channels. The selectivity for 4,4′-DABP decreased at high temperatures in some alkylations: isopropylation over MOR, and s-butylation and t-butylation over MOR, AFI, and ATS. The decreases are due to the isomerization of 4,4′-DABP at external acid sites, because the channels are not large enough for the isomerization of 4,4′-DABP to bulkier 3,4′-DABP. However, the isopropylation over AFI was accompanied by the isomerization of 4,4′-DIPB at external and internal acid sites, because the channels are large enough for the isomerization of 4,4′-DIPB.
  • Masataka Horigome, David A. Pacheco Tanaka, Margot A. Llosa Tanco, Wak ...
    2007 Volume 80 Issue 11 Pages 2243-2245
    Published: November 15, 2007
    Released: November 13, 2007
    JOURNALS RESTRICTED ACCESS
    Hydrogen gas diffusion electrodes were prepared from porous carbon spheres dispersed with Pd–Ag alloy nanoparticles with various Pd/Ag ratios. The performance of the electrodes evaluated by observing the polarization characteristics in the electro-oxidation of hydrogen markedly depended on the ratio of Pd and Ag in the alloy.
feedback
Top