Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 80 , Issue 12
Showing 1-31 articles out of 31 articles from the selected issue
Vol. 80 Commemorative Accounts
  • Keiji Morokuma
    2007 Volume 80 Issue 12 Pages 2247-2261
    Published: December 15, 2007
    Released: December 13, 2007
    JOURNALS FREE ACCESS
    Theoretical/computational studies of chemical reactions provide insight into detailed pathways and energy profiles that are not easily available from experiments. Although finding the potential energy profile for ground-state reactions of small molecular systems has become routine, there are many challenges in theoretical studies of chemical reactions. There are still a lot to learn from gas-phase reactions of small molecular systems, starting from an excited state and cascading though many potential surfaces via conical intersections. Molecular dynamics using quantum mechanical energy (QM/MD) was found to be an ideal tool for study of reactions occurring far from equilibrium, such as formation of fullerenes from small carbon fragments and growth of carbon nanotubes. Challenges in theoretical studies of homogeneous catalysis are subtle ligand effects, involvement of multiple spin states and cooperative effects of multiple metal centers. Discussions here cover stories on activation of molecular nitrogen by zirconium complexes, olefin epoxidation by Salen complexes and reactions of tri-ruthenium complexes. Metalloenzymatic reactions have been discussed using protein models with ONIOM QM:MM approaches as well as active site models. Cases are presented where the enzymatic environment makes rather small effects, where it makes energetically significant effects and where it participates positively into the reaction coordinate.
    Author's recent theoretical/computational studies of chemical reactions have been briefly reviewed, covering gas-phase photochemistry, fullerene and nanotube growth, homogenous catalyses and metalloenzymatic reactions. Theory of chemical reactions provide information not easily obtainable experimentally and is still a fascinating world. Fullsize Image
  • Whitney L. Hough, Robin D. Rogers
    2007 Volume 80 Issue 12 Pages 2262-2269
    Published: December 15, 2007
    Released: December 13, 2007
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    Ionic liquids (ILs) have evolved from salts studied primarily for their physical properties (low melting salts which could be used as solvents) to tunable materials based upon the physical, chemical, and now even biological properties that can be introduced through either ion. In this perspective, we follow this interesting evolution with respect to our work in this growing field, and discuss possible future directions, such as the use of ILs as active pharmaceutical ingredients (APIs).
    Ionic liquids have evolved from their original uses based on their tunable physical properties to unique materials based on their chemical properties and now to active pharmaceutical ingredients based on their biological properties. It seems that the only limit to their applications is one′s imagination. Fullsize Image
  • Stefan Weber, Robert Bittl
    2007 Volume 80 Issue 12 Pages 2270-2284
    Published: December 15, 2007
    Released: December 13, 2007
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    The elucidation of structural and electronic aspects of paramagnetic organic cofactors in their protein surroundings and related model compounds is a topic of widespread interest. In this field, electron paramagnetic resonance (EPR) spectroscopy, especially in conjunction with high-resolution electron-nuclear double resonance (ENDOR) is an important tool, allowing us to analyze details of the distribution of the unpaired electron spin, which is influenced by the interaction between the cofactor and its immediate environment, as well as to characterize paramagnetic intermediate states in the course of the protein action. In this account, investigations are reported in which EPR/ENDOR methods have contributed significantly to answering questions on mechanistic and structural aspects of protein function. Emphasis is given to in-depth characterizations of electronic and spatial structures of radical cofactors and their positioning relative to substrate molecules. After a brief introduction, covering some of the trends of modern EPR/ENDOR method development, we will focus, as examples, on characterizations of quinone-type and flavin cofactors in two proteins, (i) quinoprotein alcohol dehydrogenase, and (ii) DNA photolyase.
    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are important tools to elucidate structural and electronic aspects of paramagnetic cofactors in proteins. In this account, emphasis is given to in-depth EPR/ENDOR characterizations of the quinone-type and flavin cofactors in ethanol dehydrogenase and photolyase, and the relative positioning of substrates.< Fullsize Image
Award Accounts
The Chemical Society of Japan Award for 2005
  • Koichi Komatsu
    2007 Volume 80 Issue 12 Pages 2285-2302
    Published: December 15, 2007
    Released: December 13, 2007
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    A series of two-dimensional, cyclic π-conjugated systems with the six-membered to eight-membered rings as well as polycyclic aromatic compounds and sulfur-containing compounds, which were fully surrounded by rigid bicyclic σ-frameworks, were synthesized and their structures and properties elucidated. This structural modification is characteristic to cause an elevation of the HOMO levels of neutral π-systems and to stabilize remarkably the corresponding cationic systems by both thermodynamic and kinetic effects. In contrast to annelation with a strain-free bicyclic system, such as bicyclo[2.2.2]octene, annelation with a more strained system, such as bicyclo[2.1.1]hexene, brings about a large bond fixation effect upon the cyclic π-system. Thus, π-conjugated systems with quite unusual electronic structures can be prepared by using combination of these structural modifications. As another example of unusual structure, a novel three-dimensional π-conjugated system, i.e., fullerene encapsulating molecular hydrogen, was synthesized from empty fullerene using organic reactions. This is taken as an entirely new approach to the endohedral fullerenes, of which the production has so far relied only on physical methods.
    Rigid bicyclic frameworks surrounding two-dimensional π-conjugated systems are effective in stabilizing the corresponding cationic species, which have unique structures and properties. As an unusual three-dimensional conjugated system, endohedral fullerene encapsulating molecular hydrogen was synthesized. Fullsize Image
BCSJ Award Article
  • Tomoharu Kataoka, Attila J. Mozer, Yasunori Tsukahara, Tomohisa Yamauc ...
    2007 Volume 80 Issue 12 Pages 2303-2312
    Published: December 15, 2007
    Released: December 13, 2007
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    Clear evidence for encaging guest molecules in a host material was obtained for FAU-type zeolite containing fluorescein (FL) as a guest by employing the luminescence-quenching phenomenon of FL with C60. Whereas fluorescence of FL molecules adsorbed on the outer surface of the zeolite was effectively quenched as well as that in a homogeneous solution, that of the most FL molecules in the cages of the zeolite did not suffer from quenching by C60, giving clear evidence that FL molecules are located in the inner cages, which are inaccessible to C60. Only the fluorescence of the FL molecules located in the cages in the outermost unit cells of the zeolite was partially quenched. This partial quenching can be understood by considering the structure of the zeolite and the critical distance of electron transfer inducing the fluorescence quenching.
    Fluorescence of fluorescein located in the cages of a zeolite was not quenched by a quencher, whereas that of fluorescein adsorbed on the outer surface of the zeolite was effectively quenched, giving clear evidence for the location of fluorescein. Fullsize Image
 
  • Le Xin Song, Hai Ming Wang, Peng Xu, Zi Qiang Zhang, Qing Qing Liu
    2007 Volume 80 Issue 12 Pages 2313-2322
    Published: December 15, 2007
    Released: December 13, 2007
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    Inclusion complexations of α- and β-cyclodextrin (CD) with a series of phenol and benzoic acid derivatives both in vacuo and in water were investigated by semiempirical PM3 method. The inclusion systems with a higher negative value of complexation energy or interaction energy were found to have also a larger value of formation constant (Kf) in aqueous solution. The stability of β-CD inclusion complexes depended on the size/shape-fit between host and guest. A good size fitting between the volume of a guest molecule and the free space size of CD cavity effectively improved the stability of CD inclusion complex of the guest. Even though there was no appropriate molar volume ratio (MVR) of a guest to β-CD cavity, a good structural matching between the shape of a guest molecule and the arrangement of β-CD cavity should also obviously improve the stability of β-CD inclusion complex of the guest. Moreover, the CD cavity size exerted a big influence on the stability of these supramolecular complexes. There was an energetic advantage of larger than 45 kJ mol−1 in favor of the intermolecular complexations between α-CD and mono-ortho-substituted phenol derivatives relative to phenol or mono-para-substituted phenol derivatives.
  • Pawel M. Kozlowski, Yoshihito Shiota, Satomi Gomita, Hidetake Seino, Y ...
    2007 Volume 80 Issue 12 Pages 2323-2328
    Published: December 15, 2007
    Released: December 13, 2007
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    The electronic and structural properties of the cubane-type mixed-metal sulfido clusters with a FeIr3S4 core and possible dinitrogen binding and activation were analyzed by density functional theory (DFT) calculations. Five different charges of the cluster and manifold of the electronic states were investigated. For each charge under consideration (+2,+1,0,−1,−2) systematic analysis of structural and electronic properties was carried out. The DFT calculations show that both Fe–N and N≡N bond lengths correlate with the total charge of the cluster. The length of the Fe–N bond decreased, whereas the N≡N bond length increased with the number of added electrons. However, only noticeable elongation of the N≡N bond was observed when the charge of the cluster became negative. Similar analysis was extended to species that have protonated dinitrogen bond. The results obtained from the DFT analysis are useful in considering the principles of the reduction of dinitrogen to ammonia at a single metal center.
  • Yasuo Kameda, Aya Okuyama, Yuko Amo, Takeshi Usuki, Shinji Kohara
    2007 Volume 80 Issue 12 Pages 2329-2333
    Published: December 15, 2007
    Released: December 13, 2007
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    X-ray diffraction measurements on aqueous 2.5 mol % DL-, L-, and D-alanine solutions in D2O were carried out at 26±2 °C in order to obtain information concerning the difference in the hydrogen-bonded structure between aqueous solutions involving amino acid molecules with different optical activities. The difference function, Δiinter(Q), between intermolecular interference term observed for DL- and L-alanine and between DL- and D-alanine solutions both exhibited a first peak at Q=1.6 Å−1, followed by oscillatory features extending to higher-Q region, implying that there is a difference in the intermolecular structure is present between these solutions. The difference distribution function, Δginter(r), obtained from the Fourier transform of the Δiinter(Q) between DL- and L-, and between DL- and D-alanine solutions showed an obvious negative peak at r=2.8 Å, which was attributed to the nearest neighbor hydrogen-bonded O···O interaction. The least squares fitting analysis of the observed Δiinter(Q) showed that the intermolecular O···O distance and the difference in the coordination number between DL- and L-, and between DL- and D-alanine solutions are 2.76(2) Å and −0.18(1), and 2.81(3) Å and −0.18(1), respectively. It was concluded that the intermolecular hydrogen-bonded network in aqueous L- and D-alanine solutions is stronger than that in the DL-alanine solution.
  • Keisuke Matsuoka, Shigeaki Ishii, Chikako Honda, Kazutoyo Endo, Akio S ...
    2007 Volume 80 Issue 12 Pages 2334-2341
    Published: December 15, 2007
    Released: December 13, 2007
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    The solubility of cholesterol in the binary solubilizates system (cholesterol and β-sitosterol) of a sodium taurodeoxycholate solution decreased to almost half of that in the single cholesterol system. On the other hand, the cholesterol solubilities in other binary other systems (cholesterol and certain aromatics) of those solutions were the same as that of the single cholesterol system. The results of competitive solubilization between sterols and aromatics suggested that both were solubilized at different solubilization sites of a micelle. Their molecular dynamics and solubilization sites were measured by the 1H NMR method. The rotating-frame nuclear Overhauser effect and exchange spectroscopy (ROESY) contour plot of aromatics solubilized micellar solution exhibited direct cross-peaks between the aromatics and bile salt of 19-methyl protons. The observed ROESY spectra of the sterol-solubilized solutions were almost identical to those of the pure micellar solution. The spin-lattice relaxation time (T1) for aromatics solubilized in the micellar solutions increased for 18-, 19-, and 21-methyl protons of the bile salt in comparison with those of a pure micellar solution, which indicated that the micellar core changed to a loosely packed state owing to the penetration of aromatics. On the other hand, the T1 values for sterols solubilized in micelles were lesser than those for pure micellar solutions for almost all proton positions, which suggested that the sterols were compatible with the micelle. These results indicated that the aromatics were solubilized in micellar palisade layer interacting with bile salt of methyl protons, whereas, the sterols were solubilized to match the micellar structure via the steroids interaction.
  • Masashi Hatanaka, Ryuichi Shiba
    2007 Volume 80 Issue 12 Pages 2342-2349
    Published: December 15, 2007
    Released: December 13, 2007
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    Ferromagnetic interactions in non-Kekulé polymers were analyzed under the periodic boundary condition. We transformed Bloch functions of non-bonding crystal orbitals (NBCOs) into Wannier functions. The product of the ν-th and (ν+1)-th Wannier functions was defined as PNBCOν,ν+1 (product of NBCOs). In so-called nondisjoint-type polymers, ferromagnetic ground states resulted from instabilities of anti-parallel-spin states in PNBCOν,ν+1. The instabilities consisted of “on-site term” and “through-space term.” The former corresponded to squared amplitude of the same atomic site on PNBCOν,ν+1, and the latter corresponded to antibonding-through-space interactions in PNBCOν,ν+1. The instabilities led to ferromagnetic-spin alignment. On the other hand, in so called disjoint polymers, such instabilities did not emerge.
  • Wataru Kosaka, Kazuhito Hashimoto, Shin-ichi Ohkoshi
    2007 Volume 80 Issue 12 Pages 2350-2356
    Published: December 15, 2007
    Released: December 13, 2007
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    Reaction of GdIII(NO)3·6H2O and (Bu3NH)3[WV(CN)8] (Bu3N = tributylamine) in N,N-dimethylacetamide (DMA) yielded two types of Gd–W bimetal assemblies with noncentrosymmetric crystal structures: GdIII(DMA)n[WV(CN)8] (n=6, 1; n=5, 2). X-ray single crystal analyses showed that 1 crystallizes in the monoclinic system of the Cc space group (a=12.6254(6) Å, b=16.8052(8) Å, c=20.2499(11) Å, β=103.2893(18)°, Z=4), and 2 crystallizes in the monoclinic system of the P21 space group (a=9.761(2) Å, b=19.573(5) Å, c=10.502(4) Å, β=109.247(12)°, Z=2). These two crystals consist of one-dimensional linear chains, in which [GdIII(DMA)n]3+ and [WV(CN)8]3− ions are linked in an alternating fashion. The difference between these two compounds, that is, 1 contains eight-coordinate GdIII whereas 2 contains seven-coordinate GdIII, is due to the temperature during preparation. Magnetic data showed that the magnetic interaction between GdIII (S=7⁄2) and WV (S=1⁄2) is antiferromagnetic coupling of −0.28(1) cm−1 for 1 and −0.42(1) cm−1 for 2.
  • Gene Frederick Gagabe, Yuta Satoh, Keiichi Satoh, Kiyoshi Sawada
    2007 Volume 80 Issue 12 Pages 2357-2364
    Published: December 15, 2007
    Released: December 13, 2007
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    Synergistic extraction of thenoyltrifluoroacetone (tta) complexes of 14 trivalent lanthanoids (Ln3+) into 1,2-dichloroethane with linear poly(oxyethylene) compounds (POE) was investigated at 25.0 °C, where the linear POE [HO–(CH2CH2O–)nR] are monodispersed DEOn (R=C12H25; n=4, 6, and 8) and polydispersed TX-100 (R = octylphenyl; nave=9.6). Equilibrium studies showed a 1:1 adduct complex with POE compound, Ln(tta)3·(POE), formed in the organic phase. The adduct formation constant, βadd, increased as the ionic radius of lanthanoid increased for any kind of POE. The very high stability of the 18-crown-6 adducts is explained by the incorporation of Ln3+ ion into the cavity of the crown ether. Adduct formation constants of the POE having short ethylene oxide (EO) chain, such as DEO4 and 12-crown-4, were fairly small; thus, it was estimated that those coordinate to the metal ion as a bidentate or tridentate ligand. Relatively large values of βadd of long chain POE (n≥6) indicate the indirect outer-sphere interaction of the uncoordinated residual EO units with the metal ion. Adduct formation with linear POEs significantly reduced the difference in extraction constants among the lanthanoid ions. Therefore, this synergistic extraction system is advantageous for the separation of lanthanoid ions as a group from other metal ions.
  • Chongmin Zhong, Takehiko Sasaki, Akiko Jimbo-Kobayashi, Emiko Fujiwara ...
    2007 Volume 80 Issue 12 Pages 2365-2374
    Published: December 15, 2007
    Released: December 13, 2007
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    A series of metal ion-containing ionic liquids [Bmim]2[MCl4] (M = Sn, Cu, Ni, Mn, Fe, Co, Zn, and Pt; [Bmim] = 1-butyl-3-methylimidazolium) and [Bmim]2[ZrCl6] were synthesized and their single-crystal structures were determined by X-ray crystallographic analysis. The crystal structures showed the existence of an interaction between chlorometalate anions and imidazolium cations via C–H···Cl hydrogen bonding as well as an interaction between the cations through C–H···π hydrogen bonding and/or π···π stack interaction. The melting points of the metal salts were found to correlate with the number of halide ions coordinated to each metal ion and the overall symmetry of the chlorometalate anions. Ionic conductivity measured in super-cooled states of the synthesized salts unambiguously confirmed that these salts behaved as ionic liquids. The synthesized salts have a high thermal stability as evaluated by TGA and negligible vapor pressure before decomposition.
  • Shinya Imatomi, Tetsuya Sato, Takefumi Hamamatsu, Ryoko Kitashima, Nao ...
    2007 Volume 80 Issue 12 Pages 2375-2377
    Published: December 15, 2007
    Released: December 13, 2007
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    Isomorphous bi- and mononuclear iron(III) complexes, [FeIII2L2(bimb)](BPh4)2 (1) and [FeIIIL(meim)]BPh4 (2), where H2L = bis(3-methoxysalicylideneaminopropyl)amine, bimb = 1,4-bisimidazolylbutane, meim = N-methylimidazole, and BPh4 = tetraphenylborate, respectively, were synthsized. Binuclear complex 1 showed a two-step spin-crossover (SCO) behavior at T1⁄2=60 and 90 K, whereas mononuclear complex 2 showed a one-step SCO behavior at T1⁄2=215 K. The different SCO behavior can be ascribed to the quasi-one-dimensional structure constructed by π–π stacking and the binuclear structure.
  • Mizue Fujio, Md. Ashadul Alam, Yuzo Umezaki, Kiyoshi Kikukawa, Ryoji F ...
    2007 Volume 80 Issue 12 Pages 2378-2383
    Published: December 15, 2007
    Released: December 13, 2007
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    Solvolysis rates of 2-[dimethyl(X-phenyl)silyl]-1-(Y-phenyl)ethyl 3,5-dinitrobenzoates were determined conductimetrically in 60% (v/v) aqueous ethanol. The effects of substituents X in the β-arylsilyl moiety (X-C6H4(CH3)2Si–) were analyzed by means of the Yukawa–Tsuno Equation. The X-phenyl-Si substituent effects (at 25 °C) were correlated against a set of X parameters of r+≅0.1 to give a [(ρX)Si] value of −1.06 for α-Ph (Y=H) and [(ρX)Si]=−1.18 for α-(m-CF3)phenyl (Y = m-CF3) subsets, which are all distinctly lower than that of −1.75 for the 2-[dimethyl(X-phenyl)silyl]ethyl solvolysis. The δY[(ρX)Si]Y can be regarded as the effect of the aryl substituents on the β-Si moiety on the benzylic cation center in the rate-determining step. The α-aryl substituent effect δY[log(kY)X=H] of 2-[dimethyl(X-phenyl)silyl]-1-(Y-phenyl)ethyl system was correlated against Y scale characteristic of the benzylic cation reactions (r+≅1.0) to give (ρY)α-Ar≅−3.0. The [(ρX)Si]Y values changed in parallel with the reactivities δY[log(kY)X=H] of the α-Ar substrate.
  • Naoko Senda, Atsuya Momotake, Tatsuo Arai
    2007 Volume 80 Issue 12 Pages 2384-2388
    Published: December 15, 2007
    Released: December 13, 2007
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    7-[{Bis(carboxymethyl)amino}coumarin-4-yl]methyl-caged neurotransmitters (glutamate and GABA) were synthesized. Both caged compounds showed sufficient stability in the dark, were water-soluble at pH 7.2 without using organic solvents, and exhibited relatively high quantum yield for photolysis upon irradiation with 390 nm light.
  • Takahiro Soma, Nobumasa Kamigata, Kazunori Hirabayashi, Toshio Shimizu
    2007 Volume 80 Issue 12 Pages 2389-2394
    Published: December 15, 2007
    Released: December 13, 2007
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    Selenonium imides 1 and 2, stabilized by intramolecular coordination of the amino group of 8-dimethylamino-1-naphthyl substituent to the selenium atom, were synthesized. Optically active selenonium imides were obtained by chromatographic resolution on optically active columns and were found to be stable toward racemization both in the solid state and in solution. Absolute configurations of the optically active selenonium imides were assigned on the basis of specific rotations and circular dichroism spectra.
  • Ping-Jyun Sung, Li-Fan Chuang, Wan-Ping Hu
    2007 Volume 80 Issue 12 Pages 2395-2399
    Published: December 15, 2007
    Released: December 13, 2007
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    Two new caryophyllane-type hemiketal norsesquiterpenoid alcohols, designated as rumphellatins B (1) and C (2), were obtained from the Formosan gorgonian coral Rumphella antipathies. The structures of natural products 1 and 2 were established by analyzing the spectral data. Rumphellatin B (1) showed antibacterial activity toward the Gram-positive bacterium Staphylococcus aureus.
  • Minoru Uemura, Masayuki Iwasaki, Eiji Morita, Hideki Yorimitsu, Koichi ...
    2007 Volume 80 Issue 12 Pages 2400-2405
    Published: December 15, 2007
    Released: December 13, 2007
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    Reaction of acid chlorides with lithium pentamethylcyclopentadienide afforded the corresponding pentamethylcyclopentadienyl ketones in high yield. These ketones were treated with an allylaluminum reagent to form the corresponding 3-butenyl alcohols. Removal of pentamethylcyclopentadiene upon heating or treatment with a catalytic amount of trichloroacetic acid yielded the corresponding β,γ-unsaturated ketones in good yields.
  • Hitoshi Nagao, Yoshikazu Kawano, Teruaki Mukaiyama
    2007 Volume 80 Issue 12 Pages 2406-2412
    Published: December 15, 2007
    Released: December 13, 2007
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    Chiral quaternary ammonium phenoxides were prepared readily from commercially available cinchona alkaloids and employed as novel useful asymmetric organocatalysts. Among these chiral quaternary ammonium phenoxides, a cinchonidine-derived phenoxide that possesses a sterically hindered N(1)-3,5-bis[3,5-bis(trifluoromethyl)phenyl]benzyl group was the most effective for asymmetric trifluoromethylation. In the presence of a catalytic amount of Lewis bases, such as cinchonidine-derived quaternary ammonium phenoxides, catalyzed the reaction of various ketones with (trifluoromethyl)trimethylsilane to afford the corresponding trifluoromethylated adducts in high yields and with moderate to high enantioselectivities.
  • Yumi Nakaike, Noriko Taba, Shinobu Itoh, Yoshito Tobe, Nagatoshi Nishi ...
    2007 Volume 80 Issue 12 Pages 2413-2417
    Published: December 15, 2007
    Released: December 13, 2007
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    A 2-nitrated 3-oxoester reacted with amines or alcohols to afford unsymmetrical malonic acid derivatives as a result of nucleophilic substitution accompanying C–C bond cleavage. The 2-nitrated 3-oxoester easily formed ammonium salts with amines. When the amine is liberated from the salt under equilibrium, nucleophilic amine and electrophilic keto ester locate close to each other. This intimate pair effect causes a pseudo intramolecular reaction to occur, giving rise to effective substitution under mild conditions.
  • Ayako Taketoshi, Naoya Hosoda, Yoshitaka Yamaguchi, Masatoshi Asami
    2007 Volume 80 Issue 12 Pages 2418-2424
    Published: December 15, 2007
    Released: December 13, 2007
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    Diastereoselective allylation of 3,4-dihydro-4-phenylisoquinoline by several allylating reagents was examined. Reactions using allyltin or allylsilane in the presence of alkyl chloroformate and a catalytic amount of trimethylsilyl triflate gave trans-1-allyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline with moderate diastereoselectivity. In contrast, cis-1-allyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline was obtained predominantly in the reactions using allyllithium, triallylborane, allylzinc bromide, and diallylzinc. cis-1-Allyl-4-phenyl-1,2,3,4-tetrahydroisoquinoline was transformed to (6S,10bR)-hexahydro-6-phenylpyrrolo[2,1-a]isoquinoline, a potential antidepressant agent, in five steps.
  • Takahiro Sasamori, Eiko Mieda, Norihiro Tokitoh
    2007 Volume 80 Issue 12 Pages 2425-2435
    Published: December 15, 2007
    Released: December 13, 2007
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    Novel heterocyclic compounds containing chalcogen (S, Se, and Te) and pnictogen (P, Sb, and Bi) atoms were obtained by chalcogenation reactions of the doubly bonded systems between heavier group 15 elements (dipnictenes) kinetically stabilized by 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt) groups. Whereas the sulfurization reaction of BbtP=PBbt (1) with elemental sulfur (S8) gave the Bbt-substituted thiadiphosphirane, i.e., the three-membered ring compound of P–S–P, those of BbtSb=SbBbt (2) and BbtBi=BiBbt (3) afforded the corresponding five-membered ring compounds, i.e., the 1,2,4,3,5-trithiadistibolane and 1,2,4,3,5-trithiadibismolane, as the main products, respectively. From each selenization reaction of dipnictenes 13 using elemental selenium, the corresponding three-membered ring compounds (selenadipnictiranes) were obtained as stable compounds. On the other hand, the tellurization reactions of distibene 2 and dibismuthene 3 using (n-Bu)3P=Te gave the corresponding telluradipnictiranes as in the case of their selenization reactions, though diphosphene 1 underwent no tellurization when (n-Bu)3P=Te or elemental tellurium was used as a tellurium source.
  • Tsuyoshi Michinobu, Masami Bito, Yoshiko Yamada, Yoshihiro Katayama, K ...
    2007 Volume 80 Issue 12 Pages 2436-2442
    Published: December 15, 2007
    Released: December 13, 2007
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    A chemically stable metabolic intermediate of lignin, 2-pyrone-4,6-dicarboxylic acid (PDC), was isolated, and the molecular properties were comprehensively investigated by using thermal analysis, optical spectroscopy, potentiometric titration, and X-ray crystallography. UV absorption spectra of PDC did not show any solvent effects, whereas the fluorescence spectra displayed distinct solvatochromism. Despite the fairly good planarity of the PDC geometry, dual fluorescence was observed in some small donor number solvents. The emission behaviors are thought to be due to the significant twist between the pyrone ring and carboxylate substituents, found in the X-ray crystal structures of the Na+ complex. The crystal structure also showed the intermolecular, centrosymmetric short hydrogen bonding of the carboxylate moieties with an O···H···O distance of 0.2452 nm, which made it possible to assign the pKa values to the molecular structure. PDC was thermally stable and could be sublimed even at atmospheric pressure, offering the preparation possibility of ultra-thin films by vapor-deposition techniques. The fact that the chemically and thermally stable compound possessing many attractive functions, such as unique emission, facile sublimation, and strong acidity, resulting in exceptionally short intermolecular contacts, can be obtained from biomass on a large quantity will lead to establishment of carbon neutral system in future industry.
  • Takenori Mitamura, Yoshiaki Imanishi, Akihiro Nomoto, Motohiro Sonoda, ...
    2007 Volume 80 Issue 12 Pages 2443-2445
    Published: December 15, 2007
    Released: December 13, 2007
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    By using a binary system that consisted of benzenethiol and diphenyl diselenide under photoirradiation through a Pyrex vessel with a xenon lamp (λ>300 nm), a variety of conjugate dienes could be reduced to the corresponding internal alkenes under mild conditions.
  • Yukou Du, Naoki Toshima
    2007 Volume 80 Issue 12 Pages 2446-2450
    Published: December 15, 2007
    Released: December 13, 2007
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    CdS nanoparticles with size of 2.5±0.4 nm were prepared by using well-known reverse micelle methods. The CdS particles were characterized with ultraviolet and visible (UV–vis) absorption spectroscopy, transmission electron microscopy (TEM), energy-disperse X-ray analysis (EDX), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD). Twisted nematic liquid crystal display (TN-LCD) devices, doped with various amount of CdS nanoparticles, were studied for the first time. The results showed that electro-optic characteristics were featured by a frequency modulation. As the amount of dopant increased, a wider frequency response was achieved. Interestingly, the driving voltage of TN-LCD decreased as 4′-pentylbiphenyl-4-carbonitrile (4′-pentyl-4-cyanobiphenyl, 5CB) was doped with CdS nanoparticles.
  • Teruyuki Nakato, Jun Sugawara
    2007 Volume 80 Issue 12 Pages 2451-2456
    Published: December 15, 2007
    Released: December 13, 2007
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    Inorganic oxide nanosheets, prepared by exfoliation of layered hexaniobate K4Nb6O17, were investigated in a colloidal state with different hierarchies: micrometer to submillimeter level with microscopies and molecular level with visible spectroscopy. A cationic porphyrin 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine (H2TMPyP) was added to the colloid as a spectroscopic probe. The Soret absorption band of porphyrin adsorbed on the niobate nanosheets was split when the colloid was concentrated. The modified spectral profile was retained when the colloid was re-diluted, indicating irreversible alteration that reflected concentration history of the dispersed state of the nanosheets. Fluorescence optical and transmission electron microscopies indicated aggregation and crumpling of the nanosheets in the colloids that were concentrated. The alteration of the colloidal nanosheets upon concentration was ascribed to the enrichment of electrolytes coexisting in the colloid. The results demonstrated that the microscopic status of the colloidally dispersed exfoliated nanosheets is related to the microenvironments formed by functional molecules immobilized on the nanosheets.
  • Hideki Kato, Yasuyoshi Sasaki, Akihide Iwase, Akihiko Kudo
    2007 Volume 80 Issue 12 Pages 2457-2464
    Published: December 15, 2007
    Released: December 13, 2007
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    A combination system consisting of a H2 production photocatalyst, Pt/SrTiO3:Rh, and an O2 production photocatalyst, BiVO4 or WO3, decomposed water into H2 and O2 under visible light irradiation in the presence of an Fe3+/Fe2+ redox couple as an electron mediator. O2 evolution on the BiVO4 photocatalyst was inhibited by Fe2+ ions, because of the oxidation of Fe2+ instead of water. In contrast, H2 evolution on the Pt/SrTiO3:Rh photocatalyst was enhanced when Fe3+ ions co-existed. It is due to the back-reactions between H2 and O2 to form water, and the reduction of Fe3+ by H2, which easily proceeded on the bare Pt cocatalyst surface, being efficiently suppressed by adsorption of [Fe(SO4)(H2O)5]+ and/or [Fe(OH)(H2O)5]2+ on the Pt surface. Overall water splitting was achieved with the suppression of the back-reactions even using a Pt cocatalyst. Thus, it clears that iron ions contributed to the present Z-scheme systems not only as an electron mediator but also as an inhibitor of the back-reactions.
  • Mohamed E. El-Khouly, Jong Hyung Kim, Minseok Kwak, Chan Soo Choi, Osa ...
    2007 Volume 80 Issue 12 Pages 2465-2472
    Published: December 15, 2007
    Released: December 13, 2007
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    Photoinduced intramolecular events of the newly synthesized fullerene–triphenylamine–fullerene (C60–TPA–C60) triad, in which the TPA entity was substituted with an electron-donating CH3O-group to increase electron-donating ability, were investigated in relation to a C60–TPA dyad. The molecular orbital calculations showed that the radical cation is located on the TPA entity, whereas the radical anion is located on two C60 entities in the radical ion pair. The fluorescence intensity of the singlet excited state of C60 was efficiently quenched by the attached TPA moiety in polar solvents. The quenching pathway involves a charge-separation process from the TPA to the singlet excited state C60. The lifetimes of the radical ion-pairs for C60–TPA–C60 evaluated from nanosecond transient absorption measurements were found to be 600 and 454 ns in benzonitrile and dimethylformamide, respectively. These lifetimes of radical ion-pairs of C60–TPA–C60 are longer than those of the C60–TPA dyad, which reflects the effect of the second C60 moiety in stabilizing the radical ion-pairs.
  • Yoshihito Kunugi, Hideyuki Hayakawa, Katsuhiko Tsunashima, Masashi Sug ...
    2007 Volume 80 Issue 12 Pages 2473-2475
    Published: December 15, 2007
    Released: December 13, 2007
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    Dye-sensitized solar cells using quaternary phosphonium ionic liquids as their electrolytes have been successfully fabricated. Of these, the best device performance was achieved by using triethyl(pentyl)phosphonium bis(trifluoromethylsulfonyl)amide, whose energy conversion efficiencies were determined to be 1.2% and 3.8% under full (AM 1.5, 100 mW cm−2) and low intensity (7 mW cm−2) sunlight illumination, respectively. Interestingly, the energy conversion efficiencies for the quaternary phosphonium ionic liquid electrolytes are higher than those for the corresponding quaternary ammonium ionic liquids.
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