Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 70 , Issue 8
Showing 1-34 articles out of 34 articles from the selected issue
  • Megumu Munakata, Liang Ping Wu, Takayoshi Kuroda-Sowa
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1727-1743
    Published: 1997
    Released: June 15, 2006
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    Considerable progress has been made in recent years in controlling the assembly and orientations of individual molecules to create specific aggregates. It is the aim of this review to give an account of the latest developments in our groups with regard to construction of functional crystal metal complex supermolecules from self-assembly of copper(I) and silver(I) coordination compounds by intermolecular interactions as well as coordination bonds. Several approaches to such self-organization process have been highlighted. Spontaneous organization of hydrogen bonding and host–guest interactions in 3-cyano-6-methyl-2(1H)-pyridinone system result in the formation of three-dimensional channel structures and multi-fold interpenetrated diamondoid architectures by modification of hydrogen-bonding mode and distances. Control of effective aromatic stackings between polymeric chains assembles simple phenazine and benzothiadiazole building blocks into well-organized, multidimensional honeycomb and graphite structures. Manipulation of strong interchain S···S contacts in sulfur-rich tetrathiafulvalene derivative system creates a unique bookshelf type frameworks. Employment of multi-coordination sites of the ligands in pyrazine, dithienylethene and dithiaparacyclophane systems generates a number of novel infinite-sheet and -chain metal polymers with the potential to serve as functional supramolecular devices.
  • Hajime Yasuda, Eiji Ihara
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1745-1767
    Published: 1997
    Released: June 15, 2006
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    This review article deals with the rare earth metal initiated polymerization of polar and nonpolar monomers in living fashion (“living” means very active without termination and chain transfer reaction) to give monodisperse high molecular weight polymers at high conversion. A typical example is seen in the polymerization of methyl methacrylate with [SmH(C5Me5)2]2 or [LnMe(C5Me5)2(THF)] (Ln = Sm, Y, and Lu), giving high molecular weight syndiotactic polymers (Mn > 500000, syndiotacticity > 95%) quantitatively at low temperature (−95 °C). The initiation mechanism was discussed on the basis of X-ray analysis of the 1 : 2 adduct (molar ratio) of [SmH(C5Me5)2]2 with MMA. Living polymerizations of alkyl acrylates (methyl acrylate, ethyl acrylate, and butyl acrylate) were also possible by the catalysis of [LnMe(C5Me5)2(THF)] (Ln = Sm, Y); i.e. poly(methyl acrylate) Mn = 48 × 103, Mw/Mn = 1.04, poly(ethyl acrylate) Mn = 55 × 103, Mw/Mn = 1.04, and poly(butyl acrylate) Mn = 70 × 103, Mw/Mn = 1.05. By taking advantages of the living polymerization ability, we attempted ABA triblock copolymerization of MMA/butyl acrylate/MMA to obtain rubber-like elastic polymers. Lanthanum alkoxide(III) has good catalytic activity for the polymerization of alkyl isocyanates (Mn > 106, Mw/Mn = 2.08). Monodisperse polymerizations of lactones, lactide, and various oxiranes were also achieved by polymerization with rare earth metal complexes. C1 symmetric bulky organolanthanide(III) complexes such as {SiMe2[2(3),4-(SiMe)2C5H2]2LnCH(SiMe3)2} (Ln = La, Sm, and Y) show high activity for linear polymerization of ethylene. Organolanthanide(II) complexes such as racemic {SiMe2[2-SiMe3-4-tBu-C5H2]2Sm(THF)} as well as C1 symmetric {SiMe2[2(3),4-(SiMe3)2C5H2]2Sm(THF)} were also found to have high activity for the polymerization of ethylene. Thus, polyethylene of Mn > 106 (Mw/Mn = 1.6) was first obtained by using {SiMe2[2(3),4-(SiMe3)2C5H2]2Sm(THF)}. 1,4-Cis conjugated diene polymerization of 1,3-butadiene and isoprene became available by the efficient catalytic activity of NdCl(C5H5)2/AlR3 or Nd(octanoate)3/AlR3. The Ln(naphthenate)3/AliBu3 system allows selective polymerization of acetylene in cis-fashion. Utilyzing the fact that rare earth metal initiated living polymerization proceeds for both polar and nonpolar monomers, researchers have attempted to block copolymerization of ethylene with MMA or lactones yielding polyethylene derivatives having high chemical reactivity.
  • Ahmed Galal, Nada F. Atta, Soher A. Darwish, AbuBakr M. Abdallah
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1769-1776
    Published: 1997
    Released: June 15, 2006
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    Ferrocenium hexafluorophosphate was used as the supporting electrolyte during the electropolymerization of poly(3-methylthiophene) and poly(1-methylpyrrole). The electrochemical behavior of the resulting polymer electrode indicated the incorporation of the ferrocenium moiety in the polymer film. The appearance and the magnitudes of the voltammetric anodic and cathodic current peaks of the ferrocenium/ferrocenium+ couples were influenced by: (I) the method of ferrocene incorporation into the polymer film, (ii) the concentration of both the ferrocenium and the supporting electrolyte used during the polymer deposition, (iii) the thickness of the polymer film, and (iv) the type of electrolyte used during the polymer film electrochemical characterization. FTIR experiments were performed on polymer films containing the ferrocenecarbaldehyde. The results were compared to the spectrum of ferrocene-free film; the comparison indicated the incorporation of the ferrocene moiety within the polymer film. The structural aspects of the polymer films were studied using XPS experiments, which indicated the presence of iron for films containing ferrocenium. The morphological aspects of the films were studied by SEM technique which indicated that “ferrocenium-free” film morphologies are similar to those of “ferrocenium-containing” films. A model for the charge transfer within the polymer film is described. The method described in this work resulted in a stable ferrocenium-bound to the polymeric film.
  • Hideyuki Narumi
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1777-1785
    Published: 1997
    Released: June 15, 2006
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    Voltammograms observed on basal planes of a Pt single crystal electrode in 0.1 M HClO4 were analyzed theoretically. Adsorbed hydrogen atoms were assumed to form 2-dimensional (111), (100), and (110) lattices. These lattices were treated by applying the Hückel method to an elementary domain consisting of 400 × 200 lattice points with periodic boundary conditions. Results explained the essential aspects of the butterfly at Pt(111) and the hydrogen waves at Pt(100) and Pt(110). The lateral interactions of the adsorbed hydrogen atoms were attractive in all cases and their values were estimated. The value at Pt(110) reproduced the previous one derived from the adsorption isotherm analysis. The square-shaped wave observed at Pt(111) in a potential range of 0.05—0.35 V was explained by an entirely different model for a freely moving particle. The analysis suggested that the square wave is due to electrons which move freely in the adsorption layer. The Hückel method was further applied to 3-dimensional lattices having 2 to 3 layers. Results suggested a striking effect of the absorbed hydrogen beneath the surface on the hydrogen wave.
  • Junji Inukai, Yukiko Morioka, Youn-Geun Kim, Shueh-Lin Yau, Kingo Itay ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1787-1794
    Published: 1997
    Released: June 15, 2006
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    In-situ infrared reflection absorption spectroscopy was applied to the investigation of cation effects on the C–N stretching frequency of cyanide ions on Pt(111) electrode in electrolyte solutions. Only a single absorption peak was observed at ca. 2100 cm−1 in solutions containing H3O+, Li+, Na+, K+, or Cs+. In a KClO4 solution (pH = 9.5), a change in slope was observed in the peak frequency–potential curve at ca. −0.5 V vs. the saturated calomel electrode. It was concluded that in the cathodic region in the KClO4 solution, H3O+ dominates the outer Helmholtz plane as a result of cation exchange. In alkaline solutions, the slope for the frequency shift is dependent on the cations in the order K+ > Na+ > Li+ ≈ Cs+. In HClO4, a change in slope was also observed in the peak frequency-potential curve. In a Mg(ClO4)2 solution, three peaks were observed for CN on Pt(111), indicating that factors other than the simple electrochemical Stark effect must be considered for interpreting the influence of this strongly adsorbed cation.
  • Yosuke Kataoka, Mitsuhiro Matsumoto
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1795-1804
    Published: 1997
    Released: June 15, 2006
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    The equation of state of an acetic acid fluid was derived by molecular-dynamics simulations on a rigid-molecule model. The optimized potential for liquid simulations (OPLS) given by Briggs, Nguyen, and Jorgensen was assumed. Only the Z form was adopted in the two conformers in order to save central processing unit (CPU) time to perform the molecular-dynamics simulation at many state points. Microcanonical simulations were performed for 729 states. The system had 256 molecules in the cubic basic cell. The equation of state was obtained by a least-squares fitting. The critical point and liquid-vapor phase boundary were compared with the observed values. Dimerization was also observed by 27 long runs in the gaseous phase around the liquid–vapor phase boundary. The main structure is hydrogen-bonded chains in the liquid phase. The excess entropy after subtracting the ideal gas term is −10R at low temperatures. This is compared with −8R in liquid water. These comparisons show that the present model can be used to simulate the hydrogen-bonded fluid of acetic acid.
  • Hiroshi Ichikawa, Hirotaka Kagawa
    1997 Volume 70 Issue 8 Pages 1805-1807
    Published: 1997
    Released: June 15, 2006
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    In an attempt to comfirm the role of π electrons in benzene, the relationship between the π-electron distribution and the preferred symmetry in C6H6 systems was examined. It was shown that under the restriction of being planar, the C6H66+ system has a D6h geometry, which is fragile towards shrinking as well as a distortion, and is also fragile at saddle points towards bending. When π electrons are added to such a system, the π electrons distribute in the way of either D6h or D2h symmetry according to the number of electrons. When the π-electron distribution is D6h-symmetric, non-distortive (i.e., those along the A1g coordinate) forces are produced; when it is D2h-symmetric, distortive forces, i.e., those that break the D6h symmetry, appear. Optimization leads to a symmetry which is pre-determined by the π-electron distribution. In this way, it was elucidated that π electrons in benzene have a tendency to form a uniform distribution.
  • Takehiko Mori, Yohji Misaki, Tokio Yamabe
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1809-1812
    Published: 1997
    Released: June 15, 2006
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    The crystal structure of the title compound, where TTM–TTP is 2,5-bis [4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, has been determined by X-ray analysis. The donors form a uniform stack, which is responsible for metallic conduction down to TMI = 20 K. The anions are composed of discrete I3 and an infinite chain of I3. Each donor has anomalously large positive charge of +5/3.
  • Yuko Tsutsui, Hiroaki Wasada, Shigenobu Funahashi
    1997 Volume 70 Issue 8 Pages 1813-1825
    Published: 1997
    Released: June 15, 2006
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    We studied the characteristics of model intermediary species on reaction pathways using the ab initio molecular orbital method in order to explain a change in the mechanistic behavior of the water-exchange reaction of hexahydrated divalent cations when the central elements were changed in the first transition series. Calculations show that the hexacoordinated species binding to the entering water in the second shell, the dissociative pentacoordinated species of scandium(II) and copper(II) ions, and the associative heptacoordinated species of scandium(II) ion are at local minima, whereas the heptacoordinated species of copper(II) ion is at a second-order saddle point. We also considered calcium(II) and zinc(II) ions in order to examine the correlation between the intermediary species and the reaction mechanisms. All of the intermediary species for calcium(II) and zinc(II) ions resemble those of scandium(II) and copper(II) ions, respectively. The dissociative mechanism can operate for both the calcium(II) and zinc(II) ions. The associative mechanism, however, can operate only for the calcium(II) ion, and the zinc(II) ion has no meaningful stationary point on the reaction path. We also considered the effect of the electronic structures on the reaction mechanisms. We conclude as the following: The dissociative mechanism is operative for a water exchange of all members of the first transition series. An associative mechanism is expected for the water-exchange reaction of the earlier members, which have stable heptacoordinated species. The possibility of the operation of the associative mechanism depends on the existence of appropriate associative heptacoordinated species.
  • Yoshio Sugiyama
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1827-1831
    Published: 1997
    Released: June 15, 2006
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    Poly(methyl acrylate) radical and poly(methyl acrylate-α-d) radical, generated from the polymerization of methyl acrylate (MA) and methyl acrylate-α-d (MA-d) in the frozen (solid) state, have been investigated by Electron Spin Resonance (ESR). The α-position selective deuteration of poly(MA) radical made the shoulders of poly(MA) radical emerge as more clearly isolated peaks. Both ESR spectra of poly(MA) radicals and those of poly(MA-d) radicals were simulated for the conformational ratio 2.2 between a stable conformation and eclipsed conformations. The energy difference between the stable conformation and two eclipsed conformations was estimated to be 0.27 kcal mol−1 for poly(MA) radical in the thermal equilibrium solid state.
  • Maksudul M. Alam, Akira Watanabe, Osamu Ito
    1997 Volume 70 Issue 8 Pages 1833-1838
    Published: 1997
    Released: June 15, 2006
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    The photoinduced electron transfer between C70 and tetrathiafulvalene or bis(ethylenedithio)tetrathiafulvalene in polar and nonpolar solvents and their mixture has been investigated by nanosecond laser photolysis/transient absorption spectroscopy in the visible and near-IR regions. The transient absorption bands of the triplet state of C70 observed in polar solvents decayed upon addition of tetrathiafulvalenes accompanied by the appearance of the transient absorption bands of the radical anion of C70. In benzene, the quenching of the triplet state of C70 was observed without the appearance of the radical anion of C70 within a nanosecond laser pulse, suggesting a collisional quenching of the triplet state of C70 with tetrathiafulvalenes. The quantum yield for the formation of the radical anion via the triplet state of C70 was about 1 for tetrathiafulvalene in benzonitrile. The quantum yield decreased in less polar solvents. The back electron transfer rates were also evaluated in polar solvents.
  • Feng Wu, Toshihiko Shindo, Sadashi Sawamura, Takashi Sumiyoshi
    1997 Volume 70 Issue 8 Pages 1839-1842
    Published: 1997
    Released: June 15, 2006
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    Arene/chlorine atom π-complexes were generated by pulse radiolysis of a wide variety of substituted benzenes in carbon tetrachloride at room temperature. Upon laser flash photolysis of the π-complexes, intramolecular hydrogen abstraction was observed in times much shorter than the flash time (6 ns), with quantum yields between 0.05 and 0.18 depending on the sort and the number of the substituents but not on their positions. The effects of substituents on the photochemistry of arene/chlorine atom π-complexes were discussed in connection with the bond dissociation energy of the related atoms and with the structure of the π-complexes.
  • Cheng Zhi Huang, Ke An Li, Shen Yang Tong
    1997 Volume 70 Issue 8 Pages 1843-1849
    Published: 1997
    Released: June 15, 2006
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    This paper discusses the usefulness of resonance light-scattering spectroscopy (RLSS), which can be obtained by using an ordinary spectrofluorimeter, for the analysis of the suprahelical helixes of nucleic acids induced by 5,10,15,20-tetrakis[4-(trimethyammonio)phenyl]porphine (H2tapp). Depending on the acidity of the aqueous solution, the titled porphyrin has two species, [H2tapp]4+ and [H4tapp]6+. Both species can stack on appropriate conditions along the surface of nucleic acids in the mode of long-range assembly; and this leads to the formation of suprahelical helixes of nucleic acids. Enhanced resonance light-scattering signals can be observed for the porphyrin-induced suprahelical helixes of nucleic acids with the maximal resonance light scattering near to 432 nm for [H2tapp]4+ and near to 452 nm for [H4tapp]6+. The exciton splitting signals, which are generally associated with the aggregation of porphyrins, as described by molecular-exciton theory, are observed at 428 nm in the RLS spectra, analogous to the circular dichroism spectra when the molar ratio of [H2tapp]4+ to nucleic acids (R) is greater than 0.89. These results indicate that porphyrin–porphyrin interactions occur in the suprahelical helixes of nucleic acids.
  • Yukinari Sunatsuki, Masaaki Nakamura, Naohide Matsumoto, Fumiaki Kai
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1851-1858
    Published: 1997
    Released: June 15, 2006
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    Copper(II) and nickel(II) complexes with tetraanionic quadridentate ligands, K2[CuLn] and K2[NiLn] (n = 1, 2), have been prepared. We examined whether or not they can function as “ligand complexes”, where H4L1 = 1,2-bis(2-hydroxybenzamido)ethane and H4L2 = 1,2-bis(2-hydroxybenzamido)benzene. One of the ligand complexes, K2[NiL1]·2dmf·2H2O, crystallizes in the monoclinic space group P21/n with the cell dimensions of a = 15.34(8), b = 18.99(8), c = 18.86(5) Å, β = 100.2(3), V = 5406 Å3, and Z = 8. The ligand complex assumes a unique one-dimensional structure consisting of {[KO3][K(NiL1)O]}n as the repeating unit, where each K+ ion is surrounded octahedrally by six oxygen atoms with the distances of 2.672(2)—2.866(9) Å and all the oxygen atoms act as bridging group to K+ ion. Each of the precursor complexes can function as an electrically dianionic bidentate “ligand complex” and reacts with Cu(II) ion and terminal capping ligand (cap) such as 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), ethylenediamine (en), and 1,3-diaminopropane (tn) to give di-μ-phenoxo-bridged dinuclear Cu(II)–Cu(II) and Ni(II)–Cu(II) complexes with the general formula of [(Cu or Ni)LnCu(cap)]. The molar electrical conductivities of the dinuclear complexes measured in the DMF or DMSO solutions are essentially zero, indicating that the dinuclear structures are preserved in the solutions. The electrochemical measurements for a series of [CuL2Cu(cap)] (cap = bpy, phen, tn) demonstrated that the Cu(II/III) redox process of the {CuL2} site exhibits more positive potential (−0.04 — −0.09 V) than that of the mononuclear precursor complex (−0.288 V). One of the dinuclear complexes, [CuL2Cu(phen)(DMSO)], crystallizes in the orthorhombic space group Pna21 with the cell dimensions of a = 19.702(3), b = 15.847(3), c = 9.652(2) Å, V = 3013 Å3, and Z = 4. The complex consists of a discrete di-μ-phenoxo-bridged dinuclear structure, in which two copper(II) ions assume a square planar and square pyramidal coordination geometry and the bridging core of Cu2O2 is unequivalent, as found in the distances of Cu(1)–O(1) = 1.924(4) Å, Cu(1)–O(2) = 1.908(4) Å, Cu(2)–O(2) = 1.964(4) Å and Cu(2)–O(1) = 2.249(4) Å. The magnetic susceptibility is well reproduced with the antiferromagnetic coupling parameter of J = −82 cm−1 by the Bleaney–Boweres equation.
  • Kuninobu Kasuga, Kenichiro Asano, Liang Lin, Tamotsu Sugimori, Makoto ...
    1997 Volume 70 Issue 8 Pages 1859-1865
    Published: 1997
    Released: June 15, 2006
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    The title phthalocyanine (1) was prepared from 3-(pentan-3′-yloxy)phthalonitrile, of which a bulky substituent on the 3-position caused an exclusive formation of 1 out of the possible structural isomers.
    Complexes of magnesium(II), cobalt(II), nickel(II), copper(II), and zinc(II) were prepared by refluxing a DMF solution of 1 and corresponding metal(II) chlorides, and were characterized by the absorption and 1H NMR spectra as well as elemental analyses.
    Magnesium(II) and zinc(II) complexes showed a new band at the longer wavelength side of the Q band in chloroform, probably due to the formation of a face-to-face slipped dimer.
    Compound 1 and its magnesium(II), nickel(II), or copper(II) complex showed three ring-oxidative and reductive processes, and the zinc(II) complex showed four in dichloromethane in their cyclic voltammograms. The cobalt(II) complex showed five processes, two of which arose from a central cobalt(II) ion. The oxidation of the cobalt(II) ion occurred at a more negative potential in DMF.
    The crystal structure of the nickel(II) complex was determined by an X-ray analysis; substitution on the 1,8,15, and 22 positions of the ring by pentan-3-yloxy groups was confirmed. The molecules are stacked with a distance of 3.32 Å between the phthalocyanine rings.
  • Yasunobu Ohmiya, Nguyen Thi Kim Dung, Tatsuya Sekine
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1867-1873
    Published: 1997
    Released: June 15, 2006
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    Solvent extraction of silver(I) from aqueous 1 mol dm−3 Na(SCN, NO3) solutions, where the thiocyanate ion concentration was higher than 1 × 10−3 mol dm−3 and pH was 3, into chloroform and into 4-methyl-2-pentanone (MIBK) was studied in the presence of tetrabutylammonium ions (tba+) at 298 K. The extraction equilibria of the ion-pairs, tba+SCN and tba+NO3 into these solvents were also determined. The experimental data were well explained by extraction of tba+Ag(SCN)2 into chloroform and both tba+Ag(SCN)2 and Na+Ag(SCN)2 into MIBK and by formation of Ag(SCN)n1−n, where n was 2 to 4 in the aqueous phase. More than half of the initial amount of tba+ in the aqueous phase was extracted as tba+SCN and tba+NO3. The analysis of the extraction data of silver(I) should be made by taking the decrease in the tba+ concentration due to these extractions into account. No dissociation of the ion-pairs was found in chloroform but the extracted ion-pairs were partially dissociated in MIBK. In the presence of 1 × 10−3 mol dm−3 tba+ in the initial aqueous phase, the extraction of silver(I) was much better into MIBK than into chloroform under otherwise identical conditions. The extraction and dissociation constants of the above species and the stability constants of the anionic thiocyanate complexes of silver(I) in the aqueous phase were calculated.
  • Yong-Qi Song, Tomoaki Yuzuri, Hiroko Suezawa, Kazuhisa Sakakibara, Min ...
    1997 Volume 70 Issue 8 Pages 1875-1878
    Published: 1997
    Released: June 15, 2006
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    Photolyses of 2,6- and 2,4-difluorobromobenzenes in acetonitrile gave isomerized and brominated products in addition to 1,3-difluorobenzene produced by the dehalogenation. The reactions were compared with similar reactions of the corresponding chloro- and iodoarenes. In general, photolytic cleavage of the C–X bond of 2,6-difluorohalo(X)benzene was shown to proceed more easily than the corresponding 2,4-difluorohalo compound.
  • Tamon Okano, Yoshikazu Satou, Motoshi Tamura, Jitsuo Kiji
    1997 Volume 70 Issue 8 Pages 1879-1885
    Published: 1997
    Released: June 15, 2006
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    Lanthanoid triisopropoxides are active catalysts for aldol reactions. Aldehydes give the corresponding β-hydroxyaldehydes at low temperatures in good yields, whereas ketones are less reactive, but form condensation products at high temperatures. Exceptionally, γ- or δ-diketones easily undergo condensation to give five- and six-membered unsaturated ketones in high yields. The lanthanoid propoxides, catalyzing the Michael addition of ketones to α,β-unsaturated ketones, which give δ-diketones, are also good catalysts for the Robinson-type annelation. In these reactions, the catalytic activity of the lanthanum propoxide is higher than those of the heavy lanthanoid propoxides, and is almost comparable to that of sodium isopropoxide. Since aluminum triisopropoxide shows poor activity, the lanthanoid propoxides are considerably basic for trivalent metal alkoxides.
  • Jun Li, Jun Uzawa, Yoshiharu Doi
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1887-1893
    Published: 1997
    Released: June 15, 2006
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    Methyl (3R)-3-{[(3′R)-3′-hydroxybutanoyl]oxy}butanoate (MHBOB) has been prepared as a model compound of the hydroxy terminal part of poly[(R)-3-hydroxybutanoate] [P(3-HB)]; the NMR assignments and conformational analyses of the compound are reported. The NMR assignments of MHBOB were made by means of two-dimensional pulsed field gradient 1H–1H COSY and 1H–13C HMBC (heteronuclear multiple-bond correlation) spectroscopy. The conformational behavior of MHBOB generated by rotation about two CH2–CH bonds was investigated in chloroform and in aqueous solution at various temperatures by analysis of vicinal coupling in the 500-MHz 1H NMR spectra. In both chloroform and aqueous solution, the monomer unit adjacent to the methoxy group was found to adopt a similar conformational distribution to that of the P(3-HB) polymer backbone, in which the trans and gauche conformers were predominant, while the another gauche conformer was suppressed to almost zero. On the other hand, the monomer unit adjacent to the hydroxy group had a different conformational distribution relative to that of the other monomer unit, due to the formation of an intramolecular hydrogen bond between hydroxy and carbonyl groups. In chloroform, only the gauche conformer was predominant at temperatures between −60 and 57 °C, and even the fraction of another gauche conformer was higher than that of trans conformer at low temperatures below 0 °C. In aqueous solution, the fraction of gauche conformer was also higher than that of trans conformer, suggesting the formation of the intramolecular hydrogen bond. However, the formation of the intramolecular hydrogen bond in aqueous solution was not so strong as that in chloroform.
  • Bruce W. Baldwin, Takuji Hirose, Zhen-He Wang, Tadafumi Uchimaru, Ari ...
    1997 Volume 70 Issue 8 Pages 1895-1903
    Published: 1997
    Released: June 15, 2006
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    New derivatives of 1,3,5-trimethyl-r-1, c-3, c-5-cyclohexanetricarboxylic acid (Kemp’s triacid) showed high efficiency for alkaline earth and transition metal ion transport through a chloroform liquid membrane. Simple syntheses from Kemp’s triacid or its geometric isomer provided chelating agents with a tripodal binding site for metal cations. The tripodal binding site consisted of r-1, c-3-diaxial carboxyl group and a c-5-amide, ester, or C-methyl group. Alkaline earth metal transport was quite variable and sensitive to c-5-group changes. For transition metal transport, c-5-amide diacids gave high total transport efficiency. For c-5-ester or C-methyl diacids, complexation of smaller divalent cations was decreased, resulting in increased selectivity for large cations.
  • Toru Oba, Yukiko Masada, Hitoshi Tamiaki
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1905-1909
    Published: 1997
    Released: June 15, 2006
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    A new method for the large scale preparation of Pheophytin (=Pheo) b is presented. The difficulty in chromatographic isolation of Pheo a and b, tetrapyrrole pigments, from the large amount of plant extract was overcome by an increase in polarity of the pigment given by a selective modification of Pheo b. Treatment of plant extract containing both Pheo a and b, carotenoids, lipids, etc. with a mild reductant t-BuNH2BH3 induced selective reduction of the C7-formyl group of Pheo b, but left unaffected other carbonyl moieties of the molecules. The resulting compound 7-hydroxymethyl-Pheo b was readily separated from intact Pheo a by silica gel column chromatography. Pure Pheo b was obtained by oxidation of the 7-hydroxymethyl-Pheo b with pyridinium chlorochromate. One of the reasons why the present method is superior to the previous ones is that Pheo a was obtained simultaneously as an intact form. Another is the utility of the intermediate compound, 7-hydroxymethyl-Pheo b: as the starting material for syntheses of various compounds as well as a model of ingredients in the photosynthetic systems, such as a light-harvesting apparatus of green photosynthetic bacteria.
  • Kazunari Yoshizawa, Takehiro Ohta, Tokio Yamabe
    1997 Volume 70 Issue 8 Pages 1911-1917
    Published: 1997
    Released: June 15, 2006
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    Dioxygen activation on the dicopper enzyme model was studied using fragment molecular orbital (FMO), Walsh-diagram, and molecular orbital overlap population (MOOP) analyses within the framework of the extended Hückel method. A dicopper peroxo model complex with a μ-η2 : η2-O2 binding mode is distorted to a corresponding dioxo complex with a Cu2(μ-O)2 diamond core along an assumed reaction coordinate describing O–O bond cleavage. FMO and Walsh-diagram analyses have clarified the bonding and orbital interactions between the dicopper active site and dioxygen. While the πg* orbitals of dioxygen begin with two electrons, in the early O2 binding stages two other electrons are effectively transferred from the copper d-block orbitals to O2. Qualitative calculations show that O–O bond cleavage should proceed with no cost of activation energy on the dicopper active site of actual enzyme systems.
  • Tadao Uyehara, Toshihiro Inayama, Takanobu Kobari, Yuuko Kimura, Norik ...
    1997 Volume 70 Issue 8 Pages 1919-1921
    Published: 1997
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    The treatment of a bicyclo[3.2.1]oct-6-en-2-one (3) with Amberlyst® (H-15) in boiling benzene gave a mixture of bicyclo[3.2.1]oct-3-en-2-one (5) and bicyclo[2.2.2]oct-5-en-2-one (6). The ratio of 5 to 6 was influenced by the substituent at the C-1 position of the ketone 3. Chiral ketones 3 were transformed into the chiral α,β-unsaturated ketones 5 without racemization.
  • Hiroyuki Higuchi, Kenji Shimizu, Makoto Takeuchi, Juro Ojima, Ken-ichi ...
    1997 Volume 70 Issue 8 Pages 1923-1933
    Published: 1997
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    Tris(octaethylporphyrin)s, in which two octaethylporphyrin (OEP) rings are connected with vinylene groups at α,γ- and α,β-meso positions of the central OEP ring, were synthesized. The tris(OEP)s have similar conformational and configurational structures to the corresponding vinylene group-connected bis(OEP). Examination of both 1H NMR and electronic absorption spectra of the tris(OEP)s showed the behavior reflecting the highly symmetrical structure and the mutual interaction between the three OEP rings through the vinylene linkages.
  • Yoshito Tobe, Shinji Saiki, Hirokazu Minami, Koichiro Naemura
    1997 Volume 70 Issue 8 Pages 1935-1942
    Published: 1997
    Released: June 15, 2006
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    [6](1,4)Naphthalenophane (1a), [6](1,4)anthracenophane (2a), and their peri-substituted derivatives 1b, 1c, and 2b were synthesized from 8-bromo[6]paracyclophane (4) by a benzoannelation method. The 1H NMR spectral properties of 1b, 1c, and 2b as well as the X-ray crystallographic structure analysis of 1b indicate that their bridged aromatic rings are more distorted than those of the corresponding parent systems, 1a and 2a. Thermally reversible photochemical isomerization of 1b and 2b took place readily, giving the corresponding Dewar valence isomers, 10b and 11b.
  • Hayao Matsuhashi, Satoshi Asai, Kazunori Hirabayashi, Yasuo Hatanaka, ...
    1997 Volume 70 Issue 8 Pages 1943-1952
    Published: 1997
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    The cross-coupling reaction of allylic carbonates with organosilanes was found to proceed without fluoride ion activation under mild conditions by using a coordinatively unsaturated palladium complex as a catalyst. The reaction was assumed to proceed through an allylpalladium alkoxide derived from the allylic carbonate substrate and a palladium(0) species, the alkoxo ligand activating the organosilicon reagent. Likewise, diene monoxides also underwent cross-coupling with alkenyl- and arylfluorosilanes in moderate to high yields.
  • Yukiyasu Chounan, Hiroshi Horino, Toshiro Ibuka, Yoshinori Yamamoto
    1997 Volume 70 Issue 8 Pages 1953-1959
    Published: 1997
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    In order to evaluate the electron transfer ability of organocopper reagents, the reactions of appropriate Michael acceptors with methyl- and butylcopper reagents were investigated. The reaction of trimethyl ethylene-1,1,2-tricarboxylate (1a) with methylcopper reagents gave a mixture of the conjugate adduct 2a and reduction product 3a in good to high yields. The ratio of 2a and 3a varied with the copper species and decreased in the following order: MeCu(CN)Li > MeCu > Me2Cu(CN)Li2 >> Me2CuLi > Me3CuLi2. It was confirmed by 13C NMR studies and oxidation experiments of the intermediate copper species that the reduction product 3a was produced via an electron transfer process and that the conjugate adduct 2a was afforded through a nucleophilic attack of MeCuILn. Consequently, the electron transfer ability of methylcopper reagents is in the following order: Me3CuLi2 > Me2CuLi >> Me2Cu(CN)Li2 > MeCu > MeCu(CN)Li. By similar experiments using 3-cyclopropyl-2-methoxycarbonyl-3-phenyl-2-propenoate (9) as a Michael acceptor, we concluded that the electron transfer ability of butylcopper reagents is in the order of Bu2CuLi > BuCu(CN)Li ≈ Bu2Cu(CN)Li2 > BuCu, and that its ability of butylcopper reagents is higher than that of the corresponding methylcopper reagents.
  • Noriko Chikaraishi-Kasuga, Ken-ichi Onoue, Yutaka Osawa, Seiichi Nakah ...
    1997 Volume 70 Issue 8 Pages 1961-1968
    Published: 1997
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    Two derivatives of ω-hydroxy carboxylic ionophore 2-[[2-[2-[2-[2-[2-[2-[2-(2-hydroxyethoxy)phenoxy]ethoxy]phenoxy]ethoxy]phenoxy]ethoxy]phenoxy]methyl]benzoic acid 1, 2-[[3-[2-[2-[2-[2-[2-[3-(2-hydroxyethoxy)-2-naphthyloxy]ethoxy]phenoxy]ethoxy]phenoxy]ethoxy]-2-naphthyloxy]methyl]benzoic acid 2 and 2-[[3-[2-[2-[2-[3-[2-[2-(2-hydroxyethoxy)phenoxy]ethoxy]-2-naphthyloxy]ethoxy]phenoxy]ethoxy]-2-naphthyloxy]methyl]benzoic acid 3, were prepared. Both compounds exhibited high K+ selectivity over Na+, as did 1. The structures of the Rb salt of 2 and the K salt of 3 were determined by single-crystal X-ray analyses. Both ionophores formed psuedocycles by a head-to-tail hydrogen bond between the hydroxy and carboxylato groups and enclosed each cation like the seam of a tennis ball to make lipophilic complexes. However, the three-dimensional structures of the two hydrophobic salts differed from each other in spite of the similarity of the primary structures, which might be due to the interaction of the aromatic rings.
  • Hajime Nagano, Tomoko Nagasawa, Masako Sakuma
    1997 Volume 70 Issue 8 Pages 1969-1976
    Published: 1997
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    Highly Branched polyprenols, {(6E)-2-[(2E)-3,7-dimethyl-2,6-octadienyl]-7,11-dimethyl-3-methylene-6,10-dodecadien-1-ol and (6E,10E)-2-[(2E,6E)-3,7,11-trimethyl-2,6,10-dodecatrienyl]-7,11,15-trimethyl-3-methylene-6,10,14-hexadecatrien-1-ol}, were synthesized (1) from diethyl malate, geranyl bromide, and homogeranyl iodide, and (2) from ethyl acetoacetate and geranyl (or farnesyl) bromide. These alcohols were transformed into disodium phosphates, which have been postulated to be primitive lipids in the evolution of membranes.
  • Eiji Yashima, Pennapa Sahavattanapong, Chiyo Yamamoto, Yoshio Okamoto
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1977-1984
    Published: 1997
    Released: June 15, 2006
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    4-Chloro- and 4-bromophenylcarbamates of maltooligosaccharides (n = 5, 6, and 7) were prepared and their chiral recognition abilities as a chiral stationary phase for HPLC were evaluated. The maltooligosaccharides carbamates exhibited a characteristic chiral recognition depending on the racemates and resolved several racemates in HPLC. The enantioselectivity as well as elution order of enantiomers on the maltooligosaccharide derivatives were similar to those on the corresponding amylose phenylcarbamte derivatives. The maltooligosaccharides also showed chiral discrimination for some racemates in NMR; the proton resonances of racemates, such as trans-stilbene oxide, benzoin, and 1,2,2,2-tetraphenylethanol were split into a pair of peaks due to the enantiomers. A good correlation between the NMR results and the chromatographic elution order was observed for most racemates. An enantiomeric guest, bilirubin, was also chirally discriminated by the maltooligosaccharides in chloroform to show an induced CD. The structures of the maltohexaose derivatives were examined by molecular mechanics and molecular dynamics simulations.
  • Elly L. Uzunova, Ivan G. Mitov, Dimitar G. Klissurski
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1985-1993
    Published: 1997
    Released: June 15, 2006
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    Pyroaurite-like carbonate hydroxide precursors Co1−xFex(CO3)x/2(OH)2·nH2O, where x varies in the range 0.25 ≤ x ≤ 0.75, yield cation deficient mixed oxides with particle dimensions in the nano-scale range. The thermal decomposition and spinel structure formation processes have been studied by thermal analysis and IR spectroscopy, revealing an intermediate of hydroxide oxide type. Mesoporous mixed oxides with cubic spinel structure were synthesised at 300—400 °C with significant contribution of small pores of radii <200 Å. Oxygen desorption from cobalt ferrite, synthesised at 350 °C, suggests the existence of a high content of extraframework oxygen. The temperature-programmed reduction (TPR) with hydrogen occurs in one stage for all cobalt/iron compositions. The peak maxima shift to higher temperatures and a broadening is observed with increasing the iron content. Partly inverse cation distributions of the spinel ferrites are deduced from the Moessbauer spectra.
  • Mamoru Ai, Kyoji Ohdan
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 8 Pages 1995-1999
    Published: 1997
    Released: June 15, 2006
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    Iron phosphates with a P/Fe atomic ratio of 1.2 were found to be effective as catalysts for a vapor-phase oxidative dehydrogenation of glycolic acid to glyoxylic acid. The effects of the reaction variables on the conversion and selectivity were studied. The optimum reaction temperature was around 240 °C and the optimum feed rate of oxygen was in the range of 10 to 25 mmol h−1 when the feed rate of glycolic acid was 12.3 mmol h−1. The reaction was not affected by a variation in the feed rate of water vapor in the range of 86 to 480 mmol h−1. The selectivity to glyoxylic acid remained unchanged at 74 mol% with an increase in the conversion of glycolic acid up to 70%; the highest yield of glyoxylic acid was 56.5 mol% at the conversion of 80%.
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