Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 69 , Issue 9
Showing 1-34 articles out of 34 articles from the selected issue
  • Taro Saito, Hideo Imoto
    1996 Volume 69 Issue 9 Pages 2403-2417
    Published: 1996
    Released: June 28, 2006
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    Trinuclear, tetranuclear, hexanuclear, and dodecanuclear chalcogenide cluster complexes of chromium, molybdenum, tungsten, and rhenium have been synthesized and their molecular and electronic structures have been characterized. The structure-cluster valence electron relationships are analyzed and a new isoelectronic analogy is proposed.
  • Toshie Harazono, Yukiyo Hiroyama, Tokuko Watanabe
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2419-2423
    Published: 1996
    Released: June 28, 2006
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    11B- and 13C-solid state NMR of boron carbide with different isotope ratios, B4C(11B/10B = 80.42/19.58; natural abundance isotope) and 11B4C(11B/10B = 99.5/0.5; 11B enriched sample), has been investigated. The linewidth of the icosahedral B (6h1and 6h2) in 11B-static NMR signal in 11B4C was greater in 11B4C than in B4C, which indicates that the B–B dipole–dipole interaction is the main mechanism for the broadening of the 11B-static NMR signal. The quadrupole coupling constant calculated from the signal position of (±1/2 ↔ ±3/2) transition was about 0.1 MHz. 11B-MAS spectra revealed the presence of at least two additional B sites (37 ppm and near −60 ppm) besides the icosahedral B sites (−6 ppm).
  • Yoshiki Ohgo, Yuji Ohashi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2425-2433
    Published: 1996
    Released: June 28, 2006
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    The crystal of [(R)-1-cyanoethyl][bis(dimethylglyoximato)](3-hydroxypyridine)cobalt(III) benzene solvate showed racemization along with a retention of the single-crystal form upon exposure to a fluorescent lamp. The crystal data before irradiation are as follows: [Co(C3H4N)(C4H7N2O2)2(C5H5NO)] ·2C6H6, F.W. = 594.6, triclinic, P1, Z = 2, a = 11.646(3), b = 13.267(4), c = 11.303(3) Å, α = 102.57(2), β = 101.27(2), γ = 113.38(2)°, V = 1485.2(9) Å3, Dx = 1.33 Mg m−3, μ(Mo ) = 0.624 mm−1, F(000) = 624, and T = 296 K. The structure was solved by the direct method and refined to R = 0.067, wR2 = 0.180. Upon exposure to a fluorescent lamp, the cell dimensions were gradually changed, and became significantly small after 150 h of irradiation. The cell dimensions became as follows: a = 11.596(4), b = 13.287(3), c = 11.297(2) Å, α = 102.51(2), β = 101.26(2), γ = 113.37(2)°, and V = 1481.1(8) Å3. The analysed structure showed that a crystallographic inversion center appeared between the two molecules, and that the space group changed from P1 to . The 1-cyanoethyl groups of the two molecules were transformed to disordered racemates. In the process of racemization, the cyano and methyl groups were exchanged, although the methyl group has been exchanged with hydrogen in the related crystals so far observed. The racemic crystal obtained from a solution showed approximately the same structure as that by photoirradiation. The reason why such a new mode of racemization occurred was clearly explained by the size and shape of the reaction cavities for the two 1-cyanoethyl groups in the structure before irradiation.
  • Tadayoshi Sakata
    1996 Volume 69 Issue 9 Pages 2435-2446
    Published: 1996
    Released: June 28, 2006
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    The quantum theory of electron transfer reactions at metal electrodes was studied. The obtained potential dependence of the electron transfer rate in the weak coupling case resembles the Butler–Volmer equation of classical electrochemistry. The volcano-shaped dependence of the hydrogen exchange current on the adsorption energy of hydrogen on various metals was explained microscopically, based on this theory. The mechanism of hydrogen evolution was also explained microscopically based on this theory. The exchange current density for hydrogen evolution at Pt electrode calculated quantitatively agreed well with the experimental value.
  • Narayanasamy Rajendiran, Meenachisundram Swaminathan
    1996 Volume 69 Issue 9 Pages 2447-2452
    Published: 1996
    Released: June 28, 2006
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    Absorption and fluorescence spectra of Bis(4-aminophenyl)ether (DADPE) have been studied in different solvents and at various acid concentrations. The results are compared with the spectral data of 4-Aminodiphenyl ether (ADPE). The fluorescence spectra of DADPE are blue shifted relative to that of ADPE in polar and hydrogen-bonding solvents. A small, but unusual, red shift is observed in the fluorescence spectrum of the monocation relative to that of DADPE in water. These observations reveal that the effect of two amino groups in polar solvents is less than that of one amino group in the excited singlet state. The abnormally red-shifted fluorescence with a peak at around 422 nm at pH 3.5 is due to a dication-solvent exciplex. The formation of the dication-solvent exciplex leads to an excited state equilibria quite different from that in the ground state.
  • Yoshiya Kawabata, Tomoyuki Itaya, Yuki Sasaki, Hiroshi Ochiai, Kazuyos ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2453-2459
    Published: 1996
    Released: June 28, 2006
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    Charge-transfer (CT) complexations between 1-pyrenesulfonate ion (PyS; donor) and 9,10-anthraquinone-2-sulfonate ion (2-AQS; acceptor), and between anthracene-2-sulfonate ion (ACS; donor) and 2-AQS ion around the cationic polymers were studied by means of absorption and fluorescence spectroscopies as well as molecular-orbital calculations. The cationic polymers used in this study were poly(allylammonium) (PAAH+) and poly(1,1-dimethyl-3,5-dimethylenepiperidinium) (PDDP+). When solutions included only donor and acceptor molecules at low concentration, such as solutions of PyS (1 × 10−4 M)/2-AQS (1 × 10−4 M) and ACS (1 × 10−4 M)/2-AQS (1 × 10−4 M), they did not show any CT complex formation. However, the addition of polymers to these solutions exhibited charge-transfer absorption bands (CT band). A continuous variation method for CT bands of Na+PyS/Na+2-AQS in both PAAH+Cl and PDDP+Cl systems showed that a 1 : 1 type (PyS : 2-AQS) complex preferentially formed in the vicinity of these polyions. On the other hand, in the Na+ACS/Na+2-AQS system, a 1 : 2-type (ACS : 2-AQS) complex preferentially formed around PAAH+ and a 1 : 1-type complex formed around PDDP+. By comparing these results with our previous study between 9,10-dimethoxyanthracene-2-sulfonate and 2-AQS in aqueous solution with the same polymers, it has become clear that the stoichiometries of the CT complexes and the peak positions of the observed CT bands are dependent upon the varieties of donor molecules. Molecular-orbital calculations have shown that there is a linear relationship between the calculated energy levels of the highest occupied molecular orbital (HOMO) of the donor molecules and the energies of the observed CT bands; that is, the donor molecule with a higher HOMO energy has the lower energy of the CT band.
  • Fumihiko Mukae, Hiroyuki Takemura, Kô Takehara
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2461-2464
    Published: 1996
    Released: June 28, 2006
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    2,3-Dichloro-1,4-naphtoquinone (NQ) was anchored to a gold electrode surface through the self-assembled monolayers of aminoalkanethiols (AAT, HS(CH2)nNH2: n = 2, 5, and 8). The effect of the alkyl chain length of the AAT monolayer, which also acts as the spacer between the NQ molecule and the gold electrode surface, on the redox behavior of the immobilized NQ has been studied by using a voltammetric technique. The surface coverage of the anchored NQ was estimated to be 3.8 × 10−10 mol cm−2 in the case that 2-aminoethanethiol (HS(CH2)2NH2) was used as the monolayer constituent. The electron-transfer rate constant, ket, associated with the redox process of anchored NQ decreased from 9.7 s−1 at n = 2 to 0.78 s−1 at n = 8, with increasing the chain length of the AAT monolayer, though the redox potential of NQ was scarcely affected by the chain length. The tunneling barrier coefficient, β, of the electron transfer was estimated to be 0.36 Å−1, from the observed linear relationship between the ket value and the monolayer chain length.
  • Sadakatsu Nishikawa, Sachiko Yamaguchi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2465-2468
    Published: 1996
    Released: June 28, 2006
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    Ultrasonic absorption coefficients in aqueous solutions containing β-cyclodextrin and alcohols (ethanol and 1-propanol) have been measured in the frequency range from 3 to 220 MHz at 25 °C. Although a single relaxational absorption has been observed in solution with β-cyclodextrin and 1-propanol, it has not been found when the alcohol is ethanol. From the concentration dependence of the ultrasonic relaxation parameters, the cause of the relaxational absorption has been attributed to the perturbation of an equilibrium associated with the 1 : 1 complex formation (complexation) between β-cyclodextrin and 1-propanol. The rate and equilibrium constants as well as the standard volume change were determined for the complexation reaction of β-cyclodextrin and 1-propanol. The equilibrium constant determined in this study was found to be very consistent with the reported value for β-cyclodextrin and 1-propanol. The kinetic process for complexation between β-cyclodextrin and popular alcohols is discussed in relation to the sizes of the guest molecules.
  • Sanyo Hamai, Akira Hatamiya
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2469-2476
    Published: 1996
    Released: June 28, 2006
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    In aqueous solutions, β-cyclodextrin (β-CD) has been found to form inclusion complexes with 1-methylnaphthalene, 1-ethylnaphthalene, 1-(chloromethyl)naphthalene, and 2-ethylnaphthalene. Addition of β-CD to aqueous solutions of 1-methylnaphthalene and 2-ethylnaphthalene has resulted in the observation of the excimer fluorescence of each compound. From simulations of the observed excimer fluorescence intensities of 1-methylnaphthalene and 2-ethylnaphthalene, the excimer fluorescence is concluded to be due to a 2 : 2 β-CD–alkylnaphthalene inclusion complex. In the cases of 1-ethylnaphthalene and 1-(chloromethyl)naphthalene, the excimer formation within the β-CD cavities seems to be prohibited due to the steric hindrance caused by a substituent, although the 2 : 2 β-CD–alkylnaphthalene inclusion complex is likely to be formed. Equilibrium constants for the formation of these 1 : 1 and 2 : 2 inclusion complexes have been evaluated from the monomer and excimer fluorescence intensity changes with β-CD concentration.
  • Yoshihisa Matsui, Shuichi Tokunaga
    1996 Volume 69 Issue 9 Pages 2477-2480
    Published: 1996
    Released: June 28, 2006
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    The 1H NMR chemical shifts (δ’s) of the tetramethylammonium ion (TMA), methanol, and HDO, measured by using sodium 2,2-dimethyl-2-silapentane-5-sulfonate as an external reference, showed upfield shift with increasing concentration (c) of carbohydrates such as cyclodextrins (CD’s) and methyl glucopyranoside. The plots of δ vs. c gave straight lines with slopes proportional to the number of glucopyranoside residues involved in the carbohydrates, indicating that the upfield shifts are not due to inclusion phenomena but to a change in water structure with the formation of hydrogen bonds between carbohydrates and D2O. When an internal reference, TMA, was used instead, the 1H NMR signals of such organic molecules as acetonitrile, ethanol, 1-propanol, and 1-butanol showed uniform downfield shifts upon adding α-CD. The curve-fitting analysis of the plots of δ vs. c gave binding constants in agreement with those determined by other methods. It is concluded that the internal reference method is more reliable than the external one.
  • Kinya Iijima, Mayumi Matsuoka, Takeshi Sakaizumi, Osamu Ohashi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2481-2486
    Published: 1996
    Released: June 28, 2006
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    The molecular structures of two rotational isomers (anticlinal and synperiplanar forms) of gaseous (E)-propionaldehyde oxime have been determined from electron diffraction and microwave spectroscopic data. The anticlinal form is more stable by 0.15 ± 0.10 kcal mol−1 than the synperiplanar form. The molecular parameters of the anticlinal form are rg(C1–C2) = 1.552(3) Å, rg(C2–C3) = 1.493(2) Å, rg(C3=N) = 1.284(2) Å, rg(N–O) = 1.429(2) Å, ∠C1C2C3 = 111.5(1)°, ∠C2C3N = 119.0(3)°, and ∠C3NO = 109.4(2)°. The ∠C2C3N, ∠C1C2C3, and rg(C3–N) values of the synperiplanar form (122.6(6)°, 112.6(6)°, and 1.291(3) Å, respectively) are not equal to those of the anticlinal form.
  • Tomoyuki Akutagawa, Gunzi Saito, Masami Kusunoki, Ken-ichi Sakaguchi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2487-2511
    Published: 1996
    Released: June 28, 2006
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    Studies of the crystal structures and formation of a charge-transfer (CT) complex proved that 2,2′-bi-1H-imidazole (H2BIM0) forms a new system concerned with the interplay of proton-transfer (PT) and electron-transfer (or charge-transfer (CT)) interactions. X-Ray crystal analyses of newly isolated species, 2-(2-1H-imidazolyl)-1H-imidazolium (H3BIM+) and 2,2′-bi-1H-imidazolium (H4BIM2+), revealed the formation of strong hydrogen bonds along the side-by-side direction of the molecular plane. CT complexes of H3BIM+ and H4BIM2+ with the 7,7,8,8-tetracyanoquinodimethane derivatives (TCNQs) were synthesized by a method metathesis, and the crystal structure of (H3BIM+)2(TCNQ)2(TCNQ0) was determined. During CT complex formation, the initial simple protonated states of [H3BIM+] or [H4BIM2+] changed to different ones, for example, [H4BIM2+]x[H3BIM+]1−x, [H3BIM+]x[H2BIM0]1−x, and H2BIM0. According to the protonated states of the H2BIM system, the formal charge of the TCNQs in the CT complexes varies from completely ionic, partial CT, to neutral. The mechanism of these complex formations was explained by differences in the acidities between the TCNQ anion radicals (TCNQs−•) and H3BIM+ or H4BIM2+. Higher acidities of H3BIM+ and H4BIM2+ than the TCNQs−• induce the following PT reaction: H3BIM+ (or H4BIM2+) + TCNQs−• → H2BIM0 (or H3BIM+) + HTCNQ. The isolation of HTCNQ was a failure due to the following disproportional reaction: 2HTCNQ → TCNQ0 + H2TCNQ0. However, the formation of the 1,4-benzenedimalononitrile (H2TCNQ0) was confirmed by an analysis of the residual compounds after complex formation. Although the electronic absorptions of TCNQ complexes indicated both the partial CT state of TCNQ and a segregated stacking manner, semiconductive characters were observed. In a crystal of (H3BIM+)2(TCNQ)2(TCNQ0), the H3BIM+ formed a planar dimer connected by two N–H···N hydrogen bonds, and TCNQ molecules existed as a charge-separated state with segregated trimer stacks. These dimer and TCNQ stacks were tightly connected by both N–H···N≡C hydrogen bonds, which spread into the overall crystal, and by the CT interaction. For the PT and CT system, we propose a synthetic strategy based on the redox potentials and acid dissociation constants.
  • Yong Li
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2513-2523
    Published: 1996
    Released: June 28, 2006
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    Crystallographic and spectroscopic investigations were carried out for Cu(II) complexes of 15-crown-5 (15C5) and 4′-substituted benzo-15-crown-5 (B15C5) derivatives. X-Ray diffraction measurements were performed for two single crystals of [Cu(15C5)(H2O)2](ClO4)2 and [Cu(B15C5)(H2O)2](ClO4)2, obtained from 60% HClO4 solutions. The results of the X-ray analysis demonstrated that these complexes take a seven-coordinate pentagonal bipyramidal geometry, in which the copper ion is located in the center of the crown ether cavity with two water molecules at the axial positions. The ESR spectra observed for these complexes in 60% HClO4 exhibited the characteristic g-anisotropy (gz < gx, gy), leading to an electronic configuration of a 3dz2 ground-state doublet. ESR and electronic absorption measurements were made for Cu(II) complexes of 4′-substituted B15C5 in systems of BF3–ether–water and of dry CHCl3 in which complexes having two chloride ions at the axial positions were produced. Although these systems showed the same remarkable substituent effects, clear differences were detected between them, attributable to the different axial ligands. The results of an extended Hückel MO calculation performed for the models of these complexes provide qualitative explanations for the experimental results.
  • Soichi Otsuki, Takahisa Taguchi
    1996 Volume 69 Issue 9 Pages 2525-2531
    Published: 1996
    Released: June 28, 2006
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    A phenothiazone dye, 7-dimethylamino-3H-phenothiazin-3-one, was investigated as an optical probe in homogeneous media. Two absorption bands appeared in aprotic solvents and dioxane–water and exhibited different dependencies on the solvent polarity/polarizability scale, π*. Both of the bands were quite different from that corresponding to the aggregated molecules or the protonated species of the dye. These results suggest the existence of two ground-state species with non-twisted and twisted conformations of the 7-amino group. The π* dependencies of the fluorescence maxima and the rate constants of the fluorescence decays showed three types of behavior in dioxane–water. The Lippert–Mataga plot of the spectral shift was interpreted by assuming two types of behavior in aprotic solvents. These facts suggest that the fluorescence comes from three emitting states which exist in fast equilibria. The strong polarity dependencies and the long wavelengths of the absorption and fluorescence, the large Stokes shift, and the appreciable fluorescence quantum yield make the dye useful as an optical probe of the polarity of a variety of microenvironments.
  • Kazuo Nomura
    1996 Volume 69 Issue 9 Pages 2533-2537
    Published: 1996
    Released: June 28, 2006
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    In the perfluoro carboxylate cation exchange membrane–aqueous electrolyte systems, two steps appeared in the time course of the membrane potential in response to a pH jump in the external solution. LiCl, NaCl, and KCl were used as the electrolytes. According to the experimentally observed curve of the potential transient, the membrane potential was divided in two portions: the potential difference at the membrane/solution interface (Donnan potential) and the intramembrane diffusion potential. It was found that the differences among the total membrane potentials for three kinds of alkali metal ion systems were mainly attributed to the generation process of the diffusion potential within the membrane. The pH dependencies of the Donnan potential and intramembrane diffusion potential were calculated on the basis of a theory starting at the Nernst–Planck equation for the ion diffusion. Calculations were carried out taking into account the association/dissociation reaction of hydrogen ions and ion exchange groups and the heterogeneous structure of the membrane. By fitting the theoretical equations to the experimental results, the best-fitting values of relative mobility of ion and the dissociation constant of COOH group in the membrane were obtained.
  • Takayoshi Suzuki, Akira Morikawa, Kazuo Kashiwabara
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2539-2548
    Published: 1996
    Released: June 28, 2006
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    Here are described several new nickel(II), palladium(II), and platinum(II) complexes of bis(chelate)-type with didentate phosphine ligands having an amino or thioether donor group: Me2PCH2CH2NH2 (edmp), Ph2PCH2CH2NH2 (edpp), Me2PCH2CH2NMe2 (dmedmp), or Me2PCH2CH2SMe (mtdmp). Bis(tetrafluoroborate) salts of [M(P–N or S)2]2+ (M = Ni, Pd, and Pt; (P–N or S) = the ligands above) have been prepared and the geometrical structures determined by NMR spectroscopy. All the palladium(II) complexes prepared in this study are cis-isomers, in contrast to the analogous Me2PCH2CH2S (dmsp) complex (trans-[Pd(dmsp)2]), which indicates that the anionic phosphine-thiolate ligand prefers the trans geometry more than the neutral phosphine-amine or -thioether ligand does. The dichloride salts of the bis(edmp) complexes, cis-[M(edmp)2]Cl2 (M = Ni (4a), Pd(5a), and Pt(6a)), and those of the bis(edpp) complexes have been obtained as crystals, while the corresponding salts of dmedmp, mtdmp, and 8-(dimethylphosphino)quinoline complexes can not be isolated due to their oily properties. Further, addition of LiBF4 to a methanolic solution of 4a, 5a, or 6a gives exclusively a precipitate of the chloride tetrafluoroborate salt, cis-[M(edmp)2]Cl(BF4) (M = Ni (4c), Pd(5c), or Pt(6c)). The crystal structures of 4a, 5c, and 6a determined by X-ray analyses indicate a weak (not strong enough to form a five-coordinated complex) interaction between cis-[M(edmp)2]2+ and Cl anion. The average M–N bond lengths in 4a, 5c, and 6a are considerably longer than those in the corresponding 1,2-ethanediamine complexes, owing to the strong trans influence of the –PMe2 group in edmp. The order of strength of the trans influence among NiII, PdII, and PtII triad metal series is non-periodical: NiII < PtII < PdII. This order is similar to the order among CoIII, RhIII, and IrIII triad metal series found in our previous study on fac-[M′(edmp)3]3+ (M′ = CoIII, RhIII, and IrIII) complexes.
  • Masakazu Hirotsu, Masaaki Kojima, Kiyohiko Nakajima, Setsuo Kashino, Y ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2549-2557
    Published: 1996
    Released: June 28, 2006
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    Cobalt(II) complexes containing tetradentate Schiff base ligands with phenyl substituents, [Co(Schiff base)], have been prepared and the electrochemical properties are reported. The crystal structure of [Co{7-Phsal-(rac)-stien}], where the Schiff base ligand was derived from 2-hydroxybenzophenone and (rac)-1,2-diphenylethylenediamine, has been determined by X-ray structure analysis. Crystal data: monoclinic, P21/n, a = 13.956(2), b = 14.703(2), c = 17.808(3) Å, β = 112.21(1)°, V = 3383.0(9) Å3, Z = 4, and R = 0.052 and Rw = 0.039 for 3976 unique reflections with I > 3σ(I). The two phenyl groups in the N–N chelate moiety are in the axial positions and block the apical sites. In this complex, the redox potential of the Co(III)/Co(II) couple is 0.20 V vs. Ag/Ag+ in acetonitrile and becomes more positive by ca. 300 mV than that for [Co(salen)]. This large positive shift is attributed to the steric effect of the two axially disposed phenyl groups. The redox potentials of the analogous cobalt(II) Schiff base complexes, where (meso)-1,2-diphenylethylenediamine and (R)-1-phenylethylenediamine were used as a diamine, are also explained in terms of the steric effect of the phenyl substituents. The corresponding cobalt(III) Schiff base complexes with two additional axial ligands, [Co(Schiff base)(L)2]ClO4 (L = imidazole (im), 1-methylimidazole (Meim)), have been prepared. The steric interaction between the phenyl groups on the N–N chelate moiety and the axial ligands is discussed based on the X-ray structure, the circular dichroism (CD) spectra, and the 1H NMR spectra. The crystal structure determination of [Co{sal-(meso)-stien}(Meim)2]ClO4 has been performed. Crystal data: monoclinic, P21/c, a = 10.789(2), b = 20.512(3), c = 15.330(2) Å, β = 99.88(1)°, V = 3342.3(8) Å3, Z = 4, and R = 0.051 and Rw = 0.049 for 3414 unique reflections with I > 3σ(I). In order to study the steric effect of the phenyl substituents, the [Co(Schiff base)(L)2]ClO4 complexes have been prepared using (R)-1,2-propanediamine as a diamine. The different behavior shows that the interaction between the phenyl groups is sensitive to the orientation.
  • Kuninobu Kasuga, Tsutomu Idehara, Makoto Handa, Yoichi Ueda, Takaji Fu ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2559-2563
    Published: 1996
    Released: June 28, 2006
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    A few (alkoxo)(subphthalocyaninato)boron(III) complexes, [BX(subpc)] (X = OMe, OEt, OBut, and OPh), were prepared and characterized. The molecular structure of [B(OEt)(subpc)] was determined by an X-ray structure analysis; the boron atom is situated 0.642 Å upward from the triangle plane of three isoindoline nitrogen atoms. The geometry of the boron atom is distorted tetrahedral, and the complex shows a wine-glass shape. The mass spectra showed that a part of the hydrogen atoms of the subphthalocyanine ring are displaced by the halogen atoms of boron trihalide or solvents. The complexes showed strong absorption bands at around 560 (Q band) and 300 nm (B band) in chloroform, respectively. The complexes decomposed in solution under irradiation with visible light. The first oxidative or reductive half-wave potential of [B(OEt)(subpc)] was observed at 1.06 V (vs. SCE) or −1.11 V, respectively.
  • Yasuki Yoshimura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2565-2571
    Published: 1996
    Released: June 28, 2006
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    The salt effect on fac-tris(aniono)cobalt(III) of α-amino acids (fac-[Co(amino acidato)3]), such as D-proline and glycine, was examined by determining its solubility in various aqueous salt solutions. For a comparison, the solubilities of tris(2,4-pentanedionato)cobalt(III) ([Co(acac)3]) and L-phenylalanine (L-phalaH) were also determined. The enthalpy (ΔHs) and entropy of dissolution (ΔSs) were estimated from the temperature dependence of the solubility. While NaCl and Na2SO4 cause a decrease in the solubilities (salting-out effect) of [Co(acac)3] and L-phalaH, these salts result in an increase in the solubility (salting-in effect) of fac-[Co(amino acidato)3]. The salting-out of [Co(acac)3] is caused by an increase in ΔHs, while the salting-out of L-phalaH results from a decrease in TΔSs. On the other hand, the salting-in of fac-[Co(amino acidato)3] is caused by a decrease in ΔHs. These results suggest that the origin of the salt effect on fac-[Co(amino acidato)3] and L-phalaH differs from that of the salt effect on [Co(acac)3].
  • Georg Schmauch, Teiji Chihara, Yasuo Wakatsuki, Masayuki Hagiwara, Hor ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2573-2579
    Published: 1996
    Released: June 28, 2006
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    The complexes {[M(tim)]2+[Co(mnt)2]2−}, (M = Ni (NiCo), Cu (CuCo), tim = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene, mnt2− = cis-1,2-dicyano-1,2-ethylenedithiolato) have been isolated. NiCo and CuCo have isomorphous crystal structures (P1-), the basic feature of which is the presence of mixed donor–acceptor chains induced by short intrachain distances of 3.15 and 3.03 Å, respectively. For both NiCo and CuCo, an ion pair charge-transfer band is observed at 707 and 843 nm; application of the Hush model affords reorganization energies for electron transfer from the dianion to the dication of 89 and 104 kJ mol−1, respectively. The magnetic properties of the powder samples have been studied in the temperature range of 2 K to 300 K. In NiCo the diamagnetic [Ni(tim)]2+ acceptor induces antiferromagnetic coupling of the spin a half system [Co(mnt)2]2− along the a-axis over a distance of 6.3 Å. From the exchange coupling constant of J = −37 cm−1 a Weiss temperature of 26 K is calculated. Contrary to that, the magnetic orbitals of [Cu(tim)]2+ and [Co(mnt)2]2− remain uncoupled in CuCo.
  • Bijay K. Mishra, Minati Kuanar, Amaresh Mishra, Gopa B. Behera
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2581-2584
    Published: 1996
    Released: June 28, 2006
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    This paper reports the analysis of reversal in solvatochromism of a new class of cyanine dyes by using the ET(30) scale. The point of reversion is defined as a switch that identifies the hydrogen bond donor and hydrogen bond acceptor solvents.
  • Hidehiro Sakurai, Nobuharu Iwasawa, Koichi Narasaka
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2585-2594
    Published: 1996
    Released: June 28, 2006
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    A bis(boronate) compound (1) in which boronate components are situated on the same side of the planar s-indacene framework is synthesized from 1,5-dihydro-1,1,5,5-tetramethyl-s-indacene by OsO4-catalyzed dihydroxylation in the presence of dihydroxyphenylborane. The property of 1 as a host molecule has been examined with various compounds. The host 1 forms a 1 : 1 complex with 4-dimethylaminopyridine (DMAP) when an equimolar amount of DMAP is added; more concave-type complexes (2) are formed than convex-type complexes (3). When excess amounts of DMAP are present, a 1 : DMAP = 1 : 2 complex (4) can be isolated as a single crystal. This complex can be characterized by NMR measurements and X-ray analyses. These analyses indicate that the concave-type complex 2 does not have a bidentate coordination between the two boron–nitrogen atoms as proposed previously, but has a monodentate coordination form.
  • Syun-ichi Kiyooka, Mitsuhiro Tada, Sachie Kan, Mizue Fujio
    1996 Volume 69 Issue 9 Pages 2595-2601
    Published: 1996
    Released: June 28, 2006
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    Bis(binaphtho)-22-crown-5 and bis(binaphtho)-22-crown-4, having bromoarylene moities on their rim, were prepared from (R)- and (S)-2,2′-dihydroxy-1,1′-binaphthyl. An acyclic diol, bridged by two (R)-binaphthyl moieties, underwent cyclization reaction with diethylene glycol ditosylate to afford the corresponding (R,R)-bis(binaphtho)-22-crown-5 in a good yield (69%). A one-pot cyclization reaction of (R)-2,2′-dihydroxy-1,1′-binaphthyl with 2,6-bis(bromomethyl)bromobenzene resulted in a good yield (45%) of (R,R)-bis(binaphtho)-22-crown-4, having two symmetrical bromoarylene units. In contrast to the cases started with (R)- and (S)-2,2′ -dihydroxy-1,1′-binaphthyl, the racemate in cyclization reactions did not give the corresponding crown products in the expected proportion.
  • Hiroshi Nagakubo, Gou Kubota, Kanji Kubo, Tsuyoshi Kaneko, Tadamitsu S ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2603-2611
    Published: 1996
    Released: June 28, 2006
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    The mechanism of intramolecular triplet–triplet (T–T) energy transfer and subsequent reaction in N,O-diacylhydroxylamines was investigated using the model compounds N-(1-naphthoyl)-N-phenyl-O-(benzoyl-substituted benzoyl)hydroxylamines (NPB) with self-sensitization abilities. An examination of the UV absorption and phosphorescence behavior as well as of energy-minimized conformations of these relatively flexible model compounds established that T–T energy transfer from the benzophenone chromophore to the naphthoyl chromophore occurs in a nearly unit efficiency exhibiting only phosphorescence derived from the latter chromophore in both methanol–ethanol (1 : 1 v/v) and 2-chlorobutane at 77 K and is more likely to proceed by a “through-space” mechanism than by a “through-bond” mechanism. The self-sensitized photolysis of NPB with 366 nm light in methanol at room temperature was found to give the fragmentation products, N-phenyl-1-naphthalenecarboxamide (PNA), benzophenone (BP), and benzoyl-substituted benzoic acids (BBA), whereas no BBA was detected in the photolysis in 1,2-dichloroethane and acetonitrile. The finding that the reaction of NPB is efficiently quenched by trans-stilbene according to the Stern–Volmer equation in both methanol and 1,2-dichloroethane indicates that all the products come from the first excited triplet state of the naphthoyl chromophore. On the other hand, the enhanced hydrogen bonding ability of the medium resulted in an increase in the quantum yield for the formation of BBA (ΦBBA) accompanied by a decrease in ΦBA holding the magnitude of ΦBBA + ΦBA nearly constant. But neither ΦPNA nor the quantum yield for the disappearance of NPB was subject to such a hydrogen-bonding effect. This intriguing result was explained in terms of a mechanism in which the N–O bond cleavage in triplet NPB gives a vibrationally excited triplet radical pair whose relaxation is very slow compared to decarboxylation of the caged benzoyl-substituted benzoyloxyl radical in 1,2-dichloroethane. Solvation of this vibrationally hot radical pair through hydrogen bonding substantially promotes its relaxation eventually affording BBA.
  • Masayuki Takeuchi, Masahiro Taguchi, Hideyuki Shinmori, Seiji Shinkai
    1996 Volume 69 Issue 9 Pages 2613-2618
    Published: 1996
    Released: June 28, 2006
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    Chromophric receptors for nucleosides were designed utilizing the boronic acid–diol interaction which effectively operates in aqueous solution. Receptors consist of a boronic acid moiety and a dimethylaminophenylazo moiety. The boronic acid moiety forms a covalently-bonded ester linkage with the 2,3-diol group in nucleosides in a reversible manner and the anionic charge generated on the boron atom is stabilized intramolecularly by the pyridinium cation. The azo moiety can overlap with the heteroaromatic ring moiety in nucleosides to stabilize the complex. The complexation constants could be conveniently determined by the absorption spectral change. Comparison of the complexation constants with those of 2-deoxyadenosine without 2-OH and 1,4-anhydroerythritol without the heteroaromatic ring established that the complex formation is primarily due to the boronic acid–diol (2,3-diol) interaction and secondarily facilitated by the hydrophobic and/or π–π stacking interactions.
  • Masahiro Satoh, Minoru Hirota
    1996 Volume 69 Issue 9 Pages 2619-2624
    Published: 1996
    Released: June 28, 2006
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    A non-isothermal (NIT) method for evaluating the activation enthalpies and entropies of reactions in solutions was applied to several reversible reactions. This was realized by a stepwise elevation of the temperature of a reaction system using a variable-temperature apparatus comprising on NMR spectrometer and a quick collection of FID (free induction decay) at every plateau of the step. The rate from NIT experiments agreed well with the previously measured rates by the conventional methods.
  • Hiroshi Miyauchi, Toshio Nakamura, Naohito Ohashi
    1996 Volume 69 Issue 9 Pages 2625-2632
    Published: 1996
    Released: June 28, 2006
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    SM-9164, a biologically active enantiomer of antifungal agent SM-8668, was prepared by asymmetric synthesis in 10 steps in 13% overall yield from commercially available 2-chloro-1-(2,4-difluorophenyl)ethanone. The crucial steps were Katsuki-Sharpless asymmetric epoxidation of the (E)-allylic alcohol and epimerization of the erythro-sulfone to the desired threo-isomer under basic conditions.
  • Yasushi Kawai, Kentarou Saitou, Kouichi Hida, Duc Hai Dao, Atsuyoshi O ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2633-2638
    Published: 1996
    Released: June 28, 2006
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    Bakers’ yeast reduction of α,β-unsaturated ketones affords optically active saturated ketones contaminated by allylic and saturated alcohols as minor components. Stereoselectivity of the reduction of carbon–carbon double bond strongly depends on the structure of β-aryl substituent. The bakers’ yeast reduction of β-phenyl enones gives saturated ketones in moderate stereoselectivity. Stereoselectivity is not altered by substitution at the para-position, whereas introduction of a substituent at the ortho- or meta-position drastically improves the stereoselectivity. Deuterium-labeling experiments reveal that the enzymatic reduction of carbon–carbon double bond proceeds with formal trans-addition of hydrogens regardless the efficiency of stereoselectivity. The resulting optically active ketone was converted to the precursor of (S)-iopanoic acid, an inhibitor of thyroxine 5′-deiodinase that is a thyroid hormone-converting enzyme and an oral cholecystographic agent.
  • Tadashi Okuyama, Hideki Takano, Koji Senda
    1996 Volume 69 Issue 9 Pages 2639-2644
    Published: 1996
    Released: June 28, 2006
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    The reactions of dibenzo[1,2]oxathiin 6-oxide (1a) and 3,4-dihydro-1,2-benzoxathiin 2-oxide (1b) with a phenolic leaving group were examined in acid and buffer solutions. The substrate 1b undergoes a ring opening in acid and at a higher pH, while 1a is stable in acid with a reverse ring closure predominating. The 18O-labeled 1a undergoes an isotope exchange in acid through a ring opening-closure. Although the ring opening of 1a and 1b is accelerated by buffer bases, owing to nucleophilic catalysis, a similar reaction of 3H-2,1-benzoxathiole 1-oxide with a benzylic alcohol leaving group is independent of the buffer concentration, or is decelerated by some amines. The results are accommodated by a mechanism involving a hypervalent addition intermediate with a varying rate-determining step.
  • Kazuhiro Kobayashi, Masataka Kawakita, Hideki Akamatsu, Osamu Morikawa ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2645-2647
    Published: 1996
    Released: June 28, 2006
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    It has been found that the reactions of sulfoxides bearing hydrogen(s) at the α-position (R1SOCHR2R3: R1 = alkyl or Ph; R2 = H, alkyl, or Ph; R3 = H or Me) with thiols (R4SH: R4 = alkyl or aryl) in the presence of the (diisopropylamino)magnesium reagent, generated in situ from the reaction of ethylmagnesium bromide and diisopropylamine, in diethyl ether gave unsymmetrical dithioacetals (R1SCR2R3SR4) in isolated yields ranging from 44 to 91%.
  • Tsugio Kitamura, Takahiro Fukuoka, Lei Zheng, Takeshi Fujimoto, Hirosh ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2649-2654
    Published: 1996
    Released: June 28, 2006
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    Reaction of alkynyl(p-phenylene)bisiodonium ditriflates with potassium thiocyanate in DMF gave alkynyl thiocyanates and p-iodophenyl(phenyl)iodonium triflate. The latter was readily removed by washing with water. The exclusive sulfur attack of thiocyanate ion suggests that the alkynyl group behaves as a soft acceptor of nucleophiles. The reactions with the enolate anion of 2-phenyl-1,3-indandione in DMF afforded 2-(1-cyclopentenyl)-2-phenyl-1,3-indandiones in the cases of 1-hexynyl- and 1-octynyl-(p-phenylene)bisiodonium ditriflates. In the reactions of 3,3-dimethyl-1-butynyl-, phenylethynyl-, and trimethylsilylethynyl-(p-phenylene)bisiodonium ditriflates, 2-alkynyl-2-phenyl-1,3-indandiones were obtained. The same reactions with the enolate anion of 2-phenyl-1,3-indandione in a mixed solvent of 2-methyl-2-propanol and THF improved the yields of the 1-cyclopentenyl- and alkynyl-substituted indandiones. A large difference in the reaction pathways between the (p-phenylene)bisiodonio and phenyliodonio moieties was observed in the sterically hindered 3,3-dimethyl-1-butynyl systems.
  • Makoto Shimizu, Kouki Sugiyama, Tamotsu Fujisawa
    1996 Volume 69 Issue 9 Pages 2655-2659
    Published: 1996
    Released: June 28, 2006
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    1,1,1-Trifluoro-3-(phenylthio)propan-2-ol was prepared in high enantiomeric purity by lipase-mediated kinetic resolution of the corresponding esters. The resolved alcohol was successfully converted into 1,1,1-trifluoro-2,3-epoxypropane and/or used in the subsequent reactions as latent 1,1,1-trifluoro-2,3-epoxypropane via sulfonium salt formation.
  • Iwao Mogi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 9 Pages 2661-2666
    Published: 1996
    Released: June 28, 2006
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    The electrochemical dopant-exchange (DE) process of p-toluenesulfonate-doped polypyrrole (PPy/TsO) was studied in LiClO4 and LiBF4 aqueous solutions under high magnetic fields of up to 12 T. The application of magnetic fields to the redox process of the PPy/TsO film or to the electropolymerization process shifts the undoping potential of the TsO ion to a positive or negative side, respectively. As a result, the magnetic fields allow control of the plastic behavior in the DE process of the PPy/TsO film. These results are discussed in connection with the effect of the diamagnetic orientation.
  • Kohji Yoshinaga, Makoto Teramoto
    1996 Volume 69 Issue 9 Pages 2667-2672
    Published: 1996
    Released: June 28, 2006
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    A polymer modification of monodisperse colloidal silica (120 nm in diameter) and control of the surface polarity were studied. The binding of poly(maleic anhydride–styrene) to the silica particles and successive grafting of amino-terminated polymethacrylates with methyl, hexyl, and dodecyl ester groups afforded unimodal composite particles, which were dispersible in a low-polar solvent of ethyl acetate. The bindings of the secondary polymer were dependent on the molecular structure of the polymer as well as the reaction conditions. The surface polarity was estimated by aggregation of the particles in an ethyl acetate–methanol cosolvent, monitored by the absorbance of a suspension containing the composite particles at 500 nm. The polarity was significantly affected by the main chain length of the secondary polymer of the polymethacrylates rather than the bound polymer chain number or the branch alkyl ester group of the polymer. For highly modified composite particles, it was observed that the carboxyl group, simultaneously formed in the binding of the secondary polymer, contributed to the surface polarity.
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