Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
74 巻 , 12 号
選択された号の論文の36件中1~36を表示しています
  • Michio Sorai
    原稿種別: Accounts
    2001 年 74 巻 12 号 p. 2223-2253
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    New types of phase transitions occurring in molecule-based materials have recently drawn great attention, in which electrons are directly involved. In this paper are given calorimetric investigations aimed at the elucidation of the mechanisms governing such phase transitions as (i) spin crossover phenomena occurring between high- and low-spin states in transition-metal complexes, (ii) intramolecular electron transfers in mixed-valence complexes, (iii) neutral-to-ionic transitions due to charge transfer mechanism, and (iv) thermochromic phenomena due to a change in coordination geometry. Since a change in the electronic state is strongly coupled with a change in the lattice, it turns out that the transition mechanisms always include interplays with various molecular motions in the lattice. In all these systems, a large change in the electronic energy is compensated by the entropy term due to these molecular motions.
  • Hiroshi Nakazawa, Kazuyuki Kubo, Katsuhiko Miyoshi
    原稿種別: Accounts
    2001 年 74 巻 12 号 p. 2255-2267
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Transition-metal phosphorane complexes, [Cp(CO)2M{P(OC6H4Y)2}] (M = Fe, Ru; Y = NH, NMe, O) have been prepared from [Cp(CO)2M{P(OPh)3}]PF6, o-HOC6H4YH, and a Lewis base. With the use of Et4NF in place of o-HOC6H4YH, [Cp(CO)2Fe(PF4)] and [Cp(CO)2Fe{P(OPh)F3}] have been prepared. These reactions involve nucleophilic attacks of an organic or an inorganic nucleophile at a trivalent phosphorus coordinated to a transition metal and substitution on the phosphorus. The reaction of phosphorane HP(OC6H4NH)2 with a Lewis base leads to NH proton abstraction to give the amide HP(OC6H4NH)(OC6H4N) Subsequent treatment of the anion with EX (MeI, [Cp(CO)2FeCl]) has yielded P-substituted phosphorane EP(OC6H4NH)2 whereas that with E′X (SiMe3Cl, GeMe3Cl, SnMe3Cl, [Cp(CO)CoI2]) has yielded N-substituted phosphorane HP(OC6H4NH)(OC6H4NE′) X-ray structure analyses and spectroscopic data for these metallaphosphoranes reveal that the transition metal fragment serves as a strong π donor toward a phosphorane fragment. The activation parameters for Berry pseudorotation around the phosphorus in several metallaphosphoranes have been determined. The reactivity of metallaphosphoranes was also examined. The iron and ruthenium phosphoranes react with a Lewis base to give Li[{η5-C5H4P(OC6H4Y)2}(CO)2M] In this reaction, one of the protons on the Cp ring is abstracted by the Lewis base and then migration of the phosphorane fragment to the Cp ring takes place. This constitutes the first reported migration of a hypervalent element fragment.
  • Kazuyoshi Ueda, Koji Iwama, Haruo Nakayama
    原稿種別: Headline
    2001 年 74 巻 12 号 p. 2269-2277
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Molecular mechanics and molecular dynamics simulations were performed on two types of disaccharides, neocarrabiose 2,4′-bis(sulfate) and carrabiose 4′,2-bis(sulfate), which are building blocks of ι-carrageenan. Although the conformation and potential-energy surfaces of these disaccharides have been investigated by several researchers, all of them were analyzed using a vacuum calculation. To investigate the conformational behavior of these molecules in water, we performed a molecular dynamics simulation with the presence of explicit water molecules and counter ions around the disaccharides. The trajectories of the glycosidic dihedral angles in the water simulation reproduced the potential-energy surface calculated not with a dielectric constant of 80, but with 1. The electrostatic force was found to act so as to restrict the allowed area of the potential-energy surfaces. The most stable conformation of neocarrabiose 2,4′-bis(sulfate) is φ = 162, ψ = 174. Although the global minimum conformation of carrabiose 4′,2-bis(sulfate) is at A1 (φ = 176° and ψ = −166°), the molecular dynamics simulation in water suggested that the structure, B1 (φ = 164° and ψ = −87°), is more stable than A1 by analyzing the trajectory and the hydrogen bonds with water molecules. This indicates that it is important for the conformational analysis to take into account the solvation effect explicitly. The structure of B1 agrees with that found by an NMR experiment.
  • Tohru Nakajima, Koichi Yamashita
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2279-2283
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A surface reaction mechanism in the aluminum chemical vapor deposition (Al-CVD) method using dimethylaluminum hydride (DMAH) as the material gas has been studied using quantum chemical methods. Density functional theory (DFT) and a cluster model were used to calculate the potential energies and the structures of adsorbates and transition states of surface reactions. We have obtained the result that the hydrogen molecule and trimethylaluminum (TMA) are easily produced, while methane cannot be formed as a reaction product of Al-CVD because of the large barrier height, although the latter reaction path is thermodynamically accessible.
  • Tadayoshi Sakata, Hideo Nakamura
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2285-2293
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A new theory and interpretation of the transfer coefficient based on electrostatic screening of the electrode potential is proposed. A new theory constructed based on the Debye–Hückel theory could quantitatively explain the dependence of transfer coefficient on the ionic strength of the electrolyte solution. The experimental results of the transfer coefficient for hydrogen evolution and Fe3+ / Fe2+ redox reactions were analyzed by this theory. It demonstrates that the transfer coefficient represents the electrostatic screening of the electrode potential by ions in the electrolyte solution near to the electrode. It is also shown theoretically that the information on the “electron transfer distance” is contained in the transfer coefficient.
  • Ryoka Matsushima, Hideki Okuda, Madoka Aida, Atsushi Ogiue
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2295-2301
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Upon changes in temperature or solvent, extensive and reversible color changes (e.g., blue to pink) were observed with a cationic flavylium dye in sugar-gel matrices, such as agar, agarose, pectin, sodium alginate, and carrageenan gels, whereas only small spectral changes were found in methylcellulose gel or in the absence of any sugar gels. During many repeated cycles of warming and cooling no indications of significant fatigue were observed, demonstrating a high thermochromic reversibility. Comparable thermochromism and solvatochromism were observed with the well-known cationic dye Methylene Blue in the sugar-gel matrices. In the presence of an anionic surfactant in place of sugar gel, extensive color changes were also observed while no changes were observed at all in the presence of a cationic surfactant, thus implying an important role of the electrostatic interactions between the cationic dye and anionic surfaces or species. It has been assumed that the cationic dyes are reversibly coagulated or condensed on the negatively charged colloid-gel surface to enhance dye aggregation.
  • Tadaaki Ikoma, Qiwu Zhang, Fumio Saito, Kimio Akiyama, Shozo Tero-Kubo ...
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2303-2309
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    For the first time, we detected paramagnetic products generated during the grinding of 3-chlorobiphenyl (BP-Cl) with calcium oxide (CaO) nanoparticles by a ball mill method, which is one of the promising ways to detoxify hazardous chlorinated organic compounds. Those products were assigned to oxygen-centered aromatic radicals coming from BP-Cl and trapped electrons in oxygen vacancies on the surfaces of the CaO reactants using high-frequency and pulsed electron paramagnetic resonance spectroscopies. The observed good correlation between the dechlorination efficiency and the radical yield suggests that a radical mechanism plays an important role in the destruction of organochlorine compounds. The mechanochemical dechlorination could be interpreted by the following mechanism. First of all, the mechanical stressing induces the electron transfer from O2− sites on the surface of the CaO particle to the organic compounds. The produced organic anion radicals then undergo the effective self-dissociation of a chlorine–carbon bond.
  • Lei Liu, Chao Yang, Qing-Xiang Guo
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2311-2314
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    In this study, it was found that in the molecular recognition of cyclodextrins, the guest compounds fall clearly into different classes according to the behavior of enthalpy–entropy compensation. Good enthalpy–entropy compensation takes place when the substrates are hydrophobic, whereas poor or no enthalpy–entropy compensation occurs when the substrates are relatively hydrophilic. A thermodynamic theory is proposed to explain the behaviors, and it is suggested that solvent molecular reorganization constitutes the physical origin of the enthalpy–entropy compensation in cyclodextrin complexation.
  • Jun-ichi Aihara
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2315-2318
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Lipscomb et al. designed the low-energy deltahedral isomers of borane dianions BnHn2− for n ranging from 13 to 24. We evaluated the topological resonance energies (TREs) of these dianions by applying the Kettle–Tomlinson (KT) bonding model to them. It was then found that except for B18H182− (D6d) the TRE per BH unit is highly correlative with the PRDDO binding energy per BH unit. This indicates that the thermodynamic stability of deltahedral borane dianions is determined primarily by aromaticity. B18H182− (D6d) has a very small TRE per BH unit, strongly reflecting its small HOMO–LUMO energy separation. Thus, the KT model is useful for describing electronic characteristics of large deltahedral borane dianions.
  • Kenji Komaguchi, Hiroshi Sakurai, Masaru Shiotani, Akinori Hasegawa
    原稿種別: Article
    専門分野: TP
    2001 年 74 巻 12 号 p. 2319-2324
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    The ESR spectra for the cation radicals of CH3CH2F (FE) and its partially deuterated derivatives, formed by irradiation with γ-rays in SF6 matrices at 77 K, were observed at low temperatures. The spectra consist of two lines typical of an anisotropic hyperfine coupling to a 19F nucleus. The optimized geometry of FE•+ was obtained by the ab initio MO method, and hyperfine splittings were evaluated by density functional theory (DFT). Two structures, A and B, were obtained having 2A′ and 2A′′ electronic states, respectively. Structure A is in a lower energy state by 0.31 eV than structure B, and is assigned to the detected cation radical. This structure has a SOMO composed of the 2p orbitals of two C and an F atoms in the molecular plane, and has an elongated C–C bond of 0.1884 nm. This resembles the SOMO given for C2H6•+. Furthermore, the structural distortion of FE•+ in zeolite and the thermal dissociation of FE•+ in matrices are reported.
  • Yoshifumi Tanimoto, Yukimi Akimoto, Yoshihisa Fujiwara, Masahiro Mukai ...
    原稿種別: Short Articles
    専門分野: TP
    2001 年 74 巻 12 号 p. 2325-2326
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    The magnetic field effect (≤ 0.59 T) on the quintet–quintet fluorescence of m-phenylenebis(phenylmethylene) (MPBP) was studied in a rigid glass, decaline–cyclohexane (3 : 1) mixture, at 77K. The fluorescence decay rate of MPBP increases in a magnetic field. The effect on the MPBP fluorescence is explained in terms of the Zeeman mixing of excited quintet sublevels of MPBP.
  • Tomoharu Ama, Md. Monzur Rashid, Ashok Kumar Sarker, Hideyuki Miyakawa ...
    原稿種別: Article
    専門分野: AI
    2001 年 74 巻 12 号 p. 2327-2333
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A trinuclear cobalt(III) complex, [Co3(L-his)3(μ-OH)3(μ3-O)]ClO4·H2O (L-Hhis: L-histidine), containing an incomplete cubane Co3O4 core was isolated and the structure was compared with [Co3(edma)3(μ-OH)3(μ3-O)]+ (Hedma: NH2CH2CH2NHCH2COOH) isomers. Using the edma and L-his as N–N–O type ligands, [Mo3(L)3(μ-S)3(μ3-S)]+ complexes with a Mo3S4 incomplete cubane core were also prepared, and their structures were determined by the X-ray diffraction method. A structural similarity between [Mo3(L)3(μ-S)3(μ3-S)]+ and [Co3(L)3(μ-OH)3(μ3-O)]+ is discussed; it is suggested that three N–H···O inter-ligand (intra-molecular) attractive interaction has an important role in stabilizing the incomplete cubane structure.
  • Hidetaka Konno, Yoshitaka Aoki, Zoltán Klencsár, Attila ...
    原稿種別: Article
    専門分野: AI
    2001 年 74 巻 12 号 p. 2335-2341
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Single phase zircon type EuCrO4 (S.G. I41/amd) was synthesized and the structure including atomic positions was precisely determined by X-ray Rietveld refinement. The electronic and magnetic properties of the compound were studied based on the electric conductivity, Seebeck coefficient, Raman spectroscopy, Mössbauer spectroscopy, magnetic susceptibility, and specific heat. The CrO43− tetrahedra in EuCrO4 were slightly elongated compared with that in NdCrO4, which caused splitting of the degenerated vibration modes of CrO43−, ν2 and ν3, in the Raman spectra. The 151Eu Mössbauer spectra showed not a trace of the Eu(II) species in the compounds measured in the present work. The Debye temperature, ΘD, estimated from Mössbauer spectra suggested that the vibrational state of Eu(III) in EuCrO4 was similar to that in the perovskite-type EuCrO3. However, the isomer shift of Mössbauer spectra revealed that the electron density of the 6s orbital of Eu(III) in EuCrO4 was very low and almost the same as that in the zircon type EuVO4, that is, Eu(III) in these compounds has highly ionic character, whereas the electron density of the 6s orbital of Eu(III) in EuCrO3 was higher and nearly the same as that in Eu2O3. EuCrO4 was found to be an n-type semiconductor similar to NdCrO4, while zircon type REMO4 (RE: rare earth metal(III); M: V, P, As, etc.) are insulators. Magnetic susceptibility and specific heat measurements showed that antiferromagnetic transitions took place at around 15 K and was solely due to Cr(V) from the magnetic entropy value of 5.54 J mol−1 K−1.
  • Seiichi Nishizawa, Tomoyuki Yokobori, Ryo Kato, Takeshi Shioya, Norio ...
    原稿種別: Article
    専門分野: AI
    2001 年 74 巻 12 号 p. 2343-2347
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Applicability of a thiourea-based hydrogen-bonding ionophore 2, N,N′-bis(p-nitrophenyl)thiourea, for amperometric anion sensors is presented. Chloride transfer across the nitrobenzene (NB)–water interface facilitated by this ionophore is studied by using ion transfer polarography. When 2 is present in the organic phase, a well-defined wave can be observed, indicating that the chloride transfer across the NB–water interface is facilitated by 2 via formation of hydrogen bonds. The analysis of ion transfer polarograms shows that the chloride transfer is assisted by 1 : 1 complexation between 2 and chloride, and that the transfer process is reversible and controlled by diffusion of 2 from the bulk NB phase to the interface. Despite its simple binding mode based on two point interactions, mono-thiourea 2 has a strong ability to facilitate chloride transfer, which is comparable to that obtained for a highly preorganized bis-thiourea ionophore 1, 2,7-di-t-butyl-4,5-bis(N′-butylthioureylene)-9,9-dimethylxanthene, in which four hydrogen bonds are involved in the chloride binding.
  • Takayoshi Suzuki, Shinsaku Kashiwamura, Kazuo Kashiwabara
    原稿種別: Article
    専門分野: AI
    2001 年 74 巻 12 号 p. 2349-2359
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A series of new cobalt(III) phosphine complexes of trans-[Co(dtc)2(PMe3−nPhn)2]BF4 (dtc = N,N-dimethyldithiocarbamate; n = 0, 1, 2 or 3) and cis-[Co(dtc)2(PMe3 or PMe2Ph)2](BF4 or PF6) have been prepared and their crystal structures and spectroscopic properties have been investigated. It is found that the Co–S bond lengths vary with steric and electronic factors of the P-ligands; i.e. (1) the intramolecular π–π stacking interaction between the dtc plane and the phenyl ring of the P-ligand, and (2) the electronic trans influence of the trans-positioned P-ligand. The strength of electronic trans influence decreases as PMe3 > PMe2Ph > P(OCH2)3CEt in accordance with the order of σ-donicity strengths. In the series of trans-isomers, the electronic trans influence is competitive with the steric requirement of the phosphine to elongate the mutually trans Co–P bonds. The steric trans influence via the equatorial dtc ligands for such an elongation of the Co–P bonds seems to be negligible, which is in sharp contrast to the situation for via pentane-2,4-dionate (acac) ligands in the analogous complexes, trans-[Co(acac)2(PMe3−nPhn)2]PF6. This is probably due to the compactness of dtc and the resulting open space at the Co atom. The fact that the Co–P bond lengths in the dtc complexes are shorter than those in the acac complexes is reflected in the larger stability toward hydrolysis of the dtc complexes. In the UV-vis absorption spectra, the degenerate splitting component (a1Eg) of the first d–d transition band of trans-[Co(dtc)2(PMe3−nPhn)2]+ is observed at almost the same position (within 300 cm−1) as that of the corresponding acac complexes, while the transition energies of the P-to-Co LMCT of these two series of complexes are rather different (at least 2700 cm−1) from each other. Furthermore, the first and the second d–d transition bands of cis-[Co(dtc)2(PMe3 or PMe2Ph)2]+ are observed at lower energy than those of cis-[Co(dtc)2{P(OMe)3}2]+ in spite of a weaker σ-donor of phosphite. The separation of the first and the second d–d transition bands of the P(OMe)3 complex is remarkably smaller than the separation of the bands of the PMe3 one, being indicative of a further reduction of the interelectronic repulsion in the P(OMe)3 complex.
  • Shinya Hayami, Yuko Hosokoshi, Katsuya Inoue, Yasuaki Einaga, Osamu Sa ...
    原稿種別: Article
    専門分野: AI
    2001 年 74 巻 12 号 p. 2361-2368
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Binuclear iron(III) spin-crossover complexes with salten ligand [Fe2(salten)2(L)](BPh4)2 were synthesized and characterized by single-crystal X-ray diffraction, Mössbauer spectra, magnetic susceptibilities and electronic spectra, where H2salten is a pentadentate ligand derived from salicylaldehyde and 3,3′-diaminodipropylamine and L is a didentate axial ligand (az = azobis(4-pyridine) and cc = 4,4′-vinylenebis(pyridine)). The structures of [Fe2(salten)2(az)](BPh4)2 (1) and [Fe2(salten)2(cc)](BPh4)2 (2) were determined at both 100 K and 298 K. Crystal data for 1 at 100 K: C98H94O4N10B2Fe2, monoclinic, space group P21/c, Z = 2, a = 15.986(2) Å, b = 15.825(2) Å, c = 16.441(2) Å, β = 107.902(2)°, V = 3957.8(8) Å3. Crystal data for 2 at 100 K: C100H96O4N8B2Fe2, monoclinic, space group P21/a, Z = 2, a = 16.4296(8) Å, b = 15.747(1) Å, c = 16.637(1) Å, β = 109.2375(9)° and Z = 2. The complexes 1 and 2 exhibited the spin-crossover behavior depending on temperature within the temperature range of 200 to 350 K, and rapid spin equilibrium behavior was observed by means of Mössbauer spectroscopy at 293 K. The complexes 1 and 2 also exhibited a pressure-induced spin transition between the rapid spin equilibrium state and low-spin state at 300 K. Such a pressure-induced spin transition has not been reported earlier.
  • Keisuke Hirano, Hitoshi Yamato, Kazuhiko Kunimoto, Masaki Ohwa
    原稿種別: Article
    専門分野: AI
    2001 年 74 巻 12 号 p. 2369-2372
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    It was found that N,N-dimethylindoaniline works as an excellent electron-transfer mediator for lactate oxidase. The second-order rate constant (kmed) with lactate oxidase in solution was much higher than that of other typical mediators, such as ferrocene and potassium hexacyanoferrate(II). An enzyme electrode using this compound as a mediator showed a larger response current and a higher sensitivity to lactate than a Pt-based H2O2 detecting lactate sensor. This sensor demonstrated a clear independence on the oxygen concentration in a buffer and a quite low interference current by ascorbic acid, etc. A H2O2 detecting sensor was strongly interfered by acetaminophen and uric acid, while a mediator based sensor was slightly influenced by uric acid. This sensor also showed good durability, which retained more than 90% of the initial activity until day 11.
  • Ashraf Abdel-Aaty Mohamed
    原稿種別: Short Articles
    専門分野: AI
    2001 年 74 巻 12 号 p. 2373-2374
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A new, simple, and sensitive method has been developed for the spectrophotometric determination of CrVI based on its reaction with chlorpromazine-HCl (CPH) to give a red product. Under the optimum conditions, the linear range of the calibration graph was 0.00–0.33 µg mL−1 of CrVI. The molar absorptivity and the detection limit were 3.28 × 104 dm3 mol−1 cm−1 and 0.003 µg mL−1 of CrVI, respectively. Analyses of certified ores, steels, and pure nickel samples gave results in excellent agreement with the nominal values and with relative standard deviations of ≤ 1.5%
  • Sachiyo Sakamoto, Akihiro Yatani, Katsusi Kimura, Mie Fujii, Yasuo Nak ...
    原稿種別: Short Articles
    専門分野: AI
    2001 年 74 巻 12 号 p. 2375-2376
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    The cation of [Cu(L1)(OMe)(ClO4)Cu(bpy)] ClO4 (1) consists of two coppers triply bridged by an oximato, a methoxo, and a perchlorato ligand, where L1 is 3-[2-(2-pyridyl)ethyl]amino-2-butanone oxime. The geometry around each copper is distorted square-pyramidal. The cation of [Cu(L1)(OAc)2Cu(bpy)]ClO4 (2), consists of two coppers triply bridged by an oximato, an unidentate and a bidentate acetato ligand. The geometry around the coppers is intermediate between a square pyramid and a trigonal bipyramid.
  • Kan Kanamori, Kyoko Ishida, Kazuya Fujimoto, Tomohiko Kuwai, Ken-ichi ...
    原稿種別: Short Articles
    専門分野: AI
    2001 年 74 巻 12 号 p. 2377-2378
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A vanadium(III) complex with N-hydroxyethyliminodiacetate (heida(3-)) was prepared. The X-ray crystallography has revealed that the compound is a dinuclear vanadium(III) complex, which contains a di-μ-alkoxo bridge derived from the deprotonation of the hydroxyethyl group of the parent heida(2-) ligand. Each vanadium(III) center adopts a distorted octahedral structure. The temperature-dependent magnetic susceptibility measurement suggests that the electronic spin moments of the two vanadium(III) centers are antiferromagnetically coupled (g = 1.98 and J = −36.9 cm−1).
  • Andreas Schmidt, Markus Karl Kindermann
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2379-2384
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Intermolecular interactions of modified nucleobases with altered charge properties in relation to natural systems are studied. We prepared conjugated mesomeric betaines of purines and examined their properties by semiempirical calculations, 1H NMR titrations and ESI mass spectrometry. Thus, nucleophilic substitutions of 4-(dimethylamino)pyridine and pyridine, respectively, on 2-amino-6-chloropurine 1 and 2,6-dichloropurine 2 resulted in the formation of purin-6-yl hetarenium salts 36. These were converted into the conjugated mesomeric betaines 710, respectively, on treatment with the anion exchange resin Amberlite® IRA-400 in its hydroxy form. The betaines 710 possess umpoled purine rings in relation to 7-methylguanine that forms the betainic 5′-cap structure of m-RNA. We studied the π-stacking interactions of the conjugated mesomeric betaine 8 and of its cationic precursor 4 with L-tryptophan, adenine, adenosine, and guanosine in deuterated water.
  • Nobuaki Nonoyama, Hiroshi Oshima, Chizuru Shoda, Hitomi Suzuki
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2385-2395
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    The reactions of peroxynitrite with a variety of organic molecules which include a biologically important functionality have been examined to construct a simple model for the peroxynitrite-induced in vivo transformations as well as a chemical probe for the active species involved therein. Phenols were found to undergo hydroxylation, nitration, oxidative dimerization, and oxidation to cyclohexadienones and quinones. The ring nitration of catechol was confirmed for the first time in the in vitro reaction of peroxynitrite. Dealkylation and N-oxide formation were the major reaction modes observed for N,N-dimethyl-p-toluidine. 1,2-Phenylenediamine gave benzotriazole in high yield. The electron-deficient C–C double bond in 1,4-naphthoquinone underwent epoxidation, while the electron-rich C–C double bond in α-methylstyrene suffered oxidative cleavage to acetophenone. The activated double bond in trans-stilbene underwent oxidative cleavage and epoxidation in parallel to give benzaldehyde and trans-stilbene oxide as the major products. The triple bond in diphenylacetylene was simply oxygenated to form benzil, together with trace amounts of ring nitration products. 1-Phenylethanol, imidazole, 2′-deoxyadenosine, and 2′-deoxyguanosine were all quite slow to react, while uracil and cytosine were almost inert to peroxynitrite. The reaction modes exhibited by peroxynitrite are too widespread and complicated to explain the whole mechanistic pathway in terms of a single active species. All reaction modes observed for the peroxynitrite to date could be classified into five categories according to their types: i) electron transfer type, ii) O-electrophilic type, iii) N-electrophilic type, iv) O-nucleophilic type, and v) radical type. Some of these may compete under certain conditions. The active species involved in each of these types of reactions are as follows: i) NO+, NO2, and OH, ii) ONOOH, iii) ONOOH and NO+, iv) OOH and ONOO, and v) NO2 and OH.
  • Thota Ganesh, Kamalesh Kedarnath Sharma, Gazula Levi David Krupadanam
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2397-2399
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A novel regioselective synthesis of neolignan, 6-(3-hydroxy-1-propenyl)-2-phenyl-2,3-dihydrobenzo[b]-1,4-dioxin-3-methanol, is described. 2-[bromo(phenyl)methyl]-oxirane upon condensation with 3,4-dihydroxybenzaldehyde gave regioselectively (±)-trans-3-hydroxymethyl-2-phenyl-2,3-dihydrobenzo[b]-1,4-dioxin-6-carbaldehyde, which upon reaction with dihydropyran in dichloromethane using (PPTS) gave 2-phenyl-3-(tetrahydro-2-pyranyloxy-methyl)-2,3-dihydrobenzo[b]-1,4-dioxin-6-carbaldehyde. This compound by a Wittig reaction with ethoxycarbonylmethylenetriphenylphosphorane gave stereoselectively ethyl 3-[trans-2-phenyl-3-(tetrahydro-2-pyranyloxymethyl)-2,3-dihydrobenzo[b]-1,4-dioxin-6-yl]-2-propenoate, which upon reduction with DIBAL-H afforded the title compound.
  • Habib Firouzabadi, Shahram Eslami, Babak Karimi
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2401-2406
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    An efficient and chemoselective preparation of cyclic and acyclic thioacetals from carbonyl compounds, cyclic and acyclic acetals and acylals in the presence of catalytic amounts of neutral lithium triflate and thiols under solvent-free conditions is described.
  • Masafumi Unno, Takashi Saito, Hideyuki Matsumoto
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2407-2413
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Five new silapericyclynes, (i-Pr2SiC≡C)n (n = 6, 8, 10) and (i-Pr2SiC≡CMe2SiC≡C)n (n = 3, 4) were prepared, and their structures were determined by X-ray crystallography. For sila[6]pericyclynes, the ring structures depend upon the steric demand of the substituents on silicon atoms; (i-Pr2SiC≡C)6 crystallized in nearly planar structure, and (i-Pr2SiC≡CMe2SiC≡C)3 formed a chair structure with small dihedral angles (109.6° and 121.7°), while (Ph2SiC≡C)6 crystallized in boat and chair forms. The crystal structures of larger pericyclynes (i-Pr2SiC≡C)8, (i-Pr2SiC≡C)10, and (i-Pr2SiC≡CMe2SiC≡C)4 showed that the substituents, isopropyl groups, were included inside the rings. These compounds show absorption maxima in the range of 203–221 nm.
  • Kabir M. Hossain, Toru Kameyama, Takanori Shibata, Kentaro Takagi
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2415-2420
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    In the presence of a catalytic amount of Pd2+ or Pd0, oxidative homo-coupling of arylzinc compounds was achieved by the use of N-chlorosuccinimide (NCS) or O2 as an oxidant. Different reaction pathways were involved in the catalytic reactions depending on the oxidants; NCS or O2 probably oxidized I or Pd0 to I+ or Pd2+, respectively. This reaction disclosed a new and facile synthetic method of biaryls from aryl halides or arenes via arylzinc intermediates.
  • Osamu Takahashi, Yuji Kohno, Sachiyo Iwasaki, Ko Saito, Michio Iwaoka, ...
    原稿種別: Article
    専門分野: OB
    2001 年 74 巻 12 号 p. 2421-2430
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Spatial distribution of CH hydrogen atoms with reference to a six-membered carbon aromatic ring was analyzed in the crystal structures deposited in the Cambridge Structural Database (CSD). The crystal data showed the propensity that the CH hydrogen atoms lie above the center of the aromatic ring to form interatomic CH/π contacts. Investigation of the effects of the CH proton acidity on the strength and the structure of the CH/π interaction has demonstrated that the distance between the hydrogen atom and the π plane (Dpln) decreases with increase of the CH proton acidity (Dpln: CCH3sp2-CH > sp-CH ≅ Cl2CH2 > Cl3CH), and that the C–H···π access angle (α) tends to approach 180° in the same order. Further, a negative correlation has been found between Dpln and α. The directional preferences are in accord with the property of conventional hydrogen bond, indicating a hydrogen-bond-like character of the CH/π interaction. In order to elucidate the intrinsic nature of the CH/π interaction, ab initio calculations [MP2/6-311++G(d,p)] were carried out for methane/benzene, ethylene/benzene, and acetylene/benzene complexes. Potential surfaces obtained for the three model supramolecules are consistent with the results from the CSD analyses.
  • Yoshimi Sueishi, Arimitsu Hori
    原稿種別: Short Articles
    専門分野: OB
    2001 年 74 巻 12 号 p. 2431-2432
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    The spin exchange of nitroxide with copper(II) and iron(III) complexes was studied by means of a high-pressure EPR technique. The spin exchange with CuII complexes exhibited the aspect of weak exchange, independent of the kinds of coordinated ligands, while the spin exchange with FeIII complexes was found to vary from weak exchange to a strong one, dependent of the solvent viscosity. Based on the results, the spin exchange with CuII and FeIII complexes is discussed in detail.
  • Piotr Lulinski, Nicolas Obeid, Lech Skulski
    原稿種別: Short Articles
    専門分野: OB
    2001 年 74 巻 12 号 p. 2433-2434
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Arenes (ArH) were substituted with some transient I3+ species, generated in situ in appropriate, anhydrous I2/NaIO4 or NaIO3/AcOH/Ac2O/concd H2SO4 mixtures, to form soluble organoiodine(III) intermediates, ArISO4. Next, excess concd hydrochloric acid was added to precipitate out the title ArICl2, and isolated in 46–88% optimized crude yields.
  • Takuya Nishioka, Takashi Arimura, Yasuhiro Suga, Shigeo Murata, M. Tac ...
    原稿種別: Short Articles
    専門分野: OB
    2001 年 74 巻 12 号 p. 2435-2436
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    The preparation of a calix[4]arene-based dual boron–dipyrrin system was accomplished by the condensation of diformylcalix[4]arene and pyrrole followed by a treatment with DDQ and diethyl ether–boron trifluoride (1/1). An X-ray crystal structure analysis and spectroscopic measurements revealed that the cone conformation of calix[4]arene serves to define 14.9 Å as the center-to-center boron–dipyrrin separation.
  • Jianwei Wu, Hiroaki Okamoto, Yuki Morita, Shunsuke Takenaka
    原稿種別: Article
    専門分野: AM
    2001 年 74 巻 12 号 p. 2437-2443
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    This paper describes the liquid–crystal properties of 4-(4-alkoxyphenoxycarbonyl)phenyl 3-alkoxy- (1), 3-alkoxy-4-methyl- (2), and 3-alkoxy-2-methyl-benzoates (3). Most of the homologs of 1 are non-mesogenic, due to the long alkoxy group at the 3 position restraining the appearance of liquid–crystal properties. The substitution of a methyl group at the 2 or 4 position effectively facilitates the appearance of a nematic phase. The average effective order for the nematic-isotropic transition temperatures is 3 > 2 > 1. The liquid–crystal properties of these compounds are discussed in terms of the change in the conformation of the alkoxy group at the 3 position.
  • Yutaka Amao, Yuichi Ishikawa, Ichiro Okura, Tokuji Miyashita
    原稿種別: Article
    専門分野: AM
    2001 年 74 巻 12 号 p. 2445-2449
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    A new optical oxygen sensor based on the luminescence intensity change of a terbium(III) complex, tris(acethylacetonato)(1,10-phenanthroline)terbium(III) complex, ([Tb(acac)3(phen)]), adsorbed thin film onto an alumina plate, was developed. The luminescence peak positions of [Tb(acac)3(phen)] film were observed at 490, 546, 590 and 620 nm. The luminescence intensities of [Tb(acac)3(phen)] in the film decreased with increasing the oxygen concentration, indicating that the film can be used as an optical oxygen sensing device based on luminescence quenching by oxygen. The ratio I0/I100 (I0 and I100 represent the detected luminescence intensities from the film exposed to 100% argon and 100% oxygen, respectively) values of [Tb(acac)3(phen)] film are estimated to be 2.66 (490 nm), 2.68 (546 nm), 2.67 (590 nm) and 2.66 (620 nm), respectively. [Tb(acac)3(phen)] film obeyed a Stern–Volmer plot with a multi-site model and possessed good operational stability. The response times of the [Tb(acac)3(phen)] film were 7.3 s for switching from argon to oxygen, and 70 s for switching from oxygen to argon.
  • Gary Admans, Yoshimasa Takahashi, Satoshi Ban, Hiroaki Kato, Hidetsugu ...
    原稿種別: Article
    専門分野: AM
    2001 年 74 巻 12 号 p. 2451-2461
    発行日: 2001年
    公開日: 2002/12/01
    ジャーナル 認証あり
    Structure–activity relationships for aquatic toxicity were studied using neural networks and linear regression analysis. The structural features contributing to toxicity were identified in molecules exhibiting a level of toxicity greater than that of non-reactive organic molecules. A neural network was trained for the toxicity of non-polar narcotics, polar narcotics, or reactive toxicants. Quantitative structure–activity relationships (QSARs) were developed, relating a molecular aquatic toxicity to its log P and to a set of 16 structural descriptors based upon the presence of selected structural features. The inclusion of these structural descriptors into a QSAR was found to enhance the correlation of the equation, and thus to improve its ability for predicting aquatic toxicity.
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