bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Dimensional Structures Constructed by the Electrostatic Interaction of Potassium Salts of Cobalt(III) and Manganese(III) Complexes with 1,2-Bis(2-hydroxybenzamido)benzene
Authors: Sunatsuki Yukinari , Mimura Masaaki , Shimada Hiromitsu , Kai Fumiaki , Matsumoto Naohide
Published: August 2005

Potassium salts of cobalt(III) and manganese(III) complexes, K[CoL(py)2]·2EtOH·MeOH 1 and K[MnL(py)2]·py 2, have been prepared, where H4L = 1,2-bis(hydroxybenzamido)benzene and py = pyridine. 1 crystallizes in the monoclinic space group P21/n with the cell dimensions of a = 12.688(3), b = 17.555(4), c = 16.673(3) Å, β = 102.59(2)°, V = 3624(1) Å3, and Z = 4, in which potassium ion plays a role of connector for two adjacent [CoL(py)2]− molecules through K–O interaction (two phenoxo oxygen atoms of a cobalt(III) complex, two oxygen atoms of the solvent molecules, and an amido oxygen of the adjacent unit) to give an extended one-dimensional structure. 2 crystallizes in the orthorhombic space group P212121 with the cell dimensions of a = 14.358(1), b = 16.457(2), c = 13.703(2) Å, V = 3237.7(5) Å3, and Z = 4, in which potassium ion plays a role of connector for three adjacent [MnL(py)2]− molecules through K–O interaction to give an extended three-dimensional structure.
Reduction of CO2 Directed toward Carbon–Carbon Bond Formation
Authors: Tanaka Koji
Published: August 2005

This paper describes electrochemical reduction of CO2 directed toward carbon–carbon bond formation via metal–CO2 adducts. An electrophilic attack of CO2 to penta-coordinated low valent polypyridyl Ru complexes affords a Ru–η1-CO2 adduct, which is easily converted to Ru–CO species either by an acid-base equilibrium in protic media and oxide transfer to CO2 under aprotic conditions. Two-electron reduction of resultant Ru–CO in protic solutions competitively causes a cleavage of the Ru–CO bond (CO evolution) and formation of a thermally labile Ru–CHO bond. Besides further reduction of the latter to Ru–CH2OH as precursors to CH3OH and HOOCCH2OH, Ru–CHO reacts with CO2 to afford HCOOH with regenerating Ru–CO as the precursor to CO. Thus, the difficulty of multi-electron reduction of CO2 in protic solutions is ascribed to the thermal lability and strong hydride donor character of Ru–CHO. On the other hand, two-electron reduction of Ru–CO in the presence of (CH3)4N+ or CH3I under aprotic conditions produces thermally stable R–C(O)CH3, which works as a precursor to CH3C(O)CH3. Two-electron reduction of M3(μ3-S)2 clusters (M = Co, Rh, Ir) causes an M–M bond cleavage and the nucleophilicity of the μ3-S ligand is also enhanced. As a result, two CO2 molecules reductively activated probably on μ3-S and metal sites undergo the coupling reaction to give oxalate selectively.
Reactivities of Molybdenum and Tungsten Diazoalkane–Isocyanide Complexes Derived from Dinitrogen Complexes
Authors: Harada Yuji , Mizobe Yasushi , Aoshima Takayuki , Oshita Hiroyuki , Hidai Masanobu
Published: August 2005

The diazoalkane–isocyanide complexes cis,trans-[MX2(NN=CMePh)(CNBut)(PMe2Ph)2] (1a: M = Mo, X = Cl; 1b: M = W, X = Cl; 1c: M = W, X = Br), readily derived from dinitrogen complexes cis-[M(N2)2(PMe2Ph)4], reacted with AlMe3 at room temperature to give the aminocarbene–diazoalkane complexes cis,trans-[MX2(NN=CMePh){=C(Me)NHBut}(PMe2Ph)2] (2a: M = Mo, X = Cl; 2b: M = W, X = Cl; 2c: M = W, X = Br) after hydrolysis. Treatment of 1b with TfOH (Tf = CF3SO2) and then with ButNC at room temperature resulted in the formation of a cationic bis(isocyanide)–diazoalkane complex trans,trans-[WCl(NN=CMePh)(CNBut)2(PMe2Ph)2] [OTf] (3). The detailed structures of 2b and 3 have been determined by single-crystal X-ray analyses.
The Olefin Synthesis from β-Hydroxyalkylphosphonates Induced by Fluorides or Relatively Weak Bases
Authors: Kawashima Takayuki , Ishii Takafumi , Inamoto Naoki , Tokitoh Norihiro , Okazaki Renji
Published: August 2005

β-Hydroxyalkylphosphonates, which were prepared readily from alkylphosphonates and carbonyl compounds, were treated with a fluoride ion such as CsF or with relatively weak bases such as K2CO3 in N,N-dimethylformamide to give the corresponding olefins in good yields. One molar equivalent of water to bases is effective for increasing the yields of olefins. The stereochemistry of erythro-dimethyl (2-hydroxy-1-methyl-2-phenyl)ethylphosphonate was determined by X-ray crystallographic analysis. Use of threo-isomer gave (E)-olefin exclusively, while that of erythro-enriched isomer afforded predominantly (Z)-olefin, indicating that the present olefination proceeds stereospecifically in a manner of syn-elimination.
Structures and Tropicity of Hydrogenation Products of a Bisdehydro[13]annulenone and a Bisdehydro[15]annulenone
Authors: Higuchi Hiroyuki , Hiraiwa Naoki , Daimon Tomoyo , Kondo Shiro , Ojima Juro , Iyoda Masahiko , Yamamoto Gaku
Published: August 2005

The catalytic partial hydrogenation of the 5,10-dimethyl-6,8-bisdehydro[13]annulenone using Pd–BaSO4 afforded the 5,10-dimethyl[13]annulenone together with two isomeric 5,10-dimethyl-6-dehydro[13]annulenones. The dimethyl[13]annulenone, which is the first example of a monocyclic non-dehydro annulenone derivative larger than tropone, was found to be atropic on the basis of 1H NMR spectra. Molecular mechanics studies indicate the extensive deviation of the molecular skeleton from planarity and help to explain the lack of peripheral conjugation. Attempts to obtain the [15]annulenone and the [17]annulenone from the bisdehydro[15]annulenone and the bisdehydro[17]annulenone, respectively, were unsuccessful.
Vinylic SN2 Reaction of 1-Decenyliodonium Salt with Halide Ions
Authors: Okuyama Tadashi , Takino Tomoki , Sato Koichi , Oshima Kunio , Imamura Shohei , Yamataka Hiroshi , Asano Tsutomu , Ochiai Masahito
Published: August 2005

Reactions of (E)-1-decenyl(phenyl)iodonium salt with halide ions are examined under various conditions. The products are those of substitution and elimination, usually (Z)-1-halo-1-decene and 1-decyne, as well as iodobenzene, except for the reaction with fluoride which leads exclusively to elimination. The labeling experiments show that the elimination induced by fluoride occurs via an α mode, while that caused by the other halides is a syn  β elimination. Kinetic results show that the substitution and β elimination occur mainly from the halo-λ3-iodane intermediate; the substitution occurs as a bimolecular reaction with the external halide ion while the elimination is a unimolecular (intramolecular) reaction. The intermediacy of the hypervalent λ3-iodane as well as of the iodate are also confirmed by UV spectroscopy. The secondary kinetic isotope effects, leaving group substituent effects, and pressure effects on the rate are compatible with the in-plane vinylic SN2 mechanism for the substitution with inversion. Some retained substitution product, (E)-1-halo-1-decene, is formed in polar protic solvents like trifluoroacetic acid, formic acid, and 1,1,1,3,3,3-hexafluoro-2-propanol. The reaction is very slow in these solvents and no sign of formation of ionic intermediates is found. This slow substitution with retention is considered to occur via ligand coupling within the halo-λ3-iodane intermediate.
Total Synthesis of Acanthacerebroside A and Astrocerebroside A via a Chiral Epoxide Intermediate Derived from l-Quebrachitol
Authors: Chida Noritaka , Sakata Noboru , Murai Katsuyuki , Tobe Takahiko , Nagase Toshihiko , Ogawa Seiichiro
Published: August 2005

The chiral and stereoselective total synthesis of novel cerebrosides, acanthacerebroside A (1) and astrocerebroside A (2), isolated from starfish, is described. The phytosphingosine moieties in 1 and 2 were prepared by the coupling reaction of dialkylmagnesium reagents with the common epoxide intermediate, 2-(t-butoxycarbonyl)amino-1-O-(t-butyldiphenylsilyl)-2-deoxy-3-O-(4-methoxybenzyl)-d-4,5-anhydroribitol (5). The epoxide (5) was synthesized from naturally occurring cyclitol, l-quebrachitol via the conduramine derivative, which was prepared regio- and stereoselectively by the Pd-catalyzed azidation of the allyl carbonate derivative. Condensation of phytosphingosines with 2-acetoxy fatty acid residue, followed by glycosidation, furnished the total synthesis. This work established an effective synthetic pathway to a wide variety of cerebrosides containing various phytosphingosines and 2-hydroxy fatty acid residue; the first total synthesis of astrocerebroside A (2) fully confirmed the proposed structure.
Surface-Enhanced Raman Imaging (SERI) of Patterned Self-Assembled Monolayers of Various Derivatized Thiophenols on Silver
Authors: Tryk Donald A , Yang Xiaomin , Hashimoto Kazuhito , Fujishima Akira
Published: August 2005

Surface-enhanced Raman imaging (SERI) has recently been developed in our laboratory as an imaging technique which is chemically selective, has monolayer sensitivity, and can be used under ambient conditions. A particularly interesting application of this technique is to image patterned self-assembled monolayers (SAMs). In the present work, we have used both photopatterning and microcontact printing techniques for preparing patterned SAMs with several different terminal functional groups (NO2, OH, COOH, and CH3) on evaporated silver films and have imaged them using SERI. The intrinsic subsurface roughness of the film provides sufficient enhancement for the imaging.
Ab Initio CASSCF Study on Doublet and Quartet States of 1,3,5-Tris(methylene)benzene and 1,3,5-Benzenetriamine Trication
Authors: Ito Akihiro , Taniguchi Aya , Yoshizawa Kazunari , Tanaka Kazuyoshi , Yamabe Tokio
Published: August 2005

Ab Initio CASSCF results of 1,3,5-tris(methylene)benzene (TMB) and 1,3,5-benzenetriamine trication (BTA3+), which are model molecules of the actively researched triradicals with star-branched topology, are presented. This study included a geometry determination of the four low-lying states (4A1″, 4A2, 2A2, 2B1) of TMB and BTA3+. The doublet–quartet splitting energies (ΔED–Q) of TMB and BTA3+ were calculated to be 12.7 and 3.1 kcal mol−1, respectively. Furthermore, the doublet-doublet splitting energies of TMB and BTA3+, which arise from a Jahn–Teller distortion of the doubly degenerate 2E″ state, were suitably estimated to be 2.5 and 6.8 kcal mol−1, respectively, due to obviation of the spin-contamination problem. As a result of configuration mixing, it was found that the doublet states for TMB and BTA3+ have to be represented at least by two configurations or more. In addition, the doublet states of TMB were regarded as being a doublet triradical, while those of BTA3+ were close to a doublet monoradical; associated with this result, the lowest doublet states of TMB and BTA3+ were found to be 2A2 and 2B1, respectively.
Crystal Structure of Acrylonitrile
Authors: Yokoyama Yoshihiro , Ohashi Yuji
Published: August 2005

Structure analysis of acrylonitrile, which is a low-melting-point (189.5 K) material, was performed using an imaging-plate-Weissenberg-camera-type-diffractometer at 153 K. The crystal was grown on the diffractometer. The molecule is almost planar and the molecular planes are stacked at regular distances along the a axis. The molecule takes a disordered structure since the N atom and the approximate center of the C=C double bond lie on the crystallographic mirror plane. This causes the C=C bond to be aligned to be in parallel or perpendicular arrangements to the neighboring ones along the stacking. If the solid state polymerization induced by radiation is carried out, the isotactic structure may be obtained for the parallel stacking and the syndiotactic structure may be obtained for the perpendicular stacking. Since the crystal structure is disordered, either structure or a structure with the two structures mixed (atactic structure) should be formed in the solid state polymerization.
Rotational Predissociation Dynamics of H2O (C1B1) by VUV Laser-Induced Photofragment Fluorescence Spectroscopy
Authors: Liu Shilin , Hishikawa Akiyoshi , Yamanouchi Kaoru
Published: August 2005

The rotational predissociation of water molecules in the vibrationless level of the B1 state was investigated under jet-cooled conditions (27—154 K) by exciting them with a tunable VUV laser in the wavelength range of 124.3—123.7 nm and by detecting the total fluorescence from electronically excited photofragments OH(A2Σ+). Due to the simple one-photon selection rule and the efficient rotational cooling, individual low-J rotational transitions of the B1–A1 origin band were observed with almost no overlap in the laser-induced photofragment fluorescence (LIPF) spectrum. The widths and intensities of these rotational transitions exhibited pronounced dependence on the parent rotational levels in the B1 state. The least-squares analysis of the observed line-widths (FWHM) of the resolved rotational transitions, Γ ’s, showed that they are well described by the formula, Γ = Γ0 + αa, with optimized parameters Γ0 = 2.5(1) cm−1 and αa = 0.63(1) cm−1, indicating that (i) the homogeneous interaction couples the B1 state with the B1 state to form OH fragments in the electronically ground 2Πi state and (ii) the heterogeneous (a-axis orbital-rotation) interaction couples the B1 state with the A1 state to form OH fragments in the electronically excited A2Σ+ state. By taking account of the rotational line-broadening effect, the least-squares analysis was also performed to fit the observed spectral intensities to derive the branching ratio of the OH(A2Σ+) formation via the A1 state of H2O. It was found that the OH(A2Σ+) formation branching ratio can be expressed by an exponential form, exp (−γ), which was proposed first by Hodgson et al. [Mol. Phys., 54, 351 (1985)], and reproduces well the observed rotational intensity pattern when γ = 0.097(7). By using this branching ratio and the previous data for the absorption oscillator strength, the absolute cross section to yield OH(A2Σ+) photofragments was obtained as a function of the excitation energy.
A Reversible Metalloporphyrin Oxygen Carrier Both in the Solid State and in Solution: Preparation, Characterization, and Kinetics of Formation of a Molybdenum(VI) 5,10,15,20-Tetramesitylporphyrin Dioxygen Complex
Authors: Tachibana Junichi , Imamura Taira , Sasaki Yoichi
Published: August 2005

The molybdenum(VI) porphyrin dioxygen complex, [MoVIO(O2)(tmp)] (tmp = 5,10,15,20-tetramesitylporphyrinato), prepared from the reaction of [MoIVO(tmp)] with dioxygen at room temperature is characterized in detail. Bulky mesityl substituents on the porphyrin rings enable the isolation of the dioxygen complex. Photoirradiation of the toluene solution of the dioxygen complex with visible light regenerated [MoIVO(tmp)] immediately. Upon heating the solid sample of the dioxygen complex, dioxygen gas was liberated around 40—90 °C, leaving [MoIVO(tmp)]. The solid and a toluene solution of [MoIVO(tmp)] thus formed, again absorbed O2 from air to make [MoVIO(O2)(tmp)]. The IR and 1H NMR data confirmed that O2 was coordinated as a peroxide mode to the central molybdenum(VI) ion from the same side of the porphyrin plane with the oxo ligand and that both the axial ligands (peroxo and oxo) eclipsed the trans-N atoms of the porphyrin rings. The second-order rate constant for the formation of the dioxygen complex in toluene was evaluated to be (3.9 ± 0.1) × 10−1 dm3 mol−1 s−1 at 20 °C. The rate constant is extremely small as compared with those of the oxygenation of iron(II) porphyrins, by at least a factor of 10−5.
Complex Formation of Lanthanide Ions with Sulfonated Crown Ethers in Aqueous Solution
Authors: Sasaki Takayuki , Umetani Shigeo , Matsui Masakazu , Tsurubou Shigekazu , Kimura Takaumi , Yoshida Zenko
Published: August 2005

A new type of water-soluble crown ether (3′-sulfobenzo-12-crown-4 (SB12C4), 3′-sulfobenzo-15-crown-5 (SB15C5), 3′-sulfobenzo-18-crown-6 (SB18C6), di(3′-sulfo)dibenzo-18-crown-6 (DSDB18C6), di(3′-sulfo)dibenzo-21-crown-7 (DSDB21C7), and di(3′-sulfo)dibenzo-24-crown-8 (DSDB24C8)) has been prepared. The complex formation constants (β) of lanthanide ions with sulfonated crown ethers in aqueous solution were determined via the solvent-extraction method. The stability of the resulting complexes increases with the number of sulfonic acid groups, 18C6 < SB18C6 < DSDB18C6. For mono and disulfonated crown ether complexes, the stability varies as SB18C6 < SB15C5 < SB12C4 and DSDB18C6 < DSDB21C7 < DSDB24C8. The β values of all the complexes of lanthanide ions decrease with the atomic number, which is a characteristic of macrocyclic ligands, and is quite opposite to the conventional complexing tendency. The extractive separability of lanthanide ions was found to improve by adding sulfonated crown ethers into the aqueous phase as ion-size selective masking reagents. The number of water molecules in the first coordination sphere of the central Eu3+ in the complex was determined by a laser-induced luminescence study. In addition, the fluorescence spectra were measured in order to evaluate the structure of the complexes. The stabilization of the complexes formed is discussed while taking into account an outer-sphere electrostatic attraction between the sulfonic acid group and the metal ion.
Statistical Characterization of Eleven Kinds of Helix Elements with Amino Acid Residues in the Middle of Triplets
Authors: Narita Mitsuaki , Sode Koji , Ohuchi Shokichi , Murakawa Yuka , Hitomi Mitsuo
Published: August 2005

Based on the definition of a helix region in terms of dihedral angles φ and ψ, 681 helices could be easily extracted from 125 kinds of analyzed proteins by using two-dimensional φ and ψ diagrams of their three-dimensional structures. The 8000 (203) possible kinds of amino acid residues in the middle of triplets consisting of consecutive residues were used for a precise analysis of helical segments in globular proteins. They correspond to the 8000 kinds of amino acid residues in a sequence of proteins. The 681 helices were built up from 8836 amino acid residues, which could be classified into 11 kinds of helix elements (a—k). Each of the amino acid residues in a sequence of helical segments could be allotted to one of 11 helix elements (a—k). Glycine residues in the proteins were used for its precise assignment as internal standards. The 11 kinds of helix elements could be statistically characterized with amino acid residues in the middle of triplets. Amino acid residues, observed as a specific helix element 3-times or more often in the total helical segments, were evaluated regarding their propensities for a specific helix element by using their inherent preference (IP)-values for the specific helix element, which had been defined in a previous paper. Amino acid residues found 13-times or more often in the data set are also listed to show their propensities for specific helix elements.
Preparation, Ligand Substitution, and Structural Stability of (η3-Allyl)dicarbonylnitrosyliron Complexes
Authors: Nakanishi Saburo , Memita Seiji , Takata Toshikazu , Itoh Keiji
Published: August 2005

[Fe(η3-allyl)(CO)2(NO)] complexes were prepared by the reaction of tetrabutylammonium tricarbonylnitrosylferrate with tosylates, trifluoroacetates and phosphonates of allylic alcohols and with allylic halides. However, acetates and carbonates of the allylic alcohols are ineffective for the preparation of the complexes. The reaction of [Fe{η3-(1-substituted allyl)}(CO)2(NO)] with phosphorus ligands (L) gave a mixture of diastereomeric [Fe{η3-(1-substituted allyl)}(CO)(NO)(L)] complexes, which have planar chirality and central chirality of the iron atom. Variable-temperature 1H NMR spectroscopy revealed that no isomerization between these diastereomers occurred upon heating up to 80 °C. Also, neither syn–anti isomerization of the allylic ligand nor isomerization of planar chirality of the complexes took place. The unsubstituted allylic ligand rotates about the iron-allyl ligand axis at room temperature, while η3-(1-substituted allylic) ligands do not.
Tetraanion Tetralithium with 8 Center/12 Electron π-System Stabilized by Silyl Groups. Synthesis and Characterization
Authors: Sekiguchi Akira , Matsuo Tsukasa , Akaba Ryoichi
Published: August 2005

Reduction of octasilyltrimethylenecyclopentene (2) with lithium metal in tetrahydrofuran yields orange crystals of the tetraanion tetralithium (3) with 8 center/12 electron π-system. The molecular structure of 3 is unequivocally established by X-ray crystallography. The tetralithium 3 has a monomeric structure and forms contact ion pairs (CIP) in the crystals. The two lithium atoms (η5) are located above and below the center of the five-membered ring, whereas the other two lithium atoms (μ2) are bonded to the two exocyclic carbon atoms. The structural parameters of 3 are discussed in comparison to that of the neutral starting molecule of 2. The structure of 3 in solution has also been discussed on the basis of NMR spectroscopic data.
Molecular Recognition and Atropisomerization of [5,10,15,20-Tetrakis(1-pentyl-3-pyridinio)porphyrinato]zinc(II) in Water
Authors: Mizutani Tadashi , Horiguchi Takuya , Koyama Hiroshi , Uratani Ippei , Ogoshi Hisanobu
Published: August 2005

A cationic porphyrin host, [5,10,15,20-tetrakis(1-pentyl-3-pyridinio)porphyrinato]zinc(II), binds benzenecarboxylates, in water. The temperature dependence of the binding affinity showed that the binding was entropically driven: for the binding of 1,2,4,5-benzenetetracarboxylate, ΔH° = 4.36 kJ mol−1 and ΔS° = 95.4 J K−1 mol−1. The atropisomerization rates of the porphyrin were investigated by 1H NMR, and were decelerated by the addition of either anionic guests or simple inorganic salts. Electrostatic interactions and accompanying desolvation mainly controlled these equilibrium and kinetic behaviors.
Stereochemical Control in Microbial Reduction. 30. Reduction of Alkyl 2-Oxo-4-phenylbutyrate as Precursors of Angiotensin Converting Enzyme (ACE) Inhibitors
Authors: Dao Duc Hai , Kawai Yasushi , Hida Kouichi , Hornes Sander , Nakamura Kaoru , Ohno Atsuyoshi , Okamura Mutsuo , Akasaka Takeshi
Published: August 2005

Alkyl 2-oxo-4-phenylbutyrates are reduced to the corresponding alkyl (R)-2-hydroxy-4-phenylbutyrates, versatile chiral building blocks in organic synthesis, in high chemical yield (80—90%) with excellent stereoselectivity ( > 90%ee). The reaction has been run in aqueous diethyl ether at 30 °C for 24 h under the catalysis of bakers’ yeast (Saccharomyces cerevisiae) which was preincubated for 6 h in the presence of phenacyl chloride. The amount of water in the medium should be controlled strictly not to exceed 0.8 mL (g yeast)−1.
Preparation and Characterization of Side-Chain Liquid-Crystalline Polyoxetanes Anchoring a Pendant Spacer-Separated Mesogen at the Tertiary-Like C-3 Carbon of the Oxetane Unit
Authors: Ogawa Hiroshi , Kodera Yasutake , Kanoh Shigeyoshi , Ueyama Akihiko , Motoi Masatoshi
Published: August 2005

Polyoxetanes anchoring a pendant spacer-separated mesogen at the tertiary-like C-3 carbon of the oxetane unit were prepared by cationic ring-opening polymerization of the corresponding oxetane derivatives. The resulting polymers were liquid-crystalline substances showing textures assignable to the nematic or smectic mesophase over a wide temperature range from about 260 °C to room temperature. These mesogens also behaved in the manner similar to that of the mesogens in the analogous polyoxetanes attached by a methyl side chain at the quaternary C-3 carbon, although the less bulky polymer backbone in the present work indicated a somewhat higher isotropic phase-transition temperature than that of the methyl-substituted analogs. In both types of the polyoxetanes, their mesophase patterns were influenced by the core structure and alkoxy tail length in the pendant mesogen, but not by the bulkiness of the second side chains, H and CH3, attached at the C-3 carbon of the polyoxetane unit.
Origin of the Enantioselectivity of Lipases Explained by a Stereo-Sensing Mechanism Operative at the Transition State
Authors: Ema Tadashi , Kobayashi Juka , Maeno Soichi , Sakai Takashi , Utaka Masanori
Published: August 2005

The stereoelectronic considerations and the molecular modeling using an X-ray structure of Rhizomucor miehei lipase suggested that the lipase-catalyzed reactions proceed under the stereoelectronic control. This suggestion was supported by the semiempirical MO (MNDO-PM3) calculations carried out on the imidazole-catalyzed transesterification as a model reaction. The stereoelectronic effect operates at the transition state (TS) more effectively than at the tetrahedral intermediate (THI). The stabilization energy due to the stereoelectronic effect operating at the TS was estimated to be ca. 5 kcal mol−1. The enantioselectivities for 1-phenylethanol, 1-phenyl-2-propanol, and 1-cyclohexylethanol were estimated in terms of the lipase-induced strain caused at the TS. A TS model generally applicable to chiral secondary alcohols is proposed. The kinetic study supported the TS model. The result that the enantioselectivity in the lipase-catalyzed transesterifications arises from the difference in Vmax between the two enantiomers rather than from the difference in Km indicates that the ability of lipases to discriminate between the enantiomers at the TS is high, while the ability to recognize the chirality in the binding step is poor. Furthermore, the difference in Vmax between the enantiomers was found to result not from the enhanced reactivity of the (R)-enantiomers but from the reduced reactivity of the (S)-enantiomers.
Syntheses and Properties of Unsymmetrically Substituted Bi- and Quaterthiophenes
Authors: Higuchi Hiroyuki , Uraki Yoshiyuki , Yokota Hiroki , Koyama Haruki , Ojima Juro , Wada Tatsuo , Sasabe Hiroyuki
Published: August 2005

The unsymmetrically substituted bi- and quaterthiophene derivatives were synthesized. The unsymmetrically substituted bithiophenes carrying the electron-withdrawing substituent X on one of the outer thiophene rings exhibited the maxima of absorption bands at the longer wavelengths than the symmetrically disubstituted bithiophene derivatives, while the unsymmetrical quaterthiophenes had such maxima at the shorter wavelengths than the corresponding symmetrical ones. The trend of bathochromic shift of the longest wavelength absorption bands due to the electron-withdrawing substituent X was more pronounced in case of bi- or quaterthiophenes bearing push–pull substituents. The unsymmetrical quaterthiophenes exhibited the greater third-order nonlinear optical (TNLO) properties than the corresponding bithiophenes, similarly to the case between the symmetrical bi- and quaterthiophenes. However, the TNLO properties of the unsymmetrical bi- and quaterthiophenes showed no dependence on the electron-withdrawing strength of the substituent X, unlike those of the symmetrical ones.
Superconductivity as Symmetry Breaking. Classical Treatment
Authors: Aono Shigeyuki
Published: August 2005

The superconductivity is discussed from the viewpoint of the symmetry breaking in the framework of the classical field theory. The classical Schrödinger field of an electron is assumed to be a Grassmann algebra. The interaction with a radiation field is introduced through the gauge field theory. In the Nambu representation, the Lagrangian of the system is invariant under the rotation about the z axis in the spin space, so that the Goldstone theorem suggests that the condensation occurs on the x–y plane. In the absence of any external field, the system is invariant under the phase transformation. This symmetry breaks due to the condensation, and then the massless Goldstone boson which is the supercurrent will follow. The presence of the photon field, however the photon field itself becomes massive due to the gauge symmetry breaking (Higgs phenomenon), which is the Messner effect.
Preparation of Porous Supports in the SiO2–ZrO2–Na2O System
Authors: Tsurita Yasushi , Wada Keisuke
Published: August 2005

A new method for preparing porous supports in the SiO2–ZrO2 system was investigated. A microspherical silica gel impregnated with ZrOCl2 and NaCl was heated and subsequently washed with water. Crystallization of silica proceeded in supports prepared by heating the mixture of silica gel and NaCl. In contrast, crystallization of supports as well as their sintering was suppressed in the case of the gel impregnated with ZrOCl2 in addition to NaCl, and porous supports with the SiO2–ZrO2–Na2O composition were formed. A porous-glass-like texture similar to the texture resulting from the phase-separation method was observed inside the microspherical particles as well as on their surface. Microspherical supports, whose pore volume was more than 1 cm3 g−1 and whose mode pore radii ranged from 270 to 640 Å, were obtained by controlling the synthetic conditions for the silica gel, the amount of ZrOCl2 added to the gel, and the temperature of the heat-treatment of the mixture.
Molecular-Sieving Gas Sensor Prepared by Chemical Vapor Deposition of Silica on Tin Oxide Using an Organic Template
Authors: Kodakari Nobuaki , Sakamoto Takeshi , Shinkawa Kouji , Funabiki Hisato , Katada Naonobu , Niwa Miki
Published: August 2005

A tin(IV) oxide surface was modified by the chemical vapor deposition (CVD) of tetramethoxysilane after the pre-adsorption of benzoate anion as a template to obtain a novel gas sensor with a molecular-sieving function. The sensitivity to large molecules was strongly suppressed by the modification, whereas the sensitivity to small molecules was relatively less modified. It is considered that the silica overlayer with pores whose size was controlled by the template molecule prevented large molecules from reacting with the exposed tin oxide surface, resulting in the molecular-sieving property. The catalytic activity for the oxidation of the alcohol was measured in order to support the idea that the reactivity of organic molecules was suppressed by silica.
Preparation and Characterization of Inclusion Complexes of Poly(alkyl vinyl ether) with Cyclodextrins
Authors: Harada Akira , Okada Miyuko , Kamachi Mikiharu
Published: August 2005

γ-Cyclodextrin (γ-CD) has been found to form inclusion complexes with poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), and poly(n-propyl vinyl ether) (PnPVE) of various molecular weights to give stoichiometric compounds in crystalline states. α-Cyclodextrin (α-CD) and β-cyclodextrin (β-CD) did not form complexes with poly(alkyl vinyl ether)s of any molecular weight. γ-CD did not form complexes with the low molecular weight analogs, such as diethyl ether and trimethylene glycol dimethyl ether. The yields of the complexes of γ-CD with PMVE increased with increasing molecular weight (MW) of PMVE and reached saturation at about MW 2000. The yields of the complexes of γ-CD with PEVE and PnPVE increased with increase in MW, reached a maximum at a MW of about 1000 for PEVE and about 250 for PnPVE, and decreased with a further increase in the MW. Complexes were isolated and found to have a 3 : 1 (monomer unit : CD) ratio. The complexes were characterized by IR, 1H NMR, 13C NMR, and X-ray (powder), thermal and elemental analyses. The structures of the complexes are discussed.
Combined Effects of the Polarity of Terminal Groups and the Direction of Ester Linkages on Crystalline and Mesophase Structures of Biphenyl Esters with a Cyano or a Methoxy Group
Authors: Oki Mutsuko , Hori Kayako
Published: August 2005

The crystal structures have been determined for 4′-octyloxybiphenyl-4-yl 4-cyanobenzoate (abbr. OCO-CN) and 4-methoxyphenyl 4′-octyloxybiphenyl-4-carboxylate (abbr. COO-OCH3) with the identical phase sequence of crystal 1 (CR1)-crystal 2 (CR2)-monolayered smectic A (SA1)-nematic (N)-isotropic. It is found that the combination of two factors, (1) opposite polarity of the terminal groups (electron-donating OCH3or -accepting CN) and (2) opposite direction of the central ester linkages, results in almost the same structures of CR1. They are composed of bilayers, in which the polar groups face each other. Methoxy groups are in van der Waals contact, while cyano groups have an unfavorable head-to-head arrangement. It is interpreted that this arrangement of CN groups is responsible for the large molecular rearrangements at the CR1–CR2 transition.
Membrane Phenomena in Nonisothermal Systems: Part 3. Thermal Membrane Potential across Various Hydrophobic Anion-Exchange Membranes with 10 and 14% Divinylbenzene
Authors: Huda Masud Shamsul , Kiyono Ryotaro , Tasaka Masayasu , Yamaguchi Takanori , Sata Toshikatsu
Published: August 2005

The thermal membrane potential across anion-exchange membranes having various hydrophobic anion-exchange groups was measured for various electrolyte solutions. A good linear relationship between the thermal membrane potential (Δψ) and the logarithmic temperature difference (Δln T) was observed. The temperature coefficient of the thermal membrane potential (Δψ/Δln T) was found to be a function of the logarithmic activities of ions with a slope of RTc/F for 1-1 electrolytes and RTc/(2F) for 1-2 electrolytes, where Tc is the constant temperature of the solution on one side of the membrane. The absolute value of Δψ/Δln T decreased with increasing the molality of the external electrolyte solutions. The absolute value of Δψ/Δln T in KCl solutions was higher than that in KIO3 solutions. For halide ions the order of the absolute values of the thermal membrane potential (Δψ) was Cl− > Br− > I−, which corresponds to the order of the values of the B-coefficient in the Jones–Dole expression for the viscosity of the solutions, but opposite to that of the conventional partial molar volume. For large oxoanions the order of the absolute values of Δψ was found to be NO3− > IO3− > SO42−, which is opposite to the order of the B-coefficient as well as to that of the molar volume of these hydrated ions.
Magnetic Resonance Either in Normal or Superconducting Species. Spin-Lattice Relaxation Time
Authors: Aono Shigeyuki
Published: August 2005

The spin-lattice relaxation time T1 either in the superconducting and normal phases is investigated by the use of the Green’s function method. The lattice, in this case, means the conduction electrons and the interaction is mainly due to the Fermi contact term. Electrons and nuclei are treated on the same footing, namely both are in the second quantized form. The coherent terms are summarized in a general fashion at the beginning.
Hubbard and Heisenberg Models for Four-Site Four-Electron Systems. Group-Theoretical Interrelationships and Applications to Multinuclear Transition-Metal Clusters
Authors: Yoshioka Yasunori , Kubo Shigehiro , Kiribayashi Shinji , Takano Yu , Yamaguchi Kizashi
Published: August 2005

Hubbard models for four-site four-electron {4,4} systems are analytically solved to elucidate group-theoretical interrelationships between effective model Hamiltonians for radical clusters, metal clusters, Cu4O4, and so on. The group operations used for this purpose are permutation group (SN), spatial symmetry (PN), spin rotation (S), and time-reversal (T). The magnetic (color) group (T × S) is utilized for determination of the magnetic symmetry of spin structures obtained on the basis of the classical Heisenberg model; namely a vector representation of radical spins. The magnetic double group theory (T × S × PN) is used for characterization of general Hartree–Fock solutions (GHF) involving axial, helical, and torsional spin density waves for {4,4} systems. The spin-optimized SCF solutions are constructed from the spin projection of the GHF solutions (T × S × PN) by the use of the permutation symmetry (SN). The SN group is also used for the quantum Heisenberg model for {4,4} systems. In order to show the interrelationships between these model Hamiltonians, the electronic states of {4,4} systems with the D4h, Td, and D3h symmetries are constructed by the use of the magnetically ordered general spin orbitals which have been determined by the GHF calculations. The spin-optimized SCF solutions for {4,4} systems examined here are equivalent to the full CI wavefunctions satisfying both spatial and spin symmetries. The relative contributions of the spin polarization (SP) and doubly excited configurations in the GHF, projected GHF and SO-SCF wavefunctions are clarified to elucidate possible mechanisms of spin alignments and antiferromagnetic spin correlations. Implications of these computational results are discussed in relation to quantum and classical representations of spin alignments in molecular magnetic materials such as iron–sulfur clusters. Molecular magnets having helical and torsional spin structures are designed and discussed in relation to the most general spin alignment in the species.
Concentrated Salt Effects on the Solvolysis Reaction Rates in Methanol–Water Solution
Authors: Manege Ludovick Christian , Ueda Tadaharu , Hojo Masashi
Published: August 2005

The solvolysis rates of aliphatic halides and related compounds (RX) were determined in an 80 vol% MeOH–20 vol% H2O solvent in the presence of very highly concentrated salts (0.25—5.0 mol dm−3) at 25—75 °C. For typical SN1 substrates, such as 1-adamantyl bromide and t-butyl chloride, the pseudo-first-order reaction rates (k/s−1) increased exponentially with increasing concentration of LiClO4, NaClO4, Mg(ClO4)2, and Ba(ClO4)2. The cation effects increased as Na+ < Li+ < Ba2+ ≤ Mg2+. A nonmetallic salt, Et4NBr, caused the k/s−1 value for 1-adamantly bromide to be slightly increased at lower concentrations ( < 1.0 mol dm−3), but to be greatly decreased at higher salt concentrations ( ≥ 2.0 mol dm−3). The large positive effects of metal perchlorates were explained by a change in the solvent structure and the formation of “stable” carbocations through a “chemical” interaction between X− (Cl−, Br−, or I−) and M+ (Li+, Na+) or M2+ (Mg2+, Ba2+) in the “modified” solvent. On the other hand, for SN1–SN2 intermediates, the solvolysis reaction rates were decreased by a decrease in the activity of the solvent containing a large amount of salts. The apparent rate constant (“k/s−1”) for isopropyl bromide at 75 °C remained an almost constant value in the presence of 0—5.0 mol dm−3 LiClO4. The rate constant for ethyl bromide was decreased substantially by the addition of the alkali metal and alkaline-earth metal perchlorates. A good linearity was observed between log (k1/k0) and the m values for RX by Grunwald and Winstein, where k1 and k0 are the solvolysis rates in the presence of 1.0 mol dm−3 LiClO4 and in the absence of the salt, respectively. Upon the solvolysis of neophyl chloride (1-chloro-2-methyl-2-phenylpropane), the change in the reaction scheme (e.g., methyl shift) was suspected during the increase in the LiClO4 or Ba(ClO4)2 concentration.
Sequential Titrimetric and Spectrophotometric Determinations of Trace Amounts of Tin(II) and Tin(IV) by Amplification Reactions
Authors: El-Shahawi Mohammed S , Abu Zuhri Ali Z
Published: August 2005

Two simple and accurate titrimetric and spectrophotmetric methods have been developed for the determination of tin. The methods were based upon the oxidation of tin to tetravalent tin with sodium periodate at pH 2.2—3.5; excess periodate ions were then masked with 5% sodium molybdate at the same pH. The released iodate ions were determined spectrophotometry (at 350 nm) as triiodide after the addition of KI. This proposed procedure offered a six-fold amplification for each tin(II) ion. Alternatively, the released iodine was extracted with chloroform and shaken with an aqueous solution of 1% (w/v) sodium sulfite. The iodide ions produced in the aqueous phase were then oxidized with sodium periodate after removing the unreacted sodium sulfite by boiling with H2SO4 (2 M). The released iodate was finally determined by iodometry or spectrophotometry. This procedure offered 144-fold amplification per tin(II) ion. The determination of tin(IV) after prior reduction to tin(II) with sulfur dioxide was also found to be suitable. Analyses of the binary mixtures of tin(II)–tin(IV) in an aqueous solution, tin in organotin compounds and tin(II) and tin(IV) in artificial sea-waters were successfully carried out.
Catalytic Effect of N,N-Dimethyl-4-(2-pyridylazo)aniline on the Extraction Rate of Ni(II) with 1-(2-Pyridylazo)-2-naphthol: Ligand-Substitution Mechanism at the Liquid–Liquid Interface
Authors: Onoe Yuki , Tsukahara Satoshi , Watarai Hitoshi
Published: August 2005

The catalytic effect of N,N-dimethyl-4-(2-pyridylazo)aniline (PADA) on the extraction rate of Ni(II) with 1-(2-pyridylazo)-2-naphthol (Hpan) in toluene was investigated by the high-speed stirring method. The extracted species was only Ni(pan)2 under the highly stirred system. The extraction rate of Ni(pan)2 was proportional to both concentrations of Ni(pada)2+ adsorbed at the liquid–liquid interface and Hpan in the toluene phase, suggesting that the rate-determining step was the reaction between Ni(pada)2+ and Hpan at the interface, followed by a successive fast ligand-substitution reaction with another Hpan. The rate constant for the rate-determining step was estimated as 90 ± 6 M−1 s−1. That the value was rather smaller than the ordinary formation rate constants of Ni(II) complexes was explained by the ring-closure mechanism in the coordination of Hpan.
Syntheses and Structures of Trinuclear Molybdenum Cluster Complexes [Mo3S4Cl4(C5H5N)5] and [Mo3S4Cl3(C5H5N)6]I
Authors: Mizutani Jun , Yajima Setsuko , Imoto Hideo , Saito Taro
Published: August 2005

A trinuclear molybdenum chloro sulfido cluster complex [Mo3S4Cl4(C5H5N)5] (1) was synthesized by the excision of a nonmolecular cluster compound Mo3S7Cl4 with triphenylphosphine and pyridine. Three molybdenum atoms and four sulfur atoms form an incomplete cubane-type cluster core, which is coordinated by four chloro and five pyridine ligands. By the reaction of 1 with I2 in pyridine, [Mo3S4Cl3(C5H5N)6]I (2) was synthesized. Three μ-S in the cluster cation and the iodine anion have short contacts, within the sum of the van der Waals radii of sulfur and iodine.
Preparations, Structures, and Properties of Cu(II) Complexes with Tripodal Tetradentate Ligand, Tris(6-pivaloylamino-2-pyridylmethyl)amine (Htppa), and Reaction of Its Cu(I) Complex with Dioxygen
Authors: Harata Manabu , Jitsukawa Koichiro , Masuda Hideki , Einaga Hisahiko
Published: August 2005

Mononuclear copper complexes with a tripodal tetradentate ligand, tris(6-pivaloylamino-2-pyridylmethyl)amine (Htppa), and several anions have been prepared as a model metal centre of copper enzymes, whose structures have been examined by electronic absorption, ESR and NMR spectral, cyclic voltammetry, and X-ray diffraction methods. Those with an anion such as OH−, Cl−, Br−, and I− were shown to form a trigonal-bipyramidal geometry. The X-ray structures of [Cu(Htppa)](ClO4)2·2H2O·CH3OH, [CuCl(Htppa)]ClO4, [Cu(OH)(Htppa)]ClO4, [Cu(OH)(tppa)], and [Cu(tppa)](BPh4), obtained as a single crystal, revealed all trigonal-bipyramidal geometry with four nitrogen atoms of Htppa in trigonal plane and axial position and with the anion in another apical position. The reaction with NaN3 gave [Cu(N3)2(Htppa)], whose crystal structure was a square-pyramid with three nitrogen atoms of Htppa and N3− in square-planar positions and with another N3− in apical position. The redox potentials of [CuCl(Htppa)]ClO4 in MeCN or CH2Cl2 showed almost reversible CuI/CuII couples at 0.225 and 0.300 V vs. Ag/AgCl, respectively, which are characteristically high for the usual copper complexes. The addition of dioxygen to the Cu(I)–Htppa complex prepared from [Cu(MeCN)4]ClO4 and Htppa (1 : 1) in methanol solution at −78 °C resulted in an immediate absorption spectral change, with two well-separated absorptions at 657 (ε = 110 M−1 cm−1) and 803 nm (ε = 120 M−1 cm−1) and an intense band at 315 nm (ε = ca. 4000 M−1 cm−1) as a shoulder. Simultaneous ESR experiments of the same complex solution exhibited a silent spectrum, and the NMR spectrum at −80 °C was diamagnetic. These facts indicate the formation of CuII–O2−species. Interestingly, the CO gas bubbling into a CH3OH/THF/EtCN (4 : 3 : 3) solution of the superoxo complex species at −78 °C led to a significant color change from yellow-green to pale yellow, and alternate bubblings of O2 and CO to the solution exhibited a reversible spectral change with an isosbestic point at 521 nm due to the reversible formation of the CuII–O2− species.
Dioxygen Oxidation of Coordinated Nitrosyl to Nitro on Dmf-Bridged Dinuclear CoPb Complex
Authors: Furutachi Hideki , Okawa Hisashi
Published: August 2005

The CoIIPbII complex [CoPb(L)(CH3OH)(ClO4)2] reacts with nitrogen monoxide to give the nitrosyl complex [CoPb(L)(NO)(dmf)2(ClO4)]ClO4 (1), where H2L is a dinucleating macrocycle derived from the [2 : 1 : 1] condensation of 2,6-diformyl-4-methylphenol, ethylenediamine, and diethylenetriamine and has a “salen”- and a “saldien”-like metal-binding site sharing the phenolic entities. 1 crystallizes in the triclinic space group , a = 12.729(4), b = 17.103(6), c = 10.548(4) Å, α = 107.42(4)°, β = 106.18(2)°, γ = 101.33(3)°, V = 2003(1) Å3, and Z = 2. The refinement converges with R = 0.045 and Rw = 0.049 for 3768 reflections with I > 3.00σ(I). The Co resides in the “salen” site and the Pb in the “saldien” site. The metal ions are bridged by the two phenolic oxygens of L2− and a dmf oxygen, in the Co–Pb intermetallic separation of 3.511(2) Å. The Co–O(dmf) and O(dmf)–Pb bond distances are 2.14(1) and 3.072(8) Å, respectively. The NO coordinates to the Co at the axial site trans to the bridging dmf oxygen, providing a six-coordinate geometry about the metal; the Co–N(nitrosyl) distance is 1.92(1) Å and the Co–N–O angle is 117(1)°. The Pb has an eight-coordinate geometry together with the bridging dmf oxygen, a terminal dmf oxygen and a perchlorate oxygen. The nitrosyl complex 1 is oxidized with molecular oxygen to the nitro complex [CoPb(L)(NO2)(dmf)2(ClO4)]ClO4 (2). 2 crystallizes in the triclinic space group , a = 12.748(4), b = 17.139(5), c = 10.359(3) Å, α = 106.34(3)°, β = 106.44(3)°, γ = 101.42(3)°, V = 1986(1) Å3, and Z = 2. The refinement converges with R = 0.039 and Rw = 0.042 based on 6202 reflections with I > 3.00σ(I). 2 has a dinuclear core very similar to that of 1, bearing an NO2 group instead of an NO group. The Co–N(nitro) bond distance is 1.889(6) Å. 1H NMR, 13C NMR, and 13C–1H COSY spectroscopies indicate that the dmf-bridged dinuclear cores of 1 and 2 are retained in solution.
Interglycosidic Acetals IV. Preparation and Regioselective Cleavage of Phenyl 2,2′ : 4,6 : 4′,6′-Tri-O-benzylidene-1-thio-β-laminaribiosides
Authors: Sakairi Nobuo , Okazaki Yasunori , Furukawa Jun-ichi , Kuzuhara Hiroyoshi , Nishi Norio , Tokura Seiichi
Published: August 2005

A (+)-10-Camphorsulfonic acid-catalysed acetal exchange reaction of phenyl 1-thio-β-laminaribioside using 3.5 molar equivalents of α,α-dimethoxytoluene gave a tris(benzylidene acetal), which was isolated and characterized as phenyl 3′-O-acetyl-2,2′ : 4,6 : 4′,6′-tri-O-benzylidene-1-thio-β-laminaribioside, and the corresponding 3′-O-benzyl derivative 6. Upon a treatment with pyridinium p-toluenesulfonate, the interglycosidic 2,2′-acetal in 6 underwent selective cleavage to give the 2,2′-diol. Additionally, a reductive ring-opening reaction of 6 with lithium aluminium hydride/anhydrous aluminium chloride, followed by O-acetylation, gave the 2,6,6′-O-acetyl-4,2′,3′,4′-tetra-O-benzyl derivative in 73% yield. A different regioselectivity was observed in the reduction of 6 with borane-trimethylamine adduct/anhydrous aluminium chloride or sodium cyanotrihydroborate/methanesulfonic acid, giving the corresponding 2,4,4′-triol as the major product.