bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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 ( &gt; 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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− &gt; Br− &gt; 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− &gt; IO3− &gt; 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

Abstract
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

Abstract
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

Abstract
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+ &lt; Li+ &lt; Ba2+ ≤ Mg2+. A nonmetallic salt, Et4NBr, caused the k/s−1 value for 1-adamantly bromide to be slightly increased at lower concentrations ( &lt; 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.