bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Effects of Substituents on Indole Nitrogen on the Photochromic Properties of Indolylfulgides
Authors: Uchida Soichi , Yokoyama Yasushi , Kiji Jitsuo , Okano Tamon , Kitamura Hitoshi 
Published: July 2006

Abstract
The attempt to synthesize N-p-tolylsulfonylindolylfulgide by Stobbe condensation was unsuccessful because hydrolysis of the Stobbe-condensation product eliminated the sulfonyl moiety to give, after several steps, the N-unsubstituted fulgide. Pd(II)-catalyzed carbonylation of 2-butyne-1,4-diol derivative bearing the N-p-tolylsulfonylindole, however, afforded the desired N-p-tolylsulfonylindolylfulgide. A comparison of absorption spectroscopic and photochromic properties of these fulgides with those of the known N-methylindolylfulgide gave the following results. The electron-withdrawing substituent on nitrogen (i) shortened the absorption maximum of the colored form, (ii) suppressed thermal E–Z isomerization, and (iii) enlarged quantum yields of photochromic reactions.
Alkyl Radical Substitution on Disulfide in the Presence of Cobalt(II) Complexes
Authors: Tada Masaru , Sugano Kiyohiko , Yoshihara Takao 
Published: July 2006

Abstract
Photolysis of methyl(L)cobaloxime (L = trans ligand) (1) or methyl(L)-O,O′-bis(difluoroboryl)cobaloxime (2) in the presence of bis(4-chlorophenyl) disulfide gave 4-chlorophenyl methyl sulfide together with 4-chlorophenylthio(L)cobaloxime (5) or 4-chlorophenylthio(L)-O,O′-bis(difluoroboryl)cobaloxime (6). Similar photolysis in the presence of 2,2,6,6-tetramethyl-1-piperidyloxyl (TEMPO) gives 1-methoxy-2,2,6,6-tetramethylpiperidine. The reactivity of the cobaloximes 1 and 2 to the disulfide and TEMPO increases when the cobaloximes have a trans ligand (L) of larger steric requirement and low pka, or when the equatorial ligand is an electronegative O-(difluoroboryl)dimethylglyoxime. Two probable mechanisms are proposed for the reaction. The first is a direct radical substitution on the disulfide with a methyl radical, and the second involves the initial interaction between the disulfide and the (L)cobaloxime radical to afford arylthio(L)cobaloxime (5 or 6) and an arylthio radical. The latter radical reacts with methyl(L)cobaloxime to give aryl methyl sulfide.
Chemically Induced Dynamic Electron Polarization Studies of Photochemical Reactions: Acetone in 2-Propanol and Triethylamine
Authors: Hirota Noboru , Tominaga Keisuke , Yamauchi Seigo 
Published: July 2006

Abstract
The results of Chemically Induced Dynamic Electron Polarization (CIDEP) studies of acetone in 2-propanol and triethylamine are reviewed to show how CIDEP studies can reveal interesting details of the initial processes of photochemical reactions. After a brief description of various mechanisms that give rise to CIDEP, the following topics are discussed: a) spectral pattern and the main reacting state, b) CIDEP mechanisms and the temperature and frequency dependences of the spectra, c) direct EPR observation of the radical pair spectra in solution, d) time-developments of the CIDEP signals and spin and reaction dynamics of the initial processes of photochemical reactions, e) quantitative analyses of the magnitudes of CIDEP in terms of a stochastic Liouville equation, and f) some related applications. An overview of the remaining problems and the future outlook is also presented.
The Effects of CO2-Conditioning of Polymers on Positron Annihilation and Gas Permeation Properties
Authors: Tanaka Kazuhiro , Ito Masamichi , Kita Hidetoshi , Okamoto Ken-ichi , Ito Yasuo 
Published: July 2006

Abstract
The effects of CO2-conditioning, i.e. exposing a polymer film to high pressure CO2 and degassing it in vacuo, on positron annihilation and gas permeation properties of polyimides and polyethylene were investigated. Both lifetime and intensity of ortho-positronium (o-Ps) (τ3 and I3, respectively) increased for polyimides by the CO2-conditioning. The size distribution of free space holes, which was evaluated from annihilation rate distribution of o-Ps, became broader and shifted to larger size. Permeability, diffusion, and solubility coefficients of gases for polyimides increased by the CO2-conditioning. The increases in diffusion coefficient are attributed to increases in volume fraction of free space holes, VF. The increases in τ3 and in I3 were much larger than those expected from the increases in VF. This may be explained by a model based on an interplay between electron affinity and size of free space holes for Ps formation. In the CO2-conditioned films, permeability and diffusion coefficients, VF, and I3 gradually decreased with lapse of time but after five months they were still larger than those in the as-cast films, whereas τ3 remained almost constant. No effect of the CO2-conditioning was observed for polyethylene.
Experimental Study of Amorphous Silica Crystallization in Na2CO3–NaHCO3 Solutions as a Source of Chert Formation in Lake Magadi
Authors: Muraishi Haruto 
Published: July 2006

Abstract
Amorphous silica was treated with Na2CO3–NaHCO3 and Na2CO3–NaHCO3–NaCl solutions, which are related to the alkaline brine in Lake Magadi in East Africa; its transformation was followed as a function of time under various temperatures (100—160 °C) and pHs (8—12). The reaction occurred in steps. Three kinds of sodium silicates (magadiite, kenyaite, and SiO2-X2) appeared as intermediate phases in solutions with various pH, and finally converted into quartz. The rate of formation of naturally occurring silicates and quartz (chert) was roughly estimated by extrapolating the basis of the data on the temperature dependence of the conversion rate. From those crystallization observations, the preparation conditions for obtaining well-crystallized silicates were determined, and kenyaite was synthesized, which has note yet been obtained as a highly crystallized compound.
Long-Life Excited States of CdS Photocatalytic Particles
Authors: Nakabayashi Seiichiro , Yanagida Masatoshi , Uosaki Kohei 
Published: July 2006

Abstract
The CdS particles are irradiated by the green light from an Ar laser. The irradiation produces the electron-hole pairs and other excited states in the particle. The lifetime of the excited state is ca. 10 μs, which is extremely long compared with the recombination time of the electron and hole pairs. This long-life state forms an optical absorption band in the excitation-modulated transmission spectra. The relationship between the spectral intensity and the strength of the excitation light suggests that this absorption band is caused by the photoionization of the intervalence states and the change in the electrostatic field in the CdS particles.
Highly Twisted Ethylene Dianion Dilithium Stabilized by Phenyl and Silyl Groups
Authors: Sekiguchi Akira , Ichinohe Masaaki , Nakanishi Tetsuo , Kabuto Chizuko , Sakurai Hideki 
Published: July 2006

Abstract
Phenyl- and silyl-substituted ethylene dianion dilithiums, [1-phenyl-1,2,2-tris(trimethylsilyl)ethylene]{bis[(dimethoxyethane)lithium(I)]} (2) and [1,1-diphenyl-2,2-bis(trimethylsilyl)ethylene][tris(tetrahydrofuran)dilithium(I)] (4), were prepared and characterized by X-ray crystallography as well as NMR spectra. The crystal structures of 2 and 4 revealed interesting structural features. One of the lithium cations was located near to the two central carbon atoms, ipso and ortho carbons of the phenyl ring, while the other one was found above the benzene ring. The central C–C bond is twisted by ca. 90° for 2 and ca. 70° for 4.
Dual Nature of (Phenylseleno)cobaloxime in the Reaction with 2-Propynyl Derivatives
Authors: Tada Masaru , Nagasaka Ritsuko 
Published: July 2006

Abstract
Photolysis or thermolysis of (phenylseleno)cobaloxime gives a pair of radicals: phenylseleno radical and cobaloxime radical, which are considered to be equilibrated with the ion pair by a single electron transfer. The radical addition on the acetylenic moiety takes place when the 2-propynyl derivatives have weak leaving groups (OH, OPh, OAc). On the other hand, the ionic substitution with phenylseleno anion takes place on bromides and tosylates.
Enantioselective Aerobic Oxidation of Sulfides Catalyzed by Optically Active β-Oxo Aldiminatomanganese(III) Complexes
Authors: Nagata Takushi , Imagawa Kiyomi , Yamada Tohru , Mukaiyama Teruaki 
Published: July 2006

Abstract
Enantioselective aerobic oxidation of sulfides into optically active sulfoxides was achieved by using pivalaldehyde in the presence of a catalytic amount of optically active β-oxo aldiminatomanganese(III) complexes. An acylperoxomanganese complex, formed from the original manganese complex, molecular oxygen, and pivalaldehyde, was supposed to be a key intermediate in the present oxidation. The crystal structure of chloro-{N,N′-bis[3-oxo-2-(2,4,6-trimethylbenzoyl)butylidene]-(1S,2S)-1,2-diphenylethylenediaminato}manganese(III) was determined by X-ray diffraction methods, which suggested that the bulkiness of the substituents in β-oxo aldimine ligand had played an important role in controlling the approach of sulfides to the manganese complex. Kinetic resolution took place during the subsequent oxidation process of sulfoxide into the corresponding sulfone, and the optical purity of the remaining sulfoxide increased.
Uricase Model Reactions of Polylysine–Cu(II) Complexes
Authors: Tokimitsu Yoshirou , Ise Norio , Tanaka Naoki , Kunugi Shigeru 
Published: July 2006

Abstract
Oxidation of uric acid was catalyzed by Cu(II) complexes of polylysines. The presence of the polylysine as the second ligand (in addition to the first ligand; the substrate) showed an enhancement of the intrinsic catalytic activity of Cu(II) ions. Accounting for the apparent substrate inhibition phenomenon, due to the absorbance interference by the intermediate, approximate Km value for the model systems were determined to be around 30—40 μM, which are better than that of the free Cu(II) system, 60—80 μM, and comparable or even better than the Km values for some enzymatic reactions. From the CD spectrum the conformation of the polymer ligands is known to influence the catalytic activity. A preference of partly ordered structure is implied.
The Optical and Photoelectrochemical Properties of Electrodeposited CdS and SnS Thin Films
Authors: Adachi Atsushi , Kudo Akihiko , Sakata Tadayoshi 
Published: July 2006

Abstract
An electrodeposition technique was employed to synthesize CdS and SnS thin films. The optical and photoelectrochemical properties of these films were studied. Red emission peaks of as-deposited CdS thin films were observed around 650—700 nm at 77 K. Anodic photocurrents were observed for the CdS thin films used as semiconductor electrodes. Lowering current densities for the deposition increased both the photoluminescence intensity and the photocurrents. SnS thin films were prepared by a pulsed electrodeposition technique. The films had a large absorption coefficient of 105 cm−1 order. Stirring the electrolyte solution had a drastic effect on the film growth. This suggests that the diffusion of elemental sulfur which reacts with electrochemically formed Sn is the rate determining step of the SnS formation.
Exciton Transport Mechanism in 1,4-Dibromonaphthalene (DBN)-1-Bromo-4-chloronaphthalene (BCN) Mixed Crystal at 77 K
Authors: Dutta Ashim K , Talapatra Gautam B , Misra Tridibendra N 
Published: July 2006

Abstract
The exciton transport in the presence of both orientational and substitutional disorders is investigated at 77 K. The systems of study include different compositions of 1,4-dibromonaphthalene (DBN) and 1-bromo-4-chloronaphthalene (BCN). In DBN, crystal phosphorescence emission is in conformity with quasi-one-dimensional exciton motion. Fluorescence emission from an impurity and phosphorescence emissions from the triplet state of DBN and from an impurity site present in the DBN crystal have been observed. However the fluorescence emission from the first excited singlet state of DBN is absent. In BCN-doped DBN crystal, the emission corresponding to first triplet of DBN disappears. With the increase of BCN concentration, fluorescence intensity of impurity S1IMP decreases, while the impurity phosphorescence emission intensity increases. The role of the deep trap present in DBN and the effect of orientational disorder due to BCN on the energy transfer processes have been discussed. The experimental results are explained quite satisfactorily in terms of the percolation model, which suggests a two-dimensional exciton transport topology in the mixed crystal.
Crystal Structures of Chiral Mesogenic 4-[(S)-2-Methylbutyl]phenyl and 4-[(S)-1-Methylheptyloxy]phenyl 4′-Octylbiphenyl-4-carboxylates
Authors: Ito Kyoko , Hori Kayako 
Published: July 2006

Abstract
Single crystal X-ray analysis has been carried out for the title compounds with different chiral groups, which result in different phase sequences: crystal (cryst.)-smectic G(SG)-SJ*-SF*-SI*-SC*-SA-cholesteric (chol.)-isotropic (iso.) for the 2-methylbutyl compound (1) and cryst.-SB-SA-iso. for the 1-methylheptyloxy compound (2). Each crystal has a smectic-like layer structure, in which the molecular tilt angle is 25° in 1 and 15° in 2. Biphenyl moieties are almost coplanar and normal chains have all-trans conformations in both crystals. However, long chains of the chiral groups of 2 have twisted conformations and are arranged between layers. Relationships between the crystal structures and the mesophase behavior are discussed in terms of conjugation of the polar groups and overlapping of biphenyl moieties for the related compounds.
Density and Volumic Properties of N,N-Dimethylformamide + 2-Methoxyethanol + 1,2-Dimethoxyethane Liquid Ternary Mixtures
Authors: Corradini Fulvio , Marchetti Andrea , Tagliazucchi Mara , Tassi Lorenzo 
Published: July 2006

Abstract
Densities (ρ) at various temperatures ranging from −10 up to +80 °C have been measured for N,N-dimethylformamide + 2-methoxyethanol + 1,2-dimethoxyethane ternary solvent system, employing 66 mixtures covering the whole miscibility field. Polynomial equations describing the dependence on temperature, ρ = ρ(t/°C), and molar composition, ρ = ρ(X1,X2), have been checked. Furthermore, the excess molar volumes (VE), derived from ρ values, can provide useful suggestions about the formation of solvent–cosolvent complexes. Excess molar volumes have been interpreted on the basis of specific interactions between unlike molecules, taking into account geometric effects and steric hindrances. The VE quantities have been isothermally fitted by an empirical relation of the type VE = VE(X1,X2,X3) formally derived from the well known Redlich–Kister equation. As a rule, for all the here tested relationships, the calculated values agree very well with the experimental ones, indicating that all the equations can be safely employed for predictive calculations in correspondence of the experimental data gaps.
Charge Transport at Polypyrrole Film Electrodes: Effect of the Electrolyte Concentration
Authors: Komura Teruhisa , Usui Takahiro , Takahasi Kousin 
Published: July 2006

Abstract
From measurements of the a.c. response of polypyrrole film electrodes in KNO3 solution, we found that solvent swelling of the polymer greatly influences the kinetic behaviors of the polymer film electrodes. Electric migration in bulk film was due to background electrolyte ions which permeated through the film. Inside the film in contact with a supporting electrolyte solution, the mobility of the electrons may be much smaller than that of ions. The charge-transfer resistance of a partially oxidized film decreases along with increasing concentration of the electrolyte solution, because of a resultant increase in the activity of polarons. Such an increased activity of polarons also brings about a smaller Warburg coefficient, and thus a smaller limiting diffusion resistance (RL). The pseudocapacitance appearing at low frequencies increases along with an increase in the concentration of the electrolyte solution, which is opposed to the change in RL. These results corroborate that variations in the charge-transport parameters with the electrolyte concentration can be ascribed to an increase in the polaron activity with increasing ion concentration inside the polymer film.
Coupling of Inter- and Intramolecular Vibrations in the p-Xylene Crystal
Authors: Shimizu Fumio , Yoshikai Kazumasa , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi 
Published: July 2006

Abstract
The temperature effect on the low-frequency Raman bands of the four deuterated p-xylene crystals indicates that the coupling between the intramolecular torsional vibration of the CD3 group and the intermolecular rotational vibrations takes place below about −80 °C.
Gelation of Fully Acylated Cellobiose in Alkane Solution
Authors: Ide Nobuhiro , Fukuda Takeshi , Miyamoto Takeaki 
Published: July 2006

Abstract
Cellobiose octa(decanoate), a discotic columnar mesogen, was found to form in hexadecane solution various molecular assemblies such as a lyotropic liquid crystal of discotic columnar type, multimolecular micelles, and a thermoreversible gel, depending on the concentration and temperature. The gelation, observed even at very low concentrations, say, &lt; 0.01 weight fraction of the mesogenic compound, is believed to proceed by local coagulation of long threadlike micelles into micro-liquid-crystallites, which work as cross-linking points combining the threadlike micelles. This will be a new type of gel that could be termed a “liquid crystalline gel.”
Synthesis and Characterization of Some 2,10-Dichloro-6-alkoxydibenzo[d,g][1,3,6,2]dioxathiaphosphocin 6-Oxides
Authors: Reddy C Devendranath , Reddy B Sankara , Anuradha K , Berlin K D , Naidu S Mani , Krishnaiah M 
Published: July 2006

Abstract
The syntheses of 2,10-dichloro-6-alkoxydibenzo[d,g][1,3,6,2]dioxathiaphosphocin 6-oxides are described. Their IR, 1H, 13C, and 31P NMR spectral characteristics are reported. Long-range couplings (2JPOC and 3JPOCC) between phosphorus and carbons were observed. An X-ray diffraction analysis of a crystal of 2,10-dichloro-6-ethoxydibenzo[d,g][1,3,6,2]dioxathiaphosphocin 6-oxide indicated a boat-chair conformation to the dioxathiaphosphocin ring with the phosphoryl oxygen in axial and the ethoxy group in equatorial orientations. The molecule possesses a symmetry of the mirror plane passing through the sulfur, phosphorus, phosphoryl oxygen, and ethoxy group.
1,3-Dipolar Cycloaddition Reactions of 2,4,6-Cycloheptatrien-1-imines with Benzonitrile Oxides Leading to 1,2,4-Oxadiazaspiro[4.6]undeca-2,6,8,10-tetraenes
Authors: Ito Kazuaki , Saito Katsuhiro 
Published: July 2006

Abstract
1,3-Dipolar cycloaddition reactions of N-aryl-2,4,6-cycloheptatrien-1-imines with p-substituted benzonitrile oxides afforded [2+3]-type cycloadducts in considerable yields. A study of the substituent effect on the reaction rate revealed that the reactions proceeded through nucleophilic reactions of imines to nitrile oxides. Thermal isomerizations and addition reactions of the adducts showed that the contribution of a valence isomerization between cycloheptatriene and norcaradiene lay to the side of the cycloheptatriene form. A comparison of the UV spectra between the adduct and its derivative, which was reduced by catalytic hydrogenation, implies that the spiroconjugation between cycloheptatriene and a five-membered heterocyclic moiety causes a shift of the equilibrium.
Improved Enzymatic Procedure for a Preparative-Scale Synthesis of Sialic Acid and KDN
Authors: Sugai Takeshi , Kuboki Atsuhito , Hiramatsu Shigeki , Okazaki Hanako , Ohta Hiromichi 
Published: July 2006

Abstract
Sialic acid (N-acetylneuraminic acid) and KDN (3-deoxy-β-d-glycero-d-galacto-2-nonulosonic acid) play important roles in a variety of intercellular events. Extensive studies have been reported on the use of sialic acid aldolase as a catalyst to form the C–C bond between N-acetyl-d-mannosamine derivatives and pyruvic acid to give sialic acid and its analogs. However, the reported protocols have a significant drawback in terms of the tedious separation of the desired product from a large excess of pyruvic acid. We report here on a clean solution to this problem that relies on the utilization of pyruvate decarboxylase for catalyzing the decomposition of pyruvic acid into acetaldehyde and carbon dioxide to facilitate product isolation. Concerning our investigation to enhance the activity of this enzyme, we emphasized two points. One was a sufficient supply of cofactors for pyruvate decarboxylase; the other was an improvement of the enzyme reactor. As a result, the activity became nearly four-times as high as that previously reported. The combination of two enzymatic reactions worked well, affording sialic acid and KDN in 60% yield from N-acetyl-d-mannosamine and d-mannose, respectively. In addition, an efficient method for preparing N-acetyl-d-mannosamine by the epimerization of N-acetyl-d-glucosamine was established. Calcium hydroxide was found to be most effective for base-catalyzed epimerization.
Alkenyl- and Alkynyl-Substituted (p-Phenylene)bisiodonium Ditriflates by Reactions of a (p-Phenylene)bisiodine(III) Reagent with Alkynes and 1-Trimethylsilyl-1-alkynes
Authors: Kitamura Tsugio , Furuki Ryuji , Zheng Lei , Nagata Kensuke , Fukuoka Takahiro , Fujiwara Yuzo , Taniguchi Hiroshi 
Published: July 2006

Abstract
A (p-phenylene)bisiodine(III) reagent prepared from iodosylbenzene and trifluoromethanesulfonic acid or the anhydride showed a high reactivity to alkynes. The reaction of alkynes proceeded with stereoselective addition to the carbon–carbon triple bond to give trans-alkenyl(p-phenylene)bisiodonium ditriflates, whereas the reaction of 1-trimethylsilyl-1-alkynes afforded alkynyl(p-phenylene)bisiodonium ditriflates. These reactions indicate that the (p-phenylene)bisiodine(III) reagent is accessible for a (p-phenylene)bisiodine(III) transfer agent.
Electrochemical Impedance Study and Characteristics of Polyaniline Film Electrodes
Authors: Komura Teruhisa , Sakabayashi Hironobu , Takahashi Koshin 
Published: July 2006

Abstract
The ac response of polyaniline (PA) film electrodes in 0.5 M H2SO4 was investigated at different applied potentials and film thicknesses. The results of impedance analysis on the basis of the Randles equivalent circuit indicated that the electron exchange between metal and redox sites of the polymer controlled the rate of the charge transfer process at the film electrode. The oxidation of the PA film brought about a decrease in charge transfer resistance at lower potentials than the first half-wave potential of PA. The redox capacitance of the polymer indicated the dependence on the potential and film thickness, which was expected from a finite diffusion model. A large capacitance of the order of 3—30 mF cm−2 in the partially oxidized state is explained in terms of the charge saturation effect associated with the finite thickness. Impedance plots at high frequencies (the kHz range) suggested the occurrence of a hydrogen adsorption reaction in the reduced state. The PA film probably swells with the electrolyte. A counter ion to maintain the electroneutrality of the polymer can go into and out of the film with negligible resistance.