bluuebunny/crossref_metadata_2025_split huggingface dataset:
An NMR Study on the Ruthenium Complex-Catalyzed C-H/Olefin Coupling Reaction
Authors: Hiraki Katsuma , Ishimoto Takayuki , Kawano Hiroyuki 
Published: September 2002

Abstract
A dihydridoruthenium(II) complex, [RuH2(CO)(PPh3)3], reacts with styrene to give two species: a bis(styrene)ruthenium(0) complex, [Ru(CO)(CH2=CHPh)2(PPh3)2], and a cyclometallated hydridoruthenium(II) one, [Ru(C6H4PPh2)H(CO)(PPh3)2]. The complex [RuH2(CO)(PPh3)3] reacts with isoprene to give a piano-stool type ruthenium(0) complex [Ru(η4-CH2=CMeCH=CH2)(CO)(PPh3)2]. In reactions among [RuH2(CO)(PPh3)3], styrene, and 3′-(trifluoromethyl)acetophenone, three cyclometallated hydridoruthenium(II) complexes: P,P′-cis-C,H-cis-, P,P′-trans-C,H-trans-, and P,P′-trans-C,H-cis-[Ru{C6H3(CF3)C(=O)Me}H(CO)(PPh3)2] are detected by NMR spectroscopy. The 1H NMR spectra of the reaction mixture exhibit the catalytic formation of 2′-(2-phenylethyl)- and 2′-(1-phenylethyl)-5′-(trifluoromethyl)acetophenones. On the basis of these findings, a mechanism for the C-H/olefin coupling reaction is discussed. The first of the three complexes is assigned to an active intermediate in the catalytic coupling reaction, whereas the other two are assigned as quasi-stable ruthenium(II) complexes which are in equilibrium with active species.
Synthesis, Structure, and Properties of Hexaaryl[3]radialenes
Authors: Enomoto Tetsuya , Nishigaki Naoki , Kurata Hiroyuki , Kawase Takeshi , Oda Masaji 
Published: September 2002

Abstract
A number of hexaphenyl[3]radialene derivatives were synthesized in modest to good yields by the reaction of tetrachlorocyclopropene with diarylmethyl anion followed by oxidation with oxygen. That the acidity of diarylmethane is higher than that of diphenylmethane is found to be an important factor for the successful synthesis. Lithiation and protonation of hexa(4-iodophenyl)[3]radialene thus obtained leads to the first synthesis of hexaphenyl[3]radialene. These hexaaryl[3]radialenes are stable, orange to red, crystalline substances. An X-ray crystallographic analysis of hexa(4-cyanophenyl)[3]radialene reveals a double three-bladed propeller conformation. The effects of substituents in the phenyl groups on their properties are most clearly seen in their electrochemical reduction potentials; among hexaphenyl[3]radialenes here obtained, hexa (4-nitrophenyl)[3]radialene (1Ered = -0.30 V, 2Ered = -0.45 V) is found to be a good electron acceptor stronger than p-benzoquinone.
The Juliá-Colonna Asymmetric Epoxidation Reaction of Chalcone Catalyzed by Length Defined Oligo-L-leucine: Importance of the N-Terminal Functional Group and Helical Structure of the Catalyst in the Asymmetric Induction
Authors: Takagi Ryukichi , Manabe Toshiki , Shiraki Akiko , Yoneshige Arata , Hiraga Yoshikazu , Kojima Satoshi , Ohkata Katsuo 
Published: September 2002

Abstract
Catalysts, oligo-L-leucine, for the Juliá-Colonna asymmetric epoxidation of chalcone with defined degrees of polymerization were prepared by a stepwise elongation method. The yield and enantioselectivity in the epoxidation increased with the degree of polymerization of the catalyst. The presence of an unprotected amine moiety at the N-terminus proved to be essential for high asymmetric induction. The IR characteristic absorption bands (the amide I region) of the catalysts suggested that helical structure in the catalyst is related to asymmetric induction.
Lattice Inclusion Complexation in Water. Hydrogen Bonding in Selective Guest Binding and Catalysis
Authors: Dewa Takehisa , Saiki Toshiyuki , Imai Yuki , Endo Ken , Aoyama Yasuhiro 
Published: September 2002

Abstract
When immersed in an aqueous solution of alcohol or alkyl acetate as a guest, 9,10-bis(3,5-dihydroxyphenyl)anthracene 1 as a hydrogen-bonded solid host incorporates two mols of the guest together with 5—8 mols of water. The binding isotherm shows a sharp threshold guest concentration characteristic of guest-induced phase-transition. The threshold concentrations as a measure of affinities are highly dependent on the hydrophobicities of the guests. Host 1 also catalyzes the Diels-Alder reaction of acrylaldehyde and 1,3-cyclohexadiene in an aqueous environment. The preserved 1 : 2 (host-to-guest) stoichiometry, spectroscopic evidence (ΔνC=O), guest-desorption behaviors, and X-ray powder-diffraction studies indicate that host-guest hydrogen-bonding in collaboration with apolar interactions is responsible for the selective guest-binding and catalysis under the present aqueous conditions.
Synthesis and Reduction of Silyl-Substituted [5]Radialene. Characterization and Structure of a [5]Radialene Tetraanion with a Ten-Center, Fourteen-Electron π-System
Authors: Matsuo Tsukasa , Fure Hidetoshi , Sekiguchi Akira 
Published: September 2002

Abstract
The reaction of 3,3,6,6,8,8,11,11,14,14,16,16,19,19,21,21-hexadecamethyl-3,6,8,11,14,16,19,21-octasilacyclohenicosa-1,4,9,12,17-pentayne with an excess molar amount of [Mn(CO)3(Me-Cp)] in tetrahydrofuran (THF) under photochemical and refluxing conditions produced 2,2,4,4,9,9,11,11,13,13,15,15,17,17,21,21-hexadecamehyl-2,4,9,11,13,15,17,21-octasilahexacyclo[10.5.3.15,8.06,18.07,20.014,19]henicosa-1(18),5,7,12(20),14(19)-pentaene (2) as silyl-substituted [5]radialene derivative. This was reacted with lithium metal in THF to give dark red crystals of the tetralithium salt (4) of 2. The molecular structure of tetraanion of 2 with a novel ten-center, fourteen-electron π-system was established by X-ray crystallography. The tetralithium salt 4 has a monomeric structure and forms contact ion pairs (tetrakis-CIPs) in the crystals. The structural parameters of 4 are discussed in comparison with those of the neutral starting molecule 2. The structure of 4 in solution is also discussed on the basis of NMR spectroscopic data.
Reaction of Trialkyl(dibromomethyl)silanes or 1,2-Bis(dibromomethyl)benzene with Triorganomanganates. A Facile and Selective Synthesis of Alkenylsilanes and 1,2-Diaryl-1,2-dihydrobenzocyclobutenes
Authors: Kakiya Hirotada , Shinokubo Hiroshi , Oshima Koichiro 
Published: September 2002

Abstract
Treatment of trialkyl(dibromomethyl)silanes with trialkylmanganates, derived from manganese(II) chloride and three molar amounts of Grignard reagents or alkyllithiums, provided (E)-1-trialkylsilyl-1-alkenes with high stereoselectivity in good yields. The reaction of trialkyl(dibromomethyl)silanes with alkylmagnesium halides proceeded in the presence of a catalytic amount of manganese(II) chloride. Treatment of 1,2-bis(dibromomethyl)benzene with triphenylmanganate gave 1,2-diphenyl-1,2-dihydrobenzocyclobutene.
Palladium(II)-Catalyzed Michael-Type Addition Reactions Using Aryltin Compounds
Authors: Ohe Toshiyuki , Wakita Takeshi , Motofusa Shin-ichi , Cho Chan Sik , Ohe Kouichi , Uemura Sakae 
Published: September 2002

Abstract
A variety of aryltin compounds can be employed for Michael-type hydroarylation reactions to α,β-unsaturated ketones and aldehydes in the presence of a catalytic amount of palladium(II) salt in acetic acid under air. Each reaction is much accelerated in the presence of a soluble metal chloride such as LiCl, MgCl2, and CaCl2. It is found that slightly fewer than four aryl groups of tetraaryltins can be transferred to the products in this arylation.
Synthesis of Ladder and Cage Silsesquioxanes from 1,2,3,4-Tetrahydroxycyclotetrasiloxane
Authors: Unno Masafumi , Suto Akiko , Takada Keisuke , Matsumoto Hideyuki 
Published: September 2002

Abstract
The versatility of cis,cis,cis-1,3,5,7-tetrahydroxy-1,3,5,7-tetraisopropylcyclotetrasiloxane (1) as a precursor of cage and ladder siloxanes is presented. Compound 1 reacted with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane in pyridine to give 1,3,5,5,7,7,9,11,13,13,15,15-cis-cisoid-cis-dodecaisopropyltricyclo[9.5.1.13,9]octasiloxane (2) in 20% yield. The reaction proceeded with retention of the configuration of the silicon atoms, and only syn-type isomer was obtained. The reaction of 1 with 1,1,3,3-tetrachloro-1,3-diisopropyldisiloxane in pyridine produced hexakis(isopropylsilsesquioxane) (T6) (3) in 25% yield. Treatment of 1 with dicyclohexylcarbodiimide (DCC) as dehydrating reagent led to the formation of octakis(isopropylsilsesquioxane) (T8) (4) in 45% yield. The crystal structures of 2, 3, and 4 are reported.
Separation of Orientational Disorder in the X-Ray Analysis of the Kinetically Stabilized 2-Silanaphthalene
Authors: Wakita Keiji , Tokitoh Norihiro , Okazaki Renji 
Published: September 2002

Abstract
The crystal structure of the stable 2-silanaphthalene was refined more adequately by the separation of the disorder of overlapped two 2-silanaphthalene moieties. The bond lengths of the 2-silanaphthalene ring were in fairly good agreement with the theoretically calculated values which we previously reported.
Trialkylmanganate Mediated Radical Addition of Triphenylgermane to Carbon-Carbon Multiple Bonds
Authors: Kinoshita Hidenori , Kakiya Hirotada , Oshima Koichiro 
Published: September 2002

Abstract
Treatment of 1-dodecyne with triphenylgermane in the presence of catalytic amounts of tributylmanganate at 25 °C provided 1-triphenylgermyl-1-dodecene in good yield. The reaction proceeded in a radical pathway and treatment of diene afforded the corresponding radical cyclization product.
A Universal Structural Model for Human Hair to Understand the Physical Properties 1
Authors: Nagase Shinobu , Ohshika Masato , Ueda Shinya , Satoh Naoki , Tsujii Kaoru 
Published: September 2002

Abstract
A universal structural model for human hair has been proposed in order to understand the physical properties of hair. The model consists of two structural parts, both of which have two states (Two-part/two-state model). The transition temperature (Tc) between the two states of one part is about 70 °C, and that of the other part is about 0 °C in a water medium. These transition temperatures depend highly upon the water content of the hair. A higher transition temperature is observed in hair having a lower water content. Above the transition temperatures, both parts of the hair are soft and plastic (a melted state); they are hard and elastic (a solid state) below the transition points. One part of hair which has a higher transition temperature (ca. 70 °C in water) is assigned to be macrofibril and exo-cuticle consisting of keratinous proteins; the other part with a lower Tc (ca. 0 °C) is inter-macrofibrillar materials, a cell-membrane complex (CMC), and the endo-cuticle of non-keratinous proteins and lipids. This structural model was derived from the results of thermal-setting and relaxation experiments as well as TEM observations after permeating a dye with a high electron density (Erythrosin B).
A Universal Structural Model for Human Hair to Understand the Physical Properties 2. Mechanical and Permeation Behaviors
Authors: Sakai Masahiko , Nagase Shinobu , Okada Tomoyuki , Satoh Naoki , Tsujii Kaoru 
Published: September 2002

Abstract
The mechanical properties of human hair fiber and the permeation behaviors of some dye molecules into hair have been studied, and are here discussed based on a universal structural model proposed by the authors in the previous paper. The model consists of two structural parts, both of which have two states (Two-part/two-state model). One part of the hair, which has a higher transition temperature (Tc; ca. 70 °C in water), is assigned to be macrofibril and exo-cuticle; the other part with lower Tc (ca. 0 °C in water) is inter-macrofibrillar materials, a cell-membrane complex (CMC) and endo-cuticle. The temperature dependence of the elastic modulus of a human hair in the Hookean region clearly shows two break points, indicating the above-mentioned transition temperatures. We have proposed a viscoelastic model based on the two-part/two-state structural model to understand the mechanical behaviors in the Hookean, yield and post-yield regions. The permeation rate of some dye molecules into hair fiber starts to dramatically increase at the higher transition temperature. Such permeation behaviors can also be understood from a universal structural model. The molecular size of dye is a crucial factor in permeation behaviors. Dye molecules with a size smaller than 1.0 nm migrate much more easily into hair.
X-Ray Crystallographic Study on Single-Crystalline Photochromism of 1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene
Authors: Yamada Taro , Kobatake Seiya , Irie Masahiro 
Published: September 2002

Abstract
Single-crystalline photochromism of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene was studied by X-ray crystallography. The crystal was irradiated with linearly polarized monochromatic 360 nm light and analyzed with an X-ray diffractometer. The X-Ray crystallographic analysis showed that the conversion from the open-ring to the closed-ring isomers was as much as 8% and that the reaction proceeded in a conrotatory mode. Two sulfur atoms and reactive carbon atoms in the thiophene rings clearly changed their positions. The photogenerated closed-ring isomers completely returned to the initial open-ring isomers in the crystal by irradiation with 650 nm light.
Hydrogen Abstraction Reactions from C2 Hydrocarbons
Authors: Kunioshi Nílson , Mouri Shigeru , Yamashita Noriyuki , Fukutani Seishiro 
Published: September 2002

Abstract
The sequence of hydrogen abstraction reactions from ethane to acetylene, which proceeds in fuel-rich methane flames, has been investigated by an ab initio molecular orbital method. First, the hydrogen abstraction mechanism was elucidated through an analysis of the variation in the electron spin density distributions through the reacting species. The H atoms holding the largest spin densities within a radical where seen to be those being abstracted from the species. The reaction rate coefficients for the four elementary abstraction steps from ethane to acetylene were determined through the transition state theory, and the results were compared with data published in the literature. The obtained rate coefficients were found to be lower than the published data for all four reactions examined. Especially, for two of the reactions, some published data seem to be too large, considering that the rate coefficients obtained through transition state theory tend to be larger than the true values.
Analysis of Water Oxidation Catalysis by Dinuclear Ruthenium Complex [(NH3)5Ru-O-Ru(NH3)5]4+ Incorporated in a Nafion® Membrane
Authors: Nagoshi Kentaro , Yagi Masayuki , Kaneko Masao 
Published: September 2002

Abstract
Catalytic activity of a dinuclear ammine ruthenium complex, [(NH3)5Ru-O-Ru(NH3)5]4+, for water oxidation to evolve O2 was investigated both in homogeneous aqueous solution and in heterogeneous Nafion® membrane systems using CeIV oxidant. It was suggested that the complex works as a four-electron water oxidation catalyst and that the water oxidation by the complex is in competition with a bimolecular decomposition between the complexes. The first-order rate constant (kO2 (s-1)) for O2 evolution and second-order rate constant (kdeact (M-1 s-1)) for bimolecular decomposition were obtained by a kinetic analysis. It was found that kdeact decreased by one order of magnitude by incorporating the complex in the membrane; this was ascribed to the suppression of the bimolecular decomposition. The critical decomposition distance (rd (nm)) between the catalysts was analyzed to be 1.06 nm based on an intermolecular distance distribution.
Photoinduced Electron-Transfer of Inclusion Complexes of Fullerenes (C60 and C70) in γ-Cyclodextrin
Authors: Masuhara Akito , Fujitsuka Mamoru , Ito Osamu 
Published: September 2002

Abstract
Photophysical and photochemical properties of 1:2 inclusion complexes of C60 and C70 in γ-cyclodextrin (γ-CD) have been studied by laser flash photolysis and steady photolysis methods. The triplet-triplet annihilations of C60/γ-CD and C70/γ-CD are retarded, compared with those of the pristine fullerenes. The rate constant for the fluorescence-quenching of C70/γ-CD by 1,4-diazabicyclo[2.2.2]octane was larger than that of C60/γ-CD, indicating incomplete hindrance by γ-CD due to larger size of C70 than C60. A similar trend was also observed in triplet-triplet annihilation processes of the encapsulated fullerenes. Generations of radical ions by photoinduced electron transfer between amines and 3C60*/γ-CD or 3C70*/γ-CD were confirmed by observing the transient absorption bands due to radical anions in the near-IR region. The electron transfer rates for 3C60*/γ-CD or 3C70*/γ-CD were slower than those of corresponding 3C60* or 3C70* in solution by ca. 1/100. For reversible systems in which the cation radicals of amines are stable (for example, p-anisidine), C60•-/γ-CD and C70•-/γ-CD decayed slowly by back electron transfer. For an irreversible system in which the cation radical of amine (nitrilotriethanol) is degraded, the high concentration of C60•-/γ-CD or C70•-/γ-CD was persistent. On addition of methylviologen (MV2+), persistent MV•+ was generated in high concentration as equilibrium with C60•-/γ-CD, suggesting that C60/γ-CD acts as an efficient photosensitizer and an electron mediator to produce MV•+ using nitrilotriethanol as a sacrificial donor.
Inclusion Complexes of Cyclodextrins with Methylene Blue and Acid Orange 7 in Aqueous Solutions
Authors: Hamai Sanyo , Satou Hideyuki 
Published: September 2002

Abstract
Upon the addition of Acid Orange 7 (AO7) to aqueous Methylene Blue (MB) solution buffered at pH 5.0, the absorption spectrum of MB is reduced in intensity, accompanied by a red shift of the absorption peak, indicating the formation of a complex between MB and AO7. From a simulation concerning the fluorescence intensity change of MB, the equilibrium constant for the formation of the 1 : 1 MB-AO7 complex has been estimated to be 66300 mol-1 dm3. γ-Cyclodextrin (γ-CD) forms a 1 : 2 and a 1 : 1 inclusion complex with MB and AO7, respectively. From the absorbance changes, equilibrium constants for the formation of the 1 : 2 γ-CD-MB and 1 : 1 γ-CD-AO7 inclusion complexes have been evaluated to be 2.95×107 mol-2 dm6 and 11000±300 mol-1 dm3, respectively. When γ-CD is added to MB solution containing AO7, the absorption band of MB is enhanced in intensity without an appearance of the MB dimer band, in contrast to MB solution without AO7. This finding indicates the formation of a ternary γ-CD-MB-AO7 inclusion complex. To determine the stoichiometry of the ternary inclusion complex, a continuous variation method using the absorption and fluorescence intensities has been performed under the conditions that the sum of the initial concentrations of γ-CD and AO7 has been kept constant. Both the results indicate the formation of a 2 : 1 : 1 γ-CD-MB-AO7 inclusion complex. The equilibrium constant for the formation of the ternary inclusion complex from γ-CD and the 1 : 1 MB-AO7 inclusion complex has been evaluated to be 3.40×1010 mol-2 dm6 from the fluorescence intensity change.
Characterization of the Light-Harvesting Polypeptide/Bacteriochlorophyll a Complex Isolated from Photosynthetic Bacteria by the Linear Dichroism Spectra
Authors: Iida Kouji , Ohya Nobuyasu , Kashiwada Ayumi , Mimuro Mamoru , Nango Mamoru 
Published: September 2002

Abstract
The linear dichroism (LD) spectra of the light-harvesting polypeptide (LH)/bacteriochlorophyll (BChl a) complex, isolated from photosynthetic bacteria, Rhodospirillum rubrum, were measured to provide insight into the pigment orientation in the LH/BChl a complex. The LD spectrum for the Qy band of BChl a in the complex in a squeezed polyacrylamide gel was positive, while that for the Qx band was negative, indicating that the dipole moment of the Qy band was membrane-parallel while that of the Qx band was membrane-perpendicular. The anisotropy ratio, the LD/A value for the Qy transition of BChl a in the complex, was 0.18 ± 0.02 at a 0.5 compression-ratio, consistent with that for the Qy band of a special pair of BChl a in the reaction center (RC) complex isolated from R. rubrum. This result implies that the orientation of the Qy band in the LH/BChl a complex is perpendicular for the transmembrane axis of the LH in the complex as well as that of the special pair of BChl a in the RC. Furthermore, the LD/A spectrum for the Qy band of BChl a in the LH/BChl a complex indicated that the Qy band was geometrically homogeneous in the direction to the transmembrane axis in the complex.
Photoreactions of 3-(2-Hydroxyphenyl)-1-(substituted phenyl)-2-propen-1-ones (Substituted 2-Hydroxychalcones) in Organic Solvents in the Presence and Absence of Acid
Authors: Matsushima Ryoka , Murakami Tadahiro 
Published: September 2002

Abstract
Absorption spectra and photochemical reactivities of a dozen 3-(2-hydroxyphenyl)-1-(substituted phenyl)-2-propen-1-ones (substituted 2-hydroxychalcones) have been investigated in organic solvents in the presence and absence of added acid. Upon UV irradiation in the presence of 5 mM perchloric acid, flavylium ions were formed in high quantum yields around 0.34, regardless of the nature of the substituents. Upon irradiation in neutral solution, on the other hand, amino-substituted chalcones gave photo-Z-isomers as thermostable products, while the majority of other chalcones gave cyclic hemiacetals (2-hydroxy-2-phenyl-2H-1-benzopyranes). The quantum yields for the photochemical E/Z isomerization in the neutral solution were comparable to those in the acid solution, except for the amino-substituted chalcones which revealed lower quantum yields. Remarkable hypsochromic shifts were observed for the absorption spectra of the amino-substituted chalcones upon addition of acid, reflecting protonation on the amino group.
Benzene-Ethene Interactions as Studied by ab initio Calculations
Authors: Oki Michinori , Takano Sho , Toyota Shinji 
Published: September 2002

Abstract
For a search for π-π* and/or CH-π interactions between benzene and ethene, ab initio calculations were carried out at HF/6-31G**, MP2/6-31G**, and B3LYP/6-31G** levels of theory. Thirteen configurations of benzene and ethene complexes were optimized by the energy gradient techniques, of which only two were real energy-minimum forms and the others were saddle points or conical points. The global minimum configuration is one in which one of the tilted ethene C-H groups interacts with the C-C π-bond of benzene (configuration F-1). A configuration, in which benzene and ethene planes are parallel, was not obtained as a minimum except for MP2 calculations. The intermolecular distances obtained by HF and B3LYP theories were longer than the sum of van der Waals radii, whereas those obtained by the MP2 method were close to the sum. Dipole moments were also obtained that suggest the existence of charge transfer interactions. It is concluded that the molecular interaction energy between benzene and ethene mainly consists of dispersion forces with minor contributions of CT interactions, while the configuration of the global minimum is determined by CH-π interactions. From the frequency analysis for the energy-minimum forms, the normal modes associated with the intermolecular CH-π interactions were obtained at low frequency regions.
Crystal Structure of an Ionic Charge-Transfer Complex of DAP-F4TCNQ (DAP = 1,6-Diaminopyrene, F4TCNQ = 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane)
Authors: Matsushima Koichi , Ogaki Megumi , Naito Toshio , Inabe Tamotsu 
Published: September 2002

Abstract
A charge-transfer complex of DAP with F4TCNQ has been obtained by electrochemical reduction of F4TCNQ in acetonitrile in the presence of DAP·BF4. The crystal comprises segregated one-dimensional columns of donors and acceptors with CH3CN as the crystal solvent. The molecular geometry and infrared spectrum show that the donor and acceptor components are completely ionized. These features are the same as those found in DAP·TCNQ. However, a marked difference lies in the column structure; both the DAP and F4TCNQ columns are composed of the dimerized units, while they are uniform in DAP·TCNQ. The difference can be accounted by the increase of the transfer energy in DAP·F4TCNQ·CH3CN compared with DAP·TCNQ.