bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Lithium Salts in Solvents with Low Dielectric Constant by Means of Ultrasonic Velocity and Absorption
Authors: Nishikawa Sadakatsu , Morinaga Shirou , Yoshio Masaki 
Published: August 2006

Abstract
Ultrasonic velocity at 1.92 MHz has been measured precisely in 1,2-dimethoxyethane (DME), acetonitrile (AN), and propylene carbonate (PC) solutions of lithium tetrafluoroborate (LiBF4) and in DME solution of lithium hexafluoroarsenate (LiAsF6) at 25 °C. The molar relative sound velocity for the LiBF4 solution has been found to show a clear inflection in the DME solution at 0.01 mol dm−3 and in the AN one at 0.02 mol dm−3 concentration though such an inflection has not been found in PC solution. The inflection for DME solution of LiAsF6 is found near 0.0013 mol dm−3. These sound velocity inflection points are believed to be due to formation of triple ions or dimers (quadrupoles) in solvents of low dielectric constants.
Ultrasonic absorption coefficients in DME solutions of LiAsF6 and LiBF4 have been measured in the frequency range from 8.5 to 220 MHz by a pulse method as a function of their concentration. A single relaxational absorption has been observed in both solutions. In DME solution of LiBF4, the observed relaxational absorption mechanism has been attributed to the dimerization reaction, as reported by Maaser et al. (J. Phys. Chem., 88, 5100 (1984)). Our determination of the rate and thermodynamic constants, however, has taken into account the presence of triple ions.
The results in LiAsF6 solutions are compared to those reported by Farber et al. (J. Phys. Chem., 87, 3515 (1983)) in the concentration range higher than 0.1 mol dm−3. At concentrations lower than that, however, a phenomenon with a concentration dependent relaxation frequency has been found. From a consideration of various reaction models, it has been concluded that the relaxation is associated with formation of triple ions in solution. The rate and thermodynamic parameters have been determined from the concentration dependence of the relaxation frequency and the maximum absorption per wavelength.
Ab initio Density Functional Calculations on Copper(I)–CO2 Coordinations
Authors: Masuda Hideki , Fukushima Nobuhiro , Einaga Hisahiko 
Published: August 2006

Abstract
Full geometry optimizations have been carried out for the complex formations of Cu+ and Cu(2,2′-bipyridine)+ with CO2 by using the density functional methods. The calculation demonstrated that the end-on coordination mode was mainly favored for all cases, while the binding of 2,2′-bipyridine (bpy) to Cu(CO2)+ largely labilized the end-on coordination mode and stabilized the in-plane side-on coordination mode. The detailed examination of the population analysis indicate that the coordination of bpy to Cu+ weakens the electron donating character of CO2 to Cu+ and promotes the important participation of π-back-donative interaction from the metal ion to CO2.
Application of Density Functional Calculations to the Structures and Formation Energies of [MCl4]2− Complexes (M = Cr, Mn, Fe, Co, Ni, Zn)
Authors: Waizumi Kenji , Masuda Hideki , Einaga Hisahiko , Fukushima Nobuhiro 
Published: August 2006

Abstract
The structures and the formation energies of [MCl4]2− (M = Cr, Mn, Fe, Co, Ni, Zn) have been examined by the density functional method. The optimized structures of [MnCl4]2−, [CoCl4]2− and [ZnCl4]2− are a regular tetrahedron with the M–Cl distances of 236, 227, and 231 pm, respectively. The structures of [CrCl4]2− and [FeCl4]2− are a flattened tetrahedron with the M–Cl distances of 236 and 231 pm, respectively, and with the flattening angles of 156 and 112°, respectively, while that of [NiCl4]2− is a tetrahedron elongated along an S4 axis with the Ni–Cl distance of 226 pm and the corresponding angle of 97°. The formation energies of [MCl4]2− have been compared with their experimental data, and the relative energies of the transformation from [M(H2O)6]2+ to [MCl4]2− are also evaluated in connection with the stability of the anions in aqueous solutions.
Preparation and Molecular Structures of [Co(S2O-S,S′)(Me2PCH2CH2PMe2)2]ClO4 and [Co(S2PMe2)2(Me2PCH2CH2PMe2)]BF4
Authors: Kita Masakazu , Kashiwabara Kazuo , Fujita Junnosuke , Kurachi Saeko , Ohba Shigeru 
Published: August 2006

Abstract
The reaction of elemental sulfur S8 with [Co(dmpe)2](BF4)2 in a mixture of methanol and benzene gave a novel S,S′-coordinated disulfur oxide cobalt(III) complex, [Co(S2O-S,S′)(dmpe)2]ClO4 (1), and a dimethyldithiophosphinato complex, [Co(S2PMe2)2(dmpe)]BF4 (2). The molecular structures of these complexes were determined by X-ray structure analyses. Crystal data for complex 1: monoclinic, P21/n, a = 14.702(3), b = 11.645(1), c = 14.333(2) Å, β = 109.90(2)°, V = 2307.4(2) Å3, Dx = 1.55, Dm = 1.54(3) g cm−3, Z = 4, R = 0.039 for 4542 reflections. Crystal data for complex 2: orthorhombic, Pnc2, a = 13.383(3), b = 12.333(2), c = 13.742(3) Å, V = 2268.1(8) Å3, Dx = 1.60, Dm = 1.59(2) g cm−3, Z = 4, R = 0.075 for 2060 reflections. The central sulfur atom of the S–S–O group in complex 1 exerts a larger trans influence than does the terminal sulfur.
Enantiospecificity of α-Chymotrypsin at S′1 Site for Peptide Synthesis in Aqueous–Organic Media
Authors: Kise Hideo , Nagashima Tohru 
Published: August 2006

Abstract
The enantiospecificity of α-chymotrypsin (CT) at S′1 site in aqueous–organic media was investigated for peptide synthesis from N-acetyl-l-tyrosine ethyl ester (ATEE) as an acyl donor and alanine or serine derivatives as acyl acceptors. It was found that catalytic activity of CT is a function of nature of organic solvent, and, among the solvents used, CT exhibited high activity in t-butyl alcohol, acetone, and acetonitrile. The relative reactivity of l-alaninamide as an acyl acceptor to that of d-isomer was also significantly dependent on nature of solvent. CT exhibited high specificity to l-isomer in these three organic solvents. The enantiospecificity is also a function of water content in reaction media. In acetonitrile, the maximum reaction rates of ATEE with l- and d-alaninamide were obtained at 10 and 6% water, respectively, and relative reactivity of d-isomer increased with decrease in water content. Structural effects of acyl acceptors on their reactivity are striking and discussed in terms of stability of their complexes with the acyl-enzyme intermediate.
Pyrene-Sensitized Photolysis of N-(1-Naphthylsulfonyl)-N-phenyl-O-(p-toluoyl)hydroxylamine
Authors: Sakurai Tadamitsu , Okamoto Mitsuko , Inoue Hiroyasu 
Published: August 2006

Abstract
The title hydroxylamine (SO2NT) underwent singlet-sensitized photolysis in the presence of pyrene to give rearrangement and fragmentation products. SO2NT was found to quench both pyrene-monomer and -excimer fluorescences. The presence of a sulfonyl group with a semipolar-bond character in SO2NT was suggested to be responsible for a pronounced termolecular interaction between the pyrene excimer and SO2NT to result in a quenching of the excimer emission. An energetic consideration of the pyrene monomer and excimer as well as the N–O bond cleavage of SO2NT allows us to propose that not the excimer, but the monomer, activates SO2NT to induce its sensitized decomposition. An analysis of the solvent polarity effects on both limiting the quantum yields for the appearance of the products and the quenching of pyrene fluorescence by SO2NT demonstrated that the sensitized reaction proceeds by a singlet-exciplex mechanism in benzene, whereas an electron-transfer mechanism predominates in acetonitrile.
A Novel Synthesis of Naphthazarin and Juglone Derivatives by Reaction of Naphthazarin and Juglone with Cyclic Enol Ethers
Authors: Tanoue Yasuhiro , Terada Akira , Taniguchi Hiroshige , Okuma Tadashi , Kaai Hiroshi , Anan Mihoko , Kakara Yasuyuki , Doi Mika , Morishita Shin-ichi 
Published: August 2006

Abstract
The reaction of naphthazarin with cyclic enol ethers in acetic acid in the presence of BF3·OEt2 gave naphthazarin derivatives such as cycloshikonin, having a cyclic ether substituent, in one step. Cyclic enol ethers did not attack the quinone ring of naphthazarin but the benzene ring, and the corresponding naphthazarin derivatives were produced after tautomerization. This reaction was applicable to juglone to give juglone derivatives bearing a cyclic ether substituent.
Magnetic Properties of CT Complexes between 2,2″,5,5″-Tetrakis(dimethylamino)terphenyls and TCNQF4
Authors: Nakamura Yosuke , Iwamura Hiizu 
Published: August 2006

Abstract
2,2″,5,5″-Tetrakis(dimethylamino)-p- and m-terphenyls (1 and 2), in which two N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) moieties are linked through p- and m-phenylene units, respectively, were synthesized, and their CT complexes with TCNQF4 were prepared. In the complexes, 1 and 2 possess two S = 1/2 spins per molecule. The intramolecular interaction between the spins of the two TMPD moieties was found to be antiferromagnetic (2J/k = −42 K) in 1, and ferromagnetic (2J/k = 240 K) in 2.
The Catalytic Friedel–Crafts Acylation Reaction Starting from Aromatic Compounds and Free Carboxylic Acids (or Their Trimethylsilyl Esters) by Promotion of Silicon(IV) Cationic Species via Mixed Anhydrides
Authors: Suzuki Kaoru , Kitagawa Hideo , Mukaiyama Teruaki 
Published: August 2006

Abstract
In the presence of active cationic species generated from silicon(IV) chloride and silver perchlorate, carboxylic acids or their trimethylsilyl esters react with p-trifluoromethylbenzoic anhydride to form corresponding mixed anhydrides in situ. Then the catalytic Friedel–Crafts acylation reaction between initially formed mixed anhydrides and coexisted aromatic compounds smoothly proceeds at room temperature to afford the corresponding aromatic ketones in high yields. The above two sequential reactions are effectively promoted by the active silicon(IV) catalyst under mild conditions.
Syntheses and Cycloadditions of Ethyl 2-(Benzylidene)hydrazino-1-azaazulene-3-carboxylates with Dimethyl Acetylenedicarboxylate
Authors: Abe Noritaka , Kakehi Akikazu 
Published: August 2006

Abstract
Syntheses and cycloadditions of ethyl 2-(benzylidene)hydrazino-1-azaazulene-3-carboxylates were investigated. Condensations of ethyl 2-hydrazino-1-azaazulene-3-carboxylate with benzaldehyde and p-methoxybenzaldehyde gave corresponding hydrazones in good yields. Reactions of ethyl 2-(benzylidene)hydrazino-1-azaazulene-3-carboxylate (2a) and ethyl 2-(p-methoxybenzylidene)hydrazino-1-azaazulene-3-carboxylate with dimethyl acetylenedicarboxylate gave novel 1 : 2-adducts, 4a,11,11a-triazaindeno[5,6-a]azulene derivatives and 2-methoxycarbonylimino-1-(2-pyrrolylmethyl)-1-azaazulene derivatives as major products. Reaction of 2a with electron deficient olefins (tetracyanoethylene, N-methylmaleimide) gave no cycloadduct but a cyclization product of 2a, 3-phenyl-1,2,3a-triazacyclopent[a]azulene-9-carboxylate. The structures of the obtained compounds were analyzed by inspections of their physical and spectral data, and by single-crystal X-ray analyses of some of these compounds. The reaction mechanisms of these reactions are discussed.
Synthesis of 5- and 7-(Dicyanomethylene)-2,3-dihydrocyclohepta-1,4-dithiins, “Push-Pull” Heptafulvene Derivatives. 8,8-Dicyanoheptafulvenes from α-Bromomalononitrile and Cycloheptatrienylium Salt
Authors: Mori Akira , Kubo Kanji , Takeshita Hitoshi 
Published: August 2006

Abstract
Treatment of 2,3-dihydro-4aH-cyclohepta-1,4-dithiin with triphenylmethyl tetrafluoroborate followed by condensation with α-bromomalononitrile in pyridine afforded 5- and 7-(dicyanomethylene)-2,3-dihydrocyclohepta-1,4-dithiins in good yields. When changing the solvent to acetonitrile, the products obtained were 5- and 6-(2,2-dicyanoethyl)-2,3-dihydro-1,4-benzodithiins. This new method was applicable to the general synthesis of dicyanoheptafulvenes from tropylium salts.
Palladium and Copper-Catalyzed Carboxylation of Alkanes with Carbon Monoxide. Remarkable Effect of the Mixed Metal Salts
Authors: Nakata Kazuyuki , Miyata Tsutomu , Jintoku Tetsuro , Kitani Akira , Taniguchi Yuki , Takaki Ken , Fujiwara Yuzo 
Published: August 2006

Abstract
The mixed catalyst Pd(OAc)2–Cu(OAc)2 promotes the carboxylation of cyclohexane and propane with CO in higher yield than either a Pd(II) or Cu(II) catalyst alone. The mixed catalyst has the highest activity when the ratio of Cu(II)/Pd(II) is more than unity. The carboxylations of p-xylene with Pd(II)–Cu(II) and Pd(II) afford 2,5-dimethylbenzoic acid, but no carboxylic acid is detected in the reaction with Cu(II), giving rise to p-xylene dimer as the major product instead. Clear isotope effect (3.0—3.2) is observed in the reactions of cyclohexane with Pd(II)–Cu(II) and Pd(II), unlike the reaction with Cu(II) (1.0).
Diamide Derivatives of α-Amino Acids with a Quinolyl Group as Cu(II) Ionophores
Authors: Kasuga Kazuyuki , Hirose Takuji , Takahashi Toshikazu , Hiratani Kazuhisa 
Published: August 2006

Abstract
Several new N-(8-quinolyl)-substituted diamide compounds were synthesized from α-amino acids and their Cu(II) transport abilities as carriers through liquid membranes were investigated. The Cu(II) transport ability of the carrier is affected by the α-substituent of the amino acid. Diamides derived from alanine and phenylalanine have good Cu(II) transport abilities.
Synthesis and Intramolecular Charge Separation of Fixed-Distance Triads Consisting of Zinc Porphyrin, Metal-Free Porphyrin, and Electron-Accepting Diimide Moiety
Authors: Osuka Atsuhiro , Zhang Run-Ping , Maruyama Kazuhiro , Ohno Takeshi , Nozaki Koichi 
Published: August 2006

Abstract
Synthesis of fixed-distance triads consisting of zinc porphyrin (ZnP), metal-free porphyrin (H2P), and pyromellitimide (PIm) or 1,4 : 5,8-naphthalenetetracarboximide (NIm) is described. The ZnP and H2P moieties are bridged by aromatic spacers such as 1,4-phenylene, 4,4′-biphenylylene, methylenebis(1,4-phenylene), and bicyclo[2.2.2]octane-1,4-diylbis(1,4-phenylene) groups. The steady-state fluorescence spectra indicated the occurrence of intramolecular singlet-singlet energy transfer form the ZnP to the H2P. Formation of long-lived charge-separated states (ZnP)+–H2P–(PIm)− and (ZnP)+–H2P–(NIm)− with lifetimes of 0.14—80 μs in THF was observed by nanosecond to microsecond transient absorption spectroscopy. The lifetimes of the (ZnP)+–H2P–(Im)− states depend on the distances between the charged sites as well as the energy gaps between the ion pair and the ground state.
Regioselective Hydroalumination of Allenes and Their Synthetic Application
Authors: Nagahara Shigeru , Maruoka Keiji , Yamamoto Hisashi 
Published: August 2006

Abstract
The hydroalumination of a terminal allene, 1,2-nonadiene, with LiAlH4 in THF using [TiCl2(Cp)2], TiCl4, TiCl3, ZrCl4, and [ZrCl2(Cp)2] catalysts afforded a wide variety of deuterated species by quenching hydroalumination products with D2O, while PhB(OH)2-catalyzed hydroalumination with AlHCl2 in ether gave &gt;95% pure 1-nonene-3-d as predominant product (92%) in high yield. The allylation of benzaldehyde using the PhB(OH)2-catalyzed hydroalumination product suggested that the resulting hydroalumination product may be the allylaluminum compound, 2-nonenylaluminum dichloride. Allylation of trans-cinnamaldehyde using this allylaluminum compound proceeded with high regioselectivity, leaving the ketone functionality intact. Allylative ring-opening reaction of epoxides was less regioselective. The combination of catalytic PhB(OH)2 with AlHCl2 also was effective for the regioselective hydroalumination of the disubstituted allenes, vinylidenecyclohexane and 1-trimethylsilyl-1,2-nonadiene, although the trisubstituted allene, 1-butenylidenecyclohexane, showed nonregioselective orientation results.
Syntheses and Structures of Dinuclear Palladium(II) and Platinum(II) Complexes with (2S,3S)-2,3-Diaminobicyclo[2.2.1]heptane
Authors: Hatano Keiichiro , Saito Reiko 
Published: August 2006

Abstract
Dinuclear complexes bridged by optically active diamines, [Pd2Cl2(SS-nbn)3]Cl2·4H2O (1) and [Pt2(en)2(SS-nbn)2]Cl4 (2) (SS–nbn = (2S,3S)–2,3–diaminobicyclo[2.2.1]heptane, en = ethylenediamine) were prepared and characterized by X-ray crystallography for 1. Pd(II) centers are square-planarly coordinated by Cl and three N of three bridging SS-nbn. Molecule 2 has been suggested to have two μ-SS-nbn and two chelating en.
Cis-Selective Iodinative Etherification of N-Alkenyl-N-(2-hydroxyalkyl)anilines
Authors: Nishiyama Tomihiro , Kitano Kouji , Kishi Hiroshi , Yamada Fukiko 
Published: August 2006

Abstract
Several 6-alkyl- or 6-aryl-2-(iodomethyl)morpholines were prepared in good yields with regio- and cis-selectivity from N-alkenyl-N-(2-hydroxyalkyl)anilines by electrophilic iodinative etherification.
Stereoselective Synthesis of Dimethoxy[n.2]metacyclophanes
Authors: Okada Yukihiro , Ishii Fuyuhiko , Nishimura Jun 
Published: August 2006

Abstract
Dimethoxy[n.2]metacyclophanes were obtained in 5—45% yields through [2+2] photocycloaddition of corresponding styrene derivatives. These cyclobutane-fused metacyclophanes were assigned to be of only syn conformation (n = 6, 8, 10, and 12). The cyclobutane ring exclusively took the opposite direction to the alkyl bridged chain.
X-Ray Analysis of a Captodative Diphosphene, 1-(N-Mesityl-9-fluorenylamino)-2-[2,4,6-tris(trifluoromethyl)phenyl]diphosphene
Authors: Yoshifuji Masaaki , Abe Masatoshi , Toyota Kozo , Miyahara Ikuko , Hirotsu Ken 
Published: August 2006

Abstract
The N-mesityl-9-fluorenylamino group was utilized as an electron-donating new sterically protecting group for stabilizing low coordinate organophosphorus compounds. A push–pull substituent effect on the P–P double bond was demonstrated by the X-ray analysis of a captodative diphosphene, 1-(N-mesityl-9-fluorenylamino)-2-[2,4,6-tris(trifluoromethyl)phenyl]diphosphene.
Purification and Crystallization of the Reaction Center from the Thermophilic Purple Sulfur Bacterium Chromatium tepidum
Authors: Kobayashi Masayuki , Nozawa Tsunenori 
Published: August 2006

Abstract
The reaction center of Chromatium tepidum was crystallized by the vapor diffusion method using octyl β-d-glucoside and polyethylene glycol-4000 (PEG) as a detergent and a precipitant, respectively. Good crystals were obtained at reservoir PEG concentrations between 20—27.5% for a PEG concentration in protein solution of 8%.
Determination of substituent distribution of viscoses by GPC
Authors: Rußler Axel , Potthast Antje , Rosenau Thomas , Lange Thomas , Saake Bodo , Sixta Herbert , Kosma Paul 
Published: August 2006

Abstract
Based on previous investigations on the substitution pattern of stabilized and fresh viscose, different viscoses were analyzed by gel permeation chromatography (GPC) with multiple-angle laser light scattering, refractive index (RI), and UV detection. Viscoses derivatized with N-methyl-N-phenyl-iodoacetanilide are stable over a long time and largely improve handling for analytical purposes. In addition, the derivatized xanthogenate groups exhibit UV absorbance that can be used to detect their distribution along the polymer molecule, once the polymer is dissolved. UV assay indicated that in technical viscoses the distribution of substituents is uniform. Enzymatic degradation with endoglucanases was followed by analysis of the degradation pattern by GPC. Even though the degree of substitution (DS) of xanthogenate groups ranged from γ=0.4 to 0.6, endoglucanases were able to slightly degrade the viscose. Ultrasonic degradation resulted in a narrow molecular weight distribution (MWD), notably without cleavage of substituents, and was also used to improve the solubility of the stabilized viscoses for further analysis. The techniques applied provide more insight into the xanthogenate distribution along the MWD. Remarkable differences in the degradation behavior of both viscose samples were observed.
Influence of amide content on the crystal structure of chitin
Authors: Tamura Hiroshi , Sawada Makoto , Nagahama Hideaki , Higuchi Taiichi , Tokura Seiichi 
Published: August 2006

Abstract
The crystalline structure of chitin and chitosan was investigated by X-ray diffraction (XRD). Chitosan filaments were prepared using a saturated solution of calcium chloride dihydrate in methanol (CaCl2-MeOH) as a mild solvent and the study focused on the interaction between the degree of acetylation (DA) and crystallinity. There were pronounced differences in the XRD patterns for specimens with DA values between 44.2% and 52.2%. We suggest that the crystalline structure changes from an anhydrous-type chitosan to an α-chitin type without any additives. CaCl2-MeOH is a good solvent for chitin and a poor solvent for chitosan and we found that it can regulate the distribution of N-acetyl glucosamine and glucosamine between amorphous and crystalline regions.
Measurement of the shear modulus of wood by the square-plate twist method
Authors: Yoshihara Hiroshi , Sawamura Yuya 
Published: August 2006

Abstract
In this research, square-plate twist test methods for obtaining the shear modulus of wood were examined. Square plates of western hemlock (Tsuga heterophylla Sarg.) were used as specimens. Twist tests were conducted according to three different methods for various length/thickness and span/plate diagonal ratios, and the shear modulus corresponding to each test condition was obtained. To examine the validity of shear modulus obtained by these tests, asymmetric four-point bending tests and finite element calculations were independently conducted and the results were compared. Specimens had a length/thickness ratio greater than 47 and were supported at two or three points close to each corner while applying a load to the remaining corner. Under these conditions, the shear modulus could be properly obtained over a wide range of span/plate diagonal ratios.
Dielectric relaxation of water adsorbed on chemically treated woods
Authors: Sugiyama Masaki , Norimoto Misato 
Published: August 2006

Abstract
Changes in the dielectric relaxation due to water adsorbed on eight types of chemically treated woods, as well as untreated wood (Picea sitchensis Carr.), with moisture content (MC) were investigated in the temperature range between −150°C and 20°C and in the frequency range between 100 Hz and 1 MHz. Cole-Cole's circular arc law was applied to the results of dielectric measurements conducted at seven levels of relative humidity (RH), and the relaxation spectra at −75°C were calculated. The theory of rate processes was applied to the dielectric relaxation resulting from the motions of water molecules adsorbed on the untreated and chemically treated woods, and the binding state of adsorbed water was examined. The relaxation magnitude increased with increasing MC, irrespective of the chemical treatment. The distribution of relaxation times decreased in the MC range below 1%, but increased with increasing MC at higher levels. The generalized relaxation time increased up to 5% MC, then decreased. The enthalpy-entropy compensation phenomenon was observed in the dielectric relaxation, which was derived from the adsorption of water molecules on the chemically treated woods. The binding states of adsorbed water and ice were similar. The water molecules adsorbed on wood may have produced a very wide variety of cohesive structures in the chemically treated woods.