bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Structures of the Room-Temperature Phase of 4,4″-Difluoro-p-terphenyl and 4,4″′-Difluoro-p-quaterphenyl
Authors: Saitoh Hideki , Saito Kazuya , Yamamura Yasuhisa , Matsuyama Haruo , Kikuchi Koichi , Iyoda Masahiko , Ikemoto Isao 
Published: August 2006

Abstract
4,4″-Difluoro-p-terphenyl and 4,4″′-difluoro-p-quaterphenyl were synthesized and their crystal structures were determined at room temperature. These are isostructural to p-terphenyl and p-quaterphenyl, respectively. Some “disorder” in the inner benzene ring orientation was detected and resolved by the split-atom method. A rigid-body librational analysis of each benzene ring around the long molecular axis was performed. A rough estimate of the barrier height of the planar conformation for 4,4″-difluoro-p-terphenyl was obtained as being about 1 kJ mol−1. The results are compared with the properties of p-terphenyl and p-quaterphenyl, and the effect of fluorine-substitution on the molecular properties is discussed in relation to the low-temperature phase transitions.
Electrochemical Insertion of Hydrogen into Diniobium Pentaoxide
Authors: Komura Teruhisa , Nakanori Takahiro , Takahashi Koshin 
Published: August 2006

Abstract
The electrical behavior of the Nb2O5 electrode in Na2SO4 solutions was characterized by the impedance spectra. The pH dependence of the flat band potential could be explained in terms of the acid-dissociating equilibrium of hydroxyl groups on the oxide surface. The plot of equilibrium potential of the oxide vs. pH gave a straight line with a slope of −0.06 V. The equilibrium potential became monotonously more negative with increasing extent of the reduction of the oxide. The cyclic voltammograms and chronopotentiograms of the partially reduced oxide indicated that the diffusion of an electroactive species in the oxide controlled the rate of the electrode process. These results suggest that HxNbO2.5 or NbO2.5−x(OH)x can be formed by the reduction of the oxide. The conductivities of the oxide increased about two orders of magnitude by the insertion of a small amount of hydrogen. In conclusion, a blue coloration of the oxide can occur as a result of the diffusion of H+ from the electrolyte into the Nb2O5 lattice and a simultaneous injection of electrons to d-block bands of Nb in the energy band model.
Band Assignments of the Infrared Spectrum of 1-Methyl-2(1H)-pyridinimine
Authors: Inuzuka Kozo , Fujimoto Akira , Ito Hiroshi 
Published: August 2006

Abstract
The band assignments of the IR spectrum of 1-methyl-2(1H)-pyridinimine in solution were carried out with the normal coordinate treatment by the ab initio 6-31G method. The IR spectrum of the compound is characterized by three prominent strong absorption bands in the 1700 to 1500 cm−1 region. These three bands are mainly attributed to the stretching modes of the C=C bonds of the ring and the C=N group. All another bands are relatively weak compared with the intensities of these bands. The normal coordinate treatment suggests that 1-methyl-2(1H)-pyridinimine has three out-of-plane fundamental bands in the frequency region lower than the lowest fundamental band of pyridine. The calculated lowest fundamental band is near 129 cm−1. It was assigned to the twisting mode of the CH3 group. The second and third lowest bands correspond to the twisting vibration of the CH3 group and the out-of-plane bending vibration of the ring framework. This suggests that the ring framework of 1-methyl-2(1H)-pyridinimine may be more flexible than that of pyridine. The vibrational features of the IR spectrum of 1-methyl-2(1H)-pyridinimine are similar to that of 1-methyl-2-pyridone. In the liquid state, 1-methyl-2(1H)-pyridinimine forms an inter-molecular hydrogen bond between the imino groups.
Crystal Structures and Molecular Conformations of Isoprenaline Hydrochloride and (S)-Isoprenaline Hydrogen (2R,3R)-Tartrate
Authors: Kingsford-Adaboh Robert , Hayashi Eiichi , Haisa Masao , Kashino Setsuo 
Published: August 2006

Abstract
The crystal structures of racemic form of isoprenaline hydrochloride (I) and (S)-isoprenaline hydrogen (2R,3R)-tartrate (II) were determined by X-ray diffraction method. Among the related compounds I has the least extended phenethylamine chain with a gauche–gauche conformation. The side chain of II has the usually observed perpendicular-trans conformation. The conformations observed for I and II are consistent with the intermolecular hydrogen bonding. The observed conformations are close to either a global or local minimum estimated by MMP2.
The Synthesis and X-Ray Crystal Structures of Bis(diethylenetriamine)rhodium(III), Bis(diethylenetriamine)iridium(III), and Bis[bis(3-aminopropyl)amine]rhodium(III) Complexes
Authors: Harada Kazumasa 
Published: August 2006

Abstract
Separations of geometrical isomers of the title complexes were carried out by a column chromatographic method. All three isomers of mer-, sym-fac-, and unsym-fac-[Rh(dien)2]3+ complexes were isolated. The only mer-isomer of the [Ir(dien)2]3+ complex was isolated, although trace fac-isomers were detected. Although the synthesis of a new [Rh(dpt)2]3+ (dpt = bis(3–aminopropyl)amine) complex was successful, that of [Ir(dpt)2]3+ was not. The only mer-[Rh(dpt)2]3+ isomer was obtained. These complexes were characterized by spectroscopic methods. In each case, the obtained unsym-fac- and mer-isomer were resolved in their antipodes. The crystal structures of three complexes were determined by an X-ray diffraction method. The crystal data are: for sym-fac-[Rh(dien)2]Br3, monoclinic, C2/c, a = 14.803(5), b = 9.102(3), c = 13.989(6) Å, β = 118.25(3)°, Z = 4, R = 0.0478; for mer-[Rh(dpt)2]Cl(ClO4)2, monoclinic, P21/a, a = 18.711(6), b = 12.942(5), c = 9.714(2) Å, β = 103.34(3)°, Z = 4, R = 0.0275; for mer-[Ir(dien)2] (ClO4)3·2H2O, orthorhombic, Aba2, a = 15.283(9), b = 14.736(4), c = 10.411(3) Å, Z = 4, R = 0.0341. The formation ratio of the isomers for the [Rh(dien)2]3+ complex is different from the known ratio for cobalt(III) analogs; this can be attributed to a difference in the M–N bond length based on a molecular mechanics calculation.
Mg2+-Promoted P–O vs. S–O Bond Cleavage in the Alcoholyses of Phenyl Phosphatosulfate
Authors: Eiki Toshio , Negishi Shin-ichi , Izumi Mitsunori , Ishida Naoko , Hada Hiroshi 
Published: August 2006

Abstract
In order to obtain insight into the selectivity of Mg2+ at the site of bond cleavage of P–O and S–O of the P–O–S linkage, metal ion-promoted alcoholyses of phenyl phosphatosulfate were studied. Mg2+ quantitatively promoted P–O bond cleavage in the methanolysis, but mixed cleavage of the P–O bond, which occurred partly due to hydrolysis by trace water and the S–O bond in the reaction of ethanol, 1- or 2-propanol. The ratio of the S–O bond cleavage against the mixed cleavage increased in a order EtOH (11.5%) &lt; n–PrOH (13.3%) &lt; i–PrOH (29.0%). On the other hand, Ca2+ and Zn2+ promoted selective P–O and S–O bond cleavage, respectively, in the reaction of 2-propanol as well as methanolysis.The medium-dependent change in the selectivity of Mg2+ at the site of bond cleavage was discussed.
Synthesis of Optically Active 4-Hydroxyalkanenitriles via an Enzymatic Reaction
Authors: Takagi Yumiko , Itoh Toshiyuki 
Published: August 2006

Abstract
Lipase-catalyzed enantioselective hydrolysis of esters of 4-hydroxyalkanenitriles was demonstrated for the first time. Efficient optical resolution was achieved when (±)-3-cyano-1-phenylpropyl 2-(phenylthio)acetate was hydrolyzed by lipase PS (Pseudomonas sp.).
Stabilization of Sugar-Boronic Esters of Indolylboronic Acid in Water via Sugar–Indole Interaction: A Notable Selectivity in Oligosaccharides
Authors: Nagai Yoshiro , Kobayashi Kenji , Toi Hiroo , Aoyama Yasuhiro 
Published: August 2006

Abstract
5-Indolylboronic acid (1) reversibly forms boronic esters with reducing sugars in water. The resulting boronates are stronger Lewis acids than the starting boronic acid in the deprotonation of water; pKa = 10 for 1 and &lt; 7 for its sugar-boronates. Thus, at pH 9.0, there exists an experimentally-evaluable sugar-binding equilibrium between neutral trivalent acid 1 and anionic tetravalent ester thereof, which can be conveniently monitored by fluorescence or 11B NMR spectroscopy. A characteristic aspect of the present sugar-binding process is the notable selectivity of host 1 for oligosaccharides. The binding constants for maltodextrins (α-1,4-linked glucose oligomers) increase with increasing chain lengths or repetition numbers of the glucose unit. Such a chain length selectivity and those among stereoisomers and linkage isomers of disaccharides are discussed in terms of intracomplex oligosaccharide–indole interaction.
Photochemical Reaction of 2,3-Di[(E)-styryl]pyrazine Derivatives in the Crystalline State and in Solution
Authors: Takeuchi Atsuo , Komiya Hitoshi , Tsutsumi Takehiro , Hashimoto Yukihiko , Hasegawa Masaki , Iitaka Yoichi , Saigo Kazuhiko 
Published: August 2006

Abstract
The photoreaction of 2,3-di[(E)-styryl]pyrazine derivatives was carried out in the crystalline state and in solution. Among them, 2,3-di(p-chlorostyryl)pyrazine and 2,3-di(p-cyanostyryl)pyrazine were photoreactive in the crystalline state and gave, upon photoirradiation, [2.2]orthocyclophanes in 76 and 58% yields, respectively. Such a topochemical photo-behavior was interpreted on the basis of X-ray crystallographic analyses of the crystals. The photoirradiation of 2,3-distyrylpyrazine in solution gave [2.2]orthocyclophane and anti head-to-tail type monocyclic dimer as the major products. The yields of the products varied depending on the solvent; with decreasing the polarity of the solvent, the yield of the cyclophane decreased, whereas the yield of the monocyclic dimer increased. In a similar manner, the photoirradiation of the other 2,3-distyrylpyrazine derivatives in acetonitrile/chloroform (10/1) or acetonitrile gave the corresponding [2.2]orthocyclophanes and monocyclic dimers, respectively, as major products through two types of excimers.
Substituent Effect Studies of Aryl-Assisted Solvolyses. I. The Acetolysis of 2,2-Bis(substituted phenyl)ethyl p-Toluenesulfonates
Authors: Fujio Mizue , Maeda Yasuyuki , Goto Mutsuo , Saeki Yoshihiro , Mishima Masaaki , Tsuno Yuho 
Published: August 2006

Abstract
The substituent effect on the acetolysis of 2,2-bis(substituted phenyl)ethyl p-toluenesulfonates at 90.10 °C can be described accurately in terms of the Yukawa–Tsuno (LArSR) relationship, giving a ρ value of −4.44 and an r value of 0.53. The substituent effect correlation of this system carrying two aryls is quite comparable to that of the 2-methyl-2-phenylpropyl system carrying a single aryl group, suggesting the close similarity in the structure of the transition states between the systems. The results can be reasonably accounted for on the basis of the accepted mechanism of this reaction, involving a rate-determining aryl-assisted transition state where only one aryl group of the two β-aryl groups participates.
Studies on Nickel-Containing Ziegler-Type Catalysts. IV. Dimerization of Propylene to 2,3-Dimethylbutenes. Part-II
Authors: Sato Hiroshi , Tojima Hideto 
Published: August 2006

Abstract
A small amount of water was found to increase the activity of catalyst (A) for the selective dimerization of propylene to 2,3-dimethylbutenes (DMBS),
Ni(naph)2/AlEt3/PR3/Diene/Chlorinated phenol, (A)
where Ni(naph)2 denotes nickel naphthenate. The activity increased by about three to five times upon the addition of H2O in amounts of 0.2 to 0.8 mole per mole of AlEt3; the maximum activity was obtained at around 0.5 molar ratio of H2O to AlEt3. On the other hand, the reaction product between H2O and AlEt3 in a molar ratio of 0.5 was isolated and was identified to be μ-oxo-bis(diethylaluminum), the accelerating effect of which was also proved to be high. It is, therefore, concluded that the Lewis acidity of μ-oxo-bis(diethylaluminum) activates the Ni–H bond of the active species through coordination to the square-planer complex of nickel.
Infrared Study of Hydrogenation of Benzoic Acid to Benzaldehyde on ZrO2 Catalysts
Authors: Kondo Junko , Ding Nan , Maruya Ken-ichi , Domen Kazunari , Yokoyama Toshiharu , Fujita Naoko , Maki Takao 
Published: August 2006

Abstract
The selective hydrogenation of benzoic acid to benzaldehyde on ZrO2 and Cr2O3–ZrO2 at 523 K was studied by IR spectroscopy. An enhancement of the hydrogenation rate of benzoic acid by Cr2O3 doping to ZrO2 was observed. The main role of Cr2O3 was considered to be the step of activating hydrogen. An intermediate species was observed based on the IR bands during a transformation from the adsorbed benzaldehyde to the benzoate at lower temperatures. This is discussed in conjunction with the reaction mechanism of the hydrogenation. The intermediate species was regarded as being the chemisorbed benzaldehyde by an analysis of the observed IR bands.
Formation of Polystyrene Latex Thin Films by Micelle Disruption Method
Authors: Saji Tetsuo , Ebata Ken-ichi 
Published: August 2006

Abstract
Polystyrene latex thin films were prepared on an indium tin oxide electrode by controlled-potential electrolysis of an aqueous solution containing a nonionic surfactant with a ferrocenyl moiety and dispersed latex particles. Thermal treatment rendered the film more transparent, and made the ITO electrode covered with the film inert against electrochemical reaction of hexacyanoferrate(II) due to the disappearance of the intergranular space in the film.
Methanol Synthesis from CO2 and H2 over a ZnO Catalyst. Effect of the Pretreatment with CO–H2 upon the Reaction
Authors: Fujita Shin-ichiro , Ito Hiroto , Takezawa Nobutsune 
Published: August 2006

Abstract
Methanol Synthesis from CO2–H2 was carried out over a ZnO catalyst. Pretreatments with a CO–H2 mixture caused a transient increase of the methanol formation as Bowker et al. found. It was shown that methoxide species was formed in the course of the pretreatments, being readily hydrolyzed to methanol by water formed via the reverse water gas shift reaction.
Enzymatic Kinetic Resolution of 2-Cyclohexen-1-ol Derivatives
Authors: Hagiwara Hisahiro , Nakano Takashi , Uda Hisashi 
Published: August 2006

Abstract
Optically active (S)-2-cyclohexen-1-ol derivatives and their enantiomeric (R)-acetates have been obtained in high enantiomeric excesses by enzymatic kinetic acetylation catalyzed by lipase AK.
Theoretical Simulations on d(CGCGAATTCGCG)2 with cis-syn Thymine–Thymine Cyclobutane Dimer
Authors: Rao Shashidhar N , Kollman Peter A 
Published: August 2006

Abstract
We present molecular mechanics and molecular dynamics simulations on the dodecanucleotide d(CGCGAATTCGCG)2, incorporating a cis-syn thymine–thymine cyclobutane dimer, represented as T[]T, at the TT site using the all atom force field. Although the starting optimized structures were essentially kink-free, kinked models are observed during the molecular dynamics simulations. Most conformational changes are seen in the sugar puckering and phosphodiester conformations of residues in and around the site of photolesion.
Improved Double-Zeta Description for the Atoms Li through Xe
Authors: Koga Toshikatsu , Seki Yousuke , Thakkar Ajit J 
Published: August 2006

Abstract
The conventional double-zeta (DZ) approximation uses two Slater-type functions χnlm’s with different exponents for the description of each occupied atomic orbital φnlm, where the two principal quantum numbers n’s are assumed to be the same. We show that the removal of this implicit restriction improves the DZ functions nontrivially for the ground-state atoms Li through Xe. The largest improvement 0.0267 a.u. in the atomic energy is found for Pd. The valence orbital energies are generally improved, particularly for the 4d-orbital of the fourth-row atoms. It is also found that the conventional DZ functions given in the literature can be further improved by reoptimization of the exponents.
Electronic Spin Alignment in Free Radical Reactions
Authors: Ohta Katsuhisa , Kawa-ai Ryousei 
Published: August 2006

Abstract
Classical spin alignment in radical reactions is studied by the GSF-HF wave function in H3 model system. The GSF-HF wave function introduces a simple classical picture of electronic spins directly and leads to the classical Heisenberg model. The instability of various spin alignments is studied on the GSF-HF electronic energy surface. In compensation for the classical spin freedom, the GSF-HF method does not satisfy quantum mechanical spin-symmetry. The GSF-HF wave function is analyzed with a projection operator constructed by a full-CI wave function.
Mechanism of Above-Threshold Dissociation of Hydrogen and Deuterium Molecular Ions
Authors: Sugawara Michihiko , Kato Miwa , Fujimura Yuichi 
Published: August 2006

Abstract
The mechanism of above-threshold dissociation (ATD) of both hydrogen and deuterium molecular ions has theoretically been investigated. A quantum-mechanical, time-dependent nuclear wave-packet theory has been applied to evaluation of the kinetic energy distributions of H2+ and D2+ photodissociations. The time-dependent shift of the kinetic energy distribution to the low energy side, which is common to both H2+ and D2+ ATD, is interpreted in terms of dynamic Stark shift. The different behavior in the intensity ratio of the kinetic energy distribution between H2+ and D2+ ATD is qualitatively explained by applying the Landau–Zener model to radiative coupling between the ATD channels involved.
Frontier-Orbital Interactions along the Intrinsic Reaction Coordinates of Ketene Dimerizations
Authors: Yamabe Shinichi , Minato Tsutomu 
Published: August 2006

Abstract
Ketene dimerizations to diketene and to 1,3-cyclobutanedione are studies theoretically. Their transition state (TS) structures are determined, for the first time, with correlated wavefunctions. The present calculation demonstrates that the two reactions proceed concertedly. The intrinsic reaction coordinates (IRCs) starting from the TSs are traced so as to seek the origin of the selectivity of the two reactions. At their initial stages, a one-center type charge transfer (donative orbital interaction) takes place, enhanced by polarization interactions in the charge-acceptor ketene. The back-donative orbital interactions are found to control the selectivity.
Molecular Integrals in the Equation of a Correlated Electronic Wave Function Including Interparticle Distances
Authors: Obara Shigeru , Hirao Kimihiko 
Published: August 2006

Abstract
An equation has been derived for a correlated electronic wave function satisfying the two-particle correlation cusp condition. Molecular integrals of spatial operators in the equation have been formulated based on the recursive formulations of general molecular integrals given by Honda, Sato, and Obara. An efficient scheme of computing them is proposed by taking advantage of the recursive and translational relations of the integrals.
Determination of the N–H Bond Lengths for Simple Peptides in the Solid State by Natural Abundance 15N Two-Dimensional Separated Local Dipolar Field (2D-SLDF) NMR Spectroscopy
Authors: Naito Akira , Tuzi Satoru , Saitô Hazime 
Published: August 2006

Abstract
The N–H bond lengths of simple petides were determined under the condition of high-resolution spectroscopy by analyzing the dipolar side-band patterns obtained from samples of natural abundance, as recorded by 15N two-dimensional (2D) separated local dipolar field (SLDF) NMR spectroscopy combined with cross-polarization and magic-angle spinning (CP-MAS) techniques. It was found that the dipolar side-band pattern obtained from the one-dimensional (1D) cross section taken from the 2D spectrum can be conveniently used to distinguish the 15N signal of the N–H group from that of the N–C group, whose peak positions are very close to each other. Further, spectral simulations of the 15N dipolar patterns of the peptides were performed in order to determine the N–H bond lengths of the amino acid residues of natural abundance at the C-terminus. These values were determined to be 1.07, 1.12, and 1.09 Å for Ala–Gly, Gly–Pro–Ala, and Ala–Pro–Gly, respectively, with an accuracy of 0.01—0.02 Å. The obvious difference in the bond lengths between the last two compounds suggests that the degree of interchain packing, as estimated from the N–H bond lengths, significantly differs between Gly–Pro–Ala and Ala–Pro–Gly. This finding is consistent with the previous data regarding the presence or absence of ring-puckering motion at the Pro residue, as examined by the 13C spin-lattice relaxation times in the laboratory frame.
Novel Electron Correlation in the Scattering Continuum for a Stability Analysis of the Electron Pair in the “Atomic” Level
Authors: Tachibana Akitomo 
Published: August 2006

Abstract
Wannier phenomenon is examined for a stability analysis of a time-reversal electron pair scattering. Imagine a pair of electrons interacting one another. It is found that the nature of the interelectron interaction is to stabilize the time-reversal scattering state. This nature survives even under the influence of a scattering center. To conclude, we shall prove the following results: 1) inside the reaction zone of the scattering center, one of the electrons is trapped, pressing the other electron to the barrier of the reaction zone, or letting the other electron go away over the barrier of the reaction zone, namely, a time-reversal scattering state of the electron pair is unstable, while 2) outside the reaction zone, if the critical radius rc is reached, then the time-reversal scattering state of the electron pair is stabilized. The critical radius rc has an intrinsic importance as a measure of the coherence length ξ of the Cooper pair that exhibits the time-reversal symmetry.
Theoretical Studies of Mg(1S, 3P) Atom Reaction Mechanisms with HF, H2O, NH3, HCl, H2S, and PH3 Molecules
Authors: Sakai Shogo 
Published: August 2006

Abstract
The reaction mechanisms of Mg (1S and 3P) atom and XH molecules (X = F, OH, NH2, Cl, SH, and PH2) were studied by ab initio molecular orbital methods. A localized molecular orbital centroid analysis along the reaction coordinate shows that the Mg(1S) atom insertion into the X–H bonds occurs through the pull–push mechanism. The activation barriers for the Mg(1S) atom insertion are approximately the same values for each groups (X = F and Cl, OH and SH, and NH2 and PH2).
For the Mg(3P) atom reactions with above six compounds, the hydrogen abstraction (produces MgH and H) and/or the exchange reaction (produces MgX and H) were studied. Both reactions of Mg(3P) atom are the same one with two-step mechanism. The first step is an electron transfer from a Mg atom into the X–H bonds, which corresponds the transition state. The activation barrier height of the reaction is explained by adiabatic electron affinity of the X–H bonds. The second step is the formation of the products (Mg–X+H or Mg–H+X), which is clarified by the difference of Mg–X and Mg–H bond energies.
A Theoretical Study of the Stability of the Fullerene-Like Cage Structures of Silicon Clusters
Authors: Kobayashi Kaoru , Nagase Shigeru 
Published: August 2006

Abstract
In order to provide theoretical insight into the structures of silicon clusters of current interest, several representative structural models proposed up to now for the medium size clusters are investigated by means of semi-empirical and ab initio molecular orbital calculations. Unlike general expectation based on the hitherto proposed structural models, it is suggested that silicon clusters also prefer spherical cage (fullerene-like) frameworks with the increase in the size, as do carbon clusters.