bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Double-Zeta Description for the Atoms Li through Xe
Authors: Koga Toshikatsu , Seki Yousuke , Thakkar Ajit J
Published: August 2006

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

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

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

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

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

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

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

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

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.
A Theoretical Study on Bromonium Ion and Mercurinium Ion Intermediates
Authors: Yamabe Shinichi , Minato Tsutomu
Published: August 2006

Geometries of two title intermediates brought about by bromination and oxymercuration are studied with PM3 and ab initio molecular orbital calculations. For thirteen Br+ intermediates, the regular Markovnikov type structures are obtained and they depend upon the electronic donating strength. On the other hand, geometries of thirteen Hg(OCOCH3)2 intermediates are found to be almost the same and of the isosceles-triangle forms. Steric repulsion occurs not between two acetate groups but between one acetate and the substituents attached to olefins.
Molecular Orbital Study of Ion-Molecule Reactions Producing Hydrocarbons in Interstellar Space
Authors: Sonoda Yoko , Iwata Suehiro , Osamura Yoshihiro
Published: August 2006

The reaction mechanisms involving the formation of hydrocarbons in interstellar space were examined in terms of an ab initio molecular orbital calculation. The reaction energies and potential energy surfaces producing CH and C2H were evaluated based on the scheme for ion-molecule reactions proposed by the late H. Suzuki. According to the very attractive potentials of positive ions with the hydrogen molecule, most of the reactions proceed via energy-rich intermediates, such as CH4+, C2H+, C2H2+, C2H3+, and C3H+. Consequently, the model proposed by Suzuki has been confirmed concerning the result that the reactions are exothermic and without an energy barrier up to C3+ formation.
Thermodynamic Parameters for Formation of Through-Ring α-Cyclodextrin Complexes of Donor–Acceptor Linked Compounds: Comparison between D2O and H2O Solutions of Anthracene–Viologen Systems with Intramolecular Charge-Transfer Absorption Spectra
Authors: Toki Akira , Yonemura Hiroaki , Matsuo Taku
Published: August 2006

On the addition of α-cyclodextrin (CD), an intramolecular charge-transfer absorption band of an anthracene-viologen linked compound rapidly disappeared with elapsed time. The reason was ascribed to formation of a through-ring CD complex, which hinders direct interaction between the donor- and acceptor moieties. Thermodynamic parameters, including the energy of activation for complexation of α-CD, were evaluated by the use of the charge-transfer absorption band in D2O- and H2O solutions. Solvent deuterium isotope effects were observed with the free energy change on complexation, but not with the energy of activation for formation of the through-ring CD complex. An open, extended conformer of the linked compound was proposed as the model of the activated state for forming the through-ring CD complex.
The Formation of Crosslinked Polymer from Polyethylene in Benzenesulfonic Acid Aqueous Solution
Authors: Ishihara Yumiko , Saido Katsuhiko , Ikemura Tadashi , Takesue Tomoyuki
Published: August 2006

Polymer degradation was investigated by examining reactions with alternate daylight exposure and immersion in aqueous environments. Crosslinked polymers were produced by the carbonium ion reaction of carbonyl groups in benzenesulfonic acid aqueous solution.
Optical Resolution of 1-(3-Methoxyphenyl)ethylamine with Enantiomerically Pure Mandelic Acid, and the Crystal Structure of Less-Soluble Diastereomeric Salt
Authors: Sakai Kenichi , Hashimoto Yukihiko , Kinbara Kazushi , Saigo Kazuhiko , Murakami Hisamichi , Nohira Hiroyuki
Published: August 2006

Enantiomerically pure 1-(3-methoxyphenyl)ethylamine (1), which is a key intermediate of new phenyl carbamate drugs, was obtained by a diastereomeric method with high resolution efficiency (E) by using enantiomerically pure mandelic acid (2) as a resolving agent. The first crystallization of the mixture of diastereomeric salts from methanol gave a less-soluble diastereomeric salt in 70% yield with 99% diastereomeric excess. Recrystallization of the salt from 2-propanol gave (R)-1·(R)-2 in 97% yield with 100% diastereomeric excess (total E = 68%). The crystal structure of the less-soluble diastereomeric salt, (R)-1·(R)-2, was determined by X-ray crystallography. The crystal data are: Monoclinic, space group P21, a = 12.642(4), b = 5.890(2), c = 10.855(4) Å, β = 103.68(3)°, V = 785.4(5) Å3, Z = 2, R = 0.058 for 1450 unique reflections. The X-ray crystallography revealed that the high resolution efficiency was due to a layer-like arrangement of the enantiomerically pure acids, of which two layers sandwiched a layer of the amines by hydrogen bonds, as well as the helical column formed by hydrogen bonds between the acids and the amines, as observed for the less-soluble diastereomeric salt of 1-phenylethylamine with mandelic acid.
π-Facial Selectivity in the Diels–Alder Reaction of 5-Substituted 1,3-Cyclopentadienes
Authors: Ishida Masaru , Aoyama Takamichi , Beniya Yasufumi , Yamabe Shinichi , Kato Shinzi , Inagaki Satoshi
Published: August 2006

Theoretical and experimental studies are presented about π-facial selectivities in Diels–Alder reactions of 5-substituted cyclopentadienes (1). The HOMO and the NHOMO of 1 were readily predicted from the orbital mixing rule to be distorted to favor the syn- and anti-attack, respectively. The frontier orbital is dependent on the n-orbital energy (εn) of the substituent relative to the π-HOMO energy (επ) of the diene. For επ > εn, the syn π-facial selectivity is predicted since the HOMO contains the diene π-HOMO as the main component. For επ < εn, the anti π-facial selectivity is predicted since the π-HOMO most contributes to the NHOMO. For ε  π    εn, the loss of π-facial selectivity is predicted since the HOMO and the NHOMO both contribute to the reaction. The qualitative theory was examined by ab initio molecular orbital calculation on 1 (X = NH2, PH2, AsH2, OH, SH, SeH, F, Cl, and Br) and PM3 calculation of the activation energies on Diels-Alder reactions of 1 (X = NH2, PH2, AsH2, SbH2, OH, SH, SeH, TeH, F, Cl, Br, and I) with maleic anhydride. The observed selectivities of chalcogen-substituted cyclopentadienes (X = SPh and SePh) were in agreement with the theoretical prediction.
Utilization of 2,4-Di-t-butyl-6-(methoxymethyl)phenyl as a New Sterically Protecting Group
Authors: Yoshifuji Masaaki , Kamijo Kazunori , Toyota Kozo
Published: August 2006

A sterically hindered bromobenzene, 2-bromo-1,5-di-t-butyl-3-(methoxymethyl)benzene, was prepared and converted to the corresponding phosphonous dichloride. The dichloride was then utilized to stabilize a low-coordinate phosphorus compound such as 1-[2,4-di-t-butyl-6-(methoxymethyl)phenyl]-2-(2,4,6-tri-t-butylphenyl)diphosphene. Furthermore, the dichloride gave a cyclization product 1-chloro-2,1-oxaphosphaindan with elimination of chloromethane on standing at room temperature.
Synthesis and Properties of Polyacetylene Films Prepared by Ti(OEt)4–AlMe3 Catalyst System
Authors: Akagi Kazuo , Mochizuki Kazue , Aoki Yoshifumi , Shirakawa Hideki
Published: August 2006

Novel homogeneous catalyst system of composed tetraethoxytitanium–trimethylaluminum, Ti(OEt)4–AlMe3, is employed for synthesis of polyacetylene film. It is confirmed that the present system has a high catalytic activity for acetylene polymerization, and its activity is comparable to that of the representative Ti(O-n-Bu)4–AlEt3 catalyst system. Experimental conditions, especially for preparation and aging of the catalyst, are optimized in view of properties of polyacetylene film such as cis content, mechanical stretchability, and electrical conductivity. The homogeneity of the present catalyst aged at room temperature enables us to synthesize highly conductive non-stretched and stretched films whose electrical conductivities after iodine doping are 2.0 × 103 and 1.2 × 104 S cm−1, respectively. Discussion has also been made in terms of the effect of high-temperature aging for the catalyst, the role of co-catalyst as a reductant, and the dependence of electrical conductivity on film thickness.
Synthesis and Mercurophilic Properties of Sulfur-Containing Troponoid Crown Ethers
Authors: Takeshita Hitoshi , Yin Bing Zhu , Kubo Kanji , Mori Akira
Published: August 2006

Condensation of 2,7-dibromotropone and 7-bromo-4-isopropyl-2-(4-tolysulfonyloxy)tropone with oligoethylene glycol bis(2-mercaptoethyl) ethers gave sulfur-containing crown ether derivatives. Among these mercurophilic derivatives, triethylene glycol bis(2-mercaptoethyl) derivatives transport and extract mercury ion excellently.
Oxidative Generation of N-Acyliminium Ions from N-1-(Tributylstannyl)alkyl Carboxamides and Carbamates and Their Reactions with Carbon Nucleophiles
Authors: Narasaka Koichi , Kohno Yasushi
Published: August 2006

Oxidation of N-1-(tributylstannyl)alkyl carboxamides and carbamates with ammonium hexanitratocerate(IV) or ferrocenium hexafluorophosphate generates their N-acyliminium ions by the elimination of tributylstannyl radical under mild reaction conditions. The iminium ions thus formed react with various carbon nucleophiles to give the corresponding addition products.
Catalytic Asymmetric Aldol-Type Reactions Using a Chiral (Acyloxy)borane Complex
Authors: Ishihara Kazuaki , Maruyama Tohru , Mouri Makoto , Gao Qingzhi , Furuta Kyoji , Yamamoto Hisashi
Published: August 2006

In the presence of 20 mol% of a chiral (acyloxy)borane (CAB) complex prepared from BH3·THF and a chiral mono-O-acylated tartaric acid, achiral silyl enol ethers or ketene silyl acetals react with achiral aldehydes to afford the corresponding aldol-type adducts in good yields with high enantio- and diastereoselectivities. Furthermore, the reactivity of aldol-type reactions can be improved without reducing the enantioselectivity by use of 10—20 mol% of the CAB complex prepared from 3,5-bis(trifluoromethyl)phenylboronic acid and chiral tartaric acid derivative. The enantioselectivity can also be improved without reducing the chemical yield by use of 20 mol% of the CAB complex prepared from o-phenoxyphenylboronic acid and chiral tartaric acid derivative. The observed erythro selectivities and re-face attack of nucleophiles on carbonyl carbon of aldehydes imply that the extended transition state model is applicable.
Catalytic Decomposition of Nitrogen Monoxide over Valency-Controlled La2CuO4-Based Mixed Oxides
Authors: Yasuda Hiroyuki , Nitadori Taihei , Mizuno Noritaka , Misono Makoto
Published: August 2006

The direct decomposition of nitrogen monoxide (NO) to N2 and O2 was carried out over valency-controlled La2−xA′xCu1−yB′yO4 (A′ = Sr, Ba, Ca, Ce; B′ = Zr, Al) mixed oxide catalysts with a K2NiF4-type structure. The catalysts were characterized by XRD, XPS, redox titration, and oxygen TPD. It was confirmed by XPS that the surface and bulk compositions generally agreed and by redox titration that the average oxidation number (AON) of copper varied widely from 1.60 to 2.30. XPS showed that the valency of surface copper agreed with AON for AON ≤ 2, while it was in the Cu2+ state for AON > 2.0. The amounts of oxygen desorbed in TPD and the oxygen nonstoichiometry of La2−xSrxCuO4 increased with x in parallel. The catalytic activity for NO decomposition showed a maximum at x = 0.4—0.5, and a good correlation was found between the catalytic activity and AON for all of the catalysts tested. The decomposition of dinitrogen oxide (N2O) was also carried out for La2−xSrxCuO4 for a comparison. Based on the much slower rate of decomposition for NO than that for N2O and the significantly high rate of oxygen TPD, it was concluded that the oxygen desorption was not the rate-determining step in the steady state. The relative activities of the catalysts studied are all well explained by a mechanism in which the active sites for NO decomposition over these catalysts are coordinatively unsaturated Cu 2+ ions on the surface that can be easily oxidized to Cu3+ upon NO adsorption.
Magnetic Properties of the Dinuclear Copper(II) Compounds Bridged by Oxalato-Type Ligands
Authors: Emori Shuji , Todoko Kyoko
Published: August 2006

Various dinuclear copper(II) compounds bridged by the oxalato, oxamato, and oxamidato ligands were prepared and characterized by means of magnetic susceptibility and IR spectroscopy. The strong antiferromagnetic couplings through their carboxylate or carboxamidate groups are interpreted in terms of the ligand basicities and the electron withdrawal due to the resonance of the substituents.
Enhancement of Catalytic Activity of ZnCl2 in the Friedel–Crafts Benzylation of Benzenes Using Polar Solvents
Authors: Hayashi Eiji , Takahashi Yukio , Itoh Hironori , Yoneda Norihiko
Published: August 2006

Zinc chloride was successfully employed in the Friedel–Crafts benzylation of benzenes as a useful catalyst in the presence of polar solvents. Particularly, zinc chloride dissolved in primary alcohols, ketones, and water with a molar ratio of 1 was a highly effective catalytic system in the reaction.
Crystal and Molecular Structure of 2-Ethylthio-3-phenyl-1,3,4-thiadiazolium Tetrafluoroborate
Authors: Matsubara Yoshio , Kitano Kazutada , Sasaki You , Yoshihara Masakuni , Maeshima Toshihisa
Published: August 2006

2-Ethylthio-3-phenyl-1,3,4-thiadiazolium tetrafluoroborate (2) was synthesized by the reaction of 3-phenyl-1,3,4-thiadiazole-2(3H)-thione (1) with triethyloxonium tetrafluoroborate (Meerwein’s reagent) in acetonitrile at room temperature. A structural investigation of 2 was carried out on the basis of such spectral data as 1H NMR and 13C NMR spectroscopies and X-ray analysis. The crystallographic data of 1 and 2 are as follows: Orthorhombic space group of P212121, a = 10.116(2), b = 13.199(2), c = 6.690(2) Å, V = 893.3(3) Å3, and Z = 4 for 1, orthorhombic space group of Pbca, a = 16.449(6), b = 15.291(3), c = 10.833(2) Å, V = 2725(2) Å3, and Z = 8 for 2, respectively.
Stereoselective Introduction of Hydroxyl Groups via Hydrazones
Authors: Tada Masahiro , Chiba Kazuhiro , Izumiya Koji , Tamura Mihoko
Published: August 2006

Reduction of tosylhydrazones by hydride reagents in wet alcohol gave predominantly alcohols whose stereochemistries are opposite to those of the major reduction products of the corresponding ketones with sodium borohydride.
Acidic Properties and Catalytic Activity of Natural Kaolinitic Clays for Friedel–Crafts Alkylation
Authors: Sabu Kuzhunellil Raghavanpillai , Sukumar Rugmini , Lalithambika Malathy
Published: August 2006

Natural Kaolinitic clays containing transition metals Fe and Ti in their lattice have been examined for their acidic properties and catalytic activity for the alkylation of benzene with benzyl chloride. Calcination of the clays at 550 °C and subsequent acid-activation using 2 M HCl (1 M = 1 mol dm−3) rendered the kaolinite surface highly acidic with very high acid amount. These clays exhibited high catalytic activity and selectivity for the conversion of benzyl chloride to diphenylmethane. Al(III), Fe(II), and Ti(II) ions exsolved from the lattice of kaolinites by acid activation relocate in the interlamellar space and boost the Brønsted acidity of coordinated hydroxo and proposed to initiate the alkylation. In fact kaolinites having structural transition metal, on acid activation exhibited higher acid amount and enhanced catalytic activity than kaolinites devoid of transition metals and recently studied alkylation catalysts such as synthetic TiO2–SiO2–Al2O3 and Fe2O3–SiO2–Al2O3. Natural kaolinitic clays having transition metals in their lattice possess disordered structure and hence on acid activation results in the generation of larger amounts of relocatable cations, higher surface area and higher acidity compared to an ideal kaolinite. Also their acid amount and catalytic activity retained up to five successive regeneration cycles studied.
Mobility of Charge Carriers in Sublimed Films of Phenothiazine Derivatives
Authors: Yoshida Sadamu , Kozawa Kozo , Maruyama Yusei , Uchida Tokiko
Published: August 2006

Mobilities of charge carriers in sublimed films of three phenothiazine derivatives, benzo[b]phenothiazine, dibenzo[a,j]phenothiazine, and triphenodithiazine, were measured in surface-type cells at room temperature in both transient and stationary phtoconduction. The drift mobilities in films of these three materials, which are the sum of electron and hole mobilities, are on the order of 10−7—10−5 cm2 V−1 s−1. They do not seem to be affected by the orientation of molecules in the sublimed films.
Discotic Liquid Crystals of Transition Metal Complexes. XVI. Discotic Mesomorphism and Unique Chromism of Bis[1,2-bis(3,4-dialkoxyphenyl)ethanedione dioximato]palladium(II) Complexes
Authors: Ohta Kazuchika , Moriya Mitsuo , Ikejima Mayumi , Hasebe Hiroshi , Fujimoto Tetsuya , Yamamoto Iwao
Published: August 2006

Bis[1,2-bis(3,4-dialkoxyphenyl)ethanedione dioximato]palladium(II) complexes, (abbreviated [Pd{(CnO)4dpg}2]; n = 1—12)have been synthesized and characterized. It was found that each of the [Pd{(CnO)4dpg}2] (n = 2—12) complexes has an enantiotropic discophase (Dhd). The clearing points of the [Pd{(CnO)4dpg}2] (n = 4, 8, 12) complexes are higher than those of the corresponding [Ni{(CnO)4dpg}2] (n = 4, 8, 12) complexes. Interestingly, the [Pd{(CnO)4dpg}2] complexes exhibit thermochromism and solvatochromism similar to that of [Ni{(CnO)4dpg}2] complexes.
Discotic Liquid Crystals of Transition Metal Complexes. XVII. The Mechanism of “Mesomorphic Thermochromism” in Bis(octasubstituted diphenylglyoximato)palladium(II) Complexes Established by Their Temperature-Dependent Electronic Spectra
Authors: Ohta Kazuchika , Moriya Mitsuo , Ikejima Mayumi , Hasebe Hiroshi , Fujimoto Tetsuya , Yamamoto Iwao
Published: August 2006

The bands in the electronic spectra of the [Pd{(C12O)4dpg}2] and [Pd{(C6)4dpg}2] complexes were assigned by using the results of temperature-dependent electronic spectral measurements. The temperature-dependent electronic spectra of “cast samples” of the complexes showed that two characteristic bands shift to higher energy (blue shift) with increasing temperature. The band which is located at a longer wavelength was assigned to the 4dz2–5pz transition (d–p band), and that located at a shorter wavelength to the metal-to-ligand charge-transfer transition (MLCT band). The absorption intensities of both bands strongly depend on the sample film preparation manners and temperatures. From these facts, the mechanism of this unique “mesomorphic thermochromism” has been established.
Dispersion and Fixation of 12-Tungstophosphate Anion on a Silica Surface Modified with Silane Agents Having an Amine Group and Their Catalytic Properties
Authors: Kamada Masahiko , Nishijima Hirotaka , Kera Yoshiya
Published: August 2006

Silica gel (SiO2) was modified by a dip-cure method with silane coupling agents having an amine-group: (3-anilinopropyl), (3-aminopropyl), and N-[3-(2-aminoethyl)aminopropyl] trimethoxysilanes. 12-tungstophosphate (PW12) was deposited on the carriers as a test catalyst material. The amounts and the dispersed states of the silane agents and PW12 on the modified SiO2 were successfully analysed by gravimetry as well as UV and FT-IR spectrometries. The amount of PW12 deposited increased in proportion to the amount of the silane agents on SiO2 in the case of deposition under a constant concentration of PW12-solution, although only a little PW12 was deposited directly on SiO2. The acidic site of PW12 was confirmed to interact directly with the amine-group on the modified SiO2, and the strength of the interaction was correlated with the basicity of the amine-group. The activity per gram of catalyst for the dehydration of 2-propanol as a test reaction is generally higher than that on a directly deposited one, although the activity per PW12 unit certainly decreases with the SiO2-modification. The activity was confirmed to increase by a pretreatment at high temperatures, such that the amine-group was completely decomposed. It was clearly shown that the present modification method could be effectively applied for preparing a highly dispersed heteropoly acid catalyst on carriers.
Efficient :CF2 Generation by IR Multiphoton Dissociation : Time Resolved Observation of Infrared Chemiluminescence from the :CF2 + O2 → COF2 + O Reaction
Authors: Chowdhury Pradyot Kumar
Published: August 2006

IR multiphoton dissociation of Octafluorocyclopentene is used as an efficient means for the generation of :CF2. Time resolved infrared chemiluminescence has been observed from the reaction of ground state :CF2 (X1A1) radicals with molecular oxygen, generating COF2 as a product. IR emission observed around 5 μm region has been assigned to ν1 and 2ν2 modes of COF2. The kinetic measurements of the reaction as a function of oxygen pressure suggest a rate constant to be 5 × 1011 cm3 mol−1 s−1, which corresponds to a :CF2 temperature of ≤3650 K.
Hydrates of Organic Compounds. XVIII. The Formation of Hydrates of Tetraisopentylammonium Salts Having Polyanions
Authors: Nakayama Haruo , Baba Kei
Published: August 2006

In order to confirm the formation of hydrates, both the solid–liquid phase diagrammatic method and the thermal analytic method using a differential scanning calorimeter were applied to binary mixtures of water with various tetraisopentylammonium salts having polyanions, poly(vinyl sulfate) anion and poly(styrenesulfonate) anion, as well as related low molecular-weight anions, ethyl sulfate ion and p-ethylbenzenesulfonate ion. It was found that the two salts with the polyanions and ethanesulfate could form hydrates with large hydration numbers: The melting point and hydration numbers were estimated to be around 16.5 °C and 34 ± 2 for the tetraisopentylammonium poly(vinyl sulfate) hydrate; around 11 °C and 35 for the tetraisopentylammonium poly(styrenesulfonate) hydrate; and 12—13 °C and 37 ± 2 for the tetraisopentylammonium ethyl sulfate hydrate, respectively. The formation of the hydrate phase around the tetraisopentylammonium cation attached to a surface of cation-exchange resins was also examined.
Investigation of Electron Transfer through the Interfacial Electrical Double Layers of Various Micelles
Authors: Fujihira Masamichi , Yanagisawa Masahiro , Kondo Toshihiro
Published: August 2006

In order to estimate the inner potential difference of an electrical double layer (EDL) created between the ionic hydrophilic head group of the amphiphile and its counter ion, the electrochemical characteristics of the ferrocene derivatives solubilized in three kinds of micelles were measured, and are discussed so as to clarify the effect of the EDL on the electron transfer through the interface.
Unimolecular Dissociation of Benzyl Halide Radical Anions Studied by Low-Temperature Pulse Radiolysis
Authors: Kimura Norio , Takamuku Setsuo
Published: August 2006

The one-electron reduction of benzyl halides (BzX; X = F, Cl, Br) by solvated electrons in 2-methyltetrahydrofuran has been investigated by using a pulse radiolysis technique at different temperatures above 77 K. The radical anions of BzX (λmax = 300 nm) formed by the capture of an electron in the π*-orbital of the benzene ring dissociate into Bz· (λmax = 320 nm) and X− via Bz•/X− complexes (λmax = 340 nm for BzCl and 370 nm for BzBr). The corresponding species were observed with 4-phenylbenzyl halide at 85 K and below. A spectral change observed at 95 K has been attributed to a structural change of the biphenylyl group. The dissociation rate of the radical anions increased in the order BzF < BzCl < BzBr. On the basis of these results, the reaction mechanism is discussed.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 >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.
Correlation of the Surface Basicity of Alkali Metal-Modified MgO Evaluated by the Two Parameters
Authors: Kanno Tohru , Kobayashi Masayoshi
Published: August 2006

The surface basicity of alkali metal-modified MgO was evaluated by both TPD and IR techniques and a good correlation between the two results was obtained, in which Li showed the distinct modification effect on MgO.
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

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.