bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excitation Wavelength Dependence of Phosphorescence and Hydrogen-Bonding Formation of Thioxanthone and 2,4-Diisopentylhioxanthone
Authors: Morita Hiroshi , Mori Shigeyasu , Yamaoka Tsuguo 
Published: July 2006

Abstract
Phosphorescence spectra of the ethanol solutions of thioxanthone(TX) and 2,4-diisopentylthioxanthone (DITX) exhibited excitation wavelength dependence at 77 K. In addition to the normal phosphorescence observed at 450 nm for TX and at 460 nm for DITX, a new red-shifted phosphorescence was resolved at 470 nm and 485 nm, respectively, when TX and DITX were excited at the absorption tail. The lifetimes and excitation spectra of the red-shifted phosphorescence were found to differ from those of the normal phosphorescence. Based on the study on UV absorption spectra and phosphorescence spectra measured with hydrated species of TX and DITX in ethanol–water solution at 77 K, the red-shifted phosphorescence is ascribed to the hydrogen-bonded species with water. In 2-methyltetrahydrofuran, phosphorescences of TX and DITX shift to the longer wavelengths and the lifetimes become longer when excited at the longer absorption tail, although the phosphorescence excitation spectra do not change appreciably.
Pressure-Induced Phase Transition and Superconductivity in Phosphorus
Authors: Shirotani Ichimin , Kawamura Haruki , Tsuji Kazuhiko , Tsuburaya Kazuhiko , Shimomura Osamu , Tachikawa Kyoji 
Published: July 2006

Abstract
The pressure-induced superconductivity in black phosphorus was measured along five different paths in a P–T phase diagram. The effect of the pressure on the superconducting transition temperature(Tc) depends strongly on the path in the P–T phase diagram. The results for several paths were compared with those obtained by Wittig et al. If black phosphorus was pressurized at the temperature of liquid helium, the Tc went up to 10.7 K and the onset temperature of transition was beyond 13 K at very high pressures. When red phosphorus was used as the starting material and pressurized at 4.2 K, Tc steeply increased with an increase in the pressure; it increased up to 13 K, while the onset temperature of transition reached 18 K at 30 GPa. This is the highest superconducting transition temperature among the elements. Pressure-induced phase transitions have also been studied by the X-ray techniques using synchrotron radiation at the temperature of liquid nitrogen. The pressure of the transition at 77 K was higher than that at room temperature. Two or three phases coexisted in a wide pressure (6–14 GPa) at 77 K.
Why Does the Hückel Rule Hold for a Variety of Monocyclic Conjugated Systems?
Authors: Aihara Jun-ichi , Ichikawa Hiroshi 
Published: July 2006

Abstract
Hückel’s 4n+2 rule is shown to be applicable to diverse monocyclic π systems by means of graph theory and frontier orbital theory. All monocyclic (4n+2)-π-electron systems are proved to have both kinetic and thermodynamic stabilities. They are predicted to be diatropic in nature.
Azoxy- and Azoferrocenes, and N-(Ferrocenylarylmethylene)anilines Formed via Aryliminodimagnesium(IDMg) Procedure. Effect of Ferrocenyl Group on IDMg Reaction and Molecular Structures of Products
Authors: Tsutsumi Toshiki , Okubo Masao , Yasuoka Noritake , Katsube Yukiteru 
Published: July 2006

Abstract
Some unsymmetrical azoxy- and azoferrocenes and N-(ferrocenylarylmethylene)anilines were obtained by the reactions of aryliminodimagnesium reagents (ArN(MgBr)2) with nitro- and aroylferrocenes. The types of products were same as those obtained in the similar reactions with nitrobenzenes and benzophenones. The different distribution of products arising from quite mild reactions was understood by the effect of bulky and electron-rich ferrocenyl group which retards the initial coordination and electron transfer processes, in comparison with that of phenyl group. The characteristic molecular structures of the new ferrocene compounds were studied by means of electronic absorption, 1H NMR, and X-ray crystallography. The results were summarized and discussed.
Heat Capacity of CH3D Adsorbed on Graphite at Monolayer Coverages between 0.3 and 7 K
Authors: Inaba Akira , Morrison James Alexander 
Published: July 2006

Abstract
Heat capacity measurements have been made on CH3D adsorbed on exfoliated graphite (Grafoil MAT) over the temperature range 0.3&lt;T&lt;7 K at two surface coverages near a monolayer, to evaluate predictions of the energy states of the adsorbed molecules, based on earlier studies of the properties of bulk solid CH3D and other isotopic methanes. Two Schottky-type anomalies are observed with maxima at 2 and 0.1 K; these are consistent with the predictions in a general way.
Molecular Orbital Treatment of Some Amino Acids
Authors: Abu-Eittah R , Obaid A , Basahl S , Diefallah E 
Published: July 2006

Abstract
INDO-molecular orbital calculations have been performed on a number of amino acids, namely, alanine, phenylalanine, some tyrosines and histidine. Computations on N-acetylhistidine are included for comparison. The results obtained for the charge densities and dipole moments were used to get a “structurefunction” correlation.
Complete Computer Analysis of NQR Data
Authors: Nogaj Boleslaw 
Published: July 2006

Abstract
Theories explaining temperature dependences of frequency, line width and spin-lattice relaxation times in Nuclear Quadrupole Resonance (NQR) spectroscopy have been presented in the form of mathematical expressions. Hence a complete analysis of experimental data can easily be implemented on any microcomputer. This was demonstrated by the results obtained from 35Cl NQR studies of p,p′-DDT. The computer analysis allowed to separate different mechanisms of quadrupole relaxation and determine characteristic parameters: moments of inertia of the molecule, librational frequencies and activation energies of rotating molecular groups. Besides numerical values, the printer working with the computer can produce plots of experimental points in different coordinate systems as well as the fit curves.
Molecular Rearrangements. XXVIII. Thermolysis and Photolysis of Some Hydroxamic Acid Derivatives
Authors: Badr M Z A , Fahmy A M , Mahgoub S A , Aly M M 
Published: July 2006

Abstract
Thermolysis and photolysis of benzohydroxamic acid and some of its derivatives have been investigated. Thermolysis of benzohydroxamic acid (BHA) either by heating in air or in a sealed tube gives NH3, H2O, CO, benzil, aniline, o- and p-aminophenols, phenoxazine, benzanilide, and benzoic acid. Whereas, thermolysis of N-(benzyloxy)benzamide (BBA) affords toluene, benzaldehyde, bibenzyl, stilbene, phenanthrene, acridine, and o- and p-aminodiphenylmethane in addition to the previous products. Analogous products were also obtained on pyrolysis of phenylacetohydroxamic acid. Photolysis of BHA and BBA in acetonitrile gives similar results to those of pyrolysis. A free-radical mechanism involving homolysis at different sites was postulated to account for the formation of such products.
Pinacol–Pinacolone Rearrangement Promoted by Polyphosphoric Acid Trimethylsilyl Ester (PPSE)
Authors: Kakimoto Masa-aki , Seri Takuya , Imai Yoshio 
Published: July 2006

Abstract
Pinacols afforded the corresponding pinacolones in high yields in the presence of the polyphosphoric acid trimethylsilyl ester (PPSE) at a temperature above 80 °C. Tetraphenylethylene oxide, in addition to benzopinacolone, was obtained in the reaction of benzopinacol under milder conditions. The solvent effect suggested that the rearrangement proceeded via the carbonium-ion intermediate.
Reinvestigation of the Diastereoselectivity of Kinetic Aldol Condensation of Cyclohexanone Lithium Enolate with Benzaldehyde
Authors: Hirama Masahiro , Noda Takeshi , Takeishi Shoichi , Itô Shô 
Published: July 2006

Abstract
Aldol condensation of cyclohexanone lithium enolate with benzaldehyde has been shown to give a considerably higher stereoselectivity at low temperature than that reported previously.
Diverse Kinetic Behaviors of the β-Structure Formation. A Study on Poly(S-carboxymethyl-l-cysteine)
Authors: Fukada Kazuhiro , Hattori Hideyuki , Maeda Hiroshi , Ikeda Shoichi 
Published: July 2006

Abstract
The pH jump kinetics of random coil-to-β-structure convertsion of poly(S-carboxymethyl-l-cysteine) were examined on two samples of degree of polymerization (DP) of 330 and 560. Various kinetic behaviors were observed depending on polymer chain length and concentration: single exponential with or without a lag and two exponential behavior. In unbuffered solutions, the rate enhancement of β-formation was confirmed.
Absorption and CD Spectral Properties of Bis(ethylenediamine)cobalt(III) Complexes with O-Bonded Sulfoxide and Seleninate
Authors: Konno Takumi , Okamoto Ken-ichi , Hidaka Jinsai 
Published: July 2006

Abstract
The absorption and CD spectral behavior of [Co{OS(CH3)CH2CH2NH2}(en)2]3+ and [Co{OSe(O)CH2CH2NH2}(en)2]2+ was discussed. The O-bonded seleninato isomer, Λ-(+)500CD-[Co{OSe(O)CH2CH2NH2}(en)2]2+, showed racemization at the chiral selenium atom in an aqueous solution and a shift of the equilibrium between the (R) and (S) configurations of the chiral selenium atom through the protonation on the pendant oxygen atom.
Dehydrooligopeptides. IX. Syntheses and Conversions of α-Dehydroglutamine Derivatives to N-Carboxy-α-dehydroglutamine Anhydride and Δ1-Dehydroglutaminyldipeptides
Authors: Yonezawa Yasuchika , Takefuji Nobuo , Takahashi Nobuyuki , Shin Chung-gi 
Published: July 2006

Abstract
Various kinds of Cbz-α-dehydroglutamine derivatives were synthesized by the reaction of Cbz-α-dehydroglutamic acids with a few primary amines, including l-α-amino acid ester, and subsequently transformed to N-carboxy-α-dehydroglutamine anhydride and several Δ1-dehydroglutaminyldipeptides.
Electrophilic and Nucleophilic Substitutions of 2-Amino- and 2-Hydroxy-1,3-diazaazulenes
Authors: Ebine Seiji , Takahashi Kazuko , Nozoe Tetsuo 
Published: July 2006

Abstract
2-Amino- (2) and 2-hydroxy-1, 3-diazaazulenes (3) underwent smoothly electrophilic bromination under basic conditions to give 2-amino-4,6,8-tribromo- (4) and 6-bromo-2-hydroxy-1,3-diazaazulenes (7), respectively. Bromo derivatives 4 and 7 underwent some nucleophilic substitutions, e.g., 4 reacted with ease with sodium methoxide to give 2-amino-4,6,8-trimethoxy-1,3-diazaazulene (10).
The Study of Partition Coefficients. The Prediction of Log P Value Based on Molecular Structure
Authors: Kasai Kenji , Umeyama Hideaki , Tomonaga Atsushi 
Published: July 2006

Abstract
An effort has been made to determine the partition coefficients from the physical quantities based on the molecular structure. The quantities are representatives of energies which constitute the solvation energy of the solute molecule. The logP value is expressed with them as
logP=−1.26+3.78φct−0.72μ1−1.28μ2
(N=244, R=0.959, S.D.=0.54, F=934).
For the practical use, the following equation is recommended:
logP=−1.36+3.89φct−1.09μ2−0.085UH+0.021UC−0.134UN−0.198UO
(N=244, R=0.976, S.D.=0.42, F=787).
Here, φct is the representative related to the charge-transfer energy and μ1, μ2, UH, UC, UN, and UO are those related to the electrostatic energy. The molecular structure of the solute molecule has been shown to be very important in the determination of the logP value. A logP value with a higher precision can be obtained by modifying the approximations used.
Conductive Salts of Tropylium Ions with Tetracyanoquinodimethan Anion Radical (TCNQ\ewdot) and Bisthiadiazolotetracyanoquinodimethan Anion Radical (BTDA–TCNQ\ewdot)
Authors: Yamashita Yoshiro , Hagiya Koji , Saito Gunzi , Mukai Toshio 
Published: July 2006

Abstract
Tropylium ions have been found to be good cations for forming highly conductive salts of TCNQ\ewdot. Tropylium ions with different reduction potentials were prepared. The first reduction potentials which are correlated with the substituent constants σp+ control the formation of the salts. The cations with higher reduction potentials underwent a reaction with TCNQ\ewdot to give neutral TCNQ and coupling products. The molar ratios of the initially formed salts are also dependent on the reduction potentials. The simple salts are only formed when the reduction potentials are lower than −0.43 V. This fact is rationalized by the difference in the ease of electron transfer from TCNQ\ewdot to tropylium ions which is determined by the reduction potentials. Some simple salts show significantly low electrical resistivities compared with usual TCNQ\ewdot simple salts. BTDA–TCNQ\ewdot also gave conductive salts of tropylium ions, indicating that BTDA–TCNQ is useful for forming organic semiconductors.
Dielectric Properties of the Hydrogen-Bonded Liquids. Steric Effects on Dielectric Properties in Isomeric Methylcyclohexanols
Authors: Takeshita Kimiya , Ikada Eiji , Ashida Michio 
Published: July 2006

Abstract
The dielectric properties of 2- and 4-methylcyclohexanols were studied in order to elucidate the molecular geometric dependences of the dielectric properties of alcohols. The Kirkwood correlaton factors g of the trans isomers are larger than those of the cis isomers. Especially the g of cis-2-methylcyclohexanol at 298 K is 0.75. The dielectric relaxation of all the methylcyclohexanols studied shows the characteristics of the Debye-like behavior frequently reported for primary alcohols. The activation energy of dielectric relaxation of 2-methylcyclohexanol is much larger than that of the other methylcyclohexanols. These facts are discussed in terms of the difference of the steric hindrance for the association through the hydrogen bond.
Proton Transfer and Aggregation Reactions in Aqueous Solutions of Isobutylamine and Isopentylamine Studied by Ultrasonic Methods
Authors: Nishikawa Sadakatsu , Yoshida Yukio , Nakano Ayumi 
Published: July 2006

Abstract
Ultrasonic absorption and velocity measurements have been performed in aqueous solutions of isobutylamine and isopentylamine at 25 °C. Two different relaxation phenomena are observed in these sample solutions. One of them, observed at a high frequency range, has been attributed to a proton transfer reaction of amines from the concentration dependence of the relaxation frequency and the maximum excess absorption per wavelength. The rate and thermodynamic constants have been determined for ion-pair formation and dissociation. The other, observed at a low frequency range becomes more striking as the hydrophobicity of the solute increases; it has been considered that the cause of the relaxation may be associated with a hydrophobic interaction. The formation of small aggregates has been speculated in both solutions. The rate and thermodynamic constants for the association and dissociation reactions of nonionized amine molecules have been estimated from the concentration dependences of the relaxation frequency and the maximum excess absorption per wavelength. Furthermore, the coupling effect of the two relaxation processes has been discussed briefly.
New Mesomorphic Compounds: N,N′,N″-Trialkanoyl-2,4,6-trimethyl-1,3,5-benzenetriamines
Authors: Harada Yukimasa , Matsunaga Yoshio 
Published: July 2006

Abstract
The homologous series of N,N′,N″-trialkanoyl-2,4,6-trimethyl-1,3,5-benzenetriamines has been prepared. The viscous birefringent melts are given by the butyryl to hexadecanoyl derivatives. The X-ray diffraction pattern recorded for the octanoyl derivative and the higher homologous members consists of two sharp inner peaks and a broad outer one assignable to the 100, 110, and 001 reflections respectively, indicating that the phase is hexagonal disordered columnar (Dhd). A more-structured high-temperature phase is displayed at lower temperatures by the nonanoyl to hexadecanoyl derivatives.
Some Aspects through Sedimentation Study on the Extremely Elongated Micelle Formed in Cationic Surfactant-Aromatic Additive Systems
Authors: Sakaiguchi Yuko , Hirata Hirotaka 
Published: July 2006

Abstract
Sedimentation studies were carried out upon systems composed of HTAB or HPB, a cationic surfactant, and several aromatic additives which were accompanied by remarkable viscoelasticity in a solution in which the existence of extremely elongated gigantic rod-like micelles was previously established by the authors as images under an electron microscope. Those elongated rod-like micelle systems appeared to be separated into two components: one showed floatation and the other sedimentation under a 6×104 rpm force field, providing rather pertinent values of S20ω in the order of 10−13s, compared with several proteins or other polymeric substances. After attaining an equilibrium state during sedimentation, the micellar particle weight was deduced to be about 1.2×107 amu. The obtained values seemed to be considerably smaller than those expected from the electron microscope images where the length of the rod-like micelles were assumed to be infinitely elongated. The discrepancy is likely to have been brought about by a degradation of the micelle chain under a strong centrifugal force field.
Catalytic Activity of Nonstoichiometric Niobium Oxide with Controlled Composition, NbO2.488–2.500, for Butene Isomerization
Authors: Murakami Yasushi , Wada Yuji , Morikawa Akira 
Published: July 2006

Abstract
The composition of niobium oxide was controlled between NbO2.488 and NbO2.500 by treating with mixture of water vapor and hydrogen gas at 873K. X-ray diffraction (XRD) study of the treated niobium oxide showed that only a phase of nonstoichiometric T-Nb2O5 was found in the range of NbO2.488–2.500 and a phase of NbO2 coexisted with the T-Nb2O5 phase by further reduction. The catalytic activity of the oxide for cis-2-butene isomerization had a maximum value at the O/Nb ratio of 2.494. The electron spin concentration of Nb4+ ion, and the amount of nitrogen monoxide adsorbed on the niobium oxide also showed a maximum value at the O/Nb ratio of 2.496 and 2.494, respectively. Coincidence in the dependences, on the composition of the reduced niobium oxide, of the catalytic activity, the spin concentration of Nb4+ ion, and of the amount of adsorbed nitrogen monoxide shows that isolated Nb4+ ion with unsaturated coordination is a catalytically active site.
Synthesis, Properties, and Crystal and Molecular Structure of Chloro[N,N-bis(2-hydroxyethyl)glycinato]copper(II)
Authors: Yamaguchi Hiromitsu , Nagase Makoto , Yukawa Yasuhiko , Inomata Yoshie , Takeuchi Toshio 
Published: July 2006

Abstract
The crystal and molecular structure of the title copper(II) complex was determined by the X-ray diffraction method. The crystal is orthorhombic with the space group Pbca, Z=8, a=14.18(1), b=15.835(7), c=8.188(3) Å. Full matrix least-squares refinements have led to a final R value of 0.047 for 2128 reflections. The copper atom is in a trigonal-bipyramidal geometry, ligated by a nitrogen atom, an oxygen atom of carboxylato group, two hydroxyl oxygen atoms and a chlorine atom. The complex has three five-membered chelate rings which are formed by one copper, one nitrogen, one oxygen, and two carbon atoms. There are two hydrogen bonds formed between the non-coordinated carboxylato oxygen atom and the hydroxyl hydrogen atom. The powder diffuse reflection spectrum of this complex exhibits a band characteristic of trigonal bipyramidal structure at 1000 nm. In the far-infrared absorption spectra of this complex, the bands at 340, 317, and 275 cm−1 are assigned to the stretching vibrations of Cu–N, Cu–Cl, and Cu–O (carboxylato), respectively.
Structures and Properties of Divalent Metal Complexes of an N2O2 Type Ligand, 6,6′-Bis(benzoylamino)-2,2′-bipyridine
Authors: Yamada Masaki , Araki Koji , Shiraishi Shinsaku 
Published: July 2006

Abstract
Complex formations of an N2O2 tetradentate ligand, 6,6′-bis(benzoylamino)-2,2′-bipyridine (babpH2) with various divalent metal ions were investigated. BabpH2 complexes of Ni(II), Co(II), and Zn(II) were obtained as dinitrate and/or diacetate, and their deprotonated complexes, [Ni(babp)], [Co(babp)], and [Zn(babp)], where babp represents the deprotonated form of amide protons of babpH2, were also isolated. The deprotonated complexes were shown to have high thermal stability up to 300 °C. The structures, stabilities, and spectral properties of these complexes were discussed in relation to the copper(II) complexes of babpH2 and babp.
Determination of Trace Metals in Seawater by Graphite Furnace Atomic Absorption Spectrometry after Preconcentration Using Synergistic Extraction
Authors: Ueda Kazumasa , Kubo Katsutoshi , Yoshimura Osamu , Yamamoto Yoshikazu 
Published: July 2006

Abstract
Trace Cd, Mn, Pb, Co, Ni, and Cu have been quantitatively separated and concentrated from seawater matrices with a low concentration (mmol dm−3 level) of 1,1,1-trifluoro-4-mercapto-4-(2-thienyl)-3-buten-2-one and trioctylphosphine oxide cyclohexane solution. The synergistic extract was directly injected into the furnace and a reproducible signal with little memory effect was obtained. The extracted adduct enhanced the AAS sensitivity during thermal decomposition processes, and simultaneously resulted in depression of the interferences. The detection limits of the analytes ranged from several ng dm−3 to 100 ng dm−3. The proposed technique provides both the preconcentration and determination for trace analysis by a single extraction using a small volume of sample. Coastal seawater samples were analyzed by the method.
The Crystal and Molecular Structures of Dithia[4.3](6,9)(6′,9′)purinophane, Dithia[4.4](6,9)(6′,9′)purinophane, and Dithia[3.3](6,9)(9′,6′)purinophane
Authors: Seyama Fumio , Sakata Yoshiteru , Kasai Nobutami , Misumi Soichi 
Published: July 2006

Abstract
Molecular structures of three purinophanes, dithia[4.3](6,9)(6′,9′)purinophane (1), dithia[4.4](6,9)(6′,9′)purinophane (2), and dithia[3.3](6,9)(9′,6′)purinophane (3), have been determined by means of X-ray diffraction. 1: monoclinic, space group P21/n, a=10.561(1), b=16.674(3), c=9.136(1) Å, β=90.29(1)°, V=1608.8(4) Å3, Dc=1.529 g cm−3 for Z=4. 2: monoclinic, space group P21⁄n, a=10.870(2), b=17.058(2), c=9,289(1) Å, β=94.15(1)°, V=1717.9(4) Å3, Dc=1.487 g cm−3 for Z=4. 3: monoclinic, space group P21/n, a=8.068(1), b=27.841(2), c=6.913(1) Å, β=111.0(1)°, V=1449.8(2) Å3, Dc=1.631 g cm−3 for Z=4. All structures were solved by the direct method, and refined anisotropically by the least-squares procedure. Final R values are 0.045, 0.053, and 0.050 for 1, 2, and 3, respectively. Molecular structures of 1 and 2 take very similar crossed form, whereas that of 3 reveals a different crossed form.
A Novel Synthesis of (±)-Prostaglandin B1 Methyl Ester
Authors: Naora Hirokazu , Ohnuki Takashi , Nakamura Asao 
Published: July 2006

Abstract
Five simple preparative methods of (±)-prostaglandin B1 (PGB1) methyl ester are described. All routes were started from a common intermediate, 7-(2-hydroxy-5-oxo-1-cyclopentenyl)heptanoic acid derived from cyclooctanone via two steps. The key reaction of these routes is a palladium-catalyzed vinylation. The methods provided other PGB1 congeners and are applicable to synthesize 11-functionalized PG systems.