bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative Chemical Ionization Mass Spectrometric Studies on Dissociative Electron Attachment Processes of Chloroethylenes and Bromoethylenes
Authors: Nakagawa Seiko , Shimokawa Toshinari 
Published: September 2002

Abstract
The temperature dependence of the formation of negative ions from chloroethylenes (cis-1,2-C2H2Cl2, trans-1,2-C2H2Cl2, C2HCl3, C2Cl3F, C2Cl4) and bromoethylenes (cis-1,2-C2H2Br2, trans-1,2-C2H2Br2, C2HBr3, 1,1-C2Br2F2) was studied using negative chemical ionization mass spectrometry. The halide ion was observed for all samples. Other fragment anions, (M-X)- (parent molecule, M, less one halogen atom, X)- and X2- were produced for some samples. The former was observed for trans-1,2-C2H2X2 and C2HBr3, and the latter for 1,2-C2H2Cl2, cis-1,2-C2H2Br2, and C2HBr3. The branching ratio of X2- and (M-X)- decreases with increasing the temperature. The branching ratio of X2- is considerably different for chloroethylenes and for bromoethylenes.
A Thermodynamic Theory of Suspension II. Kinetic Theory for Viscosity of Suspension
Authors: Furukawa Junji 
Published: September 2002

Abstract
A dispersion is prepared by vigorous agitation for large particles of radius r or volume v larger than its critical rc or vc. The viscosity η is several Pa s and will be large compared with the viscosity of the solvent η0 of 10-3 Pa s. As a typical case, cement paste was studied by Hattori-Izumi who showed a gradual increase in η with time t. It was explained by collisions followed by cohesion, but gradual sedimentation seems more likely to be the origin. The author proposes a dynamic theory of viscosity.
The static viscosity is proportional to the energy of sedimentation Wsed, whereas dynamic viscosity η is expressed as exponential functions of Wsed. Molar concentration Wsed/v increases with the density of particles ρ, but decreases with the viscosity of solvent. The η value decreases by addition of water and fly ash. ζ-potential promotes dispersion. Contrary to an ordinary concept, cohesion heat may not act except in the coagulated state.
Time-dependent viscosity is caused by the relaxation of agitation energy Wag through three stages: rapid stage relaxation by collision of particles, slow stage relaxation by the consumption of Wc i.e., internal sedimentation energy due to viscous resistance and finally relaxation by coagulation. The second stage is expressed as ln η ≈ φ (Wc/vcRT)(t/τ), where Wc/vcRT = 1, vc = (rc/r)3, rc = 30 nm, r = 1 μm, τ = C0.5 (rc/r)2, C = η00.5/Δρ3/4 and τ is about 1 h.
For the case of very large particles e.g., fluidized bed, the relative volume v of the bed expands with the velocity of gas stream u0 like thermal expansion with a coefficient β and η is expressed as η = A exp (Wsed/β u0RT). This type of equation for polymeric material is known as Doolittle's equation, η = A exp (B/vf), vf being a free volume fraction.
Fluorescence Quenching of 1-Pyrenemethanol by Serotonin on the Surface of Polystyrene Latex Particles
Authors: Nakashima Kenichi , Koide Daigo , Gong Yong-Kuan 
Published: September 2002

Abstract
The fluorescence quenching of 1-pyrenemethanol (PyM) by serotonin (Ser) in polystyrene latex dispersions has been studied by steady-state and time-resolved fluorescence spectroscopy. From steady state fluorescence measurements, it is found that the quenching is remarkably enhanced on going from an aqueous homogeneous solution to a latex dispersion. This is attributed to that both PyM and Ser are effectively adsorbed onto the latex particles, as evidenced by measurements of the adsorption isotherms. Fluorescence decay curves of PyM in polystyrene latex dispersions have been successfully analyzed in terms of double exponential functions. The analysis reveals that the quenching of PyM fluorescence by Ser on polystyrene latex surfaces is mainly operated by a static mechanism, although the contribution of a dynamic mechanism is not negligible.
Further Insights into the Electrooxidation of N-Methyluric Acids and Correlation of Oxidation Potentials with Frontier MO Energies
Authors: Goyal Rajendra N , Thankachan P P , Jain Neena 
Published: September 2002

Abstract
The electrochemical oxidation of various N-methylated uric acids has been studied at a pyrolytic graphite electrode at physiological pH 7.2. The observed behavior was compared with uric acid to evaluate the effect of a methyl group. The Ep value was found to shift to less positive potentials when a methyl group is present at the N-1 position and to more positive potentials when substitution is at the N-3 position or at nitrogens of the imidazole ring. The values of ΔEp followed the additivity of the substituents effect only when two methyl groups are present in different rings. The methyl groups were also found to increase the electron density at N atoms of uric acids, and an excellent correlation between the oxidation potential and energy of the highest occupied molecular orbital was observed. On the basis of these studies it is concluded that the presence of a methyl group in the pyrimidine ring restricts the formation of allantoin. The peroxidase-catalysed oxidation of the N-methylated derivatives of uric acid was found to follow a pathway similar to that observed during electrochemical oxidation.
Electronic Spectra of Push-Pull 4-Phenylaminoazobenzene Derivatives
Authors: Makita Shohei , Saito Ayako , Hayashi Makoto , Yamada Shohei , Yoda Koji , Otsuki Joe , Takido Toshio , Seno Manabu 
Published: September 2002

Abstract
A series of push-pull type 4-phenylaminoazobenzene derivatives bearing an electron-withdrawing 4′-substituent were probed by electronic spectra in solution. The visible absorption maxima of these azobenzenes were correlated with the solvent parameters through the McRae theory as well as the solvent donor numbers. While the absorption spectra of these neutral species were solvent-dependent, those of protonated species were almost solvent independent. On the other hand, the absorption maxima and the rates of thermal cis-to-trans isomerization in a given solvent were correlated with Hammett constants. These results are discussed with the help of semi-empirical molecular-orbital calculations and compared with previously published data on related compounds.
Spectroscopic Study on Direction and Inclination of Helical Peptides in Monolayers Formed at the Air/Water Interface and on a Gold Substrate
Authors: Morita Tomoyuki , Kimura Shunsaku , Kobayashi Shiro , Imanishi Yukio 
Published: September 2002

Abstract
Monolayers at the air/water interface and self-assembled monolayers (SAMs) on a gold substrate were prepared from helical peptide derivatives carrying a 9-ethyl-3-carbazolyl group and a disulfide group. π-A Isotherms and circular dichroism spectra of Langmuir-Blodgett monolayers on a quartz substrate showed that the helical peptides were lying at the air/water interface. The molecular arrangement in the monolayer was analyzed by fluorescence quenching using in situ fluorescence spectroscopy. Computer simulations for the quenching experiment under the assumption of the mixed arrangement of parallel and antiparallel orientations explain the experimental data. On the other hand, the helical peptides in the SAMs were found to take standing orientation and a parallel arrangement by Fourier transform infrared reflection-absorption spectroscopy and fluorescence spectroscopy.
Studies of the Lowest Excited Triplet State of 3,3′-Biisoquinoline(dicyano)platinum(II) [Pt(CN)2(i-biq)] by Means of Time-Resolved Electron Paramagnetic Resonance and Optical Spectroscopy
Authors: Funayama Tomoyo , Kato Masako , Kosugi Hiroshi , Yagi Mikio , Higuchi Jiro , Yamauchi Seigo 
Published: September 2002

Abstract
The lowest excited triplet (T1) state of 3,3′-biisoquinoline(dicyano)platinum(II), [Pt(CN)2(i-biq)] was examined by time-resolved electron paramagnetic resonance (TREPR) and optical techniques in comparison with that of a ligand 3,3′-biisoquinoline (i-biq). Trans and cis i-biqs were assigned from obtained and calculated zero-field splittings (zfs') in the T1 state. The zfs parameter D increased with complex formation from 2.66 to 4.66 GHz in a rigid dimethylformamide solution; the polarization pattern of the spectrum was very different between the ligand and the complex. The triplet lifetime (ca. 1 s) of i-biq is also remarkably shortened in the complex (ca. 2 ms). These facts were analyzed in terms of the spin-orbit coupling (soc) between T1 (ππ*) and 1,3dπ*. From the analyses, the soc matrix element and the magnitude of delocalization of π* electrons over the Pt atom are obtained as 65 cm-1 and 0.02, respectively. The solvent dependences of the D value and the triplet lifetime also support the importance of the 1,3dπ* states for the T1 (ππ*) properties of the complex.
Reaction of Electronically Stabilized Thiones with Benzyne. The Isolation of Thiobenzophenone-Benzyne and Thiopivalophenone-Benzyne Adducts
Authors: Okuma Kentaro , Shiki Kyoko , Sonoda Shinya , Koga Yuji , Shioji Kosei , Kitamura Tsugio , Fujiwara Yuzo , Yokomori Yoshinobu 
Published: September 2002

Abstract
The reaction of thiobenzophenones (1) with phenyl[2-(trimethylsilyl)phenyl]iodonium trifluoromethanesulfonate (4) in the presence of tetrabutylammonium fluoride afforded the corresponding [4+2] cycloadducts, which are the first examples of thiobenzophenone-benzyne adducts. The reaction of thiopivalophenone (6) with benzyne prepared from 4 and tetrabutylammonium fluoride at room temperature gave [2+2] cycloadducts (7). When the reaction was carried out in refluxing dichloromethane, a mixture of 7 and [4+2] cycloadducts (13) was obtained.
Effect of High Magnetic Field on the Lifetime of Biradicals Generated from Benzophenone and Diphenylamine Bifunctional Chain Molecules
Authors: Duan Wenyong , Hashimoto Akihiko , Fujiwara Yoshihisa , Tanimoto Yoshifumi 
Published: September 2002

Abstract
The effect of high magnetic fields (≤ 13 T) on the lifetime of triplet biradicals (BPH·-O-(CH2)n-O-DPA·, n = 2, 4, 8, 16) composed of a protonated diphenylketyl radical (BPH·) and a diphenylaminyl radical (DPA·) is studied in N,N-dimethylformamide at room temperature by laser flash photolysis. On increasing the magnetic field from zero to ca. 2 T, the lifetime of BPH·-O-(CH2)n-O-DPA· (n = 4, 8, 16) increases steeply, and then decreases gradually in higher magnetic fields. The lifetime of BPH·-O-(CH2)2-O-DPA· decreases gradually with increasing the magnetic field with a shallow dip at ca. 2 T. The reversal of the effect observed in the lifetime of BPH·-O-(CH2)n-O-DPA·, n = 4, 8, 16 is interpreted in terms of spin-lattice relaxation which is induced by the anisotropic Zeeman interaction. The dip observed in the magnetic field dependence of the lifetime of BPH·-O-(CH2)2-O-DPA· is attributable to the S-T_ level crossing.
Charge-Density and Ring-Size Dependent Dimerization of 1-Arylcycloalkene Cation Radicals
Authors: Kojima Masanobu , Ishida Akito , Kuriyama Yasunao , Oishi Shigero 
Published: September 2002

Abstract
The γ-radiolysis of 1-arylcyclopentenes [Ar = Ph (1a); 4-ClC6H4 (1b); 4-MeC6H4 (1c); 4-MeOC6H4 (1d)] at 77 K initially gave transient absorption bands attributable to their monomer cation radicals (1a·+—1d·+), with λmax around 400 and 650—730 nm. In the case of 1a, 1b, and 1c, simultaneous formation of new absorption bands with λmax around 480—500 nm, attributable to the dimer cation radicals, was clearly observed upon warming along with a decrease in the monomer cation radical absorption bands. Using 355-nm laser photolysis at room temperature and an N-methylquinolinium salt as an electron acceptor, the rate constants for the formation of the dimer cation radicals (kdimer) and the reaction-rate constants for 1·+ with methanol (kMeOH) were determined. The reactivities of 1·+ with 1 and with methanol are discussed on the basis of the results obtained by a semiempirical molecular orbital calculation using the PM3 method. The results indicate that the reactivities of 1·+ depend not on its structure but on the charge density of the ethylene bond. In addition, dimerization of the cycloalkene cation radicals with larger ring size than 1, such as 1-phenylcyclohexene, 1-phenylcycloheptene, and 1-phenylcyclooctene cation radicals, was found to be remarkably dependent on the ring size.
Molecular States of 2-Naphthoic Acid in Solid Dispersions with Porous Crystalline Cellulose, as Investigated by Fluorescence Spectroscopy
Authors: Tozuka Yuichi , Yonemochi Etsuo , Oguchi Toshio , Yamamoto Keiji 
Published: September 2002

Abstract
2-Naphthoic acid (2-NPA) crystals were mixed with porous crystalline cellulose (PCC). After a heat-treatment of the mixture, no diffraction peaks due to 2-NPA crystals were observed on the XRD pattern. Fluorescence spectral data indicated that the molecular state of 2-NPA was modified by heating with PCC. The results of a fluorescence analysis also seemed to support the molecular state change of 2-NPA. When 2-NPA formed an inclusion complex by co-grinding with γ-cyclodextrin (γ-CD), the emission spectra of 2-NPA in this sample was similar to that in the heat-treated sample with PCC. Since γ-CD could be assumed to include two naphthyl moieties into the cavity, the fluorescence properties of 2-NPA after a heat treatment with PCC could be characterized by the excimer of 2-NPA on the PCC surface.
Magnetic Field Effect on the Intramolecular Exciplex Fluorescence of Chain-Linked Pyrene/N,N-Dimethylaniline Systems
Authors: De Rina , Fujiwara Yoshihisa , Zhang Baowen , Tanimoto Yoshifumi 
Published: September 2002

Abstract
The magnetic field effect (MFE) (≤ 13 T) on the intramolecular exciplex fluorescence of chain-linked pyrene/N,N-dimethylaniline systems is studied. In the case of pyrenyl-(CH2)2-O-(CH2)10-N(CH3)-phenyl, the exciplex fluorescence lifetimes are 34.2 (0 T), 50.6 (1 T), and 36.1 ns (13 T) in tetrahydrofuran/N,N-dimethylformamide (1 : 1) mixed solvent at room temperature. The lifetime decrease above 1 T is explained in terms of a Δg mechanism. Solvent dependence of the MFE maximum is discussed in terms of stabilization energy of the intramolecular radical ion pair, which is in fast dynamic equilibrium with the singlet exciplex. Influences of chain length and temperature are also discussed.
Site-Selective X-Ray Absorption Fine Structure (XAFS) Spectroscopy (2). XAFS Spectra Tuned to Surface Active Sites of Cu/ZnO and Cr/SiO2 Catalysts
Authors: Izumi Yasuo , Nagamori Hiroyasu 
Published: September 2002

Abstract
Site-selective XAFS spectra were measured by tuning the Rowland-type fluorescence spectrometer to each site of Cu/ZnO and Cr/SiO2 catalysts. The chemical shifts between Cu0 and CuI sites and between CrIII and CrVI sites were relatively large for model compounds (ΔE = 1.6 eV), and were utilized as the tune energies of site-selective XAFS. Site-selective XANES tuned to Cu0, CuI, and CrIII sites were successfully obtained. Based on the correlation between the chemical shift and the peak width (energy resolution of the fluorescence spectrometer), site-selective XANES spectra were analyzed. The population ratio of Cu metal, Cu2O, and CuI atomically dispersed on ZnO was estimated to be 70(±23) : 22(±14) : 8(±5). The contribution of the CrIII site to site-selective XANES tuned to the CrIII site was 94(±3)%.
1H NMR Spectra of Ternary Platinum(II) Complexes with N-Ethyl- or N-Benzyl-1,2-ethanediamine and 2,2′-Bipyridine or 1,10-Phenanthroline: Intramolecular Aromatic-Aromatic Interaction in Coordination Sphere, and It's Solvent and Temperature Effects
Authors: Goto Masafumi , Sumimoto Masamitsu , Matsumoto Takashi , Iwasaki Maki , Tanaka Yoshitomo , Kurosaki Hiromasa , Yuto Koji , Yoshikawa Yuzo 
Published: September 2002

Abstract
Square-planar complexes with the formula [Pt(L1) (L2)]X2, where L1 is di(ammine) or 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) and L2 is N-ethyl-1,2-ethanediamine (Eten) or N-benzyl-1,2-ethanediamine (Been), and X = NO3- or Cl-, were prepared. NMR measurements of D2O solutions of these complexes showed that the N-ethyl and N-benzyl groups are forced to take a pseudo axial disposition due to an intramolecular repulsion from hydrogen atoms of aromatic diamines for complexes where L1 = bpy or phen and significant upfield shifts due to the ring current effect were observed for the Been complexes. An analysis of coupling with N-H and 195Pt showed that the major rotamer due to rotation around CH2-NH is (-)-syn for the Been with a significant intramolecular stacking between aromatic rings of L1 and L2, but anti- for the Eten complexes. The solvent and temperature dependency of the upfield shift of the Been complexes are described; the protein denaturants, guanidinium chloride, and urea, act to reduce stacking as dioxane.
Production of Sb(IV) Chloro Complex by Flash Photolysis of the Corresponding Sb(III) and Sb(V) Complexes in CH3CN and CHCl3
Authors: Shinohara Nobuyoshi , Ohshima Masaaki 
Published: September 2002

Abstract
[SbCl6]2- was formed in the flash photolysis of [SbCl6]3- or [SbCl6]- in both solutions of CH3CN and CHCl3 in the presence of an excess of chloride. [SbCl6]2- had absorption maxima at 293, 328, and 390 nm in CH3CN. A similar absorption spectrum of [SbCl6]2- was also obtained in CHCl3. The lifetime of [SbCl6]2- was much shorter in CHCl3 than in CH3CN. [SbCl6]- was easily reduced to [SbCl6]3- upon continuous UV-irradiation in CH3CN as well as in CHCl3. On the other hand, [SbCl6]3- was oxidized to [SbCl6]- in CHCl3 in the presence of oxygen, but was not in CH3CN. The spectrum and the decay rate of [SbCl6]2- were not essentially affected by oxygen in both solutions of CH3CN and CHCl3.
A New and Convenient Method for the Synthesis of Dehydroamino Acids Starting from Ethyl N-Boc- and N-Z-α-Tosylglycinates and Various Nitro Compounds
Authors: Nagano Tanemasa , Kinoshita Hideki 
Published: September 2002

Abstract
Ethyl N-Boc- and N-Z-α-tosylglycinates, which were readily available from t-butyl or benzyl carbamate, ethyl glyoxylate, and sodium p-toluenesulfinate in formic acid, were reacted with a variety of nitro compounds in the presence of a base to afford the corresponding α,β-didehydroamino acid derivatives in good yields. Eventually, it was found that the (Z)-isomer was predominantly formed in the present method.
Langmuir Films of Amphiphilic [60]Fullerene Derivatives
Authors: Nakamura Yosuke , Taki Masumi , Asami Aya , Inokuma Seiichi , Hiratani Kazuhisa , Taguchi Kazuhiro , Higuchi Masahiro , Nishimura Jun 
Published: September 2002

Abstract
The stability of Langmuir films of [60]fullerene bisphenols 1—3, monophenols 4 and 5, and monocatechol 6 was investigated on the basis of surface pressure-area (π-A) isotherms. The films of 1—3 were found to be more stable than those of 4—6. Among bisphenols 1—3, cis-3-isomer 2 forms less stable Langmuir films than cis-2- (1) or e-isomer (3). This is ascribable to the lower hydrophilicity due to the intramolecular hydrogen bonding between the OH groups in 2, as demonstrated by the 1H NMR and IR spectroscopies. The contribution of intramolecular hydrogen bonding was also observed in monocatechol 6.
Effect of the N6-Methyl Group of the Adenine Ring on the Stacking Interaction
Authors: Itahara Toshio 
Published: September 2002

Abstract
In an effort to determine the effects of N6-methylation of the adenine ring on stacking, the molecular aggregation of 9,9′-(α,ω-alkanediyl)bis[6-(dimethylamino)purine] (1) and of 9,9′-(α,ω-alkanediyl)bis[6-(methylamino)purine] (2) were compared with that of 9,9′-(α,ω-alkanediyl)bis[adenine] (3) by NMR spectroscopy. The obtained concentration effects indicate that N6-methylation resulted in an increase in the population of intermolecular aggregates in the buffer solution at pD 7.0, and had an additive effect on the aggregation. It can be interpreted as a hydrophobic effect of the N6-methyl groups. The aggregation of 1 and 2 depended on the length of the polymethylene chains in a similar manner as that of 3, when the measurements were made on the solution of low concentrations. This suggests that the aggregates of 1, 2, and 3 were similar to each other through stacking between two adenine rings. Furthermore, the chemical shifts of the N6-methyl groups were slightly influenced by the length of the polymethylene chains and the changes of temperature. The N6-methyl group may be located outside the stacking. On the basis of these data, it may be concluded that the N6-methylation enhanced the stacking, but had little influence on the conformation of the stacking.
Synthesis of Amphiphilic Chitopentaose and Chitoheptaose Derivatives Using a Common Disaccharidic Synthon as the Chain Elongation Unit
Authors: Hinou Hiroshi , Umino Atsusi , Matsuoka Koji , Terunuma Daiyo , Takahashi Shunya , Esumi Yasuaki , Kuzuhara Hiroyoshi 
Published: September 2002

Abstract
With interest in clustering bioactive chitooligosaccharides, a pair of amphiphilic derivatives of around DP (degree of polymerization) 6, which has been considered to be the minimum molecular length for some kinds of bioactivity, was synthesized. Homologous derivatives of chitopentaose and chitoheptaose carrying tetradecanoyl and tetradecyloxy groups at the NH and C-1 of the reducing ends, respectively, were actually obtained using a 1,6-anhydro-2-azido-2-deoxy-β-D-glucopyranose derivative as the terminal precursor and a chitobiose derivative as the elongation unit. Micelle formation of both derivatives was assumed from the results obtained by dye solubilization tests.
A Facile Transformation of Terminal Olefins to vic-Difluoro Olefins: Electro-optical Properties of Liquid Crystalline Materials Having a vic-Difluoro Olefinic Moiety
Authors: Kanie Kiyoshi , Tanaka Yoichiro , Takehara Sadao , Hiyama Tamejiro 
Published: September 2002

Abstract
A facile synthetic method of vic-difluoro olefins from the corresponding olefins is explored and applied to the synthesis of liquid crystals (LCs) having a terminal vic-difluoro olefinic moiety. The physical and electro-optical properties of these LCs are compared with those of the corresponding parent olefinic LCs.
Photo-Cleavage of Carbon-Carbon Bond of α-Iodocycloalkanones Giving ω,ω-Dialkoxyalkanoic Ester in Alcohol
Authors: Ji Shun-Jun , Horiuchi C Akira 
Published: September 2002

Abstract
The irradiation at λ &gt; 300 nm of α-iodocycloalkanones with a high-pressure mercury lamp in alcohols containing a small amount of water afforded the corresponding ω,ω-dialkoxyalkanoic ester (65—88%) by photochemical cleavage of the C(I)-C=O bond at room temperature. In the case of a commercial fluorescent lamp as the irradiating light source, photochemical ring-opening products were also obtained. The irradiation of 2α-iodo-5α- and 4β-iodo-5β-cholestan-3-ones in methanol gave methyl 2,2-dimethoxy-2,3-seco-5α-cholestan-3-oate and methyl 4,4-dimethoxy-3,4-seco-5β-cholestan-3-oate in 78 and 62% yields, respectively. The photochemical behavior of the cleavage reaction of α-iodocycloalkanones is also discussed on the basis of 2-hydroxycycloalkanone as an intermediate.
Design of Optically Active Hydroxamic Acids as Ligands in Vanadium-Catalyzed Asymmetric Epoxidation
Authors: Hoshino Yujiro , Murase Noriaki , Oishi Masataka , Yamamoto Hisashi 
Published: September 2002

Abstract
New optically active hydroxamic acids bearing a 1,1′-binaphthyl group were prepared as ligands in a vanadium-catalyzed asymmetric epoxidation. The feature of these hydroxamic acids is a sterically hindered ligand. The asymmetric epoxidation with good selectivity and reactivity can be established by using VO(O-i-Pr)3 (5 mol%) and a small excess amount of ligand (7.5 mol%) with triphenylmethyl hydroperoxide (TrOOH) in toluene at -20 °C. Disubstituted allyl alcohols were epoxidized more rapidly than mono- or tri-substituted allyl alcohols, and were obtained in good to high enantioselectivities (48—94%ee). The transition state based on X-ray crystal structure of 1e is discussed.