bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the L-DOPA and Carbidopa Reactivity against Pyridoxal 5′-Phosphate. A Kinetic Study
Authors: Echevarría Gorostidi Gerardo R , Santos José G , Figueroa Julia , Blanco Francisco García 
Published: September 2002

Abstract
The apparent rate constants of the formation (k1) and hydrolysis (k2) of Schiff bases formed by pyridoxal 5′-phosphate (PLP) with L-3,4-dihydroxyphenylalanine (L-DOPA) at a variable pH, 25 °C and an ionic strength of 0.1 M was determined. The individual rate constants for the formation and hydrolysis of Schiff bases corresponding to the different chemical species present in the medium as a function of its acidity were also determined, as were the pKa values for the Schiff bases. The formation and hydrolysis rate constants of the Schiff bases were compared with those of the reaction of PLP with carbidopa (CD), showing that the reactivity of L-DOPA and carbidopa on PLP are the same over the whole pH range studied, and that the hydrolysis rate is somewhat greater for the Schiff bases between PLP and CD than those between PLP and L-DOPA.
Determination of the Chemical Bonding of Ionic Lithium and Proton Exchange in Spinel-Type Manganese Oxides
Authors: Kim Yang-Soo , Kanoh Hirofumi , Hirotsu Takahiro , Ooi Kenta 
Published: September 2002

Abstract
A study of the electronic structure and chemical bonding of the Li ions and protons inserted in manganese oxides was performed by a first-principles molecular-orbital method using model clusters (Mn28O40)32+ for λ-MnO2 and (X5Mn12O40)n- for XMn2O4{n = 31 (X = H) and n = 33 (X = Li)}. The discrete-variational (DV)-Xα method was employed and Mulliken’s population analyses were carried out. Strong covalent interactions operate between Mn and O ions in the manganese oxides. Li and hydrogen in manganese oxides are highly ionized. These results are likely to be a very important factor in determining the excellent selectivity of spinel-type manganese oxides for Li+ ions and the exchange between Li+ and protons.
Ortho-Fused Heterocyclic Derivatives as Efficient Electroluminescent Materials
Authors: Tanaka Kazuhiko , Osuga Hideji , Tsujiuchi Naoki , Hisamoto Masashi , Sakaki Yuichi 
Published: September 2002

Abstract
We describe the synthesis and optical properties of 1,2-dithienylethylene derivatives (DTE-8–15) consisting of ortho-fused heterocyclic systems such as benzodithiophene and naphthothiophene. The compounds 8–13 are highly fluorescent in toluene solution and their intensities are approximately two times as large as 4,4′-bis(2,2-diphenylethenyl)biphenyl (18). The fluorescence quantum yields of compounds 8–15, except for 14, are 2 times as high as that of 18. Although a maximum luminance of 9 in a multilayer device of structure ITO/CuPc/NPD/9/Alq3/LiF/Al is low (186 cd m-2), the brightness is significantly improved by doping the host emitters such as 18 and 9,10-bis(2-biphenylyl)-2-(t-butyl)anthracene (19) with 9. The electroluminescent (EL) device doped with 8 (5%) in the layer of 19 exhibits blue emission with a maximum luminance of 30000 cd m-2 at a driving voltage of 14 V and a luminous efficiency of 2.42 lm W-1 at 5V.
A Chiral M6L4 Cage Complex Assembled from a D2h-Symmetric Ligand: Self-Assembly, Structure, and Chirality Observation
Authors: Kubota Yasuo , Biradha Kumar , Fujita Makoto , Sakamoto Shigeru , Yamaguchi Kentaro 
Published: September 2002

Abstract
Chiral M6L4 cage structures were self-assembled by mixing a D2h-symmetric ligand with a cis end-capped (diamine)Pd(NO3)2 complex [diamine = ethylenediamine (en), 2,2′-bipyridine (2,2′-bpy), or 1,2-cyclohexanediamine (cxn)]. This self-assembly was achieved by exploiting the template effect of an aromatic guest molecule. The structures were confirmed by CSI-MS, NMR observations, and X-ray crystallographic analysis. Having C2 molecular chirality, two diastereomers were differentiated by attaching a chiral auxiliary on Pd(II).
Hydrophobicity and Structure of 1,2,4-Triazole Derivatives Bearing 1-Carbamoyl and 3-Sulfonyl Groups
Authors: Ohkata Katsuo , Yano Tomoyuki , Kojima Satoshi , Hiraga Yoshikazu , Yoshii Tomoko , Hori Masahiro 
Published: September 2002

Abstract
Various 3-sulfonyl-1,2,4-triazole-1-carboxamides (5a–h) were synthesized and their hydrophobicities were evaluated from their retention time in reversed-phase HPLC chromatography. Although the compounds have rather complex structures, a good linear relationship was observed between log k′ of these compounds derived from the retention time of HPLC and log PH for water–hexadecane partition coefficients of related alcohols. In regards with the rotation about the O2S–C(ester part) single bond, the preference for a gauche conformer relative to the anti form was revealed by both X-ray structural analysis of 5a and calculations at the AM1 level. In this conformation, substituents are arrayed to have the largest separation between the hydrophilic and hydrophobic parts. This can be rationalized as the primary reason for the good linearity.
Synthesis and Properties of Unsymmetrical Indamine Dyes Derived from 2,2′-Bis(dialkylamino)-4,5′-bithiazoles
Authors: Kim Jae Joon , Funabiki Kazumasa , Muramatsu Hiroshige , Shiozaki Hisayoshi , Matsui Masaki 
Published: September 2002

Abstract
Unsymmetrical indamine dyes have been synthesized by the reaction of 2,2′-bis(dialkylamino)-4,5′-bithiazoles with 4-nitrosoanilines followed by heating with metal salts. The first UV/vis absorption bands of indamine dyes were observed at λ = 648–725 (ε = 3900–55000) nm in dichloromethane, being more bathochromic than those of the corresponding cyanine derivatives. The chromophoric system for these indamine dyes was described as a mixture of the π–π* transition coming from the alternant chromophore inside the bithiazolyl moiety and the intramolecular charge-transfer transition from the anilino residue to the bithiazolyl moiety. Negative solvato- and halochromism have been observed for these indamine dyes.
Synthesis of Neoflavenes by a Palladium-Catalyzed Cross-Coupling Reaction of 4-Trifluoromethylsulfonyloxy-2H-Chromenes with Arylboronic Acids
Authors: Eguchi Tetsuya , Hoshino Yukio , Ayame Akimi 
Published: September 2002

Abstract
Under anhydrous conditions, 4-phenyl-2H-chromenes were obtained in excellent yields by a cross-coupling reaction of 4-trifluoromethylsulfonyloxy-2H-chromenes with arylboronic acids, except for o-methoxyphenylboronic acid, in the presence of K2CO3 and several palladium catalysts. Although copper(I) iodide, used as a co-catalyst, showed no effect on this reaction, it was confirmed to act in the case of the coupling reaction of 4-trifluoromethylsulfonyloxy-2H-chromene with tributylphenyltin, instead of phenylboronic acid, in the presence of [Pd(PPh3)4].
Enantioselective Cathodic Reduction of Some Prochiral Ketones in the Presence of (1R,2S)-(-)-N,N-Dimethylephedrinium Tetrafluoroborate at a Mercury Pool Cathode
Authors: Yadav Ashok K , Singh Arpita 
Published: September 2002

Abstract
The enantioselective cathodic reduction of some prochiral ketones viz. acetophenone (I), propiophenone (II), butyrophenone (III), valerophenone (IV), isobutyrophenone (V), and pivalophenone (VI) has been accomplished at a mercury pool cathode in N,N-dimethylformamide (DMF)–water (90 : 10) using tetrabutylammonium fluoroborate (TBA·BF4) as a supporting electrolyte in the presence of (1R,2S)-(-)-N,N-dimethylephedrinium tetrafluoroborate (DET). Cyclic voltammetric investigations have been carried out and a probable mechanism of the process has been presented.
Preparation and Characterization of Dye-Doped Zirconia Gel Films from Zirconium Tetra-n-butoxide Stabilized with Diethanolamine or Acetoin
Authors: Matsui Masaki , Yoshimura Yasuhiro , Ohya Tomokazu , Ban Takayuki , Ohya Yutaka , Takahashi Yasutaka 
Published: September 2002

Abstract
Zirconia gel films were prepared by a dipping method from a 2-propanol solution of zirconium tetra-n-butoxide (ZTNB) stabilized with diethanolamine (DEA) and acetoin. In the case of the ZTNB–DEA system, crystallization to zirconia occurred at 480 °C, while in the case of the ZTNB–acetoin system it occured at 380 °C. The density of gel film prepared from the ZTNB–DEA system was higher than that from the ZTNB–acetoin system. Neutral acetoin could act as a good stabilizer for dye-doped ZTNB gel films. The photostability of dyes depended on the combination between dyes and stabilizers. DEA could act as an anti-oxidizing reagent and an electron donor to depress and accelerate the photo-decomposition of the dyes, respectively.
Dynamics of the Hydration of Halogenoalcohols in Aqueous Solution
Authors: Okouchi Shoichi , Ashida Tatsuya , Sakaguchi Shinobu , Tsuchida Kazushi , Ishihara Yoshimasa , Uedaira Hisashi 
Published: September 2002

Abstract
The 17O NMR spin-lattice relaxation times (T1), of the solvent water in aqueous solutions of halogenoalcohols were determined as a function of the concentration at 298 K. The values of the dynamic hydration number, nDHN ≡ nh(τch/τc0 -1), were determined from the concentration dependence of T1. In order to investigate the effect of the halogen atom on hydrophobic hydration, the ratios (τch/τc0), of the rotational correlation times,(τch), of water molecules around the solute to those of pure water,(τc0), were estimated from the nDHN and the coordination numbers (nh), which were calculated from the water-accessible surface area (ASA) of the solute molecule. (i) The τch/τc0 value decreased in the order EtOH &gt; IEtOH ≥ BrEtOH ≥ ClEtOH &gt; FEtOH for monohalogenoethanols, EtOH ≥ Cl3EtOH &gt; Cl2EtOH ≥ ClEtOH and EtOH ≥ F3EtOH &gt; FEtOH for polyhalogenoethanols, and PrOH &gt; ClPrOH and i-PrOH &gt; (CF3)2CHOH for halogenopropanols. (ii) The ASA dependence of the τch/τc0 value for chloroethanols was smaller than that for fluoroethanols. These results are explained by the disturbance of hydrophobic hydration by the halogen atom and the size effect.
New Treatment Method for Dilute Hydrochloric Acid Using Magnesium-Aluminum Oxide
Authors: Kameda Tomohito , Yoshioka Toshiaki , Uchida Miho , Miyano Yoshinori , Okuwaki Akitsugu 
Published: September 2002

Abstract
Magnesium-aluminum oxide (Mg-Al oxide) was shown to be superior to CO32- intercalated hydrotalcite (CO3-HT) for removing dilute hydrochloric acid. Cl- in a 0.5 M HCl solution could be quantitatively removed by adding 1.75-times the stoichiometric quantity of Mg0.70Al0.20O at 60 °C for 1 h. The solution after the reaction was weakly alkaline. This reaction could be adequately described as being first order for the HCl concentration, and the apparent activation energy was 49.3 kJ mol-1. The amount of Cl- removal per 1 g of Mg-Al oxide in the first use was 3.08 meq at a Mg/Al molar ratio of 2.0 and 2.89 meq at a ratio of 3.5.
Influences of C1–C3 Alcohols and Purities of TiO2 Powders on Their Photoluminescence Properties at Room Temperature
Authors: Nakajima Hiromitsu , Itoh Kiminori , Murabayashi Masayuki 
Published: September 2002

Abstract
We have investigated the photoluminescence (PL) of rutile and anatase TiO2 powders at room temperature in vacuum, in air, and in air with one of C1–C3 alcohols (methanol, ethanol, 1-propanol, and 2-propanol). For rutile TiO2 powder, we observed that the PL intensities in these atmospheres, except air, increase linearly with the square root of the UV irradiation time (t0.5), and found that the time dependence agrees with that of the integrated amount of photo-desorbed O2 from rutile TiO2 powder. By considering the O2 photo-desorption and its effect on the surface band bending of the powder, we could explain the time dependence of the PL intensities. This explanation is supported by the experimental results. For anatase TiO2 powder, the PL intensities in air with one of the alcohols, except for methanol, did not increase linearly with t0.5, although those in vacuum and in air with methanol did increase. This inconsistency is probably due to the difference between the photocatalytic activities of anatase TiO2 powder for the alcohols. In addition, it was found that the difference between the slopes of the PL intensities of the TiO2 powders in vacuum against t0.5 corresponds to that between the purities of the powders.
Decomposition of NO by Microwave Discharge of NO/He or NO/Ar Mixtures
Authors: Tsuji Masaharu , Nakano Kousuke , Kumagae Jun , Tsuji Takeshi 
Published: September 2002

Abstract
The decomposition of NO into N2 and O2 by a continuous or pulsed microwave discharge of NO/He or NO/Ar mixtures was studied at NO and rare-gas flow rates of 2–50 and 1000 sccm, respectively. Although discharge could be maintained in the low total-pressure range of 1–350 Torr for an NO/He mixture, stable microwave discharge could be maintained in the wide total-pressure range of 1–760 Torr for an NO/Ar mixture at a microwave power of 200 W. The decomposition efficiency of NO was measured as a function of the microwave power and of the NO flow rate in a continuous mode, and as a function of the duty cycle and the pulse period in a pulse mode. The decomposition mechanism of NO in He and Ar discharges is discussed on the basis of mass spectroscopic and emission spectroscopic data.
A New Class of Star-Shaped Discotic Liquid Crystal Containing a 2, 4, 6-Triphenyl-1, 3, 5-triazine Unit as a Core
Authors: Lee Chi-Han , Yamamoto Takakazu 
Published: September 2002

Abstract
A new class of discotic liquid crystals based on 2, 4, 6-triphenyl-1, 3, 5-triazine as a core and [(4-alkoxyphen-yl)ethynyl] benzene ester as rigid arms has been synthesized by a Pd(0)/Cu(I)-catalyzed carbon–carbon coupling reaction. The obtained compounds exhibited liquid-crystalline properties.
Effects of Alkali and Alkaline Earth Metals on the Kolbe–Schmitt Reaction
Authors: Rahim Mohammad Abdur , Matsui Yoshihisa , Kosugi Yoshio 
Published: September 2002

Abstract
It was found that the carboxylations of magnesium, calcium, and barium phenoxides with carbon dioxide at 260 °C produced salicylic acid and dicarboxylic acids (4-hydroxyisophthalic acid and 2-hydroxyisophthalic acid) in very high yields (80–100%), exceeding that of the ordinary Kolbe–Schmitt reaction. The orientation (ortho/para ratio) was controlled not only by chelations of the intermediate with alkaline earth metal (Mg, Ca, Ba) ions, resulting in salicylic acid, but also by the sizes of metal ions (Rb, Cs), giving p-hydroxybenzoic acid in a much higher ratio than the widely used method with potassium or sodium phenoxide. These alkaline earth metals worked to produce 3-hydroxy-2-naphthoic acid by the reaction of 2-naphthoxide with carbon dioxide, but the yield of 6-hydroxy-2-naphthoic acid was comparable to that of 3-hydroxy-2-naphthoic acid when cesium or rubidium 2-naphthoxide was employed. Considerably high yields (∼60%) of 6-hydroxy-2-naphthoic acid, a monomer of one of the best liquid-crystal polymers, was attained by the carboxylation of cesium or rubidium 2-naphthoxide in the presence of potassium or sodium carbonate, where the alkali metal ion was supposed to increase the reactivity of the substrate. The formation of “binol” was observed in the preparation of 2-naphthoxides with metal hydroxides, especially with copper(II) ion.
Vibrational Energy Relaxation of Metalloporphyrins in a Condensed Phase Probed by Time-Resolved Resonance Raman Spectroscopy
Authors: Mizutani Yasuhisa , Kitagawa Teizo 
Published: September 2002

Abstract
Recent experimental work on vibrational energy relaxation of metalloporphyrins in a condensed phase carried out in this laboratory is summarized. The formation of a vibrationally excited photoproduct of metalloporphyrins upon (π, π*) excitation and its subsequent vibrational energy relaxation were monitored by picosecond time-resolved resonance Raman spectroscopy. Results related to intramolecular relaxation of octaethylporphyrinato nickel (NiOEP) are described. Stokes Raman bands due to a photoproduct of NiOEP instantaneously appeared upon the photoexcitation. Their intensities decayed with a time constant of ∼300 ps, which indicates an electronic relaxation from the (d, d) excited state (B1g) to the ground state (A1g), being consistent with the results of transient absorption measurements. Anti-Stokes ν4 and ν7 bands for vibrationally excited (d, d) state of NiOEP decayed with time constants of ∼10 and ∼300 ps. The former is ascribed to vibrational relaxation, while the latter corresponds to the electronic relaxation from the (d, d) excited state to the electronic ground state. While the rise of anti-Stokes ν4 intensity was instrument-limited, the rise of anti-Stokes ν7 intensity was delayed by 2.0 ± 0.4 ps, which indicates that intramolecular vibrational energy redistribution has not been completed in the subpicosecond time regime. To study the mechanism of intermolecular energy transfer, solvent dependence of the time constants of anti-Stokes kinetics was investigated using various solvents. No significant solvent dependence of the rise and decay constants was observed for NiOEP. For an iron porphyrin, we observed two phases in intermolecular energy transfer. The fast phase was insensitive to solvent and the slow phase depended on solvents. A model of classical thermal diffusion qualitatively reproduced this behavior. For myoglobin, temporal changes of the anti-Stokes Raman intensity of the ν4 and ν7 bands demonstrated immediate generation of a vibrationally excited heme upon photodissociation and subsequent decays of the excited populations, whose time constants were 1.1 ± 0.6 and 1.9 ± 0.6 ps, respectively. This direct monitoring of the cooling dynamics of the heme cofactor within the protein matrix allows the characterization of the vibrational energy flow through the protein moiety and to the water bath. For solute–solvent energy transfer process, low-frequency modes of proteins seem to be less important.
Gel Formation Analyses by Dynamic Light Scattering
Authors: Shibayama Mitsuhiro , Norisuye Tomohisa 
Published: September 2002

Abstract
A novel methodology for non-destructive and real-time determination of the gelation threshold for both chemical and physical systems has been proposed. This method i.e., a time-resolved dynamic light scattering (TRDLS) measurement, allows one not only to determine the gelation threshold but also to investigate critical dynamics near gelation threshold, mechanism of gelation, and architecture of gelling cluster. The gelation threshold was found to be characterized by (1) the appearance of a speckle pattern in the scattering intensity, (2) a power-law in the intensity–time correlation function (ICF), (3) a specific broadening of the distribution function, and (4) a noticeable suppression of the initial amplitude of ICF. All of these features originate from some unique aspects of gels: nonergodicity, frozen inhomogeneities, and divergence of connectivity correlation. As an application of these concepts, we propose four methods for determination of gelation threshold and examine their validity and usefulness for various types of gels; these include chemical gels of N-isopropylacrylamide, a gelling system of silica gel in a reaction batch, thermoreversible physical gels of poly(vinyl alcohol)–Congo Red complex, and biological gels of gelatin and globular protein.
Theory of Intermolecular Interaction
Authors: Aono Shigeyuki 
Published: September 2002

Abstract
The method of orbital interaction describing the intermolecular interaction is reformulated in terms of Green’s function. The eigen-values and eigen-vectors for individual molecules obtained by block diagonalization of the original Hamiltonian, are sufficient to predict the next step of the reaction. The polarizabilities in the ordinary perturbation treatment is also effectively used. This procedure is further clarified by defining the effective coupling. The method is applied to a molecular compound between ethylene and H2.
Syntheses, Structures and Properties of Kinetically Stabilized Distibenes and Dibismuthenes, Novel Doubly Bonded Systems between Heavier Group 15 Elements.
Authors: Sasamori Takahiro , Arai Yoshimitsu , Takeda Nobuhiro , Okazaki Renji , Furukawa Yukio , Kimura Masahiro , Nagase Shigeru , Tokitoh Norihiro 
Published: September 2002

Abstract
The first stable distibene (RSb=SbR) and dibismuthene (RBi=BiR) were successfully synthesized by taking advantage of steric protection using an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). Since it is quite difficult to investigate the reactivities of the distibene (TbtSb=SbTbt) and dibismuthene (TbtBi=BiTbt) in solution due to their extremely low solubility values, similarly overcrowded distibene and dibismuthene, BbtE=EBbt (E = Sb, Bi), with sufficiently high solubility were also synthesized using another bulky substituent, 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl group (Bbt). The crystallographic analysis and spectroscopic studies of these stable dipnictenes led to the systematic comparison of structural parameters and physical properties for all homonuclear doubly bonded systems between heavier group 15 elements. In addition to these experimentally obtained results, theoretical calculations for these doubly bonded systems also revealed the intrinsic character of dipnictenes.
Surface-Enhanced Raman Scattering of Indigo on a Stable Silver Foil Substrate Prepared by a Nitric Acid Etching Method
Authors: Min Eun Sun , Nam Sang Il , Lee Mu Sang 
Published: September 2002

Abstract
A chemical etching method with HNO3-prepared silver foils was used for a Raman study. These foils were found to exhibit a strong SERS effect. An SEM image clearly shows that spherical particles exist in an oxidized state, with diameters in the range of 200 nm for oxidized silver. SERS spectrum of Indigo was taken to illustrate the usefulness of this sample preparation technique. HNO3-roughened silver foils seemed to be more easily prepared substrate systems for SERS studies. There is a high potential that this technique can be used in studies concerning the adsorption, molecular orientation, surface reaction, and surface catalysis at room or elevated temperatures.
Ultrasonic and Volumetric Study of Binary Mixtures of Benzyl Alcohol with Amides
Authors: Ali Anwar , Nain Anil Kumar 
Published: September 2002

Abstract
The density (ρ) and ultrasonic speed (u) in binary mixtures of benzyl alcohol (BA) with formamide (FA), N-methylacetamide (NMA), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA), including those of pure liquids, were measured at 35 °C over the entire composition range. The isentropic compressibility (ks), deviations in isentropic compressibility (Δks) and ultrasonic speed (Δu) from linear dependence on the composition, excess volume (VE), apparent molar isentropic compressibility (Kφ,s) and apparent molar volume (Vφ) of amides in benzyl alcohol were calculated. The variation of these parameters with composition of the mixtures suggests that the strength of interaction (BA–FA) &lt; (BA–BA) or (FA–FA), whereas the interaction (BA-substituted amide (NMA, DMF, and DMA)) &gt; (BA–BA) or (amide–amide). Moreover, the values of Δks are found to depend on the positions of the methyl groups, while those of VE seem to depend on the number of such groups in the amide molecule.