bluuebunny/crossref_metadata_2025 huggingface dataset:
State-Selected Ion-Molecule Reactions Studied by the Threshold Electron-Secondary Ion Coincidence (TESICO) Technique, Ar+(2P3/2, 2P1/2) + HCl
Authors: Fukuzumi Takahiro , Nakano Ryousuke , Okamura Satoshi , Honma Kenji , Koyano Inosuke
Published: September 2002

The reactions of Ar+ with HCl were studied for the two spin-orbit states of Ar+, 2P3/2 and 2P1/2, by the threshold electron-secondary ion coincidence (TESICO) technique. State selected relative reaction cross sections of the two product channels, hydrogen abstraction (HA) to form ArH+, and charge transfer (CT) to form HCl+, were determined at five collision energies in the range of 0.71–3.5 eV. At low collision energies, the cross sections of both channels show no substantial difference between the two spin-orbit states. At high collision energies, the cross sections for the HA channel also show no difference between the two states, whereas those for the CT channel show significant dependence on the spin-orbit state, the cross sections for Ar+(2P1/2) being always larger than those for Ar+(2P3/2). Combining these results with the coincidence time-of-flight (TOF) spectra, a direct reaction mechanism is suggested for both channels. The importance of the nonadiabatic transitions between the surfaces correlating to the Ar+ + HCl and Ar + HCl+(A2Σ) states in leading the reaction is proposed. Proton transfer follows the nonadiabatic transition for the HA channel and radiative or nonradiative transition follows for the CT channel.
Oxidative Dehydrogenation of Ethylbenzene over Sm2O3–V2O5 System
Authors: Sugunan Sankaran , Renuka Neeroli Kizhakayil
Published: September 2002

Sm2O3/V2O5 catalysts were synthesized by wet impregnation of samaria with an aqueous solution of ammonium trioxovanadate(V). The characterization of the prepared samples was carried out using EDX, XRD, FTIR and TG-DTA as well as a measurement of the surface area and pore volume. The catalysts were found to be stable up to 800 °C. Both amorphous and crystalline vanadate species were detected in the supported system. Vanadia species became anchored to the surface through an interaction with basic hydroxy groups and Lewis acid sites of the surface. Lewis acid and base sites decreased upon vanadia addition along with a concomitant enhancement of Brønsted acid sites. The oxidative dehydrogenation of ethylbenzene was carried out over Sm/V catalysts, which exhibited a styrene selectivity > 80%. The active species present in the supported system was concluded to be amorphous vanadia in tetrahedral coordination. The higher vanadia-loaded systems exhibited constant styrene selectivity, where crystalline tetraoxovanadates were predominantly formed.
Kinetics of Change in Casein Aggregation as a Result of Solvent-Induced Structural Change
Authors: Nishikawa Sadakatsu , Huang Hua , Matsumoto Chiho , Katayama Mizuho , Robinson Brian H
Published: September 2002

The stopped-flow method has been applied to a kinetic study concerning structural changes in casein aggregates in an aqueous medium. The aggregation process has been followed in aqueous solutions of α-casein, the results of which have revealed the same rate parameters as those reported previously in a mixed protein system (sodium casein). It has been found that the additions of urea and 1-propanol to aqueous solutions of sodium casein lead to a breakdown of the casein aggregates, which is monitored by the decrease in the absorbance (turbidity) of the sample. From the concentration dependence of the apparent first-order rate constant and the amplitude of the reaction, it is proposed that the rate-determining step is the departure of a single molecule (monomer) or a small aggregate from a large aggregate. The apparent first-order rate constant is 37 s-1 in the presence of 1-propanol and 0.26 s-1 for urea. Furthermore, in a mixing experiment with 1-propanol, an additional process associated with structural changes in the aggregate has been observed at longer times (monitored by an increase of absorbance), the apparent first-order rate constant being about 0.03 s-1. It is inferred that an intermediate is observed between the process of the breakdown of the aggregate which is quite stable in the presence of CaCl2, and that of the formation of another stable aggregate, which may include 1-propanol.
Linear and Nonlinear Polarizabilities of Fragmental Molecules for the Phenylacetylene Dendrimers
Authors: Nomura Yasushi , Sugishita Takashi , Narita Susumu , Shibuya Tai-ichi
Published: September 2002

Linear and nonlinear polarizabilities of small fragmental molecules for the phenylacetylene dendrimers have been calculated with the frequency-dependent moment schemes based on the sum-over-states expressions of the polarizabilities, including all of the singly-excited configurations in the semiempirical CNDO/S approximation. The smallest system, consisting of two benzene rings connected by an acetylene chain, corresponds to a molecular unit that is usually adopted in the exciton model for a theoretical analysis of the phenylacetylene dendrimers. The dependences of the polarizabilities upon the molecular size were examined. It has been shown that the linear polarizability in the static-field condition increases linearly with the number of acetylene chains (N). MO calculations of the nonlinear polarizabilities of these molecules have been carried out for the first time. The third-order polarizability in the static-field condition is shown to depend quadratically upon N, which suggests that two chromophores at a time participate in the optical process of the third-order polarization.
Toroidal Graphenes from 4-Valent Tori
Authors: Diudea Mircea V
Published: September 2002

Square tori are transformed into hexagonal and other tiling tori by several cutting procedures. The toroidal objects thus generated are optimized by a molecular mechanics procedure. The strain energy, defined as the difference between the energy of toroidal structure and the energy of its corresponding straight, open tube, is shown to decrease as the torus diameter increases, in the series 10,n of polyhex tori, up to 5000 atoms. Graph-theoretical characterization of toroidal structures including the Hosoya polynomial, Distance Degree Sequence, and Wiener index is also given.
Absolute Rate Constants of Cr2 (X 1Σg+) with O2, NH3, and C2H4 in the Gas Phase at Room Temperature
Authors: Ishikawa Yo-ichi , Ogawa Hiroshi , Iwaki Takayuki
Published: September 2002

The gas-phase reactivities of ground-state chromium dimers (Cr2 (X 1Σg+)) for three small molecules (O2, NH3, and C2H4) were investigated in a mass-flow controlled cell. The transient concentration of Cr2 (X 1Σg+, v = 0) produced by pulsed 266-nm laser photolysis of [Cr(CO)6] was monitored by a time-resolved laser-induced fluorescence (LIF) at 459.67 nm (A 1Σu+, v′′ = 0 ← X 1Σg+, v′ = 0). The pseudo-first-order decay rates of Cr2 (X 1Σg+) were observed to increase linearly with increasing O2 and NH3 pressure, giving pseudo-second-order rate constants of (2.3 ± 0.3)×10-11 cm3 molecule-1 s-1 for Cr2 + O2 and (4.3 ± 0.8)×10-13 cm3 molecule-1 s-1 for Cr2 + NH3 under 6.0-Torr total pressure with Ar buffer gas at room temperature. On the other hand, C2H4 was apparently found not to react with Cr2 (X 1Σg+) under our experimental conditions. In the Cr2 + O2 reaction, the pseudo-second-order rate constants were found to depend on the total pressure, and the limiting low-pressure rate constant was estimated to be (5.9 ± 2.5)×10-28 cm6 molecule-2 s-1.
Amperometric Sensor for Glutathione Based on a Mechanically Immobilized Cobalt Hexacyanoferrate Modified Electrode
Authors: Ravi Shankaran Dhesingh , Sriman Narayanan Sangilimuthu
Published: September 2002

A mechanically immobilized cobalt hexacyanoferrate modified electrode has been constructed. The modified electrode exhibits two reversible redox peaks in a 0.1 M NaCl medium, and can be used for the amperometric determination of glutathione. The modified electrode facilitates the catalytic oxidation of glutathione at a reduced overpotential compared with an unmodified graphite electrode. Glutathione was determined in the range of 4 × 10-5 to 5.2 × 10-4 M in 0.1 M NaCl and in 0.1 M KCl with correlation coefficients of 0.9991 and 0.9992, respectively. Relative standard deviations of 2.88% in NaCl and 3.27% in KCl were obtained for 4 × 10-4 M GSH (n = 10). The sensor exhibited excellent stability, reproducibility and immediate response, and can be used in flow-injection analysis.
Study on Estimating the Contribution to the Transfer Free Energies of Complex Ions. Part II. [Fe(CN)2n(bpy)(3-n)](2-2n)+ from Water to a Water–Ethanol Mixed Solvent
Authors: Tarui Takao
Published: September 2002

The solubilities of [Fe(bpy)3](ClO4)2, [Fe(CN)2(bpy)2], and K2[Fe(CN)4(bpy)] in ethanl–water mixed solvents were measured at 25.0 ± 0.1 °C, and the transfer free energy of each complex from water to a water–ethanol mixed solvent was calculated. From the obtained data, the transfer free energies were split into contributions from 2,2′-bipyridine-solvent, cyano ligand-solvent interaction energies, and electrostatic energies. The ratios of the contributed energy from 2,2′-bipyridine vs transfer free energy of free(non-coordinated) 2,2′-bipyridine are almost constant at about 0.6–0.75 over the whole mole fraction range; this is similar to the case of 1,10-phenanthroline, although 2,2′-bipyridine has a single bond between two pyridine rings and the configuration of non-coordinated 2,2′-bipyridine differs markedly as compared with that of the coordinated one. The contributed energy from the cyano ligand in this work is somewhat smaller than that estimated from an iron(II)–cyano-1,10-phenanthroline mixed-ligand complex system; it is considered that the weaker selective solvation of 2,2′-bipyridine than 1,10-phenanthroline affects the contribution from the neighbouring cyano ligand. That the contribution from the electrostatic energy does not agree with the expected value from the Born equation, is attributed to the difference between the local and bulk dielectric constants resulting from the strong selective solvation of 2,2′-bipyridine by ethanol, where ε and ε  w represent the dielectric constant of a mixed solvent and water, respectively.
Characterization of Dimeric (Carboxylato)copper(II) Complexes by Electron Spin Resonance Spectra. Correlation of ESR Parameters with Singlet–Triplet Energy Separations
Authors: Muto Yoneichiro , Nakashima Michio , Tokii Tadashi , Suzuki Ikuo , Ohba Shigeru , Steward Omar W , Kato Michinobu
Published: September 2002

Linear correlations with positive slopes have been found for the zero-field splitting parameters (D) and the anisotropic exchange parameters (Dex) vs the singlet–triplet separations (-2J) for [Cu2(O2CR)4(L)2] (R = F3C, FCH2, Cl3C, ClCH2, CH3, H, and C6H5CO) for a wide range of -2J values, ca. 240–650 cm-1. The values of D and Dex for benzoylformate were found to be the highest ever studied. The quality of the linear relations of -2J, Dex and D with the square of the coefficient of 2px(C) of the symmetric HOMO of the bridging carboxylate ions, coeff,2 were found to be in the order, -2J vs coeff2 > Dex vs coeff2 > D vs coeff2. A roughly linear relationship with a negative slope was found for D vs -2J for a system, [Cu2(O2CCMenPh3-n)4(L)2], in which the -2J values cover a relatively small range, ca. 320–370 cm-1.
The Aggregation of Dichlorobis(N-hexylethylenediamine)zinc(II) in Water and Water/Chloroform Mixed Solvents
Authors: Iida Masayasu , Asayama Keiko , Ohkawa Shiho
Published: September 2002

The aggregation of a surfactant metal complex, dichlorobis(N-hexylethylenediamine)zinc(II) (= [ZnCl2(hex-en)2]), was studied in such solvents as water, methanol (or water–methanol mixed), and chloroform (or water-containing chloroform). This complex was readily dissolved in water to form aggregates extensively, and was also very soluble in water-containing chloroform to give reversed-type aggregates. In dilute aqueous solutions, the complex was hydrolyzed and precipitated, while the solution was stable at concentrations above 0.25 mol kg-1 where the complex aggregates considerably. Precipitation was prevented by the addition of NaCl; this effect can be attributed to chloride-ion binding. The aggregation behavior in solutions was investigated by measuring the self-diffusion coefficients for the complex and of the vapor pressure depressions. The degrees of aggregation of the aqueous and water-containing chloroform solutions were in a similar manner at higher concentrations, although the critical concentration for aggregation in the aqueous solution was considerably smaller than in the chloroform solution. The hydration mode of this surfactant complex is discussed in comparison to the D2O longitudinal relaxations between the aqueous solutions and the water-containing chloroform solutions.
Synthesis and UV/Vis Absorption Spectra of Novel Azo Dyes Derived from Polyfluoro- and Perfluoroazobenzenes
Authors: Matsui Masaki , Funabiki Kazumasa , Shibata Katsuyoshi
Published: September 2002

Novel mono- and intermolecularly substituted, cyclized, and disazo dyes have been synthesized by the reaction of 4′-dimethylamino-2,3,4,5,6-pentafluoroazobenzene and perfluoroazobenzene with bifunctional heteroatom nucleophiles, such as 1,2-benzenedithiol, 2-aminobenzenethiol, 2-aminophenol, 1,2-ethanedithiol, ethylenediamine, and 2-aminoethanol. The kinds of bifunctional nucleophiles and the reaction conditions drastically affected the distribution of the product. The absorption maxima and the molar absorption coefficients of these dyes were observed in the range of 323–485 nm and 15000–60000 dm mol-1 cm-1, respectively.
Syntheses of Twelve-Membered Ring Titana- and Zirconasiloxane Compounds and Their Properties as Ceramic Precursor
Authors: Gunji Takahiro , Kubota Ken-ichi , Kishiki Shin-ichiro , Abe Yoshimoto
Published: September 2002

Cyclic metallasiloxanes, [(SiR1R2O)2M(acac)2O]2 (R1 = Me, R2 = OBut; R1 = R2 = OBut; R1 = OPri, R2 = OBut; M = Ti, Zr), were synthesized by the reaction of disiloxane-1,3-diols with diisopropoxidobis(2,4-pentanedionato)titanium(IV) or diisopropoxidobis(2,4-pentanedionato)zirconium(IV) in tetrahydrofuran. Cyclic titanasiloxanes and zirconasiloxanes have twelve-membered rings with the (Si–O–Si–O–Ti–O)2 linkages and (Si–O–Si–O–Zr–O)2 linkages, respectively. The pyrolysis of cyclic titanasiloxanes and zirconasiloxanes provided 2SiO2–TiO2 and 2SiO2–ZrO2 ceramics, respectively, which consist of amorphous silica and crystallized titania or zirconia.
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

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

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

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

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

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

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

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

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

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

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 > IEtOH ≥ BrEtOH ≥ ClEtOH > FEtOH for monohalogenoethanols, EtOH ≥ Cl3EtOH > Cl2EtOH ≥ ClEtOH and EtOH ≥ F3EtOH > FEtOH for polyhalogenoethanols, and PrOH > ClPrOH and i-PrOH > (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

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

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

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

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

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

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

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

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

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

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

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) < (BA–BA) or (FA–FA), whereas the interaction (BA-substituted amide (NMA, DMF, and DMA)) > (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.
Dispersion Interaction between Fluoranthene and Benzene in Cyclohexane
Authors: Enomoto Shigendo , Hasegawa Miki , Yoshinaga Tetsutaro , Hiratsuka Hiroshi , Kobayashi Michio , Okubo Jun , Hoshi Toshihiko
Published: September 2002

The electronic absorption spectra of fluoranthene (abbreviated as FA) were measured in various solvents together with the polarization spectrum with the aid of the stretched polymer film technique. The electronic structure of FA is discussed in comparison with MO calculated results. The polarization directions of the electronic transitions of FA were determined. For instance, the 404 (very weak) and 360.3 nm bands are polarized along the shorter and the longer (C2-) molecular axes, respectively. A weak van der Waals type FA–benzene complex formation was recognized in cyclohexane. The equilibrium constants for this complex formation were determined at various temperatures, e.g. K = 0.147 ± 0.03 dm3·mol-1 at 298 K. The enthalpy, entropy, and free-energy changes are estimated to be ΔH° = -5.9 ± 1.2 kJ·mol-1 (-1.4 ± 0.3 kcal·mol-1), ΔS°298 = -36 ± 1.0 J·K-1 mol-1 (-8.7 ± 0.24 cal·K-1 mol-1), and ΔG°298 = 4.7 ± 0.4 kJ·mol-1 (1.1 ± 0.1 kcal·mol-1). This ΔH° value is considerably small compared with the familiar hydrogen bonding energy, ca. -12 kJ·mol-1(-3 kcal·mol-1).
Temperature and Pressure Effects on Intermolecular Interactions in Charge Transfer Crystals of 2-(4-Methoxyphenyl)-1,4-benzoquinone and Quinhydrone
Authors: Uchida Yuki , Okabe Chie , Kishi Atsushi , Takeshita Hideyoshi , Suzuki Yoshio , Nibu Yoshinori , Shimada Ryoichi , Shimada Hiroko
Published: September 2002

Temperature and pressure effects on the Raman spectra due to the intramolecular vibrations of charge transfer crystals of 2-(4-methoxyphenyl)-1,4-benzoquinone and quinhydrone were studied. In quinhydrone crystals involving the intermolecular charge transfer and the intermolecular hydrogen bonding, the temperature- and pressure-induced frequency shifts of the intramolecular vibrations showed blue and red shifts with decreasing temperature and increasing pressure depending on the vibrational modes. In the yellow crystal of 2-(4-methoxyphenyl)-1,4-benzoquinone involving the intramolecular charge transfer, and in the red crystal involving both the intra- and intermolecular charge transfers, the frequencies of the intramolecular vibrations showed only blue shift with increasing pressure. This blue shift was larger in the yellow crystal than in the red crystal. It was also observed that phase transitions take place under 1.8 and 2.7 GPa in quinhydrone crystal and that the phase transitions take place under 1.5 and 2.5 GPa in the yellow and red crystals of 2-(4-methoxyphenyl)-1,4-benzoquinone, respectively.
Laser Trapping-Picosecond Fluorescence Microspectroscopy of Single Microdroplets under High Pressure: Droplet-Size and Pressure Effects
Authors: Kitagawa Fumihiko , Kitamura Noboru
Published: September 2002

A laser trapping picosecond fluorescence microspectroscopy system was combined with a high pressure cell to study droplet size and pressure effects on chemical phenomena in single micrometer-sized oil droplets. When a rectangular capillary tube was used as a pressure cell, single oil droplets were easily and stably trapped by a 1064-nm laser beam even under high pressure. The developed system enabled us to pressurize a sample emulsion as high as 75 MPa; such pressure was enough to induce pressure and droplet-size effects on the fluorescence dynamics of an Acridine Orange derivative (C12-AO+) in single oil droplets. In particular, droplet-size effects on the fluorescence dynamics were pronounced with an increase in static pressure. Possible origins of the pressure and droplet-size effects were discussed.
Crystalline Molecular Complexes of 1-Alkylpyridinium Bromide with Aromatic Compounds
Authors: Iimura Nahoko , Hirata Hirotaka , Ohashi Yuji
Published: September 2002

A surfactant, 1-alkylpyridinium salt, such as 1-hexadecylpyridinium bromide, formed complexes with aromatic compounds, such as phenolic derivatives and basic substances from an aqueous, alcohol, or acetone solution at low temperatures (< 10 °C). Fifteen complex crystals were obtained, of which two well-grown crystals, 1-hexadecylpyridinium/guaiacol and 1-hexadecylpyridinium/9-anthracenecarboxylic acid, were suitable for X-ray analysis. The structures, analyzed by X-rays, were shown to be very similar to each other, and have a common packing pattern, which has been observed in crystalline molecular complexes with surfactants contained as quaternary alkylammonium salts. The void space to accommodate the aromatic compounds in the 1-alkylpyridinium bromide complexes is greater than the corresponding one in the quaternary alkylammonium bromide complexes.
Laser-Induced Fluorescence Instrument for the Detection of Tropospheric OH Radicals
Authors: Matsumi Yutaka , Kono Mitsuhiko , Ichikawa Toshio , Takahashi Kenshi , Kondo Yutaka
Published: September 2002

An instrument for the measurement of troposphric OH radical concentrations using a laser-induced fluorescence technique has been developed. Ambient air is expanded through a pinhole into a low-pressure fluorescence cell and irradiated by the second harmonic of a dye laser at a high repetition rate of 1 kHz. The OH radicals are electronically excited using A2Σ+(ν′ = 0) ← X2Π (ν′′ = 0) transitions around 308 nm. The fluorescence from OH radicals is collected by a lens system and detected by a photomultiplier. The photoelectron pulses from the photomultiplier are processed by a photon-counting system. The dynode gate of the photomultiplier and counting gate systems are made to minimize the detection of the chamber and Rayleigh scattering signal. The sensitivity of the developed instrument is calibrated with two methods: one is a long-path absorption technique and the other is a titration technique with simultaneous photolysis of water vapor and oxygen. It is found that the background signal is mainly produced by after-pulse effects in the photomultiplier for the fluorescence detection with a dynode gate system. The minimum detection limit is determined to be 7.0×105 molecules cm-3 for OH radicals with a signal-to-noise ratio of 2 and a signal integration time of 60 s.
NMR Chemical Shift Methods for Binding Constant Determination of an Organic Anion and α-Cyclodextrin
Authors: Funasaki Noriaki , Ishikawa Seiji , Neya Saburo
Published: September 2002

Internal reference compounds suitable for proton chemical shift measurements of organic anions in deuterium oxide solutions are proposed and used to determine the binding constant of sodium hexane-1-sulfonate (SHS) and α-cyclodextrin (α-CD). The chemical shift of the methyl proton of sodium methyl sulfate (MeS), referred to external sodium 4,4-dimethyl-4-silapentane-1-sulfonate (DSS), changes linearly with the α-CD concentration, because of the volume magnetic susceptibility effect. The chemical shifts of the SHS methyl proton, referred to external DSS and corrected for this magnetic susceptibility effect, as well as referred to internal MeS and methanol (MeOH), provide reliable binding constants of SHS and α-CD. Therefore, MeS and MeOH are appropriate internal standards for organic anions. The present results serve not only for choosing appropriate internal references and the internal or external standard method for chemical shift measurements but also for correcting the chemical shift referred to an external standard.
Copper-Organic Coordination Polymers with Porous Structures
Authors: Wang Rui-Hu , Hong Mao-Chun , Su Wei-Ping , Liang Yu-Cang , Cao Rong , Zhao Ying-Jun , Weng Jia-Bao
Published: September 2002

Three copper coordination polymers containing organosulfur ligands ({[CuI2(bpsb)3(ClO4)](ClO4)}n (1), {[CuI2(bpsb)3Cl](ClO4)}n (2), and {[CuII(bpb)2Br](ClO4)·3dmf·MeCN}n (3) (bpsb = 1,2-bis[(2-pyrimidinyl)sulfanylmethyl]benzene, bpb = 1,2-bis[(4-pyridyl)sulfanylmethyl]benzene, dmf = N, N-dimethylformamide)) were synthesized and characterized by X-ray structural analysis. Complexes 1 and 2 have similar structures. In both, each bpsb molecule exhibits an exo-bidentate coordination fashion and bridges 3-coordinated copper(I) and 4-coordinated copper(I) through pyrimidinyl rings. Thus, six copper(I) centers, three 3-coordinated and three 4-coordinated located at two different planes alternatively, are linked by six bpsb molecules forming a crown-like nanocavity; such nanocavities make up a 2-D lamellar structure. In complex 3, each copper(II) center adopts a distorted square pyramidal coordination mode; each bpb molecule acts as an exo-bidentate ligand through coordinating to copper(II) atoms in two different directions to form a square unit with solvent molecule guests. Such square units share copper atoms and generate a single-stranded infinite 1-D chain structure.
Hydration of Polymer Complexes with Iminodiacetate-Type Chelating Resin
Authors: Yuchi Akio , Sotomura Yuka , Ueda Kaoru
Published: September 2002

Hydration of polymer complexes of divalent and trivalent metal ions with an iminodiacetate (IDA)-type chelating resin (-LNa2) was studied. The hydration numbers of [(-LH)2MII] for Ca2+ and [(-LH)3MIII] for Y3+ and La3+, which are practically the same as those of the respective aqua ions, indicate simple electrostatic interactions between the carboxylates of monoprotonated species of iminodiacetate, (-LH)-, and hydrated metal ions. In contrast, an appreciably smaller hydration number of [(-LH)3MIII] for Sc3+ than that of the aqua ion suggests involvement of the carboxylates in the coordination sphere. The difference in their interaction modes is discussed.
Crystal Structures and 166Er Mössbauer Spectra for Some β -Diketonatoerbium(III) Complexes
Authors: Wang Junhu , Takahashi Masashi , Takeda Masuo
Published: September 2002

The crystal structures and 166Er Mössbauer spectra for some β -diketonatoerbium(III) complexes have been investigated. The geometries around the Er(III) ions in [Er(dpm)3(H2O)] (1; Hdpm = 2,2,6,6-tetramethyl-3,5-heptanedione), [Er(pta)3(H2O)] (2; Hpta = 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione) and [Er2(pta)6] (3) are distorted monocapped trigonal prisms. 3 is a dimeric structure in which one of the chelating oxygen atoms of the pta ligand bridges between the Er(pta)3 fragments. The 166Er Mössbauer spectra for those β -diketonatoerbium(III) complexes show paramagnetic relaxation patterns at 12 K. The estimated relaxation time (τ) is spread out from 0.1 to 1 ns. For the seven-coordinated complexes, τ decrease among with a decrease in the Er(III)–Er(III) distance. τ for the six-coordinated complex of [Er(dpm)3] is as short as 0.4 ns in spite of having a rather long distance of Er(III)–Er(III) ions, suggesting that the τ also depends on the coordination number.