bluuebunny/crossref_metadata_2025 huggingface dataset:
Trace Metals in Nigerian Crude Oils and Their Heavy-End Distillates
Authors: Olajire Abass A , Oderinde Rotimi A
Published: August 2006

Energy dispersive X-ray fluorescence spectroscopy was used to determine Fe, Hg, V, Cd, Pb, Mn, Ni, Zn, Cu, As, and Se in samples of crude petroleum and their heavy residual oils boiling above 387 °C (729 °F) from different oil producing companies in Nigeria. Vanadium, nickel, iron, and copper are the most abundant elements, and their concentrations ranged from 14 to 99 ppm; 5.0 to 11 ppm; 43 to 110 ppm and < 0.05 to 54 ppm respectively. Other metals, i.e. Cadmiun and manganese were observed at the 2.4 to 8.9 ppm level while mercury, zinc, lead, arsenic, and selenium are present in very low level (0—1.4 ppm). An attempt was made to establish the distribution pattern of vanadium and nickel in the crude petroleum and their heavy residual oils.
A Computational Approach to the Structure of 4-Alkoxy-4′-cyanobiphenyl in Nematic Mesophase
Authors: Ono Isamu , Kondo Shoichi
Published: August 2006

Computer simulations were carried out to study the structural properties of the nematogens, nOCB (n = 5—8). The order parameters for the individual C–H bonds in the alkoxyl chain decreased stepwise along the chain in a manner similar to that determined by NMR techniques. A small difference in the ratio of molecular length to width for the compounds studied appeared according to the flexibility in the chain. The calculated densities and anisotropies in the self-diffusion coefficients were found to decrease with increasing number of carbons in the chain.
Effects of Metal Ions on Delayed Chemiluminescence Reaction of Luminol Catalyzed by Copper(II)
Authors: Kamidate Tamio , Ishikawa Atsushi , Watanabe Hiroto , Abe Shokichi
Published: August 2006

The delay time and chemiluminescence (CL) intensity in delayed-luminol CL catalyzed by copper(II) were remarkably affected by the presence of such metal ions as Cr(III), Mn(II), Co(II), and Ni(II). The variation of the delay time could be explained in terms of the effects of the metal ions on the oxidation rate of cysteamine by Cu(II). Meanwhile, all of the metal ions reduced the CL intensity compared with that by Cu(II) alone. This result could be ascribable to a deactivation of Cu(II) by the metal ions for the decomposition of hydrogen peroxide, thus decreasing the CL emission due to the peroxidation of luminol.
Determination of the Absolute Configuration of (−)-2,2,2-(Trifluoro-1-hydroxyethyl)ferrocene
Authors: Goto Midori , Yamazaki Yoshimitsu , Uebayasi Masami
Published: August 2006

The absolute configuration of the title compound produced by the microbial reduction was determined through the anomalous dispersion effect of the iron atoms. The crystals are monoclinic, space group P21, with a = 10.046(2), b = 8.844(1), c = 12.802(2) Å, β = 95.61(1)°, V = 1132(1) Å3, Z = 4, Dc = 1.666 g cm−3. There are two independent molecules in the asymmetric unit. Both of them have the same chirality of R configuration, though their molecular conformations are different.
Epoxidation of Polyolefin by Peroxy Acid Generated in situ
Authors: Kurusu Yasuhiko , Masuyama Yoshiro , Yanagi Keita , Morinaga Hiroshi , Yamamoto Shigeharu , Makanishi Mitsunori
Published: August 2006

The epoxidation of a new type polyolefin copolymer, poly(ethylene-co-1,9-decadiene) (PED) was carried out with performic acid produced in situ from formic acid and 35% hydrogen peroxide. The reaction was performed at room temperature or at 50 °C with conversion of vinyl group in the polymer chain and high selectivity to epoxide.
Formation of Aggregates of N-Acyl-l-amino Acids in Methanol Solutions. An Origin of CD
Authors: Mizuno Kazuko , Sirato Sohichiro , Inoue Kenji , Ogura Yasushi , Isa Kimio , Shindo Yohji
Published: August 2006

CD, UV, and FT-IR measurements were carried out on methanol solutions of N-dodecanoyl-l-glutamic acid and of N-dodecanoyl-l-valine over a concentration range of 5 × 10−3—1 × 10−1 M. A large positive CD band at 212 nm and a small negative one at 240 nm were observed. The positive CD decreased along with a simultaneous increase in the negative CD upon heating. Weak absorption due to a carboxylic carbonyl was found in the wavelength region where the CD bands were observed. The IR measurements reveal that carboxylic acid dimers are formed predominantly over the concentration range studied, and that an amide group does not take part in the formation of a hydrogen bond.

The two CD bands are explained in terms of the presence of two rotational conformers about the C1–C2 bond of the carboxylic group. This conclusion differs from the assignment of the positive CD band previously reported, which was ascribed to hydrogen bonding between the C*–COOH carbonyl and NH groups.
Rotational Excitation in the N2(C3Πu) and N2+(B2Σ+u) States Produced by Electron Impact of N2
Authors: Tokue Ikuo , Wang Jundong , Ito Yoshio
Published: August 2006

Rotational state distributions of N2(C3Πu) and N2+(B2Σ+u) produced by electron impact on N2 have been measured by observing the 0–0 band of the N2(C3Πu—B3Πg) and N2+(B2Σ+u—2Σ+g) emissions, respectively. The average rotational quantum number for N2(C) decreases with increasing impact energy up to 30 eV (so-called rotational excitation), reaches a minimum, and increases with impact energy above 45 eV. The rotational excitation has been observed in formation of N2(C) for the first time. This trend indicates the importance of multipole interactions between the target N2 molecule and the incident electron.
Solution and Solid State High Resolution 13C NMR Studies on Tetraphenylchlorins
Authors: Nozawa Tsunenori , Nishimura Mitsushi , Hatano Masahiro , Sato Mitsuo
Published: August 2006

High-resolution 13C NMR spectra in solid and solution states were observed for tetraphenylchlorin (TPC), tetraphenylbacteriochlorin (TPBC), and tetraphenylisobacteriochlorin (TPIBC). Chemical-shift assignments of the 13C NMR signals for TPBC were completed by a comparison of the 1H decoupled solution 13C NMR spectra with non-decoupled and solid state ones. The absence of signal number changes by temperature in the solution 13C NMR spectra and their comparison with those of the solid state ones suggested the absence of an NH tautomerism in the chlorin ring for TPC and TPBC, indicating the predominant stability of one tautomer over the other. On the other hand, for TPIBC the presence of temperature-dependent signal number changes in the solution 13C NMR spectra were observed. The rate constants of cross polarization (CP) (TCH) and the 1H spin-lattice relaxation time in the rotating frame (T1ρH) were determined based on the dependence of the NMR magnitude on the contact time.
Cycloreversion of Aryl-Substituted Cyclobutene by Direct Photolysis and Pulse Radiolysis
Authors: Nakabayashi Kenichi , Tahara Yasuhisa , Yasuda Masahide , Shima Kensuke , Takamuku Setsuo
Published: August 2006

The cycloreversion of 1,5-diphenylbicyclo[3.2.0]hept-6-ene (1) to 1,4-diphenyl-1,3-cycloheptadiene (2) has been studied by direct photolysis and radiolysis. The γ-radiolysis of 1 in benzene gave 2 quantitatively up to a stationary state where the ratio of 1 to 2 is 0 : 100. However, no isomerization of 2 to 1 occurred. The triplet state of 2 (λmax = 380—385 nm; τ = 2.7—2.8 μs) was formed by pulse radiolysis of 1 in benzene. It has been found that cycloreversion proceeds by an adiabatic mechanism via the triplet state. On the other hand, the quantum yield for the formation of 2 by the irradiation of 254 nm light to 1 was determined to be 0.64 in hexane. The fluorescence spectra of 1 and 2 also indicated that diabatic cycloreversion occurred. The singlet and triplet energy values of 1, as well as those of 2, were estimated to be 102, 78, 75, and 40 kcal mol−1, respectively. The energy difference between the ground states of 1 and 2 was determined to be 20 kcal mol−1 from DSC measurements.
Micellization of Sodium Dodecyl Sulfate in Sodium Acetate–Acetic Acid Buffer. A Conductivity Study
Authors: Paul Babul Chandra , Ismail Kochi
Published: August 2006

Electrical conductivity of sodium dodecyl sulfate (SDS) in sodium acetate–acetic acid buffer solutions was measured as functions of concentration, temperature and pH. First and second critical micelle concentrations (cmc1 and cmc2) of these solutions were estimated. Plot of cmc1 versus pH passes through a minimum in the pH range 5.2 to 5.6. The decrease in cmc1 with increasing pH is shown to be due to the Na+ counterion and is described quantitatively by an analytical expression which also provides the value of counterion binding constant. The increasing tendency of cmc1 with increase in pH is, on the other hand, caused by the acetate co-ion. The enthalpy and standard free energy changes due to micellization of SDS were estimated. The slope of the specific conductivity versus concentration plot above cmc2 is found to decrease with increasing concentration of sodium acetate which is contrary to the trend reported in sodium chloride solution. This study has revealed the effect of the nature of co-ion on micellization.
On the Formation of Inorganic Colloid Particles
Authors: Lasic Danilo D
Published: August 2006

A qualitative model for the formation of inorganic colloidal particles is presented. The model is based on the symmetry of the complexes in solution and on the symmetry of distribution, i.e., position and orientation of the binding sites of the complexes. These factors determine the final particle shape when particles grow by crystallization, while in the case of additional secondary aggregation, it is controlled also by the factors which determine crystal habit and stability of colloidal particles. In addition, kinetic factors have to be considered also because the systems are normally driven through various phases far from themodynamic equilibrium.
Molecular Mechanics Studies on the Ligand Conformation of Chiral Ruthenium Tris(2,2′-bipyridine)-Type Complexes
Authors: Ishida Hitoshi , Hamada Taisuke , Fujishita Yu-ichi , Saito Yuri , Ohkubo Katsutoshi
Published: August 2006

Molecular mechanics (MM) calculations were performed for two chiral ligands, 4,4′-bis[R(or S)-phenylethylamino carbonyl]-2,2′-bipyridine (R(or S)-PhEtbpy) and 4,4′-bis(menthoxycarbonyl)-2,2′-bipyridine (Menbpy) by the MM2PRIME program with several new parameters. These ruthenium complexes have been already found to be efficient catalysts for photochemical and enantioselective electron transfer reactions. The bonded terms in the new parameters were determined by Hopfinger's method with molecular orbital (MO) calculations. The MO calculations were mainly performed with AM1 program, however some torsional parameters were also determined by ab initio MO methods to compare with the results derived by semi-empirical methods. The electrostatic parameters were determined with the AM1 program by using the electrostatic potential (ESP) method. To find the most stable conformation, the contour maps of the strain energy of the chiral ligands were drawn as a function of rotation of the chiral groups, and the favorable conformation obtained was supported by 1H NMR measurement. The structures of these ruthenium complexes were also discussed on the CD spectra of the complexes and the enantioselectivity of the reaction.
Dependence of Ni Corrosion with a (Li0.62K0.38)2CO3 Coating on the Temperature and Atmosphere
Authors: Ota Ken-ichiro , Kim Baek-un , Yoshitake Hideaki , Kamiya Nobuyuki
Published: August 2006

The corrosion of Ni coated with alkali carbonates was measured in a CO2/O2 atmosphere at 873—1173 K. The corrosion of Ni coated with carbonates generally obeyed a parabolic rate law under a 67% CO2–33% O2 atmosphere. The parabolic rate constant decreased with an increase in the temperature with a (Li0.62K0.38)2CO3 coating under a 67% CO2–33% O2 atmosphere. This was explained by the solubility of NiO that was formed on Ni metal during corrosion. Hot corrosion was observed several times with (Li0.62K0.38)2CO3 under low CO2 pressure at 1073 K. This hot corrosion could be explained by the dissolution/reprecipitation mechanism of the NiO scale, due to the solubility gradient in the carbonate film.
The Effects of Vapor Sorption in Polymers Observed by Positron Annihilation
Authors: Ito Yasuo , Sanchez Victor , Lopez Rafael , Fucugauchi Luz A , Tanaka Kazuhiro , Okamoto Kenichi
Published: August 2006

Positron lifetime measurements were performed for two different kinds of polymers (low density polyethylene and a polyimide 6FDA-TMPD) during sorption of various vapors (hexane, cyclohexane, benzene, acrylic acid, methyl acrylate, water, and oxygen). The vapor sorption affected the long-lived component (ortho-positronium component) in a systematic way regardless of the kind of the vapor molecules, i.e. for the polyethylene both the lifetime and the intensity of the long-lived component were enhanced, while for the polyimide they were decreased significantly. These different effects are interpreted in terms of different states of sorbed molecules in rubbery (the polyethylene) and in glassy (the polyimide) polymers.
Photovoltaic Properties of Porphyrin Thin Films Mixed with o-Chloranil
Authors: Takahashi Kohshin , Horino Kenji , Komura Teruhisa , Murata Kazuhiko
Published: August 2006

By mixing Zntpp solid with o-chloranil, the rectification and photovoltaic properties of Al/porphyrin/Au sandwich-type cell are improved (Zntpp: 5, 10, 15, 20-tetraphenylporphyrinatozinc). The improvement may be mainly attributable to an increase in the hole concentration as the majority carrier because of the electron transfer from Zntpp to o-chloranil in the ground state. In addition, by mixing H2tpp solid with o-chloranil, the short circuit photocurrent of the sandwich-type cell increases although the rectification property is hardly improved (H2tpp: 5, 10, 15, 20-tetraphenylporphyrin). The fluorescence intensity, the short circuit photocurrent and its temperature-dependence for various porphyrin solids mixed with o-chloranil are measured in order to clarify the photogeneration mechanism of charge carriers. The results suggest strongly that an exciplex formed between H2tpp and o-chloranil molecules contributes to the photogeneration of charge carriers.
Fluorescence Spectra of Pyrene and Humidity Effects on Them during the Sol-to-Gel-to-Xerogel Transitions of Mixed Silicon–Aluminum Alkoxide Systems
Authors: Fujii Tsuneo , Murayama Kei , Negishi Nobuaki , Anpo Masakazu , Winder Edmund J , Neu Donald R , Ellis Arthur B
Published: August 2006

The fluorescence spectra of pyrene of four sol systems comprising silicon and aluminum alkoxides (Si : Al = 99.4 : 0.6 ; 93.6 : 6.4; 85.9 : 14.1; and 50 : 50) have been observed during sol-to-gel-to-xerogel transitions under at relatively low concentration, on the order of 10−4 mol dm−3, uncatalyzed, and constant temperature (300 K) conditions. The influence of relative humidity on the relative intensities of pyrene monomer and excimer-like fluorescence in the four xerogel states has also been observed. In three of the four systems studied (all but Si : Al = 99.4 : 0.6), fluorescence spectra revealed that excimer concentration increased with time and reached a maximum near 55 days after which it decreased. From our data, it is apparent that the ratio of the intensity of the excimer-like fluorescence to that of the monomer fluorescence increases with relative humidity.
Charge Recombination Process in X-Ray Irradiated Pyrene-Doped Polystyrene as Studied by Optically Detected Electron Spin Resonance and Magnetic Field Dependence of the Recombination Fluorescence
Authors: Okazaki Masaharu , Tai Yutaka , Toriyama Kazumi
Published: August 2006

The ODESR spectrum and magnetic field dependence on recombination fluorescence were observed for X-ray irradiated pyrene-doped polystyrene at temperatures of 242—348 K. The ODESR intensity as a function of the pyrene concentration, 0.1—8.9 wt%, showed an unusual minimum at about 1.0%. Two phases were separated in the magnetic field dependence of the fluorescence: one was sharp and saturates at fields of over 50 mT, while the other was broad with a dip at around 60—150 mT. The cause of this dip was naturally attributed to the ST−1 level crossing. The sharp magnetic field effect also showed a minimum at around a concentration of 1.0 wt%. These novel findings have been interpreted using a recombination model modified from the previous one for pyrene-doped ethylene–propylene rubber and polyethylene. The essential points of the present model are: (1) although electron hopping within the polystyrene molecule is rapid, electron transfer at the last step of recombination between the polystyrene anion and the pyrene cation proceeds at a moderate rate; (2) the hole-transfer rate in the polymer chain is moderate; (3) electron hopping between the doped pyrene molecules is very much dependent on the concentration; (4) hole hopping between the pyrenes is inhibited.
The Role of Zinc Cations in the Conversion of Isobutane into Aromatics over Mechanical Mixtures of ZnO and H-ZSM-5
Authors: Osako Kazuaki , Nakashiro Katusmi , Ono Yoshio
Published: August 2006

Mechanical mixtures of ZnO and H-ZSM-5 show high activities and selectivities for the aromatization of isobutane. The temperature-programmed desorption spectra of ammonia and the infrared spectra of adsorbed pyridene revealed that a solid–solid ion-exchange occurs between ZnO and H-ZSM-5. The presence of Zn cations in the zeolite channels not only enhances the dehydrogenation, but also the C–C bond cleavage of isobutane. A mechanism for the activation of isobutane is proposed.
The Kinetics and Mechanism of the Reaction of Uranium(VI) with 8-Quinolinol and 8-Hydroxy-5-quinolinesulfonic Acid
Authors: Das Asim K
Published: August 2006

The kinetics of the reaction of uranium(VI) with 8-quinolinol and 8-hydroxy-5-quinolinesulfonate under the conditions of 1 : 1 chelate formation in the pH range 3.6—4.6 at different temperatures (20—30 °C) and ionic strength I = 0.1 mol dm−3 (KNO3) have been studied. A dual path mechanism involving both UO2(aq)2+ and UO2(OH)(aq)+ and the partially deprotonated ligand (LH,LH−) is consistent under the experimental conditions. The different rate constants under the condition of equilibrium have been determined. The results conform to kobs/B = k1[H+] + k2Kh;

where

K h = hydrolysis constant of UO2(aq)2+; Ka(1) = first deprotonation constant of the ligand, LH2 (charges are omitted); k1 and k2 are the second order forward rate constants of UO2(aq)2+ and UO2(OH)(aq)+ respectively and Q is the equilibrium constant of the reaction, UO22+ + LH UO2L+ + H+, where LH represents the partially deprotonated form of the ligand, 8-quinolinol and a similar reaction occurs for deprotonated 8-hydroxy-5-quinolinesulfonate (LH−). Thermodynamic parameters for each of the steps have been determined. The results have been compared with those of recent findings in the interaction of cerium(IV) and iron(III) with these ligands. UO2(aq)2+ has been argued to react through a dissociative interchange (Id) mechanism and its characteristic water exchange rate has been found as a rough estimate. Similarly for UO2(OH)(aq)+, a dissociative mechanism has been speculated.
Utilization of Adduct Formation and Masking Effect for Separation of Some Metal 4-(2-Thienyl)-4-thioxo-1,1,1-trifluoro-2-butanonates and 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedionates by Reversed Phase HPLC
Authors: Suzuki Tomohiro , Tsunoda Kin-ichi , Kawamoto Hiroshi , Akaiwa Hideo
Published: August 2006

The separation behavior of CoIII-, NiII-, CuII-, and ZnII-STTAs [4-(2-thienyl)-4-thioxo-1,1,1-trifluoro-2-butanone] and CoII-, NiII-, and CuII-TTAs [4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] in reversed phase high performance liquid chromatography was investigated when various additives were added to the mobile phase. The adduct formation or the masking effect was observed upon addition of additives. When trioctylphosphine oxide was added to the mobile phase, mutual separation of those metal chelates was especially remarkable due to the adduct formation. Moreover, the decomposition of some metal chelates in the HPLC column was also prevented by the adduct formation. On the other hand, 2,2′-bipyridyl and 1,10-phenanthroline showed the masking effect. Such effects of additives were consistent with their synergistic extraction constants in chelate extraction.
Study of Ion Transport across Amphoteric Ion-Exchange Membrane. VI. Multi-Ionic Potential, Membrane Permeability, and Ion-Sieve Effect
Authors: Kaibara Kozue , Kumagai-Ueda Kyoko , Inoue Hiroyoshi
Published: August 2006

The transport characteristics of an amphoteric ion-exchange membrane were examined by electrochemical measurements for a multi-ionic system, in which NH4Cl and tetraalkylammonium chloride (TAA·Cl) solution phases are divided by the membrane phase. Membrane permeability values were estimated for two cations, NH4+ and TAA+, and Cl−, as well as for whole cations as an averaged quantity describing the cation transport process relative to the anion transport process. The present study indicated that ion-sieve permeation characteristics, which have been demonstrated as a fundamental transport mechanism across an amphoteric ion-exchange membrane in the concentration-cell systems, still play a dominant role in the multi-ionic system. Satisfactory linear relationships of the logarithmic membrane permeabilities to NH4+, Cl−, and a series of TAA+ ions against the hydrated ionic radii of respective ions were obtained. This linear relation was not affected appreciably by the combination of electrolytes separated by the membrane. Thermodynamic analyses on the multi-ionic transport across an amphoteric ion-exchange membrane contribute to improve the selective performances of membrane materials and to survey more efficient operating conditions of the membrane processes.
Indirect Determination of Iodide Using Flame Atomic Absorption Spectrometry
Authors: Nag Jiban Kumar , Chattaraj Sarnath , Das Arabinda K
Published: August 2006

An indirect atomic absorption spectrometric determination of iodide has been proposed. The method involves the formation of chelate complex, [Cu(bptc)I], where BPTC, Hbptc = 2-benzoyl pyridine thiosemicarbazone, within a wide pH range (4.3—8.5), extraction of the complex into butyl acetate solvent and determination of copper signal by flame AAS and hence indirectly determining iodide. The method gave a linear graph upto 10. 4 μg ml−1 of iodide with a limit of detection (3σ) value of 47 ng ml−1. The proposed method was free of spectral interferences from large number of metal ions, anions, and organics. Hence it was successfully applied to iodide determination in laboratory chemicals and commercial grade salts.
Electrochemical Reactions of Dihalobis(isocyanide)nickel(II) at Platinum and Mercury Electrodes
Authors: Yamamoto Yasuhiro , Ehara Kazuko , Takahashi Katsuo
Published: August 2006

Electrochemical reactions of divalent nickel complexes, NiX2(RNC)2 (1) (X = I, Br, Cl; R = 2,6-Me2C6H3 (Xyl), 4-Br-2,6-Me2C6H2, 2,4-t-Bu2-6-MeC6H2, 2,4,6-t-Bu3C6H2) were carried out at Hg and Pt electrodes. Cyclic voltammograms (CVs) of 1 at a Pt electrode showed a quasi-reversible redox wave at ca. −0.50 V, due to two-electron reduction [(1) (1)2−]. The reduction potential of the iodide (1a) or bromide (1f) complex (R = Xyl) shifted to the positive side by ca. 0.3 V in the presence of isocyanide, due to the electrochemical reaction of NiX2(RNC)3 (X = I, Br). The chloride complex (1e) showed a similar potential in the presence or absence of isocyanide; there exists no five-coordinated complex. The CV of 1a at a Hg electrode showed a redox wave at −0.74 V, due to the redox reaction of the unsaturated species, “[Ni(RNC)2HgI2]” (4) formed from the reaction of 1a with Hg, suggesting the CE mechanism. Compound 1a had a redox potential at −0.72 V in the presence of 2,6-xylyl isocyanide, being responsible for [Ni(RNC)4HgI2]2. The bromide complex showed a similar behavior, but the chloride complex underwent a very complicated reaction. The electrochemical mechanism of NiX2(RNC)2 with or without isocyanide is discussed.
Studies on Mixed Chelates. XX. Mono- and Binuclear Nickel(II) and Copper(II) Complexes with N,N,N′,N″,N″′,N″′-Hexamethyltriethylenetetramine and β-Diketonates
Authors: Shintani Noriko , Kotaki Junko , Sone Kozo , Fukuda Yutaka
Published: August 2006

Nine mixed chelates of Ni(II) and Cu(II) with N,N,N′,N″,N″′,N″′-hexamethyltriethylenetetramine (hmtt) and β-diketonate (dike) ligands were prepared and characterized. Except for [Ni(dipm)(hmtt)]ClO4 (dipm = dipivaloylmethanate), all of them were found to be binuclear chelates: (i) [M2(dike)4(hmtt)] (M = Ni, dike = dipm,acac(acetylacetonate), tfac, or hfac(tri- or hexafluoroacetylacetonate); M = Cu, dike = hfac), (ii) [Ni2(NO3)2(dike)2(hmtt)] (dike = dipm, acac), and (iii) [Cu2(acac)2(hmtt)](ClO4)2. Although they are similar to their mononuclear analogues containing N,N,N′,N′-tetramethylethylenediamine (tmen), a number of characteristic differences exist. Though the Ni(II) chelates are only slightly solvatochromic, the Cu(II) chelates are strongly so.
Preparation and Properties of Vanadium (III) Complexes with l-Cysteinate and d-Penicillaminate
Authors: Maeda Haruyo , Kanamori Kan , Michibata Hitoshi , Konno Takumi , Okamoto Ken-ichi , Hidaka Jinsai
Published: August 2006

The coordination geometry of bis(l-cysteinato) vanadate(III) was determined by single-crystal X-ray crystallography. The vanadium(III) center coordinates octahedrally two tridentate l-cysteinate ligands via trans S, cis O, and cis N atoms. Bis(d-penicillaminato) vanadate(III) was characterized so as to adopt a similar trans(S) configuration based on its electronic spectrum. The coordination chemistry of the two complexes in solution was examined on the basis of the ligand-to-metal charge-transfer band. One of the two V(III)–S bonds of each complex is easily cleaved in solution.
Synthesis and Properties of 3-, 4-, and 5-Nitro-2-pyridinecarbaldehyde 2-pyridylhydrazones and Characterization of Their Metal Complexes
Authors: Odashima Tsugikatsu , Sakakura Kei , Kohata Katsunori , Ishii Hajime
Published: August 2006

Three hydrazones, 3-, 4-, and 5-nitro-2-pyridinecarbaldehyde 2-pyridylhydrazones, were synthesized. Their properties and reactivities with metal ions and the extraction and characteristics of the resultant complexes have been investigated and compared with one another. As a result, useful information on the molecular design of highly sensitive hydrazone reagents has been obtained.
Synthetic Utility of Amine–Cyanoborane Complexes as Reducing Agents
Authors: Das Mrinal Kanti , Maiti Pradip Kumar , Bhaumik Arpita
Published: August 2006

Investigations with amine–cyanoborane complexes as new viable reducing agents have shown that the reactivity of amine–cyanoborane complexes is highly dependent on the nature of the component amine and on the solvent used, and that the amine–cyanoborane complexes derived from primary amines are highly efficient and chemoselective reducing agents compared to those derived from secondary and tertiary amines.
Generation of β-Carbonyl Radicals from Cyclopropanol Derivatives by the Oxidation with Manganese(III) 2-Pyridinecarboxylate and Their Reactions with Electron-Rich and -Deficient Olefins
Authors: Iwasawa Nobuharu , Hayakawa Satoshi , Funahashi Masahiro , Isobe Koichi , Narasaka Koichi
Published: August 2006

Various β-carbonyl radicals are generated oxidatively from cyclopropanol derivatives by the use of manganese(III) 2-pyridinecarboxylate (Mn(pic)3). These β-carbonyl radicals react with electron-rich olefins such as conjugated silyl enol ethers, a ketene thioacetal, a ketene dithioacetal, and a vinyl ether intermolecularly to give crossed-addition products in good yield. Furthermore, the combined use of Mn(pic)3 and tributylhydridotin makes it possible to carry out the 1 : 1 addition reaction of these β-carbonyl radicals with electron-deficient olefins such as acrylonitrile, acrylaldehyde, methyl acrylate, methyl vinyl ketone, and N,N-dimethylacrylamide, and the corresponding products are obtained in moderate to good yield.
Synthesis and Inclusion Properties of Carbonyl-Bridged Analogs of Acyclic p-t-Butylphenol–Formaldehyde Oligomers
Authors: Ohba Yoshihiro , Irie Keisaku , Zhang Fu Sheng , Sone Tyo
Published: August 2006

A series of compounds in which a part or all of the methylene bridges of acyclic p-t-butylphenol–formaldehyde oligomers are replaced by C=O bridge(s) has been synthesized. The carbonyl-bridged tetramers, except for that with no methylene bridge, formed crystalline host–guest complexes with various organic compounds; those with two C=O bridges were superior regarding complexation, regardless of the position of the bridges. Exclusive guest selectivity of the tetramer with one terminal C=O bridge was observed for benzene and its methyl derivatives in a two-component system. The fully carbonyl-bridged dimer, trimer, tetramer, and pentamer had no complexing-capability. The thermal stability of benzene complexes (host : guest = 2 : 1) of the tetramers with one C=O bridge, as estimated from their thermal dissociation rates, are remarkably lower than that of the parent tetramer. Oximes derived from the tetramers with one C=O bridge were much more effective than the corresponding carbonyl-bridged ones regarding their complex-forming capability.
Spectrophotometric and Calorimetric Studies on Nickel(II) Chloro Complexes in Acetonitrile
Authors: Suzuki Honoh , Ishiguro Shin-ichi
Published: August 2006

Complexation equilibria between nickel(II) and chloride ions have been studied in acetonitrile (MeCN) by spectrophotometry and calorimetry at 25 °C. Formation of four mononuclear complexes, [NiIICln](2−n)+ (n = 1—4), has been found, and their formation constants, enthalpies and entropies have been determined. Individual electronic spectra of the complexes are obtained for both charge-transfer (CT) bands (230—350 nm) and d-d transition bands (320—840 nm). These spectra indicate coordination geometries of octahedral complexes {[Ni(MeCN)6]2+, [NiCl(MeCN)5]+, [NiCl2(MeCN)4]} and tetrahedral ones {[NiCl3(MeCN)]−, [NiCl4]2−}. The tetrachloronickelate (II) complex is less stable and the overall formation is more endothermic than the analogous copper(II) and zinc(II) complexes. For these metal systems, the overall complexation reactions are more favored and more exothermic in MeCN than in N,N-dimethylformamide (DMF), which is ascribed to the much weaker solvation toward hard metal ions in MeCN.
Footprint Catalysis. V. Substituent Effects of Template Molecules on the Catalytic Behavior of Imprinted Molecular Footprint Cavities
Authors: Shimada Toyoshi , Kurazono Ritsuko , Morihara Kensaku
Published: August 2006

“Footprint catalysts” are silica(alumina) gel catalysts with tailored substrate specificities; they are easily prepared by the present authors' molecular imprinting procedures with an appropriate template. Four footprint catalysts were newly prepared by imprinting using p-acetamido-substituted derivatives of benzenesulfonamide and benzamide as templates. They catalyzed transacylations of benzoic anhydride and 4-(acetamido)benzoic benzoic anhydride, respectively. The effects of the acetamido substituents apart from the reaction center on the substrate specificities were investigated.
N-Hydroxyamide-Containing Heterocycles. Part 2. Synthesis and Iron(III) Complex-Forming Tendency of 1-Hydroxy-2(1H)-pyrimidinone and -pyrazinone
Authors: Ohkanda Junko , Tokumitsu Takeshi , Mitsuhashi Keiryo , Katoh Akira
Published: August 2006

The reaction of N-(benzyloxy)urea with 1,1,3,3-tetraethoxypropane, 4,4-dimethoxy-2-butanone, and 2,4-pentanedione under acidic conditions gave the corresponding 1-benzyloxy-2(1H)-pyrimidinones (3 and 3′) in moderate yields. In contrast, the reaction of N-(benzyloxy)urea or N-methoxyurea with 1-phenyl-1,3-butanedione exclusively gave 3-alkoxyimino derivatives (4). 1-Benzyloxy-2(1H)-pyrazinones (9a and 9b) were synthesized via three steps starting from N-(t-butoxycarbonyl)glycine. The hydrogenation or treatment with 30% HBr in acetic acid of compounds 3c, 9a, and 9b afforded 1-hydroxy-4,6-dimethyl-2(1H)-pyrimidinone (HOPY), and 1-hydroxy- (HOPR-H), and 1-hydroxy-5,6-dimethyl-2(1H)-pyrazinone (HOPR-Me), respectively. They form 3 : 1 complexes of iron(III) with the N-hydroxyamide groups in the acidic region, but the stability constants of their iron(III) complexes are far below that of natural ferrioxamine B.
A Highly Regioselective Reaction of Allylic Acetates with Silylated Carbon Nucleophiles Directed by a Sulfenyl Group. Scope, Limitation, and Mechanistic Aspects
Authors: Kudo Kazuaki , Hashimoto Yukihiko , Houchigai Hitoshi , Hasegawa Masaki , Saigo Kazuhiko
Published: August 2006

α-(Sulfenylmethyl)allyl acetates reacted with silylated carbon nucleophiles in the presence of a catalytic amount of TMSOTf to give products substituted at the α-position of the sulfenylmethyl group in moderate to good yields with high regioselectivity. The theoretical calculation on an intermediate cationic species indicated that an episulfonium ion was a stable form; the observed regioselectivity was rationalized qualitatively on the basis of the coefficients of LUMO of the cation. Some transformations of the products were also demonstrated.
Electron-Transfer Photosensitized Oxygenation of Stilbene and Naphthalene Derivatives in the Presence of Acetate Ion. Controlling the Reaction of the Cation Radicals by Weak-Nucleophilic Salts
Authors: Yamashita Toshiaki , Tsurusako Taiji , Nakamura Nobuya , Yasuda Masahide , Shima Kensuke
Published: August 2006

The 9,10-Dicyanoanthracene (DCA)- or 9-cyanoanthracene-sensitized photooxygenation of trans-stilbene derivatives gave benzaldehyde derivatives efficiently in the presence of weak-nucleophilic salts, such as Et4NOAc and KOAc/18-crown-6 ether. The product distribution of this photooxygenation was apparently different from that of each photooxygenation in the presence of Mg(ClO4)2 and Et4NBF4 or in the absence of the salt. The DCA-sensitized photooxygenation of 2-methylnaphthalene gave phthalic acid and 4-methylphthalic acid in the presence of Et4NOAc. These products were different from the products generated from each photooxygenation in the presence of Et4NBF4 and KClO4 or in the absence of the salt. Also, such ring-oxygenation occurred in the DCA-sensitized photooxygenation of 2,3-dimethylnaphthalene and naphthalene in the presence of Et4NOAc. These photooxygenations in the presence of Et4NOAc proceeded by the addition of an acetate ion to the cation radical of the substrate generated by a photochemical electron transfer from the substrate to the sensitizer and the subsequent reaction with O2 and the related oxygen species.
Structures of New Pseudo-Peptide Antibiotics, Sperabillins
Authors: Hida Tsuneaki , Tsubotani Shigetoshi , Funabashi Yasunori , Ono Hideo , Harada Setsuo
Published: August 2006

Sperabillins, novel antibiotics, were isolated from the culture filtrate of Pseudomonas fluorescens YK-437. The structure of sperabillin A was elucidated to be 3-[[(3R,5R)-3-amino-6-[(2E,4Z)-2,4-hexadienoylamino]-5-hydroxyhexanoyl]amino]propanamidine dihydrochloride. Sperabillin B has a methyl substituent at the C-6 position of sperabillin A. Sperabillin C and D are (2E,4E)-isomers of the 2,4-hexadienoyl moiety of sperabillin A and B, respectively.
Synthetic Photochemistry. LX. One-pot Formation of Spirocyclic 3-Acetyl-2-hydroxy-2-cyclopentenone Derivatives from Methylenecycloalkanes and Methyl 2,4-Dioxopentanoate
Authors: Hatsui Toshihide , Ikeda Shin-ya , Takeshita Hitoshi
Published: August 2006

A series of proto-photocycloadducts of methyl 2,4-dioxopentanoate to methylenecycloalkanes and -alkenes spontaneously caused retro-benzilic acid rearrangement in high yields. The results are utterly different from those of sterically-crowded acyclic alkenes, with which the rearrangement occurred by thermolysis as a minor process.
Studies of the Selective O-Alkylation and Dealkylation of Flavonoids. XIV. A Convenient Method for Synthesizing 5,6,7-Trihydroxy-3-methoxyflavones from 6-Hydroxy-3,5,7-trimethoxyflavones
Authors: Horie Tokunaru , Tominaga Hideaki , Yoshida Isao , Kawamura Yasuhiko
Published: August 2006

Demethylation of 6-hydroxy-3,5,7-trimethoxyflavones and their acetates was studied and the following results were found. Demethylation of 6-hydroxy-3,4′,5,7-tetramethoxyflavone with 30% anhydrous aluminum chloride in acetonitrile afforded a mixture of 5,6-dihydroxy-3,4′,7-trimethoxyflavone and 5,6,7-trihydroxy-3,4′-dimethoxyflavone, but demethylation of its acetate formed the 5,6,7-trihydroxyflavone as a main product. The latter reaction was applicable as a general method for synthesizing 5,6,7-trihydroxy-3-methoxyflavones. On the other hand, the demethylation of 6-hydroxy-3,4′,5,7-tetramethoxyflavone with 10% anhydrous aluminum bromide in acetonitrile afforded the 5,6,7-trihydroxyflavone as a main product without cleavage of the 4′-methoxyl group and the reaction was more conveniently applicable for the synthesis of the 5,6,7-trihydroxyflavones. The method, however, was not adapted to the synthesis of the flavones with methoxyl groups adjacent to the hydroxyl group on the B ring, since the benzyloxyl group and the methoxyl group adjacent to the hydroxyl group were simultaneously cleaved under demethylating conditions. Seven 5,6,7-trihydroxy-3-methoxyflavones were synthesized by these methods and their properties were clarified.
Trityl Antimonate-Catalyzed Sequential Reactions of Epoxides with Silylated Nucleophiles. Rearrangement of Epoxides and C–C or C–O Bond Forming Nucleophilic Reaction onto the Intermediate Carbonyl Compounds
Authors: Harada Tsunehiro , Mukaiyama Teruaki
Published: August 2006

In the presence of a catalytic amount of trityl hexafluoroantimonate, sequential reactions of epoxides with silylated nucleophiles, rearrangement of epoxides and C–C or C–O bond forming nucleophilic reaction onto the intermediate carbonyl compounds, proceed smoothly to afford the corresponding products in fairly good yields by one-pot procedure. Trityl hexafluoroantimonate (5 mol %) efficiently promotes the above plural sequential reactions.
Preparation and Characterization of Tow kinds of cis-[RuCl(qn)2NO] (Hqn = 4-Methyl-, 2,4-dimetyl-, 2-ethly-, or 5-chloro-8-quinolinol), and the Photoinduced Preparation of the trans-[RuCl(qn)2NO] from the cis-Complex
Authors: Ikezawa Hidenori , Miki Eiichi , Mizumachi Kunihiko , Ishimori Tatujiro , Nagai Takashi , Tanaka Mikio
Published: August 2006

A mixture of hydrous trichloronitrosylruthenium(III) and 8-qulinolinol derivative (4-methyl-, 2,4-dimethyl-, 2-ethyl-, or 5-chloro-8-quinolinol) (mole ratio 1 : 4—5) was refluxed in ethyl alcohol in the dark to prepare two kinds of cis-type complexes, [RuCl(qn)2NO] (Hqn = 8–quinolinol derivative), cis-1 and cis-2, as major products. Using 2,4-dimethyl- or 2-ethyl-8-quinolinol, the trans complex was prepared in low yield with the cis-type complexes. The trans complex could be photochemically generated from the cis-1 complex in dichloromethane in good yield. The introduction of an alkyl group with an electrondonating nature to the 2-position in the quinolinol ring could induce the formation of the trans complex. The complexes were characterized by NMR, IR UV-vis, and field desorption mass spectrometries. From the cis-1-trans photoisomerization reaction in the presence of 15NO (15N atom % = 99), a bond rupture between Ru and NO was found to be involved in the reaction.
A Versatile Synthetic Method of 1-Alkylazulenes and Azulene by the Reactions of 3-Methoxycarbonyl-2H-cyclohepta[b]furan-2-one with in situ Generated Enamines
Authors: Yasunami Masafumi , Miyoshi Shiro , Kanegae Noriko , Takase Kahei
Published: August 2006

Methyl 3-alkylazulene-1-carboxylates were synthesized in high yields by the reaction of 3-methoxycarbonyl-2H-cyclohepta[b]furan-2-one with in situ generated morpholine enamines of aldehydes. Treatment of the esters with 100% phosphoric acid gave 1-alkylazulenes in excellent yields. Azulene was also synthesized in a good yield via methyl azulene-1-carboxylate with a modification of this method.
Optical Resolution and Absolute Configuration of anti Head-to-Head Umbelliferone Dimer
Authors: Adegawa Yutaka , Hashimoto Yukihiko , Fang Lan , Nakamura Masataka , Kinbara Kazushi , Hasegawa Masaki , Saigo Kazuhiko
Published: August 2006

(±)-anti Head-to-head umbelliferone dimer was resolved into a pair of optically active forms in good yields with high optical purity by a diastereomeric separation of two diastereomeric diamides obtained by the ring-opening addition reaction with optically pure erythro-2-amino-1,2-diphenylethanol or norephedrine, followed by hydrolysis and relactonization. The absolute configuration of the cyclobutane in (−)589-anti head-to-head umbelliferone dimer was confirmed to be (S,S,S,S) by an X-ray crystallographic analysis of the diamide derived from the (−)589-form by the ring-opening addition reaction with (S)-(−)589-1-(1-naphthyl)ethylamine. The absolute configuration of the cyclobutane in (−)589-anti head-to-head umbelliferone dimer is in agreement with that in (−)589-anti heat-to-head coumarin dimer.
Footprint Catalysis. VI. Chiral “Molecular Footprint” Catalytic Cavities Imprinted by a Chiral Template, Bis(N-benzyloxycarbonyl-l-alanyl)amine, and Their Stereoselective Catalyses
Authors: Morihara Kensaku , Kawasaki Satoko , Kofuji Miki , Shimada Toyoshi
Published: August 2006

Chiral “molecular footprint” catalytic cavities were formed on a silica(alumina) gel surface by molecular imprinting with a chiral template, bis(N-benzyloxycarbonyl-l-alanyl)amine. These cavities exhibited stereoselective catalyses in the transacylation of the corresponding substrates: l-, d-, and meso- forms of bis(benzyloxycarbonyl-alanyl) oxide.
Synthesis of 1-Substituted 1,2-Bis(trimethylsilyl)ethenes via Hydroboration of 1,2-Bis(trimethylsilyl)ethyne with Dialkylborane
Authors: Hoshi Masayuki , Masuda Yuzuru , Arase Akira
Published: August 2006

The reaction of 1,2-bis(trimethylsilyl)ethyne with a stoichiometric amount of dialkylborane proceeds to the monohydroboration stage, giving [(Z)-1,2-bis(trimethylsilyl)ethenyl]dialkylborane. In situ treatment of the above alkenylborane with iodine in the presence of aqueous sodium hydroxide provides highly pure (E)-1-alkyl-1,2-bis(trimethylsilyl)ethene whose alkyl group migrates from the boron atom. Successive treatment of [(Z)-1,2-bis(trimethylsilyl)ethenyl]dicyclohexylborane with copper(I) iodide, allyl bromide, and aqueous sodium hydroxide affords a cross-coupling product, (Z)-1,2-bis(trimethylsilyl)-1,4-pentadiene, stereoselectively. A similar cross-coupling reaction with 1-bromo-1-hexyne followed by UV irradiation affords (E)-1,2-bis(trimethylsilyl)-1-octen-3-yne stereoselectively.
Magnetic Field Effects on and Mechanism of Photoredox Reaction of Aromatic Nitro Group
Authors: Mutai Kiyoshi , Nakagaki Ryoichi , Tukada Hideyuki
Published: August 2006

Photoredox reaction mechanism of a homologous series p-O2NC6H4O(CH2)nNHPh (1) in acetonitrile and benzene is studied. The major products are p-ONC6H4O(CH2)n−1CHO (3) and aniline derived from intramolecular reaction, but the presence of minor amounts of intermolecular reaction products, p-O2NC6H4O(CH2)n−1CHO (4) and p-ONC6H4O(CH2)nNHPh (5) is confirmed in the reaction mixture. In the presence of an external magnetic field, the yield of 3 is suppressed and those of 4 and 5 are correspondingly increased, while the rates of the disappearance of 1 and of the formation of aniline remain unchanged, suggesting the presencer of biradical recombination process accompanied by intersystem crossing in a rate-determining step. On the basis of these observations, two reaction schemes are proposed. The magnetic field effects provide strong evidence for the presence of a transient species with (nitro)N(OH)–O–CHN< group generally supposed for nitro oxygen transfer process in this type photoreaction.
Molecular Design of a New Fluorescent Barbiturate Receptor. Sensitive Detection of Barbiturates through Solvent Extraction
Authors: Aoki Izuo , Kawahara Yohko , Sakaki Toru , Harada Takaaki , Shinkai Seiji
Published: August 2006

A fluorescent receptor, N,N′-bis[6-[4-(1-pyrenyl)butanamido]-2-pyridyl]isophthalamide (2), was synthesized to develop a sensitive host–guest-type sensory system for barbiturates. 2 aggregates in cyclohexane and the pyrene fluorescence in 2 almost disappeared because of aggregation-induced concentration quenching. The addition of barbital to the cyclohexane solution of 2, which induced the deaggregation of 2 through complementary complexation with barbital, increased the fluorescence intensity at 378 nm by a factor of about 70-fold. The barbiturates in water could also be sensitively detected by 2 based on a liquid (water)–liquid (cyclohexane) extraction technique. In this system, 2 was essentially selective for barbiturates and no fluorescence response was observed for guests including a hydantoin skeleton. The analogue of 2, which has the N,N′-di-(2-pyridyl) terephthalamide skeleton, was also investigated as a fluorescent receptor for dicarboxylic acids.
Multicarbonylation of Cyclopentadienyl and Cycloheptatrienyl Anions by Fe(CO)5
Authors: Nakanishi Saburo , Hirano Takehiro , Moriuma Hiroshi , Shiomi Makoto , Otsuji Yoshio , Adachi Tomohiro
Published: August 2006

The reaction of cyclopentadienyl anions with Fe(CO)5 in the presence of acyl chlorides or carboxylic anhydrides gave cyclic acyliron complexes [η5-C5H4C(OCOR)=C(OCOR)CO]Fe(CO)2 via triple carbonylation of the anions and a double acylation. The structure of [η5-C5H4C(OCOCH2CH3)=C(OCOCH2CH3)CO]Fe(CO)2 thus obtained was confirmed by the X-ray analysis. Diastereomers of indenyl derivative [η5-C9H6C(OCOCH2CH3)=C(OCOCH2CH3)CO]Fe(CO)(P(OCH3)3) were prepared by substitution of CO ligand with trimethyl phosphite and the structure of the diastereomers were characterized by NMR spectroscopy using 2D technique. Treatment of cycloheptatrienyl anion with Fe(CO)5 and acyl chloride resulted in double carbonylation to give [η5-C7H6C(OCOR)=C(OCOR)]Fe(CO)2. The mechanism of the reaction is proposed.
Synthesis and Chiroptical Properties of Optically Active Polyamides Having anti Head-to-Head Umbelliferone Dimer as a Component
Authors: Adegawa Yutaka , Fang Lan , Nakamura Masataka , Hasegawa Masaki , Saigo Kazuhiko
Published: August 2006

Optically active polyamides having 2,4-dihydroxyphenyl groups in the side chain were synthesized by the ring-opening polyaddition reaction of (−)-anti head-to-head umbelliferone dimer with diamines, such as 1,6-hexanediamine, 1,4-phenylenediamine, m-xylene-α,α′-diamine, and piperazine. Chiroptical properties of the polyamides were elucidated on the basis of their circular dichroism (CD) spectra in solution and in the film state. The polyamide having a 1,4-phenylene moiety in the diamine component existed in an ordered conformation even in a neutral DMAc solution. Moreover, the polyamides having 1,4-phenylenediamine or piperazine as a component existed in an ordered conformation in the film state. The steric repulsion and/or hydrogen bonding of the para-hydroxyl group on the phenyl group in the side chain was found to play a significant role to reveal the ordered conformations.