bluuebunny/crossref_metadata_2025 huggingface dataset:
Aluminum Chloride–Tetraalkylammonium Halide Complex as a Novel Catalyst in Friedel–Crafts Alkylation. Direct Construction of the Chroman Structure from 1,3-Diene
Authors: Matsui Makoto , Yamamoto Hisashi
Published: July 2006

Tetrabutylammonium halides were found to accelerate Lewis acid-catalyzed Friedel–Crafts alkylation when trimethylhydroquinone and myrcene were used, followed by cyclization to give the chroman compound predominantly. For tetraalkylammonium salts which have long-chain alkyls and/or bromide, iodide counter anions promote the reaction in less-polar solvents. Phosphonium halides and sulfonium halide were also effective. The tetraoctylammonium bromide–aluminum chloride complex was an effective catalyst for the initial regioselective protonation of 7,11,15-trimethyl-3-methylene-1,6-hexadecadiene to give α-tocopherol in high yield.
High-Pressure Diels–Alder Reaction of Cyclooctatetraene with Dimethyl 1,4-Dimethyl-7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate. Single Crystalline State Valence Isomerization of a syn-Tricyclo[4.2.0.02,5]octane Derivative
Authors: Takeshita Hitoshi , Mori Akira , Kato Nobuo , Kurahashi Yoichi , Ito Masahito
Published: July 2006

High-pressure Diels–Alder reaction of cyclooctatetraene with dimethyl 1,4-dimethyl-7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate afforded six products, one of which was shown to be a 2 : 2-adduct having a syn-tricyclo[4.2.0.02,5]octane framework. Upon radiation with X-rays, the tricyclooctane derivative isomerized to a cyclooctadiene derivative.
Synthetic Modification of Cotylenol. Synthesis of 3α-Cotylenyl Methyl Dithiocarbonates with Four Diastereomeric Glycol Moieties and Their Plant Growth Regulating Activity
Authors: Kato Nobuo , Okamoto Hiroaki , Takeshita Hitoshi
Published: July 2006

To confirm the role of an electronegative substituent on the C-3 position of the cotylenol framework in exhibiting the biological activity, four diastereomers at the 8,9-glycol moieties of 3α-sulfur analogs, 3α-cotylenyl methyl dithiocarbonates, were synthesized. The 8β,9α-dihydroxy compound, which had the same stereochemistry regarding the glycol moiety with natural products, revealed similar biological activity in stimulating the germination of lettuce seeds.
Different Roles of Two Consecutive Leucine Residues in a Receptor-Tethered Ligand Peptide (SFLLRNP) in Thrombin Receptor Activation
Authors: Nose Takeru , Shimohigashi Yasuyuki , Okazaki Mika , Satoh Yusuke , Costa Tommaso , Shimizu Naokata , Ogino Yoshio , Ohno Motonori
Published: July 2006

A synthetic peptide, H–Ser–Phe–Leu–Leu–Arg–Asn–Pro–NH2, which corresponds to a ligand peptide tethered to a human thrombin receptor, was able to activate the thrombin receptor with no thrombin. In order to inspect the structural requisites of two consecutive leucines (Leu-3 and Leu-4) in receptor activation, two sets of analogs with substitutions at either position 3 or 4 were synthesized and evaluated for their ability to hydrolyze phosphoinositide in human neuroblastoma SH-EP cells. The replacement of Leu-4 by Ala drastically decreased the activity of the parent peptide (only about 4% activity), while that of Leu-3 retained about 50% activity. A similar result was obtained when replaced by Gly. Substitution by Phe for Leu-3 sustained full activity. Although the Leu-4/Phe substitution exhibited a slight reduction in activity, Leu-4/Ile substitution unexpectedly diminished the activity (20%). These results suggested that two consecutive leucines have different roles in receptor activation; i.e., Leu-3 behaves something like a connection of peptide units to construct a bioactive conformation and Leu-4 acts like a structural element essential for interactions with receptors.
Synthesis of Pyrrole Derivatives Using Thioimidates
Authors: Yokoyama Masataka , Menjo Yasuhiro , Wei He , Togo Hideo
Published: July 2006

Dimethyl acetylenedicarboxylate, ethyl propiolate, nitro olefins, or 2-nitroalkyl acetates react with thioimidate in the presence of organic bases to give the corresponding pyrroles in moderate-to-good yields.
A 1H and 13C NMR Study of the Structure of Sulfur-Stabilized Lithiated Allylic Carbanions
Authors: Glendenning Lionel , Field Leslie D , Haynes Richard K
Published: July 2006

NMR studies of the solution structures of lithiated (E)-1-(t-butylthio)but-2-ene (4) and lithiated (E)-1-(phenylthio)but-2-ene (6) are reported. The structure of lithiated (E)-1-(t-butylthio)but-2-ene (4) is best described as a transoid carbanion with the allylic carbons C1, C2, and C3 having intermediate sp2–sp3 hybridization. In (4) the heteroatom and non-allylic substituent do not play any significant role in carbanion stabilization. Lithiated (E)-1-(phenylthio)but-2-ene (6) differs from (4) in that it exhibits cis geometry about the C1–C2 bond and the phenylthio group participates in helping to stabilize allylic charge. There is a discrepancy between the geometry about the C1–C2 bond in the solution and solid structures of (4) in the presence of TMEDA.
Synthesis and Structure of a Novel Cyclic Polysulfide, 2,4,6-Tris[bis(trimethylsilyl)methyl]phenyloctathionane
Authors: Takeda Nobuhiro , Tokitoh Norihiro , Imakubo Tatsuro , Goto Midori , Okazaki Renji
Published: July 2006

A novel cyclic polysulfide, octathionane TbtCHS8 (7; Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl) was synthesized by thermal reaction of the corresponding diazomethane TbtCHN2 with cyclooctasulfur (S8) in benzene in the dark. Molecular structure of 7 was determined by X-ray crystallographic analysis and the geometry of the CS8 ring was compared with that of theoretically optimized cyclononasulfur (S9). Desulfurization of 7 by triphenylphosphine afforded the corresponding pentathiane TbtCHS5.
Photoluminescence of 4,4′-Diaminobiphenyl
Authors: Rajendiran Narayanasamy , Swaminathan Meenakshisundaram
Published: July 2006

Fluorescence solvatochromic shifts of 4,4′-diaminobiphenyl (DABP) were found to be less than those of 4-aminobiphenyl and the difference mainly occured in hydrogen bonding solvents. This shows that the net effect of hydrogen bonding interactions of two amino groups is less than that of one amino group. The unusual fluorescence red-shift observed for the monocation of DABP relative to the neutral form is not because of the amino group becoming more basic, but because of a large solvent relaxation in aqueous media. As the entire molecule becomes planar upon excitation, its behavior is found to be similar to that of 2,7-diaminofluorene in the S1 state. pKa values for various prototropic reactions in the S0 and S1 states were determined and are discussed.
Photosubstitution Reactions of 4-Methyl-2-quinolinecarbonitrile with Arylalkanoic Acids. No Evidence for the External Magnetic Field Effects or Chiral Symmetry Breaking
Authors: Nakagaki Ryoichi , Takahira Osamu , Yamaoka Masaharu , Kashima Noriko
Published: July 2006

No appreciable magnetic field effects were observed on the relative quantum yield for photochemical reactions of 4-methyl-2-quinolinecarbonitrile with (R)-(−)-2-phenylpropionic, diphenylacetic, and 2,2-diphenylpropionic acids in benzene. Observed results were reasonably explained in terms of kinetic parameters which are dependent on and independent of an external magnetic field. (S)-(+)- and (R)-(−)-α-methoxyphenylacetic acids exhibit equivalent reactivity toward the excited state of 4-methyl-2-quinolinecarbonitrile in acetonitrile. No unusual phenomena were observed under well controlled conditions with sufficient repetitions.
Homogeneous Hydrogenation of Carbon Dioxide to Methanol Catalyzed by Ruthenium Cluster Anions in the Presence of Halide Anions
Authors: Tominaga Ken-ichi , Sasaki Yoshiyuki , Watanabe Taiki , Saito Masahiro
Published: July 2006

Methanol, together with methane, is formed for the first time by homogeneous hydrogenation of CO2 using a catalytic system consisting of Ru3(CO)12 and alkaline iodides in N-methylpyrrolidone (NMP) solution at 240 °C. The time course of the reaction indicates the successive formation of CO, methanol, and then methane. The FT-IR analysis of the resulting reaction solutions reveals the formation of several species of ruthenium carbonyl anion and their mutual interchanges during the reaction. A mechanism for the overall reaction is proposed, based on these results.
Determination of Chromium(III) and Chromium(VI) by Electrothermal Atomization Atomic-Absorption Spectrometry Following Coprecipitation with Gallium(III) Phosphate
Authors: Kagaya Shigehiro , Ueda Joichi
Published: July 2006

Gallium(III) phosphate coprecipitates quantitatively 0.2—7.5 μg of chromium(III) from 100 to 500 cm3 of a sample solution at pH 4.5—6.0. Although chromium(VI) is hardly coprecipitated with gallium(III) phosphate, it can be collected as chromium(III) after reduction by hydroxylamine. The calibration curve is linear from 8 to 300 ng cm−3 for chromium. The detection limit (signal/noise = 2) is 0.11 ng cm−3 of chromium(III) or chromium(VI) in 500 cm3 of the initial sample solution.
Dioxotungsten(VI) Complexes of ONO Donor Ligands and the X-Ray Crystal Structure of [WO2(o-OC6H4CH=NN=C(O)C6H5)(MeOH)]·MeOH
Authors: Maurya Mannar R , Antony Deena C , Gopinathan Sarada , Puranik Vedavati G , Tavale Sudam S , Gopinathan Changaramponnath
Published: July 2006

A general method for the preparation of dioxotungsten(VI) complexes of the type [WO2L(MeOH)] (where LH2 = the Schiff’s base derived from salicylaldehyde or o-vanillin and benzoylhydrazide, salicylhydrazide, furoylhydrazide, and isonicotinoylhydrazide) using [WO2(acac)2] (acacH = acetylacetone) as a precursor, is described. These complexes have been characterized by elemental analysis, electrical conductance, IR, electronic, and NMR spectral, electrochemical, and magnetic susceptibility measurements. The structure of [WO2(o-C6H4CH=NN=C(O)C6H5)(MeOH)]·MeOH (1a·MeOH) has been determined by single-crystal X-ray diffraction analysis. 1a·MeOH crystallizes in the space group Pbc21 with a = 6.992(2), b = 16.190(2), c = 31.390(4) Å, V = 3553.4(12) Å3, Z = 8, RF = 0.050, and Rw = 0.054. The tungsten atom has a highly distorted octahedral coordination in which anionic oxygen atoms of the tridentate ligand are mutually trans and are cis to the cis-dioxo group.
Kinetics and Mechanisms of the Vanadium(IV)-Catalyzed Oxidation of Iodide Ion in the Presence of Molecular Oxygen in an Acid Solution
Authors: Kimura Masaru , Hara Tomoko , Tsukahara Keiichi
Published: July 2006

The kinetics of the oxidation of iodide ion to iodine by molecular oxygen catalyzed by VO2+ ions were studied in sulfuric acid solutions in the dark. After an induction period during which time the I2−• radical anion forms, the rate of formation of iodine increased due to catalysis by VO2+ ions. The rate of reaction depended on the concentrations of VO2+, H+, and I−, and was independent of the ionic strength. The reaction was inhibited by either radical scavengers or the complex-forming substances of ethylenediaminetetraacetic acid and chloride ions. A chain mechanism containing I2−•/I2, VO2+/V3+, and O2/HO2• redox cycles is presented.
1,3-Dipolar Additions of a Nitrile Ylide with Carbonyl Compounds Studied by Laser Flash Photolysis of 3-(Biphenyl-4-yl)-2H-azirine
Authors: Naito Ikuo , Fujiwara Yoshihisa , Tanimoto Yoshifumi , Ishida Akito , Takamuku Setsuo
Published: July 2006

1,3-Dipolar additions of a nitrile ylide (NY) with carbonyl compounds were studied by means of the laser flash photolyses of 3-(biphenyl-4-yl)-2H-azirine in the presence of various types of carbonyl compounds: i.e. ketones, aldehydes, and esters. NY decays according to psuedo first-order kinetics. The rate constant of the 1,3-dipolar addition reaction of NY with carbonyl compound is increased with increasing the ionizing potential of the π-electron on the carbonyl double bond. NY reacts also with carbon dioxide (k = 5.3 × 105 dm3 mol−1 s−1 in acetonitrile).
Synthesis of dl-Shikonin by Vanadium(II)-Assisted Cross-Coupling and Electrooxidation of Aromatic Nuclei
Authors: Torii Sigeru , Akiyama Kouji , Yamashita Hidetoshi , Inokuchi Tsutomu
Published: July 2006

Vanadium(II)-assisted cross-coupling of 1,4,5,8-tetramethoxynaphthalene-2-carbaldehyde and 3-methyl-2-butenal was employed for introduction of the side chain of dl-shikonin. 2-(1-Hydroxy-4-methyl-3-pentenyl)-1,4,5,8-tetramethoxynaphthalene was prepared by the pinacol coupling and the subsequent palladium-catalyzed hydrogenolysis of the carbon–oxygen bond at the allylic position of the diol carbonate. Electrochemical oxidation of the 2-substituted 1,4,5,8-tetramethoxynaphthalene, followed by reductive acetylation with zinc and the subsequent electrooxidation of the resulting 5,8-diacetoxy-1,4-dimethoxynaphthalene, afforded the corresponding 5,8-diacetoxy-1,4-naphthoquinone, whose alkaline hydrolysis furnished dl-shikonin.
The Nucleophilic Substitution Reaction of p-Chloronitrobenzene with N-Substituted Cyclic Amines under High Pressure
Authors: Ibata Toshikazu , Shang Mu-Hong , Demura Tetsuo
Published: July 2006

An aromatic nucleophilic substitution (SNAr) reaction of p-chloronitrobenzene with N-substituted pyrrolidines under high pressure gave p-pyrrolidinonitrobenzene and ring-opening products through quaternary ammonium salt. The selectivity of dealkylation and ring-opening depends on the electronic and steric factors of N-substituents. The reactions with N-methylaziridine and N-methylazetidine gave ring-opening products without affording any demethylation product.
Preparation and Properties of Novel Titanio- and Zirconiosiloxane Compounds
Authors: Gunji Takahiro , Kitakatsu Tsutomu , Abe Yoshimoto
Published: July 2006

Syntheses and characterization of titaniosiloxane and zirconiosiloxane compounds were investigated. Titaniosiloxane and zirconiosiloxane compounds were prepared by the reaction of di-t-butoxymethoxysilanol [DBMS] with titanium or zirconium alkoxides.

DBMS was subjected to the reaction with bis(acetylacetonato)titanium diisopropoxide and titanium tetraisopropoxide to give titaniosiloxane compounds TS12 and TS14, respectively. Titaniosiloxane compounds were isolated by distillation or sublimation. TS12 was estimated to be cis-form from its 13C NMR spectrum in CDCl3. TS14 was stable in solution, but apt to decompose after isolation.

ZS12 and ZS14 were prepared by the reaction of DBMS with bis(acetylacetonato)zirconium diisopropoxide and zirconium tetraisopropoxide, respectively. The isolation of ZS12 and ZS14 by distillation or recrystallization was difficult because of decomposition and high solubility, and the formation of ZS12 and ZS14 was confirmed by 1H, 13C, and 29Si NMR and IR spectra.
Syntheses and Characterizations of Cyclotitanosiloxane and Cyclozirconosiloxane Compounds
Authors: Gunji Takahiro , Kasahara Takayuki , Fujii Akihiko , Abe Yoshimoto , Kawano Masaki
Published: July 2006

The syntheses and characterizations of cyclotitanosiloxane (CTS) and cyclozirconosiloxane (CZS) were investigated. CTS and CZS were synthesized by the reaction of di-t-butoxysilanediol with bis(acetylacetonato)diisopropoxidotitanium(IV) or bis(acetylacetonato)diisopropoxidozirconium(IV) in benzene. The formation of CTS and CZS was confirmed by the NMR and IR spectra and elemental analysis. The X-ray structural analysis for single crystals revealed that CTS and CZS consist of an eight-membered ring of two titano- or zirconosiloxane linkages bearing two t-butoxy groups on a silicon atom and two acetylacetonato groups on a titanium or zirconium atom.
Dianion Dialkali Metals of 2,2′,5,5′-Tetrasilabicyclopentylidene. Synthesis and Crystal Structures
Authors: Sekiguchi Akira , Ichinohe Masaaki , Kabuto Chizuko , Sakurai Hideki
Published: July 2006

The intramolecular bissilylation of 3,3,6,6,7,7,10,10-octamethyl-3,6,7,10-tetrasilacyclodecyne (4a) at 110 °C with a catalyst of Pd(OAc)2/1,1,3,3-tetramethylbutyl isocyanide under 5000 bar produced 2,2,2′,2′,5,5,5′,5′ -octamethyl-2,2′,5,5′-tetrasilabicyclopentylidene (5a). 2,2,2′,2′,5,5,5′,5′ -Octamethyl-2,2′,5,5′-tetragermabicyclopentylidene (5b) was also synthesized by the same method. The reaction of 5a with alkali metals (Li, Na, K, Rb, and Cs) in THF gave the corresponding dianion dialkali metals. The structures of 5a, (2,2,2′,2′,5,5,5′,5′-octamethyl-2,2′,5,5′-tetrasilabicyclopentylidene)bis[(tetrahydrofuran)lithium(I)] (6a), and (2,2,2′,2′,5,5,5′,5′-octamethyl-2,2′,5,5′ -tetrasilabicyclopentylidene)bis[(tetrahydrofuran)sodium(I)] (6b) were studied by X-ray crystallography as well as NMR spectroscopic means. The central anionic C–C bond is not twisted for 6a, whereas it is twisted by 17.1° for 6b.
Electrooxidative Fission of Carbon–Carbon Double Bond in a K2OsO2(OH)4/HIO4 Double Mediatory System
Authors: Tanaka Hideo , Kikuchi Ryo , Baba Masakatsu , Torii Sigeru
Published: July 2006

Electrooxidation of olefins in the presence of potassium osmate (0.04 molar amount) and periodic acid (0.5 molar amount) afforded the corresponding carbon–carbon double bond cleavage products in moderate to good yields, where the turnover number of periodic acid reached ca. 3.
Electrochemical Hydrotrifluoromethylation of Dialkyl Fumarates
Authors: Dan-oh Yasufumi , Uneyama Kenji
Published: July 2006

Dialkyl fumarates were electrochemically hydrotrifluoromethylated. The reaction was explained in terms of anodic bistrifluoromethylation and subsequent hydrolysis of one of the trifluoromethyl groups under the basic condition near cathode surface.
On the Nonradiative Decay of Individual Vibronic States
Authors: Islampour Reza , Gharanfoli Soheila
Published: July 2006

A general formulation of the nonradiative decay-rate constant of initially selected vibronic states in polyatomic molecules is developed. This method includes the effects of displacements as well as distortions of the potential-energy surfaces. The rate constant is also calculated perturbatively using the cumulant expansion technique. For a comparison of the two methods, a numerical analysis is carried out.
ESR Study of Paramagnetic Nickel Species Obtained by Reduction and Oxidation of Bis(1,3,5-triphenylformazanato)nickel(II)
Authors: Kawamura Yoshiko , Yamauchi Jun
Published: July 2006

Diamagnetic bis(1,3,5-triphenylformazanato)nickel(II) was reduced or oxidized by chemical and electrochemical methods. The paramagnetic Ni(I) and Ni(III) complexes thus obtained were studied by means of ESR spectroscopy. Ni(I) complexes formed by alkali metal reductions showed remarkable changes in their g values, depending on the kinds of alkali metal used. The change of g-values, which related to the ionic radii of the alkali metal ions, was well interpreted by the axial coordination effect due to the alkali metal ions. The electrochemical formation of the Ni(I) complex showed a solvent-dependency; the nickel(II) ion was reduced in DMF solution, but not in acetonitrile. The g-components were 2.030 for g// and 2.001 for g⊥. The relation between the two g-components gave a dx2−y2 ground state for the Ni(I) ion in the complex. Their anisotropy was very small. The Ni(II) ion oxidized by both chemical and electrochemical methods showed a dz2 ground state. The three g-components were 2.056, 2.039, and 2.000 in DMF, which are similar to those obtained from the other oxidation methods.
Synthesis and Crystal Structures of γ-Type Octamolybdates Coordinated by Chiral Lysines
Authors: Inoue Miyao , Yamase Toshihiro
Published: July 2006

The acidification of aqueous solutions containing Na2MoO4·2H2O in the presence of a chiral lysine ligand (d- and l-form) gives octamolybdates coordinating two lysine ligands, Na2[Mo8O26(d-lysH2)2]·8H2O (Mo8-d) and Na2[Mo8O26(l-lysH2)2]·8H2O (Mo8-l) (where lysH2 is 2,6-diammoniohexanoato), respectively. These two compounds crystallize with triclinic symmetry in the space group P1, the cell parameters being a = 10.782(2), b = 11.241(5), c = 10.027(2) Å, α = 93.21(2), β = 102.86(2), γ = 112.98(2)°, V = 1077(1) Å3, and Z = 1 for the Mo8-d, and a = 10.783(4), b = 11.246(3), c = 10.019(4) Å, α = 93.21(3), β = 102.75(3), γ = 112.98(2)°, V = 1077(2) Å3, and Z = 1 for Mo8-l. The X-ray crystal structures of these two species have been solved by the MITHRIL direct method and refined to R = 0.0337 and 0.0312 for Mo8-d and -l, respectively. The chiral lysine ligands are coordinated via their carboxylate-oxygen atoms at the vacant sites on the two five-coordinate molybdenum for the centrosymmetric γ-[Mo8O26]4− anion to retain their configuration with a resultant formation of optically-active octamolybdate species.
Multielement Determination of Rare Earth Elements in Coastal Seawater by Inductively Coupled Plasma Mass Spectrometry after Preconcentration Using Chelating Resin
Authors: Sawatari Hideyuki , Toda Takeshi , Saizuka Tomoo , Kimata Chisen , Itoh Akihide , Haraguchi Hiroki
Published: July 2006

Rare earth elements in coastal seawater were preconcentrated by using chelating resin in a batch method and determined simultaneously by inductively coupled plasma mass spectrometry (ICP-MS). In this procedure, matrix components (Na, K, Mg, and Ca) were eliminated to reduce matrix effects in ICP-MS analysis and rare earth elements were concentrated by a concentration factor of 100. The pH dependence of the recovery, resin amounts, amount of ammonium acetate for washing, and elution of adsorbed metals with nitric acid were examined in details to optimize the experimental conditions in sample pretreatment. All rare earth elements in coastal seawater were determined at the ppt or sub-ppt level successfully by the present analytical method.
Hydrazones Derived from Dithiamonoaza and Tetrathiamonoaza Analogs of Polyethers as Silver Ion Selective Ionophores: Syntheses, Proton-Dissociation Behaviors, and Metal Ion Complexing Properties in 1,4-Dioxane–Water Acidic Solution
Authors: Ishikawa Junichi , Sakamoto Hidefumi , Mizuno Tamao , Otomo Makoto
Published: July 2006

Cyclic and acyclic dithiamonoaza, tetrathiamonoaza, and tetrathiadiaza analogs of polyethers bearing a hydrazone moiety on nitrogen atom(s) were synthesized. Their acidity constants in 1,4-dioxane–water solution and stability constants of hydrazones derived from dithiamonoaza and tetrathiamonoaza analogs of polyethers for some heavy metal ions in same acidic media were measured spectrophotometrically. Hydrazones of cyclic and acyclic tetrathiamonoaza series had highly Ag+-selective complexability.
Low-Temperature Phosphorimetric Determination of Traces of Palladium(II) with Water-Soluble Coproporphyrin III
Authors: Endo Kazutoshi , Igarashi Shukuro
Published: July 2006

The characteristics of coproporphyrin III (Copro III) as a chelating agent, a chromogenic agent, and a luminescence agent for metal ions were studied. Copro III forms 1 : 1 complexes with Co(II), Cu(II), Mn(II), Ni(II), Pd(II), and Zn(II). Copper, palladium, and zinc complexes exhibit phosphorescence at liquid nitrogen temperature (77 K), and the intensity of the palladium complex (λPdmax = 659 nm) is 10 and 13 times larger than that of the copper and zinc complexes (λCumax = 685 nm, λZnmax = 702 nm), respectively. Based on these facts, a low-temperature phosphorimetric determination of the 10−8 mol dm−3 level of palladium was developed. The detection limit (S/N = 3 using a 150 W xenon arc lamp as a light source) was 8 × 10−9 mol dm−3, and the relative standard deviation was 2.8% for 6 × 10−7 mol dm−3 Pd(II) (7 determinations). Interference from many metal ions was avoided by selective extraction of palladium(II) as an ion-pair of the bromo complex with H2SO4-tetrabutylammonium bromide-methyl isobutyl ketone systems, followed by back extraction with acetate buffer solution (pH 5.0).
Surface Imprinting. Characterization of a Latex Resin and the Origin of the Imprinting Effect
Authors: Tsukagoshi Kazuhiko , Yu Kai Yu , Maeda Mizuo , Takagi Makoto , Miyajima Tohru
Published: July 2006

In accordance with the concept of Surface Imprinting, as proposed by the present authors, a Cu(II)-imprinted microsphere was studied in detail in order to obtain information about the origin of the imprinting effect. Unimprinted and Cu(II)-imprinted microspheres were prepared under several pH (4.0, 5.0, 5.6, or 6.0) conditions in second-step polymerization. The obtained microspheres were characterized regarding particle form, size-distribution pattern, average diameter, Cu(II) adsorption behavior, and so on. During preparation at pH 4.0—5.6 in the second-step polymerization, imprinted microspheres adsorbed Cu(II) more effectively than did unimprinted microspheres in this pH range, indicating a clear metal-imprinting effect. On the other hand, the imprinting effect was not observed during preparation at pH 6.0, because of the formation of copper(II) hydroxide precipitates. The maximum imprinting effect was provided by microspheres obtained at pH 5.6. Spectroscopic studies were made on Cu(II)-loaded microspheres. The FT-IR spectra suggested that carboxyl groups on the microsphere surface participated in the Cu(II) binding in their ionized carboxylate forms. An FE-SEM (ångstrom SEM) observation of the microsphere indicated a smooth surface structure at the 10 nm level. The collected data indicate that the origin of the imprinting effect on a Cu(II)-imprinted microsphere is the interaction between Cu(II) and the carboxylate group at the aqueous-organic interface, supporting the concept of Surface Imprinting.
Synthesis and Evaluation of Novel Crowned Coumarins as Self-Catalytic Fluorescence Reagents
Authors: Takadate Akira , Masuda Toshinobu , Murata Chiyomi , Tanaka Toshiharu , Goya Shujiro
Published: July 2006

Three coumarin reagents carrying crown-ether moieties as catalytic sites for the fluorescence derivatization of carboxylic acids were designed and synthesized. The catalytic abilities of these reagents were evaluated based on the stability constants (Ks) for complexation with metal acetates in methanol. The derivatization reactions of carboxylic acids with these reagents proceeded self-catalytically without crown-ether catalysts, and gave the corresponding coumarin esters in good yields. It was found that their reactivities significantly depended upon the metal-binding ability of the reagent molecules from kinetic treatments of the reactions. The derivatized products showed remarkably high fluorescence quantum yields of above 0.8 in methanol. These results suggested that the functionalization of reagents was a quite useful approach for the development of new-type analytical reagents.
Asymmetric Synthesis of 4-Phenyl-1,5-diazacyclooctan-2-one Using Optically Active Vinyl Sulfoxides
Authors: Itoh Nobuhiro , Matsuyama Haruo , Yoshida Masato , Kamigata Nobumasa , Iyoda Masahiko
Published: July 2006

Both enantiomers of (S)- and (R)-4-phenyl-1,5-diazacyclooctan-2-ones (7) were synthesized stereoselectively with good optical purity by the asymmetric conjugate addition of pyrazolidine to optically active vinyl sulfoxides, t-butyl (E)-2-[(R)- and (S)-p-tolylsulfinyl]cinnamates, respectively. Starting from 7, a synthesis of optically active homaline was achieved.
The Cyanation of Vinyl Halides with Alkali Cyanides Catalyzed by Nickel(0)–Phosphine Complexes Generated In Situ: Synthetic and Stereochemical Aspects
Authors: Sakakibara Yasumasa , Enami Hiroji , Ogawa Hiroshi , Fujimoto Shinpei , Kato Hiroyuki , Kunitake Katsumi , Sasaki Ken , Sakai Mutsuji
Published: July 2006

The cyanation of β-bromostyrenes catalyzed by Ni(PPh3)n, which was generated in situ from NiBr2(PPh3)2–Zn–PPh3 (Ni : Zn : P = 1: 3 : 2 molar ratio), was at first examined with various MCN (M = K, Na)-dipolar aprotic solvent systems by several procedures. The presence of excess cyanide ion inhibited the reaction. However, when the KCN–DMF system with some intermediate cyanide solubility was used, the nitriles were obtained in high yields and high stereoselectivity at 50 °C by almost all of the procedures attempted. On the contrary, the KCN–HMPA and KCN–MeCN systems with low cyanide solubilities accelerated the coupling of the halides to inhibit the cyanation, and in general the NaCN–DMF and NaCN–HMPA systems with high cyanide solubilities needed to reduce Ni(II) before adding MCN in order to make the catalytic reaction start. Vinyl halides such as 1- and 2-halo (Cl, Br)-1-alkenes, 2-bromo-2-butenes, 3-bromo-3-hexenes, and 1-chlorocyclohexene were also cyanated using suitable procedures and MCN–solvent systems to give the corresponding nitriles in high yields and fair-to-good stereoselectivities. However, with (Z)-2-ethoxy-1-bromoethene the (E)-nitrile, though its selectivity markedly varied with the reaction temperature, was obtained as the main product. The cyanation of ethyl (Z)-β-bromoacrylate and ethyl α-bromoacrylate was unsuccessful due to polymerization.
Synthesis and Positive Cooperativity in Cation Binding of New Podand Possessing Tropolonoids at Both Terminals of Oligoethylene Glycol
Authors: Kato Tadahiro , Hiraide Akira , Suda Miki , Kanbe Takuro , Nozoe Tetsuo
Published: July 2006

The oligoethylene glycol derivatives having tropolonoid moieties at both terminals were synthesized. The diethylene to pentaethylene glycol derivatives formed Zn complex in an intramolecular fashion, which extracted metal picrates from the aqueous solution. The larger cooperativity was observed in the extractions of alkaline earth metal ions as compared with those of alkaline metal ions.
Syntheses of 2-[(1S,3S)-1-Amino-3-carboxy-3-hydroxypropyl]thiazole-4-carboxylic Acid and the Tripeptide Skeleton of Nosiheptide Containing the Acid
Authors: Shin Chung-gi , Nakamura Yutaka , Yamada Yasuhiro , Yonezawa Yasuchika , Umemura Kazuyuki , Yoshimura Juji
Published: July 2006

The stereoselective synthesis of an amino acid component called Fragment D, N,O-diprotected 2-[(1S,3S)-1-amino-3-carboxy-3-hydroxypropyl]thiazole-4-carboxylic acid of a macrobicyclic peptide antibiotic nosiheptide, was achieved by two routes. The dipeptide, Fragment B-C, 2-[(Z)-1-(N,O-isopropylidene-l-threonylamino)-1-propenyl]thiazole-4-carboxylic acid was also synthesized by the thiazole ring formation from (Z)-2-(N,O-diprotected l-threonylamino)-2-butenethioamide with ethyl bromopyruvate. The coupling of two components by using a condensing agent gave the expected tripeptide 2, which is an important partial skeleton of the nosiheptide.
A Tetrameric Enkephalin Analog for the Putative Multivalent Interaction with Opioid Receptors
Authors: Kondo Michio , Kitajima Hiroshi , Yasunaga Teruo , Kodama Hiroaki , Costa Tommaso , Shimohigashi Yasuyuki
Published: July 2006

Based on increased affinity and selectivity of dimeric enkephalin analogs for opioid receptors, divalent interactions have been demonstrated between opioid peptides and receptors. To explore the receptor multivalency suggested by fluorescent microscopic studies, a novel type of tetrameric enkephalin analog was designed and synthesized. The tetrameric enkephalin comprises four [d-Ala2, Leu5]enkephalin molecules coupled with the amino groups of the gem-diamino derivative of cystine, which was derived from cysteinamide by a Hofmann-type rearrangement, causing an amide-to-amine conversion. By the reduction of the gem-cystine disulfide bond in the tetramer, two dimeric analogs with a free or p-methoxybenzyl-protected mercapto group were also prepared. The receptor binding characteristics of these tetramer and dimers for the δ and μ receptors were analyzed in an NG108-15 cell and rat-brain membranes. The affinity of the tetrameric analog for the δ receptors was about equal to that of the dimers, but 2—4-fold lower for the μ receptors. The dimers were 5—8-fold δ-selective, and, thus, the tetramer exhibited a high selectivity for the δ receptors. A divalent interaction mechanism was considered between the tetrameric ligand and the δ opioid receptors.
Allenyl(vinyl)methane Photochemistry. Photochemistry of 5-[2-(1,2-Propadienyl)-Substituted Alkylidene]-2,2-dimethyl-1,3-dioxane-4,6-diones
Authors: Tsuno Takashi , Sugiyama Kunio
Published: July 2006

The Photochemistry of 5-[2-(1,2-propadienyl)-substituted alkylidene]-2,2-dimethyl-1,3-dioxane-4,6-diones has been studied. These acylals formed an intramolecular charge-transfer (CT) complex between the 1,2-propadienyl and vinyl moieties in acetonitrile and in hexane, the direct photolyses of which gave (1-alkenylidene)cyclopropanes as the main products, and the intramolecular [2+2] cycloadducts, 3-alkylidene-2′,2′,5,5-tetramethylspiro[bicyclo[2.1.0]pentane-2,5′-[1,3]dioxane]-4′,6′-diones as minor products. The (1-alkenylidene)cyclopropanes were produced from the enol intermediate via a preferred 1,5-hydrogen transfer of a diradical, which was formed via an intramolecular CT excited state. On the other hand, the acetone-sensitized photolyses afforded mainly the intramolecular [2+2] cycloadducts. It is considered that the lowest triplet energies of these acylals in acetonitrile were estimated to lie in the range of 250—290 kJ mol−1, and that these energies were near to the values of the reported triplet energies of α,β-unsaturated esters, because the allene underwent a [2+2] cycloaddition to the triplet vinyl moiety, excited by triplet sensitization.
Photolyses of Derivatives of Naphthyl and Anthryl Phosphates and Methylphosphonates
Authors: Nakamura Mitsunobu , Sawasaki Koichi , Okamoto Yoshiki , Takamuku Setsuo
Published: July 2006

Upon UV irradiation in acetonitrile, tri-1-naphthyl phosphate and di-1-naphthyl methylphosphonate underwent intramolecular rearrangement and ipso-coupling to give 1,2′-binaphthalen-1′-ol and 1,1′-binaphthalene, respectively. In the photolyses of tris(4-methoxy-1-naphthyl) phosphate and bis(4-methoxy-1-naphthyl) methylphosphonate in methanol, 4,4′-dimethoxy-1,1′ -binaphthalene, 1′,4,4′-trimethoxy-1,2′-binaphthalene, and 2,4,4′-trimethoxy-1,1′-binaphthalene were generated. Tri-9-anthryl phosphate and di-9-anthryl methylphosphonate underwent intramolecular (4+4) photocycloaddition between two anthryl groups. The fluorescence spectra of the naphthyl derivatives had two emission bands ascribed to an intramolecular excimer and a monomer, but the fluorescence spectra of the anthryl derivatives had only a monomer emission band. These photoluminescence behaviors are closely related to the reactivities of the compounds.
Substituent Effects on Chloride Transfer Equilibrium in the Gas Phase. Intrinsic Resonance Demand of Benzyl Cation
Authors: Mishima Masaaki , Arima Kiyoshi , Inoue Hiroki , Usui Satoshi , Fujio Mizue , Tsuno Yuho
Published: July 2006

Relative chloride ion affinities of 48 carbocations have been measured by the chloride ion transfer equilibrium of benzyl chlorides in the gas phase. The substituent effects on the chloride affinity of benzyl cation have been analyzed in terms of the LArSR Eq., giving a ρ = −14.0 and an r+ = 1.29. The r+ value higher than the corresponding value of unity for the α-cumyl(2-phenyl-2-propyl) cation clearly indicates that the benzyl cation has an enhanced resonance demand in the intrinsic carbocation stability compared with that of the α-cumyl one. Most importantly, the unique r+ value of 1.29 for the gas-phase benzyl cation stability has been found to be identical with the value observed for the kc ionization process of the solvolysis of the activating substituent range of benzyl tosylates. The identity of the r  + value, which is consistent with previous observations for the relevant benzylic carbocation systems, suggests that the intramolecular charge-delocalization in the transition state of the kc solvolysis should be quite close to that of the carbocation intermediates. It is concluded that the exalted r+ value observed for the kc solvolysis of benzyl tosylates is not a correlational artifact arising as a result of the non-linearity caused by the kc–ks mechanistic transition but is due to the enhanced resonance stabilization of the benzyl cation compared with the α-cumyl cation.
Peroxidase-Catalyzed Oxidative Polymerization of Cresols to a New Family of Polyphenols
Authors: Uyama Hiroshi , Kurioka Hideharu , Sugihara Junji , Komatsu Izuru , Kobayashi Shiro
Published: July 2006

Enzymatic oxidative polymerization of cresols has been performed by using peroxidase catalyst in two types of polymerization solvent: an aqueous organic solution and a reverse micellar solution, to produce polymeric materials. Peroxidases derived from horseradish and soybean were employed as catalyst. The resulting polymers were partly soluble in DMF and DMSO, but, insoluble in water and other common organic solvents. The molecular weight of the DMF-soluble part was measured by GPC as ca. 5000. The solubility and molecular weight were dependent upon the polymerization condition and monomer structure. From IR and UV analyses, the polymer was found to be composed of a mixture of phenylene and oxyphenylene units. The polymer possessed no clear glass transition or melting points. TG analysis exhibited that the present polymers have relatively high thermal stability. The stability of the polymer from o- and m-cresols was better than that from the p-isomer. The polymer remained in around 40 weight % yield at 1000 °C under nitrogen.
The SNAr Reaction of 2,3,5,6-Tetrachloronitrobenzene with Diamines under High Pressure: Formation of Cyclization Products
Authors: Ibata Toshikazu , Zou Xin-Zhuo , Demura Tetsuo
Published: July 2006

The reaction of 2,3,5,6-tetrachloronitrobenzene with ethylenediamine under high pressure gave mainly a 1 : 1-product and a bridged 2 : 1-product by the substitution of a nitro group and/or an o-chlorine atom. The ratio of the products varied depending upon the amount of amine used. Other diamines, such as 1,4-butanediamine cis-and trans-1,2-cyclohexanediamines, m-xylylenediamine, and o-phenylenediamine, gave similar results. On the other hand, N,N′-dimethylethylenediamine and N,N′-dimethyl-1,3-propanediamine gave cyclization products through successive substitutions of an ortho-chlorine atom and a nitro group by the two methylamino groups of a molecule of diamine. N-Methylethylenediamine afforded a 1 : 1-product through the substitution of a nitro group by a primary amino group together with a cyclic 1 : 1-product through substitutions of an o-chlorine atom and a nitro group by secondary and primary amino groups, respectively.
Facile Aromatic Nucleophilic Substitutions Observed for the Triarylcarbenium Ions, [(4-YC6H4)Φ2C]+ [Φ = 2,6-(MeO)2C6H3; Y = MeO, Cl, Me2N, HO]
Authors: Wada Masanori , Watanabe Tetsuya , Natsume Satoko , Mishima Hisashi , Kirishima Katsuhiko , Erabi Tatsuo
Published: July 2006

Triarylmethanols of type (4-YC6H4)Φ2COH {Φ = 2,6-(MeO)2C6H3; Y = MeO, Cl, Me2N} were prepared. The methanol, (4-MeOC6H4)Φ2COH, reacted with acids in a variety of solvents to give the triarylcarbenium salts, [(4-MeOC6H4)Φ2C]X or [(4-HOC6H4)Φ2C]X, or 4-bis(2,6-dimethoxyphenyl)methylene-2,5-cyclohexadienone, O=C6H4=CΦ2, depending on the conditions. These carbenium salts further reacted in alcohols, ROH, to give the triarylmethanes, (4-ROC6H4)Φ2CH (R = Me, Et), where the para-substituent, MeO or HO, was substituted by the solvent, accompanied by a reduction at the central carbon. The methanol, (4-ClC6H4)Φ2COH, also reacted with acid to give the carbenium salt or the triarylmethane, depending on the conditions. While the methanol, (4-Me2NC6H4)Φ2COH, also gave the carbenium salt, [(4-Me2NC6H4)Φ2C]X, it was inert against the formation of the triarylmethane under analogous conditions. It reacted with aqueous sodium hydroxide to give O=C6H4=CΦ2 rather than the original methanol. The para-substituent of [(4-MeOC6H4)Φ2C]X was substituted by di- and monoalkylamines, RR′NH, to give [(4-RR′ NC6H4)Φ2C]X (R,R′ = Me,Me; Et,Et; Me,H; Et,H; Bu,H). While [(4-ClC6H4)Φ2C]X reacted with the dialkylamines to give [(4-RR′NC6H4)Φ2C]X, it reacted with monoalkylamines, RNH2, to give [(4-ClC6H4)Φ2C–NRH2]X. [(4-Me2NC6H4)Φ2C]X was hydrolyzed in the presence of diethylamine to give O=C6H4=CΦ2, but reacted with monoalkylamines to give RN=C6H4=CΦ2.
Fucoxanthin-Pyropheophorbide and Zeaxanthin-Pyropheophorbide Dyads as New Models for Study on Carotenoid-Chlorophyll Excited State Interactions
Authors: Osuka Atsuhiro , Shinoda Satoshi , Marumo Shinji , Yamada Hiroko , Katoh Tetzuya , Yamazaki Iwao , Nishimura Yoshinobu , Tanaka Yoshinori , Taniguchi Seiji , Okada Tadashi , Nozaki Koichi , Ohno Takeshi
Published: July 2006

Fucoxanthin-pyropheophorbide dyads, 3c and 4c, and zeaxanthin-pyropheophorbide dyads, 3d and 4d, were prepared as the first example of natural carotenoid-linked pyropheophorbide. Singlet–singlet energy transfer from carotenoid to pyropheophorbide is more efficient in fucoxanthin-pyropheophorbide dyads than the corresponding zeaxanthin-pyropheophorbide dyads, while the singlet excited state of the pyropheophorbide is quenched more strongly in the zeaxanthin-linked molecules. Marked differences in carotenoid-pyropheophorbide singlet excited-state interactions between fucoxanthin and zeaxanthin strongly suggest their different roles in vivo; antenna function for fucoxanthin and energy-dissipation for zeaxanthin. Both carotenoids similarly quench the triplet excited state of the pyropheophorbide through triplet–triplet energy transfer with rates which depend on temperature and the linkage.
Norbornadiene-Fused Heterocycles: Syntheses and Cycloaddition Reactions of 2-Aryl-4,7-dihydro-4,7-methano-2H-isoindoles and 4,7-Dihydro-4,7-methanoisobenzofuran
Authors: Kobayashi Tomoshige , Suda Hirokazu , Takase Hiroki , Iriye Ryozo , Kato Hiroshi
Published: July 2006

2-Phenyl- and 2-(p-tolyl)-4,7-dihydro-4,7-methano-2H-isoindole were synthesized by treatment of 3-(diethoxymethyl)bicyclo[2.2.1]hepta-2,5-diene-2-carbaldehyde with aniline or p-toluidine, followed by reduction with sodium borohydride and acid-catalyzed cyclization. It was concluded that the previous claim of the synthesis of methanoisoindole derivatives was incorrect. 4,7-Dihydro-4,7-methanoisobenzofuran was prepared by the reduction of the norbornadiene-monocarbaldehyde with sodium borohydride and subsequent treatment with Amberlyst-15. The p-tolylmethanoisoindole reacted with dimethyl acetylenedicarboxylate to give a novel 1 : 3 adduct. On the other hand, in the reaction of the methanoisobenzofuran with N-phenylmaleimide, spontaneous oxidation of the Diels–Alder cycloadduct took place to give exclusively its epoxide.
Interaction of Colloidal Chitin and Chlorophyll a in Ethanol–Water Mixed Solutions
Authors: Takahashi Yasuko , Watanabe Hatsumi
Published: July 2006

The interaction of colloidal chitin [a polysaccharide consisting of β-(1-4)-linked N-acetyl-d-glucosamine (GlcNAc) residues] and chlorophyll a (chl.a) in ethanol–water mixed solutions was investigated by means of vis and UV absorption spectroscopy. The observed facts and discussions are as follows: (i) In ethanol (10%)–water mixed solutions, the reaction rate for complex formation between colloidal chitin and chl.a shows an oscillatory dependence on their concentration ratio. At specific ratios of 7.4 × 1, 2, 4, 8··· of sugar units of chitin to one chl.a molecule, a host–guest complex of colloidal chitin with chl.a is produced. (ii) Another oscillatory phenomenon on the spectral bands of chl.a in the solution is also found as a function of the ethanol concentration. This phenomenon is discussed in terms of cluster formation of ethanol and water molecules in binary mixed solvents. (iii) Upon increasing the ethanol concentration, the host–guest complex of colloidal chitin with chl.a begins to collapse when the ethanol concentration in the solution exceeds a critical value up to which the hydrophilic/hydrophobic hydration equilibrium of the system is attained.
Quinolinium Dichromate Oxidation of Bicyclic Alcohols
Authors: Nongkynrih Irona , Mahanti Mahendra K
Published: July 2006

Kinetic data on the rates of quinolinium dichromate oxidation of some bicyclic alcohols are reported and discussed with reference to the factors that influence the nature of the transition state. The mechanistic pathway has been visualized via the formation of the intermediate chromic ester which undergoes decomposition to give the product. A cyclic transition state is suggested; being a Hückel-type system (4n + 2), this would be an allowed process.
ESR of the Anion Radical of 2,6-Dithioxobenzo[1,2-d:4,5-d′]bis[1,3]dithiole-4,8-dione. Observation of the Satellites of 17O, 13C, and 33S and the Second-Generation Satellites due to Both 13C and 33S in Natural Abundance
Authors: Hirayama Masatoshi , Terasaka Toshitaka , Yamashita Yoshiro , Suzuki Takanori , Miyashi Tsutomu , Usui Yoshiharu
Published: July 2006

ESR study of the anion radical produced by the reduction of the title compound (DTB-BDTD) with potassium metal in 1,2-dimethoxyethane is reported. In addition to the satellites of 17O, 13C, and 33S, the second-generation satellite lines of extremely low intensity, arising from both 13C and 33S isotopes in natural abundance, have been detected. It was found that these satellites vary markedly in line width among each component of its multiplet. This line width effect was used to determine the sign of hfs constants of these magnetic nuclei, and the resulting signs agreed well with those estimated from the spin densities obtained by the McLachlan procedure and the INDO method.
Heavy Atom Effect on 14 Group Nuclear Shielding Constant of SiX4 and CH4−nXn (X = Cl, Br, I; n = 1, 2, 3, 4)
Authors: Endo Kazunaka , Yamamoto Kyonosuke , Okada Hiroaki
Published: July 2006

A sum-over-states third-order perturbation theory using a semiempirical wavefunction parameteric method 3 was applied to 29Si and 13C nuclear magnetic shielding constants of SiX4 and CH4−nXn (X = Cl, Br, I; n = 1, 2, 3, 4), respectively. The other new spin-orbit (LS) term, σLS(A), was proposed to come from the cross term involving the halogen spin-orbit coupling, Fermi I·S interaction and the external field-(carbon or silicon) orbit interaction. The values using the MO method predicted a substantial contribution (25%) of σLS(Si or C) to the σLS(X) as already given. The results agreed fairly well with the experimental values, indicating the importance of the spin-orbit effect on the chemical shifts of molecules containing halogen heavier atoms. The dominant contribution of electronic states to the LS shifts is due to the excitations from all occupied MOs to only all vacant σ*Si(or C)–X antibonding MOs, since the Fermi interaction intervenes between the shift contributions.
Infrared Multiphoton Dissociation Mechanism of 1,2-Dichlorotrifluoroethane in a Molecular Beam
Authors: Yokoyama Atsushi , Yokoyama Keiichi , Fujisawa Ginji
Published: July 2006

The mechanism of the infrared multiphoton dissociation of the title molecule has been studied using photofragmentation translational spectroscopy. The HCl elimination and the C–Cl bond rupture occurred competitively as primary dissociation channels. The HCl elimination reaction accounts for % of the total primary dissociation yields at 16 ± 3 J cm−2. This is consistent with the branching ratio calculated by RRKM theory. A C=C bond rupture of the CF2CFCl molecules and C–Cl bond rupture of C2HF3Cl radicals were also observed as secondary photodissociation processes. The average excitation energy of the dissociating 1,2-dichlorotrifluoroethane molecules was found to be 14—36 kcal mol−1 (1 kcal mol−1 = 4.184 kJ mol−1) above the C–Cl dissociation threshold of the molecules by comparing the observed center-of-mass translational energy distribution for the C–Cl bond rupture with that calculated by Rice–Ramsperger–Kassel–Marcus (RRKM) theory.
Pulse Radiolysis of a Ruthenium(III,III) Oxo-Acetato Dinuclear Complex in Acetonitrile
Authors: Imamura Taira , Kishimoto Akira , Sumiyoshi Takashi , Takahashi Kenta , Fukumoto Tatsuma , Sasaki Yoichi
Published: July 2006

Pulse radiolysis of a ruthenium(III,III) oxo-acetato dinuclear complex, [Ru2(μ-O)(μ-CH3COO)2(pyridine)6](PF6)2 (abbr. Ru2(33)), in acetonitrile was studied. Electron-pulse irradiation of deaerated acetonitrile solutions caused one-electron reduction of Ru2(33) to form Ru2(32) by the acetonitrile radical anion, CH3CN•−, with a rate constant of 8.0 × 1010 M−1 s−1 (M−1 = dm3 mol−1) at 17 °C. In the solutions containing O2, Ru2(33) was competitively reduced by CH3CN•− and the superoxide ion, O2−, with a rate constant of 1.1 × 1010 M−1 s−1, to form Ru2(32). This was reoxidized by the peroxyl radical, •O2CH2CN, with a rate constant of 7.5 × 109 M−1 s−1 to regenerate the parent complex of Ru2(33). The reaction scheme is discussed in comparison with the results for the ruthenium(III,III,III) trinuclear complex, [Ru3(μ3-O)(μ-CH3COO)6(pyridine)3]PF6 (abbr. Ru3(333)), reported previously.