bluuebunny/crossref_metadata_2025 huggingface dataset:
[Ru(bpy)2(dppz-NH2)]2+ Complex (dppz-NH2: 7-Amino-dipyrido[3,2-a : 2′,3′-c]phenazine) as a Useful Photosensitizing Unit for the Construction of Photoinduced Energy Transfer Systems
Authors: Choi Chang-Shik , Mishra Lallan , Mutai Toshiki , Araki Koji
Published: September 2002

7-Amino-dipyrido[3,2-a : 2′,3′-c]phenazine (dppz-NH2) has a diimine coordination site, a rigid and extended π conjugation system, and a reactive amino group within the molecule, and [Ru(bpy)2(dppz-NH2)]2+ was synthesized as a useful photosensitizing unit for the construction of photoinduced energy-transfer systems. Anthraquinone, anthracene, and [Os(bpy)3]2+ derivatives having a carboxylic acid function were used as energy-accepting units, and were successfully connected to [Ru(bpy)2(dppz-NH2)]2+ through an amide bond. Electronic spectral and electrochemical studies of the resultant complexes were carried out, and it was shown that effective excited electron or energy transfer took place from the Ru(II) polypyridyl center to these units. In the case of the heterodinuclear Ru(II)/Os(II) complex, emission from the Ru(II) polypyridyl center was effectively quenched and that from the Os(II) polypyridyl center was increased compared to the reference Os(II) polyimine complex. The rate of energy transfer from the Ru(II) to the Os(II) polypyridyl center through the dppz-amide connector was estimated to be 1.0 × 108 s-1 in acetonitrile.
Magnetic Properties of Iron(III) Complexes with Photoisomerizable Ligands
Authors: Hirose Shigeyuki , Hayami Shinya , Maeda Yonezo
Published: September 2002

New spin-crossover Iron(III) complexes [Fe(salten)(trans-stpy)]BPh4·(CH3)2CO·0.5H2O 1 and [Fe(salten)(cis-stpy)]BPh42 with cis-trans photoisomerizable ligands have been synthesized and characterized, where trans-stpy is trans-4-styrylpyridine and cis-stpy cis-4-styrylpyridine, and salten denotes bis(3-salicylideneaminopropyl)amine, which is a quinquedentate Schiff base derived from the condensation of salicylaldehyde and di(3-aminopropyl)amine. The data of the variable-temperature magnetic susceptibility measurements for the complexes show that 1 and 2 exhibit spin-crossover phenomena in a solid. The spin-state transition temperature of 1 is lower than that of 2. The temperature dependencies of the Mössbauer spectra for the complexes also provide evidence that spin-state transitions between the high- and low-spin states take place, and that the rates of the spin interexchange at 298 K are faster than the inverse of the lifetime (1×10-7 s) of the Mössbauer nucleus. A temperature dependence of the UV-visible spectra suggesting spin-equilibrium in acetonitrile solution was obtained. The X-ray diffraction structures of single crystals of 1 and 2 were determined. Crystal data for 1: C60H61N4O3.5FeB, space group P1 (#2), Z = 2, a = 14.83(1), b = 17.98(1), c = 11.31(2) Å, α = 103.71(8), β = 110.60(8), γ = 94.31(7)°, V = 2702(5) Å3, R = 14.0%, Rw = 17.2%. Crystal data for 2: C57H54N4O2FeB, space group P21/n (#14), Z = 4, a = 14.823(9), b = 17.417(7), c = 18.37(1) Å, β = 95.331(8)°, V = 4722(3) Å3. The coordination cores of both complexes have trans coordination in oxygen atoms. Although light irradiation to 1 in acetonitrile brings about isomerization from trans- to cis- of styrylpyridine, the change in the spin-state of the complexes is not clear.
Syntheses, Crystal Structures, and Some Spectrochemical Properties of S-Bridged Tetranuclear Complexes with Stacking Arrangements Composed of Planar Palladium(II) Units
Authors: Yamada Yasunori , Fujisawa Kiyoshi , Okamoto Ken-ichi
Published: September 2002

The reaction of [Pd(aet)2] (aet = 2-aminoethanethiolate) with [Pd(NO3)2(diimine)] (diimine = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (dmphen)) gave a new type of S-bridged tetranuclear complex [{Pd(diimine)}2{Pd(aet)2}2]4+. The crystal structures of these complexes were determined by X-ray crystallography. In these complexes, the two intramolecular diimine moieties are aligned so as to overlap each other and the PdN2S2 planes in the {Pd(aet)2} units are almost perpendicular to those in the {Pd(diimine)} moieties. In the case of diimine = bpy and dmbpy, furthermore, the complex cations exist in the dimeric structure with a coplanar stacking arrangement, in which the diimine moieties of the two distinct complex cations are antiparallel to each other. In the case of diimine = phen and dmphen, on the other hand, the complex cations exist in the linear-chain-like structure with an alternate coplanar stacking arrangement, in which the diimine moieties of the neighboring complex cations are antiparallel to each other. All of the complexes were characterized on the basis of the electronic absorption, diffuse reflection, and 13C NMR spectra.
Enantioselective Photocyclization of Acrylanilides and N-Ethyl-N-methylbenzoylformamide in Inclusion Crystals with (R,R)-(-)-[trans]-2,3-Bis(α-hydroxydiphenylmethyl)-1,4-dioxaspiro-[4.4]nonane and -[4.5]decane. Mechanistic Study Based on X-Ray Crystal Structure Analyses
Authors: Ohba Shigeru , Hosomi Hiroyuki , Tanaka Koichi , Miyamoto Hisakazu , Toda Fumio
Published: September 2002

X-Ray structure analyses of the inclusion complexes indicated that the high stereo- and enantioselectivities in photocyclization of cyclohex-1-enecarboic acid methyl-phenyl-amide (3), N-methyl, N-{(E)-methylmethacryloyl}anilide (5), N-methyl, N-(methacryloyl)anilide (8), and N-ethyl-N-methylbenzoylformamide (10) are the result of their chiral conformations in the clathrate crystalline environment with the title chiral hosts [(-)-1 and (-)-2, respectively]. The chirality of acrylanilides and benzoylformamide can be indicated by the sign of the torsion angle in the backbone of the molecule, C-N-C(=O)-C and O=C(-Ph)-C(=O)-N, respectively. A partial single-crystal-to-single-crystal transformation of 1 : 1 complex of 10 with (-)-1 was performed by photoirradiation to observe in situ the photoproduct.
A Novel Maleic Anhydride Derivative from the Fungus Talaromyces sp. No. 10092
Authors: Yamanishi Ryo , Okada Kazuki , Tamugi Norihusa , Iwashima Makoto , Iguchi Kazuo
Published: September 2002

A new maleic anhydride derivative 1 (FR222398) was isolated from fermentations with the fungus Talaromyces sp. No. 10092. The structure of 1 was determined based on spectroscopic analysis and chemical conversion. The sodium salt of 1 exhibited a dispersant activity toward kaolin suspension.
Synthesis, Structure, and Reactions of Octakis(1,1,2-trimethylpropyl)octagermacubane
Authors: Unno Masafumi , Higuchi Koichi , Furuya Koji , Shioyama Hiroaki , Kyushin Soichiro , Goto Midori , Matsumoto Hideyuki
Published: September 2002

Octathexyloctagermacubane (1, thexyl = 1,1,2-trimethylpropyl) was synthesized by the condensation of trichlorothexylgermane with Mg/MgBr2, and structurally characterized by X-ray crystallography. As in the case of the thexyl-substituted octasilacubane, a ring-opening reaction followed by skeletal rearrangement of 1 took place with PCl5 to give endo, exo- and exo,exo-4,8-dichlorooctathexyltetracyclo[3.3.0.02,7.03,6]octagermanes. Treatment of these dichlorides with sodium afforded octagermacubane 1.
An NMR Study on the Ruthenium Complex-Catalyzed C-H/Olefin Coupling Reaction
Authors: Hiraki Katsuma , Ishimoto Takayuki , Kawano Hiroyuki
Published: September 2002

A dihydridoruthenium(II) complex, [RuH2(CO)(PPh3)3], reacts with styrene to give two species: a bis(styrene)ruthenium(0) complex, [Ru(CO)(CH2=CHPh)2(PPh3)2], and a cyclometallated hydridoruthenium(II) one, [Ru(C6H4PPh2)H(CO)(PPh3)2]. The complex [RuH2(CO)(PPh3)3] reacts with isoprene to give a piano-stool type ruthenium(0) complex [Ru(η4-CH2=CMeCH=CH2)(CO)(PPh3)2]. In reactions among [RuH2(CO)(PPh3)3], styrene, and 3′-(trifluoromethyl)acetophenone, three cyclometallated hydridoruthenium(II) complexes: P,P′-cis-C,H-cis-, P,P′-trans-C,H-trans-, and P,P′-trans-C,H-cis-[Ru{C6H3(CF3)C(=O)Me}H(CO)(PPh3)2] are detected by NMR spectroscopy. The 1H NMR spectra of the reaction mixture exhibit the catalytic formation of 2′-(2-phenylethyl)- and 2′-(1-phenylethyl)-5′-(trifluoromethyl)acetophenones. On the basis of these findings, a mechanism for the C-H/olefin coupling reaction is discussed. The first of the three complexes is assigned to an active intermediate in the catalytic coupling reaction, whereas the other two are assigned as quasi-stable ruthenium(II) complexes which are in equilibrium with active species.
Synthesis, Structure, and Properties of Hexaaryl[3]radialenes
Authors: Enomoto Tetsuya , Nishigaki Naoki , Kurata Hiroyuki , Kawase Takeshi , Oda Masaji
Published: September 2002

A number of hexaphenyl[3]radialene derivatives were synthesized in modest to good yields by the reaction of tetrachlorocyclopropene with diarylmethyl anion followed by oxidation with oxygen. That the acidity of diarylmethane is higher than that of diphenylmethane is found to be an important factor for the successful synthesis. Lithiation and protonation of hexa(4-iodophenyl)[3]radialene thus obtained leads to the first synthesis of hexaphenyl[3]radialene. These hexaaryl[3]radialenes are stable, orange to red, crystalline substances. An X-ray crystallographic analysis of hexa(4-cyanophenyl)[3]radialene reveals a double three-bladed propeller conformation. The effects of substituents in the phenyl groups on their properties are most clearly seen in their electrochemical reduction potentials; among hexaphenyl[3]radialenes here obtained, hexa (4-nitrophenyl)[3]radialene (1Ered = -0.30 V, 2Ered = -0.45 V) is found to be a good electron acceptor stronger than p-benzoquinone.
The Juliá-Colonna Asymmetric Epoxidation Reaction of Chalcone Catalyzed by Length Defined Oligo-L-leucine: Importance of the N-Terminal Functional Group and Helical Structure of the Catalyst in the Asymmetric Induction
Authors: Takagi Ryukichi , Manabe Toshiki , Shiraki Akiko , Yoneshige Arata , Hiraga Yoshikazu , Kojima Satoshi , Ohkata Katsuo
Published: September 2002

Catalysts, oligo-L-leucine, for the Juliá-Colonna asymmetric epoxidation of chalcone with defined degrees of polymerization were prepared by a stepwise elongation method. The yield and enantioselectivity in the epoxidation increased with the degree of polymerization of the catalyst. The presence of an unprotected amine moiety at the N-terminus proved to be essential for high asymmetric induction. The IR characteristic absorption bands (the amide I region) of the catalysts suggested that helical structure in the catalyst is related to asymmetric induction.
Lattice Inclusion Complexation in Water. Hydrogen Bonding in Selective Guest Binding and Catalysis
Authors: Dewa Takehisa , Saiki Toshiyuki , Imai Yuki , Endo Ken , Aoyama Yasuhiro
Published: September 2002

When immersed in an aqueous solution of alcohol or alkyl acetate as a guest, 9,10-bis(3,5-dihydroxyphenyl)anthracene 1 as a hydrogen-bonded solid host incorporates two mols of the guest together with 5—8 mols of water. The binding isotherm shows a sharp threshold guest concentration characteristic of guest-induced phase-transition. The threshold concentrations as a measure of affinities are highly dependent on the hydrophobicities of the guests. Host 1 also catalyzes the Diels-Alder reaction of acrylaldehyde and 1,3-cyclohexadiene in an aqueous environment. The preserved 1 : 2 (host-to-guest) stoichiometry, spectroscopic evidence (ΔνC=O), guest-desorption behaviors, and X-ray powder-diffraction studies indicate that host-guest hydrogen-bonding in collaboration with apolar interactions is responsible for the selective guest-binding and catalysis under the present aqueous conditions.
Synthesis and Reduction of Silyl-Substituted [5]Radialene. Characterization and Structure of a [5]Radialene Tetraanion with a Ten-Center, Fourteen-Electron π-System
Authors: Matsuo Tsukasa , Fure Hidetoshi , Sekiguchi Akira
Published: September 2002

The reaction of 3,3,6,6,8,8,11,11,14,14,16,16,19,19,21,21-hexadecamethyl-3,6,8,11,14,16,19,21-octasilacyclohenicosa-1,4,9,12,17-pentayne with an excess molar amount of [Mn(CO)3(Me-Cp)] in tetrahydrofuran (THF) under photochemical and refluxing conditions produced 2,2,4,4,9,9,11,11,13,13,15,15,17,17,21,21-hexadecamehyl-2,4,9,11,13,15,17,21-octasilahexacyclo[10.5.3.15,8.06,18.07,20.014,19]henicosa-1(18),5,7,12(20),14(19)-pentaene (2) as silyl-substituted [5]radialene derivative. This was reacted with lithium metal in THF to give dark red crystals of the tetralithium salt (4) of 2. The molecular structure of tetraanion of 2 with a novel ten-center, fourteen-electron π-system was established by X-ray crystallography. The tetralithium salt 4 has a monomeric structure and forms contact ion pairs (tetrakis-CIPs) in the crystals. The structural parameters of 4 are discussed in comparison with those of the neutral starting molecule 2. The structure of 4 in solution is also discussed on the basis of NMR spectroscopic data.
Reaction of Trialkyl(dibromomethyl)silanes or 1,2-Bis(dibromomethyl)benzene with Triorganomanganates. A Facile and Selective Synthesis of Alkenylsilanes and 1,2-Diaryl-1,2-dihydrobenzocyclobutenes
Authors: Kakiya Hirotada , Shinokubo Hiroshi , Oshima Koichiro
Published: September 2002

Treatment of trialkyl(dibromomethyl)silanes with trialkylmanganates, derived from manganese(II) chloride and three molar amounts of Grignard reagents or alkyllithiums, provided (E)-1-trialkylsilyl-1-alkenes with high stereoselectivity in good yields. The reaction of trialkyl(dibromomethyl)silanes with alkylmagnesium halides proceeded in the presence of a catalytic amount of manganese(II) chloride. Treatment of 1,2-bis(dibromomethyl)benzene with triphenylmanganate gave 1,2-diphenyl-1,2-dihydrobenzocyclobutene.
Palladium(II)-Catalyzed Michael-Type Addition Reactions Using Aryltin Compounds
Authors: Ohe Toshiyuki , Wakita Takeshi , Motofusa Shin-ichi , Cho Chan Sik , Ohe Kouichi , Uemura Sakae
Published: September 2002

A variety of aryltin compounds can be employed for Michael-type hydroarylation reactions to α,β-unsaturated ketones and aldehydes in the presence of a catalytic amount of palladium(II) salt in acetic acid under air. Each reaction is much accelerated in the presence of a soluble metal chloride such as LiCl, MgCl2, and CaCl2. It is found that slightly fewer than four aryl groups of tetraaryltins can be transferred to the products in this arylation.
Synthesis of Ladder and Cage Silsesquioxanes from 1,2,3,4-Tetrahydroxycyclotetrasiloxane
Authors: Unno Masafumi , Suto Akiko , Takada Keisuke , Matsumoto Hideyuki
Published: September 2002

The versatility of cis,cis,cis-1,3,5,7-tetrahydroxy-1,3,5,7-tetraisopropylcyclotetrasiloxane (1) as a precursor of cage and ladder siloxanes is presented. Compound 1 reacted with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane in pyridine to give 1,3,5,5,7,7,9,11,13,13,15,15-cis-cisoid-cis-dodecaisopropyltricyclo[9.5.1.13,9]octasiloxane (2) in 20% yield. The reaction proceeded with retention of the configuration of the silicon atoms, and only syn-type isomer was obtained. The reaction of 1 with 1,1,3,3-tetrachloro-1,3-diisopropyldisiloxane in pyridine produced hexakis(isopropylsilsesquioxane) (T6) (3) in 25% yield. Treatment of 1 with dicyclohexylcarbodiimide (DCC) as dehydrating reagent led to the formation of octakis(isopropylsilsesquioxane) (T8) (4) in 45% yield. The crystal structures of 2, 3, and 4 are reported.
Separation of Orientational Disorder in the X-Ray Analysis of the Kinetically Stabilized 2-Silanaphthalene
Authors: Wakita Keiji , Tokitoh Norihiro , Okazaki Renji
Published: September 2002

The crystal structure of the stable 2-silanaphthalene was refined more adequately by the separation of the disorder of overlapped two 2-silanaphthalene moieties. The bond lengths of the 2-silanaphthalene ring were in fairly good agreement with the theoretically calculated values which we previously reported.
Trialkylmanganate Mediated Radical Addition of Triphenylgermane to Carbon-Carbon Multiple Bonds
Authors: Kinoshita Hidenori , Kakiya Hirotada , Oshima Koichiro
Published: September 2002

Treatment of 1-dodecyne with triphenylgermane in the presence of catalytic amounts of tributylmanganate at 25 °C provided 1-triphenylgermyl-1-dodecene in good yield. The reaction proceeded in a radical pathway and treatment of diene afforded the corresponding radical cyclization product.
A Universal Structural Model for Human Hair to Understand the Physical Properties 1
Authors: Nagase Shinobu , Ohshika Masato , Ueda Shinya , Satoh Naoki , Tsujii Kaoru
Published: September 2002

A universal structural model for human hair has been proposed in order to understand the physical properties of hair. The model consists of two structural parts, both of which have two states (Two-part/two-state model). The transition temperature (Tc) between the two states of one part is about 70 °C, and that of the other part is about 0 °C in a water medium. These transition temperatures depend highly upon the water content of the hair. A higher transition temperature is observed in hair having a lower water content. Above the transition temperatures, both parts of the hair are soft and plastic (a melted state); they are hard and elastic (a solid state) below the transition points. One part of hair which has a higher transition temperature (ca. 70 °C in water) is assigned to be macrofibril and exo-cuticle consisting of keratinous proteins; the other part with a lower Tc (ca. 0 °C) is inter-macrofibrillar materials, a cell-membrane complex (CMC), and the endo-cuticle of non-keratinous proteins and lipids. This structural model was derived from the results of thermal-setting and relaxation experiments as well as TEM observations after permeating a dye with a high electron density (Erythrosin B).
A Universal Structural Model for Human Hair to Understand the Physical Properties 2. Mechanical and Permeation Behaviors
Authors: Sakai Masahiko , Nagase Shinobu , Okada Tomoyuki , Satoh Naoki , Tsujii Kaoru
Published: September 2002

The mechanical properties of human hair fiber and the permeation behaviors of some dye molecules into hair have been studied, and are here discussed based on a universal structural model proposed by the authors in the previous paper. The model consists of two structural parts, both of which have two states (Two-part/two-state model). One part of the hair, which has a higher transition temperature (Tc; ca. 70 °C in water), is assigned to be macrofibril and exo-cuticle; the other part with lower Tc (ca. 0 °C in water) is inter-macrofibrillar materials, a cell-membrane complex (CMC) and endo-cuticle. The temperature dependence of the elastic modulus of a human hair in the Hookean region clearly shows two break points, indicating the above-mentioned transition temperatures. We have proposed a viscoelastic model based on the two-part/two-state structural model to understand the mechanical behaviors in the Hookean, yield and post-yield regions. The permeation rate of some dye molecules into hair fiber starts to dramatically increase at the higher transition temperature. Such permeation behaviors can also be understood from a universal structural model. The molecular size of dye is a crucial factor in permeation behaviors. Dye molecules with a size smaller than 1.0 nm migrate much more easily into hair.
X-Ray Crystallographic Study on Single-Crystalline Photochromism of 1,2-Bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene
Authors: Yamada Taro , Kobatake Seiya , Irie Masahiro
Published: September 2002

Single-crystalline photochromism of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene was studied by X-ray crystallography. The crystal was irradiated with linearly polarized monochromatic 360 nm light and analyzed with an X-ray diffractometer. The X-Ray crystallographic analysis showed that the conversion from the open-ring to the closed-ring isomers was as much as 8% and that the reaction proceeded in a conrotatory mode. Two sulfur atoms and reactive carbon atoms in the thiophene rings clearly changed their positions. The photogenerated closed-ring isomers completely returned to the initial open-ring isomers in the crystal by irradiation with 650 nm light.
Hydrogen Abstraction Reactions from C2 Hydrocarbons
Authors: Kunioshi Nílson , Mouri Shigeru , Yamashita Noriyuki , Fukutani Seishiro
Published: September 2002

The sequence of hydrogen abstraction reactions from ethane to acetylene, which proceeds in fuel-rich methane flames, has been investigated by an ab initio molecular orbital method. First, the hydrogen abstraction mechanism was elucidated through an analysis of the variation in the electron spin density distributions through the reacting species. The H atoms holding the largest spin densities within a radical where seen to be those being abstracted from the species. The reaction rate coefficients for the four elementary abstraction steps from ethane to acetylene were determined through the transition state theory, and the results were compared with data published in the literature. The obtained rate coefficients were found to be lower than the published data for all four reactions examined. Especially, for two of the reactions, some published data seem to be too large, considering that the rate coefficients obtained through transition state theory tend to be larger than the true values.
Analysis of Water Oxidation Catalysis by Dinuclear Ruthenium Complex [(NH3)5Ru-O-Ru(NH3)5]4+ Incorporated in a Nafion® Membrane
Authors: Nagoshi Kentaro , Yagi Masayuki , Kaneko Masao
Published: September 2002

Catalytic activity of a dinuclear ammine ruthenium complex, [(NH3)5Ru-O-Ru(NH3)5]4+, for water oxidation to evolve O2 was investigated both in homogeneous aqueous solution and in heterogeneous Nafion® membrane systems using CeIV oxidant. It was suggested that the complex works as a four-electron water oxidation catalyst and that the water oxidation by the complex is in competition with a bimolecular decomposition between the complexes. The first-order rate constant (kO2 (s-1)) for O2 evolution and second-order rate constant (kdeact (M-1 s-1)) for bimolecular decomposition were obtained by a kinetic analysis. It was found that kdeact decreased by one order of magnitude by incorporating the complex in the membrane; this was ascribed to the suppression of the bimolecular decomposition. The critical decomposition distance (rd (nm)) between the catalysts was analyzed to be 1.06 nm based on an intermolecular distance distribution.
Photoinduced Electron-Transfer of Inclusion Complexes of Fullerenes (C60 and C70) in γ-Cyclodextrin
Authors: Masuhara Akito , Fujitsuka Mamoru , Ito Osamu
Published: September 2002

Photophysical and photochemical properties of 1:2 inclusion complexes of C60 and C70 in γ-cyclodextrin (γ-CD) have been studied by laser flash photolysis and steady photolysis methods. The triplet-triplet annihilations of C60/γ-CD and C70/γ-CD are retarded, compared with those of the pristine fullerenes. The rate constant for the fluorescence-quenching of C70/γ-CD by 1,4-diazabicyclo[2.2.2]octane was larger than that of C60/γ-CD, indicating incomplete hindrance by γ-CD due to larger size of C70 than C60. A similar trend was also observed in triplet-triplet annihilation processes of the encapsulated fullerenes. Generations of radical ions by photoinduced electron transfer between amines and 3C60*/γ-CD or 3C70*/γ-CD were confirmed by observing the transient absorption bands due to radical anions in the near-IR region. The electron transfer rates for 3C60*/γ-CD or 3C70*/γ-CD were slower than those of corresponding 3C60* or 3C70* in solution by ca. 1/100. For reversible systems in which the cation radicals of amines are stable (for example, p-anisidine), C60•-/γ-CD and C70•-/γ-CD decayed slowly by back electron transfer. For an irreversible system in which the cation radical of amine (nitrilotriethanol) is degraded, the high concentration of C60•-/γ-CD or C70•-/γ-CD was persistent. On addition of methylviologen (MV2+), persistent MV•+ was generated in high concentration as equilibrium with C60•-/γ-CD, suggesting that C60/γ-CD acts as an efficient photosensitizer and an electron mediator to produce MV•+ using nitrilotriethanol as a sacrificial donor.
Inclusion Complexes of Cyclodextrins with Methylene Blue and Acid Orange 7 in Aqueous Solutions
Authors: Hamai Sanyo , Satou Hideyuki
Published: September 2002

Upon the addition of Acid Orange 7 (AO7) to aqueous Methylene Blue (MB) solution buffered at pH 5.0, the absorption spectrum of MB is reduced in intensity, accompanied by a red shift of the absorption peak, indicating the formation of a complex between MB and AO7. From a simulation concerning the fluorescence intensity change of MB, the equilibrium constant for the formation of the 1 : 1 MB-AO7 complex has been estimated to be 66300 mol-1 dm3. γ-Cyclodextrin (γ-CD) forms a 1 : 2 and a 1 : 1 inclusion complex with MB and AO7, respectively. From the absorbance changes, equilibrium constants for the formation of the 1 : 2 γ-CD-MB and 1 : 1 γ-CD-AO7 inclusion complexes have been evaluated to be 2.95×107 mol-2 dm6 and 11000±300 mol-1 dm3, respectively. When γ-CD is added to MB solution containing AO7, the absorption band of MB is enhanced in intensity without an appearance of the MB dimer band, in contrast to MB solution without AO7. This finding indicates the formation of a ternary γ-CD-MB-AO7 inclusion complex. To determine the stoichiometry of the ternary inclusion complex, a continuous variation method using the absorption and fluorescence intensities has been performed under the conditions that the sum of the initial concentrations of γ-CD and AO7 has been kept constant. Both the results indicate the formation of a 2 : 1 : 1 γ-CD-MB-AO7 inclusion complex. The equilibrium constant for the formation of the ternary inclusion complex from γ-CD and the 1 : 1 MB-AO7 inclusion complex has been evaluated to be 3.40×1010 mol-2 dm6 from the fluorescence intensity change.
Characterization of the Light-Harvesting Polypeptide/Bacteriochlorophyll a Complex Isolated from Photosynthetic Bacteria by the Linear Dichroism Spectra
Authors: Iida Kouji , Ohya Nobuyasu , Kashiwada Ayumi , Mimuro Mamoru , Nango Mamoru
Published: September 2002

The linear dichroism (LD) spectra of the light-harvesting polypeptide (LH)/bacteriochlorophyll (BChl a) complex, isolated from photosynthetic bacteria, Rhodospirillum rubrum, were measured to provide insight into the pigment orientation in the LH/BChl a complex. The LD spectrum for the Qy band of BChl a in the complex in a squeezed polyacrylamide gel was positive, while that for the Qx band was negative, indicating that the dipole moment of the Qy band was membrane-parallel while that of the Qx band was membrane-perpendicular. The anisotropy ratio, the LD/A value for the Qy transition of BChl a in the complex, was 0.18 ± 0.02 at a 0.5 compression-ratio, consistent with that for the Qy band of a special pair of BChl a in the reaction center (RC) complex isolated from R. rubrum. This result implies that the orientation of the Qy band in the LH/BChl a complex is perpendicular for the transmembrane axis of the LH in the complex as well as that of the special pair of BChl a in the RC. Furthermore, the LD/A spectrum for the Qy band of BChl a in the LH/BChl a complex indicated that the Qy band was geometrically homogeneous in the direction to the transmembrane axis in the complex.
Photoreactions of 3-(2-Hydroxyphenyl)-1-(substituted phenyl)-2-propen-1-ones (Substituted 2-Hydroxychalcones) in Organic Solvents in the Presence and Absence of Acid
Authors: Matsushima Ryoka , Murakami Tadahiro
Published: September 2002

Absorption spectra and photochemical reactivities of a dozen 3-(2-hydroxyphenyl)-1-(substituted phenyl)-2-propen-1-ones (substituted 2-hydroxychalcones) have been investigated in organic solvents in the presence and absence of added acid. Upon UV irradiation in the presence of 5 mM perchloric acid, flavylium ions were formed in high quantum yields around 0.34, regardless of the nature of the substituents. Upon irradiation in neutral solution, on the other hand, amino-substituted chalcones gave photo-Z-isomers as thermostable products, while the majority of other chalcones gave cyclic hemiacetals (2-hydroxy-2-phenyl-2H-1-benzopyranes). The quantum yields for the photochemical E/Z isomerization in the neutral solution were comparable to those in the acid solution, except for the amino-substituted chalcones which revealed lower quantum yields. Remarkable hypsochromic shifts were observed for the absorption spectra of the amino-substituted chalcones upon addition of acid, reflecting protonation on the amino group.
Benzene-Ethene Interactions as Studied by ab initio Calculations
Authors: Oki Michinori , Takano Sho , Toyota Shinji
Published: September 2002

For a search for π-π* and/or CH-π interactions between benzene and ethene, ab initio calculations were carried out at HF/6-31G**, MP2/6-31G**, and B3LYP/6-31G** levels of theory. Thirteen configurations of benzene and ethene complexes were optimized by the energy gradient techniques, of which only two were real energy-minimum forms and the others were saddle points or conical points. The global minimum configuration is one in which one of the tilted ethene C-H groups interacts with the C-C π-bond of benzene (configuration F-1). A configuration, in which benzene and ethene planes are parallel, was not obtained as a minimum except for MP2 calculations. The intermolecular distances obtained by HF and B3LYP theories were longer than the sum of van der Waals radii, whereas those obtained by the MP2 method were close to the sum. Dipole moments were also obtained that suggest the existence of charge transfer interactions. It is concluded that the molecular interaction energy between benzene and ethene mainly consists of dispersion forces with minor contributions of CT interactions, while the configuration of the global minimum is determined by CH-π interactions. From the frequency analysis for the energy-minimum forms, the normal modes associated with the intermolecular CH-π interactions were obtained at low frequency regions.
Crystal Structure of an Ionic Charge-Transfer Complex of DAP-F4TCNQ (DAP = 1,6-Diaminopyrene, F4TCNQ = 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane)
Authors: Matsushima Koichi , Ogaki Megumi , Naito Toshio , Inabe Tamotsu
Published: September 2002

A charge-transfer complex of DAP with F4TCNQ has been obtained by electrochemical reduction of F4TCNQ in acetonitrile in the presence of DAP·BF4. The crystal comprises segregated one-dimensional columns of donors and acceptors with CH3CN as the crystal solvent. The molecular geometry and infrared spectrum show that the donor and acceptor components are completely ionized. These features are the same as those found in DAP·TCNQ. However, a marked difference lies in the column structure; both the DAP and F4TCNQ columns are composed of the dimerized units, while they are uniform in DAP·TCNQ. The difference can be accounted by the increase of the transfer energy in DAP·F4TCNQ·CH3CN compared with DAP·TCNQ.
Cyclic Voltammetric Characteristics of Tri- and Diarylcarbenium Salts Having Some Methoxyphenyl Groups
Authors: Erabi Tatsuo , Ohtsuki Takayuki , Osaki Eiko , Tomita Nobuyuki , Asahara Masahiro , Wada Masanori
Published: September 2002

Triarylcarbenium salts (Φa3C+, ΦaΦb2C+, Φb3C+, ΦfΦb2C+, ΦeΦb2C+, PhΦb2C+, and FcC+ΦbPh [Φa, Φb, Φe, Φf, Ph, Fc = 2,4,6-(MeO)3C6H2, 2,6-(MeO)2C6H3, 2-(MeO)C6H4, 4-(MeO)C6H4, C6H5, Fe(η5-C5H5)(η5-C5H4)]) showed a reversible redox wave with one-electron transfer at a Pt electrode in 1,2-dichloroethane, while the reduction of diarylcarbenium salts (Φa2C+H, FcC+ΦaH, FcC+ΦbH, FcC+ΦcH, FcC+ΦeH, and FcC+PhH [Φc = 2,5-(MeO)2C6H3]) proceeded irreversibly. A wide range of cathodic shifts in the redox potentials (198—-377 mV for triarylcarbenium salts) and in the reduction peak potentials (-23—-311 mV for monoaryl(ferrocenyl)carbenium salts) could be observed as the number of o- and p-methoxy groups increased. Probably, the electron donation from the o- and p-methoxy substituents to the central carbon caused the wide negative shift in the redox potentials. These triarylcarbenium salts again showed reversible redox waves in their relatively low concentration region at an ITO electrode in an aqueous acidic medium. In the higher concentration region, an anodic wave was varied to a sharp peak, indicating the adsorption of triarylmethyl radicals. It is very interesting that the reversible redox behavior of these triarylcarbenium salts was observable even in an aqueous medium.
Estimation of Off-Site Coulomb Integrals and Phase Diagrams of Charge Ordered States in the θ-Phase Organic Conductors
Authors: Mori Takehiko
Published: September 2002

Intermolecular Coulomb repulsion, V, of the highest occupied molecular orbitals (HOMO) of BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) is calculated for various molecular geometries. The bare V is a quantity that is easily estimated under the point charge approximation. As far as the screened V in actual crystals is proportional to the calculated bare V, the usual θ-phase prefers the horizontal or diagonal stripe, whereas the vertical stripe becomes comparatively stable in the limit of the small dihedral angle (in the metallic limit). The phase diagrams of the θ-phase are discussed under the combination of the static charge distribution (the atomic limit) and the Stoner model (the extended Stoner model). The model contains two order parameters: the spin polarization, Sz, and the charge order, n-1/2. This model explains why the insulating state of the Rb salt below 190 K is a paramagnetic charge-ordered state, while the Cs salt has a different insulating phase below 20 K. The lattice dimerization of the Rb salt can be explained only from V.
Optical-Optical Double-Resonance Spectroscopy of the 1u(3P2) and 2u(3P2) States of I2 Through the A3Π(1u) State
Authors: Ishiwata Takashi , Motohiro Satoshi , Kagi Eriko , Fujiwara Hisashi , Fukushima Masaru
Published: September 2002

Optical-optical double-resonance spectroscopy is used to study the 1u(3P2) and 2u(3P2) ion-pair states of I2 correlating to the lowest ionic state, I-(1S) + I+(3P2). In the (1 + 2) photoexcitation sequence, we gain access to the 1u(3P2) ion-pair state through the A3Π(1u) state. The 2u(3P2) state is also identified from the occurrence of extra lines through heterogeneous coupling with the 1u(3P2) state and an apparent energy shift in the 1u(3P2) state. The energy levels of the 1u(3P2) and 2u(3P2) states were analyzed in detail by including the heterogeneous interaction between these states. We have established the vibrational numbering of the 2u(3P2) state in considering the 1u-2u(3P2) interaction terms under a pure precession approximation. Combined with other results, the present study has allowed us to characterize and map out the ion-pair states of I2 in the 5 eV region.
Phase Behavior of Tetrabutylammonium Salt in Aromatic Hydrocarbons or Aqueous Solutions
Authors: Ohtani Noritaka , Hosoda Yasuhiro
Published: September 2002

The solubility of tetrabutylammonium salt (TBAX; X = Cl, Br, or I) in benzene was examined as a function of temperature. The solubility curve had specific features, which were characterized by critical values corresponding to the Krafft point and the critical micelle concentration of ionic surfactants in water. Above the critical concentration, TBAX was assumed to aggregate in benzene, based on NMR analyses. A slight difference of the oil structure exerted a significant effect on the solubility behavior. In the presence of sodium halides, TBACl or TBABr with water exhibited a specific temperature that was similar to the cloud point. Above that temperature, TBAX was liberated as a liquid to form a liquid-liquid two-phase. The solubility of TBAI in water was poor. It gave a liquid-solid two-phase at low temperatures or a liquid-liquid two-phase above 69 °C, unless the TBAI concentration was too low. The solubility of TBAX in aqueous solution was also dependent on the metal cation of the inorganic salts.
Phase Behavior of Tetrabutylammonium Salt/Oil/Water/Inorganic Salt Four-Component Systems
Authors: Ohtani Noritaka , Yamashita Tsuyoshi , Hosoda Yasuhiro
Published: September 2002

The phase behavior of four-component systems composed of tetrabutylammonium halide (TBAX; X = Cl, Br, or I), nonpolar benzene, water, and sodium halide (NaX) has been examined in detail. According to their constituents, compositions, and temperatures, the four-component systems afforded from single- to four-phase states. There were at least three kinds of liquid phases: a TBAX-rich phase (M), an aqueous solution phase (W), and an oil solution phase (O). In the M phase, TBAX was assumed to form aggregates, like microemulsions, while, in the latter two solution phases, TBAX was present without any aggregated form. When these three liquid phases coexisted, an O-M-W three-liquid-phase equilibrium state occurred. Depending on the temperature and NaX concentration in the W phase, the system changed its state from the O-M-W to the O-M or M-W two-liquid-phase. In some cases, a solid TBAX phase (Q) or solid NaX phase (S) coexisted with these liquid phases. In the presence of excess sodium halide, an O-M-W-S four-phase state was often observed due to the solid sodium halide being precipitated as a solid phase. These phase-separation phenomena were explained based on the amphiphilic nature of the quaternary salts, which bore some resemblance to the surfactant properties.
Apparent Violation of the Third Law without a Detectable Glass Transition in Simple Molecular Solids: Calorimetric Entropy of p-Bromochlorobenzene
Authors: Tozuka Yoshitaka , Akutsu Hiroki , Yamamura Yasuhisa , Saito Kazuya , Sorai Michio
Published: September 2002

The heat capacities of crystalline and liquid p-bromochlorobenzene were measured by adiabatic calorimetry between 6 and 350 K. The crystal melts at 337.99 K with an enthalpy and an entropy of fusion of 18390 J mol-1 and 55.41 J K-1 mol-1, respectively. Neither an ordering phase transition nor a glass transition was detected in the solid state, contrary to an expectation based on the apparent symmetry of the molecule at room temperature due to an orientational disorder. The calorimetric entropy of the gas was estimated using the vapor-pressure data. A comparison with spectroscopic entropy based on a quantum chemical calculation shows that the PBCB crystal has a residual entropy of about Rln 2 (R: gas constant), which is compatible with the orientational disorder at room temperature. The absence of a sizeable anomaly due to a glass transition suggests two possibilities: an undetectably small thermal anomaly around the glass transition, or a glass-transition temperature higher than the temperature of fusion.
Preparation and Crystal Structure of the trans(O5) Isomer of Magnesium(ethylenediamine-N,N,N′-triacetato-N′-3-propionato)cuprate(II) Octahydrate, Mg[Cu(ed3ap)]·8H2O. Stereochemistry of Octahedral Cu(II)-EDTA-Type Complexes in Relation to the Structure of the Ligand
Authors: Radanovic Dušan J , Ama Tomoharu , Gurešic Dejan M , Ristanovic Divna M , Radanovic Dušanka D , Kawaguchi Hiroshi
Published: September 2002

The hexadentate complex trans(O5)-Mg[Cu(ed3ap)]·8H2O (1) (ed3ap = ethylenediamine-N,N,N′-triacetate-N′-3-propionate (4-) ion) has been prepared and its structure established by X-ray crystallography. The complex crystallizes in space group Pna21 of the orthorhombic crystal system. The structure converged to R = 0.076 for 2213 observed reflections. The Cu(II) ion is surrounded by two nitrogen and four oxygen atoms of the ligand, making an elongated rhombic octahedron (tetragonality, T = 0.859). The conformations of the chelate rings of the complex anion were found to be an envelope (or twist) for the five-membered rings and a distorted skew-boat (half-chair) for the G2 β-alaninate ring. The extremely large total deviation observed for the R2 ring (-11°) is not common for axially coordinated glycinates in M-edta-type complexes. A comparison of the structures of octahedral Cu(II)-edta-type complexes shows an expected variation in their stereochemistry, depending on the structure of the ligand and the geometry of the complex. Data for the electronic absorption and reflectance spectra are also reported.
Rate of Complex Formation and Solvent Extraction of Chromium(III) Produced by the Reduction of Chromium(VI) with Acetylacetone in Aqueous Solutions
Authors: Yamada Meri , Sato Yoshihiro , Sekine Tatsuya
Published: September 2002

The rate and degree of solvent extraction of chromium(III), which was produced by the reduction of chromium(VI) with ascorbic acid in 0.1 mol dm-3 sodium nitrate solutions containing acetic acid/acetate ion as the buffer, were examined by using acetylacetone as the extractant and chloroform as the solvent. The rate of formation of an extractable acetylacetonato complex was greater than that when metal ion was added as hydrated Cr3+ until a certain amount of chromium(III) was extracted. Although the rate was first order with respect to the acetylacetone concentration and inverse first order with respect to the hydrogen-ion concentration, the extraction of chromium(III) formed in this way was dependent on the concentration of acetate ions in the aqueous solution. From these results, it was assumed that the chromium(III) produced from chromium(VI) formed a complex with an acetate ion just after the reduction occurred, and that the complex functions as a precursor to the extraction. The acetylacetone reacted with the precursor much more rapidly than the hydrated chromium(III) ion. From the change in the UV-vis spectrum of the complex and in the easiness of stripping of chromium(III) from chloroform with a nitric acid solution, the thus-formed extractable complex was assumed to be an intermediate which changed to a final complex similar to that obtained by the dissolution of crystals of tris(acetylacetonato)chromium(III) in chloroform.
Structural Characteristics of S-Bridged Trinuclear Complexes [{Pd(terpy)}2{Pd(aet)2}]4+ (terpy = 2,2′ : 6′,2′′-Terpyridine, aet = 2-Aminoethanethiolate): Effects of Counter Anions and Solvent on Intra- and Intermolecular Stacking Arrangements
Authors: Yamada Yasunori , Fujisawa Kiyoshi , Okamoto Ken-ichi
Published: September 2002

S-bridged trinuclear Pd(II) complexes, [{Pd(terpy)}2{Pd(aet)2}]X4·nSolv (terpy = 2,2′ : 6′,2′′-terpyridine, aet = 2-aminoethanethiolate; X = PF6-, n = 2, Solv = CH3CN (1); X = BF4-, n = 0.5, Solv = H2O (2); X = BF4-, n = 0 (3); 2X = SiF62-, n = 6, Solv = H2O (4)), were obtained by the reactions of [Pd(aet)2] (aet = 2-aminoethanethiolate) with [Pd(NO3)(terpy)]+ (terpy = 2,2′ : 6′,2′′-terpyridine) using some kinds of counter anions and solvents. The molecules of 1—4, whose structures were determined by X-ray crystallography, contain two {Pd(terpy)} moieties bridged by one [Pd(aet)2] unit. Although the molecular structures of these complexes are similar to each other, they have significantly different intermolecular structures from each other. While 1 and 2 take monomeric structures, 3 and 4 exist as polymeric forms. These structural features also reflect their diffuse reflection spectra.
Calorimetric Study of Hydrated Potassium Molybdenum Bronze
Authors: Suzuki Takashi , Eda Kazuo , Sotani Noriyuki
Published: September 2002

Hydrated and dehydrated potassium bronzes, K0.25H0.07MoO3·0.54H2O (HyK-H2) with the six-coordination structure and K0.25H0.07MoO3 (DehyK) with the eight-coordination one, were synthesized by a new direct method. The standard enthalpy of formation was determined by solution calorimetry to be -4950 ± 1 kJ mol-1 for HyK-H2 and -4817 ± 1 kJ mol-1 for DehyK, respectively. According to the thermodynamic data, HyK-H2 is stable.
19F NMR Study of the Heme Orientation and Electronic Structure in a Myoglobin Reconstituted with a Ring-Fluorinated Heme
Authors: Hirai Yueki , Yamamoto Yasuhiko , Suzuki Akihiro
Published: September 2002

13,17-Bis(2-carboxylatoethyl)-3,8-diethyl-2-fluoro-7,12,18-trimethylporphyrinatoiron(III) was reconstituted with sperm-whale apomyoglobin to investigate the molecular and electronic structures of the heme-active site by 19F NMR spectroscopy. The detection of the nuclear Overhauser effect between the substituted fluorine atom for a heme side-chain and an amino acid side-chain proton in the reconstituted myoglobin unequivocally determines the heme orientation relative to the protein matrix. The orientation of this fluorinated hemin in the protein was found to differ by a 180° rotation of the heme plane about its C2-axis from that of structurally analogous mesohemin in the active site of myoglobin. Thus, the difference between the methyl group and fluorine atom as the peripheral side-chain at the 2-position of the porphyrin is a critical determinant for the thermodynamical stability of the heme orientational isomers. The effects of the heme orientation on the electronic structure of the active site of myoglobin in a variety of iron oxidation, spin, and ligation states were characterized by 19F NMR spectroscopy. The present study demonstrated that the 19F NMR signals observed for hemoprotein reconstituted with fluorinated hemin provides useful information on the relationship between the heme orientation relative to the protein and its electronic structure in all accessible oxidation/spin states of the protein, that can be hardly obtained by 1H NMR spectroscopy.
A Practical Method for the Synthesis of Enantiomerically Pure 4-Borono-L-phenylalanine
Authors: Nakamura Hiroyuki , Fujiwara Masaru , Yamamoto Yoshinori
Published: September 2002

Enantiomerically pure L-BPA (4-borono-L-phenylalanine) was synthesized from L-tyrosine or 4-iodo-L-phenylalanine derivatives using the palladium-catalyzed cross-coupling reaction of pinacolborane (2,3-dimethyl-2,3-butanediolatoboron). Cbz-Tyr(Nf)-OBzl (2b) underwent the cross-coupling reaction with pinacolborane (1) in the presence of [PdCl2(PPh3)2] catalyst to give N-benzyloxycarbonyl-4-(2,3-dimethyl-2,3-butanediolatoboryl)-L-phenylalanine benzyl ester (3a) in 58% yield. The reaction of the 4-iodo-L-phenylalanine derivatives, such as N-benzyloxycarbonyl-4-iodo-L-phenylalanine benzyl ester (2c), N,N-dibenzyl-4-iodo-L-phenylalanine benzyl ester (2d), (4S)-3-benzyloxycarbonyl-4-(4-iodobenzyl)-5-oxazolidinone (2e), and (4S)-3-t-butyloxycarbonyl-4-(4-iodobenzyl)-5-oxazolidinone (2f), with 1 proceeded very smoothly in the presence of [PdCl2(dppf)] catalyst, giving N-benzyloxycarbonyl-4-(2,3-dimethyl-2,3-butanediolatoboryl)-L-phenylalanine benzyl ester (3a), N,N-dibenzyl-4-(2,3-dimethyl-2,3-butanediolatoboryl)-L-phenylalanine benzyl ester (3b), (4S)-3-benzyloxycarbonyl-4-[4-(2,3-dimethyl-2,3-butanediolatoboryl)benzyl]-5-oxazolidinone (3c), and (4S)-3-butyloxycarbonyl-4-[4-(2,3-dimethyl-2,3-butanediolatoboryl)benzyl]-5-oxazolidinone (3d), respectively, in high yields. Deprotection of 3a—d gave enantiomerically pure L-BPA in high total yields.
Oxygen Atom Exchange Reaction between Tetradentate Schiff Base-Oxovanadium(IV) Complexes and Water
Authors: Tsuchimoto Masanobu , Hoshina Gakuse , Uemura Ryushi , Nakajima Kiyohiko , Kojima Masaaki , Ohba Shigeru
Published: September 2002

The oxygen atom exchange reaction between the terminal oxygen atom (V=O) of tetradentate Schiff base-oxovanadium(IV) complexes and water slowly proceeds in DMSO solutions. The rate constants kobs for the isotopic oxygen atom exchange reaction in DMSO solutions containing excess H218O at 50 °C under an argon atmosphere were obtained for several complexes (6×10-7 to 6×10-5 s-1). The reaction proceeds faster for those complexes with electron-withdrawing groups at the Schiff base ligand moieties, and slower for the complexes with bulky hydrophobic groups. The oxygen atom exchange reaction and isomerization reaction under an argon atmosphere and in air were investigated for oxovanadium(IV) complexes that have two geometrical isomers. Water molecules attack the vanadium atom mainly from the same side of the oxo ligand for the oxovanadium(IV) complexes, whereas mainly from the opposite side of the oxo ligand for the oxovanadium(V) complexes produced by oxidation with air.