bluuebunny/crossref_metadata_2025 huggingface dataset:
Echo FT-EPR Study of the Photochemical Reduction and Oxidation Reactions of 2,5-Di-t-butyl-1,4-benzoquinone and 2,5-Di-t-butylhydroquinone by Xanthene Dyes
Authors: Katsuki Akio , Akiyama Kimio , Tero-Kubota Shozo
Published: July 2006

Electron spin polarization has been studied in order to clarify the character of the short-lived radical-pair (RP) intermediates generated from the photosensitized reduction of 2,5-di-t-butyl-1,4-benzoquinone and the oxidation of 2,5-di-t-butylhydroquinone by xanthene dyes using FT-EPR spectroscopy. Unusual absorptive electron spin polarization and heavy atom effects were observed in a former photoreduction system, indicating the production of contact RP as the reaction intermediate. Absorptive polarization is created by sublevel selective back electron transfer in the triplet contact RP due to the spin-orbit coupling interaction. On the other hand, it has also been shown that for the photooxidation system a pure RP mechanism is operative to create spin polarization, suggesting the generation of a solvent separated RP as an intermediate. The reaction rate constants for electron transfer and hydrogen abstraction reactions were also determined by analyses of the time profile of the chemically induced electron spin polarization spectra.
Spectroscopic and Kinetic Studies on Volume Expansion Processes of Photoresponsive Polyacrylamide Microgels in Water
Authors: Ishikawa Masazumi , Misawa Hiroaki , Kitamura Noboru , Irie Masahiro , Masuhara Hiroshi
Published: July 2006

Photostimulated volume expansion of polyacrylamide microgels (initial radius = 11—235 μm) bearing triphenylmethyl cyanide moieties (AAm-TPMCN) in water was studied on the basis of simultaneous measurements of the degree of ionic dissociation (α) of TPMCN to TPM+ (triphenylmethyl cation) and the gel radius. The time profile of the radius change, r(t), was analyzed by a convolution relation between r(t) and the time course of α (α(t)). The characteristic time constants of the volume change, related to the cooperative diffusion coefficient of the gel network, were determined for AAm-TPMCN gels with various radii. The faster photoresponse time of the volume change for the smaller AAm-TPMCN gel was explained in terms of the diffusion theory of gel networks in water.
A Laser Flash Photolysis Study of the Intramolecular Energy Transfer Reaction from Benzophenone to Norbornadiene Covalently Bonded by a Rigid Steroid Bridge
Authors: Cao Hong , Akimoto Yukimi , Fujiwara Yoshihisa , Tanimoto Yoshifumi , Zhang Li-Ping , Tung Chen-Ho
Published: July 2006

The photoinduced intramolecular energy-transfer (ET) reaction between benzophenone (BP) and norbornadiene (N) covalently bonded by a rigid steroid bridge in acetonitrile has been studied by laser flash photolysis. The ET rate constant for the excited triplet BP (3BP*) to N is 6.1 × 104 s−1, whereas the constant for the intramolecular hydrogen atom abstraction of 3BP* from the steroid is 1.91 × 105 s−1.
EPR Spectra of Gadolinium(III)-β-diketonate Complexes
Authors: Miyamoto Ryo , Sudoh Susumu
Published: July 2006

The electron paramagnetic resonance spectra of some gadolinium(III)-β-diketonate complexes were observed as frozen solutions. The observed spectra differ from each other upon changing the ligands, indicating that a change of the ligand fields and/or coordination structure of the ligands has a great effect on the behavior of the inner 4f electrons. Zero field splitting (ZFS) parameters were estimated by spectral simulations for the 8S7/2 system. The EPR spectral simulations attempted so far indicate that at least the ZFS parameter (|D|) for the Gd(hfa)3 complex is much smaller than that for other complexes, such as Gd(acac)3.
Synthesis and Crystal Structure of Bis(1,1,1-tris(dimethylphosphinomethyl)ethane)iron(II) Tetrafluoroborate Dihydrate
Authors: Kashiwabara Kazuo , Ozeki Yuji , Kita Masakazu , Fujita Junnosuke , Nakajima Kiyohiko
Published: July 2006

An air and thermally stable iron(II) complex of 1,1,1-tris(dimethylphosphinomethyl)ethane (mmtp), [Fe(mmtp)2](BF4)2·2H2O, has been prepared, and the crystal structure has been determined by X-ray analysis. The complex was crystallized in the orthorhombic, space group Pca21 with four molecules in a unit cell of dimensions a = 17.448(4), b = 17.574(4), c = 11.367(2) Å, and V = 3485(1) Å3. Final R was 0.047 for 1671 reflections. The average Fe–P bond length of 2.312(5) Å is intermediate between those of [Co(mmtp)2][Co(CN)6]·2.25H2O (av Co–P = 2.331(9) Å) and [Cr(mmtp)2] (av Cr–P = 2.287(1) Å), in which Fe(II), Co(III), and Cr(0) have the same low-spin d6 electron configuration. A less stable dimeric complex, [Fe2(μ-Cl)3(mmtp)2]B(C6H5)4·H2O, has also been isolated. Absorption spectra and cyclic voltammograms have been compared between the Fe(II) and Co(III) complexes.
A Revised Structure of Chloranthalactone F and Chloranthalactone A Photodimer
Authors: Okamura Hiroaki , Iwagawa Tetsuo , Nakatani Munehiro
Published: July 2006

Two known lindenane sesquiterpenoids, chloranthalactone F and chloranthalactone A photodimer, were identified to be the same by direct comparison of the samples and their spectra. Both of their structures were revised to a new structure, head-to-head, anti dimer of chloranthalactone A, from the spectroscopic and chemical studies. Chloranthalactone A photodimer has been reported as an artifact, but this compound was observed as a natural product in the leaves of Chloranthus glaber.
Formation of Acyl-Substituted Nitrile Ylides by Rh2(OAc)4-Catalyzed Decomposition of α-Diazocarbonyl Compounds in Nitriles
Authors: Fukushima Kazuaki , Ibata Toshikazu
Published: July 2006

The Rh2(OAc)4-catalyzed reactions of α-diazocarbonyl compounds in nitrile in the presence of dimethyl acetylenedicarboxylate (DMAD) gave oxazole and pyrrole derivatives. The formation of the oxazole derivatives is explained in terms of the 1,5-cyclization of an acyl-substituted nitrile ylide intermediate, and the formation of the pyrrole derivatives is explained by the 1,3-dipolar cycloaddition of the same intermediate with DMAD. The regiochemistry of the cycloaddition of the acyl-substituted nitrile ylide with methyl propiolate showed that the contribution of an allenyl-type resonance structure plays an important role in the acyl-substituted nitrile ylide reaction.
Three New Triterpenoidal Saponins Acylated with Monoterpenic Acid from Albizziae Cortex
Authors: Ikeda Tsuyoshi , Fujiwara Satoko , Kinjo Junei , Nohara Toshihiro , Ida Yoshiteru , Shoji Junzo , Shingu Tetsuro , Isobe Ryuichi , Kajimoto Tetsuya
Published: July 2006

The structures of Julibrosides I, II, and III, isolated from dried stem bark of Albizzia julibrissin DURAZZ (Albizziae Cortex), were characterized as complex triterpenoidal glycosides linked to the monoterpene glycoside dimer, mainly by means of an NMR spectroscopic method. These compounds have a common structure comprising from acacic acid, the (6S)-2-trans-6-hydroxy-2,6-dimethy1-2,7-octadienoyl-6-O-quinovopyranoside dimer, and α-l-arabinofuranosyl-(1→4)-[β-d-glucopyranosyl-(1→3)]-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranoside. The diversity of the oligosaccharides attached to the C-3 hydroxyl group of acacic acid, an oleanane-type triterpene, makes a distinction between Julibrosides I, II, and III.
Synthesis of Rubidium and Cesium Tellurocarboxylates and an X-Ray Structural Analysis of Heavy Alkali Metal Monochalcogenocarboxylates
Authors: Kawahara Yasuyuki , Kato Shinzi , Kanda Takahiro , Murai Toshiaki , Ebihara Masahiro
Published: July 2006

A series of rubidium and cesium tellurocarboxylates (2 and 3) were synthesized from the reaction of O-trimethylsilyl tellurocarboxylates (1) with rubidium and cesium fluorides in moderate isolated yields and characterized by 1H, 13C, and 125Te NMR spectroscopy and X-ray diffraction. The carbon–oxygen distance [1.235(6) Å] of the tellurocarboxyl group of crystalline cesium 2-methoxybenzenecarbotelluroate (3f) showed a typical value of the carbon–oxygen double bond. The crystal packing of 3f shows the possibility of an interaction between the cesium cation and the aromatic ring carbon. The thio- and selenocarboxyl groups of the corresponding sulfur and selenium isologues (4 and 5) also indicate a double bond [1.231(4) and 1.226(5) Å] between the carbon and oxygen, respectively. The salts (2 and 3) readily react with iodomethane to afford the corresponding Te-methyl tellurocarboxylates in good yields. The reaction between 3 and tetramethylammonium chloride was found to give a novel quaternary ammonium salt (8) of tellurocarboxylic acid, where the dihedral angle between benzene ring and the tellurocarboxyl group of 8 is ca. 90°. Crystallographic data for 3f, 4, 5, and 8 are as follows. 3f: P21/n, a = 7.182(2), b = 12.161(5), c = 12.151(3) Å, β = 92.57(2)°, V = 1060.2(6) Å3, dcalcd = 2.479 g cm−3, Z = 4, R = 0.035, Rw = 0.043. 4: Pbca, a = 8.995(2), b = 29.936(2), c = 7.291(1) Å, V = 1963.3(5) Å3, dcalcd = 2.030 g cm−3, Z = 8, R = 0.024, Rw = 0.021. 5: Pbca, a = 9.290(1), b = 30.207(2), c = 7.193(2) Å, V = 2018.5(3) Å3, dcalcd = 2.284 g cm−3, Z = 8, R = 0.029, Rw = 0.020. 8: P212121, a = 11.844(2), b = 14.014(2), c = 8.650(1) Å, V = 1435.8(3) Å3, dcalcd = 1.558 g cm−3, Z = 4, R = 0.044, Rw = 0.047.
Synthesis and Properties of Methano-Bridged Bisdehydro[17]-, -[19]-, -[21]annulenones and the Related Compounds
Authors: Higuchi Hiroyuki , Kiyoto Seiken , Sakon Chiaki , Hiraiwa Naoki , Asano Kaori , Kondo Shiro , Ojima Juro , Yamamoto Gaku
Published: July 2006

14-Methyl-10,12-bisdehydro-4,9-methano-1H-[17]annulen-1-one, 14-methyl-10,12-bisdehydro-4,9-methano-1H-[19]annulen-1-one, and 16-methyl-12,14-bisdehydro-6,11-methano-1H-[21]annulen-1-one, as well as their methylated and benzannelated derivatives, were synthesized and their tropic properties were studied by NMR and UV spectra under neutral and acidic conditions. The tropicity in these compounds was found to be lower than in their non-bridged monocyclic counterparts. Thus the methano-bridge works to decrease the planarity of the peripherally conjugated system.
Dehydrooligopeptides. XVIII. Enzymatic Hydrolysis and Coupling of Dehydrodipeptide Esters Containing α-Dehydroamino Acid Residue by Using Papain
Authors: Shin Chung-gi , Kakusho Takeshi , Arai Kazushige , Seki Masashi
Published: July 2006

The enzymatic hydrolysis of N-protected dehydrodipeptide methyl esters (2) (Protect-ΔAA-AA-OMe) was first achieved, despite the requisite of the only neutral and large proteinic l-α-amino acid (AA) in the case using papain. Furthermore, the reverse enzymatic coupling of the C-component 2 with N-component α-amino acid anilides or dehydrodipeptide esters containing dehydrovaline (ΔVal) residue was also successful. Consequently, the present study suggests that the proteolytic enzyme papain is able to become a very useful tool for peptide synthesis by a coupling of the C-component dehydropeptide with N-component α-amino acid, peptide, or dehydropeptide.
Characterization of a Longicyclic (2,2,2,2) Conjugated π System in 1,4-Difluorobenzene–Naphthalene Biplanemer
Authors: Okamoto Hideki , Satake Kyosuke , Kimura Masaru
Published: July 2006

The electronic absorption spectrum of a 1,4-difluorobenzene–naphthalene biplanemer 1 exhibited a characteristic absorption band around 290 nm. This was attributable to intramolecular charge transfer interaction between the longicyclic conjugated π system and the benzene chromophore. The oxidation potential of 1 was 1.70 V (vs. Ag/AgCl), which was lower than those of the related compounds in which one of the double bonds of 1 was hydrogenated. Thermally, the biplanemer 1 underwent facile Cope rearrangement, followed by dehydrofluorination, to give 1-(4-fluorophenyl)naphthalene and 2-(3-fluorophenyl)naphthalene.
Catalytic Ability of Octopus-Type Calixarene in the Formation of Ethers from Phenols and Alkyl Halides or 1-Chloro-4-nitrobenzene
Authors: Taniguchi Hisaji , Otsuji Yoshio , Nomura Eisaku
Published: July 2006

The formation of ethers was catalyzed by 5,11,17,23,29,35-hexa-p-t-butyl-37,38,39,40,41,42-hexakis(3,6,9-trioxadecyloxy)calix[6]arene (1). It was found that the calixarene-catalyzed reaction of phenol with benzyl bromide in the presence of KOH in CH2Cl2 yields only the O-alkylated product and this reaction proceeds according to Michaelis–Menten type kinetics. The calixarene 1 also catalyzed the reactions of phenols with dichloromethane and 1-chloro-4-nitrobenzene.
Synthesis of α-Tocopherol: Scandium(III) Trifluoromethanesulfonate as an Efficient Catalyst in the Reaction of Hydroquinone with Allylic Alcohol
Authors: Matsui Makoto , Karibe Norio , Hayashi Kenji , Yamamoto Hisashi
Published: July 2006

Scandium(III) trifluoromethanesulfonate was found to be an efficient catalyst as a Lewis acid for the condensation reaction of trimethylhydroquinone with isophytol to afford α-tocopherol. The condensation reaction proceeded smoothly using only a 0.001 molar amount of the catalyst. The catalyst was easily recovered from an aqueous layer after the reaction was completed, and could be reused.
Novel Synthesis of γ-Lactones Starting from β,γ-Unsaturated Carboxylic Esters
Authors: Kayano Akio , Yajima Yumi , Akazome Motohiro , Fujita Makoto , Ogura Katsuyuki
Published: July 2006

A novel synthetic route to highly substituted γ-lactones was achieved by an intermolecular radical addition to 4-(methylthio)-4-(p-tolylsulfonyl)-3-butenoic ester (1) and its 2-(ethoxycarbonyl) derivative (2), which were easily prepared from (methylthio)methyl p-tolyl sulfone. Upon the irradiation of a solution of 1 and benzophenone in an alcohol (R1R2CHOH), the 1-hydroxyalkyl radical (R1R2C–OH) was generated and added regiospecifically to the 3-position of 1 to form an adduct that led to a γ-lactone by spontaneous intramolecular condensation. Similarly, 2 reacted with the alcohol to give α-(ethoxycarbonyl)-γ-lactones. The alcohol, which is a high boiling liquid or solid, can be employed in the form of a solution (10 molar amounts in acetonitrile) without greatly lowering the reaction efficiency.
A Convenient Method for the Preparation of Nitro Olefins by Nitration of Olefins with Nitrogen Monoxide
Authors: Hata Eiichiro , Yamada Tohru , Mukaiyama Teruaki
Published: July 2006

Olefins with a terminal double bond or conjugated with aromatic nucleus are successfully nitrated into nitro olefins in good-to-high yields on treatment with nitrogen monoxide (NO) in 1,2-dichloroethane. Nitro alcohols formed as by-products are dehydrated to yield nitro olefins by the subsequent treatment with acidic activated alumina. By GC analysis, it was confirmed that an equimolar amount of nitrogen gas was evolved during the present nitration. A possible reaction pathway including the formation of nitro nitroso compounds, key intermediates, is described. The key intermediates are transformed into nitro olefins by reaction with nitrogen monoxide.
Absolute Configuration of (+)-Aureothin: A Toxic Metabolite Possessing γ-Pyrone Unit
Authors: Ishibashi Yasuharu , Ohba Shigeru , Nishiyama Shigeru , Yamamura Shosuke
Published: July 2006

The absolute configuration of aureothin (1) has been determined by synthesis of (−)-aureonone (4) bearing R-configuration. X-Ray single crystallographic analysis of 21 guaranteed the stereochemistry of the chiral center introduced by Sharpless asymmetric epoxidation, as well as that of isoaureothin (3) which was previously synthesized in a similar pathway. Aureothin (1) itself was also synthesized, although Wittig coupling reaction of 4 under basic conditions, caused a partial epimerization of the chiral center.
Synthesis, Characterization, and Catalytic Activity of NAPO-5 and NAPO-11
Authors: Elangovan Shanmugam P , Krishnasamy Vengaimuthu , Murugesan Velayutham
Published: July 2006

Nickel-substituted aluminophosphate molecular sieves (NAPO-5 and NAPO-11) were synthesized hydrothermally using triethylamine and dipropylamine as templates. Structures were confirmed by X-ray powder pattern, and unit cell parameters calculated by a standard least square refinement technique. The isomorphous substitution of nickel in the aluminophosphate framework is evidenced by the considerable increase in unit cell volume compared to unsubstituted AlPO4-5 and AlPO4-11. In addition, electron spin resonance and diffuse reflectance spectra were carried out to produce supporting evidence for the isomorphous substitution of nickel. Acidity was determined by a TPD-TGA method which shows two types of acid sites. Symmetry and asymmetry vibrations were obtained from infrared spectra. Chemical analysis by ICP and BET surface area are also reported. The physicochemical properties of the catalysts were correlated towards isomerisation of camphene at various (WHSV)−1 values and temperatures. The products formed are tricyclene and 2-bornene and the selective formation of tricyclene was achieved over these catalysts.
The Catalytic Life of CdBr2–KBr and Its Affect on the Rate of Indole Formation from Aniline and Ethylene Glycol
Authors: Seto Takatoshi , Kujira Katsufumi , Iwane Hiroshi , Imanari Makoto
Published: July 2006

In the liquid-phase synthesis of indole from aniline and ethylene glycol (EG), a CdBr2–KBr catalyst gave a high yield of indole. In recycling experiments using the catalyst in an autoclave, the yield of indole remained stable and the inorganic components of the catalysts did not suffer degeneration. The time course of the reaction under high pressure and high temperature was evaluated using a newly devised autoclave. The rate of formation of indole was determined to be proportional to the concentrations of both EG and the catalyst. Based on these findings for the reaction over CdBr2–3KBr, it is clear that this catalyst provides a simple and low-cost catalytic process for the formation of indole.
Transition Metal-Catalyzed Synthesis of Silicon Polymers
Authors: Yamashita Hiroshi , Tanaka Masato
Published: July 2006

Si–H and Si–Si bonds are efficiently transformed by early and late transition metal catalyses that involve possible key elemental steps, such as σ-bond metathesis, the oxidative addition of Si–H and Si–Si bonds, insertion of unsaturated compounds into silylmetals, the reductive elimination of Si–Si and Si–C bonds, and silylene generation via α-substituent migration in silylmetal species. These catalyses have enabled us to develop a dehydrogenative poly/oligosilane formation from hydrosilanes, oligosilane formation via a redistribution of hydrodisilanes, silylene-phenylene polymer synthesis via a redistribution of bis(trihydrosilyl)benzene, and (step-)ladder polycarbosilane synthesis by a dehydrogenative double silylation of diynes with a tetrakis(hydrosilyl)benzene. Insertion of unsaturated compounds (acetylenes, quinones, etc.) into Si–Si bonds of polymer backbones provides a new methodology for the modification/synthesis of silicon polymers. Cyclooligosilanes and cyclic disilanes undergo ring-opening copolymerization with p-quinones to give silylene and arylenedioxy unit-containing polymers. Other relevant processes as well as some chemical and physicochemical properties (ceramization, electric conductivity, thermal stability, etc.) of the resulting polymers are also described.
Structure and Reactivity of C2 Species on Polymetallic Systems
Authors: Akita Munetaka , Moro-oka Yoshihiko
Published: July 2006

A variety of polymetallic C2 (C2 and C2H) complexes are prepared by structure expansion of parent metal acetylide complexes, Fp*–C≡C–H (1) and Fp*–C≡C–Fp* (2) [Fp* = (η5–C5Me5)Fe(CO)2], and their structure and reactivity have been investigated as models for surface-bound C2 species formed during catalytic CO hydrogenation. The results summarized here involve (1) intramolecular 1,2-H shift of the C2H complexes relevant to the 1-alkyne-to-vinylidene rearrangement within a metal coordination sphere, (2) electronic influence of metal centers on the structure of dinuclear bridging alkynyl complexes, (3) conversion of the C2 moiety into various C2 functional groups, and (4) synthesis of higher nuclearity dicarbide (C2) cluster compounds with novel coordination structure by sequential addition reactions of metal fragments and direct coupling of a preformed low-nuclearity cluster structure.
Nonlinearity of the Enthalpic Response Function to a Temperature Jump and Its Interpretation Based on Fragility in Liquid Glasses
Authors: Fujimori Hiroki , Fujita Hiroaki , Oguni Masaharu
Published: July 2006

Irreversible enthalpy-relaxation processes were tracked under a constant temperature condition by the temperature jump method for liquid 1,3-diphenyl-1,1,3,3-tetramethyldisiloxane with an adiabatic calorimeter, and simulated based on a double-well potential model with a computer. The processes were observed to show remarkable nonexponentialities and were characterized in terms of a stretched exponential function. The nonexponentiality parameter (β) depended strongly on the magnitude of the temperature jump, indicating the nonlinearity of the relaxation processes. The results of the nonlinearity parameter (δ) combined with those of 1,2-propanediol and glycerol indicated that the nonlinearity originated primarily due to the fragility of the liquid, namely the non-Arrhenius property of the relaxation times. The degree of the nonlinearity was smaller in the endothermic processes than in the exothermic ones. The difference is discussed based on the results of a computer simulation.
Structure, Composition, and Vibrational Property of Iodine-Doped Polyvinyl Alcohol Studied by Temperature-Dependent I K-Edge Extended X-Ray-Absorption Fine Structure
Authors: Yokoyama Toshihiko , Kaneyuki Kentaro , Sato Hitoshi , Hamamatsu Hiroshi , Ohta Toshiaki
Published: July 2006

The temperature dependence of the I K-edge extended X-ray absorption fine-structure (EXAFS) spectra of a highly oriented iodine-containing polyvinyl alcohol (I-PVA) film was investigated in order to reveal any local structures around I. It was firstly demonstrated that an analysis of the EXAFS amplitude, which is associated with the Debye–Waller factor (mean square relative displacement) provides information concerning the composition ratio of the dopant species. In the present high-contrast I–PVA film it was found that a significant amount (64%) of isolated I− is present, and that the polyiodine species, which contributes to a high polarization property of I–PVA for ultraviolet and visible light, consists of 21% I3− and 15% I5−, without containing neutral I2.
Thermoosmosis and Transported Entropy of Water across Hydrocarbonsulfonic Acid-Type Cation-Exchange Membranes
Authors: Suzuki Takashi , Iwano Keiko , Kiyono Ryotaro , Tasaka Masayasu
Published: July 2006

Solvent transport across hydrocarbonsulfonic acid-type cation-exchange membranes was measured for aqueous electrolyte solutions under a temperature difference and an osmotic pressure difference. The hydrocarbonsulfonic acid-type cation-exchange membranes, Aciplex® K-181, Aciplex® K-182, and Neosepta® C66-5T with the H+, Li+, Na+, K+, NH4+, CH3NH3+, (CH3)2NH2+, (CH3)3NH+, (CH3)4N+, (C2H5)4N+, (n-C3H7)4N+, and (n-C4H9)4N+ forms were used. The direction of thermoosmosis across the membranes with the H+ and the Na+ forms was from the cold side to the hot side, as observed for various anion-exchange membranes. However, the direction was from the hot side to the cold side for the membranes with the ammonium and the alkylated ammonium ion forms, except for Neosepta® C66-5T with the (CH3)4N+, (C2H5)4N+, and (n-C3H7)4N+ forms. This is why the entropy of the water in the membranes will increase with increasing the number of hydrogens combining with the nitrogen of the alkylated ammonium counterions, because they are exchangeable with the hydrogens of water molecules in the membranes. Thermoosmosis across the membranes with the (n-C3H7)4N+ and the (n-C4H9)4N+ forms will also occur toward the cold side, because the hydrophobic interaction between the hydrophobic alkyl groups of the counterions and the membrane matrix is very strong and the membranes act as a hydrophobic polyethylene membrane.
Pressure Effect on the Inter- and Intramolecular Vibrations of Pyrazine Crystal
Authors: Maehara Masayoshi , Kawano Hiroshi , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi
Published: July 2006

The effect of pressure on the Raman active inter- and intramolecular vibrations of the pyrazine crystal was studied under hydrostatic pressure up to 5 GPa. The frequency shift of the intermolecular vibrations and the discontinuous variation of the bandwidth of the ν2 and ν1 intramolecular vibrations induced by pressure at constant temperature indicate that the pyrazine crystal undergoes phase transition (change of the molecular orientation in the crystal) under about 1 GPa. The pressure-induced frequency shift of the intramolecular vibrations was calculated using an intermolecular potential of the atom–atom type. The calculation also suggests the occurrence of the phase transition of the crystal.
Raman Spectroscopic Study on the Temperature Dependence of the Uncoupled O–D Stretching Band from HDO Molecules in Concentrated Aqueous Zn(ClO4)2 Solutions
Authors: Kameda Yasuo , Sugawara Ikuko , Kijima Ken-ichi , Usuki Takeshi , Uemura Osamu
Published: July 2006

Polarized Raman spectra of the uncoupled O–D stretching vibrational bands in concentrated aqueous Zn(ClO4)2 solutions have been recorded in the temperature range of 26—95 °C. Observed isotropic and anisotropic spectra have been analyzed by a double-difference method, in conjunction with a least squares fitting procedure, to deduce Raman band components arisen by HDO molecules in the first hydration shell of the constituent ions in the solution. Two band components centered near 2420 and 2640 cm−1 were assigned to the O–D stretching vibrational mode of HDO molecules coordinated to Zn2+ and ClO4−, respectively. These frequencies agree with the infrared double-difference results. Further, it has been found that the relative integrated intensity of the ion-perturbed O–D bands is quite different from that of the ‘bulk’ HDO molecules. The temperature dependence of peak parameters such as the frequency and peak area for Zn2+ and ClO4−-perturbed bands is very small in the temperature range of 26—95 °C, in contrast to a pronounced collapse of the band from bulk HDO molecules at elevated temperatures. This suggests that the local structure around these ions in the solution changes little in the temperature range examined in this study.
Simulation of the Valence X-Ray Photoelectron Spectra of 16 Polymers by the Semiempirical HAM/3 MO Method Using the Model Molecules
Authors: Endo Kazunaka , Inoue Chiaki , Kaneda Yasuo , Aida Masayuki , Kobayashi Naoya , Chong Delano P
Published: July 2006

The HAM/3 method was used to provide a better assignment of the valence X-ray photoelectron spectra of 16 polymers involving nitrogen, oxygen, fluorine, a glucose unit, and a benzene nucleus using the monomer, dimer or trimer model molecules without consideration of the contraction factor of the energy scale. The calculated Al Kα photoelectron spectra were obtained using Gaussian functions of a fixed approximate linewidth, 0.10 Ik and Ik = I′k − WD, where I′k is the vertical ionization potential of each MO and WD is an approximate shift to account for the work function of the sample and other energy (polarization energy and so on) effects. We assumed that WD corresponds to the shift that we must apply before we can compare the calculated spectrum for the single model molecule with the observed spectrum for the solid. The approximate linewidth corresponds to the experimental result that the inner valence spectra are broader. The theoretical spectra showed good agreement with the spectra of the polymers observed between 0—40 eV.
Silica Gel-Bonded Cationic Polyelectrolyte with Ferron as Counterion. Application to Preconcentration or Elimination of Trace Metals
Authors: Prasad Bhim Bali , Sundd Sonu
Published: July 2006

An integral N-based cationic polymer, poly[N-xylylene N,N′-dicyclohexylethylenediammonium dibromide], was immobilized through hydrogen bonding on the surface of silica gel. The chelating ligand, 7-iodo-8-hydroxyquinolino 5-sulfonic acid (Ferron), was subsequently attached to the matrix by ion-exchange method; this renders an extremely stable stationary phase, free from leaching complications, under electrostatic (salt) bond interactions. Analytical characteristics of this sorbent were studied. The optimum sorption conditions for Cu2+, Cd2+, Zn2+, Pb2+, Co2+, Ni2+, and Fe3+ under static and dynamic (column) methods were ascertained. The chelator was found to be selective for the retention of Cu2+, Pb2+, and Fe3+ from multi-element mixtures. The relatively fast kinetics of the sorbent with the time required to reach half of the maximum sorption (t1/2 value 2 min) and the percentage attainment of equilibrium in 2 min (P2 min value > 50%) for most of the heavy metals, excluding Ni2+, reveal the suitability of the chelating resin in column operation, especially in single column ion-chromatography. The specific applications of the sorbent in purification of supporting electrolyte/buffers required for voltammetric detection are also explored.
Molecular Structure of Nitro- and Nitrito-Copper Complexes as Reaction Intermediates in Electrochemical Reduction of Nitrite to Dinitrogen Oxide
Authors: Komeda Nobutoshi , Nagao Hirotaka , Kushi Yoshinori , Adachi Gin-ya , Suzuki Masatatsu , Uehara Akira , Tanaka Koji
Published: July 2006

Copper-nitrito and -nitro isomers, [Cu(ONO)(tpa)]PF6 and [Cu(NO2)(tpa)]PF6 (tpa = tris[(2-pyridyl)methyl]amine) were isolated and the molecular structures were determined by X-ray analysis. [Cu(ONO)(tpa)]PF6 (C18H18N5O2PF6Cu) crystallizes in the monoclinic space group P21/a with a = 13.374(2), b = 14.033(2), c = 13.455(2) Å, β = 119.10(1)°, V = 2206.5(6) Å3, and Z = 4. [Cu(NO2)(tpa)]PF6 (C18H18N5O2PF6Cu) crystallizes in the orthorhombic space group I/ba2 with a = 16.718(3), b = 17.554(3), c = 14.785(3) Å, V = 4338(1) Å3, and Z = 8. Those nitrito- and nitro-complexes exist as an equilibrium mixture in solutions. Electrochemical reduction of NO2− in the presence of [Cu(H2O)(tpa)](ClO4)2 at −0.4 V in H2O (pH 7.0) catalytically produced N2O with concomitant evolution of a small amount of NO via the nitro and nitrito adducts.
Extraction Behavior of Di-μ-oxo-bis[oxomolybdenum(V)] with 2-Methyl-5-octyloxymethyl-8-quinolinol
Authors: Feng Yuqi , Imura Hisanori , Ohashi Kousaburo
Published: July 2006

Binuclear oxomolybdenum(V), Mo2O42+, was quantitatively extracted with 0.01 mol dm−3 2-methyl-5-octyloxymethyl-8-quinolinol (HMO8Q) in chloroform at pH 2.3 and isobutyl methyl ketone at pH 1.0—3.9. To elucidate the extraction equilibrium, the effect of the pH as well as the HMO8Q and molybdenum(V) concentration on the distribution ratio of Mo2O42+ was studied. The extracted complex was found to be Mo2O4(MO8Q)2; the extraction constants (Kex) were determined to be 100.15 and 101.57 in benzene and chloroform, respectively. These values were lower than Kex = 103.26 obtained in the Mo2O42+-5-octyloxymethyl-8-quinolinol–chloroform system, suggesting a steric effect of the methyl group at the 2-position. In the presence of trioctylphosphine oxide (TOPO) a great enhancement of molybdenum(V) extraction was found and could be ascribed to the formation of an adduct, Mo2O4(MO8Q)2(TOPO).
Synthesis and Properties of Linear-Type S-Bridged RhIIINiIIRhIII Trinuclear Complexes with 2-Aminoethanethiolate (aet) or l-Cysteinate (l-cys). Crystal Structure of [Ni{Rh(aet)3}2](NO3)2
Authors: Konno Takumi , Okamoto Ken-ichi
Published: July 2006

The reaction of fac(S)-[Rh(aet)3] with Ni2+ at room temperature gave a linear-type S-bridged RhIIINiIIRhIII trinuclear complex, [Ni{Rh(aet)3}2]2+ (1). A similar reaction of ΔLll-fac(S)-[Rh(l-cys-N,S)3]3− with Ni2+ produced the corresponding trinuclear complex with l-cys ligands, ΔLllΔLll-[Ni{Rh(l-cys-N,S)3}2]4− (ΔLllΔLll-2), retaining the ΔLll configuration of the starting complex. The crystal structure of 1(NO3)2 was determined by X-ray diffraction. [Ni{Rh(aet)3}2](NO3)2·2H2O, chemical formula C12H40N8S6O8NiRh2, crystallizes in the triclinic space group with a = 12.249(3), b = 13.366(4), c = 10.260(2) Å, α = 108.76(1), β = 102.46(1), γ = 101.21(1)°, V = 1488.7(7) Å3, Z = 2, and R = 0.024. In 1 the central NiII atom is situated in a distorted octahedral geometry, coordinated by six thiolato sulfur atoms from the two octahedral fac(S)-[Rh(aet)3] units. The two fac(S)-[Rh(aet)3] units have the same absolute configuration to form the racemic (ΔΔ/ΛΛ) isomer. The optically active ΔΔ and ΛΛ isomers of 1 were derived from ΔΔΔΔ- and ΛΛΛΛ-[{Rh(aet)3}4Zn3(HO)]5+ respectively, by adding excess Ni2+. The electronic absorption spectral behavior of 1 indicated that the intermolecular exchange of the fac(S)-[Rh(aet)3] units occurs in solution, which results in the formation of the ΔΛ (meso) isomer from a 1 : 1 mixture of the ΔΔ and ΛΛ isomers. The chemical properties of the present RhIIINiIIRhIII complexes are discussed in comparison with those of the corresponding CoIIINiIICoIII and RhIIICoIIIRhIII complexes.
Synthesis and Photochromic Properties of Fulgides with a t-Butyl Substituent on the Furyl- or Thienylmethylidene Moiety
Authors: Kiji Jitsuo , Okano Tamon , Kitamura Hitoshi , Yokoyama Yasushi , Kubota Shuji , Kurita Yukio
Published: July 2006

2,6,6-Trimethyl-5-(2,5-dimethyl-3-furyl and -3-thienyl)-3-heptyn-2,5-diols were carbonylated in benzene in the presence of 1 : 1 — Pd(OAc)2/I2 as the catalyst. The reaction at 90 °C under 80 atm of carbon monoxide for 5 h directly gave both E and Z isomers of t-butyl-substituted furyl- or thienyl fulgides. The former had been reported impossible to synthesize by the Stobbe condensation. Similarly, furyl- and thienylfulgides with an isopropyl group were synthesized by this method. The fulgides were isolated by column chromatography in 37—75% yields. Coloring quantum yields of t-butyl-furyl- and -thienylfulgides are 0.79 and 0.73, respectively, which are the greatest in each series of fulgides with the same heteroaromatic ring.
Triethylborane-Induced Radical Cyclization of 1-Allyloxy-2-halosilacyclopentane. Stereoselective Synthesis of 1,3,6-Triols Starting from Silacyclobutane
Authors: Matsumoto Kozo , Miura Katsukiyo , Oshima Koichiro , Utimoto Kiitiro
Published: July 2006

1-Allyloxy-2-bromo-1-phenylsilacyclopentane was synthesized by a ring-enlargement reaction of 1-allyloxy-1-phenylsilacyclobutane with LiCHBr2. The treatment of 1-allyloxy-2-bromo-1-phenylsilacyclopentane with n-Bu3SnH in the presence of a catalytic amount of Et3B provided 2-oxa-1-silabicyclo[3.3.0]octane, which was converted into 1,3,6-triol by an oxidative cleavage of silicon–carbon bonds with H2O2. An intermolecular radical addition of 2-iodosilacyclopentane to acetylenic compounds afforded the corresponding iodoalkenes.
Synthesis, Properties, and Structures of 1,2 : 5,6-Bis(ethylenedithio)pyracylene and Its Radical Cation Salts
Authors: Tani Hiroyuki
Published: July 2006

1,2 : 5,6-Bis(ethylenedithio)pyracylene (2) was synthesized as an example of molecular design for a polyaromatic condensed-type donor with two ethylenedithio groups at the periphery. The redox potential of 2 indicates that this heterocycle is a reversible two-stage redox system with low oxidation potentials, which enhances the donor ability. This donor was readily oxidized to afford single crystal radical cation salts with hexafluorophosphate (PF6−) and triiodide (I3−) by electrocrystallization. The crystal structures of the radical cation salts, (2)3(PF6)2 and (2)2I3, show segregated stacks of donors and anions. The I3 salt presents a two-dimensional sheet along the ab plane similar to I3 salt of bis(ethylenedithio)tetrathiafulvalene.
Solvent Effects on the Solvolysis of p-Nitrobenzyl and 3,5-Bis(trifluoromethyl)benzyl p-Toluenesulfonates
Authors: Fujio Mizue , Susuki Toshihiro , Goto Mutsuo , Tsuji Yutaka , Yatsugi Ken-ichi , Kim Sung Hong , Ahmed Gamal Abdel-Wahab , Tsuno Yuho
Published: July 2006

Solvolysis rates of p-nitrobenzyl and 3,5-bis(trifluoromethyl)benzyl p-toluenesulfonates were determined in a wide variety of solvents. The solvent effects were analyzed based on the Winstein–Grunwald equation. The solvent effect on these deactivated benzyl solvolyses failed to give a single linear correlation with the 2-adamantyl YOTs parameter. The lower response to the solvent polarity and the pattern of dispersion for respective binary solvent series can be interpreted in terms of nucleophilic solvent assistance. The application of the equation gave a low m value of 0.4 and a large l of close to unity for both derivatives. Furthermore, the l value is also comparable to that for ethyl p-toluenesulfonate and even close to that for the methyl derivative, which has generally been defined as the standard SN2 substrate.
Spectroscopic Study of Intracluster Proton Transfer in Small Size Hydrogen-Bonding Clusters of Phenol
Authors: Mikami Naohiko
Published: July 2006

Spectroscopic studies of the hydrogen-bonding clusters of phenol were reviewed with an emphasis of the characterization of the cluster structures involving the proton transfer processes. Two experimental methods which were newly developed for the spectroscopy of the size selected clusters and their ions were described. Trapped ion photodissociation spectroscopy revealed that chromophore alternation occurs in the cluster cations with various proton-accepting molecules, such as NH3 and H2O. The infrared spectroscopy combined with the ionization detection was applied to the spectra of the OH vibrations which characterized the neutral clusters of phenol with water. The spectroscopic evidence of the ion-pair form of the neutral cluster is presented and the possibility of the intracluster acid-base reaction is discussed.
Photovoltaic Properties of Triphenodioxazine and Dichlorotriphenodioxazine
Authors: Yoshida Sadamu , Kozawa Kozo , Uchida Tokiko
Published: July 2006

Photovoltaic behaviors of evaporated thin films of triphenodioxazine (TPDO) and 6,13-dichlorotriphenodioxazine (DClTPDO) were investigated with sandwich-type cells, the configurations of which were Ag/TPDO/Al and Al/DClTPDO/indium–tin oxide (ITO). The action spectra of the short-circuit photocurrent suggest that only the photons absorbed by pigments near the Ag/TPDO interface or the DClTPDO/ITO interface are effective to produce carriers for external circuits. These results mean that Schottky barriers are formed at these interfaces, and that both pigment layers act as n-type semiconductors. Observed effects of oxygen and/or hydrogen gas on the dark conductivity of these pigment films also reflect the n-type semiconducting behavior. The observed electrical behaviors are consistent with the proposed band structures for these two cells, which are estimated from the spectroscopic data.
Semiconductor Photocatalysis: Size Control of Surface-Capped CdS Nanocrystallites and the Quantum Size Effect in Their Photocatalysis
Authors: Yanagida Shozo , Ogata Tomoyuki , Shindo Akihiro , Hosokawa Hiroji , Mori Hirotaro , Sakata Takao , Wada Yuji
Published: July 2006

Size-controlled CdS nanocrystallites were prepared by using thiophenol or hexanethiol as a capping reagent by controlling the ratio of Cd2+ to bis(trimethylsilyl) sulfide (S(TMS)2) as a source of the sulfide ion in reversed micelles. Their solubility and photocatalysis were examined. A series of size-controlled phenyl-capped CdS nanocrystallites catalyze the photoreduction of aromatic ketones in the presence of triethylamine as an electron donor under visible-light irradiation. The photocatalytic activity is affected by the particle size, i.e., the reducing power of the photogenerated electron on CdS nanocrystallites toward the ketones increases with decreasing the particle size. The enhancement of photocatalytic activity observed by reducing the particle size should be ascribed to not only a negative shift of the conduction band edge, but also suppression of the formation of surface defects.
NMR Study on the Electrochemically Generated Triphenylmethyl Anion
Authors: Okano Mitsutoshi , Kugita Tsuyoshi , Ohtani Daijiro , Hamano Hiroshi
Published: July 2006

The 13C and 1H NMR spectra of the triphenylmethyl anion, which had been generated by an electrochemical reduction of triphenylmethane in dimethylformamide at −40 °C, were successfully obtained. An anion having a tetrabutylammonium counter cation had 13C chemical shifts similar to those for an anion with a lithium counter cation. An examination of the 1H NMR spectra revealed that the reaction is a one-electron reaction. Experiments conducted under temperature control showed that the anion is fairly stable below −20 °C. Decomposition of the anion above −20 °C was suggested to be hydrogen abstraction from the β-position of a tetrabutylammonium cation by a triphenylmethyl anion (Hofmann decomposition of the ammonium cation).
Collinear Quantum Calculation of Transition-State Spectrum for the K + NaCl Reaction
Authors: Takayanagi Toshiyuki
Published: July 2006

The laser-induced reaction, K + NaCl + hν → KCl + Na*, has been studied quantum-mechanically, with consideration of only collinear geometries. Laser-dressed equations are numerically solved by the R-matrix propagation method. Quantum reaction probabilities are dominated by many resonances corresponding to the vibrational states of the reaction complex formed in the reaction. The results obtained are compared with surface hopping trajectory calculations. The trajectory surface hopping model fails in predicting the translational energy dependence of the reaction probabilities but a Landau–Zener model is qualitatively correct in the calculation of the laser wavelength dependence of the reaction probabilities. These results suggest that the dynamics of the laser-induced reaction can be divided into two independent processes; the ground state reaction K + NaCl → KCl + Na and the non-adiabatic transition from the laser-dressed ground state to the excited state.
A Voltage-Modified Trajectory Simulation for a State-Selected CH3I Supersonic Beam in an Electrostatic Hexapole Field
Authors: Che Dock-Chil , Ogawa Tetsuya , Ohoyama Hiroshi , Kasai Toshio , Kuwata Keiji
Published: July 2006

The |JKM > state selection of a seeded CH3I/Ar supersonic beam has been achieved using a 2-m electrostatic hexapole field. Several |JKM > states were better resolved than the previous one in a CH3Cl/He supersonic beam. A voltage-modified trajectory simulation was carried out for fitting the observed focusing curve, in which the first-order approximation of the Stark effect was corrected in terms of the hexapole voltage in an empirical formula. A better agreement was found on the peak positions of the focusing curve, and the relative heights of the three peaks suggest that CH3I molecules in the present beam populate among the |JKM > states in a statistical way with a rotational temperature of 3 K.
Conductometric and Volumetric Studies on the Inonization, Hydration, Aggregation, and Coagulation of AOT in Dodecane
Authors: Manabe Masahiro , Ito Tetsuya , Kawamura Hideo , Kinugasa Takumi , Sasaki Yasushi
Published: July 2006

For the sodium l,2-bis(2-ethylhexyloxycarbonyl)ethanesulfonate (AOT)/water/dodecane system, the conductivity (κ) of the solution as well as the partial molar volume of water was determined at 25 °C as a function of the water concentration (CW) at a given concentration of AOT (CA). The value of (κ) increased stepwise through 2 peaks before water-phase separation. Each step was assigned as follows. Upon the initial additions of water at all of the CA’s studied (CA < 0.2 mol kg−1 (dodecane)), κ remained zero, indicating the formation of unionized hydrate, AOT(H2O)2. The critical composition of the solution for reversed micelle formation was estimated to be CA = ca. 0.02 and CW = ca. 0.04 mol kg−1 (dodecane). After hydrate formation, micelles were formed in equilibrium with the hydrate, at which point κ increased abruptly to the 1st peak. Coagulation of the micelles occurred above another critical composition (CA = 0.120 and CW = 0.612 mol kg−1), at which point κ increased with a steep slope up to the 2nd peak. The partial molar volume of water in the same system also indicated the formation of AOT(H2O)2.
Thermochemical Aspects of Partition. A Study on The Novel Hydrophobic Parameters of Multiply-Substituted Benzoic Acids
Authors: Nakamura Katsuhiko , Da Yong-Zhong , Jikihara Takahiro , Fujiwara Hideaki
Published: July 2006

The thermochemical aspects of partition have been measured for multiply-substituted benzoic acids with the intention of disclosing the mode of change of the proposed novel hydrophobic parameters on multiple substitution in the phenyl ring. The substituent hydrophobic parameter (π) has been separated into two terms of enthalpic and entropic nature (πH and πS). It is necessary to take into account the effect of solvation around the hydrogen-bond-participating groups, such as OH, OCH3, and NO2, besides the benzoic CO2H in interpreting the substituent dependency of π, πH and πS. Some Hammett sigma parameters, such as σo(→OH) and σo(→OCH3), which mean the ortho substituent effect to the functional OH and OCH3 groups, respectively, act in a compensating manner to πH and πS, resulting in a vanishing effect on π. These trends are in good conformity with the enthalpy–entropy compensation rule in chemical thermodynamics.
Distribution Study on Electroneutral and Protonated Amino Acids between Water and Nitrobenzene. Determination of the Standard Ion-Transfer Potentials of Protonated Amino Acids
Authors: Takeda Yasuyuki , Ezaki Tatsuya , Kudo Yoshihiro , Matsuda Hiroaki
Published: July 2006

In order to determine the standard ion-transfer potentials () of protonated amino acids (HA+) from water to an organic solvent of moderate dielectric constant, new theoretical equations were derived. Various theoretical predictions were verified experimentally by the solvent extraction of d- and l-amino acids with perchloric and nitric acid from water to nitrobenzene at 25 °C. Furthermore, the distribution constants (KD,A) of the electroneutral d- and l-amino acids (A) between water and nitrobenzene were determined at 25 °C. The amino acids were Ala, Val, Ile, Leu, Met, Phe, Thr, Asn, and Gln. The KD,A values of the d- and l-form of the same amino acid are equal. The same is true for the values. The hydrophilicity of A decreases in the following order: Asn > Thr > Gln > Ala > Val > Met > Ile ≥ Leu > Phe. The same order of decreasing hydrophilicity was also observed for HA+. All of the A and HA+ are much more soluble in water than in nitrobenzene. The A is more lipophilic than the corresponding HA+. Contributions of a methylene group to the distribution Gibbs-free energies of A were compared with those of HA+.
EXAFS Debye–Waller Factor and Ligand Exchange Reaction of Hydrated Metal Complexes
Authors: Miyanaga Takafumi , Sakane Hideto , Watanabe Iwao
Published: July 2006

The EXAFS (Extended X-Ray Absorption Fine Structure) spectra of hydrated transition metal complexes were measured to investigate the relation between the Debye–Waller factor in EXAFS, σ2, and their ligand exchange reaction rate constant, k1, in aqueous solution. A good correlation between these two factors was obtained for various transition metal ions. The relation between σ2 and log k1 is studied theoretically using the Arrhenius theory. The introduction of an anharmonic Morse function as the interaction potential was found to lead to a simple expression connecting σ2 and log k1, which is in accordance with the experimental results. It is also found that k1 correlates not only with σ2 but also a third order cumulant in EXAFS, C3; the greater the k1 value, the greater the increase in C3 with temperature. The behavior of C3 implies that the anharmonicity in the potential of the metal–oxygen interaction must be taken into consideration for the study of the ligand exchange reaction.