bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Electronic Properties of Adsorbed Thiophene on Cu(111) Studied by S K-Edge X-Ray Absorption Spectroscopy
Authors: Imanishi Akihito , Yokoyama Toshihiko , Kitajima Yoshinori , Ohta Toshiaki 
Published: February 2006

Abstract
The surface structure and electronic properties of 0.07 ML thiophene (C4H4S) adsorbed on Cu(111) have been investigated by means of S K-edge X-ray-absorption fine structure measurements. The results are comparatively discussed with the previously studied C4H4S/Cu(100) case. It is found that C4H4S molecules are adsorbed with the molecular plane parallel to the surface, as in the Cu(100) substrate. The S–Cu distance is 2.50 ± 0.02 Å, which is significantly longer than that of Cu(100) (2.42 ± 0.02 Å), while the S–C bond distance is 1.71 ± 0.04 Å, somewhat shorter than the Cu(100) one (1.74 ± 0.04 Å). Correspondingly, a smaller amount of charge transfer of (0.5 ± 0.2) electron from the substrate to the C4H4S π* orbital is estimated compared to the Cu(100) case of (1.0 ± 0.2) electron. These findings indicate a considerably weaker interaction of thiophene with Cu(111) than with Cu(100), due to a more closely packed surface of Cu(111).
Light-Induced Mixed-Valence State of FeII[Fe(CN)5NO]·xH2O
Authors: Morioka Yoshiyuki , Hisamitsu Taka-aki , Inoue Hidenari , Yoshioka Naoki , Tomizawa Hiroshi , Miki Ei-ichi 
Published: February 2006

Abstract
A long-living metastable state is produced in FeII[Fe(CN)5NO]·xH2O by an irradiation of 488 nm light at 200 K. A strong near-infrared band of about 10000 cm−1 and a ν(CN) band at 2070 cm−1 that newly appear in the metastable state point to development of the mixed-valence state analogous to Prussian blue. An iron-to-nitrosyl charge transfer in pentacyanonitrosylferrate(2−), [Fe(CN)5NO]2−, explains the formation of the mixed-valence state, because the charge transfer causes a pair of iron(II) and iron(III) atoms bridged by CN− that has the same local structure as Prussian blue. In addition to the formation of the metastable state, the prolonged irradiation causes an irreversible change of FeII[Fe(CN)5NO]·xH2O and leads to the formation of a photoproduct. The photoproduct also has infrared spectra characteristic of the mixed-valence state. Mössbauer spectra of the photoproduct show that a low-spin iron ion in pentacyanonitrosylferrate(2−) is divalent and a high-spin iron outside of pentacyanonitrosylferrate(2−) is trivalent. Therefore, the charge-transfer between the two non-equivalent iron ions is thought to follow the intra-molecular charge transfer in pentacyanonitrosylferrate(2−).
Negative Second Hyperpolarizability of the Nitronyl Nitroxide Radical
Authors: Nakano Masayoshi , Yamada Satoru , Yamaguchi Kizashi 
Published: February 2006

Abstract
The static second hyperpolarizability (γ) for a symmetric open-shell system including nitroxide radical groups, nitronyl nitroxide radical, has been studied using ab initio molecular-orbital methods, including various electron-correlation effects. This system is predicted to exhibit a negative γ by our classification rule of γ based on symmetric resonance structures with inversible polarization (SRIP). A remarkable electron correlation dependence has been observed in the magnitude and sign of γ, which has been found to be negative by using high-order electron correlation methods. This tendency has also been investigated in terms of the second hyperpolarizability density, which is defined as the third-derivative of the charge density with respect to the applied electric field.
Effects of Hydrogen Bonding and Hydrophobic Interactions on the Ultraviolet Resonance Raman Intensities of Indole Ring Vibrations
Authors: Matsuno Motonori , Takeuchi Hideo 
Published: February 2006

Abstract
UV resonance Raman intensities of indole ring vibrations were examined in solutions of different solvent properties to establish the correlation between the intensity and the environment of the indole ring, the main side-chain component of amino acid tryptophan. Each of the Raman bands that are enhanced through resonance with the Bb electronic transition gives the highest intensity when the indole NH site is hydrogen-bonded with a proton acceptor in hydrophobic environments. On the other hand, the Raman bands that gain intensity through resonance with the La transition are most enhanced when the indole ring is not hydrogen-bonded. Although these changes in Raman intensity result from small red and blue shifts of the Bb and La absorptions, respectively, the Raman intensity changes are much greater than the changes in UV absorption spectra. UV resonance Raman intensities are thus expected to be useful markers of hydrogen bonding and hydrophobic interactions of tryptophan residues in proteins.
Extraction, Separation, and Spectrophotometric Determination of Tellurium(IV) with 1-(4-Bromophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol
Authors: Kolekar G B , Anuse M A 
Published: February 2006

Abstract
A method is proposed for the extraction, separation and spectrophotometric determination of trace levels of tellurium(IV) from hydrochloric acid media with 1-(4-bromophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol (4-bromoPTPT) in chloroform. The yellow-colored complex absorbs at 440 nm and the system obeys Beer’s law in the 1—15 ppm concentration range. The molar absorptivity and Sandell’s sensitivity are 8.1 × 103 dm3 mol−1 cm−1 and 16 ng cm−2, respectively. The probable composition of the extracted species is TeL2. The interference of various ions was studied. Various parameters, such as the effects of the acidity, reagent concentration, equilibration time etc., have been established for the extractive spectrophotometric determination of tellurium(IV). The method has been applied for the determination of tellurium(IV) in various synthetic samples corresponding to alloys, and provides for the binary separation of tellurium(IV) from lead, bismuth, copper, gold, and antimony. It is also applicable for the simultaneous determination of selenium(IV) and tellurium(IV). The method is accurate, simple, rapid, and selective, and the overall process of extraction and determination takes about 15 to 20 min.
Synthesis and Characterization of Ruthenium Terpyridine Dioxolene Complexes: Resonance Equilibrium between RuIII–Catechol and RuII–Semiquinone Forms
Authors: Kurihara Masato , Daniele Stephane , Tsuge Kiyoshi , Sugimoto Hideki , Tanaka Koji 
Published: February 2006

Abstract
A series of [RuX(dioxolene)(terpy)] (terpy = terpyridine; X = Cl, OAc) and one-electron oxidized complexes were prepared. The molecular structures of [RuCl(O2C6H2-3,5-Bu2)(terpy)] (1) and [Ru(OAc)(O2C6H4)(terpy)] (3) were determined by X-ray crystallography. Crystal data for 1: monoclinic, space group P21/c, Z = 8, a = 11.548(1), b = 18.224(5), c = 30.002(8) Å, β = 96.51(2)°, and R = 0.077 (Rw = 0.068). Crystal data for 3: monoclinic, space group C2/c, Z = 8, a = 13.355(5), b = 12.131(4), c = 26.645(4) Å, β = 92.46(2)°, and R = 0.041 (Rw = 0.041). Although the binding mode of O2C6H2-3,5-Bu2 to Ru was not determined by the molecular structure of 1, the carbon–oxygen and carbon–carbon bond lengths of O2C6H4 in 3 were consistent with those of catecholato ligands. Electronic absorption spectra of [RuX(dioxolene)(terpy)] were explained by the electronic structure of [RuIIX(semiquinone)(terpy)] rather than [RuIIIX(catecholato)(terpy)], while the reverse assignment was deduced from the IR spectra. Moreover, ESR spectra showed hyper-fine structures due to the contribution of semiquinone superimposed on an axial pattern of the Ru(III) center, indicating a resonance equilibrium between [RuIIX(semiquinone)(terpy)] and [RuX(dioxolene)(terpy)].
Substitution of Cl Atom in (2-Chloromethylallyl)palladium Complexes with Soft and Hard Nucleophiles
Authors: Watanabe Saisuke , Hiraike Hiroshi , Kurosawa Hideo 
Published: February 2006

Abstract
[Pd{η3-CH2C(CH2Cl)CH2}(μ-SPh)]2 is spontaneously transformed, in MeCN, into [Pd{η3-CH2C(CH2SPh)CH2}(Cl)]2, which has a novel thioether-bridged dimeric structure. This transformation is suggested to proceed by an attack of the thiolate anion at the methylene carbon bearing a Cl substituent of an ionic intermediate, [Pd{η3-CH2C(CH2Cl)CH2}(MeCN)2]+. [Pd{η3-CH2C(CR2Cl)CH2}(μ-SPh)]2 (R = H, Me) reacts with PPh3 to give [Pd{η3-CH2C(CH2SPh)CR2}(Cl)(PPh3)]. This transformation proceeds via an attack of the thiolate anion at the terminal allyl carbon of an ionic intermediate, [Pd{η3-CH2C(CH2Cl)CH2}(PPh3)2]+, to give 2-phenylthiomethylallyl chloride, which undergoes an oxidative addition to the resulting Pd(0) complexes. [Pd{η3-CH2C(CR2Cl)CH2}(Cl)(PPh3)] (R = H, Me) reacts with Bu3SnCH=CH2 to give [Pd{η3-CH2C(CH2CH=CH2)CR2}(Cl)(PPh3)] through a reductive elimination–oxidative addition sequence, starting from an intermediate, [Pd{η3-CH2C(CR2Cl)CH2}(CH=CH2)(PPh3)].
Kinetics and Mechanism of the Copper(II)-Catalyzed Oxidation of the Iodide Ion by Chromate(VI) Ion in an Aqueous Solution
Authors: Kimura Masaru , Ikawa Rie , Shiota Yuko , Tsukahara Keiichi 
Published: February 2006

Abstract
Although the chromate(VI) ions, CrO42− and HCrO4−, which are described as CrVI herein, could hardly oxidize the iodide ion to iodine above pH 3.0, it was catalytically oxidized by adding traces of copper(II) ion. When a copper(II) solution of 10−7—10−5 mol dm−3 was mixed with an iodide solution, after a fast formation of iodine, the iodine concentration remained constant. After such an iodine formation had occurred, if a chromate solution was added into the reacting mixture, the iodine began to form again in accordance with a rate law of 2/3(d[I2]/dt) = −d[CrVI]/dt = k[CuI][CuVI], in which [CuI] is the steady-state concentration in the chain cycle CuI+/CuI. The rate of the chain reaction was independent of the time to add chromate, and the formation of iodine I2 (or triiodide ion I3−) stopped at the time when all of the chromate was consumed by the chain reaction. The stoichiometry was 3I− + CrVI → 1.5I2 + CrIII. The iodine formation was extremely inhibited by the presence of either radical scavengers or complex-forming reagents as well as by increasing pH. Although addition of alcohols to the reaction mixture extremely accelerated the iodine formation before adding chromate, it hardly affected on this process after the addition of chromate. The reaction mechanisms are presented in order to account for the observed results.
Use of a Sacrificial Aluminum Anode in the Acylation of Some Olefins
Authors: Vukicevic Rastko D , Joksovic Ljubinka , Konstantinovic Stanimir , Markovic Zoran , Mihailovic Mihailo Lj 
Published: February 2006

Abstract
The acylation of some alicyclic and aliphatic alkenes by the electrochemical generation of a catalyst using a sacrificial aluminum anode was investigated. Substrates were electrolyzed in a dichloromethane solution of an appropriate electrolyte (tetraalkylammonium salts) in the presence of an acylating agent (acetyl chloride or anhydride). Thus, unsubstituted cycloalkenes, namely cyclohexene and cycloheptene, gave by that reaction conjugated ketones, i.e. the corresponding 1-acetylcycloalkenes, as the only unsaturated carbonyl compounds in moderate-to-good yields. Under the same reaction conditions their 1-methyl derivatives gave mixtures of the corresponding conjugated and β,γ-unsaturated isomeric ketones in which unconjugated compounds predominate. In both cases unsaturated ketones were accompanied by different amounts of side products. Terminal aliphatic alkenes (1-hexene, 1-heptene, and 1-dodecene) afforded only conjugated a ketone with a normal skeleton, but in lower yields. The acylation of cyclohexene was studied in more detail, altering the reaction conditions by changing the reaction temperature, the supporting electrolyte, the acylating agent and the electrochemical cell. Mechanistic considerations were made on the basis of the products distribution and some theoretical calculations being made by the MOPAC program package (version 7.0).
Dinitrogen Tetraoxide Complexes of Iron(III) and Copper(II) as Efficient and Mild Reagents for Oxidation of Hydroxy Compounds
Authors: Iranpoor Nasser , Firouzabadi Habib , Zolfigol Mohammad Ali 
Published: February 2006

Abstract
Fe(NO3)3·1.5N2O4 is a highly efficient reagent for the oxidation of various classes of hydroxy compounds in dichloromethane at room temperature, or in the absence of solvent. Cu(NO3)2·N2O4 oxidizes different hydroxy compounds in refluxing carbon tetrachloride and is a highly selective reagent for oxidation of primary benzylic alcohols in refluxing EtOAc.
Photodimerization of trans-Cinnamic Acid in a Bilayer of Dimethyldioctadecylammonium Bromide
Authors: Nakamura Tomotaka , Takagi Katsuhiko , Sawaki Yasuhiko 
Published: February 2006

Abstract
The photochemistry of trans-cinnamic acid (trans-1) was studied in a cast film of dimethyldioctadecylammonium bromide (2), deposited from aqueous dispersions as a crystalline solid by the spontaneous vaporization of water. UV irradiation of the cast film resulted in a highly selective formation of the syn-Head-to-Head dimer, suggesting a parallel orientation of trans-1 within a bilayer film. Analyses with X-ray diffraction, differential scanning calorimetry, and IR spectra revealed the formation of a bilayer structure of 2 in which the molecules of trans-1 are dissolved to interact with 2 of the polar head groups. The photoreactivity of trans-1 in the cast film was found to be dramatically suppressed by heating at 40—60 °C, which is attributed to an improvement in the crystallinity of the bilayer.
Dimensiosolvatic Effects. IV. Topomerization in Alkyl α-Chlorobenzyl Ethers and Insights into Mechanisms of Their Thermolyses
Authors: Oki Michinori , Ikeda Hiroshi , Miyake Hiromichi , Mishima Hirohito , Toyota Shinji 
Published: February 2006

Abstract
Rates of topomerization in α-chlorobenzyl ethyl ether and its p-methyl as well as p-methoxy derivatives were determined in various solvents by the dynamic NMR method. The topomerization process was deduced to be ionic because the rates are enhanced in polar solvents as well as by electron-donating substituents. Concentration dependence study of the topomerization in carbon tetrachloride revealed that the observed process is unimolecular; the rates are not affected by concentration of the substrate if the concentration is lower than 0.2 mol L−1. The rates of topomerization are smaller for solutions in bulky solvents than in small solvents, the effects being clear for compounds with electron-donating substituents. The key feature of the kinetic parameters is that the entropy of activation is large and negative for all the solvents examined. The reaction mechanisms are discussed on the basis of these data. The effects of the molecular size of the solvent, dimensiosolvatic effects, are attributed to the effectiveness of the solvation in the formation of ion pairs. The results show that thermolyses of alkyl α-chlorobenzyl ethers are much slower reactions than the ionization. The nature of the reaction is discussed.
Synthesis of the Hexagonal Form of Tungsten Trioxide from Peroxopolytungstate via Ammonium Paratungstate Decahydrate
Authors: Han Wonchull , Hibino Mitsuhiro , Kudo Tetsuichi 
Published: February 2006

Abstract
Two types of crystalline (NH4)10[H2W12O42]·10H2O were precipitated in sequence when an ammonia solution of peroxopolytungstate was neutralized with hydrochloric acid. It was found by X-ray diffraction that one of them is an unknown phase of ammonium paratungstate, and the other is the reported one. Heating the former, it turned directly to common triclinic WO3. On the other hand, the latter yielded the hexagonal form of WO3 (h-WO3) in the temperature range 350—370 °C. This is a new synthetic method of h-WO3, though the final precursor is a known compound. The color of h-WO3 thus formed was pale yellow and contained a small amount of residual ammonia (N/W = 0.017 in molar ratio). Its crystallographic c-axis (7.689 Å) was shorter than than the reported value (7.798 Å) for the same WO3 phase synthesized from 3WO3·H2O.
Comparison of Catalytic Decomposition of Dinitrogen Oxide and Nitrogen Monoxide over Cu/ZSM-5 and Cu/Y Zeolites
Authors: Wang Jie , Mizuno Noritaka , Misono Makoto 
Published: February 2006

Abstract
A comparative study of NO and N2O decomposition over Cu/ZSM-5 and Cu/Y zeolites with various Cu loading levels has been carried out at 523—823 K. The Arrenhius plot of NO decomposition tended to level off above 773 K, as reported in the literature, while that of N2O decomposition was linear. It was noted that the reactivity of N2O decomposition rose much more sharply than that of NO decomposition with an increase in the level of the copper-ion exchange. The implications of these results on the reaction mechanism were discussed. In addition, the adsorption of NO on Cu/ZSM-5 and Cu/Y was measured by IR at 173—373 K and the results were compared with the catalytic decomposition results.
Reaction of Nitrides of Molybdenum and Tungsten with Hydrogen Peroxide to Form Inorganic Proton Conductors
Authors: Nakajima Hitoshi , Tanaka Hitoshi , Hibino Mitsuhiro , Kudo Tetsuichi , Mizuno Noritaka 
Published: February 2006

Abstract
Reactions of nitrides of Mo, W, V, and Ti with hydrogen peroxide, especially Mo and W, were investigated. The reactions were characterized by elemental analysis, NMR, IR, Raman, XPS, TOF mass, and TG/DTA spectroscopy and titration of ammonia and peroxo group. The major oxometalate species in reaction solution for Mo and W were [MoO(O2)2(OOH)]22− and [W2O3(O2)4(H2O)2]2−, respectively. As for the nitrogen-containing species, ammonium ions were initially formed, followed by the nitrate ions. Protons formed by the reaction take part in the formation of ammonia. The removal of unreacted hydrogen peroxide and the evaporation to dryness resulted in the formation of isopolymetalates. The peroxooctamolybdate, peroxododecatungstate, and decavanadate were suggested to be formed. Among them, the peroxopolytungstate was the most thermally stable and provided homogeneous thin films. The films showed protonic conductivity and the logarithm of conductivity changed linearly with the relative humidity or the inverse of the temperature.
Preparation of Copolymeric Gels Composed of Polydimethylsiloxane and Polyethylene Oxide Network Chains and Their Specific Characteristics
Authors: Kohjiya Shinzo , Tsubata Hideki , Urayama Kenji 
Published: February 2006

Abstract
Copolymeric networks composed of two chemically different network chains, polydimethylsiloxane (PDMS) and polyethylene oxide (PEO), are prepared by the two synthetic methods: (1) Vinyl-terminated PDMS and PEO are end-linked with the multi-functional silane compounds; (2) Vinyl-terminated PEO and silyl-terminated PDMS are end-linked with each other. The compositions in the resulting two-component networks are determined by two independent methods: 1H NMR analysis of the extracted unreacted materials and thermogravimetric analysis of the network samples. The appearances of the copolymeric networks are transparent. The differential scanning calorimetry and dynamic mechanical analysis show that the copolymeric networks have the microphase separated structures composed of PDMS and PEO phases. Swelling experiments in various solvents clearly indicates the amphiphilic character of the copolymeric networks. The Li-doped copolymeric networks, which are obtained by immersing the gels in LiClO4, exhibit conductivity of the order of 10−6 S cm−1 at room temperature. The temperature dependence of the conductivity obeys the William–Ferry–Landel equation based on the free volume theory.
Structure-Reactivity Relationship in Allyl and 2-Propynyl Complexes of Group 10 Metals Relevant to Homogeneous Catalysis
Authors: Kurosawa Hideo , Ogoshi Sensuke 
Published: February 2006

Abstract
Recent developments in the understanding of some fundamental reactions undergone by group 10 metal allyl and propargyl (2-propynyl) complexes are described. Emphasis was placed on the bonding-reactivity relationship of these complexes which are relevant as key intermediate models in transition metal catalyzed transformations of allylic and propargylic substrates as well as related transformations involving unsaturated hydrocarbons. The specific complexes surveyed include group 10 metal complexes of allyl and propargyl ligands bound to the metal both in η1- and η3-fashions. Specific reactions to be discussed include oxidative addition, nucleophilic and electrophilic attack at the allyl or propargyl ligands, and reductive elimination of the allyl ligands.
Synthesis and Properties of Photochromic Diarylethenes with Heterocyclic Aryl Groups
Authors: Irie Masahiro , Uchida Kingo 
Published: February 2006

Abstract
A new class of thermally irreversible and fatigue resistant photochromic molecules named diarylethenes has been developed. Theoretical consideration based on the state correlation diagrams of electrocyclic reactions revealed that the thermal irreversibility is attained by introducing aryl groups that have low aromatic stabilization energy. According to the molecular design principle thermally irreversible photochromic diarylethenes having heterocyclic five-membered rings, such as furan, thiophene (or benzothiophene), or thiazole rings, have been newly synthesized. Among them, diarylethenes having benzothiophene aryl groups showed an excellent fatigue resistant property. They underwent photochromic cycles more than 1.0 × 104 times. The absorption maxima of the closed-ring forms varied from 425 to 828 nm depending on the aryl groups, substituents of the aryl groups, and the substitution position of the aryl groups to the ethane moiety. The response times of both cyclization and ring-opening reactions were less than 10 ps in solution as well as in a crystalline phase. The chemical and thermal control of photochromic reactivity was achieved by introducing intramolecular hydrogen bonding groups or oligothiophene aryl groups to the diarylethenes. Some of the dithienylperfluorocyclopentene derivatives were found to show photochromic reactivity in the crystalline phase. The reactivity was dependent on the conformation and molecular packing in the crystals.
Electrical and Structural Properties and Phase Diagram of a Molecular Superconductor β-[(CH3)4N][Pd(dmit)2]2
Authors: Kobayashi Akiko , Miyamoto Akihito , Kato Reizo , Sato Akane , Kobayashi Hayao 
Published: February 2006

Abstract
β-[(CH3)4N][Pd(dmit)2]2 is isomorphic to [(CH3)4N][Ni(dmit)2]2, which is the first pure π acceptor molecular conductor exhibiting a superconducting transition. The crystal structure at low temperature, pressure dependence of the resistivity and the magnetic susceptibility of β-[(CH3)4N][Pd(dmit)2]2 were examined. The general features of the phase diagram of β-[(CH3)4N][Pd(dmit)2]2 resemble those of the organic superconductors. At ambient pressure, the resistivity increases gradually with lowering temperature. A superconducting transition was observed at 6—9 kbar. The highest Tc was 6.5 K. Between 5 and 6.3 kbar, a characteristic rapid resistivity decrease was observed at the small temperature range above the offset temperature of the superconducting transition. Although the resistivity is not zero, this temperature region can be regarded as a “pre-superconducting region.” Above 9 kbar the metallic state is stabilized down to low temperature. Above 5 kbar, most of the crystals exhibited resistivity anomalies around 60 K, which may be ascribed to the metal-insulator transition of the domains with α-type structure (α-[(CH3)4N][Pd(dmit)2]2), which became mixed in with the crystals of β-[(CH3)4N][Pd(dmit)2]2. The resistivity data of the highly conducting state were very noisy in the pressure range where the superconducting transition could be observed.