bluuebunny/crossref_metadata_2025_split huggingface dataset:
4,7,11,14,18,21-Hexa-t-butyltribenzodecacyclenyl Radical: A Six-Stage Amphoteric Redox System
Authors: Kubo Takashi , Yamamoto Kagetoshi , Nakasuji Kazuhiro , Takui Takeji , Murata Ichiro 
Published: December 2002

Abstract
A six-stage amphoteric redox hydrocarbon radical 3• containing three phenalenyl units was prepared. Cyclic voltammogram of 3• exhibits six reversible redox waves with a small numerical sum (E1sum) of first oxidation (E1ox) and reduction (E1red) potentials. Some redox states of 3• were successfully generated from the neutral 3• and characterized by NMR, ESR, UV-vis-NIR spectroscopies, and theoretical calculations. The spin and the charges are delocalized over the entire C3 molecule of 33+, 3•2+, 3•, and 33−. On the other hand, 3•2− shows the localization of the spin on one phenalenyl unit; these results are consistent with the distorted C2 structure caused by the Jahn-Teller effect.
Crystal and Molecular Structures of 2-Dodecyl-7,7,8,8-tetracyanoquinodimethane
Authors: Terashita Shin-ichi , Suzuki Takashi , Nakatsu Kazumi , Iriyama Keiji , Ozaki Yukihiro 
Published: December 2002

Abstract
To develop a possible structural model for molecular arrangement in Langmuir–Blodgett (LB) films of 2-alkyl-7,7,8,8-tetracyanoquinodimethane (alkyl-TCNQ) the molecular and crystal structures of 2-dodecyl-7,7,8,8-tetracyanoquinodimethane (dodecyl-TCNQ) have been determined by X-ray single-crystal analysis. The compound crystallizes in the triclinic space group P1- with Z = 2. The molecule consists of the planar TCNQ moiety and the dodecyl chain having all-trans conformation. In the crystals the TCNQ fragments make a stacking structure in a head-to-head manner across the centers of symmetry to form a double layer of TCNQ groups. The dodecyl chains protrude oppositely from the TCNQ layers and are assembled to form a close-packed layer, being interdigitated with each other. In this way, the TCNQ moieties and the dodecyl groups form layers alternately. This molecular arrangement in the crystal provides new insight into the structure of the LB films of alkyl-TCNQ.
Voltammetric Behavior of Menadione in Surfactant Media and Its Determination in Sodium Dodecyl Sulfate Surfactant System
Authors: Jaiswal Priya V , Ijeri Vijaykumar S , Srivastava Ashwini K 
Published: December 2002

Abstract
Cyclic voltammograms at the carbon paste electrode were recorded for menadione or vitamin K3 dissolved in aqueous surfactant solutions above their critical micellization concentrations. The reduction and oxidation potentials of the vitamin were found to be different in different surfactants and were found also to vary with change in the surfactant concentration. Differential pulse voltammetric technique was utilized for the determination of the vitamin in the above surfactant systems. The limit of detection and the linear range varied in different surfactants, the lowest being in the sodium dodecyl sulfate surfactant systems. Similarly, cyclic voltammograms were recorded for ascorbic acid and the effect of various surfactants on its oxidation peak was also studied. Simultaneous determination of menadione, ascorbic acid, and riboflavin was attempted. Synthetically prepared samples were analyzed and gave satisfactory results.
Sol–Gel Prepared Sn–Al2O3 Catalysts for the Selective Reduction of NO with Propene
Authors: Haneda Masaaki , Ohzu Shin-ichi , Kintaichi Yoshiaki , Shimizu Ken-ichi , Shibata Junji , Yoshida Hisao , Hamada Hideaki 
Published: December 2002

Abstract
Catalytic reduction of NO by propene in the presence of oxygen was studied over Sn–Al2O3 prepared by the sol–gel method. The maximum NO conversion did not change much with Sn loading (1–5 wt%), although the effective temperature window for NO reduction shifted to lower temperatures with increasing Sn loading. X-ray diffraction (XRD), and X-ray absorption spectroscopy (XANES and EXAFS) revealed the formation of finely-divided SnO2 crystallites in Sn–Al2O3. It was deduced that not only the surface vicinity of supported SnO2, which can be reduced at lower temperatures, but also alumina participate in the reaction as catalytically active sites. The catalytic performance of Sn–Al2O3 was markedly improved by an H2O treatment at 873 K. The H2O treatment did not affect the crystal structure of the catalysts and the dispersion state of supported SnO2, but promoted the removal of Cl− ions, which originated from the SnCl4 precursor. The activity enhancement by the H2O treatment was accounted for by an increase in the surface SnO2 concentration as active sites and by the modification of oxo-tin species as active sites. Reaction kinetic studies suggested that NO reduction on the fresh and the H2O-treated catalysts proceeds through the same reaction pathway in which the surface NOx adspecies and C3H6-derived species play an important role for NO reduction.
Binding of Phenol Derivatives to Nonionic Surfactant Micelles as Studied by Capillary Zone Electrophoresis
Authors: Takayanagi Toshio , Motomizu Shoji 
Published: December 2002

Abstract
Binding constants of 13 kinds of phenols as neutral and anionic species to nonionic surfactant micelles were determined using their mobility changes in capillary zone electrophoresis. Electrophoretic mobility of the phenolate ions at alkaline regions decreased with increasing the concentrations of nonionic surfactant. Analyzing such mobility decreases provided the binding constants of the ions (KB,A). The KB,A values are larger in the anions which are more hydrophobic. Binding constants of the phenols as their neutral species to nonionic surfactant micelles (KB,HA) were also determined by using the difference in acid dissociation constants between in the absence of and in the presence of nonionic surfactant micelles: in the presence of the surfactant, the apparent pKa values became larger, which indicates that the neutral species are more likely bound to the micelles. The KB,A and KB,HA values determined were compared with each other on the basis of hydrophobicity, basicity, and position of the substituents.
Comparative Structural, Spectroscopic and Redox Studies of Isostructural Complexes of Ruthenium(III), Osmium(III), and Rhenium(III): cis-Dichloro Complexes Containing Tris(2-pyridylmethyl)amine and Its 6-Methylpyridyl Derivative
Authors: Sugimoto Hideki , Matsunami Chikako , Koshi Chikako , Yamasaki Mikio , Umakoshi Keisuke , Sasaki Yoichi 
Published: December 2002

Abstract
A series of the complexes, [MCl2(L)]+ (M = Ru, L = tpa (1), Metpa (1a); M = Os, L = tpa (2); M = Re, L = tpa (3), Metpa (3a); tpa = tris(2-pyridylmethyl)amine, Metpa = ((6-methyl-2-pyridylmethyl)bis(2-pyridylmethyl)amine), have been prepared. X-ray structural analyses of the series of isostructural complexes [1a]BF4, [2]PF6·C2H5OC2H5, [3]BF4, and [3a]BF4 together with that of the previously reported [1]ClO4, made detailed comparison of structure parameters for Ru, Os, and Re possible. The corresponding metal-ligand bond lengths which are similar between [1]ClO4 and [2]PF6·C2H5OC2H5 are considerably longer (0.02–0.03 Å) for [3]BF4, especially in the case of M–N(tertially nitrogen) (0.06 Å) bond. The M–Cl(trans to tertially nitrogen) bond lengths do not follow this trend. Introduction of the methyl group causes significant influence on the structure of the Re(III) complex: increase in bond length of Re–N(methylated pyridyl) and Re–N(pyridyl) trans to it. Bond angles around the metal ion related to the methylated pyridyl group are also significantly affected. Such steric influence is not clear for [1a]BF4 due to disorder of methyl group. The redox waves of the two processes, M(II/III) and M(III/IV), are observed for all the complexes. The redox potentials for individual process follow the order: Ru &lt; Os &lt; Re (from negative to positive), the difference being ca. 0.5 V. The difference in the two consecutive redox potentials is almost identical (ca. 1.6 V) among the three metal ions, suggesting that the stabilities of the trivalent oxidation state over di- and tetravalent ones are not affected by the different d-electron configurations. Strong visible MLCT bands are observed only for the rhenium(III) complexes. This may be due to higher d-orbital energies of the rhenium(III) ion as evidenced from the redox potentials.
Synthesis, Structures and Characterization of the Dinuclear Nickel(II) Complexes Containing N,N,N′,N′-Tetrakis[(1-ethyl-2-benzimidzolyl)- methyl]-2-hydroxy-1,3-diaminopropane and their Urea Complexes Relevant to the Urease Active Site
Authors: Yamane Heitaro , Nakao Yasuo , Kawabe Satoru , Xie Yong , Kanehisa Nobuko , Kai Yasushi , Kinoshita Masashi , Mori Wasuke , Hayashi Yasuhisa 
Published: December 2002

Abstract
New dinuclear nickel(II) complexes ([Ni2(L-Et)(CH2ClCOO)(H2O)2](ClO4)2·H2O (3), [Ni2(L-Et)(CCl3COO)(H2O)2](ClO4)2·H2O (4), [Ni2(L-Et)(CF3COO)(H2O)2](ClO4)2·3H2O (5)) and their urea complexes ([Ni2(L-Et)(RCOO)(ur)(H2O)](ClO4)2 (R = CH3 (6), C2H5 (7), CH2Cl (8), CCl3 (9), CF3 (10)) (HL-Et = N,N,N′,N′-tetrakis[(1-ethyl-2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane and ur = urea) have been prepared in order to model the active site urease. These complexes were characterized by IR and UV-vis spectra, and by magnetic susceptibilities. The crystal structures of the complexes [Ni2(L-Et)(CH2ClCOO)(CH3OH)2](ClO4)2 (3′) and [Ni2(L-Et)(OAc)(ur)(H2O)](ClO4)2· 2(CH3)2CO (OAc = acetate) (6′) were determined by X-ray crystallography. In the cation of 6′, the two nickel(II) ions are bridged by an alkoxo of L-Et− and an acetato, and a monodentate urea molecule is attached to a nickel(II) through its oxygen atom. Variable temperature magnetic susceptibility measurements of the urea complexes 6, 8, and 10 show an antiferromagnetic exchange coupling (2J = −15.8, −8.0, and −13.3 cm−1 for 6, 8, and 10, respectively, Hamiltonian H = −2JS1·S2 with S1 = S2 = 1) between two nickel(II) ions.
Structure and Magnetic Property of Ru(II,III) Dimer Axially Coordinated by the Niroxide Radical and Water [Ru2(O2CCMe3)4(nitph)(H2O)]BF4, nitph = 2-Phenyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide
Authors: Sayama Yasuyoshi , Handa Makoto , Mikuriya Masahiro , Hiromitsu Ichiro , Kasuga Kuninobu 
Published: December 2002

Abstract
A ruthenium(II,III) pivalate dimer axially coordinated by a nitroxide radical and a water molecule, [Ru2(O2CC-Me3)4(nitph)(H2O)]BF4 (nitph = 2-phenyl-4,4,5, 5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-N-oxide), has been prepared and characterized. The magnetic interaction between the Ru(II,III) core and the radical through the coordinated N–O group was estimated to be J = −45 cm−1.
Effect of Palladium Dispersion on the Enantioselective Hydrogenation of α,β-Unsaturated Acids with Modified Pd/TiO2 Catalysts
Authors: Nitta Yuriko , Kubota Takeshi , Okamoto Yasuaki 
Published: December 2002

Abstract
The enantioselective hydrogenation of the C=C double bonds in (E)-2-methyl-2-butenoic acid, (E)-2-methyl-2-pentenoic acid, and (E)-2,3-diphenyl-2-propenoic acid has been studied using cinchonidine-modified Pd/TiO2 catalysts with different metal loadings of between 0.5 to 30 wt%. For all of the substrates examined, those catalysts with degrees of Pd dispersion lower than 0.2 have been shown to be rather detrimental for obtaining a high enantioselectivity, as opposed to the tendencies reported for the hydrogenations of keto esters with modified Pt and Ni systems. The hydrogenations of the aliphatic acids are almost structure insensitive with a slight decrease in the enantioselectivity at Pd dispersions lower than 0.2, which is in great contrast to the hydrogenation of the aromatic acid. A similar difference in the structure sensitivity has been observed with catalysts modified by a larger modifier, (−)-dihydroapovincaminic acid ethyl ester. The influence of the substrate structure on the adsorption mode and the strength of the modifier-substrate complex is discussed in relation to the size of the Pd ensemble on the catalyst surface.
Conformational Mobility of the Bridged Calix[6]arenes with Allyl and Ethyl Groups at the Lower Rim
Authors: Akine Shigehisa , Goto Kei , Kawashima Takayuki 
Published: December 2002

Abstract
The conformational mobility of the bridged calix[6]arenes with allyl and ethyl groups at the lower rim was investigated. Allylation of the tetrahydroxy compounds afforded two isomers: 5a (cone) and 5b (1,2,3-alternate), which were separated by silica-gel chromatography. These isomers underwent slow isomerization at room temperature with a half-life time of about 2 weeks. On the other hand, the ethyl derivatives 6–9 were found to exist as mixtures of conformational isomers in solution; they were observed independently on the NMR time-scale but were inseparable on the laboratory time-scale. The ratios of two isomers of 6–9 depended on the functionality on the bridging unit, the effects of which were investigated by molecular mechanics calculations. In the crystalline state, the ethyl derivative 6 with a bromo functionality was found to take the 1,2,3-alternate conformation, while compound 7 with an ethynyl group adopted the cone conformation.
Efficient Dimerization of Formic Acid in Aqueous Solution Induced by Ar-Arc Plasma
Authors: Harada Kaoru , Ito Yoshimi , Wada Toshinori , Munegumi Toratane 
Published: December 2002

Abstract
Introduction of argon-arc plasma into an aqueous solution of formic acid resulted in the formation of oxalic acid. The reaction conditions for the dimerization were studied. The maximum yield of oxalic acid reached 47–50% when the reaction was carried out using sodium formate or calcium formate. Dimerization of acetic acid was also examined.
Observation of the Pathway from Lysine to the Isoprenoidal Lipid of Halophilic Archaea, Halobacterium halobium and Natrinema pallidum, Using Regiospecifically Deuterated Lysine
Authors: Yamauchi Noriaki , Endoh Satoshi , Kato Keiko , Murae Tatsushi 
Published: December 2002

Abstract
We examined the incorporation of lysine into archaeal isoprenoidal lipids of halophilic archaea, Natrinema pallidum and Halobacterium halobium using two regiospecifically deuterium-labeled derivatives, [3,3-2H2] and [6,6-2H2]lysines. The two deuterated lysines were synthesized, and the incorporation of deuterium to the lipid core was defined by 2H NMR. The results revealed that lysine is degraded to crotonoyl-CoA by the decarboxylation of carboxylate in the metabolism of halophilic archaea, much like the metabolism of lysine in aerobic bacteria; the process converts lysine to isoprenoidal lipids via the mevalonate pathway through glutaryl-CoA, crotonoyl-CoA, and acetoacetyl-CoA.
Molecular Dynamics Simulation of Neocarrabiose 2,4′-Bis(sulfate) and Carrabiose 4′,2-Bis(sulfate) as Building Blocks of ι-Carrageenan in Water
Authors: Ueda Kazuyoshi , Iwama Koji , Nakayama Haruo 
Published: December 2002

Abstract
Molecular mechanics and molecular dynamics simulations were performed on two types of disaccharides, neocarrabiose 2,4′-bis(sulfate) and carrabiose 4′,2-bis(sulfate), which are building blocks of ι-carrageenan. Although the conformation and potential-energy surfaces of these disaccharides have been investigated by several researchers, all of them were analyzed using a vacuum calculation. To investigate the conformational behavior of these molecules in water, we performed a molecular dynamics simulation with the presence of explicit water molecules and counter ions around the disaccharides. The trajectories of the glycosidic dihedral angles in the water simulation reproduced the potential-energy surface calculated not with a dielectric constant of 80, but with 1. The electrostatic force was found to act so as to restrict the allowed area of the potential-energy surfaces. The most stable conformation of neocarrabiose 2,4′-bis(sulfate) is φ = 162, ψ = 174. Although the global minimum conformation of carrabiose 4′,2-bis(sulfate) is at A1 (φ = 176° and ψ = −166°), the molecular dynamics simulation in water suggested that the structure, B1 (φ = 164° and ψ = −87°), is more stable than A1 by analyzing the trajectory and the hydrogen bonds with water molecules. This indicates that it is important for the conformational analysis to take into account the solvation effect explicitly. The structure of B1 agrees with that found by an NMR experiment.
Thermochromism and Solvatochromism by Reversible Dye Aggregation in Sugar-Gel Matrices
Authors: Matsushima Ryoka , Okuda Hideki , Aida Madoka , Ogiue Atsushi 
Published: December 2002

Abstract
Upon changes in temperature or solvent, extensive and reversible color changes (e.g., blue to pink) were observed with a cationic flavylium dye in sugar-gel matrices, such as agar, agarose, pectin, sodium alginate, and carrageenan gels, whereas only small spectral changes were found in methylcellulose gel or in the absence of any sugar gels. During many repeated cycles of warming and cooling no indications of significant fatigue were observed, demonstrating a high thermochromic reversibility. Comparable thermochromism and solvatochromism were observed with the well-known cationic dye Methylene Blue in the sugar-gel matrices. In the presence of an anionic surfactant in place of sugar gel, extensive color changes were also observed while no changes were observed at all in the presence of a cationic surfactant, thus implying an important role of the electrostatic interactions between the cationic dye and anionic surfaces or species. It has been assumed that the cationic dyes are reversibly coagulated or condensed on the negatively charged colloid-gel surface to enhance dye aggregation.
Enthalpy–Entropy Compensation of Cyclodextrin Complexation with Different Classes of Substrates
Authors: Liu Lei , Yang Chao , Guo Qing-Xiang 
Published: December 2002

Abstract
In this study, it was found that in the molecular recognition of cyclodextrins, the guest compounds fall clearly into different classes according to the behavior of enthalpy–entropy compensation. Good enthalpy–entropy compensation takes place when the substrates are hydrophobic, whereas poor or no enthalpy–entropy compensation occurs when the substrates are relatively hydrophilic. A thermodynamic theory is proposed to explain the behaviors, and it is suggested that solvent molecular reorganization constitutes the physical origin of the enthalpy–entropy compensation in cyclodextrin complexation.
Structure of EuCrO4 and Its Electronic and Magnetic Properties
Authors: Konno Hidetaka , Aoki Yoshitaka , Klencsár Zoltán , Vértes Attila , Wakeshima Makoto , Tezuka Keitaro , Hinatsu Yukio 
Published: December 2002

Abstract
Single phase zircon type EuCrO4 (S.G. I41/amd) was synthesized and the structure including atomic positions was precisely determined by X-ray Rietveld refinement. The electronic and magnetic properties of the compound were studied based on the electric conductivity, Seebeck coefficient, Raman spectroscopy, Mössbauer spectroscopy, magnetic susceptibility, and specific heat. The CrO43− tetrahedra in EuCrO4 were slightly elongated compared with that in NdCrO4, which caused splitting of the degenerated vibration modes of CrO43−, ν2 and ν3, in the Raman spectra. The 151Eu Mössbauer spectra showed not a trace of the Eu(II) species in the compounds measured in the present work. The Debye temperature, ΘD, estimated from Mössbauer spectra suggested that the vibrational state of Eu(III) in EuCrO4 was similar to that in the perovskite-type EuCrO3. However, the isomer shift of Mössbauer spectra revealed that the electron density of the 6s orbital of Eu(III) in EuCrO4 was very low and almost the same as that in the zircon type EuVO4, that is, Eu(III) in these compounds has highly ionic character, whereas the electron density of the 6s orbital of Eu(III) in EuCrO3 was higher and nearly the same as that in Eu2O3. EuCrO4 was found to be an n-type semiconductor similar to NdCrO4, while zircon type REMO4 (RE: rare earth metal(III); M: V, P, As, etc.) are insulators. Magnetic susceptibility and specific heat measurements showed that antiferromagnetic transitions took place at around 15 K and was solely due to Cr(V) from the magnetic entropy value of 5.54 J mol−1 K−1.
Chloride Transfer across the Liquid–Liquid Interface Facilitated by a Mono-Thiourea as a Hydrogen-Bonding Ionophore
Authors: Nishizawa Seiichi , Yokobori Tomoyuki , Kato Ryo , Shioya Takeshi , Teramae Norio 
Published: December 2002

Abstract
Applicability of a thiourea-based hydrogen-bonding ionophore 2, N,N′-bis(p-nitrophenyl)thiourea, for amperometric anion sensors is presented. Chloride transfer across the nitrobenzene (NB)–water interface facilitated by this ionophore is studied by using ion transfer polarography. When 2 is present in the organic phase, a well-defined wave can be observed, indicating that the chloride transfer across the NB–water interface is facilitated by 2 via formation of hydrogen bonds. The analysis of ion transfer polarograms shows that the chloride transfer is assisted by 1 : 1 complexation between 2 and chloride, and that the transfer process is reversible and controlled by diffusion of 2 from the bulk NB phase to the interface. Despite its simple binding mode based on two point interactions, mono-thiourea 2 has a strong ability to facilitate chloride transfer, which is comparable to that obtained for a highly preorganized bis-thiourea ionophore 1, 2,7-di-t-butyl-4,5-bis(N′-butylthioureylene)-9,9-dimethylxanthene, in which four hydrogen bonds are involved in the chloride binding.
Pressure-Stabilized Low-Spin State for Binuclear Iron(III) Spin-Crossover Compounds
Authors: Hayami Shinya , Hosokoshi Yuko , Inoue Katsuya , Einaga Yasuaki , Sato Osamu , Maeda Yonezo 
Published: December 2002

Abstract
Binuclear iron(III) spin-crossover complexes with salten ligand [Fe2(salten)2(L)](BPh4)2 were synthesized and characterized by single-crystal X-ray diffraction, Mössbauer spectra, magnetic susceptibilities and electronic spectra, where H2salten is a pentadentate ligand derived from salicylaldehyde and 3,3′-diaminodipropylamine and L is a didentate axial ligand (az = azobis(4-pyridine) and cc = 4,4′-vinylenebis(pyridine)). The structures of [Fe2(salten)2(az)](BPh4)2 (1) and [Fe2(salten)2(cc)](BPh4)2 (2) were determined at both 100 K and 298 K. Crystal data for 1 at 100 K: C98H94O4N10B2Fe2, monoclinic, space group P21/c, Z = 2, a = 15.986(2) Å, b = 15.825(2) Å, c = 16.441(2) Å, β = 107.902(2)°, V = 3957.8(8) Å3. Crystal data for 2 at 100 K: C100H96O4N8B2Fe2, monoclinic, space group P21/a, Z = 2, a = 16.4296(8) Å, b = 15.747(1) Å, c = 16.637(1) Å, β = 109.2375(9)° and Z = 2. The complexes 1 and 2 exhibited the spin-crossover behavior depending on temperature within the temperature range of 200 to 350 K, and rapid spin equilibrium behavior was observed by means of Mössbauer spectroscopy at 293 K. The complexes 1 and 2 also exhibited a pressure-induced spin transition between the rapid spin equilibrium state and low-spin state at 300 K. Such a pressure-induced spin transition has not been reported earlier.
Spectrophotometric Determination of Chromium in Ores, Steels and Pure Nickel Samples using Phenothiazines
Authors: Mohamed Ashraf Abdel-Aaty 
Published: December 2002

Abstract
A new, simple, and sensitive method has been developed for the spectrophotometric determination of CrVI based on its reaction with chlorpromazine-HCl (CPH) to give a red product. Under the optimum conditions, the linear range of the calibration graph was 0.00–0.33 µg mL−1 of CrVI. The molar absorptivity and the detection limit were 3.28 × 104 dm3 mol−1 cm−1 and 0.003 µg mL−1 of CrVI, respectively. Analyses of certified ores, steels, and pure nickel samples gave results in excellent agreement with the nominal values and with relative standard deviations of ≤ 1.5%
Neutral Lithium Triflate (LiOTf) Efficiently Catalyzes Chemoselective Preparations of Cyclic and Acyclic Dithioacetals from Carbonyl Compounds, Acylals, and O,O-Cyclic and Open-Chain Acetals under Solvent-Free Conditions
Authors: Firouzabadi Habib , Eslami Shahram , Karimi Babak 
Published: December 2002

Abstract
An efficient and chemoselective preparation of cyclic and acyclic thioacetals from carbonyl compounds, cyclic and acyclic acetals and acylals in the presence of catalytic amounts of neutral lithium triflate and thiols under solvent-free conditions is described.