bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic Voltammetric Characteristics of Tri- and Diarylcarbenium Salts Having Some Methoxyphenyl Groups
Authors: Erabi Tatsuo , Ohtsuki Takayuki , Osaki Eiko , Tomita Nobuyuki , Asahara Masahiro , Wada Masanori 
Published: September 2002

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

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

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

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

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

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

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

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

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

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

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

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

Abstract
The oxygen atom exchange reaction between the terminal oxygen atom (V=O) of tetradentate Schiff base-oxovanadium(IV) complexes and water slowly proceeds in DMSO solutions. The rate constants kobs for the isotopic oxygen atom exchange reaction in DMSO solutions containing excess H218O at 50 °C under an argon atmosphere were obtained for several complexes (6×10-7 to 6×10-5 s-1). The reaction proceeds faster for those complexes with electron-withdrawing groups at the Schiff base ligand moieties, and slower for the complexes with bulky hydrophobic groups. The oxygen atom exchange reaction and isomerization reaction under an argon atmosphere and in air were investigated for oxovanadium(IV) complexes that have two geometrical isomers. Water molecules attack the vanadium atom mainly from the same side of the oxo ligand for the oxovanadium(IV) complexes, whereas mainly from the opposite side of the oxo ligand for the oxovanadium(V) complexes produced by oxidation with air.
Friedel-Crafts Reactions Catalyzed by Rare Earth Metal Trifluoromethanesulfonates
Authors: Kawada Atsushi , Mitamura Shuichi , Matsuo Jun-ichi , Tsuchiya Takehiro , Kobayashi Shu 
Published: September 2002

Abstract
Rare earth metal trifluoromethanesulfonates (rare earth metal triflates, RE(OTf)3) were found to be efficient catalysts for Friedel-Crafts acylation and alkylation. In the presence of a catalytic amount of RE(OTf)3, acylation of aromatic compounds having electron-donating substituents such as anisole, thioanisole, and mesitylene with acid anhydrides proceeded smoothly to afford the corresponding aromatic ketones in high yields. Although RE(OTf)3 alone is not effective for acylation of less reactive aromatics such as toluene, the combination of RE(OTf)3 and lithium perchlorate (LiClO4) enhanced the catalytic activity dramatically. Friedel-Crafts acylation reactions using rare earth metal perfluoroalkanesulfonates were also successfully performed in supercritical carbon dioxide (scCO2). Moreover, in the presence of a catalytic amount of RE(OTf)3, aromatic compounds reacted with benzyl chloride smoothly to afford the corresponding alkylation products in high yields. In these reactions, RE(OTf)3 could be easily recovered after the reactions were completed and could be reused without loss of activity.
Studies on the Conformations of Antimicrobial Salicylanilide Derivatives by Spectroscopy
Authors: Suezawa Hiroko , Hirota Minoru , Yuzuri Tomoaki , Hamada Yoshiki , Takeuchi Isao , Sugiura Michiharu 
Published: September 2002

Abstract
Conformations of variously substituted salicylanilides were determined by NMR spectroscopy. The salicylanilide molecules are fairly rigid, taking either the OH…O=C hydrogen bonded (I) or the NH…O hydrogen bonded (II) conformation. The preference between the two intramolecularly hydrogen bonded conformations is affected by the 3- and/or 2′(6′)-substitutent(s). In general, conformation (I) exists overwhelmingly, while conformation (II) becomes predominant in 3-chloro or 2-O-acetylated salicylanilide in inert solvents. These two intramolecular hydrogen bonds were weakened or destroyed to a great extent in dimethyl sulfoxide.
Reactions of 2,2-Dialkylvinyl Iodonium Salt with Halide Ions
Authors: Okuyama Tadashi , Sato Koichi , Ochiai Masahito 
Published: September 2002

Abstract
Reactions of (E)- and (Z)-2-methyl-5-phenyl-1-pentenyl(phenyl)iodonium (1) salts with halide ions were examined in various solvents at 50 or 60 °C. The main products are those of substitution, 1-halo-2-methyl-5-phenyl-1-pentenes, mainly of inversion but involving some retained products. Varying amounts of rearranged products are also formed. Reaction follows pseudo-first-order kinetics at [1] &lt;&lt; [halide ion]. The observed rate constants show curved dependence on halide concentration typical of reactions involving a pre-equilibrium formation of the adduct, λ3-haloiodane, and first-, second-, and third-order reaction pathways. The first-order rate constant for the E isomer, (E)-1, is greater than that for (Z)-1, while the opposite is the case for the second- and third-order terms. The main reaction is considered to proceed via a vinylic in-plane SN2 mechanism to lead to inversion while some retention routes via out-of-plane SN2 and/or ligand coupling mechanism are also possible. Competing rearrangement reactions occur by the β-alkyl participation and no evidence for formation of the primary vinylic cation was obtained.
Synthesis and Structure of Sterically Congested, New Alkenes, syn- and anti-9,9′-Bibenzonorbornenylidenes
Authors: Sugihara Yoshiaki , Noda Koichi , Nakayama Juzo 
Published: September 2002

Abstract
Sterically congested alkenes, syn- and anti-9,9′-bibenzonorbornenylidenes (1a) and (1b), were synthesized starting from 9-benzonorbornenone in good overall yields and were isolated in pure form. Their structures were elucidated by analyses of NMR spectra and established by X-ray crystallographic analysis. Structures of the two episulfides, which served as precursors leading to 1a and 1b, were also determined by X-ray crystallographic analysis.
Structural and Stereochemical Studies of Tris[2-(trifluoromethyl)phenyl]borane: Spontaneous Resolution, Stereodynamics, and Intramolecular C-F···B Interactions
Authors: Toyota Shinji , Asakura Mitsuhiro , Oki Michinori , Toda Fumio 
Published: September 2002

Abstract
The structure and stereochemistry of the title organoboron compound, prepared from the corresponding organolithium compound and BCl3, were studied by spectroscopic methods and molecular orbital calculations. The X-ray crystal structure analysis shows that molecules take a propeller-shaped structure of nearly C3 symmetry, in which three CF3 groups lie at the same side of the boron sp2 plane. This compound crystallizes as conglomerates to give single crystals consisting of one or the other enantiomeric forms, both of which are CD active in the solid state. In solutions, molecules exist as a mixture of two conformational isomers, the C3 and C1 symmetric forms. Interconversion between the two isomers was observed by the variable temperature 19F NMR, the barriers to isomerization being 8 and 6 kcal mol-1 for two independent processes in the two ring flip mechanism. The presence of C-F···B interactions was supported by the short F···B contacts (ca. 2.80 Å) in the X-ray structure and by the chemical shift of 19F NMR in solutions.