bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Behavior of Benzyltributylphosphonium Salts in Aromatic Hydrocarbons or Aqueous Solutions
Authors: Ohtani Noritaka , Tsuchimoto Daisuke 
Published: September 2002

Abstract
The solubility of benzyltributylphosphonium salt (BTBPX: X = Cl, Br, or I) in aromatic hydrocarbons was examined as a function of the temperature. The solubility curve had specific features, which were characterized by critical values corresponding to the Krafft point and critical micelle concentration. A slight difference in the oil structure exerted a significant effect on the solubility behavior. The Krafft boundary as well as a liquid–liquid immiscibility gap, on the other hand, featured the solubility behavior of BTBPX in an aqueous solution. The shape of the gap was assumed to be a closed loop and the region of the gap was sharply dependent on the concentration of the added metal halide (MX). The phase behavior of the three- or four-component systems, composed of BTBPX, benzene, water, and MX, has been examined in detail. According to their constituent, composition, and temperature, the system afforded a single- to four-phase state form. There were at least three kinds of liquid phases: a BTBPX-rich phase (M), an aqueous solution phase (W), and an oil solution phase (O). When these three liquid phases coexist, the system affords an O–M–W three-liquid-phase equilibrium state. The three-liquid phase may be converted to O–M or M–W two-liquid-phase, depending on the temperature and MX concentration in the W phase. In the presence of excess MX (S), BTBPCl gave an O–M–W–S four-phase state, while BTBPBr or BTBPI never formed a four-phase state. The phase behavior of the four-component systems is discussed based on phase diagrams of fewer component systems.
Platinum-Catalyzed Bis-Germylation of Alkynes with Organodigermanes and Cyclic Oligogermanes
Authors: Mochida Kunio , Wada Tohru , Suzuki Kaoru , Hatanaka Wakako , Nishiyama Yuriko , Nanjo Masato , Sekine Akiko , Ohashi Yuji , Sakamoto Masato , Yamamoto Akio 
Published: September 2002

Abstract
Hexamethyldigermane, Me3GeGeMe3, reacted with various alkynes in the presence of platinum complexes at 120 °C to afford Z–1,2-bis(germyl)ethenes in moderate to good yields. Terminal alkynes exhibit higher reactivities than internal ones. [Pt(acac)2] and [Pt(dba)2] serve as efficient catalysts, while [Pt(PPh3)4], [PtCl2(PPh3)2], and [Pt(dba)2]-phosphite were found to be inactive. Four- and six-membered cyclic oligogermanes, such as dodecamethylcyclohexagermane, (Me2Ge)6, reacted with alkynes in the presence of platinum catalysts to yield 1,4-digermacyclohexa-2,5-dienes in ca. 30% yield. The reactions of phenylacetylene with 1,2-digermacyclohexa-3,5-dienes afforded the corresponding 1,4-digermacycloocta-2,5,7-trienes in 93% yield. Bis(germyl)platinum complexes having various tertiary phosphine ligands have been prepared as models of a key intermediate in the above mentioned catalytic bis-germylation of alkynes, and their structures have been established by spectroscopic methods and X-ray crystallography. Bis(germyl)platinum complexes reacted with phenylacetylene to give the corresponding insertion products, germyl(germylvinyl)platinum species, whose structures have been determined by spectroscopic and X-ray analysis. Germyl(germylvinyl)platinum complexes were found to liberate a bis-germylation product of the alkyne upon heating. The result supports a mechanism involving the oxidative addition of a digermane to a Pt(0) complex, the insertion of an alkyne into one of the two Pt-Ge bonds to give a germyl(germylvinyl)platinum species, and the reductive elimination of the bis-germylation product of the alkyne. Evidence suggesting the extrusion of a germylene unit from the bis-germylplatinum species has been obtained, accounting for the generation courses of other by-products.
Kinetics and Mechanism for the Oxidation of CS2 and COS at High Temperature
Authors: Murakami Yoshinori , Kosugi Masami , Susa Kenji , Kobayashi Takaomi , Fujii Nobuyuki 
Published: September 2002

Abstract
The rate constants for the thermal decompositions of CS2 and COS were investigated by measuring the time profiles of S atom using atomic resonance absorption spectroscopy behind the incident shock of CS2/Ar or COS/Ar mixtures, and the rate constants were determined to be k = (4.0 ± 0.1) × 1014 exp (−295 ± 20 kJ/RT) cm3 mol−1 s−1, T: 2200–2900 K and k = (1.4 ± 0.3) × 1015 exp (−290 ± 25 kJ/RT) cm3 mol−1 s−1, T: 2000–3200 K, respectively. The oxidation mechanism of COS was also investigated behind the incident shock of COS/O2/Ar mixtures and the rate constant for the reaction S + O2 → SO + O was obtained to be k = (9.5 ± 0.7) × 1013 exp (−41 ± 28 kJ/RT) cm3 mol−1 s−1, T: 2200–2900 K. From a numerical analysis for time profiles of S atom behind the incident shock of CS2/O2/Ar mixtures, the rate constant for the reaction O + CS → CO + S was expressed as k = (3.2 ± 1.0) × 1013 cm3 mol−1 s−1, T: 2100–3000 K. Similarly, the rate constant for the reaction CS + O2 → COS + O was also determined to be k = (6.1 ± 0.6) × 1012 exp (−51.0 ± 68 kJ/RT) cm3 mol−1 s−1, T: 2000–2900 K by measuring the time profiles of O atom behind the reflected shock of CS2/O2/Ar mixtures. Ab initio calculations were carried out and the reaction pathways of CS + O2 → COS + O and CS + O2 → CO + SO were also investigated.
Theoretical Study of a Conformational Change Occurring with Lithium Complexation to a Tetra-aza Macrocycle Containing 2,2′-Bipyridines
Authors: Furuhama Ayako , Takano Keiko , Ogawa Shojiro , Tsuchiya Shinji 
Published: September 2002

Abstract
Ab initio Hartree–Fock theory was used to determine the structures of model molecules of a dibutyl dicyano tetra-aza macrocycle (1) containing 2,2′-bipyridines and their lithium complexes. Energy profiles for the conformational inversion, which is closely related to the complexation process of a lithium cation, were also studied. Macrocycles having cyano groups on the bridge methylene carbons were found to be good macrocyclic models related to the macrocycle (1). The energy profiles of stationary points and the vibrational frequencies of macrocycles and their lithium complexes reveal that conformational inversion in the lithium complexes is plausible after lithium complexation. The difference in the vibrational frequencies corresponding to the movement of the lithium cation suggests that C2v-like skeletons in the macrocyclic moiety have a stronger interaction between the lithium cation and coordinating nitrogens than the C2h structure.
Temperature- and Pressure-Induced Phase Transitions in p-Difluorobenzene Crystals
Authors: Towata Yuji , Suzuki Yoshio , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi 
Published: September 2002

Abstract
The temperature and pressure effects on the Raman-active inter- and intramolecular vibrations of [1H4]- and [2H4]p-difluorobenzene crystals were studied. The observed spectral structure, and the temperature and pressure dependences on the vibrational frequencies of the inter- and intramolecular vibrations indicate the following facts: (1) The temperature-induced phase transitions take place at about 235 and 195 K under 1 atm in [1H4]- and [2H4]p-difluorobenzene crystals. (2) The pressure-induced phase transition takes place under about 2.7 and 2.8 GPa at 298 K in [1H4]- and [2H4]p-difluorobenzene crystals, respectively. (3) A weak C–H···F–C intermolecular interaction exists in crystals.
The Effect of Surfactants on Equilibria in Aluminium(III) Ion + Ofloxacin Solution and Adsorption of Ofloxacin on Aluminium-Oxide
Authors: Djurdjevic Predrag , Jelikic-Stankov Milena , Lazarevic Ivan 
Published: September 2002

Abstract
The protonation and complex formation equilibria in aluminium(III) + ofloxacin (Hoflo) solutions in the presence of either cetyltrimethylammonium bromide (CTAB, 5.0 mmol L−1), cetylpyridinium chloride (CPCL, 2.0 mmol L−1) or polyethylene glycol tert-octylphenyl ether (triton X-100, 1.0 mmol L−1) have been studied by glass-electrode potentiometric measurements in a 0.1 mol L−1 LiCl ionic medium at 298 K. In the concentration range 0.4 ≤ CAl ≤ 1.0 mmol L−1, with a ligand to metal ratio of 1 : 1 to 5 : 1, and 3.5 ≤ −log h ≤ 7.0, a non-linear least squares treatment of the data indicate that in all studied systems the complex Al(oflo)2+ forms as the dominating one. Its overall stability constant (log β) is in the range 10.37–11.90 (depending on the type of surfactant), which is about 1 log unit higher than in the absence of surfactants. The formation of bis(ofloxacinato) and mixed protonated or hydrolytic complexes is largely suppressed in the presence of surfactants. The adsorption of ofloxacin on aluminium oxide was studied in neutral, acidic (0.1 mol L−1 HCl) and alkaline (0.001 mol L−1 NaOH) media; in absence and presence of ionic surfactants; sodium dodecylsulfate (SDS, 10 mmol L−1); or CTAB (5.0 mmol L−1). The adsorption is of the Freundlich type and is higher in neutral media with no presence of surfactants, while in an acidic medium it is significantly enhanced in the presence of SDS. Both surfactants increase the adsorption in an alkaline medium. The observed phenomena were explained based on the hydrophilic/lipophilic properties of the surfactants.
Flotation-Separation of Chromium(VI) and Chromium(III) from Water and Leathers Tanning Waste Using Active Charcoal and Oleic Acid Surfactant
Authors: Ghazy Shaban El-Sayed , Moustafa Gamal Abdel-Hafeez 
Published: September 2002

Abstract
An experimental procedure is presented for the separation of Cr(VI) and Cr(III) from aqueous solutions, natural water and leather tanning waste using powdered active charcoal (PACh) as an adsorbent and oleic acid (HOL) as a surfactant. Several parameters (namely: the initial concentrations of surfactant and active charcoal, pH value, ionic strength, shaking time, temperature and foreign ions) that influence the separation process were studied. Good results were obtained, according to which more than 98% of Cr(VI) at pH 2.0 or Cr(III) at pH 7.5 were removed. The selective separation of Cr(VI) from Cr(III) was also examined, since the system Cr(III)/Cr(VI) is toxic, and occurs in industrial effluents and some surface waters. The procedure may find analytical applications for speciation studies. Moreover, a flotation mechanism is suggested.
Reversed-Phase High-Performance Liquid-Chromatographic Determination Systems Specific to Ultratrace Hard Metal Ions with Tridentate Schiff Bases and Pyridylhydrazones
Authors: Hoshino Hitoshi , Saitoh Yuzuru , Nakano Koji , Takahashi Toru , Yotsuyanagi Takao 
Published: September 2002

Abstract
Two Schiff-base ligands derived from salicylaldehyde and two 2-pyridylhydrazones were examined for the ultratrace determination of metal ions by reversed-phase high-performance liquid chromatography (HPLC). Although these ligands have been thought to be rather unattractive in inorganic analysis, their renewal in the HPLC methodology was demonstrated in this work. In these ligand systems, certain hard metal ions such as Al(III), Ga(III), V(V), Fe(III), and Co(III) ions, were effectively separated on octadecyl- or cyanopropyl-bonded silica packing materials. A highly sensitive fluorimetric detection of Al(III) ion was achievable with N-salicylidene-2-hydroxyaniline having an O,N,O donor set; although the contamination problem actually limited the detection capability, the calculated detection limit for Al(III) ion was down to 0.1 nM (3 ppt) on a 3 σ blank basis. The chromatography of chelates with 4-N,N-diethylaminosalicylaldehyde-2-pyridylhydrazone seems to be attractive for actual analysis; Al(III), Ga(III), V(V), Fe(III), and Co(III) ions at the sub-ppb to ppb levels have been photometrically detected with a relative standard deviation of less than 5%. The fluorimetric detection using 4-hydroxysalicylaldehyde-2-pyridylhydrazone was very effective to access trace levels of Al and Ga ions, giving detection limits of 3.0 nM and 1.3 nM, respectively (M = mol dm−3).
Thermal Stability of Pyridine Base Complexes of Cadmium Chloride
Authors: Sawada Kiyoshi , Satoh Keiichi , Shirakura Yasuhiro , Masuda Yoshio 
Published: September 2002

Abstract
The heat of decomposition of a series of crystalline pyridine base (Rpy) complexes of cadmium chloride was determined by means of differential scanning calorimetry, where the complexes were bis(pyridine base) complexes, CdCl2·2Rpy (Rpy = pyridine and 4-methyl-, 3-methyl-, 4-acetyl- and 4-cyanopyridine) and mono(pyridine base) complexes, CdCl2·Rpy (Rpy = 2-methyl- and 2-ethylpyridine). The heats of dissolution of the pyridine base complexes, cadmium chloride CdCl2, and pyridine bases in a non-polar aprotic solvent, 1,2-dichloroethane, containing tetrabutylammonium chloride were determined by a calorimetry. The stability of the crystalline complexes is discussed in connection with the heat of dissolution and reaction of the complexes in solution. The stability of the complexes is explained by various interactions, such as the basicity and steric hindrance of the pyridine bases and the intermolecular interaction between the complexes.
Synthesis and Structure of Ln(W5O18)-Capped Mixed-Ligand Polyoxotungstolanthanoate [Ln(W5O18){Ln(H2O)2(SbW9O33)(W5O18)}]15−(Ln = Sm and Er)
Authors: Naruke Haruo , Yamase Toshihiro 
Published: September 2002

Abstract
Polyoxotungstolanthanoate, [Ln2(H2O)2(SbW9O33)(W5O18)2]15− (Ln = Sm and Er), possessing Ln3+, trivacant α-B-Keggin [SbW9O33]9−, and monovacant Lindqvist [W5O18]6− groups with a ratio of 2 : 1 : 2, was prepared and structurally characterized. In the anion the α-B-[SbW9O33]9− group coordinates to two [Ln(W5O18)]3− moieties through terminal- and bridging-O atoms at vacant and non-vacant sites, respectively. A 183W-NMR spectrum for Y3+-analog in aqueous solution was consistent with this anion structure.
Crystal Structures and Spectroscopic Characterization of Linear-Type S-Bridged Trinuclear Complexes ΔΛ- and ΔΔ/ΛΛ-[ReIII{RhIII(aet)3}2]3+ (aet = 2-Aminoethanethiolate)
Authors: Miyashita Yoshitaro , Mahboob Nagina , Tsuboi Satoko , Yamada Yasunori , Fujisawa Kiyoshi , Okamoto Ken-ichi 
Published: September 2002

Abstract
The reduction of an acidic mixture of fac(S)-[RhIII(aet)3] (aet = 2-aminoethanethiolate) and NH4ReVIIO4 gave the first linear-type S-bridged trinuclear complexes containing a d4 metal ion, [ReIII{RhIII(aet)3}2]3+. The meso (1a) and racemic (1b) isomers were selectively isolated by using HCl and HBr solutions, respectively, although both isomers were formed in each case. The crystal structures of 1aCl(ReO4)2·4H2O and 1b(ClO4)3 were determined by X-ray crystallography. Both complex cations consist of two terminal fac(S)-[RhIII(aet)3] units and a central rhenium atom, which is situated in an octahedral environment with the ReIIIS6 chromophore. 1b was optically resolved by a column chromatographic method and characterized by CD spectroscopy. 1a and 1b were fairly stable in water, even under aerobic conditions, unlike in the case of previously reported [MoIII{RhIII(aet)3}2]3+. The Re(III) ion, which is incorporated into the S-bridged polynuclear structure, indicated a lower magnetic moment (1.32 μB for 1b) at room temperature than the spin-only value for the d4 electronic configuration. The 1H and 13C NMR spectra of 1a and 1b showed paramagnetic shifts compared with those of the corresponding diamagnetic complexes, [CoIII{RhIII(aet)3}2]3+. 1a and 1b were also characterized on the basis of the IR and UV-vis absorption spectra and the molar conductivities.
Stereoselective Electron-Transfer Reactions of Myoglobin and Cytochrome c with Chiral Viologen-Radical Cations
Authors: Tsukahara Keiichi , Ueda Rie , Goda Mariko 
Published: September 2002

Abstract
Electron-transfer (ET) reactions of metmyoglobin (metMb) and the oxidized form of cytochrome c (cyt c(III)) with chiral viologen-radical cations containing (1-phenyl- and 1-cyclohexylethyl)carbamoylmethyl groups were examined at pH 7.0 (10 mM phosphate buffer), ionic strengths (I) of 0.040–0.50 M, and temperatures of 10–35 °C. In the metMb system, the pseudo first-order rate constant of the decay of the viologen-radical cation was saturated with increasing concentrations of metMb, indicating that metMb interacts with the viologen-radical cation to form a complex followed by an intramolecular ET reaction. The stereoselectivity was observed in both the complex formation and the intramolecular ET processes for the (S,S)-isomers of chiral viologens. The ratios of the association constants and the intramolecular ET rate constants of the (S,S)-isomer with those of the (R,R)-isomer were 1.1–1.3 and 1.1–1.5, respectively. The saturation kinetics was not observed for the ET reaction between metMb and the achiral benzylviologen-radical cation, which has no CONH bond, suggesting that the hydrogen bonding of the CONH group of the chiral viologen with the side chain of the polypeptide in metMb plays an important role in the stereoselectivity. No appreciable complex formation was observed in the ET reaction between cyt c(III) and viologen-radical cations, although the stereoselectivity was observed. The ratios of the second-order rate constants of the (S,S)-isomer with those of the (R,R)-isomer were 1.1–1.4. The stereoselectivity is discussed based on the activation parameters.
Organization of Nucleosides Supported by Boronic-Acid-Appended Poly(l-lysine): Creation of a Novel RNA Mimic
Authors: Kobayashi Hideki , Amaike Masato , Koumoto Kazuya , Shinkai Seiji 
Published: September 2002

Abstract
Boronic-acid-appended poly(l-lysine) (1) can form anionic boronate esters with diol derivatives in aqueous solution. One can thus expect that when nucleosides are mixed with 1, the resultant complexes will satisfy the basic structural characteristics of RNA, viz., one-dimensionally organized nucleic bases and anionic charges. To obtain insights into this novel RNA mimic, the solution properties of adenosine (Ad) were estimated in the absence and the presence of 1. The large absorption and CD spectral changes were observed at pH 6–10 where the poly(l-lysine) main chain tends to adopt an α-helix-rich conformation. On the basis of the fact that the magnitude of the spectral changes is much larger than the fraction of complexed Ad molecules, the polymer-supported organization mode was proposed: that is, Ad molecules complexed by covalent bonds with 1 act as clusters to induce further organization of uncomplexed Ad molecules by noncovalent interactions. The proposal was further confirmed by 1H NMR spectroscopy and dynamic light scattering. On the other hand, none of these spectral changes were observed for 2′-deoxyadenosine. The 1–Ad complex thus formed can interact with complementary poly(U) but not with noncomplementary poly(C), indicating that it can act as a novel RNA mimic.
Practical Synthesis of 13-Substituted Milbemycin
Authors: Sugiyama Yoko , Saito Akio 
Published: September 2002

Abstract
A novel and practical method to synthesize 13-alkoxy derivatives from milbemycin A4 was studied and an efficient approach via the 15-hydroxymilbemycin derivative was established. During the study, a novel conversion of the 15-alkoxy derivative into the 13-alkoxy derivative via allyl cation and a new method for the conversion of allyl iodide into allyl ether using copper(I) trifluoromethanesulfonate as a catalyst were also found.
Adamantane-2,4-bis(p-quinone methide) and -2,6-bis(p-quinone methide) as New Models for Intramolecular Interactions between Spatially Separated Redox Systems
Authors: Kurata Hiroyuki , Shimoyama Takushi , Matsumoto Kouzou , Kawase Takeshi , Oda Masaji 
Published: September 2002

Abstract
Adamantane-2,4-bis(p-quinone methide) and -2,6-bis(p-quinone methide) were synthesized by the reaction of adamantane-2,4-dione and -2,6-dione, respectively, with lithium 4-lithio-2,6-di-t-butylphenoxide, followed by dehydration. Their structures were established by spectroscopic and X-ray crystallographic analyses. Having a distance (2.47 Å) between C2 and C4 longer than that (ca. 1.9 Å) between C1 and C3 of cyclobutane-1,3-bis(p-quinone methide)s, adamantane-2,4-bis(p-quinone methide) was found to show a clear through-space interaction (homoconjugation) and to form a σ-bond at its bis(anion radical) stage upon both chemical and electrochemical reduction. On the other hand, adamantane-2,6-bis(p-quinone methide), which has a long distance and near orthogonal arrangement between the quinone methide chromophores, shows a through-bond interaction, though it is weak.
Highly Active 3-Oxobutylideneaminatocobalt Complex Catalysts for an Enantioselective Hetero Diels–Alder Reaction
Authors: Kezuka Satoko , Mita Tsuyoshi , Ohtsuki Natsuki , Ikeno Taketo , Yamada Tohru 
Published: September 2002

Abstract
Optically active 3-oxobutylideneaminatocobalt(III) complexes were developed as effective catalysts for the enantioselective hetero Diels–Alder reaction of aromatic and aliphatic aldehydes with 3-(t-butyldimethylsilyloxy)-1-methoxy-1,3-butadiene. In the presence of the highly active cationic cobalt(III) complex, the hetero Diels–Alder reactions proceeded to afford the corresponding dihydropyran-4-ones with high performance and high enantioselectivities. The reaction with aromatic aldehydes substituted by a coordinating group at the ortho position proceeded more smoothly.
Palladium(II)- and Rhodium(III)-Catalyzed Carbonylation Reaction of Aryltin Compounds
Authors: Ohe Toshiyuki , Motofusa Shin-ichi , Ohe Kouichi , Uemura Sakae 
Published: September 2002

Abstract
A variety of aryltin compounds can be employed for carbonylation reactions in the presence of a catalytic amount of palladium(II) salt with reoxidant in acetonitrile or acetic acid under an atmospheric pressure of carbon monoxide (CO) to afford arenecarboxylic acids and diaryl ketones. Similar reactions also proceed by using rhodium(III) salt as a catalyst, where the presence of reoxidant is sometimes not necessary. More than one of two, three, or four aryl groups of aryltin compounds, and almost all of them in some cases, can be transferred to the products in this catalytic carbonylation.
Size Control of Metastable ZnS Particles in W/O Microemulsion
Authors: Hanaoka Toshiaki , Tago Teruoki , Kishida Masahiro , Wakabayashi Katsuhiko 
Published: September 2002

Abstract
The effect of various factors on the metastable size of ZnS particles was investigated in order to widely and precisely control the size of ultrafine particles synthesized in a microemulsion. The metastable size of the ZnS particles could be more widely changed by changing the microemulsion system, the specific permittivity of the organic solvent, the pH, and the synthesis temperature than the previously reported factors. We proposed a stabilization model of the ZnS ultrafine particles by surfactants and a new method for controlling the size of ultrafine particles synthesized in the microemulsion.
Non-specific and Specific Adsorption of Proteins on Langmuir–Blodgett Films of Amino Acid Derivative Polymers
Authors: Ide Makoto , Mitamura Akihiro , Miyashita Tokuji 
Published: September 2002

Abstract
Polymer LB films consisting of lysine and alanine derivative polymers were prepared to investigate the interfacial recognition between protein and ligand on the LB film. The surface of lysine derivative polymer LB film was modified by the biotin molecule that is the ligand for avidin. The biotinylation was carried out without inducing non-specific adsorption of proteins; avidin specifically adsorbed onto the biotinylated surfaces. Moreover, it was found that there is an optimum molar ratio of biotinylation for the adsorption of avidin onto the surface.