bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetizabilities of Ring-Structured Molecules, [8]-Cyclacene, [8]-BN-Cyclacene and [8]-Collarene, and their Effect on 3He Nuclear Shielding Tensor
Authors: Tonmunphean Somsak , Wijitkosoom Atchara , Tantirungrotechai Yuthana , Nuttavut Narin , Limtrakul Jumras 
Published: August 2003

Abstract
The magnetizabilities of three ring-structured molecules, [8]-cyclacene, [8]-BN-cyclacene, and [8]-collarene, were subsequently calculated at the B3LYP/6-31G* level with the CSGT gauge-origin treatment. The magnetizability of [8]-cyclacene shows a large diamagnetic nature in the direction parallel to the ring cylindrical axis, while the value of [8]-BN-cyclacene is nearly isotropic, and that of [8]-collarene is slightly more diamagnetic in the perpendicular direction than in the parallel direction. A large diamagnetic magnetizability in the parallel direction of [8]-cyclacene arises from the current flow around the ring circumference. The magnetic environment in the ring channel of these three molecules was investigated by calculating the nuclear shielding tensor of the 3He atom when the atom moves through the ring channel. The GIAO nuclear shielding tensor changes significantly toward a prolate shape in [8]-cyclacene, but becomes a slightly oblate shape in [8]-BN-cyclacene and [8]-collarene. The changes correlate well with the magnetizabilities of the ring-structured molecules.
Flotation and Spectrophotometry: Thorough Investigation and Application to the Determination of the Total Amounts of Lanthanum and Yttrium in Natural Samples
Authors: Akl Magda Ali , Kabil Mohammed Abdel Ghany , Abdallah Amin Mahmoud , Ismael Dalia Salah 
Published: August 2003

Abstract
The extraction and preconcentration of a metal complex via surfactant-mediated phase separation was studied. A sensitive, selective and low-cost methodology for the determination of microamounts of Lanthanum and Yttrium, using alizarin red sulfonate (ARS) with a flotation step prior to absorptiometric determination was developed. The precipitate in the scum layer was quantitatively collected, stripped with 10% HNO3 and measured by spectrophotometry at 650 nm. Stripping of La(III) and Y(III) from the scum layer was carried out in one step with different mineral acids. The stripping efficiency was found to be quantitative in the case of HNO3. Excess ARS was used to nullify the interfering effects of various foreign species. The proposed procedure has been applied to the determination of La and Y spiked in natural water samples and real ore samples. Additionally, the mechanism of flotation of the metal chelate was proposed to be due to a physical interaction between the metal chelate and the oleic acid surfactant through the van der Waal force.
Coordination of Amines to Palladium(II) Complexes of N21,N22-Bridged Porphyrins
Authors: Takao Yuko , Takeda Tokuji , Setsune Jun-ichiro 
Published: August 2003

Abstract
Pyridine and ethylenediamine reacted with Pd(II) complexes of N21,N22-bridged porphyrins to give mixed-ligand Pd(II) complexes. The UV-vis and 1H NMR spectral features of the porphyrin ligand provide information regarding the nature of the coexisting ligands and Pd(II) coordination geometry in the products. That is, the splitting pattern in the Soret region of the UV-vis spectra was dependent on whether porphyrinatopalladium(II) was coordinated by neutral ligands or anionic ligands. In the 1H NMR spectra of ethylenediamine complexes of porphyrinatopalladium(II), signal broadening of porphyrin β-pyrrole protons and a chemical shift change of ethylenediamine protons were seen in the dichloride in comparison with the bis(perchlorate). These phenomena indicate the equilibrium of the coordination and dissociation of chloride and amine at the apical and basal sites in the square pyramid. The H–D exchange in the ethylenediamine ligand was promoted by the presence of chloride.
Synthesis of Cross-Linked Chitosan Resin Possessing Leucine Moiety for the Column Collection/Concentration of Molybdenum and Determination of Molybdenum by ICP-MS, ICP-AES and GFAAS
Authors: Oshita Koji , Xu Jingsong , Gao Yun-Hua , Lee Kyue-Hyung , Oshima Mitsuko , Motomizu Shoji 
Published: August 2003

Abstract
A chitosan resin possessing the leucine moiety (leucine-type chitosan) was newly synthesized by using the chitosan cross-linked with ethylene glycol diglycidyl ether (EGDE) as a basic material. The adsorption behavior of trace amounts of metal ions on the leucine-type chitosan was systematically examined by packing it in a mini-column by ICP-MS (inductively coupled plasma mass spectrometry). Molybdenum was adsorbed on the resin quantitatively and was easily eluted with 1 M nitric acid. The optimized pH range was from 1 to 5, and Mo was collected by the chelation mechanism and/or the anion-exchange mechanism. The method was applied to the determination of Mo in sea and river water samples. A pretreatment with the resin could remove the matrix components in seawater. Preconcentration by 100-fold was accomplished by a column treatment, which had a sufficient concentration to measure trace Mo in river water samples by ICP-AES (inductively coupled plasma atomic emission spectrometry) and GFAAS (graphite furnace atomic absorption spectrometry): LODs with a 100-fold preconcentration by ICP-AES and GFAAS were 0.007 ng mL−1 and 0.009 ng mL−1, respectively, and the RSDs were both within 4.0%.
Conformation and Packing of Odd-Numbered α-Oligothiophenes in Single Crystals
Authors: Azumi Reiko , Goto Midori , Honda Kazumasa , Matsumoto Mutsuyoshi 
Published: August 2003

Abstract
X-ray single crystal analyses revealed the molecular geometry and molecular packing of odd-numbered α-oligothiophenes (septithiophene, quinquethiophene and terthiophene) in single crystals prepared by sublimation. Septithiophene crystallizes into triclinic, which is in contrast to the monoclinic packing of even-numbered oligomers. The molecular arrangement of septithiophene in a single crystal resembles that reported for even-numbered oligomers, while the molecules take a more random conformation: only one of the two terminal thienyl rings exhibits disorder and significant torsion from the conjugated plane. The X-ray diffraction data of a quinquethiophene single crystal suggest that the molecule with one of the two different orientations randomly occupies each site.
Kinetic Study of Fast Complexation of Zinc(II) with 8-Quinolinol and 5-Octyloxymethyl-8-Quinolinol at 1-Butanol/Water Interface by Two-Phase Sheath Flow/Laser-Induced Fluorescence Microscopy
Authors: Tokimoto Takahira , Tsukahara Satoshi , Watarai Hitoshi 
Published: August 2003

Abstract
The kinetics of the fast complexation of zinc(II) with 8-quinolinol (Hqn) and 5-octyloxymethyl-8-quinolinol (Hocqn) at the 1-butanol/water interface was investigated with two-phase sheath flow/laser-induced fluorescence microscopy. The micrometer-sized two-phase sheath flow system was constructed in a flow cell, in which the 1-butanol phase was introduced as an inner flow and the aqueous phase as an outer flow. The fluorescence emitted from the zinc(II) complex was corrected by an objective lens, and detected with a CCD camera. It was revealed that the fluorescence intensity had a maximum value at the interfacial region, and increased with the reaction time up to 2 ms after the formation of the interface. The complexation rate increased with the increase of the initial ligand concentration in the organic phase, giving a saturation curve. The complexation rate of Hqn with zinc(II) was three times faster than that of Hocqn at equivalent conditions. A digital simulation taking into account the interfacial formation rate of 1:1 complex, the interfacial adsorption of the ligand and complex, and the diffusion of each species reproduced accurately the observed results. It was suggested that the interfacial adsorption of ligands was delayed and depressed by the preferential occupancy of 1-butanol molecules at the interface.
Synthesis, Structure, and Properties of the First Disulfur and Diselenium Complexes of Platinum
Authors: Nagata Kazuto , Takeda Nobuhiro , Tokitoh Norihiro 
Published: August 2003

Abstract
The first platinum disulfur and diselenium complexes, [Pt(S2)(ArMe2P)2] (Ar = Tbt (4a), Bbt (4b)) and [Pt(Se2)(ArMe2P)2] (Ar = Tbt (5a), Bbt (5b)), have been synthesized by the reactions of the corresponding overcrowded platinum(0) complexes [Pt(ArMe2P)2] with elemental sulfur and selenium. Molecular structures of 4b and 5b were established by X-ray crystallographic analyses, which show a novel three-membered PtE2 (E = S, Se) ring structure with a square planar geometry around the platinum center. The oxidation of 4b and 5b with an equimolar amount of m-chloroperbenzoic acid or tert-butyl hydroperoxide in dichloromethane afforded the corresponding disulfur and diselenium monoxide complexes [Pt(E2O)(BbtMe2P)2] (E = S (6), Se (7)), respectively. An interesting difference in reactivity between 6 and 7 was shown in the further reactions with an excess of oxidants, which produced the corresponding O,S-coordinated thiosulfate complex [Pt(S2O3)(BbtMe2P)2] (8) and the O,O-coordinated selenite complex [Pt(SeO3)(BbtMe2P)2] (11), respectively. The dynamic behavior in solution was revealed by the variable-temperature NMR spectroscopy for 4b, 5b, 8, and 11, which indicates the existence of the intramolecular CH···E (E = O, S, Se) interactions between the methine hydrogens of the o-bis(trimethylsilyl)methyl groups and the Pt-bonded heteroatoms.
Template Synthesis of Copper Complexes of Dinucleating and Tetranucleating Macrocyclic Ligands
Authors: Matsumoto Kohta , Arimura Keisuke , Ohba Masaaki , Okawa Hisashi 
Published: August 2003

Abstract
The reaction of N,N′-dimethyl-N,N′-trimethylenedi(3-aminomethyl-5-methylsalicylaldehydato)copper(II) with 1,3-diaminopropane in DMF afforded the [1+1] condensation product [Cu(L)] and the [2+2] condensation product [Cu2(R)]. The dinucleating macrocyclic ligand (L)2− has one N(amine)2O2 and one N(imine)2O2 metal-binding sites sharing two phenolic oxygen atoms and the tetranucleating macrocyclic ligand (R)4− has two N(amine)2O2 and two N(imine)2O2 sites in an alternate arrangement in the macrocyclic framework. The mixture of [Cu(L)] and [Cu2(R)] was treated with CuCl2 to give [Cu2(L)Cl2] (1a) and [Cu4(R)Cl4] (2a), which were separated based on different solubility in methanol. 1a and 2a were converted into [Cu2(L)](ClO4)2 (1b) and [Cu4(R)(dmf)2](ClO4)4·2H2O (2b), respectively, by the treatment with AgClO4. 1a and 1b each has a dinuclear core doubly bridged by the phenolic oxygen atoms. The crystal structure of [Cu4(R)(dmf)2](ClO4)4·2DMF·H2O·PrOH (PrOH = 2-propanol) (2b′) was determined by X-ray crystallography. It has a dimer-of-dimers structure where each N(amine)2O2 entity accommodates one Cu ion in the usual tetradentate chelating mode, whereas each N(imine)2O2 entity assumes a spread shape to combine one Cu ion with its NO donor atoms and another Cu ion with the remaining NO donor atoms. 2b can be converted into 2a in the presence of chloride ion. Based on magnetic and visible spectral studies, 2a is supposed to have a folded structure of 2b with two Cu–Cl–Cu linkages.
Selective Extraction and Isolation of Vitamin B12 Using Homogeneous Liquid–Liquid Extraction with Perfluoro Surfactant
Authors: Takagai Yoshitaka , Igarashi Shukuro 
Published: August 2003

Abstract
Cyanocobalamin (vitamin B12) was selectively extracted from a biological sample by the homogeneous liquid–liquid extraction based on a pH-dependent phase separation with perfluorooctanoate ion (PFOA−). When the experimental conditions were [PFOA−]T = 2.86 × 10−3 mol L−1, [HCl]T = 0.66 mol L−1, and [Acetone]T = 2.86 vol %, 8.46 × 10−7 mol L−1 (1.14 ppm) of vitamin B12 was selectively extracted at 95.2% (sample solution; 35 mL → a liquid sedimented phase; 30 μL). This liquid sedimented phase consisted of large amounts of HPFOA. When microliter levels of THF and water were added to this sedimented phase, vitamin B12 is completely and rapidly back-extracted from the sedimented phase to the water phase. Vitamin B12 was then extracted into the water phase at 96.2% and all HPFOA remained in the sedimented phase. The rest of the sedimented phase after the back-extraction was dried and completely recovered as a powder of HPFOA. Consequently, this method was able to recycle HPFOA as a separation medium. Vitamin B12 in a water phase was also crystallized by the addition of excess THF. Moreover, this method was applied to the extraction from rare oysters. As a result, a few micrograms of vitamin B12 were recovered.
Synthesis and Characterization of the Au11 Cluster with Sterically Demanding Phosphine Ligands by Single Crystal X-ray Diffraction and XPS Spectroscopy
Authors: Nunokawa Keiko , Onaka Satoru , Yamaguchi Tadashi , Ito Tasuku , Watase Seiji , Nakamoto Masami 
Published: August 2003

Abstract
A new Au11 cluster with (m-CF3C6H4)3P ligands has been synthesized and characterized by single crystal X-ray and XPS analysis. The cluster has an incomplete icosahedral skeleton similar to known Au11X3(PR3)7 clusters, but a stronger distortion from the ideal symmetry has been caused by introducing CF3 substituents at a meta-position of each phenyl ring of PR3 ligands.
Syntheses of O-β-d-Mannosyl-(1→4)-O-α-d-mannosyl-(1→3)-l-rhamnose and O-(2-Acetamido-2-deoxy-β-d-mannosyl)-(1→4)-O-α-d-galactosyl-(1→4)-d-galactose via In-situ-activating Glycosylation Using 2-O-Acetyl-3,4,6-tri-O-benzyl-d-glucose
Authors: Koto Shinkiti , Shinoda Yoshika , Hirooka Motoko , Sekino Akiko , Ishizumi Sachiko , Koma Mutsuko , Matuura Chieko , Sakata Naoko 
Published: August 2003

Abstract
O-β-d-Mannopyranosyl-(1→4)-O-α-d-mannopyranosyl-(1→3)-l-rhamnopyranose, a trisaccharide including a repeating unit of the O-specific polysaccharide (OSP) of Bulkholderia vietnamiensis strain LMG 6988, and O-(2-acetamido-2-deoxy-β-d-mannopyranosyl)-(1→4)-O-α-d-galactopyranosyl-(1→4)-d-galactopyranose, a trisaccharide including a repeating unit of OSP of Acinetobactor baumannii serogroup O18, were synthesized by means of in-situ-activating glycosylation using 2-O-acetyl-3,4,6-tri-O-benzyl-d-glucopyranose (2ATBG) and a reagent mixture of p-nitrobenzenesulfonyl chloride, silver triflate, and 1,8-diazabicyclo[5.4.0]undec-7-ene, and related systems. New syntheses of 2ATBG, allyl 2,3,6-tri-O-benzyl-α-d-galactopyranoside, benzyl 2,3,6-tri-O-benzyl-α-d-galactopyranoside, and 2-azido-3,4,6-tri-O-benzyl-2-deoxy-d-mannopyranose are described.
Solvent-Dependent Conformation of the Third Repeat Fragment in the Microtubule-Binding Domain of Tau Protein, Analyzed by 1H-NMR Spectroscopy and Molecular Modeling Calculation
Authors: Minoura Katsuhiko , Tomoo Koji , Ishida Toshimasa , Hasegawa Hiroshi , Sasaki Masahiro , Taniguchi Taizo 
Published: August 2003

Abstract
The third repeat fragment (3MBD, 31 residues) in the four-repeat microtubule-binding domain of tau protein is considered to be responsible for the formation of the neuropathological filament. To clarify the structural function of 3MBD in the filamentous assembly, solution structures in water and 2,2,2-trifluoroethanol (TFE) were investigated by CD measurement and the combination of two-dimensional 1H-NMR measurement and a molecular modeling calculation. The CD spectra suggested the solvent-dependent conformation of 3MBD, i.e., random and α-helical structures in water and TFE solvents, respectively. All protons were assigned by various 2D NMR spectral measurements. The NOE pattern characteristic of a typical helical structure was observed in TFE solution. Using NOE and JHNCαH data observed in both solutions, possible 3D structures were generated by the dynamical simulated annealing method. The constructed NMR conformers in water consisted of an equilibrium mixture of extended and folded conformers, although the N-terminal Val1–Lys6 and middle fragments formed well-refined extended (Val1–Lys6) and α-helical (Leu10–Leu20) structures in TFE, respectively. Interestingly, the helical structure showed an amphipathic distribution of the respective side chains. This amphipathic behaviour of the 3MBD structure is advantageous for self-association through the alternating hydrophilic and hydrophobic interactions into a helical filament of the tau MBD domain. Based on the situation-dependent conformational flexibility of 3MBD, the possibility of filament formation of tau protein via self-assembly of the α-helical structure under neuropathological conditions is discussed.
Fluorescence Property of Photochromic Diarylethenes with Indole Groups
Authors: Yagi Kyoko , Irie Masahiro 
Published: August 2003

Abstract
Diarylethenes having a fluorescent indole ring as the aryl group 1a and 2a were synthesized. Upon alternate irradiation with 366 nm and visible (λ &gt; 480 nm) light, 1a underwent reversible photocyclization reactions to produce closed-ring isomer 1b. The fluorescence intensity also reversibly changed along with the reactions. The fluorescence quantum yields of the open-ring isomers 1a and 2a were 4.6 and 6.3% respectively, while the yields of the closed-ring isomers 1b and 2b were almost zero. The fluorescence quantum yields decreased with the increase in the photocyclization quantum yields.
Catalytic and Stereoselective Glycosylation with Glucosyl Thioformimidates
Authors: Chiba Hiroyuki , Funasaka Setsuo , Mukaiyama Teruaki 
Published: August 2003

Abstract
A novel and efficient glycosyl donor having a p-trifluoromethylbenzylthio-N-p-trifluoromethylphenylformimidate group at an anomeric position is easily prepared by the addition of anomeric hydroxy group of 2,3,4,6-tetra-O-benzyl-α,β-d-glucopyranose to p-trifluoromethylphenyl isothiocyanate, followed by treatment with p-trifluoromethylbenzyl bromide. Catalytic and stereoselective glycosylation of various glycosyl acceptors with the above glycosyl donor smoothly proceeds by using various protic and Lewis acid catalysts which interact with its nitrogen atom. Further, catalytic and highly 1,2-cis or 1,2-trans stereoselective and chemoselective glycosylation between two different “armed” and “disarmed” glycosyl p-trifluoromethylbenzylthio-N-p-trifluoromethylphenylformimidates is also performed effectively in the presence of a catalytic amount of trifluoromethanesulfonic acid (TfOH) at −78 °C in tBuOMe or EtCN, respectively. These glycosylations are applied to successful one-pot sequential syntheses of trisaccharides.
Efficient Method for the Preparation of Carboxylic Acid Alkyl Esters or Alkyl Phenyl Ethers by a New-Type of Oxidation–Reduction Condensation Using 2,6-Dimethyl-1,4-benzoquinone and Alkoxydiphenylphosphines
Authors: Shintou Taichi , Kikuchi Wataru , Mukaiyama Teruaki 
Published: August 2003

Abstract
A new-type of oxidation–reduction condensation proceeded smoothly to afford carboxylic acid alkyl esters or alkyl phenyl ethers in good to high yields by combined use of alkoxydiphenylphosphines (1) having primary, bulky secondary or tertiary alkoxy groups, a mild quinone-type oxidant such as 2,6-dimethyl-1,4-benzoquinone (DMBQ) and carboxylic acids or phenols. Generally, alkoxydiphenylphosphines were prepared easily from chlorodiphenylphosphine (2) and alcohols in the presence of pyridine, and were isolated by distillation. On the other hand, the phosphines 1 were also prepared in situ from N,N-dimethylaminodiphenylphosphine (3a) and primary or secondary alcohols while primary, bulky secondary or tertiary alkoxydiphenylphosphines were alternatively formed in situ by adding 2 to the nBuLi-treated alcohols in order to perform the above reactions by a one-pot procedure from alcohols and nucleophiles. The reaction of thus formed 1, DMBQ and carboxylic acids or phenols afforded the corresponding alkylated products, including hindered secondary and tertiary alkylated ones, in good to high yields at room temperature. In the case of using chiral secondary alcohols, the corresponding carboxylic acid alkyl esters were obtained as well in high yields with perfect inversion of stereochemistry by SN2 replacement.
Structure of the Hydration Product of the C60-Di(2-pyridyl)-1,2,4,5-tetrazine Adduct
Authors: Murata Yasujiro , Suzuki Mitsuharu , Rubin Yves , Komatsu Koichi 
Published: August 2003

Abstract
A solid-state reaction of fullerene C60 with 3,6-di(2-pyridyl)-1,2,4,5-tetrazine using the high-speed vibration milling technique gives almost quantitatively the monoadduct 2, which is transformed in high yield upon contact with silica gel to a novel 1,2,3,4-tetrahydro-C60 derivative 3 having a 2-pyrazoline ring fused at unusual 2,3-positions of the C60 framework. This unexpected product is the result of the addition of a water molecule to an imine moiety of 2, followed by a series of rearrangements.
1,4-Diazabicyclo[2.2.2]octane 1,4-Bis(oxide)-Bis(hydrogen peroxide)/MClx as a Novel Heterogeneous System for the Oxidation of Urazoles under Mild Conditions
Authors: Zolfigol Mohammad Ali , Salehi Peyman , Mallakpour Shadpour E , Torabi Mehdi 
Published: August 2003

Abstract
A combination of inorganic hydrolyzable chloride salts and 1,4-diazabicyclo[2.2.2]octane 1,4-bis(oxide)-bis(hydrogen peroxide), DABCO-DNODP, in the presence of wet SiO2 is used as an effective oxidizing agent for the oxidation of urazoles and bis-urazoles to their corresponding triazolinediones under mild and heterogeneous conditions with good to excellent yields.
Wittig Reaction by Using DBU as a Base
Authors: Okuma Kentaro , Sakai Osami , Shioji Kosei 
Published: August 2003

Abstract
The reaction of methyltriphenylphosphonium bromide with DBU in refluxing dichloromethane or toluene afforded methylenetriphenylphosphorane, which further reacted with benzaldehydes to give styrenes in good yields. Semistabilized ylide, benzylidenetriphenylphosphorane was also synthesized by using DBU, which reacted with aldehydes to afford olefins in nearly quantitative yields.
A New Catalytic System Consisting of Mo for Acetic Acid Synthesis from Methane and CO
Authors: Kitamura Tsugio , Ishida Yusuke , Yamaji Teizo , Fujiwara Yuzo 
Published: August 2003

Abstract
In trifluoroacetic acid (TFA), methane and CO can be converted to acetic acid by a new catalytic system, Mo/CaCl2/K2S2O8/TFA. The best result (89.4% of acetic acid) was obtained in a reaction of methane (20 atm) and CO (50 atm) using the catalytic system at 85 °C for 20 h.
2-Phenylthioallylation of Aldehydes with Allyl Phenyl Sulfides via Dibromination, Followed by Dehydrobromination
Authors: Masuyama Yoshiro , Sano Takehiro , Oshima Michihito , Kurusu Yasuhiko 
Published: August 2003

Abstract
2-Phenylthioallyl bromides, derived from allyl phenyl sulfides via dibromination, followed by dehydrobromination, cause the 2-phenylthioallylation of aldehydes with tin(II) iodide, tetrabutylammonium iodide and sodium iodide in 1,3-dimethylimidazolidin-2-one to produce the corresponding 1-substituted 3-phenylthiohomoallyl alcohols.
Decomposition of Phenolic Endocrine Disrupting Chemicals by Potassium Permanganate and γ-Ray Irradiation
Authors: Abe Yasuhiro , Takigami Machiko , Sugino Kouji , Taguchi Mitsumasa , Kojima Takuji , Umemura Tomonari , Tsunoda Kin-ichi 
Published: August 2003

Abstract
The decomposition of phenolic endocrine disrupting chemicals (P-EDCs), such as phenol, 4-t-butylphenol (BuP), and bisphenol A (BPA), in aqueous solutions by potassium permanganate (KMnO4) was studied, and its efficiency was compared with that of hydroxyl radicals (OH•) generated by 60Co γ-ray irradiation. Various organic acids and inorganic carbon were formed in the decomposition of P-EDCs due to either KMnO4 or OH•. They were formed via direct aromatic ring cleavage in the case of KMnO4 and via OH• addition-substitution reactions, followed by aromatic ring cleavage, in the case of OH•. Comparing the decrease in the P-EDCs based on the number of electrons, the amount of KMnO4 spent to completely eliminate BuP and BPA was comparable to that of OH•. Although three-times more KMnO4 was needed for phenol decomposition than OH•, the complete conversion of phenol into organic acids and inorganic carbon was achieved with 720 μM of electrons in both cases.