bluuebunny/crossref_metadata_2025_split huggingface dataset:
Weak Antiferromagnetism in a μ-Alkoxo-μ-Pyrazolato-Bridged Dinuclear Vanadium(IV) Complex
Authors: Mikuriya Masahiro , Minowa Kenichi , Nagao Nobuyuki 
Published: September 2002

Abstract
A vanadium(IV) complex with 2-hydroxy-N,N′-bis(1-methyl-3-hydroxy-3-phenyl-2-propen-1-ylidene)-1,3-propane-diamine (H3L), [(VO)2(L)(pz)] (Hpz = pyrazole), was synthesized and characterized by measurements of the magnetic moment and the electronic spectra. The X-ray crystal structure analysis shows that the compound has a dinuclear structure with two square-pyramidal N2O3 coordination environments, which are bridged by the alkoxo and the pyrazolato groups. The antiferromagnetic interaction between the two metal atoms is fairly weak.
Transformation of Isatin 3-Acylhydrazones under Acetylating Conditions: Synthesis and Structure Elucidation of 1,5′-Disubstituted 3′-Acetylspiro[oxindole-3,2′-[1,3,4]oxadiazolines]
Authors: Somogyi László 
Published: September 2002

Abstract
Several substituted isatin 3-acylhydrazones (e.g. 1a–k, n, p, t) have been synthesized. Under acetylating conditions they were transformed into selectively acetylated derivatives (e.g., 1l, n, o, q–s) and into the novel, title spiroheterocycles (2a–i). Some side reactions occurring under various acetylating conditions are also discussed.
Allosteric Binding of K+ to Crown Ether Macrocycles Appended to a Lanthanum Double Decker System
Authors: Robertson Andrew , Ikeda Masato , Takeuchi Masayuki , Shinkai Seiji 
Published: September 2002

Abstract
A benzocrown-appended lanthanum(III) porphyrin double decker has been synthesized which is capable of binding simple K+ in a cooperative, allosteric fashion to form a 1 : 4 complex. Analysis of this system by means of the Hill equation gave an overall binding constant (Kb) of 1.0 × 1014 (mol dm−3)−4 and a Hill coefficient of 4.0. This same system, however, binds Na+ in a conventional, linear fashion. These results indicate that the novel allosteric binding occurs as the result of 1 : 2 sandwich complexes between K+ and appended crown ether moieties of the two joined porphyrins. The suitability of lanthanum(III) over cerium(IV) for preparing this highly crowded double decker porphyrin is also noted.
Synthesis and Properties of Head-to-head, Head-to-tail, and Tail-to-tail Orientational Isomers of Extended Dihexylbithiophene–Octaethylporphyrin System [OEP–(DHBT)n–OEP] Connected with 1,3-Butadiyne Linkages
Authors: Higuchi Hiroyuki , Ishikura Takashi , Mori Kazumine , Takayama Yukari , Yamamoto Koji , Tani Keita , Miyabayashi Keiko , Miyake Mikio 
Published: September 2002

Abstract
An extended π-electronic conjugation system of dihexylbithiophene–octaethylporphyrin [OEP–(DHBT)n–OEP; n = 1–5], all the chromophores in which are connected with the linkage of 1,3-butadiyne (diacetylene), was synthesized by an oxidative cross-coupling reaction of the corresponding terminal acetylenes. Absorption spectral and electrochemical properties of the OEP–(DHBT)n–OEP system were examined. The results proved that the orientation of two 3-hexylthiophene (3HTh) rings of DHBT plays an important role in electronic communications between the two terminal OEP rings.
Stacked Porphyrin Arrays from Hydrogen-Bonded Porphyrin–Resorcinol 1D Chains
Authors: Tanaka Toshihiro , Endo Ken , Aoyama Yasuhiro 
Published: September 2002

Abstract
The Ni(II) complex of monoresorcinol derivative of a sterically unhindered tetraalkylporphyrin (3) affords adducts 3•(methanol) and 3•1.5(acetophenone). In the crystals, porphyrin 3 forms hydrogen-bonded (O–H···O–H) polyresorcinol chains with the porphyrin residues sticking out of the chains. The chains are self-assembled in such a manner as to give closely stacked interchain porphyrin columns, while the guest molecules are either firmly bound to the hydrogen-bonding sites (in the case of methanol) or incorporated in the channels running in parallel with the porphyrin stacks (in the case of acetophenone). The formation of such a stacked porphyrin array is not observed when the guest is changed to 4-heptanone or when the porphyrin is changed to a sterically hindered one 4 or 5 with full substitution at the meso- or the β-positions. The mode of interchain porphyrin stacking is discussed in light of the crystal structures of adducts 3•(4-heptanone), 4•pyridine, and 5•(2-nonanone).
Mechanistic Considerations on the Oxime–Nitrone Isomerization and Intramolecular Cycloaddition Reaction of 3-(Alk-2-enylamino)propionaldehyde Oximes
Authors: Noguchi Michihiko , Okada Hirofumi , Tanaka Masayuki , Matsumoto Satoshi , Kakehi Akikazu , Yamamoto Hidetoshi 
Published: September 2002

Abstract
3-(Alk-2-enylamino)- and 3-(acryloylamino)-2,2-dimethylpropionaldehyde oximes underwent thermally induced 1,3-dipolar cycloaddition under mild conditions, leading to perhydroisoxazolo[4,3-c]pyridine derivatives. The features of the intramolecular oxime–olefin cycloaddition in this system and the roles of the geminal methyl groups at the 2-position and the alkenylamino nitrogen in the oxime–nitrone isomerization process are discussed based on kinetic studies.
Kinetic Analysis of the Temperature Dependence of the Template-Directed Formation of Oligoguanylate from the 5′-Phosphorimidazolide of Guanosine on a Poly(C) Template with Zn2+
Authors: Kawamura Kunio , Umehara Masatosi 
Published: September 2002

Abstract
A kinetic study of the temperature dependence of the template-directed formation of oligoguanylate (oligo(G)) on polycytidylic acid (poly(C)) from the 5′-phosphorimidazolide of guanosine (ImpG) has been carried out in the presence of Zn2+ at 40–80 °C. It is surprising that a large amount of oligo(G) was formed at 40–60 °C and a small amount of oligo(G) was detected even at 80 °C. The rate constants of the template-directed formation of oligo(G) were determined at 40–60 °C, and the same trend, the rate constants increase with the chain length, was observed as that at lower temperatures. Besides, second-order rate plots of the hydrolyses of ImpG and oligo(G) were consistent with pseudo-second-order processes in the presence of 0.04 M Zn2+. The apparent activation energy determined from the Arrhenius plots decreases in the order hydrolysis of oligo(G) &gt; formation of 4-mer ≈ formation of 3-mer ≈ hydrolysis of ImpG &gt; formation of 2-mer. The kinetic analysis and computer simulations demonstrate the importance of the rate of 2-mer formation to determine the efficiency of the oligo(G) formation.
Preparation and Lectin Binding Property of Chitosan–Carbohydrate Conjugates
Authors: Sashiwa Hitoshi , Shigemasa Yoshihiro , Roy Renè 
Published: September 2002

Abstract
Chitosan–sialic acid conjugates were prepared using p-formylphenyl α-sialoside by reductive N-alkylation. The degree of substitution (DS) of conjugates could be controlled from 0.06 to 0.53 by the amount of sialoside. With the use of p-isothiocyanatophenyl α-sialoside, chitosan–sialic acid conjugates were also prepared with excellent efficiency. Chitosan–melibiose conjugates having α-galactosyl epitope were also prepared by reductive N-alkylation. These conjugates were transformed into water-soluble forms by N-succinylation and their protein binding property was tested using wheat germ agglutinin (WGA) or Griffonia simplicifolia (GSI-B4) lectin. Strong immunodiffusion bands were observed in all of conjugates, thus demonstrating the specific binding of epitope in conjugate to each lectins.
Kinetic Investigation on the Hydrolysis of Aryl(fluoro)(phenyl)-λ6-sulfanenitriles
Authors: Dong Tiaoling , Fujii Takayoshi , Murotani Satoro , Dai Huagang , Ono Shin , Morita Hiroyuki , Shimasaki Choichiro , Yoshimura Toshiaki 
Published: September 2002

Abstract
A kinetic investigation on the hydrolysis of aryl(fluoro)(phenyl)-λ6-sulfanenitriles was carried out in some aqueous and mixed aqueous-organic solutions. The pH-rate profiles showed that the hydrolysis consists of pH-independent, acid-catalyzed and base-catalyzed reactions. The neutral hydrolysis of fluoro-λ6-sulfanenitriles was found to proceed via an SN1 or an S-nitrilosulfonium cation-like transition state, which is characterized by a large negative Hammett ρ-value (ρ = −1.76 in water; −1.85 in CH3CN/H2O(1/4, v/v); −2.35 in TFE/H2O (1/1, v/v)), relatively large m-values (ca. 0.83 for fluoro(diphenyl)-λ6-sulfanenitrile; ca. 0.82 for fluoro(p-nitrophenyl)(phenyl)-λ6-sulfanenitrile against the solvent ionizing power YOTs-values in acetonitrile–water), a common ion effect in TFE/H2O, and a small salt effect. The large negative activation entropies (−60 – −101 J K−1 mol−1) were presumed to be due to strong solvation of F− with H2O in the reaction systems. The ease of ion dissociation of the S–F bond was examined by a theoretical calculation in a DFT method, to show that the SN1-like transition state is caused by a facile tendency of dissociation of the S–F bond of fluoro-λ6-sulfanenitriles. The acid-catalyzed hydrolysis was found to proceed via a more cation-like transition state involving a concerted proton transfer to the fluorine atom and breaking of the sulfur-fluorine bond in the λ6-sulfanenitrile. The alkaline hydrolysis probably takes place via an SN2 mechanism.
Asymmetric Bis(alkoxycarbonylation) Reaction of Terminal Olefins Catalyzed by Palladium in the Presence of Copper(I) Triflate and a Chiral Bioxazoline Ligand
Authors: Takeuchi Susumu , Ukaji Yutaka , Inomata Katsuhiko 
Published: September 2002

Abstract
A palladium-catalyzed asymmetric bis(alkoxycarbonylation) reaction of terminal olefins in the presence of copper(I) triflate was achieved by using a chiral bioxazoline ligand, (4S,4′S)-4,4′-dibenzyl-4,4′,5,5′-tetrahydro-2,2′-bioxazole, under normal pressure of carbon monoxide and oxygen at 25 °C to give the corresponding optically active mono-substituted succinates with enantioselectivity up to 66% ee.
Conformational Preference of β-Aryldehydroalanine. Solid-State Conformation of Tripeptide Possessing a (Z)-β-(1-Pyrenyl)dehydroalanine Residue in the Second Position
Authors: Inai Yoshihito , Oshikawa Tatsuo , Yamashita Mitsuji , Hirabayashi Tadamichi , Kurokawa Yuji 
Published: September 2002

Abstract
In this paper we attempted to reveal how a large β-substituent (pyrenyl group) of dehydroresidue affects the structural and conformational preferences of (Z)-β-substituted α,α-dehydroalanine. An X-ray crystallographic analysis was carried out for Boc–l-Ala–ΔZPyr–l-Val–OMe (Boc = t-butyloxycarbonyl; OMe = methoxy) possessing a novel (Z)-β-(1-pyrenyl)dehydroalanine (ΔZPyr) residue. Single crystals were obtained by slow evaporation from an ethanol solution in the monoclinic space group P21. The bond lengths and bond angles of the ΔZPyr residue were essentially similar to other β-substituted dehydroalanines. The tripeptide took a type II β-turn conformation involving an intramolecular hydrogen bond between CO(Boc) and NH(Val), like small peptides possessing a (Z)-β-(1-naphthyl)dehydroalanine or a (Z)-β-phenyldehydroalanine residue. The similarity between ΔZPyr and other dehydroalanines in structural property and conformational preference should be responsible for the non-planarity of the ΔZPyr residue to give an extremely high energy in the planar orientation of the pyrenyl group relative to the Cα=Cβ-Cγ plane; the non-planarity should weaken the π-conjugation effect of the pyrenyl group on the structural property and conformational preference of the ΔZPyr residue. The pyrenyl rings were packed in a partially overlapped face-to-face orientation with the shortest center-to-center distance of 5.96 Å. The CD spectrum of a KBr disk prepared from the crystal showed strong excitonic interactions between pyrenyl groups, reflecting a regular arrangement of the pyrenyl groups in the crystal structure.
Synthesis of 2H-Chromenes through the Reduction of Chromones with 9-BBN
Authors: Eguchi Tetsuya , Hoshino Yukio 
Published: September 2002

Abstract
Chromones were regioselectively reduced to 2H-1-benzopyrans through the 1,2-addition of 9-borabicyclo[3.3.1]nonane. Although transition-metal complexes did not have a catalytic effect on the reaction, only by using palladium(II) chloride, could both 2H-1-benzopyran and dihydro-1-benzopyran be obtained to a similar extent. Also, the reduction of chromone using other organoboranes led not to 2H-1-benzopyran, but rather to chromanone through the reduction of only an olefin moiety.
Synthesis, Crystal Structure, and Some Spectrochemical Properties of S-Bridged Hexanuclear Zinc(II) Complex with 2-Aminoethanethiolate: Formation of Zn3S3- and Zn4S4-Cyclic Cores
Authors: Yamada Yasunori , Miyashita Yoshitaro , Fujisawa Kiyoshi , Okamoto Ken-ichi 
Published: September 2002

Abstract
The reaction of [Zn(aet)2] (aet = 2-aminoethanethiolate) with Zn(ClO4)2•6H2O in aqueous acetonitrile gave an S-bridged hexanuclear complex, [{Zn(aet)}4{Zn(aet)2}2]4+, accompanied by the ligand-transfer of aet from [Zn(aet)2] units to Zn2+ ions. In the hexanuclear complex, all of the Zn and S atoms are included in the Zn3S3- and/or Zn4S4-cyclic structures.
Intramolecular Cyclizations of o-Substituted β,β-Difluorostyrenes: Synthesis of 3-Fluorinated Isochromenes and Isothiochromenes
Authors: Wada Yukinori , Ichikawa Junji , Katsume Tadayuki , Nohiro Tomoko , Okauchi Tatsuo , Minami Toru 
Published: September 2002

Abstract
β,β-Difluorostyrenes bearing an oxygen (OH) or a sulfur (SH, SCOCH3) nucleophile linked by a methylene unit to the ortho carbon are prepared from 2,2,2-trifluoroethyl p-toluenesulfonate via the in situ generation of 2,2-difluorovinylboranes and their palladium-catalyzed cross-coupling reaction with aryl iodides. These styrene derivatives readily undergo intramolecular nucleophilic substitution of the oxygen and sulfur with loss of fluorine under basic conditions, leading to 3-fluoroisochromenes and 3-fluoroisothiochromenes in high yields.
Synthesis and Properties of a Series of the Longest Oligothiophenes up to the 48-mer
Authors: Sumi Naoto , Nakanishi Hidetaka , Ueno Shinpei , Takimiya Kazuo , Aso Yoshio , Otsubo Tetsuo 
Published: September 2002

Abstract
A series of the longest class of oligothiophenes extended at intervals of seven thiophene units from the 6-mer up to the 48-mer has been synthesized by a combination of the random Eglinton coupling reaction of mono- and di-ethynylsexithiophenes and a subsequent sodium sulfide-induced cyclization reaction of the resulting oligo(sexithienylene-diethynylene)s. Their structures were well characterized by MALDI-TOF MS and 1H NMR spectroscopy. The molecular weights of the oligothiophenes and oligo(sexithienylene-diethynylene)s, measured by gel-permeation liquid chromatography using the polystyrene standard, are nearly double the actual ones, indicating that they keep highly rigid rod-type shapes. According to a molecular model, the molecular lengths of the longest oligothiophene 48-mer and the longest oligo(sexithienylene-diethynylene) reach approximately 18.6 nm and 25.0 nm, respectively. In the electronic absorption and emission spectra, the π–π* transitions of the oligothiophenes demonstrate progressive red shifts with increasing chain length up to the 20-mer. In the cyclic voltammograms, furthermore, the first oxidation potentials tend to continue negative shifts up to the 34-mer. In accordance with these spectral changes, the doped conductivities steadily increase and approach that of a structurally related polymer.
Syntheses of Chiral Solid Catalysts Using Menthol and Application to the Asymmetric Diels–Alder Reaction
Authors: Nagasawa Tomomi , Kudo Nozomi , Hida Yoshiyuki , Ito Kazuaki , Ohba Yoshihiro 
Published: September 2002

Abstract
A chiral solid catalyst as a heterogeneous Lewis acid prepared from trimethylaluminum, menthol and tetrachlorobisphenol A has been found to promote the asymmetric Diels–Alder reaction of 2-methyl-2-propenal with cyclopentadiene and is a reuseable catalyst.
Monodentate, Didentate, and Tridentate Ligation of a Schiff-Base Ligand in a Tetranuclear Zinc(II) Complex
Authors: Mikuriya Masahiro , Ikemi Shinichiro , Lim Jong-Wan 
Published: September 2002

Abstract
A tetranuclear zinc(II) complex with 2,6-bis(salicylideneaminomethyl)-4-methylphenol (H3L), [Zn4(L)2(pz)2]•2CH3CN (Hpz = pyrazole), was synthesized and characterized by 1H NMR spectroscopy and a single-crystal X-ray diffraction method. Each Schiff-base L3- acts as a monodentate, a didentate, and a tridentate ligand for four zinc atoms to form a Z-shaped tetranuclear structure.
A Novel Photosensitive Silicone Ladder Polymer: Synthesis, Photochemical, and Thermal Characteristics
Authors: Yasuda Naoki , Yamamoto Shigeyuki , Adachi Hiroshi , Nagae Suguru , Wada Yuji , Yanagida Shozo 
Published: September 2002

Abstract
A negative working photosensitive silicone ladder polymer (PVSQ) based on polyphenylsilsesquioxane with vinyl groups as a reactive substituents in the side chain, and 2,6-bis(azidobenzylidene)-4-methylcyclohexanone (BA) as a photocrosslinker, has been developed. The monodisperse PVSQ was synthesized by co-polymerization of trichlorophenylsilane and trichloro(vinyl)silane with potassium hydroxide in isobutyl methyl ketone. The PVSQ film showed excellent transparency above 280 nm and high solubility in organic solvents. The photosensitive PVSQ containing 3 wt% of BA showed the sensitivity of 40 mJ cm−2 when it was exposed to 365 nm light (i-line) followed by development with a mixture solution of anisole and xylene at 25 °C. The photosensitive PVSQ film also showed high thermal stability (decomposition temperature: 520 °C) and low dielectric constant (3.2/1 MHz), demonstrating a high potential for application to LSI production.
Convenient Route to Both Enantiomerically Pure Forms of trans-4,5-Dihydroxy-2-cyclopenten-1-one: Efficient Synthesis of the Neocarzinostatin Chromophore Core
Authors: Toyama Koji , Iguchi Satoru , Sakazaki Hayato , Oishi Tohru , Hirama Masahiro 
Published: September 2002

Abstract
An enantioselective synthesis of an epoxybicyclo[7.3.0]dodecenediyne core system of the neocarzinostatin chromophore has been achieved via intramolecular acetylide addition and palladium-mediated coupling of iodocyclopentene 5 with alkyne 6. The key cyclopentene moiety, trans-4,5-dihydroxy-2-cyclopenten-1-one 7, was conveniently prepared in both enantiomerically pure forms via enzymatic desymmetrization of meso-3,4,5-trans,trans-trihydroxycyclopentene derivatives.
Design, Synthesis, Structure, and Spectroscopic and Electrochemical Properties of Phthalocyanines
Authors: Kobayashi Nagao 
Published: September 2002

Abstract
The synthesis and spectroscopic and electrochemical properties of crown-ether substituted metallophthalocyanines (MCRPcs), optically active phthalocyanines (Pcs), subphthalocyanines (SubPcs), low symmetrical Pcs, ring-expanded Pcs, and novel oligomers of Pcs studied mainly by the author over the last 20 years have been reviewed, together with the electrocatalytic reduction of dioxygen using water soluble Pcs. MCRPcs form, on addition of certain kinds of cation, cofacial dimers through a two-step three-stage process. SubPcs react with isoindolediimines to produce mono-substituted Pc and Pc analogues. Optically active Pcs have been prepared to show the beauty and usefulness of circular dichroism spectroscopy. Ring-expanded or -shrunk and low symmetrical Pc analogues have helped in exploiting the relationship between size, symmetry, and spectroscopic and electrochemical properties of large aromatic molecules. Molecular orbital calculations on these compounds have succeeded in reproducing many of the experimental properties. New types of cofacial and planar dimers have been prepared, occasionally with a new concept. Water-soluble iron and cobalt Pcs electrocatalyze the reduction of dioxygen. When a four-electron reduction was attained, the reduction proceeded via hydrogen peroxide, and could be explained by a mechanism of electrochemical catalyst regeneration. The results for these compounds are occasionally compared with those of porphyrin systems.
Resonance Raman Spectra of Cytochrome c Oxidase in Whole Mitochondria
Authors: Takahashi Toshinari , Ogura Takashi 
Published: September 2002

Abstract
Resonance Raman spectra of cytochrome c oxidase in intact whole mitochondria were selectively observed. The Raman bands observed at 576, 517, and 369 cm-1 for the carbon monoxide-bound state were assigned to the δFe–C–O, νFe–CO, and δFe–C–O modes, respectively, of heme a3-CO complex based on the 13C18O isotopic frequency shifts. These frequencies are essentially the same as those observed for solubilized cytochrome c oxidase, which implies that the environmental structure of the dioxygen reducing site in the solubilized state is not very much altered. It is likely that the dioxygen reducing reaction studied so far for solubilized enzyme is also valid for intact whole mitochondria.
Optimizing Vibrational Population Transfer at Surfaces through Infrared Excitation
Authors: Bonn Mischa , Wolf Martin 
Published: September 2002

Abstract
We present an experimental and theoretical study of vibrational excitation of the C–O stretch vibration of carbon monoxide adsorbed on a ruthenium Ru(001) surface with ultrashort femtosecond infrared (IR) laser pulses. Broadband IR excitation leads to the transfer of a significant fraction of the CO molecules to their first (∼15%) and second (∼5%) vibrationally excited states. We reproduce the observed excited state spectra by solving the three-level Bloch equations and discuss possibilities to optimize the degree of localized vibrational excitation of a specific bond of surface molecules through IR excitation by tuning the pulse duration and central frequency.
Developing Vibrational Infrared Near Field Spectroscopy to Characterize Polymer Structures on Surfaces: Identification and Reduction of Topographic Coupling Artifacts
Authors: Akhremitchev Boris B , Walker Gilbert C 
Published: September 2002

Abstract
We report efforts to develop infrared near field microscopy for the characterization of polymer surfaces. The new near field microscope is adapted from an atomic force microscope with custom optics to create a high spatial resolution imaging platform. In addition, we report developments of analytical and finite difference approaches relating the rough sample/light interaction, the resultant near field optical signal, and the chemical structure of the sample. Simulations of the role of a topographic coupling artifact of the observed near field signal, and a method to overcome that artifact are presented.
Time-Resolved Infrared Absorption Studies of Surface OH Groups on TiO2 Particles Irradiated by UV Pulses
Authors: Yamakata Akira , Ishibashi Taka-aki , Onishi Hiroshi 
Published: September 2002

Abstract
The shift of vibrational frequency of surface OH groups on TiO2 particles induced by UV pulse irradiation has been studied by time-resolved IR absorption spectroscopy. By the UV irradiation of the TiO2 particles, the absorption intensity at 3696 cm-1 was decreased and that at 3654 cm-1 was increased. These changes were gradually recovered on a millisecond time scale. The transient changes were interpreted by a small (&lt; 0.1 cm-1) shift of a ν(O–H) band at 3677 cm-1. The temperature jump triggered by the UV pulse caused the shift.