bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Soluble Complexan Polymers in Organic Solvents for Using as a Polymer–Chelate Precursor to YBa2Cu3O7-x Thin Films
Authors: Naka Kensuke , Tanaka Yasuyuki , Yamasaki Kunitoshi , Ohki Akira , Chujo Yoshiki , Maeda Shigeru 
Published: September 2002

Abstract
A soluble complexan polymer in organic solvents, derived from 1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA), was synthesized and used as a polymer chelate precursor to YBa2Cu3O7-x thin films. Five complexan polymers (3) were prepared by a ring-opening polyaddition of CyDTA dianhydride (1) with several diamines (2). The polymer (3e) prepared with 1,2-diaminocyclohexane (2e) was soluble in water, dimethyl sulfoxide (DMSO), methanol, and ethanol. A clear aqueous solution (pH 8) containing 3e and 1/2 equivalent molar amount of metal nitrates of Y, Ba, and Cu (1 : 2 : 3 in molar ratio) was poured into tetrahydrofurane (THF) to precipitate a polymer–metal chelate. The chelate formations of each metal were confirmed by C=O stretching bonds. The polymer chelate precursor was soluble in methanol, DMSO, and water, and partially soluble in ethanol. The polymer–metal chelate was dissolved in methanol, of which the metal concentration was adjusted to 3 wt%. This solution was spin-coated onto SrTiO3 (100) and MgO (001) substrates for preparing YBa2Cu3O7-x thin films. According to an X-ray diffraction analysis, YBa2Cu3O7-x film with a c-axis orientation was formed on a SrTiO3 substrate; even the precursor film was sintered at 780 °C for 1 h under air. Superconducting YBa2Cu3O7-x films with a c-axis orientation were also prepared on a MgO (001) substrate.
VUV Laser Chemistry—Formation of Hot Molecules and Their Reactions in the Gas Phase—
Authors: Yatsuhashi Tomoyuki , Nakashima Nobuaki 
Published: September 2002

Abstract
The hot molecule (S0**) is in a highly vibrationally excited state formed by rapid internal conversion from initially prepared electronic excited states. The importance and predominance of the S0** mechanism in VUV gas phase photochemistry has been demonstrated. In this account, the fundamental physicochemical properties of S0** are discussed in order to understand the characteristic features of S0** reactions, and VUV laser chemistry is reviewed from the following two points of view: 1) The generalization and classification of VUV chemistry for a variety of molecules, including the hot molecule mechanism and other competitive mechanisms; 2) A new strategy of multiphoton chemistry that employs hot molecule as an intermediate. Internal conversion is a dominant deactivation process for many molecules in the VUV region. Aromatic hydrocarbons and olefins are the representative examples of S0** reactions. However, fluorescence and intersystem crossing are major deactivation processes in some cases such as large condensed aromatic hydrocarbons. The reactions of chlorinated compounds and phenols are explained by other reaction mechanisms such as direct dissociation and predissociation. Carbonyl compounds and some amines are classified into the intermediate cases. Due to the large molar extinction coefficient and relatively long lifetime of S0**, the multiphoton absorption process can be induced by a single nanosecond laser pulse. As a result of fast internal conversion and intramolecular energy redistribution, the second photon and further photons will not be absorbed by the molecule in the electronic excited state but by that in the S0**, and the photon energy of the multiphoton is accumulated as vibrational energy. Therefore, ionization is minor process in the case of the multiphoton reaction of S0**. The neutral radical formation is predominant in the dissociation reaction, and the rate constant increases because the internal energy is multiplied by the multiphoton absorption process. The applications of these findings lie in the following: 1) Large molecules of which the single-photon hot molecule reaction rate is small; 2) Molecules which have been deemed to be photoinert.
Tetrathiapentalene Derivatives with Long Alkyl Chains
Authors: Kimura Shinya , Kurai Hiroyuki , Mori Takehiko , Mori Hatsumi , Tanaka Shoji 
Published: September 2002

Abstract
Bis-fused π-electron donors having alkylthio chains, CnTET-TTP (2-[4,5-bis(alkylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene; n = 2–4) have been synthesized. C2TET-TTP (1a) forms radical-cation salts with BF4- and ClO4-, which are metallic (σrt = 900-2500 S cm-1) down to helium temperatures. The I3 salts of C3TET-TTP (1b) and C4TET-TTP (1c) are semiconductive from room temperature (σrt = 0.041 and 0.025 S cm-1, respectively). (C2TET-TTP)2ClO4 has uniform stacks of the donors, and hats an elliptical Fermi surface characteristic of two-dimensional metals. (C4TET-TTP)I3 is dimeric, and can be regarded as a band insulator. These crystal structures demonstrate the tendency that the long alkyl chains increase the anion content, and stabilize the usual stacking structure as well as the dimerization.
Energy Transfer from Photoexcited Electronic States to the Thermal Modes
Authors: Terazima Masahide 
Published: September 2002

Abstract
Energy transfer processes from a photoexcited ion and molecules to solvents were studied from the rate of the temperature rise of the solvent using several newly developed techniques: temperature grating, temperature lens, acoustic peak delay, and molecular heater–molecular thermometer methods. These energy transfer processes are closely related to the well-studied vibrational relaxation (cooling) process but the overall energy transfer process can be monitored by detecting the time course of the matrix heating. In aqueous solution, most of the energy of a photoexcited ion transfers to the thermal mode within 2–3 ps after the populational relaxation to a lower electronic state. In organic solvents, the process is described by roughly two kinetics: fast ( ≤ 1 ps) and slow (20–30 ps). This two-phase kinetics was explained by a simple thermalization model; the initial fast process represents the energy transfer to the doorway molecules in the first solvent shell molecules and the slower one represents the thermal diffusion process from the hot solvent molecules to the bulk solvent molecules. A new molecular heater-molecular thermometer integrated system is also described.
Enzymatic Polymerization for Precision Polymer Synthesis
Authors: Kobayashi Shiro , Uyama Hiroshi , Ohmae Masashi 
Published: September 2002

Abstract
Our recent advances in enzymatic polymerization, defined as chemical polymer syntheses in vitro (in test tubes) via non-biosynthetic pathways catalyzed by an isolated enzyme, have been mainly reviewed. The major target macromolecules formed via the enzymatic polymerizations described in this article are polysaccharides, polyesters, and polyaromatics. For synthesis of polysaccharides and polyesters, hydrolases are used as catalysts; hydrolases catalyzing a bond-cleavage reaction by water induce the reverse reaction of hydrolysis, leading to polymer production by a bond-forming reaction in vitro. Specific enzyme catalysis provides a novel synthetic route with precise structure control not only for natural biopolymers such as cellulose, xylan, and chitin, but also for unnatural polysaccharides and polyesters, many of which are difficult to be synthesized by conventional methodologies. Oxidoreductases act as catalysts for oxidative polymerization of phenol, aniline, and their derivatives. A new class of phenolic polymers are synthesized without use of toxic formaldehyde under mild reaction conditions. Enzyme-model complexes also catalyze polymerizations for the synthesis of new high-performance polymeric materials.
Dimerization–Carbostannylation of Alkynes Catalyzed by a Palladium–Diimine Complex: Regioselectivity, Stereoselectivity and Mechanism
Authors: Yoshida Hiroto , Shirakawa Eiji , Nakao Yoshiaki , Honda Yuki , Hiyama Tamejiro 
Published: September 2002

Abstract
Double insertion of alkynes into the C–Sn bond of an alkynyl-, alkenyl-, allyl- or arylstannane proceeded in the presence of a palladium–diimine complex to afford highly conjugated alkenylstannanes with exclusive syn selectivity. Perfect regioselectivities were observed in the dimerization–carbostannylation of ethyl propiolate with a palladium–1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene complex, which allowed regio- and stereoselective synthesis of stannyl-substituted muconic acid derivatives. The π-conjugation of the dimerization–carbostannylation products was further extended through a cross-coupling or homocoupling reaction. A palladacyclopentadiene is proposed as an intermediate species.
Evaluation of Novel Local Structural Parameters of Acids and Bases for 1 : 1 Hydrogen-Bond Complexation. II. p-Fluorophenol, 5-Fluoroindole and Various Bases in Carbon Tetrachloride
Authors: Mishima Shozi , Nakajima Tsuyoshi , Tanaka Nobuaki 
Published: September 2002

Abstract
For 1 : 1 hydrogen-bond complexation in CCl4, novel local structural parameters, η° and ω°, representing the nature of the functional group and the residual moiety (supporting group) of acids and bases have been evaluated for two acids and 26 bases. An evaluation of the η° and ω° was carried out by using convergent linear relationships observed among the log K values of the bases against each couple of reference acids. The values of log K experimentally obtained were reproduced from the η°and ω° values within ±0.21 in the log K unit, excluding three exceptions. Family-independent linear relationships were observed between ω°b and the solute hydrogen bond basicity (β2H), and between ω°a and the solute hydrogen bond acidity (α2H) of the bases and acids. Linear relationships could be applied to estimate the ω°a and ω°b values from α2H and β2H values existing in the literature.
Magnetic Field Effects on the Lifetimes of Triplet Biradicals Photogenerated from Zinc(II) Tetraphenylporphyrin-Viologen Chain-Linked Compounds: Dependence on Spacer Chain Length and Environment
Authors: Ito Toshiyuki , Naka Masao , Miura Atsushi , Ujiie Tomomi , Nakamura Hiroshi , Matsuo Taku 
Published: September 2002

Abstract
The effects of magnetic fields on the lifetimes of chain-linked triplet biradicals (3BRs), generated by photoinduced electron transfer from zinc(II) tetraphenylporphyrin (ZnP) to appended viologen (V2+), were investigated in homogeneous solutions of acetonitrile-water and reversed micellar solutions of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) by means of laser flash photolysis. It was found that the decay rate constants (kobs) of the 3BRs increased significantly in the absence of magnetic fields as the number of carbon atoms (n) in the spacer chain between the ZnP and V2+ moieties increased, and then reached a constant value above n = 8. When the magnetic field was increased, the kobs values decreased. A sharp decrease in a low magnetic field was observed, followed by a gradual decrease as the magnetic field was increased, eventually reaching an asymptotic value under the high magnetic field (B &gt; 100 mT) for the compounds with the longer spacer chains. In AOT/2,2,4-trimethylpentane/water reversed micellar solutions, the kobs values were smaller than those in MeCN–H2O homogeneous solutions; this trend became increasingly prominent the longer the spacer chain length. Therefore, the kobs values showed the opposite spacer chain length dependence in comparison with those in homogeneous solutions at B = 470 mT. These results were interpreted in terms of the variation of triplet-singlet energy separation with the interradical distance, Zeeman splitting of the triplet sublevels, electron–nuclear hyperfine coupling, and spin relaxation mechanisms.
Determination of Acidity Constants of Perfluoroalkanoic Acids
Authors: Moroi Yoshikiyo , Yano Hiroaki , Shibata Osamu , Yonemitsu Tadashi 
Published: September 2002

Abstract
Acidity constants (Ka) of perfluoroalkanoic acids were determined by pH titration and by electric conductivity for shorter alkanoic acids (C1 to C5) with 1 to 5 carbon atoms in the alkyl chain. The acidity constants obtained by the two methods are in good agreement. They increase from C1 (ethanoic) to C3 (butanoic acid) and then decrease from C3 to C5 (hexanoic acid) with increasing alkyl chain length. An abrupt decrease in the Ka value for the C5 acid occurred; the attempt to explain this in terms of viscosity of the solutions did not succeeded. The decrease in the Ka values with increasing alkyl chain length was substantiated by the values for C9 (decanoic) to C11 (dodecanoic) acids, which were determined from the solubility change with the solution pH. For the intermediate alkanoic acids (C6 to C8), the Ka values could not be determined precisely by these methods due to the extreme difficulty in separating the colloidal acid particles from the aqueous phase, because the particles have an emulsifying action of their own.
Unique Axial Interaction of a Quadruply-Bonded Cr(II)-Cr(II) with Two Pt(II) Atoms in the Linearly Aligned Pt-Cr-Cr-Pt Supported by Four 6-Diphenylphosphino-2-pyridonate Ligands
Authors: Tanaka Mitsuhiro , Mashima Kazushi , Nishino Masamichi , Takeda Sadamu , Mori Wasuke , Tani Kazuhide , Yamaguchi Kizashi , Nakamura Akira 
Published: September 2002

Abstract
Linearly aligned tetranuclear Pt(II)-Cr(II)-Cr(II)-Pt(II) complexes were prepared using a tridentate pyphos ligand (pyphos = 6-diphenylphosphino-2-pyridonate). The bonding between Cr(II) and Pt(II) was discussed on the basis of magnetic measurements. A dichromium complex, [Cr2(pyphos)4] (1), was prepared by the reaction of [Cr2(OAc)4] with the sodium salt of pyphos ligand. The complex 1 has four phosphorus atoms capable of holding transition metals at both of the axial positions of the Cr2 moiety. Three tetranuclear Pt(II)-Cr(II)-Cr(II)-Pt(II) complexes, i.e., [Cr2Pt2Me4(pyphos)4] (2), [Cr2Pt2Cl4(pyphos)4] (3), and [Cr2Pt2Cl2Me2(pyphos)4] (4), have been prepared by the addition of the respective platinum species, PtIIMe2, PtIICl2, and PtIIMeCl, to the axial positions of the Cr2 moiety of 1. Magnetic measurements of 1-4 together with a crystallographic study for the complexes 1 and 2 revealed that the quadruply-bonded Cr-Cr distance was delicately altered by the nature of the Pt atoms, i.e., the kind of substituents (Cl and/or Me) on the Pt atoms.
Ionization of Pyrene in Nonpolar Hydrocarbon Solvents as Studied by Simultaneous Two-Photon Ionization Spectra
Authors: Ogawa Teiichiro , Murata Daisuke , Soga Hirofumi , Nakashima Keiji 
Published: September 2002

Abstract
Pyrene has two photoconductivity thresholds in the wavelength region of 360–435 nm (two-photon energy: 5.70–6.89 eV) in nonpolar hydrocarbon and tetramethylsilane. The first one is located at 6.04–6.44 eV and the second one at 5.18–6.11 eV. The former was assigned to direct ionization and the latter to an ion-pair formation process. Direct ionization is the major process.
Gas-Phase Studies of Group-11 Cation (Cu+, Ag+, and Au+) Reactions with 2-Propanol in a Supersonic Beam-Expansion Source
Authors: Huang Ya-Chien , Su Po-Hua , Yeh Chen-Sheng 
Published: September 2002

Abstract
The gas-phase reactions of group-11 ions (Cu+,Ag+, and Au+) with 2-propanol were investigated using laser vaporization combined with supersonic beam expansion in a time-of-flight mass spectrometer. A number of reaction pathways, including assoication, dehydrogenation, and dehydration, were observed. Among these metal ions, Au+ is highly reactive toward 2-propanol. The experimental results are parallel to studies by Wilkins et al. using an FT-ICR mass spectrometer (J. Am. Chem. Soc., 107, 7316 (1985)). The geometries and binding energies of all complexes M+–L, where M+ = Cu+, Ag+ , and Au+, L = 2-propanol, acetone, propene, and H2O, were estimated using Møller–Plesset perturbation (MP2) and density functional theory (BLYP). The bond strengths of the complex ions involving gold revealed the strongest bonding, due to a relativistic effect. The energetic relationship between the reactants and the products facilitated an interpretation of the observed exit channels. Because of the supersonic beam source employed, larger clusters containing metal ions were generated as well. Because the cluster sizes with solvent molecules were ≥ 2, the reactivities were apparently limited to Cu+ and Ag+ clusters, while the reactive nature changed in Au+ along with the formation of acetone, lacking in the bare Au+ reactions. For larger clusters, calculations on Ag+–(2-propanol)2 and Ag+–(2-propanol)(acetone) complexes using BLYP were performed to obtain their energetics.
Photodissociation of N2O4 Multilayer Adsorbed on a Polycrystalline Au Substrate
Authors: Senga Takehito , Yabushita Akihiro , Inoue Yoshihiko , Kawasaki Masahiro , Sato Shinri 
Published: September 2002

Abstract
The photodissociation dynamics of N2O4 multilayers adsorbed on a polycrystalline Au substrate at 80–140 K was investigated. The Au substrate was mainly composed of domains with (111) structure. Time-of-flight spectra of the photofragment NO and O as well as infrared reflection absorption spectra for the surface adsorbed species on the Au substrate were measured. Typically, four to five monolayers of N2O4 adsorb on the Au substrate at 85 K were irradiated by the pulsed output of an excimer laser at λ = 193 and 351 nm. Photodissociation of the adlayers at 193 nm takes place by direct photoabsorption of N2O4. Since the top layers of N2O4 absorbed the UV light, superthermal NO and O photofragments are produced. Translationally and internally relaxed fragments are also produced from the photodissociation of the inner layers. At 351 nm, the bulk photoexcitation results in formation of slow NO photofragments. By comparing the effect of dissociation wavelengths, substrate temperatures and dose rates, it is shown that the photodissociation dynamics is governed by both the photoexcitation process and the adsorption state of N2O4 on the Au substrate.
Conformation Preferences of 1,1′-Bis(1-amino-4,4-dicyclopropyl-2,3-diaza-1,3-butadienyl)
Authors: Lam Yulin , Ma Ngai Ling , Liang Eping 
Published: September 2002

Abstract
The reaction of dicyclopropyl ketone with hydrazine sulfate and sodium cyanide afforded 1,1′-bis(1-amino-4,4-dicyclopropyl-2,3-diaza-1,3-butadienyl). The compound exists in the trans conformation in the solid-state and has a trans population of 91.2% in solution. Experimental data are compared with values estimated by ab initio calculations.
Synthesis and X-Ray Structural Study of Magnesium (1,3-Propanediaminetetraacetato)nickelate(II) Octahydrate, Mg[Ni(1,3-pdta)]•H2O. Structural Parameters and Strain Analysis of [M(1,3-pdta)]n− Complexes in Relation to Their Octahedral Distortion
Authors: Radanovic Dusan J , Ama Tomoharu , Kawaguchi Hiroshi , Draskovic Nenad S , Ristanovic Divna M , Janicijevic Svetlana 
Published: September 2002

Abstract
The hexadentate complex Mg[Ni(1,3-pdta)]•H2O (1,3-pdta = 1,3-propanediaminetetraacetate ion) was prepared and its structure established by X-ray crystallography. The complex salt crystallizes in the space group Pnna (# 52) of the orthorhombic crystal system with a = 13.251(2), b = 11.645(2), c = 13.818(3) Å and Z = 4. The Ni(II) ion is surrounded octahedrally by two nitrogen and four oxygen atoms of the ligand. The Mg cation is bonded octahedrally to six water molecules. Both complex ions utilize a two-fold symmetry axis that is present in the crystal. The conformations of the chelate rings were found to be envelope or twist for the glycinates and skew-boat for the six-membered diamine ring. A comparison of structures of hexadentate [M(1,3-pdta)]n− complexes shows an expected variation in their octahedral distortion depending on the central metal ion M. Some spectral characteristics of the complex studied have also been reported.
Europium(III)-N,N′-Ethylenebis(l-amino acid) Complexes as New Chiral NMR Lanthanide Shift Reagents for Unprotected α-Amino Acids in Neutral Aqueous Solution
Authors: Takemura Makoto , Yamato Kazuhiro , Doe Matsumi , Watanabe Masaaki , Miyake Hiroyuki , Kikunaga Toshimitsu , Yanagihara Naohisa , Kojima Yoshitane 
Published: September 2002

Abstract
Three N,N′-ethylenebis(l-amino acid) ligands have been obtained simultaneously with three α,α′-(1,4-piperazinediyl)bis[(S)-alkanoic acid] and four N,N′-ethylenedipeptide products, by reacting a mixture of l-histidine methyl ester and l-aspartic acid dimethyl ester with glyoxal in the presence of sodium cyanotrihydroborate in methanol. Europium(III) complexes with N,N′-ethylenebis(l-amino acid) ligands were useful as chiral NMR shift reagents for some unprotected natural α-amino acids as substrates in neutral aqueous solution, as characterized by large enantiomeric shift differences and unbroadened signal shapes on high-resolution NMR spectroscopy. In addition, the acid-dissociation constants of six bis(amino acid) ligands and the stability constant of the europium(III) complex with N,N′-ethylenedi(l-histidine) were obtained by potentiometric titration.
Effect of Second-Sphere Coordination 9. Partial Inclusion of Pentaammineruthenium(II) and Pentacyanoferrate(II) Complexes with Nitrogen Heterocycles into a Cyclodextrin Cavity
Authors: Ando Isao , Ujimoto Kikujiro , Kurihara Hirondo 
Published: September 2002

Abstract
The inclusion of pentaammineruthenium(II) and pentacyanoferrate(II) complexes with nitrogen heterocycles into cyclodextrins was investigated by UV-visible spectrophotometry, 1H-NMR spectroscopy, and cyclic voltammetry. The stability constants of the inclusion adducts of the metal complexes into cyclodextrins were determined by capillary electrophoresis. The complexes form adducts with cyclodextrins by the inclusion of an aromatic ligand moiety of the complex into the cavity of cyclodextrins. The adduct formation caused a modification of the redox behavior of the complex. The stability of the cyclodextrin adduct was influenced by the included aromatic ligand of the complex and the cavity size of cyclodextrin, especially the positive charge on the aromatic ligand.
Identification of Individual Si-Rich Particles Derived from Kosa Aerosol by the Alkali Elemental Composition
Authors: Kyotani Tomohiro , Koshimizu Satoshi 
Published: September 2002

Abstract
A method of scanning electron microscopy-energy dispersive X-ray microanalysis (SEM-EDX) has been investigated for the identification of individual Si-rich particles derived from Kosa aerosol. The elemental composition of individual Si-rich particles (α-quartz) having SiO2 content over 80% was determined by SEM-EDX using a standardless φ(ρz) correction program, and the results were normalized to 100% on the basis of oxide composition. The distribution of (Na2O+K2O)/SiO2(%) in individual Si-rich particles from real airborne particulate matters showed a sharp and clear seasonal variation. It was found that the distribution was closer to those in the China loess and desert sand in spring time compared to those of the non-Kosa aerosol, the distribution could be successfully used as an effective indicator. The distribution of (MgO+CaO)/SiO2(%) was also used for discrimination from Si-rich particles in some Japanese volcanic rocks such as Andesites. Individual Si-rich particles derived from Kosa aerosol were clearly discriminated from those derived from the Japanese igneous rocks by the proposed method. These results suggest that the alkali elemental composition of individual Si-rich particles is a useful indicator to identify the Kosa particles and to investigate transportation of the Kosa aerosol.
Isolation and Structural Characterization of New Samarium(III) Bromide–HMPA Complexes
Authors: Asakura Katsuo , Imamoto Tsuneo 
Published: September 2002

Abstract
The crystal structures of new samarium(III) bromide–HMPA complexes were accurately determined by single crystal X-ray analysis. The Lewis acidity of samarium(III) cation is discussed based on the crystal structures of several samarium(III)–HMPA complexes.