bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intramolecular Change Distribution and Related Properties in a Series of 3,6-Di-tert-butylbenzoquinonatocobalt Complexes Containing Piperidine
Authors: Jung Ok-Sang , Lee Young-A , Park Sung Ho , Kim Yun Ju , Yoo Kyung Ho , Kim Dong Chan 
Published: September 2002

Abstract
A series of cobalt-benzoquinone complexes containing piperidine derivatives as a coligand, [Co(3,6-dbq)2(N-N)], (N-N = 1,1′-methylenedipiperidine (mdp), 1,1′-methylenebis(3-methylpiperidine) (mbmp), 1-methyl-4-(methylamino)piperidine (mmap); 3,6-dbq = 3,6-di-tert-butyl-1,2-benzoquinone) have been prepared and characterized. The crystal structure of [Co(3,6-dbq)2(mmap)]•0.5Me2CO (P1-, a = 11.524(2) Å, b = 12.565(4) Å, c = 14.160(3) Å, α = 80.65(2)°, β = 82.15(2)°, γ = 87.39(2)°, V = 2003.6(8) Å3, R = 0.0763) proves that the molecule exists as low-spin [CoIII(3,6-dbsq)(3,6-dbcat)(mmap)] (3,6-dbsq = 3,6-di-tert-butyl-1,2-semiquinonato; 3,6-dbcat = 3,6-di-tert-butylcatecholato) in the solid state. According to magnetic, spectroscopic, and thermal analyses, [CoIII(3,6-dbsq)(3,6-dbcat)(mmap)] is locked up to 431 K while [CoII(3,6-dbsq)2(mdp)] and [CoII(3,6-dbsq)2(mbmp)] are changed to their corresponding low spin CoIII forms at (below) T1/2 = 215 K and 271 K, respectively. The transition temperature (T1/2) between CoIII/CoII varies as mbmp &lt; mdp &lt;&lt; mmap, which appears to be associated with electronic versus steric effects of the piperidine coligands. In particular, [Co(3,6-dbq)2(mdp)] reveals a two-step spin conversion centered at 208 K and 298 K with a plateau of 90 deg.
Multielement Determination of Trace Elements in Seawater by Inductively Coupled Plasma Mass Spectrometry after Tandem Preconcentration with Cooperation of Chelating Resin Adsorption and Lanthanum Coprecipitation
Authors: Yabutani Tomoki , Chiba Koichi , Haraguchi Hiroki 
Published: September 2002

Abstract
A tandem preconcentration method, in which chelating resin adsorption and La coprecipitation were cooperatively employed for preconcentration, was developed as a pretreatment method for simultaneous multielement determination of trace elements in seawater by ICP-MS. First, the seawater sample (250 ml) was treated with a chelating resin for preconcentration of trace elements, and then trace elements with good recoveries were determined by ICP-MS. Trace elements with the chemical properties of oxoanion- and hydride-formation, which were poorly recovered in the chelating resin preconcentration, were further subjected to preconcentration by La coprecipitation. As a result, more than 30 elements could be determined in the concentration range from 9.6 μg L-1 for Mo to 0.00018 μg L-1 for Tm, when the present tandem method was applied to the analysis of open seawater standard reference material (NASS-4). Furthermore, the analytical results for open seawater reference materials were compared with those for coastal seawater reference material as well as for coastal seawater collected in the Ise Bay. It was found that the multielement data for trace elements in these seawater samples clearly showed different elemental distributions, reflecting the different marine environments.
Stabilities in Water and Transfer Activity Coefficients between Nonaqueous Solvents and Water of 1 : 1 Complexes of 15,15-Dimethyl-16-crown-5 with Metal Ions
Authors: Katsuta Shoichi , Motoyama Takako , Takeda Yasuyuki , Ouchi Mikio 
Published: September 2002

Abstract
The stability constants of 1 : 1 complexes of 15,15-dimethyl-16-crown-5 (DM16C5) with Li+, Na+, K+, Ag+, Tl+, Sr2+, Ba2+, and Pb2+ and of 16-crown-5 (16C5) with Li+ have been determined by conductometry in water at 25 °C. The transfer activity coefficients (sγ H2O) of the alkali metal ion complexes between nonaqueous solvents (s: acetonitrile, propylene carbonate, and methanol) and water have been calculated. These values have been compared with the literature values for 16C5 and 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (L16C5). In water, 16C5 and DM16C5 selectively complex Li+ over Na+ and K+. The complexing ability of DM16C5 for a given metal ion is generally lower than that of 16C5 and L16C5. The alkali metal ion complexes of all the crown ethers are much less stable in water than in s, and the selectivity and the substituent effects also depend upon the solvent. The sγ H2O values provide the following information: the alkali metal ion and the ether oxygen atoms are greatly dehydrated upon complexation in water; the dehydration is most drastic for Na+; the dehydration for Na+ is hindered by the methyl groups of DM16C5 and facilitated by the electron-donating side arm of L16C5. The solvent effects upon complexation are explained in terms of solute-solvent interactions.
Chemical Lithiation/Delithiation of K+-β-Ferrite (K1+xFe11O17)
Authors: Ito Shigeru , Omomo Yoshitomo , Fujii Takashi 
Published: September 2002

Abstract
The chemical lithiation⁄delithiation of K+-β-ferrite has been performed using butyllithium, lithium naphthalide (for lithiation), and iodine (for delithiation). In lithiation using butyllithium, the lithium content (y) in K1+xLiyFe11O17 was dependent on the average grain size of K+-β-ferrite single crystals; small grains (5 μm) largely reacted with lithium to form K0.99Li1.65Fe11O17. Lithiation was performed by the reduction of Fe3+ to Fe2+. Since the same X-ray diffraction (XRD) patterns were obtained before and after lithiation, the reaction seemed to be restricted to only near the grain surfaces. In lithiation using lithium naphthalide, the lithium content (y), which attained to be 36, was independent of the average grain size of K+-β-ferrite single crystals. This lithium content was remarkably large, compared to y = ca.1.6 in lithiation using butyllithium. A large amount of Fe0 (metal) was detected in the samples. According to scanning electron microscope (SEM) and XRD studies, not only pulverization of grains, but also destruction of the β-structure, occurred upon lithiation. On the other hand, delithiation of deeply lithiated samples was achieved by using iodine as an oxidant.
Synthesis and Structural Characterization of Thiolato-Bridged Tetranuclear Palladium(II) Complexes with N,N,S-Tridentate Ligands
Authors: Kawahashi Takako , Mikuriya Masahiro , Nukada Ryoji , Lim Jong-Wan 
Published: September 2002

Abstract
Palladium(II) complexes with 2-[(2-aminoethyl)amino]ethanethiol (HL1), 2-[(3-aminopropyl)amino]ethanethiol (HL2), 2-[(2-pyridylmethyl)amino]ethanethiol (HL3), and 2-{[2-(2-pyridyl)ethyl]amino}ethanethiol (HL4), [Pd4(L1)4]Cl4 (1), [Pd4(L2)4]Cl4 (2), [Pd4(L3)4](ClO4)3Cl (3), [Pd4(L4)4][Pd(SCN)4]Cl2 (4), and [Pd4(L4)4](ClO4)4 (5), were synthesized and characterized by measurements of the infrared, electronic, and NMR spectra. X-ray crystal structure analyses of 1, 2, 3, and 4 show that these complexes have a thiolato-bridged tetranuclear structure, where each palladium(II) center takes a square-planar N2S2 coordination environment.
Synthesis and Dimeric Structure of a Palladium(II) Complex with Bis(benzoylacetoneimine)-1,3-propan-2-ol
Authors: Mikuriya Masahiro , Minowa Kenichi , Lim Jong-Wan 
Published: September 2002

Abstract
A palladium(II) complex with 2-hydroxy-N,N′-bis(1-methyl-3-hydroxy-3-phenol-2-propene-1-ylidene)-1,3-propanediamine (H3L), [Pd(HL)]2, was synthesized and characterized by measurements of the magnetic moment and the electronic spectra. The X-ray crystal structure shows that the compound has a dimeric structure with two planar N2O2 coordination environments, which is formed by hydrogen-bonds between the alkoxy groups and the coordinating keto groups.
Fluorescent Monitoring of Complexation of Phthalimide-Fused Crown Ethers with Alkali Metal Ions
Authors: Otsuki Joe , Yamagata Toshihiro , Ohmuro Koji , Araki Koji , Takido Toshio , Seno Manabu 
Published: September 2002

Abstract
Phthalimide-fused mono(crown ether)s (1 and 2) and bis(crown ether)s (3 and 4) were prepared. These imide derivatives strongly fluoresce in methanol, and the fluorescence intensity is affected by alkali metal ions due to crown-ion interactions. While fluorescence increases upon complexation involving a single macrocycle, it decreases when the fluorophores take a face-to-face arrangement. This property was used to monitor the process of ion complexation and concomitant conformation changes. With the incremental addition of cesium ions (M) to the bis(crown ether)s (L), a folded sandwich complex (LM) initially formed, which subsequently transformed into a more extended LM2-type complex. This behavior, which was independently confirmed by 1H NMR spectroscopy, is clearly manifested in the fluorescence intensity.
Regioselectivity on Electroreductive Transannular Reaction of 7-Methylenebicyclo[3.3.1]nonan-3-one
Authors: Itoh Hiroki , Kato Ichiro , Unoura Kei , Senda Yasuhisa 
Published: September 2002

Abstract
A competitive transannular reaction occurred to give 7-methyltricyclo[3.3.1.03,7]nonan-3-ol (5) and 1-adamantanol (6) in the non-mediated electroreduction of 7-methylenebicyclo[3.3.1]nonan-3-one (1) in N,N-dimethylformamide. The apparent temperature dependence of the regioselectivity of the reaction may be attributed to the competitive operation of both kinetic and thermodynamic controls in the cyclization of the ketyl radical anion. The differences in the parameter of activation between the 5-exo- and 6-endocyclizations of 1•-, ΔΔH‡(5-exo - 6-endo) and ΔΔS‡(5-exo - 6-endo), were evaluated to be -3.1 kcal mol-1 and -11 cal mol-1 K-1, respectively. Semiempirical PM3 (RHF and UHF) calculations were also carried out to elucidate the reaction mechanism.
36-Membered Macrocyclic Diether Lipid is Advantageous for Archaea to Thrive under the Extreme Thermal Environments
Authors: Arakawa Kenji , Eguchi Tadashi , Kakinuma Katsumi 
Published: September 2002

Abstract
Described in this paper is the biophysical significance of the archaeal 36-membered macrocyclic diether phospholipid 36MPC as a function of temperature, which was studied by measuring of membrane fluidity, liposomal proton permeability, and liposomal thermostability in comparison with its acyclic counterpart, DPhyPC, their glycolipid derivatives, 36MGen and DPhyGen, egg yolk lecithin eggPC, and a mixed lipid of DMPC–cholesterol (2 : 1). Fluorescence anisotropy measurements indicated that the macrocyclic structure led to a decrease in the fluidity in the inter-membrane hydrophobic part more than in the membrane surface by limiting the motional freedom of the alkyl chains. The proton permeability was also significantly reduced by introducing a macrocyclic structure. Liposomal thermostability measurements using 6-carboxyfluorescein (CF) suggested that 36MPC formed liposomes with greater thermal stability than these of DPhyPC. The presence of glycolipids to the corresponding phospholipids greatly reduced the CF leakage from liposomes. Most importantly, DMPC-cholesterol liposome showed less leakage than 36MPC at 40 °C. However, by raising the temperature, this situation was completely reversed. This suggested that the cyclic structure contributed to the formation of stable liposomes, especially at higher temperatures. These findings clearly demonstrate that the 36-membered macrocyclic lipid membrane plays an important role for the thermophilic archaea to adapt to extreme environments.
Restricted Rotation Involving the Tetrahedral Carbon. LXIV. Barriers to Rotation of s-Alkyl Groups in 9-s-Alkyl-8,13-difluoro-1,4-dimethyl- and 1,2,3,4-tetrachloro-triptycenes
Authors: Oki Michinori , Nishino Masahiro , Kaieda Kazuihiro , Nakashima Takafumi , Toyota Shinji 
Published: September 2002

Abstract
9-(3-Acetoxy-1-methylpropyl)-8,13-difluoro-1,4-dimethyltriptycene and 9-(1-methyl-2-propenyl)-8,13-difluoro-1,4-dimethyl- and 1,2,3,4-tetrachloro-triptycenes were prepared. Their barriers to internal rotation around the C(9)–C(alkyl) bonds were measured by the classical kinetics. The barrier was affected a little by the substituent, being ca. 25–26 kcal mol-1. Rotamer distributions in these compounds and possible causes for these indifferent barriers to rotation are discussed.
Solvent Effects and Steric Course in the Solvolysis of 1,3,3-Trimethyl-2-oxocyclopentyl Mesylate in Comparison with 1,1,3,3-Tetramethyl-2-oxobutyl System
Authors: Takeuchi Ken’ichi , Ushino Takuhiro , Okazaki Takao , Kitagawa Toshikazu , Kinoshita Tomomi , Ohga Yasushi , Tanaka Koichi , Toda Fumio 
Published: September 2002

Abstract
The rates of solvolysis in various solvents were determined for 1,1,3,3-tetramethyl-2-oxobutyl tosylate (1OTs) and 1,3,3-trimethyl-2-oxocyclopentyl mesylate (4OMs). The rate data for 1OTs reinforced that the linear Grunwald-Winstein (GW) relationship of 1OMs previously reported by Creary for non-aqueous solvents must also hold for aqueous organic solvents. 4OMs showed a markedly dispersed GW relationship that is, on the other hand, well correlated with an extended GW equation involving a nucleophilicity parameter. Such solvent dependence, such marked effects of added sodium azide on rates, and the 100% inversion of configuration of the solvolysis product showed that the solvolysis of 4OMs would be categorized to SN2(intermediate), whereas 1OMs and 1OTs solvolyze via limiting SN1. The negligible susceptibility of 1OTs toward nucleophilicity of solvent and azide probe indicates that the nucleofuge leaves along the C=O axis in such a manner that the back-strain (B-strain) in the ground state is efficiently relieved in the transition state. Comparison of solvolysis rates of 1OMs and 4OMs with those of the corresponding parent substrates suggests that the transition states of these substrates would not be stabilized by carbonyl π conjugation. The origin of the unexpectedly fast rates of solvolysis of 1OMs has been discussed.
Synthesis of Trifluoromethyl Ketones by Palladium-Catalyzed Cross-Coupling Reaction of Phenyl Trifluoroacetate with Organoboron Compounds
Authors: Kakino Ryuki , Shimizu Isao , Yamamoto Akio 
Published: September 2002

Abstract
Cross-coupling reaction of aryl trifluoroacetates with organoboron compounds catalyzed by palladium complexes gives trifluoromethyl ketones in moderate to excellent yields under mild conditions. The catalytic process has been designed on the basis of fundamental studies dealing with oxidative addition of phenyl trifluoroacetate to a Pd(0) complex to give a (phenoxo)(trifluoroacetyl)palladium(II) complex and its subsequent reaction with phenylboronic acid to liberate phenyl trifluoromethyl ketone. The catalytic cycle is proposed to be composed of (a) oxidative addition of the ester to give acyl(aryloxo)palladium intermediate, (b) the subsequent transmetallation with arylboron compounds, and (c) reductive elimination. Palladium(0) complexes, as well as catalysts prepared in situ from palladium acetate and 3 molar amounts of tributylphosphine or phosphite at room temperature, serve as convenient and effective catalysts. The process is applicable to a wide range of phenyl- and naphthylboronic acids to give various aryl trifluoromethyl ketones under mild conditions. Aryl perfluoroalkyl ketone derivatives can be similarly prepared in high yields from various phenyl perfluoroalkanecarboxylates and arylboronic acids.
Regioselective Substitution of Phenols with Trifluoroacetaldehyde Ethyl Hemiacetal
Authors: Gong Yuefa , Kato Katsuya , Kimoto Hiroshi 
Published: September 2002

Abstract
Phenol did not react directly with trifluoroacetaldehyde ethyl hemiacetal. In the presence of catalytic amounts of anhydrous potassium carbonate, however, the reaction readily occurred. The p-substituted product 4-(2,2,2-trifluoro-1-hydroxyethyl)phenol predominated. In contrast, the reaction catalyzed by zinc halide predominantly produced the o-substituted product. Corresponding reactions of several phenols were studied under the same catalytic conditions.
2,2′-(1,3-Phenylene)bis(4-t-butyl-6-phenylphenylnitrene): An ESR Study of a Quintet Dinitrene Coupled with 1,3-Phenylene
Authors: Miura Yozo , Oka Hiroyuki , Teki Yoshio 
Published: September 2002

Abstract
4-t-Butyl-2,6-diphenylphenylnitrene and 2,2′-(1,3-phenylene)bis(4-t-butyl-6-phenylphenylnitrene) were generated by the phyolysis of the corresponding mono- and diazides and studied by ESR spectroscopy.
Fabrication of Solid-State Dye-Sensitized TiO2 Solar Cell Using Polymer Electrolyte
Authors: Matsumoto Masamitsu , Wada Yuji , Kitamura Takayuki , Shigaki Kouichiro , Inoue Teruhisa , Ikeda Masaaki , Yanagida Shozo 
Published: September 2002

Abstract
A solid-state dye-sensitized TiO2 solar cell has been fabricated with a polymer electrolyte constructed with α-methacryloyl-ω-methoxyocta(oxyethylene) or 2-(2-methoxyethoxy)ethyl acrylate as a base polymer, α-acryloyl-ω-acryloyloxyocta(oxyethylene)octa(ethylene glycol) dimethacrylate as a cross-linking agent and 3-methoxypropiononitrile as a plasticizer. The polymer is in-situ polymerized at the porous TiO2 film by photo-irradiation and the resulting film is immersed into the liquid electrolyte in order to introduce the electrolyte to the polymer phase. The conductivity of the polymer electrolyte reached 2.67 mS cm-1. The energy conversion efficiency of the solid-state cell was 2.62% under irradiation of simulated sunlight (AM 1.5, 1 kW m-2), achieving 86.4% of the cell efficiency using the liquid electrolyte.
The C60-Photosensitized Reduction of Methyl Viologen Through the Intermediary of O2
Authors: Konishi Toshifumi , Fujitsuka Mamoru , Ito Osamu , Toba Yasumasa , Usui Yoshiharu 
Published: September 2002

Abstract
C60-photosensitized reduction system of methyl viologen (1,1′-dimethyl-4,4′-bipyridinium) electron-mediated by O2 in organic solvents was demonstrated. By steady-state photoirradiation of C60 in the presence of electron donors such as triethanolamine (2,2′,2′′-nitrilotriethanol) and tetraphenylborate (-BPh4), the absorption-band of C60•- increased with irradiation time, and persisted for a long time. On introduction of O2, followed by the irradiation, C60•- disappeared and superoxide anion (O2•-) was generated. The photochemical reaction mechanisms were investigated by the transient-absorption method. The rate constant for electron transfer from C60•- to O2 was estimated to be (3.7 ± 0.2) × 102 mol-1 dm3 s-1. On addition of MV2+, electron transfer from O2•- to MV2+ was observed in aprotic solvents such as benzonitrile, yielding blue methyl viologen cation radical (MV•+). By irradiation of the system of C60/electron donor/O2/MV2+, MV•+ was also generated. In these systems, MV•+ accumulated and remained even in air-saturated solution for more than 1 h, because electron transfer from O2•- to MV2+ is an exothermic process in aprotic solvents.
Laser Flash Photolysis in High Speed Photopolymer Coating Layers III: Sensitization Mechanisms of Aminochalcone-Type Dyes with a Radical-Generating Reagent
Authors: Itoh Hiroki , Ishikawa Masayo , Takada Akiomi , Kudo Hideaki , Senda Yasuhisa , Urano Toshiyuki 
Published: September 2002

Abstract
In order to get insight into the effect of the different fixations of the conjugated systems of the aminochalcone-dyes on both the photophysical behavior and the quenching scheme of photoinitiation systems in a film, photophysical behavior of 2-benzoyl-6-(dimethylamino)benzo[b]furan (A) on 355 nm excitation with or without a radical-generating reagent, 2,4,6-tris(trichloromethyl)-1,3,5-triazine (TRI), in poly(methyl methacrylate) (PMMA) film has been investigated by laser flash photolysis using a total reflection cell. Dye A showed characteristic dual fluorescences of which the lifetimes, τSs, of shorter- and longer-wavelength components were evaluated to be 3.2 and 5.4 ns, respectively. The fluorescences were quenched by TRI with different static quenching distances, (Rs)Ss, of 1.3 and 1.5 nm for Ashort and Along, respectively. The static quenching distance of the initial triplet absorption of A, (Rs)T, was evaluated to be 1.5 nm. In addition, deconvolution analysis of the lifetimes of fluorescent dyes has been carried out to clarify the property of nonstatic quenching of the dyes: A, 10-benzoyl-2,3,6,7-tetrahydro-1H,5H-furo[3,2-g]pyrido[3,2,1-i,j]quinoline (B), 4′-(dimethylamino)chalcone (C), and (E)-3-(9-julolidinyl)-1-phenyl-2-propen-1-one (D), with TRI in the film.
Cyclic π-Conjugated Systems Annelated with Bicyclo[2.2.2]octene: Synthesis, Structures, and Properties
Authors: Komatsu Koichi 
Published: September 2002

Abstract
This article presents an account of studies on the synthesis and properties of the cyclic π-conjugated systems annelated with bicyclic σ-frameworks. Particular emphasis is placed on π-systems carrying a positive charge, which are remarkably stabilized by complete annelation with bicyclo[2.2.2]octene. In such systems, not only the kinetic effects but also electronic effects due to σ-π conjugation strongly affect the properties of the π-systems. The thermodynamic properties, redox behavior, and the X-ray crystal structures are discussed. The cyclic π-systems studied include hydrocarbon molecules such as benzene and a series of benzenoid condensed aromatics, seven-membered ring non-benzenoid aromatic cation, i.e. tropylium ion, cyclooctatetraene, a spiro-connected cyclopentadiene, and dehydroannulenes. The study is further extended to systems containing heteroatoms such as 1,4-dithiin, metallacycloheptatrienes, and silatropylium ion.
Control of Molecular Orientation of α-Helix in the Monolayer at Air–Water Interface
Authors: Doi Tomokiyo , Kinoshita Takatoshi , Tsujita Yoshiharu , Yoshimizu Hiroaki 
Published: September 2002

Abstract
Amphiphilic block copolymers of poly(L-leucine-co-ethylene glycol) (PLeum-PEGn) having three different compositions, m : n = 80 : 23, 57 : 46, and 66 : 114, were prepared and spread at an air-water interface to form a stable monolayer. The α-helical conformation of PLeu segment in the monolayers was confirmed by FT-IR and circular dichroism measurements. The molecular orientation of PLeu helix rods in the monolayer was estimated by surface pressure-area isotherm and FT-IR reflection absorption spectroscopy measurements. As a result, we confirmed that α-helix rod of PLeu segment oriented slightly normal to the membrane plane. Furthermore, it was indicated that each α-helical rod in the PLeu57–PEG46 monolayer is effectively oriented normal to the interface compared to that in the PLeu80–PEG23 and PLeu66–PEG114 monolayers.
Ground and Excited Singlet (S1) State Interactions of 2,2′- and 4,4′-Biphenyldiols with Proton Acceptors
Authors: Mohanty Jyotirmayee , Pal Haridas , Sapre Avinash V 
Published: September 2002

Abstract
Proton-transfer interactions of 2,2′- and 4,4′-biphenyldiols with urea (U), N-methylurea (MU), and triethylamine (TEA) have been investigated in methanol solutions using optical absorption as well as steady-state and time-resolved fluorescence measurements. In the ground state, both 2,2′- and 4,4′-biphenyldiols do not interact with weak proton acceptors, like U and MU. In the excited singlet (S1) state, only the 2,2′-biphenyldiol is seen to transfer a proton to U and MU, via the formation of intermolecular hydrogen-bonded exciplexes as intermediates. With TEA, a strong proton acceptor, both 2,2′- and 4,4′-biphenyldiols undergo an efficient proton-transfer reaction in their S1 state. In the ground-state, however, only 2,2′-analogue is seen to transfer a proton to TEA. The differences in the proton-transfer behavior of 2,2′- and 4,4′-biphenyldiols with different proton acceptors have been rationalized in terms of the presence and absence of intramolecular hydrogen bonding in the two diols.