bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton ENDOR Studies on Zinc-Doped Copper(II) Acetate Monohydrate Single Crystal
Authors: Kita Shouich , Uchida Kengo , Miyamoto Ryo , Iwaizumi Masamoto 
Published: July 2006

Abstract
The proton ENDOR spectra of the zinc-doped copper(II) acetate monohydrate single crystal were measured at 20 K. Hyperfine coupling tensors have been determined for the two protons of the water molecule at the axial position of the paramagnetic copper ion and a proton of the water forming the hydrogen bond with carboxylate oxygen at the equatorial plane of the copper ion. The axial water protons have small positive isotropic hyperfine couplings owing to the pseudo-contact interaction, and the equatorial water proton has a small negative one due to the spin polarization effect of the positive spin on the acetate oxygen through the hydrogen bond. The anisotropic hyperfine tensors of the former protons are interpreted by the dipolar interaction with the unpaired spin on the copper dx2−y2 orbital. The anisotropic interaction of the latter protons indicates that the spin delocalizes onto the oxygen atoms of the acetate bridges. Based on these observed hyperfine interactions, the mechanism of the spin–spin interaction in the dimer complex is discussed.
Intersystem Crossing of Radical Pair in Solvent Cage. External Heavy Atom Effect on Dual Photoreactions of Phthalazine
Authors: Inoue Hiroyasu , Sakurai Tadamitsu , Hoshi Toshihiko , Okubo Jun , Ono Isao 
Published: July 2006

Abstract
The effects of the temperature, initial concentration, and chemical quenchers on dual photoreactions of phthalazine were investigated. The results give further supporting evidence for a previously proposed reaction mechanism, i.e., phthalazine in the lowest excited singlet and triplet states affords singlet and triplet radical pairs, respectively, in the initial hydrogen abstraction process from 2-propanol. The singlet radical pair gives a reduction product in a solvent cage, whereas the radicals produced in the triplet state escape from the solvent cage, causing dimerization. On the basis of the reaction mechanism of dual photoreactions, external heavy-atom effects on the radical pairs within a solvent cage have been studied. The results indicate that heavy-atom perturbations bring about an enhancement of the intersystem crossing efficiency from the triplet-state radical pair to the singlet one, including a spin inversion of the radical pair in the solvent cage, rather than S1→T1 intersystem crossing induced within a single molecule of phthalazine.
Four- and Five-Coordinated Nickel(II) Isocyanide Complexes and Donor–Acceptor Complexes Containing Nickel and Mercury
Authors: Yamamoto Yasuhiro , Ehara Kazuko , Takahashi Katsuo , Yamazaki Hiroshi 
Published: July 2006

Abstract
Reaction of NiI2(RNC)2 (1) (a: R=2,6-Me2C6H3; b; 4-Br-2,6-Me2C6H2; c: 2,4-t-Bu2-6-MeC6H2: d: 2,4,6-t-Bu3C6H2 with RNC or PPh3 gave NiI2(RNC)3 (2) or NiI2(PPh3) (RNC)2 (3) (a: R=2,6-Me2C6H3; b: 2,6-Me2-4-BrC6H2). An X-ray analysis of (3a) showed that the complex has a trigonal bipyramidal structure; crystal data: Space group Pna21; a=21.577(2), b=9.440(1), c=17.075(1) Å, α=β=γ=90.0°, V=3477.7(6) Å3, R=0.0444. The bromide and chloride complexes, NiX2(2,6-Me2C6H3NC)2 (1e: X=Cl; 1f: X=Br) did not produce five-coordinated species. When complexes (1a, 1b, 1e, or 1f) were treated with Hg in the presence of isocyanide, the donor–acceptor complexes [Ni(RNC)4HgX2]2 (X=I, Br, or Cl) (4) were formed. An X-ray analysis of (4b) (R=4-Br-2,6-Me2C6H2) was undertaken; crystal data: Space group: Pl (triclinic); a=12.709(3), b=16.145(3), c=12.614(3) Å, α=96.11(2), β=107.67(2), γ=73.11(2)°, V=2359.5(10) Å3, R=0.0686. The complex is a donor-acceptor complex containing the Ni–Hg bond and has a dimeric structure bridged by two I atoms. The configuration around Ni is the trigonal bipyramid and around Hg, distorted tetrahedron.
Effect of Alkylammonium Ions on the Photochemical Behaviors of γ-Stilbazolium Aggregates in Clay Interlayers
Authors: Usami Hisanao , Takagi Katsuhiko , Sawaki Yasuhiko 
Published: July 2006

Abstract
Effect of alkylammonium ions (Cn+) has been studied on the clusterization and photochemical behaviors of γ-stilbazolium (4-(2-phenylvinyl)pyridinium) ion (1) adsorbed on clay interlayers. The aggregates of 1 were shown to be dissociated by the coadsorption of Cn+ with molecular length longer than that of 1. The major photoreaction was changed from cyclodimerization to E–Z isomerization on coadsorbing Cn+’s longer than 1. The efficient excimer emission from intercalated 1 was dramatically reduced by coadsorbing alkylammonium ions. The resulting concentration dependence of excimer emission intensity is nicely simulated by a Monte Carlo method for two-dimensional lattice site models.
Ion Pairing of Radical Ions of Aromatic Alkenes and Alkynes Studied by Pulse Radiolysis
Authors: Yamamoto Satoshi , Yamamoto Yukio , Hayashi Koichiro 
Published: July 2006

Abstract
Pulse radiolysis of 1,2-dichloroethane solutions of trans,trans-1,4-bis(2-phenylethenyl)benzene and 1,4-bis(2-phenylethynyl)benzene was undertaken in the presence of Bu4NPF6 (Bu=butyl) to investigate the effect of ion pairing of the solute radical cations with PF6−. It was also undertaken for the tetrahydrofuran solutions of the above compounds in the presence of Bu4NPF6 and NaBPh4, where the solute radical anions are generated and form ion pairs with Bu4N+ and Na+. The decay of the radical ions, which is due to neutralization, is retarded by the ion pairing. The rate constants for the neutralization reactions in the free-ion and ion-paired states were determined. Also presented are the data for the radical ions of trans-stilbene, diphenylacetylene, trans,trans-1,4-diphenyl-1,3-butadiene, and diphenylbutadiyne. The radical ions of the aromatic alkynes are less stabilized by the ion pairing than those of the aromatic alkenes having the same carbon skeletons probably because of more extensive charge delocalization of the former radical ions. Spectral shifts to shorter wavelengths caused by the ion pairing are appreciable for the radical anions. Dependence of the spectral shifts on the size of the radical anions is described.
Preparation and Properties of Oxo-Centered Trinuclear Chromium(III) Complexes with Bridging Optically Active Amino Acids, [Cr3(μ3-O)(μ-O,O′-amino-acid)6(H2O)3]7+
Authors: Kato Hisashi , Nakata Kou , Nagasawa Akira , Yamaguchi Tadashi , Sasaki Yoichi , Ito Tasuku 
Published: July 2006

Abstract
Trinuclear chromium(III) complexes with optically active amino acids as bridging groups, [Cr3(μ3-O)(μ-RCH(NH3)COO)6(H2O)3]X7 (R=CH3, (CH3)2CH, (CH3)2CHCH2, C6H5CH2; X=Cl−, NO3−), were prepared, and the X-ray structure of the l-valine complex was determined. Their electronic spectra and magnetic moments are similar to those of analogous carboxylate-bridged trichromium(III) complexes.
Alumina-Catalyzed Addition of Thiols to Methyl Propiolate
Authors: Kodomari Mitsuo , Saitoh Goroh , Yoshitomi Suehiko 
Published: July 2006

Abstract
The addition of thiols to methyl propiolate was remarkably accelerated in the presence of alumina to give the Z-isomer of the 1:1 adducts stereoselectively, in which alumina acts as a bifunctional catalyst of acid and base.
Solvent Effect on the ESR Parameters of Di-t-butyl Nitroxide and Galvinoxyl. Theoretical Application of the MNDO Effective Charge Model
Authors: Takase Hideto , Morihashi Kenji , Kikuchi Osamu 
Published: July 2006

Abstract
An effective charge model of the solvent effect was incorporated with the RHF-MNDO-CI method for free radicals, allowing the solvent effect on the hyperfine coupling constants (hfcc) and g-values of the di-t-butyl nitroxide (DTBN) and galvionxyl radicals to be examined. The calculated solvent dependences of the spin distribution and the n→π* excitation energy of DTBN have well elucidated the observed solvent effect on the hfcc and g-value of DTBN. The observed trend for the proton hfcc of galvinoxyl has been correctly reproduced by the present theoretical model.
Synthesis and Properties of Peroxy Esters Having a Benzophenone Chromophore
Authors: Kumura Hiromi , Nakamura Tomoyuki , Higuchi Yoshiki , Suyama Shuji 
Published: July 2006

Abstract
Diperoxy esters having a benzophenone chromophore have been successfully synthesized from the reaction of 3-chloro-3-phenylphthalide (1) with 2,5-dihydroperoxy-2,5-dimethyl-3-hexyne (4a) or 2,5-dihydroperoxy-2,5-dimethylhexane (4b). The corresponding diperoxy esters had a UV absorption above 300 nm. The free radicals produced during the photolysis of these compounds initiated the radical polymerization of methyl methacrylate at room temperature under UV light.
Studies on the Secondary Structure of Bradykinin in Aqueous Solution. Syntheses, Circular Dichroism Spectra, and Biological Activities of Bradykinin Amide and [d-Ala4]-Bradykinin
Authors: Hashimoto Chikao , Nozaki Sukekatsu , Muramatsu Ichiro 
Published: July 2006

Abstract
Bradykinin amide and [d-Ala4]-bradykinin were synthesized by the ‘hold-in-solution’ method. The circular dichroism spectra of both peptides were measured and compared with that of bradykinin. These analogs exhibited weak activity (0.01% of bradykinin) in the increment of blood flow in a femoral artery of dog.
Synthesis, Chemical Properties, and Structure of a Sterically Hindered Ketone, 2,2,5,5-Tetramethyl-4,4-diphenyl-3-thiolanone
Authors: Nakayama Juzo , Hirashima Atsushi , Yokomori Yoshinobu 
Published: July 2006

Abstract
A sterically hindered ketone, 2,2,5,5-tetramethyl-4,4-diphenyl-3-thiolanone (1), was synthesized in two steps starting from 2,2,4,4-tetramethyl-1,5-diphenyl-3-thiapentane-1,5-dione. The carbonyl group of 1 is unreactive toward a series of nucleophiles which are bulkier than hydride or its equivalents. The observed unreactivity is ascribed to the steric hindrance enhanced by the two methyl groups on C-5 (“buttressing” effect). The result of an X-ray single crystal structure analysis of 1 is also described.
Molecular Motions of t-Butylammonium Ions and Structural Phase Transitions in Solid t-Butylammonium Perchlorate Studied by 1H NMR and Thermal Measurements
Authors: Ishida Hiroyuki , Iwachido Tadashi , Hayama Naomi , Nakamura Daiyu , Ikeda Ryuichi 
Published: July 2006

Abstract
Differential thermal analysis (DTA), differential scanning calorimetry (DSC), and the temperature dependences of the 1H spin-lattice relaxation time (T1) and the second moment (M2) of 1H NMR absorptions were studied in (CH3)3CNH3ClO4 and its partially deuterated analogs, (CH3)3CND3ClO4 and (CD3)3CNH3ClO4. DTA and DSC studied revealed four solid phases, including a metastable phase, in the temperature range between 80 K and the melting point (414 K). The stable phases (named as I, II, and III) were obtained above 394 K, between 394 and 327 K, and below 327 K, respectively. The metastable phase II′, prepared by rapid cooling the phase II to ca. 100 K, exists below ca. 245 K. The cationic motions in each solid phase were studied by T1 and M2 experiments. Three kinds of motions (reorientations of the CH3 groups about their C–C bond axes, the NH3+ group about its C–N bond axis, and the t-butyl group about the C–N bond axis) were observed in these phases and their motional parameters were determined
Fluorometric Determination of Amino Acids and Proteins Utilizing a Copper(II) Catalyzed Reaction
Authors: Mori Hisakazu , Sakai Kazue , Yamashina Kyoko , Hirata Sayuri , Horie Kumiko 
Published: July 2006

Abstract
Amino acids accelerated the copper(II)-catalyzed oxidation of di-2-pyridyl ketone hydrazone (DPKH) to form a fluorescent compound. With the use of this enhancement effect of catalysis, various amino acids (l-histidine, l-cysteine, l-glutamic acid, glycine, Dl-serine, and l-arginine) could be determined by flow injection analysis. The detection limit of L-histidine was less than 2 pmol. On the contrary, proteins decreased the catalysis. Proteins were also determined through the utilization of this effect. In this determination, the addition of citric acid was found to be very effective. The detection limit of bovine serum albumin was less than 20 ng. The effect of protein upon the catalysis of copper(II) was considered to be ascribable to an inhibition of the coordination of DPKH to copper(II).
Ligand-Mediated Pseudohypersensitivity of Some 4f–4f Transitions in Neodymium(III) Interaction with Fluorinated Nucleic Acid Components
Authors: Misra Sudhindra N , Mehta Surendra B 
Published: July 2006

Abstract
Absorption difference and comparative absorption spectrophotometry of the systems containing Nd(III) and fluorinated nucleic bases (fluoroadenine, fluorocytosine, fluorothymine, and fluorouracil) and fluorinated nucleosides (fluoroadenosine, fluorocytidine, fluorothymidine, and fluorouridine) in ethyl acetate–water (90:10), have shown that certain 4f–4f transitions (4I9⁄2→4G7⁄2, 4F7⁄2, 4F5⁄2, and 4F3⁄2), which are generally considered to be insensitive, have been found to exhibit substantial sensitivity towards even minor changes in the coordination environment around neodymium(III). The observation has been referred to as “Ligand-Mediated Pseudohypersensitivity.” The magnitude of various spectral parameters (energy interaction, Slater-Condon interelectronic repulsion Fk, spin–orbit interaction ξ4f, nephelauxetic \barβ, b, δ, and Judd–Ofelt Tλ intensity and oscillator strength (P)), computed using regression analysis, has been used in exploring the degree of inner and outer sphere coordination, incidence of covalency and extent of involvement of metal 4f orbitals in bonding. The isolation of solid complexes and their characterization by elemental analysis, infrared spectral, and Karl Fischer titration suggested octa and nona coordinated environment around neodymium and some probable structures for these complexes have been proposed.
Photoinduced Nucleophilic Addition of Ammonia and Alkylamines to Aryl-Substituted Alkenes in the Presence of p-Dicyanobenzene
Authors: Yamashita Toshiaki , Shiomori Koichiro , Yasuda Masahide , Shima Kensuke 
Published: July 2006

Abstract
The photoamination of 1,1-diphenylpropene (1a) with ammonia and some primary alkylamines in the presence of p-dicyanobenzene gave the corresponding N-substituted 2-amino-1,1-diphenylpropane (2a–e) along with the formation of 3-methyl-4,4-diphenylbutanenitrile (3a), 1,1-diphenylpropane (4a), 3,3-diphenylpropene (5), and diphenylmethane (6). In the case of 1,1-diphenylethene (1b), N-substituted 1-amino-2,2-diphenylethane (2f–h), 4,4-diphenylbutanenitrile (3b), and 1,1-diphenylethane (4b) were produced. In photoamination with t-butylamine in acetonitrile, 3a and 3b were mainly formed as a consequence of the incorporation of acetonitrile to 1a and 1b. The photoamination of 1-phenyl-3,4-dihydronaphthalene (1c) with isopropylamine or t-butylamine gave cis- and trans-N-substituted 1-phenyl-2-amino-1,2,3,4-tetrahydronaphthalenes (15 and 16) in a ratio of ca. 8:2. The mechanism of photoamination is discussed in terms of a photochemical electron transfer of 1 to p-dicyanobenzene followed by a nucleophilic addition of the amine to the cation radical of 1.
On the Splittings of J-Aggregate Band in Pseudoisocyanine
Authors: Ito Hirotoshi , Agatsuma Masaru , I’Haya Y J 
Published: July 2006

Abstract
The observation of J-band splittings in the Fano–DeVoe type calculations of pseudoisocyanine aggregates is reported. Based upon the monoclinic structure of pseudoisocyanine iodide crystal, we build four models which respectively assume the lattice constants of the crystal structure. The one-dimensional (1D-) single polymer model is selected along a particular direction from the crystal structure. As we diminish the lattice constants uniformly, the 1D-single-polymer model comes to reproduce single J-bands, while two kinds of 2D-two-inter-polymer interaction models resolve the single J-bands into doublet through multiplet structures for the corresponding parameters. The 3D-four-inter-polymer interaction model brings about doubly split J-bands, but the shortening of the parameters resolves the doublet J-bands into quartet through multiplet structures. However, a single J-band is obtained by the assumption of an orthorhombic 3D-four-inter-polymer model which has the same parameters as those of the monoclinic iodide crystal except for the angle. The shapes calculated are found to be extremely sensitive to the geometrical values as well as the monomer spectroscopic parameters. The cause of the J-band splittings is ascribable to the excitonic interactions between at least two column polymers.
The Energy Aspect of Oil/Water Partition and Its Application to the Analysis of Quantitative Structure-Activity Relationships. Aliphatic Alcohols in the Liposome/Water Partition System
Authors: Fujiwara Hideaki , Da Yong-Zhong , Ito Katsuhiko , Takagi Tatsuya , Nishioka Yukako 
Published: July 2006

Abstract
The energy aspect of oil/water partition has been examined for several solutes in different partition systems by determining the thermodynamic parameters of the partition. The thermodynamic parameters changed systematically, depending on the polarity of the nonaqueous phase of the partition. To further investigate the partition system dependency of the QSAR (quantitative structure–activity relationships) treatments the thermodynamic properties have been determined for various aliphatic alcohols in a liposome/water system; the results are discussed with regard to the previous ones obtained in a 1-octanol/water system, while paying special attention to applicability in the QSAR analysis. The following trends were observed in common with the two partition systems of liposome/water and 1-octanol/water: 1. The enthalpy term (ΔHp°) can well reproduce the toxicity data for halogenated and nonhalogenated alcohols collectively, whereas the conventional logP (partition coefficient) term can be applied only for the two types of alcohols separately; 2. The entropy term (ΔSp°) adds a discernible contribution to the refinement of the regression analysis. A distinctive characteristic is also discussed from a statistical method of analysis for the thermodynamic properties obtained in the two partition systems.
Novel Transformation of Formyl Groups into Hydroxyl Groups Utilizing Deformylative Autoxidation of Aldehydes
Authors: Kigoshi Hideo , Imamura Yoshifumi , Sawada Akihiko , Niwa Haruki , Yamada Kiyoyuki 
Published: July 2006

Abstract
Structural requirements that cause deformylative autoxidation of aliphatic aldehydes are investigated. Decarbonylation of acyl radicals proceeds smoothly when the alkyl radicals that are formed can be stabilized by allylic conjugation. Further conjugation of the double bond in the allyl radical with a carbonyl or a cyclopropyl group allows position-selective peroxidation of the alkyl radical.
Fixation of Carbon Dioxide with Diphenylcarbodiimide as a Model of Biotin Enzyme Active Site and a Weak Base: The Carboxylation of Fluorene under Mild Conditions
Authors: Chiba Koji , Tagaya Hideyuki , Karasu Masa , Ono Tsuyoyuki , Saito Masaru , Ashikagaya Atsushi 
Published: July 2006

Abstract
Carbon dioxide was directly fixed into fluorene in the presence of diphenylcarbodiimide (DPC) as a model of a biotin enzyme active site and potassium hydrogencarbonate. It was considered that not only carbon dioxide but also the hydrogencarbonate ion were the carbon source in the presence of DPC. Weak bases such as potassium acetate, potassium propionate, and potassium formate were also effective for carboxylation.
Synthesis of Substituted Pyridines by a Cycloaddition Route Using Nitrile Oxides and Homoallyl Alcohols
Authors: Kanemasa Shuji , Asai Yoshihiko , Tanaka Junji 
Published: July 2006

Abstract
Cycloadditions of nitrile oxides with unprotected homoallyl alcohols, followed by Swern oxidations, lead to 5-(2-oxoalkyl)-2-isoxazolines. Subsequent Raney Ni reduction of the resulting heterocycles in ethanol in the presence of excess tetrafluoroboric acid affords substituted pyridine derivatives.
Association Characteristics of Amphiphilic α-Helices Connected by Flexible Links
Authors: Morii Hisayuki , Honda Shinya , Ichimura Kunihiro , Uedaira Hatsuho 
Published: July 2006

Abstract
Amphiphilic helical peptides interlinked with sequences bearing a flexible mobility were designed and synthesized. The sequences containing glycine and/or cystine were adopted for the linkage parts. The secondary structure of the peptides was investigated by circular dichroism(CD) and the super-secondary structure was estimated. The CD spectra and their pH dependence show that the peptides have almost the same α-helix contents as designed and that the helices associate to be “coiled-coil” at neutral pH. The apparent helix contents increase at low pH and some of helices are subject to denaturation at high pH. The denaturation of α-helix bundles by guanidine hydrochloride is contemplated to be three-state transition. It is proposed that the peptides construct α-helix bundles with both loose and tight contacts between helices. Two kinds of folded structure constructed with 2 or more helices are also suggested.
Metal Complexes of Peptides. V. Cobalt(III) Complexes with N-β-Alanyl-(S)-aspartate
Authors: Ama Tomoharu , Maki Ritsuko , Kawaguchi Hiroshi , Yasui Takaji 
Published: July 2006

Abstract
Three cobalt(III) complexes containing N-β-alanyl-(S)-aspartic acid (H3L), [Co(L)(en)] (en: ethylenediamine), [Co(L)(dien)] (dien: diethylenetriamine), and [Co(HL)(dien)]+, were newly prepared and characterized on the basis of their 13CNMR, UV-visible absorption, and circular dichroism spectra. The dipeptide L functions as a quadridentate ligand in [Co(L)(en)] and as terdentate ligands in [Co(L)(dien)] and [Co(HL)(dien)]+. The structures of these complexes are discussed in connection with those of [Co((S)-asp)(dien)]+(H2(S)-asp: (S)-aspartic acid) and [Co(edma)(dien)]2+ (Hedma: ethylenediamine-N-acetic acid).
Association of Symmetrical p-Dihalobenzenes with Cyclodextrins in Aqueous Medium
Authors: Takuma Tatsuyoshi , Deguchi Toshio , Sanemasa Isao 
Published: July 2006

Abstract
The complex formation of cyclodextrin (CyD, host) with symmetrical p-difluoro-, dichloro-, dibromo-, and diiodobenzenes (guests) has been studied in aqueous medium at 25°C by making use of the volatilization rate of guest molecules from the aqueous into gaseous phase. In the excess of the host, α- and β-CyDs form 1 : 1 and 2 : 1 (host : guest) complexes, while γ-CyD forms 1 : 1 complexes. The association constants, especially for α-and β-CyDs, increased with an increase in the size of the halogen atom. A linear relationship between the logarithm of the 1 : 1 association constant and the total surface area of guest molecule was found for CyD–monohalobenzenes and CyD–p-dihalobenzenes. The van der Waals force seems to be the main factor in stabilizing the associated complexes. The validity of the concept of microscopic binding constant is discussed.
Studies on Ferrocene Derivatives. VII. Solvent Effect on the Oxidation Reaction of t-Butylferrocenes
Authors: Hayashi Takatoshi , Okada Yutaka , Yamashita Tetsurou 
Published: July 2006

Abstract
The oxidation reactivity of t-butylferrocenes with air was measured in 1,2-dichloroethane or 1,4-dioxane. Their reactivity in 1,2-dichloroethane was increased with increasing the number of the substituents. It was considered that the oxidation proceeds through air oxidation with catalytic proton. On the other hand, in 1,4-dioxane, the conversion amount to oxidized form of ferrocene or t-butylferrocene suddenly incresed in the course of the reaction. In this solvent, the ferrocene nucleus was decomposed to give Fe3+ ion. It seems that the substrate was oxidized by Fe3+ ion formed.