bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Dynamic Stereochemistry of a Tri(1-azulenyl)methyl Cation Containing a Different Substituent on Each Azulene Ring
Authors: Ito Shunji , Morita Noboru , Asao Toyonobu 
Published: July 2006

Abstract
The first example of a tri(1-azulenyl)methyl cation (2) containing a different substituent on each azulene ring was synthesized, and the dynamic stereochemistry was studied by temperature-dependent 1H NMR spectra. The dynamic behavior of 2 supported a one-ring flip mechanism and the validity of the flip mechanism for the analysis of the conformational change of the tri(1-azulenyl)methyl cations.
A Novel Enzymatic Decarboxylation Proceeds via a Thiol Ester Intermediate
Authors: Kawasaki Takayasu , Watanabe Masakatsu , Ohta Hiromichi 
Published: July 2006

Abstract
It is proposed that arylmalonate decarboxylase (AMDase)-catalyzed decarboxylation proceeds via a thiol ester intermediate. Kinetics and CD spectra indicated that α-bromophenylacetate is a competitive inhibitor. TOF mass data indicated that the inhibitor bound with the enzyme through a thiol ester bond which was formed between a cysteine residue of the enzyme and the carboxyl group of the inhibitor. This result was also supported by reactivation of the enzyme by the addition of 2-mercaptoethanol, which is expected to cleave the enzyme–inhibitor bond via nucleophilic attack on the thiol ester linkage.
Effect of a Liquid–Liquid Phase Separation on the Slopes of Density vs. Concentration Plots
Authors: Inamura Isamu , Jinbo Yuji , Akiyama Yoriko , Kubo Yasuo 
Published: July 2006

Abstract
The densities were measured for dextran (Dex)–polyethylene glycol (PEG)–water, poly(1-vinyl-2-pyrrolidone (PVP)–PEG–water, and poly(vinyl alcohol) (PVA)–PEG–water systems. In all cases, the linear relationship of the density vs. concentration plots was not affected by the occurrence of liquid–liquid phase separation. The partial specific volumes were calculated from the slopes of the straight lines of the density.
Direct C≡C Triple Bond Formation from the C=C Double Bond and Direct Hydroxylation into the o-Position of a Nitro Group on the Benzene Nucleus with Potassium t-Butoxide in N,N-Dimethylformamide in the Air
Authors: Akiyama Shuzo , Tajima Kunihiko , Nakatsuji Shin’ichi , Nakashima Kenichiro , Abiru Kazuko , Watanabe Miwa 
Published: July 2006

Abstract
A novel and facile method for direct C≡C acetylenic bond formation from the C=C double bond by treatment with potassium t-butoxide (t-BuOK) in N,N-dimethylformamide in the air has been found in a 9,10-bis(4-substituted styryl)anthracene series, in 4-substituted 4′-nitrostilbene series, and in 1-(p-nitrophenyl)-4-(p-substituted phenyl)-1,3-butadiene series; its scope and limitations have been examined. The ESR spectrum of the reaction against 4-diethylamino-4′ -nitrostilbene was measured to identify an anion radical species expected for explanation of the mechanism of the dehydrogenation reaction. Further, cyclic voltammetric measurements of a series of stilbenes and diphenylacetylenes were carried out in connection with the above mechanism. In many cases, interestingly, the use of a large excess of t-BuOK brought about succeeding hydroxylation into the ortho-position of a nitro group on the benzene nucleus. The simple hydroxylation is useful for the synthesis of substituted 5-(arylethynyl)-2-nitrophenols, which are expected to function as non-linear optical materials with the corresponding non-hydroxy compounds. The ultraviolet-visible and fluorescence spectral properties were measured and discussed also with those of the related compounds.
Hafnium(IV) Trifluoromethanesulfonate, An Efficient Catalyst for the Friedel–Crafts Acylation and Alkylation Reactions
Authors: Hachiya Iwao , Moriwaki Mitsuhiro , Kobayashi Shu 
Published: July 2006

Abstract
Hafnium(IV) trifluoromethanesulfonate (hafnium(IV) triflate, Hf(OTf)4) was synthesized from hafnium tetrachloride and trifluoromethanesulfonic acid. The triflate thus prepared was found to be effective in the catalytic Friedel–Crafts acylation reactions of various substituted benzenes with acid anhydrides in lithium perchlorate–nitromethane (LiClO4–MeNO2). Lithium perchlorate–nitromethane is an excellent solvent system, and the catalytic activity of the Lewis acid was much improved in this medium. The product was obtained in up to 250000% molar amounts based on the catalyst. Hafnium(IV) triflate was also found to be quite effective in the catalytic Friedel–Crafts alkylation reactions of aromatic compounds with alkyl chlorides. The reactions proceeded smoothly in the presence of 5% molar amount of Hf(OTf)4 and 50% molar amount of LiClO4 by using a slow addition procedure.
Studies on the Complex Formation between Iron(III) or Copper(II) and Poly(vinyl alcohol) in Terms of Inclusion of the Metal Hydroxide-Like Clusters by the Polymer
Authors: Yokoi Hiroshi , Mori Yasuyoshi , Fujise Yutaka 
Published: July 2006

Abstract
The complex formation between iron(III) or copper(II) and poly(vinyl alcohol) (PVA) in aqueous solution has been investigated in some detail by using many PVAs ranging in degree of polymerization (DP) from 33 to 500. The minimum concentration of PVA required to form soluble complexes has been found to be inversely proportional to its DP, as expressed by the constancy of (DP of PVA) × [PVA]; the constants were 13 and 15 M in 10 mM iron(III) and copper(II) solutions (1 M = 1 mol dm−3), respectively. It has been revealed that iron(III) and copper(II) ions in the complexes exist in the form of metal hydroxide-like clusters comprising, at most, 120 metal ions per PVA chain. Transmission electron micrographs for the cast films of an iron(III) complex solution have shown the cluster size to be about 30 Å. Poly(vinyl methyl ether), a methyl ether derivative of PVA, was similar to PVA in complex formation with iron(III) up to pH 5. This fact also supports the conclusion that the present PVA complexes are of an inclusion type due to a hydrophobic interaction.
Study on the Interaction between Iron(III) Hydroxide Oxide and Cation Exchange Resins
Authors: Inami Ichiro , Baba Takao 
Published: July 2006

Abstract
In some nuclear power plants, ion exchange resins for condensate purification systems show increasing rust removal efficiency year by year. In order to clarify this phenomenon, resin properties and rust behavior after adsorption on the resins have been studied. An adsorption test, a dissolution test and an ion exchanging test were performed in this study, using strongly acidic cation exchange resins, amorphous iron(III) hydroxide oxide and 55Fe tracer. It was found that aged cation exchange resins showed obvious property changes due to oxidative swelling, which induced better water mobility in the micropores. According to the property change, amorphous iron(III) hydroxide oxide, one of the iron rust components, is easily dissolved and diffused into resin beads, and consequently adsorption sites on aged resins are recovered rapidly compared with fresh resins. This is the reason for the superiority of the aged cation exchange resins in rust removal.
Formalized Drawing of Fullerene Nets. 2. Applications to Mapping of Pyracylene Rearrangements, C2-Insertion/Elimination Pathways, and Leapfrog/Carbon Cylinder Operations
Authors: Yoshida Mitsuho , Osawa Eiji 
Published: July 2006

Abstract
The net drawing method of fullerenes presented in the preceding paper has been applied to the predictive studies on the movements of pentagonal rings accompanying skeletal transformations in fullerenes. The products of pyracylene rearrangements have been systematically generated to examine low-energy isomers containing abutting pentagons (so-called anti-IPR isomers) by performing the rearrangement only once on all the pyracylene units in each of the C60 to C100 isomers. The Endo-Kroto mechanism of C2-insertion into the carbon framework of fullerene has been likewise shown to be executable on paper. In this way, several energetically favorable pathways of growth have been found for C76 to C90. Potential applications of net drawing to the leapfrog and carbon cylinder operations and C2-elimination are also mentioned.
C–H···π Hydrogen Bonding between Electron-Rich Benzene Rings and Polarized C–H Bonds: Selectivity in the Complexation of Highly Hydrophilic Guest Molecules with Calix[4]resorcarene Hosts in Water
Authors: Fujimoto Takako , Yanagihara Ryoji , Kobayashi Kenji , Aoyama Yasuhiro 
Published: July 2006

Abstract
Tetrasulfonate derivatives of calix[4]resorcarene (calix[4]arene derived from resorcinol) (1) form 1 : 1 complexes with highly hydrophilic guest molecules, such as ethers, alcohols, ketones, and sulfoxides, in water. The affinities of three types of the guests increase in the order CH3–X–CH3 &lt; (–CH2CH2–X–)2 &lt; CH3–X–CH2CH2–X–CH3 (X = O, CH(OH), C=O, or S=O), reflecting the importance of multiple host-guest interactions. The binding constants (K) with respect to X increase in the order O &lt; CH(OH) &lt; C=O &lt; S=O or CH(OH) &lt; O &lt; C=O &lt; S=O. As for the effects of substituents Y on 2-C of the benzene rings of the host, both 1b (Y = CH3) and 1c (Y = OH) exhibit higher binding capabilities than does the parent host 1a (Y = H). Thus, the present complexation is promoted by electron-withdrawing residue (X) in the guests and electron-donating substituents (Y) in the host. The binding of CH3–X–CH3 (X = C=O or S=O) to hosts 1a—c is characterized by favorable enthalpy changes and unfavorable entropy changes. These results, coupled with NMR data, indicate that the driving force of the present complexation is a C–H···π interaction between C–H bonds of a guest as soft acids and benzene rings of the host as soft bases.
Basic Properties of Polylactic Acid Produced by the Direct Condensation Polymerization of Lactic Acid
Authors: Ajioka Masanobu , Enomoto Katashi , Suzuki Kazuhiko , Yamaguchi Akihiro 
Published: July 2006

Abstract
The direct condensation polymerization of lactic acid has been studied, and polylactic acid having a high molecular weight was obtained in an organic solvent without any isolation of the intermediate, dilactide. The molecular weight was raised up to 300000 through the examination of several reaction conditions, e.g., solvent, catalyst, etc. Thus-obtained high-molecular-weight polylactic acid can be processed into films and molded products having sufficient strength and toughness. The characteristic features of polylactic acid obtained by this direct process were compared to that obtained by the conventional ring-opening polymerization process. In addition, copolymerization of lactic acid with a variety of d/l ratios is discussed.
Stability of Colloidal Alumina in the Presence of Various Inorganic Anions
Authors: Petkovic Milan Dj , Milonjic Slobodan K , Dondur Vera T 
Published: July 2006

Abstract
The stability of colloidal alumina in the presense of selected inorganic anions (NO3−, Cl−, I−, SO42−, and [Fe(CN)6]3−) has been studied by a potentiometric titration technique. The dependencies of the critical concentrations of coagulation on the solution pH were determined for all studied anions, as well as the regions of coagulation and stability of the system. It has been shown that the critical concentrations of coagulation decrease along with an increase in the pH, which is interpreted by coagulation theory and the electrical layer model. Differences between the critical concentrations of coagulation at the same pH value for monovalent anions are explained based on their hydration degree differences, while the discrepancies between the experimental data and the theoretical values given by the Schultze–Hardy law are interpreted in light of specific sorption of sulfate anions and the general specificity of the investigated system. Based on a parallel stability study of colloidal alumina prepared in the laboratory and of a commercial product, the same stability behavior in the presence of KCl has been found.
The Physicochemical Properties of a Nonaqueous Microemulsion: Cyclohexane/Triton® X-100/Dimethylformamide at 40 °C
Authors: Tessy Elavathingal Itteera , Rakshit Animesh Kumar 
Published: July 2006

Abstract
The phase diagram of a nonaqueous microemulsion system containing cyclohexane/Triton® X-100/DMF was determined at 40 °C. The one-phase microemulsion area increased in the presence of a cosurfactant. Physical properties like viscosity, adiabatic compressibility, specific conductance, and contact angle are discussed at a surfactant concentration of 15% to explain the microstructure. A cyclohexane/TX 100+1-propanol/DMF system shows percolation, though not high, with ca. 0.15 mole fraction of DMF. Contact angle measurements of cyclohexane/TX 100/DMF at various cyclohexane/DMF ratios show a DMF continuous system. In the presence of a cosurfactant, the contact angle values show a continuous change indicating an 0/DMF to bicontinuous to DMF/0 structure. NaI does not introduce a three-phase liquid system.
Rotational Effects on Radiationless Transition IV: Hyperfine Interaction and Deuterium Isotope Effects
Authors: Kanamaru Nobuaki 
Published: July 2006

Abstract
The theory of the rotational effects on radiationless transitions in typical azines is extended to include the hyperfine (hf) interaction term, while examining their deuterium (isotope) effects on the decay behaviors after excitation into the rotational levels belonging to their S10 levels, i.e. their ground vibrational levels of S1 states. The Fermi-contact hf term is shown to be enough to endorse the coupling between rotational levels that are different either in symmetries or in some angular-momentum quantum numbers. The deuterium (D) effect is found to be not simply described as a conventional isotope effect: Changes by D substitution are brought about in densities of triplet states and hf coupling terms, as well as molecular symmetry groups. While interpreting the experimental data, modifications of the schemes are made from those presented earlier in this series.
Dielectric Characterization of Binary Solvents Containing 1,2-Dichloroethane and 2-Chloroethanol
Authors: Corradini Fulvio , Marchetti Andrea , Tagliazucchi Mara , Tassi Lorenzo , Varini Alessandra 
Published: July 2006

Abstract
Static dielectric constants (ε) were determined for the 1,2-dichloroethane (DCE, 1)/2-chloroethanol (CE, 2) binary solvent system at 19 temperatures ranging from −10 to +80 °C and in the whole composition range expressed by the mole fraction 0 ≤ X1 ≤ 1. The experimental values have been fitted to some equations that could be usefully employed for predictive ε calculations. Furthermore, the excess mixing properties (εe) have been evaluated in order to point out the presence of solvent–cosolvent adducts in the binary mixtures mentioned above. The values of εe have been generally found to be negative and only slightly positive under a few experimental conditions in the CE rich-region, thus giving evidence of a close interaction network probably via hydrogen bonding as well as other interactions of every kind in this solvent system.
Investigation of Spin-Correlated Ion Pairs in Distance-Fixed Triads by Time-Resolved Electron Paramagnetic Resonance
Authors: Nakamura Hirofumi , Terazima Masahide , Hirota Noboru , Nakajima Satoshi , Osuka Atsuhiro 
Published: July 2006

Abstract
Charge separated ion-pair (IP) states formed from three distance-fixed photosynthetic triads were studied by the time-resolved EPR method. Upon photoexcitation of the triads in THF at 77 K, small and narrow signals were observed at the central parts of broad EPR spectra due to the excited triplet states of the chromophores. These signals were assigned to secondary, fully charge separated IP states by the simulation based on the spin-correlated radical pair mechanism. Time dependence of the TREPR signals indicates that charge separation occurs in the singlet manifold as in the case of the photoexcited state dynamics at room temperature. Estimated electron exchange interactions, J, are in the order of 10−2—10−3 mT, which is in line with the observed long lifetimes of the IP states.
Molecular Conformation of Tetragastrin in Aqueous Solution by the Monte-Carlo Simulation
Authors: Kuroda Masataka , Yamazaki Kazuto , Taga Tooru 
Published: July 2006

Abstract
A conformational analysis of tetragastrin in an aqueous solution was carried out by a Monte-Carlo simulation, assuming a molecular model in a continuous media. The hydration energy of the peptide was evaluated from a calculations of the peptide–water accessible surface area. The tetrapeptide conformers in the low-energy state take an extended form, in which the two aromatic rings on both termini of the peptide are apart. The extended conformation in which the hydrophilic portions are exposed to solvent water is quite different from that in DMSO.
Electrocatalytic Behavior of Poly(2,5-dihydroxyaniline) Synthesized by Electropolymerization in Aqueous Solutions
Authors: Morita Masayuki , Takase Hironari , Ishikawa Masashi , Matsuda Yoshiharu 
Published: July 2006

Abstract
Poly(2,5-dihydroxyaniline), or poly[imino(2,5-dihydroxy-1,4-phenylene)] (PAn(OH)2), films were prepared by electropolymerization of 2,5-dimethoxyaniline (DMA), followed by electrochemical hydrolysis of methoxyl groups in an acidic solution. The films gave responses characteristic of a hydroquinone/quinone couple in aqueous solutions, suggesting that many hydroquinone units are introduced in the polymer structure. Although the polymer in the reduced state consisted of aniline units with substitutions by hydroxyl groups, its redox process is based on the reaction of hydroquinone/quinone couple in its structure, not on the doping/undoping in the aniline unit. Electrochemical redox processes were examined on the PAn(OH)2-modified platinum electrode. The polymer films showed electrocatalytic activities for such redox reactions as the oxidation of [Fe(CN)6]4−, Fe2+, and [Co(NH3)6]2+ in aqueous solutions. Some interactions were suggested between the hydroquinone/quinone site or the aniline unit in the polymer and the redox active metal complexes in the solution and/or in the polymer.
The Role of Nonadiabatic Coupling in Bond-Selective Dissociations: Two-Dimensional Model Calculations
Authors: Takayanagi Toshiyuki , Yokoyama Atsushi 
Published: July 2006

Abstract
The photodissociation dynamics of the model CH2XY (X and Y are halogen atoms) molecule was studied using a time-dependent quantum mechanical method in two dimensions. Simple functional forms were employed as two diabatic potential energy surfaces which correspond to the excited states of C–X (n–σ*) and C–Y (n–σ*). Bond selectivity in the photodissociation is quantitatively examined in terms of the coupling strength between the two surfaces. A method to predict the bond selectivity in the photodissociations is also discussed on the basis of the results of ab initio molecular orbital calculations.
Electrochemical Properties of Carbon-Paste Electrodes Spiked with Some 1,4-Naphthoquinone Derivatives
Authors: Raoof DJahan B , Golabi Seyed M 
Published: July 2006

Abstract
The preparation and aqueous electrochemistry of a carbon-paste electrode, modified by 1,4-naphthoquinone and some of its derivatives are described. From a calculation of the half-wave potential as a function of the pH, potential-pH diagrams were constructed for each compound. The values of the formal potentials and the pKa′ of some different redox and acid-base couples involved at various solution pHs were obtained. The influence of such substituents as methyl-, hydroxy-, chloro-, and amino- concerning the electrochemical behavior of surface 1,4-naphthoquinone is described. The electrochemical behavior of such electrodes was examined in buffered borate solutions and the formation of a complex between borate anion and o-naphthalenediols was characterized. Finally, the range of the pH at which the electrode function is consistent was determined.
Steric Trans Influence of Aminomethane Ligand in trans-Aminomethanechlorobis(1,2-diaminoethane)cobalt(III)
Authors: Mizuta Tsutomu , Kusakari Kenji , Hashimoto Mari , Miyoshi Katsuhiko 
Published: July 2006

Abstract
The trans isomer of aminomethanechlorobis(1,2-diaminoethane)cobalt(III), trans-[CoCl(NH2Me)(en)2]2+, was prepared from trans-[CoCl(NO2)(en)2]+ by a two-step reaction in which Cl− was replaced with an NH2Me and then the remaining NO2− was replaced with a Cl−. The configuration was confirmed by X-ray crystal analysis, and structural comparison was made with its cis isomer. The crystals have the formulae, trans-[CoCl(NH2Me)(en)2]Cl(ClO4) and cis-[CoCl(NH2Me)(en)2]Cl2. The crystallographic data are as follows; Monoclinic, P21/c, a = 11.515(1), b = 7.421(2), c = 17.257(1) Å, β = 99.220(8) °, V = 1455.6(5) Å3, Z = 4, and R = 0.043 for the former, and Orthorhombic, Fdd2, a = 26.64(1), b = 27.26(1), c = 7.570(2) Å, V = 5497(3) Å3, Z = 16, and R = 0.057 for the latter. The Co–Cl bond of the trans complex is longer than that of the cis complex. It was found that the bulkiness of the Me group effects the trans Co–Cl bond through one of the two flexible equatorial en chelate rings. The kinetic data of an aquation reaction of the trans and the cis complexes show that the Cl− of the trans complex is substituted more readily than that of the cis is.
Analysis of d–d Transitions in trans-[Cr(CN)2(NH3)4](ClO4) as Inferred from Polarized Optical Spectra and Angular Overlap Model Calculations
Authors: Schönherr Thomas , Itoh Mutsuyoshi , Urushiyama Akio 
Published: July 2006

Abstract
The polarized absorption spectra of trans-[Cr(CN)2(NH3)4](ClO4), which crystallizes in the orthorhombic space group Pna21, were measured in spin-allowed quartet ( → ) and intraconfigurational spin-forbidden doublet ( → ) transition regions. Gaussian deconvolution of the quartet bands and detailed vibronic assignments of the spin-forbidden doublet transitions yielded a total of seven electronically excited states. These have been used for ligand field calculations in terms of the angular overlap model. By using a π-orbital reduction factor of τ = 0.984 as well as a negative eπ value for the acceptor ligand CN− (−930 cm−1) we were able to reproduce the d-level scheme in high accuracy. The results compare well with our findings for the related monocyano complex.
Reactivity of Five-Coordinate Intermediate Generated by Laser Photolysis of Monoligated Chloro(5,10,15,20-tetraphenylporphinato)chromium(III) in Toluene
Authors: Inamo Masahiko , Hoshino Mikio , Nakajima Kiyohiko , Aizawa Sen-ichi , Funahashi Shigenobu 
Published: July 2006

Abstract
The Cr(III) porphyrin complexes [Cr(tpp)(Cl)(H2O)] (1) and [(Cr(tpp)(Cl)(py)] (2) (tpp represents the dianion of 5,10,15,20-tetraphenylporphine) crystallized from a chloroform–toluene mixture in the tetragonal space group I4, Z = 2, a = 13.559(5), b = 13.559(5), c = 9.770(3) Å, V = 1796(3) Å3, and from a dichloroethane–toluene mixture containing a small amount of pyridine (py) in the monoclinic space group P21/n, Z = 4, a = 14.655(5), b = 23.498(4), c = 13.152(2) Å, β = 101.54(1)°, V = 4437(2) Å3, respectively. The axial Cr–O bond length for 1 and the axial Cr–N bond length for 2 are 2.239(3) and 2.140(5) Å, respectively. Laser irradiation of the toluene solution of [Cr(tpp)(Cl)(L)] causes the photodissociation of the axial ligand L, where L represents H2O or 3-cyanopyridine, to give the five-coordinate intermediate [Cr(tpp)(Cl)]. The rate constant of the axial ligand recombination reaction falls into a narrow range around 1 × 109 mol−1 kg s−1 at 25.0 °C for both reactions. The activation parameters indicate the very high reactivity of the five-coordinate intermediate. The diffusion-controlled process is regarded as a rate-determining step for the recombination.