bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micelle Formation by Anionic and Cationic Surfactants in 18-Crown-6 Ether + β-Cyclodextrin + Water Systems
Authors: Bakshi Mandeep Singh , Kohli Pooja , Kaur Gurinder 
Published: June 2006

Abstract
The conductances of sodium decyl sulfate (SDeS), sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB), and trimethyltetradecylammonium bromide (TTAB) have been determined in 18-crown-6 ether + water (CR + W), β-cyclodextrin + W (CYC + W), and in CR + CYC + W mixtures with fixed 0.0151 mol dm−3 of CR and varying the amount of CYC with the overall change in the mole–fraction range of CYC from 0.0 to 0.5 in a CR + CYC + W mixture at 30 °C. From the conductivity data, the critical micellar concentration (cmc), degree of counter ion dissociation (β), free energy of transfer of the surfactant hydrocarbon chain from medium to the micelle (), and free energy of transfer of surface contributions () of SDS, SDeS, DTAB, and TTAB have been computed. It has been found that the micelles of anionic surfactants are stabilized in a CR + W mixture in comparison to that in pure water, whereas micelles of cationic surfactants remain more or less unaffected. Micelles of all of the above surfactants are denatured as the amount of CYC is increased in the CR + CYC + W mixture. The effect of denaturisation is stronger on the micelles of SDS and TTAB in comparison to that of SDeS and DTAB, respectively.
Studies on Photochemical Processes of Xanthene Dyes by Means of the Transient Absorption Spectra in the Visible/Near-IR Regions
Authors: Islam Shafiqul D-M , Yoshikawa Yuko , Fujitsuka Mamoru , Watanabe Akira , Ito Osamu 
Published: June 2006

Abstract
The rate constants for quenching of the triplet states of eosin and erythrosin (3D*) with various substrates have been evaluated using nanosecond laser flash photolysis while observing the transient absorption bands in the visible/near-IR regions. Intense transient absorption bands due to 3D* were observed at about 1040 nm. An energy-transfer reaction from 3D* to anthracene-9-carboxylic acid was confirmed by the appearance of the absorption band of the triplet state of the acid at 425 nm. The ion radicals of electron donors and electron acceptors were also observed with the decay of 3D*, indicating the occurrence of an electron-transfer reaction. High hydrogen-abstraction abilities of 3D* were also confirmed for substituted phenols and benzenethiols. The negative slopes of the Hammett plots indicate that the reaction center of 3D* has a highly electrophilic nature.
Fluorescence and Phosphorescence Properties of Naphthalene in Aqueous d-Glucose Solutions Containing 6-Deoxy-6-iodo-β-cyclodextrin at Room Temperature
Authors: Hamai Sanyo 
Published: June 2006

Abstract
In aqueous solutions, 6-deoxy-6-iodo-β-cyclodextrin (β-CDI) forms a 1 : 1 inclusion complex with naphthalene. The naphthalene fluorescence is quenched upon the formation of the inclusion complex with β-CDI. The room-temperature phosphorescence of naphthalene has been observed from aqueous naphthalene solutions containing both d-glucose and β-CDI. Although the room-temperature phosphorescence has also been observed from aqueous naphthalene solutions containing both d-glucose (5.0 g/5.0 mL) and β-cyclodextrin (1.0 × 10−2 mol dm−3), its intensity amounts to at most 9% of that containing d-glucose (5.0 g/5.0 mL) and β-CDI (1.0 × 10−3mol dm−3). In addition to the high viscosities of d-glucose solutions, the external heavy atom effects of β-CDI cause the appearance of the room-temperature phosphorescence. The room-temperature phosphorescence quantum yield of naphthalene in d-glucose (5.0 g/5.0 mL) solution containing β-CDI (1.0 × 10−3 mol dm−3) has been estimated to be 2.2 × 10−3, which is around 1.8% of the intrinsic phosphorescence quantum yield of naphthalene in ethanol at 77 K.
An Evaluation of the Overall Rotational Correlation Times of Tetraalkylammonium Ions in Solution. 13C NMR Relaxation Study
Authors: Masuda Yuichi , Tobita Junko , Muramoto Akiko 
Published: June 2006

Abstract
The 13C NMR spin-lattice and spin–spin relaxation times (T1 and T2), and the nuclear Overhauser effect (NOE) were measured for tetraalkylammonium ions (R4N+, R = C2H5 (Et), n-C3H7 (n-Pr), n-C4H9 (n-Bu), and n-C5H11 (n-Pen)) in the concentrated aqueous solutions of their bromides or chlorides. A minimum was observed in the temperature dependence of T1 for the α-carbon in each solution. The value was 1.2—1.4 times higher than that predicted assuming only the isotropic overall rotation of the R4N+ ion. This increase in the T1 minimum values was ascribed to the rotations around the N–α-C bonds with an restriction in the azimuthal angle for each bond. The ranges where the N–α-C bonds could rotate with the time scales much less than those for the overall rotations were determined by the values of the T1 minima for the corresponding R4N+ ions as ±20°, ±17°, ±20°, and ±20° centering the gauche conformations, respectively, for Et4N+, n-Pr4N+, n-Bu4N+, and n-Pen4N+. These values well reproduced the T2 and NOE values observed at various temperatures in the concentrated aqueous solutions of the R4N+ halides. By using the thus obtained ranges of the azimuthal angles, the overall rotational correlation times in the dilute aqueous solutions (0.01 mol kg−1) were also determined. The obtained rotational correlation times were compared with those calculated using the Stokes–Einstein–Debye equation and the effect of the hydrophobic hydration was discussed.
Crystal and Molecular Structures of RCH2CH2SCH3 (R = OCH3, SCH3)
Authors: Yokoyama Yoshihiro , Ohashi Yuji 
Published: June 2006

Abstract
The crystal structures of 1-methoxy-2-(methylthio)ethane (MMTE) and 1,2-bis(methylthio)ethane (BMTE), which are liquid materials at room temperature, have been analyzed by X-rays at 143 and 243 K, respectively. The crystal of MMTE belongs to the monoclinic system and the space group is P21/n. The cell dimensions are; a = 8.416(1), b = 7.817(2), c = 10.181(2) Å, β = 113.79(1)°, and V = 612.8(2) Å3. The MMTE molecule has a TTG conformer, which is different from the most stable one derived from the ab initio molecular orbital calculation on the MP2/6-31G* basis set. The crystal of BMTE belongs to the monoclinic system and the space group is P21/c. The cell dimensions are; a = 6.549(1), b = 5.835(1), c = 8.728(1) Å, β = 97.330(9)°, and V = 330.7(1) Å3. The BMTE molecule lies on an inversion center and has a GTG′ conformer, which is consistent with the most stable one derived from the ab initio calculation. The relative stability of these crystal structures and the possibility of crystal structures with the other conformers were examined by the molecular mechanics calculation. Trials to make a mixed crystal with MMTE and BMTE were in vain.
Effect of Guest Species on Inclusion Compound Formation of Deoxycholic Acid by Co-Grinding
Authors: Oguchi Toshio , Limmatvapirat Sontaya , Takahashi Chikako , Sungthongjeen Srisagul , Choi Woo Sik , Yonemochi Etsuo , Yamamoto Keiji 
Published: June 2006

Abstract
Deoxycholic acid (DCA) was ground with a guest compound by using a vibrational mill. Powder X-ray diffraction, differential scanning calorimetry, and fluorescence spectroscopic data indicated the formation of the inclusion complex in the ground mixture of DCA–phenanthrene and DCA–naphthalene systems. The DCA–naphthalene ground mixture was found to have higher crystallinity than the DCA–phenanthrene ground mixture, and this was assumed to relate to the difference in the crystallization temperature of the inclusion complex. When low-temperature grinding was performed for DCA and other aromatic hydrocarbons along with naphthalene and phenanthrene, all the ground mixtures were obtained in amorphous state. Crystallization of inclusion compounds from the amorphous ground mixtures was observed to occur at a higher temperature as the stoichiometric ratio (DCA/guest) of the compound increased. With regard to the formation of crystalline complex between DCA and a guest, such as naphthalene, by grinding at room temperature, a two-step mechanism was proposed: i.e., (i) amorphization of both DCA and guest crystals, and (ii) crystallization of the inclusion complex induced above a certain temperature.
Synthesis and Characterization of Hexadentate Cobalt(III) Complexes with New edta-Type Ligands Part 5. Structure and Absolute Configuration of the trans(O5)(−)546-Isomer of Lithium (Ethylenediamine-N,N,N′-triacetato-N′-3-propionato)cobaltate(III) Monohydrate, (−)546-trans(O5)-Li[Co(ed3ap)]·H2O. Strain Analysis of [Co(edta-Type)]− Chelates in Relation to Their Octahedral Distortion
Authors: Radanovic Dušan J , Miletic Vesna D , Ama Tomoharu , Kawaguchi Hiroshi 
Published: June 2006

Abstract
The preparation and resolution of the two hexadentate Co(III) complexes containing unsymmetrical edta-type ligands, [Co(ed3ap)]− (A) and [Co(u-eddadp)]− (B) (ed3ap = ethylenediamine-N,N,N′-triacetate-N′-3-propionate ion; u-eddadp = ethylenediamine-N-diacetate-N′-di-3-propionate ion) have been reexamined. The X-ray data are reported for the Λ-(−)546-trans(O)5-Li[Co(ed3ap)]·H2O for which the same (Λ) absolute configuration was predicted from the CD sign pattern of the lowest energy band. The complex crystallizes in the space group P21 (#4) of the monoclinic crystal system with a = 6.523(4), b = 15.025(7), c = 7.464(3) Å, β = 105.40(4)°, and Z = 2. The conformations of the chelate rings are found to be envelope for the glycinates and skew-boat (half-chair) for the β-alaninate ring. Structural parameters and strain analysis of [Co(edta-type)]− chelates are discussed in relation to the structure of the ligand and octahedral distortion of complexes. The CD and IR (carboxylate region) spectra of complexes A and B are also discussed.
Association Constants of Ferrocene with Cyclodextrins in Aqueous Medium Determined by Solubility Measurements of Ferrocene
Authors: Wu Ji-Shi , Toda Kei , Tanaka Akira , Sanemasa Isao 
Published: June 2006

Abstract
The association constants of ferrocene with cyclodextrins (CyD’s) in an aqueous medium at 25 °C have been determined by solubility measurements of ferrocene in both the absence and presence of CyD. The solubility of ferrocene in pure water was found to be (4.25 ± 0.02) × 10−5 mol dm−3 at 25.0 ± 0.1 °C. The β- and γ-CyD’s form only 1 : 1 complexes with ferrocene. The 1 : 1 association constants were determined to be (1.39 ± 0.21) × 102 (α), (1.65 ± 0.04) × 104 (β), and (9.04 ± 0.11) × 102 dm3 mol−1 (γ). The 2 : 1 (CyD : ferrocene) association constant was (2.36 ± 0.06) × 103 dm3 mol−1 (α). Ferrocene-included CyD precipitates were also prepared in water, and their stability upon drying in air was studied. The sublimation enthalpy of ferrocene in the temperature range of 290.65 to 298.15 K was estimated to be 74.2 ± 1.5 kJ mol−1.
Synthesis, Structure, and Thermolysis Mechanism of S-Alkoxythiazynes
Authors: Yoshimura Toshiaki , Ohkubo Masanori , Fujii Takayoshi , Kita Hiroshi , Wakai Youko , Ono Shin , Morita Hiroyuki , Shimasaki Choichiro , Horn Ernst 
Published: June 2006

Abstract
S-Alkoxy-S,S-diarylthiazynes were prepared by two methods: the alkaline hydrolysis of S,S-diaryl-N-halosulfilimines in aqueous alcohols and the reaction of S,S-diaryl-S-fluorothiazynes with sodium alkoxides. The structure of S,S-diphenyl-S-propoxythiazyne was determined by an X-ray crystallographic analysis, which showed a short SN bond length of 1.441(3) Å. The thermolysis of S-alkoxythiazynes gave elimination products, which were identified as the corresponding carbonyl compounds and N-unsubstituted S,S-diarylsulfilimines. Kinetic experiments for the thermolysis of the S-alkoxy-S,S-diarylthiazynes were carried out. The first-order kinetic behavior, a large kinetic isotope effect (kH/kD = 6.1) using S,S-diphenyl-S-[1,1-2H2]propoxythiazyne, a negative activation entropy (ΔS‡ = −30 J K−1mol−1), and a negative Hammett ρ-value (ρ = −0.35) on the phenyl group were obtained, suggesting that the reaction proceeds via a concerted five-membered cyclic transition state. A deviation from the ideal concerted transition state is discussed in comparison with that for sulfoxides.
Intramolecular Cyclization of 4-[3-(Trimethylsilyl)prop-1-en-1-yl]cyclohexanecarbaldehyde with Loss of Formyl Carbon
Authors: Kuroda Chiaki , Murase Atsushi , Suzuki Hideyuki , Endo Toru , Anzai Shuzo 
Published: June 2006

Abstract
Treatment of cis- and trans-4-[3-(trimethylsilyl)prop-1-en-1-yl]cyclohexanecarbaldehyde (2a and 2b) with tetrabutylammonium fluoride in dilute tetrahydrofuran afforded 7-vinylbicyclo[2.2.1]heptan-1-ol (3), the same product obtained from 4-[3-(trimethylsilyl)prop-1-en-1-yl]cyclohexanone (1). It was found that oxidative deformylation of 2a, b to 1 takes place under basic conditions before the cyclization to 3. It was also shown that cyclization of allylsilane with carbonyl does not proceed via an eclipsed conformation.
Photoamination of Alkenylnaphthalenes with Ammonia via Electron Transfer
Authors: Yasuda Masahide , Kojima Ryuji , Ohira Ryujiro , Shiragami Tsutomu , Shima Kensuke 
Published: June 2006

Abstract
The photoamination of 1-(2-methyl-1-propenyl)naphthalene (1a) with ammonia in the presence of p-dicyanobenzene (p-DCB) occurred selectively at the alkenyl group but not at the naphthyl group to give 1-(2-amino-2-methylpropyl)naphthalene (2a). Similarly, the photoamination of several kinds of alkenylnaphthalenes (1) proceeded selectively at the alkenyl group. The photoamination proceeded via the nucleophilic addition of ammonia to the cation radical of 1 generated by the photoinduced electron transfer to p-DCB to give the aminated radical after deprotonation. Distribution of the positive charge in 1+• and the stabilities of the aminated radicals were calculated by the PM3-UHF method. The stabilities of the aminated radicals agreed with the regioselectivity.
The Role of Arginine in Thrombin Receptor Tethered-Ligand Peptide in Intramolecular Receptor Binding and Self-Activation
Authors: Nose Takeru , Satoh Yusuke , Fujita Tsugumi , Ohno Motonori , Nakajima Masahide , Inoue Yoshihisa , Ogino Yoshio , Costa Tommaso , Shimohigashi Yasuyuki 
Published: June 2006

Abstract
Synthetic heptapeptide of the human thrombin receptor tethered-ligand peptide, H–Ser–Phe–Leu–Leu–Arg–Asn–Pro–NH2 (SFLLRNP), activates fully the thrombin receptor without thrombin. The functional role of Arg-5 was examined using a series of analogs having amino acid substitutions at position 5 in this assays was to assess the abilities to hydrolyze phosphoinositide in human neuroblastoma SH-EP cells and to aggregate the human platelet. The replacement of Arg-5 by Ala reduced the activity (9% activity of the parent peptide) in the PI-turnover assay, and abolished completely the platelet aggregation activity. SFLL/Lys/NP was also active, but moderately: 36% in PI-turnover and 12% in platelet aggregation. These results indicated that the electrostatic interaction of the Arg-guanidino group is important for a peptide to interact with the receptor. When citrulline or glutamine was placed at position 5 instead of arginine, the resulting SFLL/citrulline/NP and SFLL/Gln/NP were found to be potent in both assays. Since citrulline and glutamine possess a side chain which can serve as hydrogen donor and/or acceptor, the receptor activation of these peptides appears to be due to hydrogen bonding at this position. The molecular mechanisms to explain both electrostatic and hydrogen-bonding interactions were postulated based on the structural modeling of seven-transmembrane domain thrombin receptor.
Synthesis and Reduction of Octasilyl[4]radialene. Structure and Dynamic Study of [4]Radialene Dianion with Eight-Center Ten-Electron π-System
Authors: Matsuo Tsukasa , Sekiguchi Akira , Ichinohe Masaaki , Ebata Keisuke , Sakurai Hideki 
Published: June 2006

Abstract
The intramolecular reaction of 3,3,5,5,8,8,10,10,13,13,15,15,18,18,20,20-hexadecamethyl-3,5,8,10,13,15,18,20-octasilacycloicosa-1,6,11,16-tetrayne (1) with three molar amounts of [Mn(CO)3(Me-Cp)] in THF under photochemical and refluxing conditions produced octasilyl[4]radialene derivative (2). The reaction of 2 with alkali metals (Li, Na, and K) in THF gave dialkali metal salts of the corresponding dianion (4) with an eight-center ten-electron π-system. The molecular structure of dilithium salt of octasilyl[4]radialene dianion (4a) has been established by X-ray crystallography. The two lithium atoms are located above and below and are bonded to the atoms of the radialene framework to give a bis-CIP structure. The structural parameters of 4a are discussed in comparison to those of 2. The structure of 4a in solution has also been discussed on the basis of NMR spectroscopic data. The two Li+ ions of 4a are not fixed to the π-skeleton in toluene-d8, but are fluxional, giving a symmetric structure (bis-CIP) on the NMR time scale. In a solvating medium such as THF-d8, one of the Li+ ions dissociates to yield an ion pair (CIP and SSIP). Some evidence for the Li+ ion walk on the π-skeleton is demonstrated.
Coumarin and Thiocoumarin Dyes for Guest–Host Type Liquid Crystal Displays
Authors: Iwanaga Hiroki , Naito Katsuyuki , Sunohara Kazuyuki , Okajima Masaki 
Published: June 2006

Abstract
To realize bright and pure colors in Guest–Host type Liquid Crystal Displays (GH-LCDs), the solubilities and/or absorption coefficients of dichroic dyes which are dissolved in liquid crystals are the most important properties. We have found that a mixture of coumarin and anthraquinone dyes was very useful because it had a large absorption coefficient and little fluorescence. On the other hand, substitution of a sulfur atom for an oxygen atom of the coumarin dye contributes to increase its solubility to liquid crystals, particularly at low temperatures.
Effects of Pressure on the DNA Minor Groove Binding of Hoechst 33258
Authors: Tang Guo-Qing , Tanaka Naoki , Kunugi Shigeru 
Published: June 2006

Abstract
We investigated the pressure perturbations of DNA minor groove binding of the antibiotic drug Hoechst 33258 (2′-(4-hydroxyphenyl-5-(4-methyl-1-piperazinyl)-2,5′-bi-1H-benzimidazole trihydrochlolride) on fluorescent titrations and on restriction endonuclease protection assays. Significantly, pressure elevations were found to disturb the binding of Hoechst 33258 with poly(dA)·poly(dT) and poly[d(A–T)]·poly[d(A–T)] in opposite directions, which suggested different volume changes (sign and size) in their complexation reactions. The ability of Hoechst 33258 to provide the restriction endonuclease protection for plasmid DNA was notably enhanced by the application of pressure, implying that there is a large volume contraction following the EcoRI site-drug interaction. These data were explained by DNA hydration and its effects on the ligand complexation that is sequence dependent.
Estimation of the Surface-Diffusion Coefficient in Gas-Phase Adsorption Using Octadecylsilyl-Silica Gel
Authors: Miyabe Kanji , Takeuchi Shigeya , Tezuka Yoshisato 
Published: June 2006

Abstract
Surface-diffusion data in a gaseous adsorption system using an octadecylsilyl-silica gel as an adsorbent were analyzed according to a restricted Knudsen diffusion model. A linear correlation was confirmed between the ratio of the restriction energy for Knudsen diffusion to the isosteric heat of adsorption, Qst, and 1/(−Qst). It was proved that a linear correlation could be observed under the conditions that a linear free-energy relation and an enthalpy–entropy compensation in adsorption equilibrium were established. An estimation procedure of the surface-diffusion coefficient (Ds) was proposed based on the results. It was demonstrated that Ds of various adsorbates at given temperatures could be estimated with an error of less than about 50% from only one datum of the adsorption equilibrium constant measured at a different temperature. Similarly, Ds in gas-phase adsorption could be estimated from the evaporative energy of the adsorbates without experimental data.
Raman Spectral Studies of Aqueous Strontium Nitrate Solution Up to 450 °C and 40 MPa
Authors: Ikushima Yutaka , Hatakeda Kiyotaka , Saito Norio , Arai Masahiko 
Published: June 2006

Abstract
We have studied the structure of aqueous strontium nitrate solution (2.8 M) at temperatures up to 450 °C and pressures of 22.6, 30.0, and 40.0 MPa using Raman spectroscopy technique. The strontium ion forms two species; one is the bound species in contact more strongly with the NO3− like the monovalent cation, and the other is the free species separated from the NO3−. The relative ratio of the bound species to the free ones remains unaltered with an increase in temperature up to 375 °C; above this temperature, however, the ratio significantly increases. The half-width at half peak height (hwhh) for the bound species is larger than that for the free species; it increases at 375 °C or above, suggesting that the bound species relaxes faster than does the free species. The relaxation for the bound species becomes significantly faster at the critical temperature. The number of water molecules of hydration around Sr2+, nH2O, is estimated by the comparison of Raman intensity and previous XAFS data. As the temperature increases, the nH2O gradually decreases. The value shows a remarkable decrease above 370 °C, indicating the displacement of water molecules from the solvation shell around Sr2+ and the concomitant entry of NO3− into the shell at higher temperatures.
The Structural Stability of Seven-Coordinate Divalent Cations in the First Transition Series Relevant to the Water-Exchange Reaction Mechanism
Authors: Tsutsui Yuko , Wasada Hiroaki , Funahashi Shigenobu 
Published: June 2006

Abstract
We studied the structural stability of heptahydrated divalent cations in the first transition series as model intermediary species in associative reaction pathways for the water exchange of hexahydrated cations by ab initio molecular-orbital methods. All of the structures of heptacoordination are pentagonal bipyramidal with a distorted equatorial plane. The structural stabilities are strongly dependent on their d-electron configurations. An associative mechanism is possible for the water-exchange reactions of hexahydrated divalent cations having less than seven d electrons, because the seven-coordinate species are located at the local minima or at the saddle points on the potential-energy surface. The occupation of the antibonding b orbital induces a transition density corresponding to an antisymmetric distortion through an interaction with a low-lying 4s orbital. The large bonding interaction makes the heptahydrated manganese(II) ion to become located at a local minimum. The occupancy of antibonding a orbitals determines the pattern of the antibonding interaction. Hexahydrated divalent cations with d3, d6, and d7 configurations (vanadium(II), iron(II), and cobalt(II)) prefer a cis attack, while chromium(II) with a d4 configuration prefers a trans attack during the operative associative process of the water-exchange reaction.