bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Molecular Thermometer Based on the Fluorescence of Fullerene Dispersed in Poly(methyl methacrylate) Film
Authors: Amao Yutaka , Okura Ichiro 
Published: September 2002

Abstract
A new optical molecular thermometer based on the fluorescence intensities of the fullerene C60 dispersed in poly(methyl methacrylate) (PMMA) film was developed. The fluorescence intensity of the C60 film decreased with increasing the temperature in the range from 260 to 373 K. The Arrhenius plot of ln[(I(T)/I(Tref))] versus 1/T for the C60 film exhibits considerable linearity supported by the correlation factor, r2, estimated to be 0.989 by the least squares method (Tref = 260 K). The E/R value of the C60 film is estimated to be 22.3 K. These results indicate that the C60 film provides a linear temperature response in the range 260 to 373 K.
Nanoscale Molecular Containers
Authors: Rudkevich Dmitry M 
Published: September 2002

Abstract
Over the last few years, there has been a breakthrough in the design and synthesis of nanoscale molecular containers—cavitands, (hemi)carcerands, and capsules. These nanocavities are designed for selective binding, separation and sensing of smaller molecules and ions, molecular transport and delivery, stabilization of reactive intermediates, and catalysis through encapsulation. They also mimic the hydrophobic pockets of enzymes. The field has grown since the first hollow calixarenes of Collet, Cram, and Gutsche, which were able to trap a single solvent or gas molecule, in the early 1980s, to investigations of giant cavities of 15–20 Å inner dimensions and 1500 Å3 internal volume. This reflects current trends in molecular recognition which are rapidly moving towards nanotechnology and microfabrication on the one hand and molecular biology on the other. Recently prepared nanocavities are ready to be employed for encapsulation of drugs and their active transport/delivery through cell membranes. Cavity-containing informationally rich polymers, sensing materials and polymer-supported microreactors are also in sight. These and many other applications can only be possible if general approaches towards construction of nanoscale molecular containers are developed and if the key rules governing their inclusion complexes are understood at the level of their organic chemistry.
Preparation and Kinetic Stabilization of Highly Strained Paracyclophanes
Authors: Tsuji Takashi , Ohkita Masakazu , Kawai Hidetoshi 
Published: September 2002

Abstract
In this Account we describe the preparation, structures, and properties of the most highly strained paracyclophanes known to date, i.e. [4]- and [1.1]paracyclophanes and their derivatives. The preparation of these cyclophanes has been accomplished through the photochemical valence isomerization of corresponding 1,4-bridged Dewar benzene derivatives. These strained paracyclophanes are prone to polymerize and are not stable enough to isolate: [4]paracyclophane is rapidly consumed even below -100 °C in fluid solution, though it remains intact indefinitely in a frozen organic glass at 77 K, while [1.1]paracyclophane is stable only below -20 °C in solution. By introducing substituents which sterically hinder access to the bridgehead carbon atoms by other reagents, however, one can remarkably stabilize these species kinetically so as to allow the measurement of 1H NMR spectrum of the former and the isolation of the latter as crystals. The 1H NMR spectrum of the [4]paracyclophane strongly support, in conjunction with theoretical calculations, the sustenance of considerable aromaticity despite the extreme bending of its benzene ring. [4]Paracyclophane is so strained that it is thermodynamically less stable than the corresponding Dewar isomer and the thermal conversion of the benzene form to the Dewar form is observed for the first time. A fully unsaturated derivative of [4]paracyclophane is also generated and confirmed to prefer the structure of 1,2,3,4-tetradehydro[4]paracyclophane rather than that of π-bond isomer, bicyclo[4.2.2]deca-1,3,5,7,9-pentaene. The stabilized [1.1]paracyclophane is found to undergo efficient photochemical transformation into a benzene p,p′-dimer structure, from which the former is thermally regenerated upon mild heating. Structural characteristic features of the [1.1]paracyclophane and the benzene p,p′-dimer are revealed by X-ray crystallography. Limits for experimentally accessible strained paracyclophane are also discussed.
Dimerization Effect on the Physical Properties in New One-Dimensional Organic Conductors: (ChTM-TTP)2AuBr2, (ChTM-TTP)2GaCl4, and (ChTM-TTP)ReO4
Authors: Kawamoto Tadashi , Ashizawa Minoru , Mori Takehiko , Yamaura Jun-Ichi , Kato Reizo , Misaki Yohji , Tanaka Kazuyoshi 
Published: September 2002

Abstract
Crystal structure analyses, measurements of transport and magnetic properties, and low-temperature X-ray studies of new organic conductors: (ChTM-TTP)2AuBr2, (ChTM-TTP)2GaCl4, and (ChTM-TTP)ReO4, where ChTM-TTP is 2-[4,5-(1,2-cyclohexylenedithio)-1,3-dithiol-2-ylidene]-5-[4,5-bis (methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, have been carried out. In these compounds, the donors form quasi-one-dimensional columns with dimerization induced by the steric hindrance of the 1,2-cyclohexylene unit. The crystal structures and the energy band structures of both AuBr2- and GaCl4- salts are similar to those of the Bechgaard salts. The electrical resistivity and the thermoelectric power show metallic behavior above 100 K for the AuBr2- salt and above 150 K for the GaCl4- salt. The results of the ESR spin susceptibility, the static magnetic susceptibility, and the low-temperature X-ray studies indicate that the ground states of both salts are antiferromagnetic insulators. The Néel temperatures are about 38 K for the AuBr2- salt and about 32 K for the GaCl4- salt. These salts are the first materials showing an antiferromagnetic state among the TTP series conductors. In (ChTM-TTP)2X (X = Au(CN)2, AuBr2, and GaCl4), the strength of the dimerization is related to the charge localization temperature. For the ReO4- salt, the donor to anion ratio is 1 : 1 in spite of the tetrahedral anion being similar to the GaCl4- anion. Although the interstack interactions are not small, the degree of charge transfer of the donor molecule is +1; thus this salt has an energy gap at the Fermi level, in agreement with the semiconducting transport behavior.
Formation of Palladium Nanoclusters on Y-Zeolite via a Sonochemical Process and Conventional Methods
Authors: Okitsu Kenji , Yue Akihiko , Tanabe Shuji , Matsumoto Hiroshige 
Published: September 2002

Abstract
The preparation of Pd clusters was investigated by the sonochemical reduction of [Pd(NH3)4]2+ complexes on Y-zeolite in an aqueous solution at 20 °C. Through measurements of the UV–vis and X-ray photoelectron spectra, [Pd(NH3)4]2+ was found to be reduced by radicals formed from 2-propanol sonolysis to yield zero-valent Pd. It was confirmed that the binding energy of the Pd 3d core level on the Y-zeolite was shifted to a higher value in comparison with that of Pd bulk metal. The formation of Pd metal, however, could not be observed by TEM and EXAFS measurements, implying the formation of ultrafine Pd clusters. On the other hand, the results of XPS analyses for several standard Pd clusters of ca. 1nm prepared by the conventional thermal treatment indicated that the peak values of the Pd core level increased with decreasing particle size. The maximum difference in binding energy between these samples was 0.6 eV at the Pd 3d5/2 core level. This phenomenon was suggested to be attributed to a quantum size effect corresponding to a splitting of the band structure. In comparison with standard samples, the size of sonochemically formed Pd clusters was roughly estimated to be less than 1 nm and composed of several dozen Pd atoms.
Electric Field Effects on Electron Transfer between H+ and Carbon-Based Electrode Surfaces: A DFT and Anderson–Newns Hamiltonian Analysis Study
Authors: Ohwaki Tsukuru , Murai Takahiko , Yamashita Koichi 
Published: September 2002

Abstract
To investigate the nature of the characteristic properties (especially the wide potential window and the low background current) of boron-doped diamond electrodes, we discuss electric field effects on the electron transfer process between the diamond surface and a proton based on density functional theory (DFT) and Anderson–Newns Hamiltonian analysis. All of the necessary data for this analysis were obtained by a “finite-field DFT method” at the level of B3LYP/6-31G and natural bond orbital analysis (NBO). The diamond and graphite electrode surfaces were modeled by corresponding clusters. We investigated the differences in the electric-field response of the density of states (DOS) peak of the proton 1s orbital and the number of electrons on the proton for the cases of a diamond cluster and a graphite cluster. These differences are attributable to the differences in the overlap between the proton 1s orbital and the surface orbitals. We discuss the relationship between this electric-field effect on the DOS peak, critical points of the Q-&lt;n&gt;curve and two characteristic properties of diamond electrodes, that is, low background currents and wide potential windows.
State-Selected Ion-Molecule Reactions Studied by the Threshold Electron-Secondary Ion Coincidence (TESICO) Technique, Ar+(2P3/2, 2P1/2) + HCl
Authors: Fukuzumi Takahiro , Nakano Ryousuke , Okamura Satoshi , Honma Kenji , Koyano Inosuke 
Published: September 2002

Abstract
The reactions of Ar+ with HCl were studied for the two spin-orbit states of Ar+, 2P3/2 and 2P1/2, by the threshold electron-secondary ion coincidence (TESICO) technique. State selected relative reaction cross sections of the two product channels, hydrogen abstraction (HA) to form ArH+, and charge transfer (CT) to form HCl+, were determined at five collision energies in the range of 0.71–3.5 eV. At low collision energies, the cross sections of both channels show no substantial difference between the two spin-orbit states. At high collision energies, the cross sections for the HA channel also show no difference between the two states, whereas those for the CT channel show significant dependence on the spin-orbit state, the cross sections for Ar+(2P1/2) being always larger than those for Ar+(2P3/2). Combining these results with the coincidence time-of-flight (TOF) spectra, a direct reaction mechanism is suggested for both channels. The importance of the nonadiabatic transitions between the surfaces correlating to the Ar+ + HCl and Ar + HCl+(A2Σ) states in leading the reaction is proposed. Proton transfer follows the nonadiabatic transition for the HA channel and radiative or nonradiative transition follows for the CT channel.
Oxidative Dehydrogenation of Ethylbenzene over Sm2O3–V2O5 System
Authors: Sugunan Sankaran , Renuka Neeroli Kizhakayil 
Published: September 2002

Abstract
Sm2O3/V2O5 catalysts were synthesized by wet impregnation of samaria with an aqueous solution of ammonium trioxovanadate(V). The characterization of the prepared samples was carried out using EDX, XRD, FTIR and TG-DTA as well as a measurement of the surface area and pore volume. The catalysts were found to be stable up to 800 °C. Both amorphous and crystalline vanadate species were detected in the supported system. Vanadia species became anchored to the surface through an interaction with basic hydroxy groups and Lewis acid sites of the surface. Lewis acid and base sites decreased upon vanadia addition along with a concomitant enhancement of Brønsted acid sites. The oxidative dehydrogenation of ethylbenzene was carried out over Sm/V catalysts, which exhibited a styrene selectivity &gt; 80%. The active species present in the supported system was concluded to be amorphous vanadia in tetrahedral coordination. The higher vanadia-loaded systems exhibited constant styrene selectivity, where crystalline tetraoxovanadates were predominantly formed.
Kinetics of Change in Casein Aggregation as a Result of Solvent-Induced Structural Change
Authors: Nishikawa Sadakatsu , Huang Hua , Matsumoto Chiho , Katayama Mizuho , Robinson Brian H 
Published: September 2002

Abstract
The stopped-flow method has been applied to a kinetic study concerning structural changes in casein aggregates in an aqueous medium. The aggregation process has been followed in aqueous solutions of α-casein, the results of which have revealed the same rate parameters as those reported previously in a mixed protein system (sodium casein). It has been found that the additions of urea and 1-propanol to aqueous solutions of sodium casein lead to a breakdown of the casein aggregates, which is monitored by the decrease in the absorbance (turbidity) of the sample. From the concentration dependence of the apparent first-order rate constant and the amplitude of the reaction, it is proposed that the rate-determining step is the departure of a single molecule (monomer) or a small aggregate from a large aggregate. The apparent first-order rate constant is 37 s-1 in the presence of 1-propanol and 0.26 s-1 for urea. Furthermore, in a mixing experiment with 1-propanol, an additional process associated with structural changes in the aggregate has been observed at longer times (monitored by an increase of absorbance), the apparent first-order rate constant being about 0.03 s-1. It is inferred that an intermediate is observed between the process of the breakdown of the aggregate which is quite stable in the presence of CaCl2, and that of the formation of another stable aggregate, which may include 1-propanol.
Linear and Nonlinear Polarizabilities of Fragmental Molecules for the Phenylacetylene Dendrimers
Authors: Nomura Yasushi , Sugishita Takashi , Narita Susumu , Shibuya Tai-ichi 
Published: September 2002

Abstract
Linear and nonlinear polarizabilities of small fragmental molecules for the phenylacetylene dendrimers have been calculated with the frequency-dependent moment schemes based on the sum-over-states expressions of the polarizabilities, including all of the singly-excited configurations in the semiempirical CNDO/S approximation. The smallest system, consisting of two benzene rings connected by an acetylene chain, corresponds to a molecular unit that is usually adopted in the exciton model for a theoretical analysis of the phenylacetylene dendrimers. The dependences of the polarizabilities upon the molecular size were examined. It has been shown that the linear polarizability in the static-field condition increases linearly with the number of acetylene chains (N). MO calculations of the nonlinear polarizabilities of these molecules have been carried out for the first time. The third-order polarizability in the static-field condition is shown to depend quadratically upon N, which suggests that two chromophores at a time participate in the optical process of the third-order polarization.
Toroidal Graphenes from 4-Valent Tori
Authors: Diudea Mircea V 
Published: September 2002

Abstract
Square tori are transformed into hexagonal and other tiling tori by several cutting procedures. The toroidal objects thus generated are optimized by a molecular mechanics procedure. The strain energy, defined as the difference between the energy of toroidal structure and the energy of its corresponding straight, open tube, is shown to decrease as the torus diameter increases, in the series 10,n of polyhex tori, up to 5000 atoms. Graph-theoretical characterization of toroidal structures including the Hosoya polynomial, Distance Degree Sequence, and Wiener index is also given.
Absolute Rate Constants of Cr2 (X 1Σg+) with O2, NH3, and C2H4 in the Gas Phase at Room Temperature
Authors: Ishikawa Yo-ichi , Ogawa Hiroshi , Iwaki Takayuki 
Published: September 2002

Abstract
The gas-phase reactivities of ground-state chromium dimers (Cr2 (X 1Σg+)) for three small molecules (O2, NH3, and C2H4) were investigated in a mass-flow controlled cell. The transient concentration of Cr2 (X 1Σg+, v = 0) produced by pulsed 266-nm laser photolysis of [Cr(CO)6] was monitored by a time-resolved laser-induced fluorescence (LIF) at 459.67 nm (A 1Σu+, v′′ = 0 ← X 1Σg+, v′ = 0). The pseudo-first-order decay rates of Cr2 (X 1Σg+) were observed to increase linearly with increasing O2 and NH3 pressure, giving pseudo-second-order rate constants of (2.3 ± 0.3)×10-11 cm3 molecule-1 s-1 for Cr2 + O2 and (4.3 ± 0.8)×10-13 cm3 molecule-1 s-1 for Cr2 + NH3 under 6.0-Torr total pressure with Ar buffer gas at room temperature. On the other hand, C2H4 was apparently found not to react with Cr2 (X 1Σg+) under our experimental conditions. In the Cr2 + O2 reaction, the pseudo-second-order rate constants were found to depend on the total pressure, and the limiting low-pressure rate constant was estimated to be (5.9 ± 2.5)×10-28 cm6 molecule-2 s-1.
Amperometric Sensor for Glutathione Based on a Mechanically Immobilized Cobalt Hexacyanoferrate Modified Electrode
Authors: Ravi Shankaran Dhesingh , Sriman Narayanan Sangilimuthu 
Published: September 2002

Abstract
A mechanically immobilized cobalt hexacyanoferrate modified electrode has been constructed. The modified electrode exhibits two reversible redox peaks in a 0.1 M NaCl medium, and can be used for the amperometric determination of glutathione. The modified electrode facilitates the catalytic oxidation of glutathione at a reduced overpotential compared with an unmodified graphite electrode. Glutathione was determined in the range of 4 × 10-5 to 5.2 × 10-4 M in 0.1 M NaCl and in 0.1 M KCl with correlation coefficients of 0.9991 and 0.9992, respectively. Relative standard deviations of 2.88% in NaCl and 3.27% in KCl were obtained for 4 × 10-4 M GSH (n = 10). The sensor exhibited excellent stability, reproducibility and immediate response, and can be used in flow-injection analysis.
Study on Estimating the Contribution to the Transfer Free Energies of Complex Ions. Part II. [Fe(CN)2n(bpy)(3-n)](2-2n)+ from Water to a Water–Ethanol Mixed Solvent
Authors: Tarui Takao 
Published: September 2002

Abstract
The solubilities of [Fe(bpy)3](ClO4)2, [Fe(CN)2(bpy)2], and K2[Fe(CN)4(bpy)] in ethanl–water mixed solvents were measured at 25.0 ± 0.1 °C, and the transfer free energy of each complex from water to a water–ethanol mixed solvent was calculated. From the obtained data, the transfer free energies were split into contributions from 2,2′-bipyridine-solvent, cyano ligand-solvent interaction energies, and electrostatic energies. The ratios of the contributed energy from 2,2′-bipyridine vs transfer free energy of free(non-coordinated) 2,2′-bipyridine are almost constant at about 0.6–0.75 over the whole mole fraction range; this is similar to the case of 1,10-phenanthroline, although 2,2′-bipyridine has a single bond between two pyridine rings and the configuration of non-coordinated 2,2′-bipyridine differs markedly as compared with that of the coordinated one. The contributed energy from the cyano ligand in this work is somewhat smaller than that estimated from an iron(II)–cyano-1,10-phenanthroline mixed-ligand complex system; it is considered that the weaker selective solvation of 2,2′-bipyridine than 1,10-phenanthroline affects the contribution from the neighbouring cyano ligand. That the contribution from the electrostatic energy does not agree with the expected value from the Born equation, is attributed to the difference between the local and bulk dielectric constants resulting from the strong selective solvation of 2,2′-bipyridine by ethanol, where ε and ε w represent the dielectric constant of a mixed solvent and water, respectively.
Characterization of Dimeric (Carboxylato)copper(II) Complexes by Electron Spin Resonance Spectra. Correlation of ESR Parameters with Singlet–Triplet Energy Separations
Authors: Muto Yoneichiro , Nakashima Michio , Tokii Tadashi , Suzuki Ikuo , Ohba Shigeru , Steward Omar W , Kato Michinobu 
Published: September 2002

Abstract
Linear correlations with positive slopes have been found for the zero-field splitting parameters (D) and the anisotropic exchange parameters (Dex) vs the singlet–triplet separations (-2J) for [Cu2(O2CR)4(L)2] (R = F3C, FCH2, Cl3C, ClCH2, CH3, H, and C6H5CO) for a wide range of -2J values, ca. 240–650 cm-1. The values of D and Dex for benzoylformate were found to be the highest ever studied. The quality of the linear relations of -2J, Dex and D with the square of the coefficient of 2px(C) of the symmetric HOMO of the bridging carboxylate ions, coeff,2 were found to be in the order, -2J vs coeff2 &gt; Dex vs coeff2 &gt; D vs coeff2. A roughly linear relationship with a negative slope was found for D vs -2J for a system, [Cu2(O2CCMenPh3-n)4(L)2], in which the -2J values cover a relatively small range, ca. 320–370 cm-1.
The Aggregation of Dichlorobis(N-hexylethylenediamine)zinc(II) in Water and Water/Chloroform Mixed Solvents
Authors: Iida Masayasu , Asayama Keiko , Ohkawa Shiho 
Published: September 2002

Abstract
The aggregation of a surfactant metal complex, dichlorobis(N-hexylethylenediamine)zinc(II) (= [ZnCl2(hex-en)2]), was studied in such solvents as water, methanol (or water–methanol mixed), and chloroform (or water-containing chloroform). This complex was readily dissolved in water to form aggregates extensively, and was also very soluble in water-containing chloroform to give reversed-type aggregates. In dilute aqueous solutions, the complex was hydrolyzed and precipitated, while the solution was stable at concentrations above 0.25 mol kg-1 where the complex aggregates considerably. Precipitation was prevented by the addition of NaCl; this effect can be attributed to chloride-ion binding. The aggregation behavior in solutions was investigated by measuring the self-diffusion coefficients for the complex and of the vapor pressure depressions. The degrees of aggregation of the aqueous and water-containing chloroform solutions were in a similar manner at higher concentrations, although the critical concentration for aggregation in the aqueous solution was considerably smaller than in the chloroform solution. The hydration mode of this surfactant complex is discussed in comparison to the D2O longitudinal relaxations between the aqueous solutions and the water-containing chloroform solutions.
Synthesis and UV/Vis Absorption Spectra of Novel Azo Dyes Derived from Polyfluoro- and Perfluoroazobenzenes
Authors: Matsui Masaki , Funabiki Kazumasa , Shibata Katsuyoshi 
Published: September 2002

Abstract
Novel mono- and intermolecularly substituted, cyclized, and disazo dyes have been synthesized by the reaction of 4′-dimethylamino-2,3,4,5,6-pentafluoroazobenzene and perfluoroazobenzene with bifunctional heteroatom nucleophiles, such as 1,2-benzenedithiol, 2-aminobenzenethiol, 2-aminophenol, 1,2-ethanedithiol, ethylenediamine, and 2-aminoethanol. The kinds of bifunctional nucleophiles and the reaction conditions drastically affected the distribution of the product. The absorption maxima and the molar absorption coefficients of these dyes were observed in the range of 323–485 nm and 15000–60000 dm mol-1 cm-1, respectively.
Syntheses of Twelve-Membered Ring Titana- and Zirconasiloxane Compounds and Their Properties as Ceramic Precursor
Authors: Gunji Takahiro , Kubota Ken-ichi , Kishiki Shin-ichiro , Abe Yoshimoto 
Published: September 2002

Abstract
Cyclic metallasiloxanes, [(SiR1R2O)2M(acac)2O]2 (R1 = Me, R2 = OBut; R1 = R2 = OBut; R1 = OPri, R2 = OBut; M = Ti, Zr), were synthesized by the reaction of disiloxane-1,3-diols with diisopropoxidobis(2,4-pentanedionato)titanium(IV) or diisopropoxidobis(2,4-pentanedionato)zirconium(IV) in tetrahydrofuran. Cyclic titanasiloxanes and zirconasiloxanes have twelve-membered rings with the (Si–O–Si–O–Ti–O)2 linkages and (Si–O–Si–O–Zr–O)2 linkages, respectively. The pyrolysis of cyclic titanasiloxanes and zirconasiloxanes provided 2SiO2–TiO2 and 2SiO2–ZrO2 ceramics, respectively, which consist of amorphous silica and crystallized titania or zirconia.