bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Conformational Analysis of 6,10-Diethyl[1,2,3]trithiolo- [4,5-h]benzopentathiepin Monoxides: Isolation and Optical Properties of Chiral Benzopentathiepin Derivatives
Authors: Kimura Takeshi , Hanzawa Masayuki , Tsujimura Kazuhiko , Takahashi Tatsuya , Kawai Yasushi , Horn Ernst , Fujii Takayoshi , Ogawa Satoshi , Sato Ryu 
Published: September 2002

Abstract
6,10-Diethyl[1,2,3]trithiolo[4,5-h]benzopentathiepin (1) was oxidized by mCPBA in dichloromethane to produce the corresponding four monoxides. The structures of the monoxides 2, 3, 4, and 5 were determined by X-ray crystallography to be 6,10-diethyl[1,2,3]trithiolo[4,5-h]benzopentathiepin 8-oxides (1,2,3-trithiole 2-oxides) for 2 and 3, and 6,10-diethyl[1,2,3]trithiolo[4,5-h]benzopentathiepin 7-oxides (1,2,3-trithiole 1-oxides) for 4 and 5, respectively. Compounds 2 and 3 are isomers with respect to the conformation of the 1,2,3,4,5-pentathiepin ring, and 4 and 5 are also the conformational isomers. These compound pair members, 2 and 3, and 4 and 5, were found to isomerize each other by inversion of the pentathiepin ring. The activation parameters of the isomerization, ΔG298≠, ΔH≠, and ΔS≠, were determined by 1H NMR spectroscopy. Because of the slow inversion of the pentathiepin ring, isolation of unsymmetrically substituted benzopentathiepin as a chiral molecule is possible. Asymmetric oxidation of 1 was performed by a Sharpless reagent [1/Ti(OiPr)4/R,R-DET/t-BuOOH = 1 : 2 : 4 : 4] to produce optically active monoxides 4a and 5a. The configuration of 4a and 5a was confirmed as R configuration on the sulfinyl sulfur atom, respectively. The specific rotation and the circular dichroism spectra of 4a and 5a were measured in chloroform; such data are apparently affected by the conformation of the pentathiepin ring.
Rhodium- and Ruthenium-Catalyzed Dehydrogenative Borylation of Vinylarenes with Pinacolborane: Stereoselective Synthesis of Vinylboronates
Authors: Murata Miki , Kawakita Koji , Asana Taichi , Watanabe Shinji , Masuda Yuzuru 
Published: September 2002

Abstract
The treatment of pinacolborane (4,4,5,5-tetramethyl-1,3,2-dioxaborolane) with vinylarenes in the presence of a catalytic amount of phosphine-free di-μ-chlorobis(1,5-cyclooctadiene)dirhodium(I) [RhCl(cod)]2, through dehydrogenative borylation, provides the corresponding regio- and stereodefined (E)-2-arylethenylboronates in high yields. Also, a ruthenium complex prepared in situ from (1,5-cyclooctadiene)(1,3,5-cyclooctatriene)ruthenium(0) [Ru(cod)(cot)] and P(4-CF3C6H4)3 showed considerable catalytic activity for dehydrogenative borylation.
Conformational Study of Isobutenylene Chains in Tandem Claisen Rearrangement Products. Insights from X-ray Crystallography and 1H NMR for Salicylideneaniline Derivatives
Authors: Houjou Hirohiko , Tsuzuki Seiji , Nagawa Yoshinobu , Hiratani Kazuhisa 
Published: September 2002

Abstract
A new variety of salicylideneaniline derivatives were prepared from a substituted aniline and a bis(hydroxybenzaldehyde) which has been synthesized through a tandem Claisen rearrangement reaction. X-ray crystal structures were obtained for many of the products. With respect to the conformation of their isobutenylene chain, the crystal structures can be classified into three groups: i.e., skew–skew (I), syn–skew (II), and syn–syn (III) conformers. The 1H NMR spectra were significantly different among these compounds, especially for the isobutenylene moiety. The set of the chemical shifts, (δ (Ha), δ (Hb)), of exo-methylene (Ha) and benzylic methylene (Hb) is a good index for classifying the NMR spectra, and these values also reflect the conformation of the isobutenylene chain found in the crystal state. Namely, each conformer of I, II, and III corresponds to the (δ (Ha), δ (Hb)) values (ppm) around (5.10, 3.43), (4.86, 3.43), and (4.74, 3.56), respectively. This result is verified by the complexation study of a 15-crown-5 derivative with alkali metal ions. The chemical shift change caused by the complexation is successfully explained by the conformation changes among I, II, and III.
Radical Addition of α-Halo Ester to Homoallylic Gallium or Indium Species: Formation of Cyclopropane Derivatives
Authors: Usugi Shin-ichi , Tsuritani Takayuki , Yorimitsu Hideki , Shinokubo Hiroshi , Oshima Koichiro 
Published: September 2002

Abstract
Treatment of benzyl bromoacetate with 3-butenylgallium dichloride in ether in the presence of a catalytic amount of Et3B as a radical initiator provided benzyl 3-cyclopropylpropanoate in 64% yield via a radical addition–substitution sequence. The use of 3-butenylindium dichloride in place of the gallium reagent also afforded the same product in good yield.
Synthetic Studies on Ceratospongamides, Cyclic Heptapeptides Containing Thiazole and Oxazoline Units: Total Synthesis of cis,cis-Ceratospongamide
Authors: Kutsumura Noriki , Sata Noriko U , Nishiyama Shigeru 
Published: September 2002

Abstract
A total synthesis of cis,cis-ceratospongamide 1a, a cycloheptapeptide isolated from the Indonesian red alga Ceratodictyon spongiosum and the symbiotic sponge Sigmadocia symbiotica, was accomplished. The heptapeptide chain 8 was produced by a stepwise connection of the following segments: (L-Phe-L-Pro)-thiazole residue, L-Phe-L-Pro-OMe, and L-Ile-L-aThr-OMe. Macrolactamization of 8, followed by cyclization to an oxazoline ring, provided cis,cis-ceratospongamide 1a along with its diastereomer 1c, which was different from the reported trans,trans-ceratospongamide 1b. The structural determination of 1c and its conversion to 1a were successfully achieved.
Collision Energy Dependence Measurement of the Total De-excitation and the CF3* Chemiluminescence Cross Sections in the Ar(3P) Reaction with CF3H
Authors: Kawaguchi Hisashi , Ohoyama Hiroshi , Kasai Toshio 
Published: September 2002

Abstract
The collision energy dependences of the total de-excitation and the CF3* chemiluminescence cross sections were measured in the reaction of Ar(3P) with CF3H using conventional and cross-correlation TOF methods. In the latter method, which is favorable for detecting weak signals, we employed a pseudorandom pulse discharge to generate a metastable argon beam. The collision energy dependence for the CF3* chemiluminescence channel gives a positive slope as a function of the collision energy with a threshold of 0.10 eV. The collision energy dependence of the total de-excitation in the entrance channel, on the other hand, shows a steep decrease as a function of collision energy without any threshold. These results provide insight into the detailed dynamics at crossing points of the potential energy surfaces.
Efficient and Selective Trimerization of Aryl and Alkyl Isocyanates Catalyzed by Sodium p-Toluenesulfinate in the Presence of TBAI in a Solvent-Free Condition
Authors: Moghaddam Firouz Matloubi , Dekamin Mohammad G , Khajavi Mohammad S , Jalili Seifollah 
Published: September 2002

Abstract
Aryl and alkyl isocyanates have been efficiently converted into symmetrical trisubstituted aryl and alkyl isocyanurates, catalyzed by sodium p-toluenesulfinate on its own or in the presence of tetrabutylammonium iodide (TBAI), in a solvent-free condition. The latter has been shown to have a higher catalytic activity.
Triethylborane-Induced Radical Reactions in Ionic Liquids
Authors: Yorimitsu Hideki , Oshima Koichiro 
Published: September 2002

Abstract
Some triethylborane-induced radical reactions were found to proceed in ionic liquids. The reactions include atom transfer radical cyclization, hydrostannylation of alkyne, and atom transfer radical addition. Benzyl bromoacetate participated in the bromine atom transfer addition reaction to 1-octene in 1-ethyl-3-methylimidazolium tetrafluoroborate to afford the corresponding adduct in excellent yield. The facile bromine atom transfer addition in the ionic liquid indicates that the ionic liquid may have a highly polar nature. The ionic liquid used was recyclable in one case, but was not in the other case.
Flame-Induced Addition of Urea to Unsaturated Carboxylic Acids
Authors: Terasaki Masanori , Nomoto Shinya , Mita Hajime , Shimoyama Akira 
Published: September 2002

Abstract
When a hydrogen-oxygen flame was blown against an aqueous solution of urea and maleic acid, N-carbamoylaspartic acid was generated. This compound seemed to be formed by the addition of an amidinoxyl radical to a C–C double bond of the acid, followed by a thermal rearrangement of an amidinoxy to a ureido group.
The Facile Oxidative Coupling of a Hindered Phenol, 2,6-Di-t-butylphenol, Driven by N,N′-Bis(ethoxycarbonyl)-1,4-benzoquinone Diimine; The Reaction Pattern Traced by 1H NMR Spectroscopy
Authors: Miyagi Yo , Banjyo Noriko , Yamamura Emiko 
Published: September 2002

Abstract
Good yields of 3,3′,5,5′-tetra-t-butyl-4,4′-diphenoquinone were obtained by the reaction of 2,6-di-t-butylphenol with N,N′-bis(ethoxycarbonyl)-1,4-benzoquinone diimine, which had been shown to undergo addition with aniline derivatives and phenols. The reaction was followed with 1H NMR spectroscopy to deduce the reaction intermediates.
Organization of Amphiphiles, Part 1: Evidence in Favor of Pre-micellar Aggregates through Fluorescence Spectroscopy
Authors: Sahoo Lingaraj , Sarangi Jitendra , Misra Pramila K 
Published: September 2002

Abstract
The advantage of a change in the vibrational structure of the emission spectra of pyrene as a function of the concentration of a series of polyoxyethylated alkyl ethers and alkylsulfonates has been utilized to explore the co-operative association of ionic and nonionic amphiphiles into micelles, the micropolarity of these micelles and the solubilization site of pyrene in micelles. The results indicate that the micropolarity of the environment experienced by pyrene is alcohol-like. Pyrene preferably resides in the palisade layer of a nonionic micelle, while in the interior of an anionic micelle. A multiple equilibrium model for micelle formation has been suggested and the existence of pre-micellar aggregates has been evidenced from the excimer characteristics of pyrene.
LB Deposition of a Stearic Acid Multilayer without Heavy Metals
Authors: Hayashi Shujiro , Yokogawa Yoshiyuki , Kinoshita Takatoshi 
Published: September 2002

Abstract
LB films consisting of stearic acid (SA) multilayers and silicon substrates without heavy metal were prepared using a computer-controlled LB film deposition apparatus. Using dimethyldioctadecylammonium bromide as the first (or first and second) monolayer(s), up to 70 layers were deposited, and the interference color was expressed. This indicated that the surface charge of the substrate needed to be canceled in order to successfully deposit a multilayer. Moreover, it was demonstrated that LB multilayers of fatty acid could be prepared using a computer-controlled apparatus even without using a heavy metal salt.
Degradation of Mixed Char of Poly(vinyl chloride) with Polyethylene Glycol to Give Hydrocarbons by the Reaction with Potassium Carbonate in Supercritical Water: Formation of Hydrocarbons Containing Lower Amounts of Benzene Accompanied by Formation of Water Soluble Potassium Salts of Carbon Oxides
Authors: Akiyama Fuminori 
Published: September 2002

Abstract
Degradation of char from poly(vinyl chloride) (PVC) or chars from mixtures of PVC and polyethylene glycol (PEG) with potassium carbonate in supercritical water was performed. Degradation of chars from a mixture of PVC and PEG prepared by heating at 250 °C in nitrogen atmosphere with potassium carbonate at 500 °C for 3 h in supercritical water gave a mixture of hydrocarbons in the yield of 11 wt%, in which the content of benzene was only 5%, accompanied by formation of oil in the yield of 16 wt%. The main reaction products in this degradation reaction were water soluble products. The facts that these water-soluble products did not any absorption in 1H NMR and 13C NMR spectra and that these water-soluble products show FT-IR absorptions at 1378 and 1622 cm-1 suggest that these water soluble products are potassium salts of carbon oxides.
Accelerated Corrosion of Stainless Steels with the Presence of Molten Carbonates below 923 K
Authors: Ota Ken-ichiro , Toda Katsuya , Mitsushima Shigenori , Kamiya Nobuyuki 
Published: September 2002

Abstract
The high-temperature corrosion of stainless steels (SUS316L and SUS310S) in the presence of lithium-potassium eutectic carbonate and lithium-sodium eutectic carbonate has been studied by thermogravimetry and the metal consumption method under a carbon dioxide–oxygen atmosphere in the temperature range of 773–1123 K. Although the corrosion of SUS310S obeyed the parabolic rate law for all reaction conditions, the corrosion of SUS316L significantly depended on the reaction conditions. At or above 923 K, the corrosion of SUS316L obeyed the parabolic rate law, even with a carbonate coating. The corrosion rates were accelerated during the initial period of corrosion tests below 923 K, especially around 823 K with a lithium-sodium carbonates coating. The initial accelerated corrosion was a local corrosion, which produced through holes in the metal specimens, and occurred more clearly at higher carbon dioxide partial pressures with the lithium-sodium carbonate coating than with the lithium-potassium carbonate coating.
Physical Chemistry of the Lowest Excited Singlet State of trans-Stilbene in Solution as Studied by Time-Resolved Raman Spectroscopy
Authors: Hamaguchi Hiro-o , Iwata Koichi 
Published: September 2002

Abstract
Structure and dynamics of the lowest excited singlet state of trans-stilbene (the S1 state of tSB) in solution are discussed with an emphasis placed on the elucidation of the mechanism of the trans–cis photoisomerization. Structure of S1 tSB in solution is first discussed based on the time-resolved Raman spectral data and their isotope substitution effects. Original data for an asymmetrically deuteriated tSB, tSB-d5, are presented to confirm the ethylene-like structure of the central C–C linkage of S1 tSB. Next, the time-, temperature-, and solvent-dependent band shape changes of the olefinic C=C stretch band are discussed in terms of the solvent induced dynamic polarization. It is shown that the dynamic polarization model accounts very well, not only for the observed band shape changes, but also for their relevance to the isomerization mechanism. A new microscopic view on the photoisomerization of tSB is thus presented. Picosecond energy dissipation process of S1 tSB is then discussed in relation to the microscopic solvation structure in chloroform. Finally, the mechanism of a new bimolecular reaction between S1 tSB and carbon tetrachloride is discussed on the basis of the diffusion-controlled reaction model.
A Novel Tyrosine Derivative to Study Non-Covalent Assembly Involving C–H···O Hydrogen Bonding
Authors: Satheeshkumar K S , Padma Malar E J , Jayakumar R 
Published: September 2002

Abstract
A novel tyrosine derivative, 3-N-tosyl-4-p-tosyloxybenzyl oxazolidin-4-one (TTBO), C24H23NO7S2, was synthesized. It shows high affinity to chloroform in a ratio of 1 : 1 as evidenced by spectroscopic studies. Ab initio 3-21G*//PM3 calculations indicate that the C–H···O hydrogen bond with a strength of up to 5.9 kcal/mol may be responsible for the non-covalent assembly.
Applications of Ultrafast Transient Infrared Spectroscopies
Authors: Heimer Todd A , Heilweil Edwin J 
Published: September 2002

Abstract
Broadband femtosecond and longer timescale mid-infrared and far-infrared (THz) probing techniques being explored at NIST using multi-element, mid-infrared focal plane arrays and solid-state THz generators/detectors are presented. Ultrafast infrared pulse generation, detection and pump-probe spectroscopy schemes are first reviewed in detail. These methods are used to examine transitory vibrational, chemical and electron transfer phenomena amenable to time-resolved infrared spectroscopy. Direct monitoring of electron transfer rates (&gt; 5×1012 s) from dye sensitizers ([Ru(dceb)(bpy)2]+2 and Ru(dcb)2(NCS)2 derivatives) anchored to semiconductor solar-cell substrates (nanoparticle TiO2, ZrO2 and SnO2 films) is accomplished by measuring increased mid-IR absorption originating from C=O groups and injected electrons in the substrate. Coherent control of CO-stretching vibrational overtone population distributions in liquid-phase metal-hexacarbonyl systems using deliberately chirped mid-IR excitation pulses has also been explored. Identification of molecular steric and diffusional properties involved in internal ring-closing reaction dynamics of ultraviolet (UV) photo-dissociated (RCp)Mn(CO)3 systems in n-hexane will be presented. Terahertz spectroscopic methods and pulsed THz spectra of calf-thymus DNA, proteins and model dipeptides are also presented and their potential use for extracting bio-molecular functional dynamics discussed.
Femtosecond Mid-Infrared Pump–Probe Study of Wave Packet Motion in a Medium-Strong Intramolecular Hydrogen Bond
Authors: Madsen Dorte , Stenger Jens , Dreyer Jens , Hamm Peter , Nibbering Erik T J , Elsaesser Thomas 
Published: September 2002

Abstract
We inspect the O–H stretching vibration of the medium-strong hydrogen bond in phthalic acid monomethyl ester in nonpolar solution by use of single-colour spectrally integrated femtosecond mid-infrared spectroscopy. We derive amplitude and phase characteristics of the coherent modulations of the pump-probe signals as a function of excitation wavelength. We exclude the role of Fermi resonances in the oscillatory contribution to the pump–probe signals. The observed periodic feature is due to wave packet motion of an underdamped out-of-plane 100 cm-1 mode that modulates the hydrogen bond distance. This low-frequency mode anharmonically coupled to the O–H stretching vibration is impulsively excited by the ultrashort mid-infrared pump pulse.
Thiolato-Ligand Substitution Reaction with Halide Ions of Five-Coordinate Trigonal-Bipyramidal Palladium(II) Complexes with Tris(2-(diphenylphosphino)ethyl)phosphine. Electronic and Steric Effects on the Reaction Mechanism
Authors: Aizawa Sen-ichi , Iida Takashi , Sone Yasushi , Kawamoto Tatsuya , Funahashi Shigenobu , Yamada Shinkichi , Nakamura Motoshi 
Published: September 2002

Abstract
Mononuclear and dinuclear thiolato complexes with five-coordinate trigonal-bipyramidal palladium(II), [Pd(pt or tt)(pp3)](BF4) and [Pd2(pdt)(pp3)2](BF4)2 (pp3 = tris(2-(diphenylphosphino)ethyl)phosphine, pt = 1-propanethiolate, tt = α-toluenethiolate, pdt = 1,3-propanedithiolate) have been synthesized. The solid-state structure of the dinuclear pdt complex was confirmed by an X-ray crystal structure analysis and the structures of the pt, tt, and pdt complexes in solution were characterized by 31P NMR spectroscopy. It is indicated from the 31P NMR chemical shifts of the bound pp3 ligand that the axially coordinated thiolato ligands are strong σ and π donors compared with the halo ligands in the axial position of the corresponding trigonal-bipyramidal palladium(II) complexes, [PdX(pp3)]+ (X- = Cl-, Br-, I-). The kinetic parameters for the one-step and successive two-step thiolato-ligand substitution reactions with halide ions in chloroform were obtained for the mononuclear and dinuclear complexes, respectively. These results have revealed that the reaction mechanism of the present thiolato-ligand substitutions is much more dissociative than that of the corresponding halo-ligand substitutions using trimethyl phosphite as the entering ligand, and that the reaction mechanism of the two-step substitution of the dinuclear thiolato complex is more dissociative than that of the mononuclear complexes. It has been concluded that the reaction mechanism of the five-coordinate trigonal-bipyramidal palladium(II) complexes with the 18-electron ground state is quite sensitive to the electronic properties of the entering and leaving ligands and the steric environment of the reaction site compared with that of four-coordinate square-planar palladium(II) complexes with the 16-electron ground state, which is generally associatively activated.
Slowing Down of Vibrational and Structural Relaxation of Water Molecules in Concentrated Aqueous NaCl Solutions
Authors: Laenen Robert , Thaller Andy 
Published: September 2002

Abstract
Sub-picosecond IR-spectroscopy is applied to aqueous NaCl solutions with low concentrated HDO–molecules acting as local probes for the strength of the H-bonds. We find a notable lengthening of the OH-lifetime by the presence of the dissolved ions by a factor of almost 3 up to 2.7 ps at 273 K in comparison to neat water. Simultaneously the average reorientation of the OH–dipoles slows down to 11 ps (273 K) and 4 ps (343 K) while also structural relaxation is found to proceed slower as compared to the case of neat water.
Time Resolved Spectroscopy of Water in the Infrared: New Data and Discussion
Authors: Laenen Robert , Simeonidis Konstantinos , Laubereau Alfred 
Published: September 2002

Abstract
We demonstrate sub-picosecond spectroscopy of an isotopic water mixture presenting strong evidence for four major spectral components within the OH-band of HDO in the solvent D2O peaked at approximately 3330 cm-1 (I), 3390 cm-1 (II), 3460 cm-1 (III), and 3520 cm-1 (IV). Species I and IV are. proposed to give rise for discrete components with local hexagone and weakly bound structures, respectively. The remaining species are most probably related to combination tones with hydrogen bridge bond vibrations. Furthermore we summarise the findings on the vibrational and spectral dynamics of water as determined by time-resolved IR-spectroscopy of HDO molecules dissolved at low concentration in D2O.
Vibrational Spectra of Dipyrido[3,2-a:2′,3′-c]phenazine and Its Radical Anion Analyzed by Ab Initio Calculations and Deuteration Studies
Authors: Matthewson Benjamin James , Flood Amar , Polson Matthew Ian James , Armstrong Christopher , Phillips David Lee , Gordon Keith Christopher 
Published: September 2002

Abstract
The ligand dipyrido[3,2-a:2′,3′-c]phenazine (dppz) and its deuterated analogues, d4-dppz, d6-dppz, d10-dppz, and [ReCl(CO)3] complexes with these ligands have been synthesized. Using DFT calculations it is possible to calculate a geometry of the ligand such that it matches the crystallographic data for a variety of dppz complexes. B3LYP/6-31G(d) frequency calculations correspond closely to the experimental IR and Raman data. Analysis of the calculated normal modes of vibration reveals the presence of a number of modes that are localized to the ring sections of the dppz-framework. Modes 79, 78, 77, 50, and 49, which lie at 1602, 1586, 1576, 1071, and 1034 cm-1, respectively, in the experimental spectra of dppz correspond to phenanthroline-based modes. Modes 68 and 67, lying at 1414 and 1402 cm-1 in dppz are phenazine-based vibrations. These provide an insight into the nature of the MLCT transitions for metal complexes with dppz. The preferential enhancement of phenanthroline-based modes in the resonance Raman spectra of these complexes strongly suggests the π* accepting MO is of phenanthroline character. DFT calculations (B3LYP/6-31G(d)) on the radical anion reveal the elongation of bonds about the pyrimidine ring. The frequency calculations also reveal significant changes in the vibrational spectra for dppz•- from the neutral ligand. Experimental resonance Raman data for the electrochemically reduced [ReCl(CO)3(dppz)]- and the deuterated analogues show distinct isotope shifts that may be correlated to results obtained from the calculations. The characteristic bands observed in these spectra are phenanthroline-based. They may be correlated with time-resolved resonance Raman spectra of Ru(II) and Re(I) complexes.