bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis, Crystal Structures, and Some Properties of S-Bridged Pt(II)-M(III) (M = Co, Rh) Dinuclear Complexes with Square-Planar and Octahedral Geometries
Authors: Yamada Yasunori , Uchida Mamoru , Miyashita Yoshitaro , Fujisawa Kiyoshi , Konno Takumi , Okamoto Ken-ichi
Published: September 2002

A novel dinuclear complex [{Pt(bpy)}{Co(aet)2(en)}]3+ (bpy = 2,2′-bipyridine; aet = 2-aminoethanethiolate; en = ethylenediamine) (1) composed of square-planar and octahedral geometries was obtained by a substitution reaction of [Ni{Co(aet)2(en)}2]4+ with [PtCl2(bpy)]. The reactions of fac(S)-[M(aet)3] (M = CoIII, RhIII) with [PtCl2(bpy)] also gave a similar type of S-bridged dinuclear complexes [{Pt(bpy)}{M(aet)3}]2+ (M = CoIII (2), RhIII (3)). The crystal structures of complexes 1, 2, and 3 were determined by X-ray crystallography. All of the Co and Rh atoms in 1, 2, and 3 take approximately octahedral geometry. The Pt atoms in 1, 2, and 3 are coordinated by two N atoms in bpy and two S atoms from C2-cis(S)-[Co(aet)2(en)]+ or [M(aet)3] unit, and all of them take square-planar geometry. fac(S)-[Co(aet)3] is structurally converted into a mer(S)-[Co(aet)3] unit during the course of producing a [{Pt(bpy)}{M(aet)3}]2+-type dinuclear complex, although fac(S)-[Rh(aet)3] retains its structure. These complexes were characterized on the basis of the electronic absorption, CD, and 13C NMR spectra, together with cyclic voltammetry.
Kinetic Results and Reaction Pathways of Intermolecular Thiolato Ligand Migration between Titanocene Complexes and from Cp2TiX(SAr) (X = Cl, SAr) to PtCl(Me)(cod) (cod = η2,η2-1,5-Cyclooctadiene)
Authors: Osakada Kohtaro , Hosoda Tomoya , Yamamoto Takakazu
Published: September 2002

Cp2TiCl(SPh) (1a), prepared from an equimolar reaction of Cp2TiCl2 with NaSPh, undergoes partial and reversible disproportionation in THF into Cp2TiCl2 and Cp2Ti(SPh)2 (2a). The thermodynamic parameters of the reaction are determined to be ΔH° = 13.0(0.6) kJ mol-1 and ΔS° = 14(2) J K-1 mol-1 at 298 K. An equimolar reaction of Cp2Ti(SAr)2 (2a: Ar = C6H5, 2b: Ar = C6H4Me–p, 2c: Ar = C6H4OMe–p, 2d: Ar = C6H4Cl–p, 2e: Ar = C10H7) with PtCl(Me)(cod) in THF leads to an intermolecular exchange of the thiolato and chloro ligands to afford Pt(Me)(SAr)(cod) (3a: Ar = C6H5, 3b: Ar = C6H4Me–p, 3c: Ar = C6H4OMe–p, 3d: Ar = C6H4Cl–p, 3e: Ar = C10H7). Ti complexes: Cp2TiCl2, Cp2TiCl(SAr), Cp2Ti(SAr)2, and a minor amount of (Cp2TiCl)2O, are also present in the products. Absorption spectra of a solution of 2a and excess PtCl(Me)(cod) exhibit distinct changes due to the thiolato ligand transfer, and indicate initial formation of 1a and its subsequent reaction with the Pt complex to form Cp2TiCl2. The reaction of 1a with excess PtCl(Me)(cod) obeys second-order kinetics to [1a]. The observed rate constants, kobsd, increase with an increase in the concentration of PtCl(Me)(cod). Linear plots of the reciprocal of kobsd versus [1a]0/[PtCl(Me)(cod)]0 are consistent with the reaction pathway involving the disproportionation of 1a into an equimolar mixture of Cp2TiCl2 and 2a, the latter of which readily reacts with PtCl(Me)(cod) to regenerate 1a.
Synthesis and Characterization of Mixed-Metal Sulfido Clusters with the Cubane-Type PtMo3S4 Core
Authors: Masui Dai , Ishii Youichi , Hidai Masanobu
Published: September 2002

The reaction of the incomplete cubane-type cluster [Mo3(μ3-S)(μ-S)3(H2O)9]Cl4 (1) and [Pt(dba)2] (dba = 1,5-diphenyl-1,4-pentadien-3-one) in MeOH gave a brown precipitate (4) that contains platinum and molybdenum in the atomic ratio of 1 : 3. Further treatment of 4 with 3 equiv of dppe (dppe = 1,2-bis(diphenylphosphino)ethane) gave the cubane-type cluster [PtMo3(μ3-S)4Cl4(dppe)3] (5) in 37% yield, whose molecular structure was unambiguously characterized by X-ray diffraction study of 5·2CH2ClCH2Cl·2H2O. A similar reaction of 4 with 4 equiv of dppe afforded the cationic cluster [PtMo3(μ3-S)4Cl3(dppe)4]Cl (6) in 29% yield, which was characterized spectroscopically. The Pd-Mo and Ni-Mo analogues of the above Pt-Mo clusters, [PdMo3(μ3-S)4Cl3(dppe)4]Cl·CH2Cl2 (7) and [NiMo3(μ3-S)4Cl4(dppe)3] (8), were also synthesized by the reactions of the corresponding aqua clusters with dppe.
Kinetic Study on the Oxidation of Trichlorophenol Using Hydrogen Peroxide and an Iron(III) Complex of Tetrasulfonatophthalocyanine Catalyst
Authors: Kasuga Kuninobu , Mori Kentaro , Sugimori Tamotsu , Handa Makoto
Published: September 2002

An oxidative decomposition of TCP, catalyzed by the title complex in the presence of hydrogen peroxide, was studied kinetically. The decrease in the initial reaction rate in an acidic solution resulted from a depression of the proton dissociation of hydrogen peroxide.
Molecular Structures of Methyl 5,6-Diaryl-1,2,4-trimethyl-7-oxobicyclo[2.2.1]hept-5-en-2-
endo
-carboxylates (aryl = phenyl or
o
-methoxyphenyl)
Authors: Balasubrahmanyam SNatarajan , Rao Sunkada P , Bhadbhade Mohan M , Sudarsanakumar C , Joseph Bubbly K
Published: September 2002

Structural assignments based on a reconstruction from the 1H NMR dynamic behavior of the three 5,6-bis(substituted aryl)-7-oxo-5-norbornene-2-carboxylic esters named in the title have received confirmation from X-ray crystallographic studies. The specific structural features of these systems are compared among themselves and with those of 7-oxo-5,6-diphenyl-5-norbornene-2-carboxylic esters, analogues systems without substitution on the phenyl groups, which were studied earlier.
Iodination of Both Deactivated and Activated Arenes with Sodium Periodate or Sodium Iodate as the Oxidants
Authors: Lulinski Piotr , Skulski Lech
Published: September 2002

Five easy, relatively inexpensive, and environmentally-safe aromatic oxidative iodination procedures are presented; three of them are particularly suitable for deactivated arenes. Nine deactivated arenes, four halobenzenes, benzene, toluene, and N,N-dimethylaniline were reacted upon with the following anhydrous systems: diiodine/NaIO4 or (in four cases) NaIO3/acetic anhydride/glacial acetic acid, acidified with varying amounts of concd (98%) sulfuric acid; the following workups are explained. The aromatic oxidative iodination reactions proceeded mostly at room temperature and within 1—8 h to give fifteen mono- and two diiodinated purified products (sometimes obtained in 2—3 different ways) in 51—95% yields.
Study of the Mechanism for the Hydrolysis of Alkoxy(aryl)(phenyl)-λ6-sulfanenitriles, ArPhS(OR)(N)
Authors: Yoshimura Toshiaki , Dong Tiaoling , Fujii Takayoshi , Ohkubo Masanori , Sakuta Mikiko , Wakai Youko , Ono Shin , Morita Hiroyuki , Shimasaki Choichiro
Published: September 2002

The hydrolysis of alkoxy(aryl)(phenyl)-λ6-sulfanenitriles in several buffer solutions was found to follow a good pseudo-first-order kinetic equation, giving the corresponding sulfoximides and alcohols (for the case of the hydrolysis of neopentyloxy-λ6-sulfanenitrile, giving a rearranged product, 2-methyl-2-butanol). The dependence of the rate of hydrolysis on the structure of the alkyl group showed the opposite trend to the usual SN2 character, i.e. Me < Pr < Bu ≈ Et < i–Pr, except for neopentyl. The pH-rate profiles indicated that the rate of hydrolysis is also first order in [H+] at pH more than 6.08, and trends to saturate at low pH. According to these kinetic results, a two-step reaction mechanism was proposed which involves a pre-equilibrium protonation on the nitrogen atom of the alkoxy-λ6-sulfanenitriles, followed by a rate-determining C-O bond cleavage via an SN2 or SN1 mechanism on the alkyl carbon atom depending on the structure of the alkyl group. From a double-reciprocal plot of 1/kobs vs. 1/[H+], the pKa value and the rate constant of the second reaction of neopentyloxy(diphenyl)-λ6-sulfanenitrile were estimated to be 5.02 and 7.02×10-3 s-1, respectively. The substituent effects on the phenyl group of neopentyloxy(diphenyl)-λ6-sulfanenitrile afforded a large negative ρ-value (-1.88) for pKa and positive one (+1.66) for the second reaction at 25.2 °C. The small negative ρ-values observed at pH 6.27 for diphenyl(propoxy)-λ6-sulfanenitrile (-0.42) and neopentyloxy(diphenyl)-λ6-sulfanenitrile (-0.26) were found to be the results of a cancellation of those for the opposite trend of the reactions of the pre-equilibrium and the second step. The activation parameters for both the pre-equilibrium and the subsequent reactions were also estimated based on the parameters for the hydrolysis of neopentyloxy(diphenyl)-λ6-sulfanenitrile at pH 6.22 and 2.99. The buffer effect is due to a nucleophilic attack of the buffer base to the alkyl carbon atom of the protonated alkoxy-λ6-sulfanenitriles. The sulfoximide moiety in the protonated λ6-sulfanenitrile is revealed to be a very good leaving group.
In situ Activating Glycosylation of 6-Deoxysugars: Synthesis of O-α-D-Fucosyl-(1→4)-O-α-D-fucosyl-(1→4)-O-α-D-quinovosyl-(1→4)-D-quinovose
Authors: Koto Shinkiti , Kusunoki Ami , Hirooka Motoko
Published: September 2002

The linear tetrasaccharide, α-D-fucopyranosyl-(1→4)-α-D-fucopyranosyl-(1→4)-α-D-quinovopyranosyl-(1→4)-D-quinovopyranose, the sugar cluster of asterosaponin A from the starfish, Asterias amurensis, was synthesized in a convergent manner. We employed an in situ activating glycosylation using 1-OH sugar derivatives and a system of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine as well as a related system.
Intramolecular Stacking of Two Aromatic Rings in the Platinum(II) Coordination Sphere: Preparation, Crystal Structures, and 1H NMR Spectra of Bipyridine(N-arylmethyl-1,2-ethanediamine)platinum(II) Nitrate
Authors: Goto Masafumi , Matsumoto Takashi , Sumimoto Masamitsu , Kurosaki Hiromasa
Published: September 2002

Square-planar complexes with the formula [Pt(L1)(L2)](NO3)2·nH2O, where L1 is bipyridine (bpy) and L2 is N-benzyl-1,2-ethanediamine (Been) (1) (n = 0), N-(1-naphthyl)methyl-1,2-ethanediamine (Npen) (2) (n = 2), and N-(9-anthryl)methyl-1,2-ethanediamine (Aten) (3) (n = 2), were prepared and X-ray crystal-structure determinations were carried out. The molecular structures of the complex cations revealed that the N-arylmethyl groups are forced to take pseudo axial dispositions due to an intramolecular repulsion from hydrogen atoms of bpy. The aromatic-aromatic interaction between the aromatic rings of ethanediamine derivatives and coordinated bpy caused 2 and 3 to take a conformation where the aromatic ring and bpy stack face-to-face to each other intramolecularly. An intermolecular aromatic-aromatic face-to-face interaction was also observed for 1, 2, and 3 in the crystals. The latter interaction occurs between bpy and the aryl substituent, except for 1. For D2O solutions of 1 through 3, significant upfield shifts due to the intramolecular stacking were observed in the 1H NMR spectra for the protons on the half ring of bipyridine, depending on the size of the aromatic ring. The crystal data of 1: monoclinic, P21/c, a = 9.884(2), b = 24.717(2), c = 9.560(5) Å, β = 113.83(3)°, Z = 4, and R = 0.029. 2: monoclinic, Ia, a = 17.030(5), b = 10.461(4), c = 14.727(4) Å, β = 94.72°, Z = 4, and R = 0.023. 3: monoclinic, Pn, a = 10.471(2), b = 8.844(5), c = 15.332(3) Å, β = 98.61(2)°, Z = 2, and R = 0.034.
Effects of Anions in Subphases on a Langmuir Monolayer of N,N-Dimethyl-1-octadecanamine
Authors: Negi Shigeru , Futami Eri , Tsukube Hiroshi , Kano Koji
Published: September 2002

The surface pressure-area (π-A) and surface potential-area (ΔV-A) isotherms of N,N-dimethyl-1-octadecanamine (C18NMe2) were measured on water subsolutions containing various sodium halides (NaX). The amine monolayer showed an expanded liquid (LE) to a condensed liquid (LC) phase transition on water at pH 7 containing 0.01 mol dm-3 NaF, while only the LE phase existed on a subsolution with NaI. The Langmuir monolayer (LM) regularly expanded and the A value at π = 30 mN m-1 increased in the order F- < Cl- < Br- < I-, while the ΔV value decreased in the order F- > Cl- > Br- > I-. The X--dependent π-A isotherm of the C18NMe2 LM is interpreted in terms of deprotonation from the protonated amine molecules at the LM surface upon compression. Similarly, the C18NMe2 LM expanded regularly in the presence of AMP, ADP, and ATP. Such a phenomenon is understandable by assuming that a high-valent anion in subphase is bound to protonated amine molecules more strongly than a low-valent anion.
Homo-Coupling Reactions of Alkenyl- and Arylfluorosilanes Mediated by a Copper(I) Salt
Authors: Nishihara Yasushi , Ikegashira Kazutaka , Toriyama Fumihiko , Mori Atsunori , Hiyama Tamejiro
Published: September 2002

Homo-coupling reactions of an alkenyl- or arylsilane readily occur with a copper(I) salt in an aprotic polar solvent such as N, N-dimethylformamide or dimethyl sulfoxide under an aerobic condition to give the corresponding conjugated dienes or biaryls, respectively. Optimization of a copper salt and a solvent for the homo-coupling reaction is discussed. The formation of the organocopper intermediates is evidenced by trapping experiments with iodine and by a conjugate addition to methyl vinyl ketone.
A Chiral Tweezers-Type Dicarboxylic Acid: Studies on Its Complexation with Amines Utilizing CD Spectrum
Authors: Matsui Hiroyuki , Kushi Sayuri , Matsumoto Shoji , Akazome Motohiro , Ogura Katsuyuki
Published: September 2002

Complexation of a tweezers-type dicarboxylic acid (1) having an optically active π-system at its center with tertiary amines (triethylamine and DABCO) and secondary amines (piperidine and 4,4′-bipiperidine) was investigated under highly dilute conditions (about 6×10-5 mol dm-3) in CHCl3. The complex formation could be pursued with the CD spectrum of 1 which is markedly varied due to the titration of amines. The complexation process is discussed.
1,4-Addition of Diorganozincs to α,β-Unsaturated Ketones Catalyzed by a Copper(I)-Sulfonamide Combined System
Authors: Kitamura Masato , Miki Takashi , Nakano Keiji , Noyori Ryoji
Published: September 2002

A mixture of CuCN and N-benzylbenzenesulfonamide catalyzes the 1,4-addition of dialkylzincs or diarylzincs (Cu : Zn = 1 : 200 to 1 : 10000) to α,β-unsaturated ketones to give, after aqueous workup, the corresponding β-substituted ketones in nearly quantitative yields. A range of cyclic enones having s-cis or s-trans geometries as well as conformationally flexible acyclic enones are usable as substrates. The ethyl group migrates more readily than the methyl and phenyl groups. CuOTf, CuO-t-C4H9, and mesitylcopper can be used in place of CuCN. The in situ-formed alkylzinc enolate, prior to aqueous workup, further undergoes an aldol reaction with aldehydes or Pd(0)-assisted coupling with allyl acetate, resulting in regio-controlled, vicinal carbacondensation products. A catalytic cycle is proposed on the basis of a kinetic study and a structural analysis of the zinc enolate product by NMR and molecular weight measurements.
Two-Dimensional Correlation Spectroscopy: Principle and Recent Theoretical Development
Authors: Ozaki Yukihiro , Šašic Slobodan , Tanaka Takeyuki , Noda Isao
Published: September 2002

This review paper aims at examining the recent developments in optical two-dimensional (2D) correlation spectroscopy. Particular emphasis is put on progress in the theory and calculation methods in 2D correlation spectroscopy. A historical review of 2D correlation spectroscopy is described first, and the mathematical treatment of generalized 2D correlation spectroscopy is explained next. Then a recently proposed efficient route to calculating 2D correlation spectra is reviewed in detail. Examples of applications of 2D correlation spectroscopy are also reported. In the last part of this article, a new possibility of the generalized 2D correlation spectroscopy, sample-sample correlation spectroscopy, is to be discussed.
Solvation Structure of Lithium Bromide in Concentrated Acetone Solutions
Authors: Kameda Yasuo , Kudoh Naomi , Suzuki Shun , Usuki Takeshi , Uemura Osamu
Published: September 2002

Polarized Raman scattering and neutron diffraction measurements have been carried out for concentrated LiBr acetone solutions, in order to deduce detailed information on the solvation structure of Li+ in non-aqueous solutions. Isotropic Raman spectra observed for (LiBr)x[(CH3)2C=O]1−x with x = 0.02–0.06 exhibited a polarized peak at ν ≈ 370 cm−1 which is attributable to the interionic vibration of Li+···Br− ion pair which is formed in the solutions. The neutron distribution function around Li+, GLi(r), derived from the first-order difference function between 6Li/7Li isotopically substituted 6 mol% LiBr acetone-d6 solutions indicated the presence of a well-defined first solvation shell around Li+ in the solution. The nearest neighbor Li+···O(acetone) distance, rLiO, and coordination number, nLiO, were respectively determined to be 2.24(1) Å and 3.2(1), from the least squares fitting analysis for the observed difference interference function, ΔLi(Q). Structure parameters for the nearest neighbor Li+···Br− interaction were determined to be rLiBr = 2.86(2) Å and nLiBr = 0.8(1), respectively.
Synthesis and Structural Characterization of Tetranuclear Zinc(II) Complexes with a Linear Array
Authors: Mikuriya Masahiro , Ikenoue Shuichi , Nukada Ryoji , Lim Jong-Wan
Published: September 2002

1,3-Bis(salicylideneamino)-2-propanol (H3salpro) and 1,3-bis(salicylideneamino)propane (H2salpn) react with Zn(ClO4)2•6H2O and pyrazole (Hpz) to give tetranuclear complexes with a linear Zn4 array, [Zn4(Hsalpro)2(pz)2-(Hpz)2](ClO4)2 (1) and [Zn4(salpn)2(pz)2(Hpz)2] (ClO4)2 (2), which were characterized by infrared spectra and X-ray crystallography.
Desymmetrization of Achiral Skeletons by Mono-Substitution. Its Characterization by Subduction of Coset Representations
Authors: Fujita Shinsaku
Published: September 2002

A set of equivalent positions in an achiral skeleton is regarded as an orbit as-signed to a coset representation G(/Gi), where the subgroup Gi is Cnv or Cn. Desymmetrization of the achiral skeleton by substituting a single ligand is examined by virtue of the subduction of the coset representation G(/Gi) ↓ Gi, which is determined to be αGi(/Gi) + βGi(/Gk(i)). The multiplicities (α and β) of the resulting coset representations are calculated from the data of the participating groups and the normalizer of Gi.
Electric Field Effects on the Adsorption, Charge Transfer and Vibrational State at Metal Electrodes: A DFT Study on H2O/Pt(111), H2O/Pt(100) and (H2O)2/Pt(111)
Authors: Ohwaki Tsukuru , Kamegai Kazuhisa , Yamashita Koichi
Published: September 2002

Electric field (EF) effects on an adsorbed H2O and (H2O)2 on Pt(111) and (100) surfaces have been studied using density functional theory (DFT) at the B3LYP/LanL2DZ level. For the interactions between the H2O and the Pt surface (modeled as a cluster), natural bond orbital (NBO) analysis was performed. This showed that the H2O interacts strongly with the Pt surface through the higher energy level lone pair of the H2O in a parallel orientation. Geometry optimizations of the adsorbed water molecule on the Pt(111) surface were carried out, and the changes in the orientation and geometry induced by the EF are discussed. In the cases of EF = 0 and EF > 0, the charge transfer interaction between the H2O and the Pt surface dominates and the H2O is adsorbed at the top site. For EF < 0, the interaction between the dipole moment of the H2O and EF dominates over the charge transfer interaction. Based on the optimized geometries, we have analyzed the vibrational structure and the EF effects on the vibration of the adsorbed H2O. For the (H2O)2 adsorbed on the Pt(111) surface, partial-optimization calculations have been carried out and the hydrogen bonding in the dimer has been analyzed.
Pressure and Viscosity Effects on Thermal Geometrical Isomerization of Oxacarbocyanine Cations
Authors: Kim Jong Chul , Ohga Yasushi , Asano Tsutomu , Weinberg Noham N , George Adrian V
Published: September 2002

Pressure and viscosity effects on the rate of thermal Z/Eisomerization of two carbocyanine dyes, 3,3′-diethyloxacarbocyanine iodide (DOCI) and 3,3′-diethyloxadicarbocyanine iodide, (DODCI) were measured in 2-methylpentane-2,4-diol. From the results, the following conclusions are obtained. 1. The medium and the chemical coordinates have to be treated separately, as in the reactions of uncharged species. 2. A positive charge on the reactant seems to induce an earlier deviation from the transition state theory. 3. The most important factors controlling a deviation from the transition state theory are the anisotropy of the characteristic times of reaction and solvent fluctuations, and the strength of the solute-solvent interactions.
Isotope Effects of Hafnium in Solvent Extraction Using Crown Ethers
Authors: Fujii Toshiyuki , Moriyama Hirotake , Hirata Takafumi , Nishizawa Kazushige
Published: September 2002

Hafnium isotopes were fractionated in a liquid–liquid extraction system by using seven types of crown ethers, tributyl phosphate, or o-diethoxybenzene. The largest isotope effect was observed in the isotope pair of 177Hf–179Hf with dibenzo-24-crown-8; the isotope enrichment factor was observed to be 0.0129 ± 0.0032.
Conformations of 1,2-Dicyano-1,1,2,2-tetraphenylethane and Cyanodiphenylmethyl Peroxide
Authors: Lam Yulin , Lee Gene-Hsiang , Liang Eping
Published: September 2002

The solid-state structures of 1,2-dicyano-1,1,2,2-tetraphenylethane and cyanodiphenylmethyl peroxide are determined by X-ray crystallography. Both molecules adopt the trans conformation in the solid-state. Experimentally derived values of the energy difference between the gauche and trans rotamers and their population quotient are compared with values predicted by semiempirical MO calculations.
Site-Selective Recognition of Amino Acids by Co(III) Complexes Containing a (N)(O)3-Type Tripodal Tetradentate Ligand
Authors: Kumita Hideyuki , Morioka Taiju , Ozawa Tomohiro , Jitsukawa Koichiro , Einaga Hisahiko , Masuda Hideki
Published: September 2002

The bis-N,N-carboxymethy-(S)-phenylalaninato carbonato cobalt(III) complex, [Co(bcmpa)(CO3)]2−, has been prepared as a simple model that enables the recognition of an amino acid (Haa) whose coordination behaviours in solution have been characterized by electronic absorption (AB), circular dichroism (CD) and 1H NMR spectroscopies. The reaction of the K2[Co(bcmpa)(CO3)] complex with amino acids (Haa) has predominantly afforded the [Co(bcmpa)(aa)] complex in the trans(N)-configuration mode, rather than in the cis(N)-form. By using amino acid derivatives with bulky substituents at their amino or carboxylate sites under a neutral condition, the reactions have been demonstrated to be initiated by coordination of the amino nitrogen site. Interestingly, the cis(N)-complex, which is isolated as a minor product, isomerizes to the trans(N)-form in the presence of active charcoal under pH 7 in an aqueous solution. The site-selective coordination of Haa to the [Co(bcmpa)(CO3)]2− complex and the stereoselective isomerization of the [Co(bcmpa)(aa)]− complex have been explained to be regulated by weak non-covalent interactions within the ligands, whose origin has been discussed based on a detailed examination of the crystal structures of the trans(N)- and cis(N)-K[Co(bcmpa)(aa)] complexes.
Enhanced Reactivity in the Quinolinium Fluorochromate Cooxidation of Some Cycloalkanones and Oxalic Acid
Authors: Meenakshisundaram Subbiah , Sockalingam Ramanathan
Published: September 2002

Under identical experimental conditions, the kinetics of the oxidation of oxalic acid and cycloalkanones with quinolinium fluorochromate (QFC) was examined separately and the rate coefficients evaluated. Oxalic acid reacts ca. 70-times faster than cyclohexanone. It seems that the enol form of the cycloalkanone is the active substrate. π-Complex formation has been envisaged to explain the oxidation of cycloalkanones. The formation of a 2 : 1 oxalic acid–QFC complex has been assumed to be the slow rate-limiting step in the oxalic acid–QFC oxidation system. The cooxidation process has been characterized by the rate equation,

k obs = k′[Oxalic acid]2 + k′′[Oxalic][Ket][H+].

The presence of oxalic acid results in the suppression of a ring-cleavage reaction, yielding cyclohexane-1,2-dione as the main product. Cr(II) involvement in the reaction sequence is ruled out. Mn(II) catalyzes the cooxidation process at its higher concentrations. The order of reactivity C6 > C8 > C5 > C7, is explained.
197Au Mössbauer Spectroscopy Studies of Some Cyclometalated Gold Dimers
Authors: Bhargava Suresh K , Mohr Fabian , Takahashi Masashi , Takeda Masuo
Published: September 2002

The oxidation states and structures of a series of cyclometalated gold complexes derived from oxidative addition reactions of the digold(I) complex [Au2(μ-C6H3-2-PPh2-6-Me)2] have been determined by 197Au Mössbauer spectroscopy. The spectra for the binuclear gold(I)/gold(I) and gold(II)/gold(II) complexes indicate the presence of equivalent gold atoms, whereas the gold(I)/gold(III) and gold(III)/gold(III) spectra show signals due to two inequivalent metal centers. The coordination spheres of metal centers in the complexes have been determined from isomer shift and quadrupole splitting data.
Syntheses, Structures and Spectroscopic Properties of Mixed-Ligand Chromium(III) Complexes Containing 1,2-Bis(dimethylphosphino)ethane, 1,3-Bis(dimethylphosphino)propane or 1,1,1-Tris(dimethylphosphinomethyl)ethane
Authors: Suzuki Takayoshi , Kashiwabara Kazuo , Usami Tsutomu , Imamura Takeshi , Kiki Masakazu , Fujita Junnosuke , Kaizaki Sumio
Published: September 2002

Mixed-ligand chromium(III) complexes containing di- or tridentate phosphines, trans-[CrX2(dmpe)2]+ (X = Cl, Br, I, CN, NCS or N3; dmpe = Me2P(CH2)2PMe2), trans-[CrX′2(dmpp)2]+ (X′ = Cl, Br or I; dmpp = Me2P(CH2)3PMe2), [CrX′′3(tdmme)] (X′′ = Cl, Br, CN or NCS; tdmme = MeC(CH2PMe2)3) and [CrCl2(tdmme)(PMe3)]+, have been prepared and their structures and spectroscopic properties have been investigated. The single-crystal X-ray analyses of trans-[CrI2(dmpp)2]I (6) and [Cr(CN)3(tdmme)]·2H2O (16·2H2O) have also been reported. The Cr–P bond length in 6 (2.5147(6) Å) is longer than those in trans-[CrCl2(dmpe)2]BPh4 (av 2.445 Å) and in 16·2H2O (av 2.455 Å). In the UV-vis absorption spectra of trans-[Cr(Cl or Br)2(dmpe or dmpp)2]+, an intense (ε > 1000 dm3 mol−1 cm−1) absorption envelope is observed at 20000–30000 cm−1, in addition to the 4B1 → a4E d–d transition band at ∼17000 cm−1 (ε = 44–65 dm3 mol−1 cm−1). The envelope consists of three d–d transition components: 4B1 → 4A2, 4B2 and b4E, similar to the corresponding H2N(CH2)2NH2 (= en) complexes. The magnetic circular dichroism (MCD) spectra of these didentate phosphine complexes show a spin-forbidden d–d transition (4B1 → 2E, 2B2) component at ∼19000 cm−1. The ligand-field and Racah parameters, Δ(d), Δ(e), Δ(t2) and B, of the complexes are estimated. It is found that the ligand-field and repulsion parameters of the dmpp complexes are almost the same as those of the corresponding en complexes. For the dmpe complexes, while Δ(d) is just slightly smaller than those of the dmpp and en complexes, the tetragonal symmetry parameters, Δ(e) and Δ(t2), are much reduced. The ligand-field perturbation energies of phosphines are estimated as Δdmpp = 21830 > Δtdmme = 20920 > Δdmpe = 20620 cm−1, the order of which is strange, since the Cr–P bond lengths in the complexes increase in the order of dmpp > tdmme > dmpe. Furthermore, the interelectronic repulsion parameter B of [Cr(Cl or Br)3(tdmme)] estimated from the 4A2 → 4T1 transition energy (B35) is remarkably much smaller than the parameter estimated from the spin-forbidden 4A2 → 2T2 transition energy (B55).
Structural Effects on Nitratocopper(II) Complexes of Tris(pyrazolyl)borates
Authors: Fujisawa Kiyoshi , Miyashita Yoshitaro , Yamada Yasunori , Okamoto Ken-ichi
Published: September 2002

Some structural influences on nitratocopper(II) complexes ligated by a series of hydrotris(pyrazolyl)borates are described. The 5-position of pyrazole rings as well as the 3-position is important to provide coordination structure.
Preparation of Artificial Urushi via an Environmentally Benign Process
Authors: Ikeda Ryohei , Tanaka Hozumi , Oyabu Hiroshi , Uyama Hiroshi , Kobayashi Shiro
Published: September 2002

“Artificial urushi” has been developed by laccase-catalyzed curing of new urushiol analogues. The analogues were designed and conveniently synthesized by regioselective acylation of phenol derivatives having a primary alcohol with unsaturated fatty acids using lipase as catalyst. The curing of the catechol derivative having a linolenoyl group proceeded in the presence of acetone powder from Chinese urushi, yielding the crosslinked film (“artificial urushi”) with high hardness and gloss surface, which are comparable with those of natural urushi coating. The analogues obtained from vanillyl alcohol were also cured. FT-IR monitoring of the curing showed that the crosslinking mechanism was similar to that of the natural urushi. The curing of the urushiol analogues in the presence of starch–urea phosphate took place to give the artificial urushi consisting exclusively of synthetic compounds.
Calf-Thymus DNA Interaction with Cr(III)-Gallate and Cr(III)-Ethyl Gallate Studied by FTIR Spectroscopy and Capillary Electrophoresis
Authors: Arakawa Hirohumi , Watanabe Norimoto , Tajmir-Riahi Heidar-Ali
Published: September 2002

Cr(VI) salts are well known to be carcinogen, and are reduced by various cellular components to form cross-linked Cr(III) products. Organic compounds, such as gallic acid (GA) and ethyl gallate (EGA), reduce Cr(VI) to Cr(III) to form Cr(III)-gallate [Cr(III)-GA] and Cr(III)-ethyl gallate [Cr(III)-EGA] as final products. These Cr(III)-tannin complexes are DNA binders. The interaction of calf-thymus DNA with Cr(III)-GA and Cr(III)-EGA in aqueous solutions at physiological pH were studied at Cr(III)/DNA (phosphate) molar ratios (r) of 1 : 160, 1 : 80, 1 : 40, 1 : 20, 1 : 10, 1 : 4, and 1 : 2 using FTIR spectroscopy and capillary electrophoresis. An analysis by FTIR showed that at low concentrations (r = 1/80 and 1/40), Cr(III)-GA and Cr(III)–EGA mainly bind to the guanine N-7 atom of the G–C base pairs with minor perturbations of the A–T base pairs. At r > 1/20, a partial helix opening occurred with major perturbations of the G–C and A–T base pairs. At r > 1/10, aggregation of the Cr(III)-tannin–DNA complexes occurred. However, no DNA conformational changes were observed, and the DNA maintained the B-family structure. The binding constants of the Cr(III)-GA–DNA and Cr(III)-EGA–DNA were estimated to be 3.8 × 104 M−1 and 6.2 × 104 M−1, respectively, by Scatchard plots following capillary electrophoresis. These results suggest that the Cr(III)-tannin complexes are external DNA binders, and do not form a chelate with the DNA.
Hydrophobic Character of Ca2+-bound S-100 Complexes
Authors: Matsuda Sadayuki
Published: September 2002

The hydrophobic character of S-100 complexes was investigated in terms of their adsorbability on phenyl-Sepharose gel in the presence of several co-adsorptive reagents. The following results were obtained: The hydrophobicity of S-100a.a′ was obviously increased by Ca2+-binding, and that of Ca2+-bound S-100a.a′ had practically no further increase upon mastoparan (MP)- or Zn2+-binding. In the case of S-100b, on the contrary, the increase in the hydrophobicity by Ca2+-binding was less than that for the former, and that of the Ca2+-bound sample showed a further increase by MP-binding, or especially by Zn2+-binding.

The hydrophobicity was also investigated with 2-p-toluidinonaphthalene-6-sulfonate (TNS). The adsorbability of the TNS-bound area was evaluated using fluorescence spectrophotometry. The hydrophobicity of Ca2+-bound S-100a.a′ was enhanced only by MP-binding. In the case of Ca2+-bound S-100b, both MP- and Zn2+-binding had appreciable effects on the hydrophobicity, and their co-existence had a greater effect than the additive of each one.
Solvolytic Stereoselective Debromination of vic-Dibromides with HMPA
Authors: Khurana Jitender Mohan , Bansal Geeti , Chauhan Sushma
Published: September 2002

A simple and efficient procedure for the debromination of vic-dibromides has been reported with hexamethylphosphoric triamide at 155–160 °C under a nitrogen atmosphere without the aid of any reagent.
Structure and Properties of 9-(Cycloheptatrienylidene)fluorene and Its Derivatives
Authors: Minabe Masahiro , Tomiyama Takashi , Nozawa Toshiya , Noguchi Makoto , Nakao Akiko , Oba Toru , Kimura Takao
Published: September 2002

One sesquifulvalene, 9-(cycloheptatrienylidene)fluorene, was found to be composed of a flat fluorenylidene part and a non-planar cycloheptatrienylidene moiety. 1-Substituted 9-(cycloheptatrienylidene)fluorene was not obtained because of a steric repulsion between the 1-substituent and the 7′-hydrogen of the seven-membered ring. Upon consideration of their 13C NMR spectra, the electronic properties of the seven-membered ring are slightly influenced by introducing a substituent (halogen, methoxy group, etc.) on the fluorenylidene part. The dissolution of 9-(cycloheptatrienylidene)fluorene in trifluoroacetic acid–chloroform afforded the (9-fluorenyl)tropylium cation. The substituent attached to the fluorene part also slightly influences the tropylium moiety.
Theoretical CD Spectrum Evaluation of the Indolylfulgide Molecules by Using Semi-Empirical Molecular Orbital Calculations
Authors: Ankai Eikoh , Sakakibara Kazuhisa , Uchida Soichi , Uchida Yuki , Yokoyama Yayoi , Yokoyama Yasushi
Published: September 2002

A fulgide is a photochromic molecule which can not be isomerized by a thermal reaction. The CD spectra of the optically resolved helically chiral indolylfulgide (99% enantiomer excess), whose absolute configurations have been determined by an X-ray crystallographic analysis of their binaphthyl derivative, were estimated theoretically within the framework of semi-empirical molecular-orbital calculations. The optical rotatory strength of the indolylfulgide was calculated based on the Rosenfeld equation by using the optimized structures, conformational energies, and molecular orbitals. The estimated CD spectra reproduced characteristic features, such as the peak shape and sign of the Cotton effect, quite well, though the accuracy of the calculated wavelengths for the individual CD peaks’ maxima was fair.
Synthesis of Pyrrolo[1,2-a]quinoxaline Derivatives by Lewis Acid-Catalyzed Reactions of 1-(2-Isocyanophenyl)pyrroles
Authors: Kobayashi Kazuhiro , Irisawa Susumu , Matoba Takeshi , Matsumoto Takashi , Yoneda Keiichi , Morikawa Osamu , Konishi Hisatoshi
Published: September 2002

1-(2-Isocyanophenyl)pyrroles have been prepared. They react in moderate to good isolated yields with aldehydes (or ketones), oxiranes, and acetals in the presence of catalytic amounts of diethyl ether–boron trifluoride to give pyrrolo[1,2-a]quinoxalines carrying an oxyalkyl substituent, such as α-hydroxyalkyl, β-hydroxyalkyl, or α-alkoxyalkyl, at the 4-position.
Stereocontrol in a Ytterbium Triflate-Catalyzed 1,3-Dipolar Cycloaddition Reaction of Carbonyl Ylide with N-Substituted Maleimides and Dimethyl Fumarate
Authors: Suga Hiroyuki , Kakehi Akikazu , Ito Suketaka , Inoue Kei , Ishida Hajime , Ibata Toshikazu
Published: September 2002

The addition of Yb(OTf)3 (10 mol%) in a Rh2(OAc)4-catalyzed reaction of o-(methoxycarbonyl)-α-diazoacetophenone with N-methylmaleimide in CH2Cl2 or in diethyl ether gave cycloadducts with high endo-selectivity (endo : exo = 95 : 5–96 : 4). The CuOTf (20 mol%)- or CuCl-Yb(OTf)3 (5 mol%)-catalyzed reaction also gave 1,3-dipolar cycloadducts in an endo-selective manner (endo : exo = 94 : 6). On the other hand, a reaction using only Rh2(OAc)4 (5 mol%) as the catalyst in benzene under reflux gave cycloadducts with exo-selectivity (endo : exo = 11 : 89). The reaction of N-ethyl- and N-phenylmaleimides under the same conditions showed a similar tendency in terms of the stereoselectivity.
Chemoenzymatic Synthesis of a Trisaccharide–Serine Conjugate, Gal(β1-3)Gal(β1-4)Xyl(β1-O)–l-Ser, Use of Galactosyl Fluoride as a Donor for Transglycosylation
Authors: Fukase Koichi , Yasukochi Takashi , Kusumoto Shoichi
Published: September 2002

The trisaccharide–serine conjugate [Gal(β1-3)Gal(β1-4)Xyl(β)-Ser], constituting the linkage region between the glycosaminoglycan and protein in proteoglycan, was synthesized by using enzymatic transglycosylation with a β-d-galactosidase as a key reaction. The yields of transglycosylation were much improved by using galactosyl fluoride as a donor in comparison with those obtained by a conventional p-nitrophenyl (PNP) galactoside. After enzymatic synthesis of Gal(β1-3)Gal(β1-4)Xyl(β)–PNP, cleavage of the PNP group of the fully acetylated trisaccharide, chemical coupling with serine, and final deprotection afforded Gal(β1-3)Gal(β1-4)Xyl(β)–Ser.
Asymmetric Addition of Allylic Stannanes to Aldehydes Catalyzed by BINAP•Ag(I) Complex
Authors: Yanagisawa Akira , Nakashima Hiroshi , Nakatsuka Yoshinari , Ishiba Atsushi , Yamamoto Hisashi
Published: September 2002

Catalytic asymmetric allylation of aldehydes with allylic trialkylstannanes was achieved with BINAP•AgOTf complex as catalyst. The chiral silver(I) catalyst was readily prepared by stirring an equimolar mixture of BINAP and silver(I) triflate in THF at room temperature. The allylation of a variety of aromatic and α,β-unsaturated aldehydes resulted in high yields and remarkable enantioselectivities. Addition of γ-substituted allylstannanes such as 2-butenyltributylstannane and trialkyl-2,4-pentadienylstannanes exclusively gave γ-adducts. High anti-selectivity was also obtained in the reaction with 2-butenyltributylstannane, irrespective of the configuration at the double bond.
An Effective Method for the Preparation of Chiral Polyoxy 8-Membered Ring Enone Corresponding to the B Ring of Taxol
Authors: Shiina Isamu , Shibata Jun , Ibuka Ryoutarou , Imai Yumiko , Mukaiyama Teruaki
Published: September 2002

An effective method for the preparation of 8-membered ring enone, (4S,5R,7R,8R)-4,8-bis(benzyloxy)-7-(t-butyldimethylsiloxy)-5-(4-methoxybenzyloxy)-2,6,6-trimethylcyclooct-2-enone (1), in sufficient quantities was developed. Optically active trioxy aldehyde, (3R,4S)-4-benzyloxy-5-(t-butyldimethylsiloxy)-3-(4-methoxybenzyloxy)-2,2-dimethylpentanal (3), was prepared first by diastereoselective dihydroxylation of (2R,4S)-2-(4-methoxyphenyl)-5,5-dimethyl-4-vinyl-1,3-dioxane derived from D-pantolactone. Next, 8-chloro-7-oxoaldehyde, (2R,3R,5R,6R)-2,6-bis(benzyloxy)-5-(t-butyldimethylsiloxy)-8-chloro-3-(4-methoxybenzyloxy)-4,4-dimethyl-7-oxononanal (30), was newly synthesized by the following reactions: i) MgBr2•OEt2-mediated diastereoselective aldol reaction of the aldehyde 3 with (Z)-2-benzyloxy-1-methoxy-1-(trimethylsiloxy)ethene and ii) reaction of methyl (2R,3R,5R,6S)-2,6-bis(benzyloxy)-3,7-bis(t-butyldimethylsiloxy)-5-(4-methoxybenzyloxy)-4,4-dimethylheptanoate with 1,1-dichloroethyllithium, followed by successive reductive dehalogenation of thus formed 1,1-dichloroethyl ketone with 1,1-dichloroethyllithium. Then, the chiral 8-chloro-7-oxoaldehyde 30 was converted to the 8-membered ring enone 1 by SmI2-mediated aldol cyclization.
Conformational Study of the Tandem Repeat Sequence in RNA Polymerase II by Circular Dichroism Spectroscopy
Authors: Ohiso Isao , Tsunemi Masahiko , Zhao Budiao , Nishi Norio
Published: September 2002

The largest subunit of RNA polymerase II has an interesting C-terminal domain, which consists of a multiple tandem repeat of a heptapeptide with the consensus sequence Ser–Pro–Thr–Ser–Pro–Ser–Tyr. However, the functional role of this sequence is unclear. One might assume that the conformation of the tandem repeat is very important for its function. The conformation of poly(Ser–Pro–Thr–Ser–Pro–Ser–Tyr) and H–Ser–Pro–Thr–Ser–Pro–Ser–Tyr–OH, corresponding to the repeat and the repeating unit of the C-terminal domain, respectively, were investigated exhaustively by circular dichroism (CD). The CD spectrum of H–Ser–Pro–Thr–Ser–Pro–Ser–Tyr–OH indicated the presence of a turn structure in water, which was further stabilized in 2,2,2-trifluoroethanol (TFE) and in acetonitrile. The CD spectra of the polyheptapeptide poly(Ser–Pro–Thr–Ser–Pro–Ser–Tyr) suggested that the disordered conformation was predominant in water and that the turn structure was stabilized by increasing the content of TFE or acetonitrile in the solvent. We suggest that the polyheptapeptide forms not only a turn structure at the heptapeptide unit Ser–Pro–Thr–Ser–Pro–Ser–Tyr, but also a kind of super conformation induced by the periodicity of the sequence in TFE or acetonitrile.
Catalytic Activity of Lanthanide(III) Ions for the Dehydration of Hexose to 5-Hydroxymethyl-2-furaldehyde in Water
Authors: Seri Kei-ichi , Inoue Yoshihisa , Ishida Hitoshi
Published: September 2002

All of the lanthanide(III) (La3+–Lu3+) efficiently catalyzed the dehydration of hexose in water at 140 °C to produce 5-hydroxymethyl-2-furaldehyde (HMF) without accompanying further hydrolysis to levulinic acid, which is routinely obtained as a by-product in the conventional Brønsted acid-catalyzed reactions. The relationships between the catalytic activity and the ionic radius (ri) of lanthanides(III) for the dehydration of d-fructose and d-glucose were found to have a double-peak profile maximizing at Pr or Nd (ri 1.00 Å) and Er or Yb (ri 0.87 Å) with a dip at Sm (ri 0.96 Å). Kinetic analyses revealed that the rate-determining step is not the complex formation of lanthanide(III) ion with the saccharide molecule, but a subsequent reaction from the substrate-catalyst complex. Possible reasons why the catalytic activity–ionic radius relationships show a two-peak profile are discussed.
Increasing the Selectivity of Bromination of Aromatic Compounds Using Br2/SiO2
Authors: Ghiaci M , Asghari J
Published: September 2002

In the presence of silica, a number of aromatic hydrocarbons such as toluene, o-, m-, and p-xylene, anthracene and phenol are brominated by Br2 under mild conditions; for example Br2/SiO2 brominates naphthalene readily at 25 °C to 1-bromonaphthalene. For comparison, we have also brominated all of the substrates in with bromine in the absence of silica gel.
Preparation of a Kaolinite–Nylon 6 Intercalation Compound
Authors: Matsumura Asako , Komori Yoshihiko , Itagaki Tetsuro , Sugahara Yoshiyuki , Kuroda Kazuyuki
Published: September 2002

A kaolinite–nylon 6 intercalation compound was prepared by the polymerization of 6-aminohexanoic acid (AHA) in the interlayer space of kaolinite. The intercalation of AHA was achieved by a guest displacement reaction using a kaolinite–methanol intercalation compound as an intermediate. After AHA dissolved in a mixed solvent of methanol and water (1 : 3) was added to a kaolinite–methanol intercalation compound, the mixture was stirred for 3 h. The basal spacing of the product increased to 1.23 nm, indicating the intercalation of AHA molecules with a monolayer arrangement between the layers of kaolinite. AHA was polymerized by a heat treatment at 250 °C for 1 h under a nitrogen flow. Although the basal spacing of the heat-treated product slightly decreased to 1.16 nm, the spacing was larger than those of kaolinite and the kaolinite–methanol intermediate. The formation of a kaolinite-nylon 6 intercalation compound was confirmed by the appearance of IR bands due to amide I (1637 cm−1) and amide II (1550 cm−1).
Pyrene Chemisorption Film on an Alumina Plate as an Optical Oxygen-Sensing Material
Authors: Amao Yutaka , Okura Ichiro , Miyashita Tokuji
Published: September 2002

An optical oxygen sensor based on the fluorescence quenching of pyrene-1-butyric acid (PBA) chemisorption film onto an alumina plate was developed. The fluorescence intensity of PBA film decreased with increasing oxygen concentration. The PBA film sensor is calibrated by a modified Stern–Volmer equation.
Inhibition of NO Decomposition Activity of Perovskite-type Oxides by Coexisting Carbon Dioxide
Authors: Teraoka Yasutake , Torigoshi Ken’ichiro , Kagawa Shuichi
Published: September 2002

Catalytic activity of La-based perovskites, La0.8Sr0.2CoO3 as a representative example, for the direct NO decomposition above 500 °C was decreased by the coexistence of gaseous carbon dioxide. The effect of carbon dioxide was more severe than the well-known impact of oxygen, though it was reversible at 800 °C.
UV and Visible Emission Spectra from the Photodissociation of Carbonyl Sulfide Using Synchrotron Radiation at 15–30 eV
Authors: Mitsuke Koichiro , Mizutani Masakazu
Published: September 2002

The photofragmentation of OCS at photon energies of 15–30 eV has been studied by dispersed fluorescence spectroscopy. The primary photon beam was monochromatized undulator radiation supplied from the UVSOR facility. The following emission-band systems have been identified: OCS+[A2ΠΩ(0,0,0) → X2ΠΩ(0,0,v3′′)], CO+(A2ΠΩ → X2Σ+), CS+(B2Σ+ → A2ΠΩ), and CO(d3Δ → a3Π). All of the transitions, except for OCS+[A2ΠΩ → X2ΠΩ], were first observed in the vacuum UV photodissociation of OCS. The fluorescence excitation spectra for the OCS+[A2ΠΩ(0,0,0) → X2ΠΩ(0,0,v3′′)] and CS+(B2Σ+ → A2ΠΩ) transitions were measured in the photon energy range of 15.1–15.75 and 21.8–26 eV, respectively. The emission spectra obtained at 20.85 and 22.9 eV exhibit atomic transitions of S[nd3Do → 4p3Pe (n = 6–9)], which result from the neutral dissociation of superexcited Rydberg states of OCS into S(nd3Do) + CO. Possible excited states of the counterpart CO are discussed on the basis of the difference in the n distribution between the two spectra.
Time Resolved ESR Study on the Photochemical Reactions of Pyrene and Nitroxide Radical System in Micelle; Formation of Spin-Correlated Pyrene Cation–Nitroxide Pairs
Authors: Kawai Akio , Shikama Atsushi , Mitsui Masaaki , Obi Kinichi
Published: September 2002

Time-resolved ESR (TR-ESR) spectra were measured in the laser excitation of aromatic compounds such as xanthone, bromopyrene, fluoranthene (Flt) and pyrene (Py) in sodium dodecyl sulfate (SDS) aqueous micellar system in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). Net emission (Em) signals of triplet hyperfine (hf) lines of TEMPO were observed in xanthone– and bromopyrene–TEMPO systems. The chemically induced dynamic electron polarization (CIDEP) was explained by radical-triplet pair mechanism. Antiphase signals of TEMPO with Em in low-field side and enhanced absorption in high-field side (EA) of each triplet hf line were superimposed on net Em signals in Flt– and Py–TEMPO systems. The square laser power dependence of the EA signal suggests that the two-photon ionization of Flt and Py is related to the EA antiphase signal. Rate constants of the reactions occurring in SDS solution were determined by analysis of transient absorption decays in the Py–TEMPO system. The reaction rates of Py+–TEMPO and 3Py*–TEMPO in SDS solution were determined as 1.2 × 106 s−1 and 3.0 × 105 s−1, respectively, at the TEMPO concentration of 2 mM (M = mol dm−3). According to these measurements, it was concluded that the EA CIDEP is due to spin-correlated radical pair (SCRP) of TEMPO and Py+ which was formed in the electron transfer reaction from TEMPO to Py+. Simulation of TR-ESR spectra was carried out using SCRP theory. From kinetic analysis of intermediates together with the simulation of TR-ESR spectra, it was concluded that both SCRP of Py+–TEMPO and RTPM of 3Py*–TEMPO contribute to the CIDEP of TEMPO.
Pressure- and Temperature-Induced Phase Transitions in 2,4,6-Trichloro-1,3,5-triazine Crystal
Authors: Tanaka Makiko , Kariu Chinatu , Suzuki Yoshio , Nibu Yoshinori , Shimada Ryoichi , Shimada Hiroko
Published: September 2002

The effects of pressure and temperature on the frequencies and band structures of the Raman active inter- and intramolecular vibrations of 2,4,6-trichloro-1,3,5-triazine crystal were studied. The changes in the Raman frequency, band width, and band structure of both the inter- and intramolecular vibrations induced by changes of pressure and temperature indicate that (1) a displacive phase transition caused by a shear distortion of π-stacked layer structure may take place under about 1.7 GPa at 298 K and (2) the intermolecular nitrogen–chlorine donor–acceptor attractive interactions supporting the extensive network structure in crystal have a direct effect upon the totally symmetric C–Cl stretching vibration.