bluuebunny/crossref_metadata_2025 huggingface dataset:
Unusual Fluorescent Properties of Novel Fluorophores, 6-Aryl-3,4-diphenyl-α-pyrone Derivatives
Authors: Hirano Keisuke , Minakata Satoshi , Komatsu Mitsuo
Published: November 2002

Novel fluorophores, 6-aryl-3,4-diphenyl-α-pyrones, were synthesized and their spectroscopic properties investigated in the form of evaporated films on plain glass slides, as well as in the solid and solution states. An electron-donating aryl group on the 6-position of the pyrones causes a red-shift in the absorption and fluorescent maxima. In the solid states, they show intense blue-to-orange fluorescence, but not in solution. This unusual fluorescent property is caused by fixing the 6-aryl group of the pyrones, and is the result of molecular packing. These interactions induce a pathway for radiative decay, which is associated with intense fluorescence emission only in the solid state.
Origin of the Primary Kinetic Hydrogen Isotope Effects on N-dealkylation from N-alkylamine by Hemoproteins
Authors: Hata Masayuki , Hirano Yoshinori , Hoshino Tyuji , Tsuda Minoru
Published: November 2002

The atomic level reaction mechanism for N-dealkylation of N,N-dimethylaniline (PhNMe2) by hemoproteins, in which a kinetic hydrogen isotope effect (KHIE) was observed, was investigated by quantum mechanical theoretical calculations. Using quantum mechanical theory, one can determine the primary KHIE by the difference in zero-point vibrational energies on normal vibrational modes which are related to the reaction coordinate of H (D or T) atom abstraction from a C–H (C–D or C–T) bond. On the basis of this idea, we theoretically determined the intramolecular primary KHIE for two cases of hydrogen atom abstraction in N-dealkylation of PhNMe2; i.e., hydrogen atom abstraction from a neutral state and proton abstraction from a cation radical state. When the intramolecular primary KHIE obtained by theoretical calculation was compared with experimental results of the intramolecular KHIE on N-dealkylation of PhNMe2, which was catalyzed by some hemoproteins, it was found that four experimental values can be interpreted only from the primary KHIE. However, many other experimental values can not be interpreted only from the primary KHIE.
Stereochemistry and Stereoisomerism Characterized by the Sphericity Concept
Authors: Fujita Shinsaku
Published: November 2002

The sphericity concept proposed for specifying stereochemistry in a molecule (S. Fujita, J. Am. Chem. Soc., 112, 3390 (1990)) has been extended to investigate stereoisomerism among molecules. The new matter of the present approach is to characterize the global symmetries of molecules as the “local symmetries of stereoisomerism”. Thereby, stereochemistry and stereoisomerism have been discussed on a common basis. Promolecules, which have been generated as stereochemical models of molecules by placing proligands (structureless ligands with chirality/achirality) on the vertices of a tetrahedral skeleton, have been analyzed by a permutation-group approach as well as by a point-group one. The skeleton has been considered to belong to the symmetric group of degree 4 (S[4]) as well as to the isomorphic point group Td. The chirality fittingness derived from the sphericity concept has been applied to the characterization of local symmetries of promolecule, where two types of Young’s tableaus have been compared. Thus, Young’s tableaus of symmetry have been introduced to treat the ligand packing based on the chirality fittingness. These tableaus have been compared with Young’s tableaus of permutation, which have taken no account of such chirality fittingness. The two types of Young’s tableaus have been applied to the enumeration of tetrahedral isomers under the observance and the violation of chirality fittingness. This enumeration has enabled us to clarify the quantitative aspect of the sphericity concept in characterizing isomer equivalence. Thereby, equivalent isomers under a point-group symmetry have been shown to construct an orbit of stereoisomers that is ascribed to a coset representation. Homomeric, enantiomeric, and diastereomeric relationships between stereoisomers have been discussed by means of homospheric, enantiospheric and hemispheric orbits of stereoisomers. Skeleton-based and ligand-based categories for enantiomers and diastereomers have been discussed. The stereogenicity and the prostereogenicity of the Chan–Ingold–Prelog system have been related to Young’s tableaus of permutation.
Optical–Optical Double Resonance Spectroscopy of I2 through the Parity Mixed Valence States
Authors: Ishiwata Takashi , Yotsumoto Takashi , Motohiro Satoshi
Published: November 2002

We used the perturbation-facilitated optical–optical double resonance technique to access the ungerade ion-pair states of I2 using the (1 + 1) photo-excitation sequence through the B3Π(0u+)–c1g parity mixing states. By analyzing the second step of the double resonance to the F0u+(3P0), γ1u(3P2), and H1u(3P1) states, the g–u coupling schemes were elucidated in the intermediate B3Π(0u+)–c1g state. We were also able to populate the δ2u(3P2) state through the g–u mixing state, and to improve its molecular constants. The interference effect between the parallel γ1u(3P2)–c1g and perpendicular δ2u(3P2)–c1g transitions was used to derive the ratio of their electronic transition moments, (μ||e/μ⊥e) ∼ 5.5.
HeI Photoelectron and Ab Initio Study of Retinal Derivatives
Authors: Katsumata Shunji
Published: November 2002

The HeI photoelectron spectra of all-trans-retinal, 13-cis-retinal and 9-cis-retinal have been observed in the gas phase by using an infrared heating device, which was developed in this laboratory. The first four ionization energies (Iobs) of all-trans-retinal have been determined to be 7.55, 8.40, 9.21, and 10.03 eV, and the ionization energies for the other two derivatives were also equal to them within the experimental error. Ab initio calculations were performed to study the optimized structures of neutral and cationic ground states of retinals and to elucidate the valence electronic structures associated with the observed ionization energies. The structural change from the neutral to the cation was considered, and the bond lengths and dihedral angles between the planes of the β-ionone ring and the polyene chain in each of retinals have been determined.
Crystal Structure and Photo-Reaction of a New Coordination Polymer: [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]·6H2O
Authors: Gu Zhong-Ze , Sato Osamu , Einaga Yasuaki , Kai Masahiro , Iyoda Tomokazu , Fujishima Akira , Hashimoto Kazuhito
Published: November 2002

A new photo-responsive coordination polymer of [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]·6H2O was synthesized. In this compound, Ni–CN–Fe forms one-dimensional standing-wave-like chains, onto which photo-functional groups of pentacyanonitrosylferrate(II) are appended. Photo-irradiation with blue light at less than 200 K transformed the pentacyanonitrosylferrate(II) from the ground state to a metastable state, which could be reverted to the original state by irradiation with red light.
Synthesis, Structure, and Characterization of an α-Dawson-type [S2W18O62]4− Complex
Authors: Himeno Sadayuki , Tatewaki Hideki , Hashimoto Masato
Published: November 2002

A yellow sulfatotungstate complex was formed by heating a 50 mM W(VI)–2 M H2SO4–40% (v/v) CH3CN system at 70 °C for 14 days, being isolated as the tetrapropylammonium (n-Pr4N+) salt. An X-ray structural analysis (ortho-rhombic, Pca21 (No. 29) a = 27.181(1), b = 14.1428(6), c = 27.7292(9) Å, and Z = 4) revealed that the structure consists of an α-Dawson-type [S2W18O62]4− anion. The α-[S2W18O62]4− complex underwent a four-step reversible one-electron reduction in CH3CN, and the presence of acid caused the one-electron waves to be converted into three two-electron waves. The formation conditions were elucidated by a combined Raman and voltammetric study.
Supercooling of Aqueous Solutions of Alkali Chlorides and Acetates
Authors: Miyata Kuniharu , Kanno Hitoshi , Tomizawa Kiyoshi , Yoshimura Yukihiro
Published: November 2002

Homogeneous nucleation temperatures (TH’s) of aqueous alkali chloride and acetate solutions were measured as a function of salt concentration. There is a linear relation between TH and 1/r+ (r+: ionic radius of alkali ion) for aqueous alkali chloride solutions. In the supercooling of aqueous alkali acetate solutions, the ionization constant also plays an important role in their supercooling behavior. The TH results were discussed in relation to nucleation theory.
Growth of Strontium Chlorapatite Crystals from a Sodium Chloride Flux
Authors: Oishi Shuji , Mitsuya Mai , Suzuki Takaomi , Ishizawa Nobuo , Rendon-Angeles Juan Carlos , Yanagisawa Kazumichi
Published: November 2002

Large and well-formed crystals of strontium chlorapatite [Sr5Cl(PO4)3] were grown for the first time from a sodium chloride flux. The obtained crystals were colorless and transparent. The crystal growth of Sr5Cl(PO4)3 was conducted by heating a mixture of solute and flux at 1100 °C for 10 h, and then cooling to 500 °C at a rate of 5 °C h−1. Hexagonal prismatic crystals with lengths of up to 8.6 mm and widths of 2.1 mm were grown from high-temperature solutions containing 0.05–0.9 mol% solute. The most suitable solute content for the growth of prismatic crystals was 0.2 mol%. The prismatic crystals were bounded by the {101-0} and {101-1} faces. The aspect ratios were in the region of 1.1 to 4.2. Hexagonal needle crystals with lengths of up to 2.6 mm and widths of 60 µm were obtained during every growth run. The needle crystals were elongated in the <0001> directions, with aspect ratios ranging from 33 to 66. The major constituents were almost homogeneously distributed in the prismatic and needle crystals. The solubility of Sr5Cl(PO4)3 crystals in NaCl flux increased with increasing temperature, reaching about 0.25 mol% solubility at 1100 °C.
Effect of Tris(acetylacetonato)chromium(III) as a Complex Ligand on the Extraction of Lanthanoid(III) with 2-Thenoyltrifluoroacetone
Authors: Kameta Naohiro , Imura Hisanori
Published: November 2002

Enhancement of the extraction of lanthanoid(III) (Ln) with 2-thenoyltrifluoroacetone (Htta) in cyclohexane or benzene has been observed by the addition of tris(acetylacetonato)chromium(III) (Cr(acac)3). The equilibrium analysis suggested that the effect of Cr(acac)3 could be ascribed to the formation of a 1 : 1 adduct of Ln(tta)3 with Cr(acac)3, i.e., a binuclear complex, in the organic phase. The formation constants (βs,1) of the adducts were determined across the Ln series. The βs,1 values decreased with decrease in the ionic radii of Ln in the light Ln, and were constant in the heavy Ln. Spectroscopic studies such as electronic absorption, IR, and 1H NMR were performed to explain the difference between the light and heavy Ln. The adduct of light Ln is mainly an inner sphere complex in which Cr(acac)3 displaces the coordinated water of the Ln chelate and directly coordinates to the Ln ion. On the other hand, the adduct of heavy Ln is an outer sphere complex formed by the hydrogen bonding between Cr(acac)3 and the coordinated water of the Ln chelate. Abilities of Cr(acac)3 as a complex ligand, i.e., the basicity and the steric factor, were evaluated by comparing with Co(acac)3 reported previously.
Spectral, Kinetics, and Redox Studies on the Transients Formed on Pulse Radiolysis of Aqueous Solution of (4-Methylthiophenyl)methanol
Authors: Mohan Hari , Mittal Jai Pal
Published: November 2002

Pulse radiolysis technique has been employed to investigate the nature and the redox properties of the transient species generated on radiolysis of aqueous solution of (4-methylthiophenyl)methanol (MTPM). Pulse radiolysis in 1,2-dichloroethane, reaction with specific one-electron oxidants (Cl2•−, SO4•−, Tl2+, Br•) and reaction of •OH radicals in acidic solution showed absorption bands at 320 and 545 nm; these are assigned to solute radical cation with positive charge on the benzene ring. OH-adduct was observed in neutral solution. The oxidation potential for MTPM/MTPM•+ couple is determined to be 1.55 ± 0.04 V vs NHE. eaq− reacts with a bimolecular rate constant of 1.5 × 109 dm3 mol−1 s−1 and the transient absorption bands (λmax = 320, 470 nm) are assigned to the solute radical anion. E0 value for MTPM/MTPM•− couple is determined to be −1.84 ± 0.04 V vs NHE. The redox properties of the transient species formed on reaction with •OH, •H, and O•− have been evaluated.
Synthesis and Biological Activity of 3,7-Anhydro-2,4-dideoxy-4-[(R)-3-hydroxytetradecanoylamino]-6-O-phosphono-5-O-[(R)-3-(tetradecanoyloxy)tetradecanoyl]-d-glycero-d-ido-octonic Acid Derivatives
Authors: Wakabayashi Takanori , Shiozaki Masao , Kanai Saori , Kurakata Shin-ichi
Published: November 2002

d-Glucosaminylacetic acid derivatives (10, 11 and 12) of GLA-60 were synthesized to investigate the LPS-antagonistic activity toward human monoblastic U937 cells. Compounds 10 and 11 show weak LPS-antagonistic activity, but 12 shows both LPS-antagonistic and -agonistic activities, depending on the concentration.
Asymmetric Synthesis of β-Amino-α-Hydroxy Acids through Lewis Acid-Mediated Addition of Ketene Acetal to Imines
Authors: Ha Hyun-Joon , Ahn Young-Gil , Woo Jun-Sik , Lee Gwan Sun , Lee Won Koo
Published: November 2002

Asymmetric synthesis of β-amino-α-hydroxy acids, key components of medicinally important molecules including Paclitaxel, KRI-1314, amastatin, and microginin, has been attained from the aldimine coupling of chiral imines N-alkylidene-(S)- or (R)-α-methylbenzylamine with (Z)-α-methoxyketene methyltrimethylsilyl acetal, followed by demethylation, hydrogenolysis, and hydrolysis.
Trifluoromethyl-Substituted Donor–Acceptor Norbornadiene, Useful Solar Energy Material
Authors: Nagai Takabumi , Fujii Kazuhisa , Takahashi Ikuko , Shimada Miwa
Published: November 2002

Trifluoromethyl (CF3)-substituted donor–acceptor norbornadiene (NBD) derivatives were synthesized. The photoisomerization of CF3-NBD derivatives proceeded smoothly. The thermal stability of quadricyclane (QC) derivatives obtained from CF3-NBD derivatives was examined, and it was found that the CF3 group increased the thermal stability of the QC derivatives. Furthermore, CF3-NBD derivatives exhibited efficient fatigue resistance.
O2-Binding Properties of Double-Sided Porphinatoiron(II)s with Polar Substituents and Their Human Serum Albumin Hybrids
Authors: Komatsu Teruyuki , Okada Tomoyuki , Moritake Miho , Tsuchida Eishun
Published: November 2002

Double-sided porphinatoiron(II)s with polar substituents [R; hydroxy (FeDP(OH)), methoxy (FeDP(OMe)), and acetoxy (FeDP(OAc))] on the 2,2-dimethylpropanoyloxy-fence groups have been synthesized. FeDP(OMe) and FeDP(OAc) formed five-N-coordinated high-spin Fe2+ complexes with an intramolecularly bound axial imidazole in toluene (or CH2Cl2) under an N2 atmosphere. Upon the addition of O2, they produced stable O2 adducts at 25 °C; their half-lives in water-saturated toluene (50–77 h) are 2–3 fold longer compared to that of the single-face encumbered porphinatoiron(II) (FeP). Their O2-binding parameters are almost identical to that of FeDP(H), which has nonpolar substituents on the fences. In contrast, FeDP(OH) showed a significantly low O2-binding affinity and was immediately oxidized to the Fe3+ state after contact with bubbling O2 gas. The incorporation of these FeDPs into the human serum albumin (HSA) provided artificial hemoproteins, which can reversibly bind and release O2 under physiological conditions (in aqueous media, pH 7.3, 37 °C) like hemoglobin and myoglobin. The half-life of the dioxygenated HSA–FeDP(H) reached 5 h (37 °C). This corresponded to a 2.5-fold increase compared to that of HSA–FeP. The time dependences of the absorption changes accompanying the O2- and CO-rebindings to the HSA–FeDPs after laser flash photolysis were composed of two phases. These observations indicate that the recombination of O2 and CO to the central Fe2+ ion is affected by the microenvironments around the FeDPs in the HSA structure, e.g. a steric hindrance of the amino acid residue and a difference in polarity. Furthermore, FeDP(H) incorporated into HSA showed a high stability against H2O2.
Iron(II) Complex of Octopus-Porphyrin with a Covalently Linked Proximal Imidazole; Self-Assembly and O2-Coordination in Aqueous Media
Authors: Komatsu Teruyuki , Hayakawa Shoichi , Yanagimoto Tetsuya , Kobayakawa Makiko , Nakagawa Akito , Tsuchida Eishun
Published: November 2002

The iron complex of tetrakis[2,6-di(alkanoyloxy)phenyl]porphyrin derivative with seven phosphocholine head groups and an N-alkylimidazole side-chain as the proximal base (octopus-porphyrin) has been synthesized. The ferrous complex (7b) was easily dispersed in water to provide a stable colloid. Transmission electron microscopy and scanning force microscopy of the evaporated solution showed spherical micelles with a diameter of 8 nm, which probably consists of a dimer of 7b. These micellar aggregates could reversibly coordinate O2 at 25 °C; and the O2-binding parameters are also given.
Solid-State and Solution Structures of Calix[4]arene Tetramethyl Ether Containing Four Diphenylphosphino Moieties at the Upper Rim
Authors: Takenaka Kazuhiro , Obora Yasushi , Jiang Li Hong , Tsuji Yasushi
Published: November 2002

X-ray crystallographic analysis and CPMAS solid-state NMR measurements of tetrakis(diphenylphosphino)calix[4]arene tetramethyl ether (1) elucidated that in the solid-state 1 adopts a flattened partial cone conformation having C1 symmetry. In solution, on the other hand, the 1H, 13C, and 31P NMR spectra measured at −20 °C indicated that 1 has a partial cone conformation with a mirror plane. Two-dimensional 31P EXSY and variable-temperature 31P NMR spectra reveal a fluxional behavior of 1 in solution on the NMR time scale due to annulus rotation from the methoxy side. Concerning the energetics for the four conformers of 1, an ab initio molecular orbital calculation showed that the partial cone conformation is the most stable form, while the cone and the 1,3-alternate conformers are only slightly less stable.
Silyl-Substituted Dithioles as Candidates for New Electron Donors
Authors: Li Hongqi , Nishiwaki Keiji , Itami Kenichiro , Yoshida Jun-ichi
Published: November 2002

Molecular orbital calculations revealed that the introduction of a silyl group onto the 2-position of 1,3-dithiole caused significant decrease of the ionization potential and that 2-silyl-1,3-dithioles served as a pseudo π-electron system. The silyl group could also be utilized as a bridge for linking π-electron systems to achieve artificial stacking. These concepts led us to the design and synthesis of silyl-substituted 1,3-benzodithioles as candidates for new electron donors. The oxidation potential of monosilyl-substituted 1,3-benzodithiole was found to be significantly less positive than that of the parent 1,3-benzodithiole. The introduction of the second silyl group caused further decrease of the oxidation potential. Compounds composed of two 1,3-benzodithiole units linked by a silyl group were also synthesized. These showed comparable oxidation potentials to those of the corresponding monomeric compounds. The effect of stannyl-substitution onto the 2-position of 1,3-dithiole was found to be larger than that of silyl-substitution. The effects of silyl- and stannyl-substitution for related systems such as thioanisole and 1,3-dithiane were also studied.
Iridium-Catalyzed Reaction of 1-Naphthols, N-(1-Naphthyl)benzenesulfonamides, and Salicylaldehyde with Internal Alkynes
Authors: Nishinaka Yuko , Satoh Tetsuya , Miura Masahiro , Morisaka Hideaki , Nomura Masakatsu , Matsui Hisaji , Yamaguchi Chiharu
Published: November 2002

1-Naphthols efficiently couple with internal alkynes via cleavage of the C–H bond at the peri-position in the presence of a catalyst system of [IrCl(cod)]2/PBut3 to selectively afford the corresponding 8-vinyl-1-naphthol derivatives. N-(1-Naphthyl)benzenesulfonamides can similarly react with the alkynes. The reaction of salicylaldehyde with the alkynes using the catalyst system gives 2-hydroxyphenyl vinyl ketones via cleavage of the aldehyde C–H bond.
Oxidation of Ferrocenyl End-Substituted Oligothiophenes
Authors: Sato Masa-aki , Sakamoto Mune-aki , Kashiwagi Shin-ichiro , Suzuki Tomohiro , Hiroi Masao
Published: November 2002

A ferrocenyl end-substituted terthiophenes derivative and a sexithiophene derivative were prepared as model compounds for a molecular wire. Electrochemical measurements and absorption spectroscopy were performed to elucidate the oxidation process and the oxidized states of those model compounds. The first oxidation of the model compounds took place in the ferrocene moieties (terminals). The resultant oxidized species in the ferrocene moieties seeped into the oligothiophene moieties (wires) and spread over two or three thiophene rings. Further oxidation of the ferrocenyl-terthiophene derivative did not occur, whereas that of the ferrocenyl-sexithiophene derivative produced an oxidized species, such as a cation radical in the sexithiophene moiety.
Total Synthesis of the Novel Spider Toxin NPTX-594 from Nephila madagascariencis
Authors: Wakamiya Tateaki , Yamamoto Akinori , Kawaguchi Keita , Kinoshita Tomohiko , Yamaguchi Yoshihiro , Itagaki Yasuhiro , Naoki Hideo , Nakajima Terumi
Published: November 2002

A novel spider toxin, NPTX-594, comprised of four constituents: i.e., 2,4-dihydroxyphenylacetic acid (Dhpa), asparagine, 4,8-diaza-1,12-dodecanediamine (Dada), and lysine, was chemically synthesized. The synthetic compound was completely identical with the natural product as regards 1H NMR and mass spectra. The structure of NPTX-594 was thus determined synthetically to be N12-(Dhpa-Asn)-N1-Lys-Dada, as proposed by spectrometric elucidation.
Chemical Composition Distribution of Biosynthesized Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Determined by Temperature Rising Elution Fractionation
Authors: Kawai Tadatomo , Teramachi Shinya , Yokoyama Takamitsu
Published: November 2002

The chemical composition distributions (CCDs) of biosynthesized poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-co-3HV), samples with different average compositions were determined by temperature rising elution fractionation (TREF). P(3HB-co-3HV) samples were supplied by Sigma–Aldrich Co. Inc. According to catalog data, the 3HV contents were about 8, 14, and 24 mol%, respectively. The TREF condition was as follows: the sample concentration was 0.3% dissolved in acetonitrile at 75 °C; the column temperature was slowly (2 °C/h) decreased from 75 °C to 0 °C to crystallize the sample. The fractions were eluted with acetonitrile by stepwise increasing the temperature by 5 °C.

The chemical compositions of the original samples and the fractions were determined by 1H NMR. Cumulative CCD curves were constructed from the fractionation data for the respective samples. It became clear that these samples had bimodal CCDs with two discrete peaks, that is, one part in the wide composition range around 10–15 mol% of 3HV contents and another part at different compositions.
Positive-Tone Imaging of Photo-Decomposable Polymer LB Films
Authors: Li Tiesheng , Mitsuishi Masaya , Miyashita Tokuji
Published: November 2002

We describe the lithographic properties of poly(N-isopentylmethacrylamide-co-t-butyl 4-vinylphenyl carbonate) [p(iPMA-tBVPC)] which has a structure that is subject to the main chain scission and to deprotection of t-butoxycarbonyloxy group by deep UV irradiation. The positive-tone patterns of the p(iPMA-tBVPC) LB film with 60 layers could be obtained by deep UV light irradiation, followed by development with alkaline aqueous solution. The resolution of the pattern was 0.75 μm, which is the resolution limit of the photomask employed. The photopattern formation with the copolymer [p(iPMA-tBVPC)] LB film was more sensitive than the homopolymer poly(N-isopentylmethacrylamide) [p(iPMA)] LB film. The etching resistance of the p(iPMA-tBVPC) LB film deposited for the pattern of the gold film is also investigated.
First Synthesis of Both “Head-to-Head” and “Head-to-Tail” Polyimides Using a Common Unsymmetric Alicyclic Tetracarboxylic Dianhydride
Authors: Li Jun , Shiraishi Shinsaku , Kudo Kazuaki
Published: November 2002

A structurally ordered polyimide with the main chain having the complete “head-to-tail” bonding sequence (HTPI) or the complete “head-to-head” bonding sequence (HHPI) was prepared. The synthesis was based on the unique reactivity of an unsymmetric spiroalicyclic tetracarboxylic dianhydride, rel-(1R,5S,6R)-spiro[3-oxabicyclo[3.2.1]octane-6,3′-tetrahydrofuran]-2,2′,4,5′-tetrone (DAn), which has one 5-membered and one 6-membered anhydride. Equimolar amount of amine reacts with this compound predominantly at the 6-membered ring. Thus, the reaction of DAn with 1 molar amount of 4-nitroaniline and the subsequent methanolysis and reduction gives a monomer for a head-to-tail polyimide, which was successfully converted to HTPI through a polycondensation-dehydration sequence. Additionally, a new dianhydride monomer MHH, which is a 2 : 1 adduct of DAn and p-phenylenediamine (PPD), was prepared. MHH was subjected to polycondensation with 1 molar amount of PPD and the condensate was dehydrated to give HHPI. Slow addition of PPD into the solution of DAn also afforded a semi head-to-head polyimide. The polyimides had inherent viscosity in the range of 0.20–0.73 dL/g and were characterized by NMR and IR spectra through a comparison with those of their random isomer RPI. No obvious differences in properties, such as solubility and thermal stability, between the ordered polyimides (HTPI and HHPI) and the random counterpart were found in this study.
Infrared Spectroscopic Study of Water–Aromatic Hydrocarbon Mixtures at High Temperatures and Pressures.
Authors: Furutaka Seiya , Kondo Hitomi , Ikawa Shun-ichi
Published: November 2002

This paper reviews recent infrared studies on water–aromatic hydrocarbon mixtures. It mainly deals with infrared absorption of HDO in hydrocarbons measured as a function of temperature and pressure in the 373–648 K and 100–350 bar ranges, respectively. The intensity ratio of a hydrogen-bonded OH band to a hydrogen-bond-free OH band increases with increasing temperature. This fact indicates that the rate of increase in water solubility in the hydrocarbons is large enough to surmount the entropy effect which is unfavorable to water–water association. A good correlation between the peak frequency of the hydrogen-bond-free band and ionization potential of solvent hydrocarbons suggests that the concept of π-hydrogen bonding between water and aromatic hydrocarbons is useful even at high temperatures and pressures. At higher temperatures, the two OH bands mentioned above merge into a single band, which suggests that a water molecule rotates rather freely even in a hydrogen-bonded water cluster at high enough temperature. Water concentration and density of a hydrocarbon-rich phase are estimated from infrared intensities. Both of them show remarkable pressure dependence near an extended line of the three-phase coexistence curve in the phase diagram. This behavior should be characteristics of fluid mixtures near the critical region.
Synthesis, Optical, and Conductive Properties of Long Oligothiophenes and Their Utilization as Molecular Wires
Authors: Otsubo Tetsuo , Aso Yoshio , Takimiya Kazuo
Published: November 2002

This account reviews the current development of extraordinarily long oligothiophenes involving the 48-mer and 72-mer, which correspond to mono-disperse polymers. The systematic studies of the homologous series have provided valuable information on the optical and conductive properties of α-conjugated thiophene systems: an effective conjugation length extends to around 20 thiophene units in the neutral state and around 30 thiophene units in the oxidation state; this length plays a critical role in determining the electronic structures and conductivities. In addition, the active charge carrier species are both π-dimers and chain dimers, and charge transport occurs through the transfiguration of both species. This account also describes how useful oligothiophenes are as molecular wires allowing photoinduced electron- and/or energy-transfer. The molecular-wire behaviors of sophisticated oligothiophenes that are functionalized with a donor unit and an acceptor unit at the terminal α-positions are demonstrated.
Experimental Studies on Complex Oscillations in a Mn2+-Catalyzed Acidic Bromate–Glucose Reaction
Authors: Li Hexing , Wang Qin
Published: November 2002

Under batch-reactor conditions, the BrO3−–glucose–Mn2+–H2SO4 system exhibits several types of oscillations, depending on the concentrations of the reactants. In certain cases, dual-frequency oscillations are observed owing to a sequential appearance of different types of oscillations. Since glucose is not subject to bromination, these oscillations may be considered as being typically radical-controlled, and can be distinguished from bromide-controlled oscillations by adding acetone, which also results in dual-frequency oscillations due to the presence of both radical-controlled and bromide-controlled oscillations. Further experimental results demonstrate that the different types of oscillations observed in the absence of acetone can be possibly attributed to the Mn2+-catalyzed reactions between bromate and glucose, or various intermediates produced from the oxidative degradation of glucose. The effects of the [BrO3−]/[glucose] ratio and [H2SO4] on the oscillatory behaviors are discussed on the basis of their effects on either the depth of oxidative degradation of glucose or the oxidizing ability of bromate.
Photoexcited State Properties of Silicon Phthalocyanine Monomer, Dimer, and Trimer
Authors: Fujitsuka Mamoru , Ito Osamu , Konami Hideo
Published: November 2002

Properties of the excited states of silicon phthalocyanine monomer and its coplanar-stacked dimer and trimer have been investigated. Absorption bands of the oligomers showed blue-shift due to exciton coupling. Weak fluorescence bands of the dimer and trimer appeared in the near-IR region. The lifetimes of the singlet excited states of the dimer and trimer were estimated to be 196 and 53 ps, respectively, from the absorption-time profiles of the singlet excited states. The T–T absorption bands showed decays according to the intermolecular T–T annihilation processes. The rate constants for the intermolecular T–T annihilation processes were one-order smaller than the diffusion-limiting rates of the solvents, indicating some steric hindrance by the substituted group at the axial position. The quantum yields for the intersystem crossing processes of the dimer and trimer were quite small compared to that of the monomer. These findings indicate the extensive contribution of the non-radiative processes in the excited states of the dimer and trimer. The energy transfer rate constants between of the triplet excited phthalocyanines and O2 decreased in the order of monomer > dimer > trimer. The small rate constants of the dimer and trimers can be attributed to the lower triplet energy levels of the dimer and trimer compared to that of the monomer.
Realization of Three-Dimensional Solvation-Structures from the Site–Site Radial Distribution Functions in Liquids
Authors: Sato Hirofumi , Hirata Fumio
Published: November 2002

We propose a new procedure to realize a three-dimensional (3D) solvation structure around a solute molecule from a set of radial distribution functions (RDF), or distance information. The method consists of the minimization of a penalty function defined as the mean-square difference of the solute–solvent interatomic distances obtained from trial 3D configurations and from target RDFs. The hydration structures around several different solute molecules are visualized to demonstrate the method.

The solvation structures realized with the present method correspond to the most plausible solvation structure (MPSS), which looks like a “snap shot” of the molecular dynamics trajectory. However, the MPSS is essentially different from the “snap shot,” since it represents an average configuration, and is therefore an observable quantity. The present procedure was originally developed for analyses of the RDF results obtained from the reference interaction site model (RISM), but can be applied straightforwardly to RDFs from other sources, such as molecular simulations and scattering experiments.
Effect of Additives on the Stability of Pd/Al2O3 for Carbon Dioxide Reforming of Methane
Authors: Nagaoka Katsutoshi , Aika Ken-ichi
Published: November 2002

The effect of additives such as alkaline earth metal (Ca and Ba) and rare earth metal (La and Ce) oxides to Pd/Al2O3 catalyst for the CH4/CO2 reforming was investigated at 1023 K under 0.1 MPa in terms of catalytic stability and coke deposition. Catalytic stability of Pd/Al2O3 was improved by all additives; the rare earth metal oxides were more effective than the alkaline earth metal oxides. Temperature programmed hydrogenation (TPH) for those catalysts after exposure to CH4/CO2 showed that rate of coke deposition (deactivating catalysts), probably due to CH4 decomposition, was in the order: Pd/Al2O3 > Ba/Pd/Al2O3 >> La/Pd/Al2O3, being in accordance with the catalytic stability. Temperature programmed oxidation (TPO) showed that rate of CH4 decomposition was in the order: Pd/Al2O3 > Ba/Pd/Al2O3 > La/Pd/Al2O3. Further, the peak on La/Pd/Al2O3 was observed at lower temperature than on the others during the TPO, implying that the reaction between CHx and CO2 on La/Pd/Al2O3 occurs more easily than on the others. Therefore, the (slow) decomposition of CH4 and the (fast) removal of the CHx would be balanced on Pd/Al2O3 with the rare earth metal oxides. Thus the catalysts do not show significant coke deposition and keep stable activity for a long time during the CH4/CO2 reforming.
Theoretical Conformational Analysis of the Tandem Repeat Sequence in RNA Polymerase II
Authors: Ohiso Isao , Oka Masahito , Nishi Norio
Published: November 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. A theoretical conformational analysis based on molecular mechanics using the energy functions of ECEPP was carried out for a heptapeptide in the repeating unit (Ac-Ser-Pro-Thr-Ser-Pro-Ser-Tyr-NHMe) and a periodic polyheptapeptide corresponding to the tandem repeat sequence (Ac-(Ser-Pro-Thr-Ser-Pro-Ser-Tyr)16-NHMe). The minimum conformations of Ac-Ser-Pro-Thr-Ser-Pro-Ser-Tyr-NHMe had two turn structures, an open turn at Pro2-Thr3 and a γ -turn at Pro5. The contiguous residues to the turns are extended or semi-extended conformations. The low-energy conformations of Ac-(Ser-Pro-Thr-Ser-Pro-Ser-Tyr)16-NHMe were long-periodic helices with a large number of residues per turn. Their helical radiuses are approximately 10–13 Å. They mostly have tyrosyl side-chains at the helical interior. They are composed of alternative backbone conformations, which are extended and turn structures, patterned on the feature of the low-energy conformations of Ac-Ser-Pro-Thr-Ser-Pro-Ser-Tyr-NHMe. It was shown that the long-periodic helices contain turn structures as possible conformations of the C-terminal domain.
Hydration of Glucose and Galactose Derivatives
Authors: Uedaira Hisashi , Okouchi Shoichi , Tsuda Sakae , Uedaira Hatsuho
Published: November 2002

The spin-lattice relaxation times, T1, of H217O have been measured for aqueous solutions of glucose and galactose derivatives, which are substituents of the 2-OH or 6-OH of these sugars, as a function of the concentration at 25 °C. The values of the coordination numbers, nh, have been estimated on the basis of the water-accessible surface areas (ASA) of the solute molecules. The rotational correlation times, τch, of water molecules around the solute were estimated and compared with that of pure water, τc0. All values of the τch/τc0 for the derivatives were smaller than those of the parent sugars, and the value of τch/τc0 = 1.26 for glucosamine was the smallest among these derivatives. The greater the hydration of the parent sugars is, the more the hydration layer will be disturbed by the substituted groups.
Solvent Density and Species Dependence of the Fluorescence Stokes-Shift and Lifetime of Coumarin 152
Authors: Kimura Yoshifumi , Iwasa Masaki , Hirota Noboru
Published: November 2002

Absorption spectra, fluorescence spectra, and fluorescence lifetime of Coumarin 152 (C152) have been measured in ethane (C2H6), carbon dioxide (CO2), and trifluoromethane (CF3H) at 343 K and in CF3H at 323 K from ρr ≈ 0.1 to 2.0. The fluorescence Stokes-shift slightly decreases in C2H6 and CO2 with an increase of the solvent density, while it increases up to ρr ≈ 0.5 in CF3H and remains almost constant above ρr ≈ 0.5, where ρr is the reduced density by the solvent critical density. All these features are common to the case of C153 (Y. Kimura and N. Hirota, J. Chem. Phys., 111, 5474 (1999)). The fluorescence lifetime of C152 is found to be strongly dependent on the solvent density and temperature below ρr = 1.0 in C2H6. On the other hand, very large density dependence is observed in CF3H below ρr = 0.1, although the lifetime slightly decreases with increasing the solvent density above ρr = 0.1. The fluorescence lifetime is discussed in relation with the energy difference between the S0 and S1 states. The quenching of the S1 state by oxygen is also found to make a contribution to the density dependence of the fluorescence lifetime.
Mechanisms of Oxidation Reactions of Iodide and Hexacyanoferrate(II) Ions, Induced by the Reaction between Phosphinate Ion and Molecular Oxygen in an Aqueous Solution
Authors: Kimura Masaru , Ieyama Noriko , Matsumoto Masami , Shimada Kimiko , Tsukahara Keiichi
Published: November 2002

When an I− solution was mixed with a PH2O2− solution which had been kept standing for given times of 5–40 min in the presence of molecular oxygen (O2), the I2 (or I3−) was rapidly formed and then gradually reduced. The maximum amounts of the formed I2 (or I3−) increased with increasing standing times of the PH2O2− solution, and with increasing concentrations of PH2O2− and H+ in the solution. When the [Fe(CN)6]4− solution was mixed with the PH2O2− solution, [Fe(CN)6]3− was formed quantitatively, but an induction period appeared under the conditions of low concentrations of PH2O2− and high pH’s. The induction period was shortened at higher concentrations of PH2O2−, O2, and/or H+. Both oxidation reactions of I− and [Fe(CN)6]4− were extremely accelerated by the addition of small amounts of the peroxodiphosphate salt (K4P2O8) into the solution, both were inhibited by the presence of radical scavengers, and never occurred in the N2-saturated solution. The mechanisms for such O2-induced/radical reactions, which are regarded as a new type of Fenton-like reagent, are discussed.
Water Molecules in Organic Solvents Involved in the Synergistic Extraction of Europium(III) with β -Diketones and Lewis Bases
Authors: Hasegawa Yuko , Nakaya Kiyotaka , Matsubayashi Izuru
Published: November 2002

To explain the difference in the magnitude of synergistic extraction among organic solvents, the water solubility in hexane, carbon tetrachloride, benzene, and chloroform was measured, and then the residual hydration number of europium(III) in the β-diketonato chelate and in their adducts with 1,10-phenanthroline as well as the adduct formation constants were determined. Using the data, the formation constants of the adduct according to a novel definition, in which the water concentration in the organic phase is treated as one variable, were determined. The constants are approximately constant irrespective of the organic solvents, although those according to the conventional definition are different among the solvents. It has been concluded that one of the most important factors controlling the magnitude of synergistic effects is the presence of water, such as the water content dissolved in organic solvents, and the hydration and dehydration of the relevant species, because water molecules compete with a Lewis base in complexation to the metal(III) chelates in the organic solvents.
Axial Hydration and Adsorption of Chloro(5,10,15,20-tetraphenylporphyrinato)manganese(III) at the Toluene/Water Interface, Studied by External Reflection Spectrophotometry
Authors: Fujiwara Kazuhiko , Watarai Hitoshi
Published: November 2002

Interfacial adsorption of chloro(5,10,15,20-tetraphenylporphyrinato)manganese(III), [Mn(tpp)Cl], at the interface of toluene/aqueous sodium hydrogensulfate was studied by means of an UV/vis external reflection (ER) spectroscopy and interfacial tension measurements. The s-polarized ER spectrum showed higher sensitivity than the p-polarized one at the incident angle of 70.8°. A linear correlation sililar to Beer’s law was obtained between the s-polarized ER absorbance and the interfacial concentration determined from the interfacial tension. The molar ER coefficient at the maximum wavelength of 478 nm was determined as −8.41×105 (mol−1 dm2). The effect of chloride ion concentration on the ER spectra suggested that the interfacial species at toluene/0.1 mol dm−3 sodium hydrogensulfate solution (pH 1.7) was Mn(tpp)(H2O)+i. The interfacial adsorption could be analyzed according to the Langmuir isotherm; the equilibrium constant for the adsorption reaction of Mn(tpp)Clo + H2O →← Mn(tpp)(H2O)+i + Cl− was determined as 59.6. Furthermore, it was suggested that chloride ions were preferentially distributing at the diffuse layer under low chloride ion concentrations.
Synthesis, Stereochemistry, and Spin Transition of Heterometal Dinuclear Fe(II)–Cr(III) Complex Bridged by 3,5-Bis(pyridin-2-yl)-pyrazolate
Authors: Ni-iya Keiko , Fuyuhiro Akira , Yagi Takashi , Nasu Saburo , Kuzushita Kaori , Morimoto Syotaro , Kaizaki Sumio
Published: November 2002

We have synthesized and characterized a new heterometal dinuclear complex, [(nta)CrIII(μ-bpypz)FeII(picen)]BF4 (1), where nta = nitritotriacetate; bpypz− =3,5-bis(pyridin-2-yl)-pyrazolate; and picen = N,N′-bis-(2-pyridylmethyl)ethylenediamine. The X-ray structure of the Fe(II)–Cr(III)·H2O·3dmf demonstrated that this has a dinuclear structure with a highly distorted octahedron around a high-spin Fe(II) and intramolecular bifurcated three-centered hydrogen bonds between the carboxylate oxygens of the nta and an amine proton of the picen with an abnormal conformation. A magnetic susceptibility measurement and/or the Mössbauer spectra of 1 substantiated a gradual spin-transition from 130 K to 300 K in a heating process centered around 250 K with a small hysteresis dip in the Fe(II) complex. The spin-transition temperature of 1 is lower than that of the mononuclear complex, [FeII(picen)(Hbpypz)](BF4)2(2), resulting from the weaker ligand field of 1 with a distorted octahedron than that of 2.
Europium(III) Fluorescence Lifetime in Poly(methacrylic acid) Related to Its Conformational Transition
Authors: Takahashi Yoshio , Kimura Takaumi
Published: November 2002

The number of water molecules (NH2O) in the inner-sphere of Eu(III) complexed with poly(methacrylic acid) and poly(acrylic acid) was reported at various temperatures and α (degree of ionization) of these polyelectrolytes using laser-induced fluorescence spectroscopy. It is suggested that the conformational transition of poly(methacrylic acid) is reflected in the α dependence of NH2O.
Stereoselective Formation of trans-2,5-Disubstituted Tetrahydropyrans by Intramolecular Nucleophilic Substitution and a Computational Study at the AM1 Level
Authors: Takagi Ryukichi , Nishitani Hiroko , Takenami Sigeharu , Okada Kazumasa , Kojima Satoshi , Ohkata Katsuo
Published: November 2002

The synthesis of 2,5-disubstituted tetrahydropyrans bearing a hydrophobic moiety at the C5 position from (E)- and (Z)-7-hydroxy-6-substituted 2,3-unsaturated esters by way of intramolecular nucleophilic substitution proceeded with high stereoselectivity. A theoretical study at the AM1 level of the cyclization reaction suggested that the reaction is kinetically controlled and that the preferred path for the cyclization reaction proceeds via a transition state in which 1,3-diaxial-like repulsions are minimized to give the trans product in accordance with experimental results.
Characterizing Pressure Effects on Winding of the DNA Double Helix
Authors: Tang Guo-Qing , Kunugi Shigeru
Published: November 2002

In order to characterize pressure effects on DNA topological conformations in terms of supercoiling, DNA topoisomerase- and ligase-induced supercoiling assays were applied to analyze several DNA samples from different sources (DNA of bacteriophage φX174 RFI, plasmid pBR322, and pUC19). Pressure generally enhanced winding of the DNA double helix. The results were analyzed with respect to the linking number, the rotation angle, and the torsional energy factor (K). K describes the energy cost of increasing DNA linking by one unit; it appeared to decrease linearly with pressure elevations up to at least 180 MPa, which suggested a volume shrinkage with DNA supercoiling.
Synthesis and Conformational Studies on 3-o-Tolylhydantoins by NMR and Molecular Modeling: Dipole-π Attractions in Peptides and Proteins
Authors: Park Sang Hyun , Bose Ajay K
Published: November 2002

5-Pentafluorobenzyl-3-o-tolylhydantoin (2) was synthesized for reducing this π-electron density, and NMR studies have shown that we have succeeded in changing the conformation of 2 into an extended system instead of the folded conformation for the non-fluorinated compound, 5-benzyl-3-o-tolylhydantoin (1). Molecular modeling has also confirmed the extended structure for 2. An approach has been found for possibly modulating the physiological activity of peptides containing aromatic amino acids.
Oxidative Addition of Allylic Substrates to Coordinatively Unsaturated Ruthenium Compounds, [Ru(η5-C5Me5)(η-amidinate)]: Preparation, Structure Elucidation, and Catalysis of Novel Ruthenium (IV)-η3-Allyl Complexes
Authors: Kondo Hideo , Kageyama Akira , Yamaguchi Yoshitaka , Haga Masa-aki , Kirchner Karl , Nagashima Hideo
Published: November 2002

Oxidative addition reactions of allylic halides, acetates, and carbonates with [Ru(η5-C5Me5)(η-amidinate)] [amidinate: iPrNC(Me)=NiPr (1a), tBuNC(Ph)=NtBu (1b)], which shows signs of coordinative unsaturation, gave novel cationic π-allyl ruthenium(IV) species. The compounds [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X− were isolated by anion exchange of the products (X = PF6, BF4, BPh4), and were characterized by spectroscopic analysis. The crystallography of two of the [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X− revealed a four-legged piano stool structure in which two nitrogen atoms in the amidinate ligand and two carbon atoms in the η3-allyl ligands occupy the positions of four legs; the orientation of the η3-allyl ligand was endo. Although cyclic voltammograms of the precursor, [Ru(η5-C5Me5)(η-amidinate)], indicated possible oxidative addition of organic halides other than allylic halides to [Ru(η5-C5Me5)(η-amidinate)], only allylic halides gave the corresponding Ru(IV) products. The importance of prior coordination of the carbon-carbon double bond of allylic substrates was evidenced by NMR observation of the intermediate in the reaction of 1a or 1b with allyl acetate. Addition of nucleophiles such as PhLi, dimethyl methylsodiomalonate, and piperidine to the [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X− gave rise to allylation of these nucleophiles and regeneration of [Ru(η5-C5Me5)(η-amidinate)]. The reactions of allyl methyl carbonate with nucleophiles were also achieved by catalysis of either [Ru(η5-C5Me5)(η-amidinate)] or [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X−.