bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electro-Optical and Hydrodynamic Properties of Synthetic Polyribonucleotides in Solutions as Studied by Electric Birefringence
Authors: Tanigawa Masato , Yamaoka Kiwamu 
Published: July 2006

Abstract
The electro-optical and hydrodynamic properties of four synthetic polyribonucleic acids were clarified by electric birefringence methods which take the molecular-weight distribution into consideration. Parallel double-stranded helices, poly(adenylic acid)·poly(protonated adenylic acid), I, and poly(cytidylic acid)·poly(protonated cytidylic acid), II, are known to possess an electric permanent dipole moment, because the reversing-pulse electric birefringence (RPEB) signals of these duplexes exhibit dips upon pulse reversal. The RPEB signals of antiparallel double-stranded poly(adenylic acid)·poly(uridylic acid), III, and poly(guanylic acid)·poly(cytidylic acid), IV, show no dip; therefore, these polynucleotides have no permanent dipole moment. By analyzing the relaxation time of the birefringence decay signals, the axial translations of the polynucleotides per base-pair were determined to be 4.0 Å for I, 2.7 Å for III, and 2.4 Å for IV, respectively. By analyzing the dependence of the steady-state birefringence values on the electric-field strength, the magnitudes of the permanent dipole moments per unit length of I and II projected onto the helix axes were found to be ca. 0.4 debye Å−1. The electric properties unraveled by electric birefringence experiments were compared with calculations based on a recent Manning theory. An unsaturable induced dipole moment may result from the polarization of the Debye–Hückel ion-atmosphere, while a saturable induced dipole moment is probably caused by the polarization of counter ions that are condensed on the charged sites of a polyion. The experimental values deviate from calculated values at ionic strengths lower than 0.0001; hence, the Manning theory is not applicable in this region.
Interactions of Cu2+ and VO2+ Ions with Phosphatidylcholine Vesicular Membranes as Studied by the 1H NMR Paramagnetic Relaxation Method
Authors: Tanaka Hisao , Saito Harumi , Kawazura Hiroshi 
Published: July 2006

Abstract
The spin-relaxation effects of the paramagnetic ions Cu2+ and VO2+ on the protons of solvent water and lipids in phosphatidylcholine unilamellar vesicles were first observed in order to elucidate the details of the interactions in the membrane surface region. VO2+ ions gave higher rates of the effective paramagnetic relaxation induced by binding to a membrane while Cu2+ ions had a larger partition coefficient from water to the membrane phase. It is concluded that VO2+ occupies a binding site closer to the N-methyl groups in the polar-head network and less accessible to a cation, which causes stronger motional restriction to a bound cation, compared with the site occupied by Cu2+.
Electrical and Optical Properties of α-(BETS)2I3 and α-(BEDT-STF)2I3
Authors: Inokuchi Makoto , Tajima Hiroyuki , Kobayashi Akiko , Ohta Toshiaki , Kuroda Haruo , Kato Reizo , Naito Toshio , Kobayashi Hayao 
Published: July 2006

Abstract
The electrical and optical properties were studied concerning α-(BETS)2I3 and α-(BEDT-STF)2I3, which are isostructural to α-(BEDT-TTF)2I3. It has been shown that α-(BETS)2I3 and α-(BEDT-STF)2I3 undergo metal-insulator transitions at around 50 and 80 K, respectively, and that their electrical resistivities exhibit temperature dependences resembling that of α-(BEDT-TTF)2I3 under high pressure. The optical reflectance spectra of these salts show a two-dimensional nature of their electronic structures, and analyses of the spectral data show that the transverse inter-molecular interaction increases in the order α–(BEDT–TTF)2I3 &lt; α–(BEDT–STF)2I3 &lt; α–(BETS)2I3.
Binuclear Dioxomolybdenum(VI) Complexes of Flexibly-Bridged Hexadentate Tetraanionic Schiff’s Bases Derived from Methylene- or Dithio-bis(salicylaldehyde) and S-Methyldithiocarbazate or S-Benzyldithiocarbazate
Authors: Maurya Mannar R , Antony Deena C , Gopinathan Sarada , Gopinathan Changaramponnath 
Published: July 2006

Abstract
The flexibly-bridged hexadentate tetraanionic ligands, LH4 [LH4 = Schiff’s bases obtained by the condensation of methylene- or dithio-bis(salicylaldehyde) with S-methyldithiocarbazate and S-benzyldithiocarbazate], react with [MoO2(acac)2] in a 1 : 2 molar ratio in refluxing methanol to give complexes of the type [(MoO2)2L]. These complexes show an intense ν(Mo=O) band at 924—948 cm−1 and a broad but strong band at ca. 850 cm−1 due to weakened ν → Mo interactions. An oligomeric structure, in which each Mo(VI) ion achieves a pseudo-octahedral structure via M2)2L] reacts with monodentate ligands (D) like pyridine, 4-methylpyridine, and dimethylsulfoxide and forms six-coordinated complexes of the type [(MoO2)2L(D)2] which are monomers. Cyclic voltammetry measurements indicate that these MoVIO2 complexes are resistant to MoIVO reduction. → Mo interactions. An oligomeric structure, in which each Mo(VI) ion achieves a pseudo-octahedral structure via MoO → Mo bridging, has been suggested for these complexes. [(MoO → Mo bridging, has been suggested for these complexes. [(MoO
Observation of Nuclear Excitation by Electron Transition (NEET) in 197Au with a Nanosecond Stroboscopic Electron Spectrometer
Authors: Shinohara Atsushi , Saito Tadashi , Otozai Kiyoteru , Fujioka Hiromu , Ura Katsumi 
Published: July 2006

Abstract
Nuclear excitation by electron transition (NEET) was investigated on 197Au. It is expected for 197Au that the deexcitation of the K-shell ionized atoms would be accompanied by the nuclear excitation of the first excited level. Time spectra of 63-keV electrons emerging from a 197Au target after bombardment with 100-keV pulsed electron beam were measured with a specially designed nanosecond stroboscopic electron spectrometer. A decay component with a half-life of 1.9 ns was extracted from the electron time spectrum. The decay was attributed to the internal conversion electrons emitted from the excited 197Au nucleus as a consequence of the NEET process and the NEET probability was deduced to be P = (5.1 ± 3.6) × 10−5. The result was compared with several theoretical estimates.
Syntheses and Structural Characterization of Dinuclear and Trinuclear Iron(II) Complexes of Tridentate Thiolic Ligands with an NNS Donor Set
Authors: Mikuriya Masahiro , Kotera Takanori , Adachi Fumiya , Handa Makoto , Koikawa Masayuki , Okawa Hisashi 
Published: July 2006

Abstract
Thiolate-bridged complexes of iron(II) with 2-[(2-aminoethyl)amino]ethanethiol (HLa), 2-[(3-aminopropyl)amino]ethanethiol (HLb), and 2-[[2-(2-pyridyl)ethyl]amino]ethanethiol (HLc) — [Fe{Fe(La)2}2](ClO4)2·CH3OH (1), [Fe{Fe(Lb)2}2]Cl2·2CH3OH (2), and [Fe2(Lc)2(NO3)2] (3), respectively — have been synthesized and characterized by elemental analyses, and infrared and electronic spectroscopies as well as magnetic susceptibilities (80—300 K). The crystal structures of all of these complexes have been measured by single-crystal X-ray diffraction. Each of complexes 1 and 2 has a thiolate-bridged trinuclear iron(II) structure showing a linear arrangement of the three iron atoms with a geometry that may be described as Oh-Td-Oh. Complex 3 is a thiolate-bridged dinuclear iron(II) molecule, in which each iron atom is coordinated in a distorted octahedron. The electronic spectroscopic and magnetic properties are discussed in relation to the crystal structures.
Synergic Extraction Equilibrium of Mn(II) with 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedione and Neutral Multidentate Ligands, Such as Terpyridine and Tetraphenyldiphosphane Dioxide
Authors: Satake Saeko , Tsukahara Satoshi , Suzuki Nobuo 
Published: July 2006

Abstract
The extraction equilibrium of Mn(II) was clarified in novel synergic extraction systems using 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta) and neutral multidentate ligands, such as 2,2′ : 6′,2″-terpyridine (terpy) and tetraphenyldiphosphane dioxide (tpdpo), into benzene. No oxidation of Mn(II) and large synergic effect were observed both in the Htta–terpy and Htta–tpdpo systems, and quantitative extraction of Mn(II) was done, which was not attained with Htta only. Mn(II) was extracted as Mn(tta)2(terpy) in the Htta–terpy system, where only two nitrogen atoms of terpy would coordinate to Mn. In the Htta–tpdpo system, two species, i.e. Mn(tta)2(tpdpo) and Mn(tta)2(tpdpo)2, formed in the benzene phase, where tpdpo functioned as a unidentate ligand. The adduct formation constants (βs) and the synergic extraction constants (Kex,s) were obtained and compared with those of other related compounds.
Analysis of d–d Transitions in [Cr(CN)(NH3)5]2+ as Inferred from Polarized Optical Spectra and Angular Overlap Model Calculations
Authors: Urushiyama Akio , Itoh Mutsuyoshi , Schönherr Thomas 
Published: July 2006

Abstract
The polarized single-crystal absorption spectra of [Cr(CN)(NH3)5]Cl(ClO4) were measured for interconfigurational quartet (t2g3 → t2g2eg) and intraconfigurational doublet transitions (t2g3 → t2g3). The band splittings of the spin-allowed transitions, 4A2g → 4T2g,4T1g, were derived to 600—1000 cm−1 from a Gaussian band deconvolution of the σ and π spectra. At low temperature (77 K), more than 45 sharp bands could be detected in the intercombination band region of the lowest doublets (2Eg, 2T1g), which were completely assigned to the five possible zero-phonon transitions and corresponding vibronic sidebands. The vibrational frequencies due to the electronic ground state were obtained from the infrared spectrum and by measuring the emission lines under resonant excitation, providing us with a sufficient data base for a normal coordinate treatment of the pentaamminecyano cation. The d-energy level scheme is rationalized using the angular overlap model (AOM). Geometric parameters were obtained from an X-ray analysis of the chloride–perchloride salt, which shows a cation of approximately 4mm (C4v) site symmetry, consistent with a linearly coordinated cyano group. The AOM parameters evaluated for the CN- ligand show strong σ-antibonding (eσ = ca. 7500 cm−1) together with unusually larger π-bonding (eπ = ca. −900 cm−1), which both contribute to the extremely high value of the respective ligand field parameter Dq. The large splitting of the lowest doublet state, 2Eg (Oh), has been shown to originate from a low-symmetry effect in the treatment of interelectronic repulsion. The attributed tetragonal orbital expansion parameter (τ = 0.99) was calculated to be similar to values recently obtained for related pentaammineaniono complexes.
Antioxidant Activities of Aminophenols against Oxidation of Methyl Linoleate in Solution
Authors: Iwatsuki Misato , Komuro Erika , Niki Etsuo 
Published: July 2006

Abstract
The antioxidant activities of 48 kinds of aminophenols, chromanols, indoles, carbazoles, aromatic amines, and related compounds were assessed in the oxidations of methyl linoleate in acetonitrile solution induced by azo radical initiator. Chromanols, aminochroman and p-phenylenediamines exhibited strong antioxidant activity. Indole and carbazole did not act as antioxidant per se, but those having either amino or hydroxy group as substituent at the para position acted as potent antioxidant. Amino-substituted compounds were in general more potent than hydroxy-substituted ones. These results were interpreted by both polar and resonance effect.
Synthesis and Molecular Structure of [4][34](1,2,3,4,5)Ferrocenophane
Authors: Hisatome Masao , Watanabe Jun , Yamakawa Koji , Kozawa Kozo , Uchida Tokiko 
Published: July 2006

Abstract
A review of synthetic and structural studies of ferrocenophanes has led to the presumption that the intramolecular substitution of ferrocenophanepropionic acid gives a bridged product when “the distance” between the two carbons to be bridged is greater than 3.20 Å. According to this prediction, the bridging reaction of [4][32](1,2,4)ferrocenophane-5-propionic acid (“the distance”: ca. 3.5 Å) was carried out, and the expected bridged compound (13) was afforded. Subsequently, the construction of fourth and fifth bridges in [4][32](1,3,4)ferrocenophane (16) was attempted by applying the working hypothesis in order to obtain perbridged [4][34](1,2,3,4,5)ferrocenophane (5). Both bridging reactions occurred as expected, and the synthesis of 5 was achieved. The absorption spectrum of 5 showed d–d* absorption at an unusually short wavelength (λmax = 345 nm; ferrocene, 443 nm), which is the shortest value in ferrocene derivatives to our knowledge. The structure of 5 was determined by an X-ray diffraction method. Compound 5 crystallizes in a tetragonal system, space group 2d with unit-cell parameters of a = 14.574(4), c = 18.208(4) Å and Z = 8; its R value converged to 0.051 for 1315 reflections. The observed distance between the iron atom and the least-squares aromatic ring of 1.55(9) Å is the smallest among those of all observed multibridged ferrocenophanes. The conformation of the ferrocene moiety is exactly eclipsed, and the dihedral angle of the two rings is small (1.9°).
Stereoselective Allylation of 2-Formyl Amides or 3-Oxo Amides
Authors: Taniguchi Masahiko , Oshima Koichiro , Utimoto Kiitiro 
Published: July 2006

Abstract
Stereoselective allylation of 2-formyl amides or 3-oxo amides has been studied. Treatment of 2-formyl-N,N-dimethylpropanamide (1a) with allylzinc bromide gave 3-hydroxy-2,N,N-trimethyl-5-pentenamide as a stereoisomeric mixture (2a : 3a = 63 : 37). Meantime, the reaction of 1a with allyltrimethylsilane in the presence of Lewis acid such as EtAlCl2 or BF3·OEt2 afforded threo-adduct 2a exclusively. Whereas treatment of 2-benzoyl-N,N-dimethylpropanamide (PhCOCH(Me)CONMe2) with allylzinc bromide provided erythro-3-hydroxy-2-methyl-3-phenyl-5-hexenamide with high stereoselectivity, allylation with allylsilane in the presence of a catalytic amount of n-Bu4NF afforded stereoisomeric threo hydroxy amide exclusively.
Synthesis and Properties of Cationic Organopalladium Complexes. Remarkable Rate Enhancement in Olefin Insertion into the Palladium–Aryl Bond by the Generation of a Cationic Palladium Complex from trans-[PdBr(Ph)(PMe3)2]
Authors: Kawataka Futoshi , Shimizu Isao , Yamamoto Akio 
Published: July 2006

Abstract
By removing the bromide ligand in trans-[PdBr(Ph)(PMe3)2] (1) by AgBF4 in the presence and absence of pyridine, pyridine-coordinated and solvent-coordinated cationic complexes, trans-[PdPh(py)(PMe3)2]BF4 (2) and trans-[PdPh(solvent)(PMe3)2]BF4 (3), have been obtained. These cationic phenylpalladium complexes show much greater reactivities than do the parent neutral complex 1 toward olefins to give phenylated olefins by insertion followed by β-hydrogen elimination processes. Kinetic studies concerning the insertion of methyl acrylate into the phenyl-palladium bond have indicated that the reactions are first order in the phenylpalladium complexes and that addition of pyridine to a system containing 2 and methyl acrylate inhibits the insertion reaction of the olefin. The results suggest that the generation of a cationic arylpalladium complex with a vacant site is important for the olefins to be inserted.
Effects of the Solvent Dynamics and Vibrational Motions in Electron Transfer
Authors: Yoshihara Keitaro , Tominaga Keisuke , Nagasawa Yutaka 
Published: July 2006

Abstract
Recent theoretical and experimental progress concerning electron transfer (ET) in solution is reviewed by focusing on the mechanism of ET, which occurs much faster than solvation dynamics. Theories of ET in solution are briefly reviewed with particular emphasis placed on the relation to solvent dynamics. Experimental methods to investigate solvent polarization relaxation are described. Ultrafast intramolecular ET, which is found in back ET from the photo-induced charge-transfer state to the ground state, is described concerning highly polar betaines and mixed-valence compounds. Ultrafast intermolecular ET has been observed for the systems of various dyes in electron-donating solvents. A non-exponential process with a significant temperature dependence was observed in aniline. A faster ET with a single exponential decay as fast as 1013 s−1 was observed with no temperature dependence in a system of oxazine 1 in N,N-dimethylaniline. The ET rate constants of excited coumarins in electron-donating solvents drastically depend on the substituent groups of the coumarin. Relatively small Stokes shifts in steady-state fluorescence spectra of ultrafast reacting molecules in solution are evidence of a “chemical timing” effect; namely, the reaction occurs in a non-equilibrium configuration of the solvent. These experimental observations are explained in terms of the extended Sumi–Marcus theory, in which the effect of solvation dynamics and low- and high-frequency vibrational modes are taken into account.
Asymmetric Hydrosilylation of 1-Alkenes Catalyzed by Palladium–MOP
Authors: Uozumi Yasuhiro , Kitayama Kenji , Hayashi Tamio , Yanagi Kazunori , Fukuyo Emiko 
Published: July 2006

Abstract
Asymmetric hydrosilylation of simple terminal alkenes (RCH=CH2) with trichlorosilane at 40 °C in the presence of 1 × 10−3 or 1 × 10−4 molar amounts of palladium catalyst prepared in situ from [PdCl(η3-C3H5)]2 and (S)-2-diphenylphosphino-2′-methoxy-1,1′-binaphthyl ((S)-MeO-MOP) proceeded with unusual regioselectivity and with high enantioselectivity to give high yields of 2-(trichlorosilyl)alkanes together with a minor amount of 1-(trichlorosilyl)alkanes. Optically active alcohols, RCH(OH)CH3, were obtained by oxidation of the carbon–silicon bond. Regioselectivities for forming 2-silylalkanes over 1-silylalkanes and enantiomeric purities of alcohols are as follows: R = n-C4H9: 89/11, 94% ee (R). R = n-C6H13: 93/7 95% ee (R). R = n-C10H21: 94/6, 95% ee (R). R = PhCH2CH2: 81/19, 97% ee (S). R = PhCH2CH2CH2: 80/20, 92% ee (R). R = cyclo-C6H11: 66/34, 96% ee (R). A similar hydrosilylation of 1-alkenes, 4-pentenyl benzoate and 1,5-heptadiene gave corresponding 2-alkanols of 90% ee and 87% ee, respectively, the ester carbonyl and the internal double bond remaining intact.
Hydrocracking of Acenaphthene over a Sulfided Ni–Mo/Al2O3 Catalyst
Authors: Miki Yasuo , Sugimoto Yoshikazu 
Published: July 2006

Abstract
The selectivity of ring opening was investigated for the hydrocracking of acenaphthene under an initial hydrogen pressure of 6 MPa and in the temperature range from 390 to 450 °C. Major products were classified into the following six components: tetrahydroacenaphthylene, hexahydroacenaphthylene, perhydroacenaphthylene, ring opening products (bicyclic compounds and monocyclic compounds), alkylation products (tricyclic compounds of C13 or larger), and dimerization products (biacenaphthene and their hydrogenated compounds). Ring opening of acenaphthene proceeded via two routes: the direct ring opening of acenaphthene and ring opening after hydrogenation to hexahydroacenaphthylene. In the former reaction only 1-ethylnaphthalene was produced, while 1,8-dimethylnaphthalene and its hydrogenated products were not observed. In the latter reaction, on the other hand, two types of ring opening of a C–C bond adjacent to the benzene ring, the opening of a saturated five-membered ring to produce 1-ethyltetralin and the opening of a saturated six-membered ring to produce 1-propylindane, were observed.
Electrochemical Study of the Micellization of Hexadecylpyridinium Bromide in Binary Methanol–Water Mixtures
Authors: Alizadeh Naader , Gharibi Hossein , Shamsipur Mojtaba 
Published: July 2006

Abstract
A membrane electrode selective to hexadecylpyridinum bromide was used to study the micellization of the surfactant in various methanol–water mixtures at 25 °C. There is a linear relationship between log cmc and the weight percent of methanol in solvent mixtures. The degree of counter-ion dissociation at different solvent compositions is reported. The degree of methanol attachment was found to be 2.04. The charged phase-separation model was used to express the mechanism of the mixed micelle formation.
Structures of Bis(phenylthio/seleno)dibenzothio/selenophenes with Short Intramolecular S···S and Se···Se Contacts
Authors: Yasui Masanori , Murata Shin , Iwasaki Fujiko , Furukawa Naomichi 
Published: July 2006

Abstract
The crystal structures of 1-phenylsulfinyl-9-phenylthiodibenzothiophene (1), 1,9-bis(phenylthio)dibenzothiophene (2), 1,9-bis(phenylthio)dibenzoselenophene (3), and 1,9-bis(phenylseleno)dibenzoselenophene (4) have been determined by an X-ray method in order to investigate the existence of a short intramolecular S···S or Se···Se contact. The crystal data are: 1, C24H16OS3, Mw = 416.59, Monoclinic, P21/n, a = 9.980(4), b = 8.843(4), c = 21.933(9) Å, β = 92.20(4)°, V = 1934(1) Å3, Z = 4, R = 0.028, wR = 0.027 for 2899 observed reflections. 2, C24H16S3, Mw = 400.59, Monoclinic, P21/n, a = 17.862(2), b = 8.050(2), c = 13.549(2) Å, β = 95.74(1)°, V = 1938.4(5) Å3, Z = 4, R = 0.053, wR = 0.075 for 3251 refined reflections (R = 0.057 for 3256 observed reflections). 3, C24H16S2Se, Mw = 447.48, Monoclinic, P21/n, a = 17.899(4), b = 8.086(2), c = 13.631(2) Å, β = 96.33(2)°, V = 1960.8(7) Å3, Z = 4, R = 0.046, wR = 0.070 for 2818 refined reflections (R = 0.050 for 2822 observed reflections). 4, C24H16Se3, Mw = 541.27, Monoclinic, P21/n, a = 18.094(2), b = 8.1571(6), c = 13.723(1) Å, β = 96.51(1)°, V = 2012.4(3) Å3, Z = 4, R = 0.066, wR = 0.066 for 3095 refined reflections (R = 0.067 for 3096 observed reflections). The nonbonding distances between two S atoms of phenylthio groups are 3.016(1), 3.012(1), and 2.973(1) Å for 1, 2, and 3, respectively. The distance of Se···Se of 4 is 3.070(1) Å. These distances correspond to 82.0, 81.8, 80.8, and 76.8% of the sum of the van der Waals radii for 1, 2, 3, and 4, respectively. Dibenzothiophene frameworks show severe deformation based on the steric effect of the 1,9-disubstituents. The dihedral angles between the benzene rings and the thiophene/selenophene rings are 6.6—8.5°. Two S/Se atoms of the phenylthio/seleno groups deviate from the thiophene/selenophene ring by about 1 Å on the opposite sides from each other.
High-Resolution Solid-State 13C NMR Studies on Molecular Motions and Solid-State Polymerization of Octatetraynes
Authors: Hayamizu Kikuko , Okada Shuji , Doi Takanori , Kawanami Hajime , Kikuchi Naoto , Matsuda Hiro , Nakanishi Hachiro 
Published: July 2006

Abstract
The effects of monomer alignment on the solid-state polymerizations of five octatetraynes and a butadiyne to produce polydiacetylenes were studied. Structural relaxations of the resulting polymers were found to occur over long time intervals. Solid-state high-resolution 13C NMR spectra were observed for six symmetrical monomers having alkyl chains (C14H29) and side chains containing either urethane or p-toluenesulfonate and the derived polydiacetylenes (PDA’s). The spin-lattice relaxation times (T1) of the PDA’s were also measured. The alignment and mobility of the monomers, which are closely related to the solid-state polymerizability and structure of the resulting polymers, are reflected in the solid-state 13C NMR spectra of the monomers.
The PDA’s with urethane side chains were found to have slow structural relaxation. When the number of spacer methylenes between the acetylenic carbon and the urethane moiety is odd, a planar main-chain structure was assumed. It was found that PDA-4A’s having an odd number of spacer methylenes achieved a more homogeneous structure after long-term relaxation than a PDA-4A with an even number of spacer methylenes.