bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoinduced Electron Transfer from Cyclic Organogermanium Compounds to C60 Studied by Laser Flash Photolysis
Authors: Ito Osamu , Sasaki Yoshiko , Watanabe Akira , Mochida Kunio
Published: June 2006

The electron transfer from cyclic organogermanium compounds to photo-excited C60 in benzonitrile solution has been investigated by the 532 nm-laser flash photolysis with observation of the transient absorption bands in the near-IR region. The transient absorption band of the C60 triplet state (TC60*) appeared at 730 nm immediately after nanosecond laser exposure. With the decay of TC60*, the absorption bands of the radical anion of C60 appeared at 1070 nm, showing that the electron transfer takes place from organogermanium compounds to TC60*. The efficiencies and rates of the electron-transfer reactions vary with ring size of the germanium compounds.
A Simple New Method for Determining Diffusion Coefficients of Interacting Particles in Porous Silica and Gels
Authors: Sasaki Shigeo , Maeda Hiroshi
Published: June 2006

A new experimental method to measure the diffusion coefficients of interacting particles in porous silica is described. The diffusion behavior of NaNO3 from a porous silica sphere into a solution of NaCl was found to be very sensitive to the cross diffusion term when the concentration ratio of NaCl to NaNO3 was high. The diffusion behavior of NaCl, KNO3, and KI from the inside to the outside of the sphere was also examined. Theoretical equations to analyze the cross diffusion flows of interacting particles were derived. The cross diffusion coefficient of NaNO3 and NaCl as well as the diffusion coefficients NaNO3, NaCl, KNO3, and KI in porous silica were evaluated from the present experimental results. The obtained diffusion coefficients were found to be about one third of those in solution. The diffusion behavior of NaNO3, NaCl, KNO3, and KI from spherical polyacrylamide gel was also examined for comparison.
Hydration and Pressure Effects on the Inter- and Intramolecular Vibrations of Tetramethylpyrazine Crystals
Authors: Maehara Masayoshi , Suzuki Yoshio , Mizobe Hideki , Kawano Hiroshi , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi
Published: June 2006

The Raman active inter- and intramolecular vibrations of tetramethylpyrazine and trihydrated tetramethylpyrazine crystals were studied under various pressures between 1 atm and 5 GPa. The pressure effect on the Raman frequency due to the intermolecular vibrations indicates that a tetramethylpyrazine crystal undergoes phase transitions under about 1.2 and 2.2 GPa and a trihydrated tetramethylpyrazine crystal undergoes phase transition under about 3.5 GPa. The pressure effect on the Raman frequency due to the intramolecular vibrations indicates that the pressure-induced frequency shift for the skeletal vibrations of trihydrated tetramethylpyrazine is larger than the corresponding shift of unhydrated tetramethylpyrazine, while the shift for the characteristic vibrations of the methyl groups of trihydrated tetramethylpyrazine is smaller than the corresponding shift of unhydrated tetramethylpyrazine. These observations suggest that the attractive force induced by the hydration plays a considerable role in the intermolecular interaction under high pressure in the molecular crystal, in addition to the repulsive force. The change of electron distribution, which strengthens the chemical bonds of the pyrazine ring more strongly than the bonds in the methyl groups, takes place with increasing pressure.
EPR and ENDOR Study of Trigonal Bipyramidal Copper Complexes with a Nitrogen Donor Tripodal Ligand
Authors: Ehsan Muhammad Q , Ohba Yasunori , Yamauchi Seigo , Iwaizumi Masamoto
Published: June 2006

The characteristic features of the electronic structure of some trigonal bipyramidal (tbp) copper complexes of the quadridentate tripodal nitrogen donor ligands, tris(2-aminoethyl)amine (tren) and tris(2-dimethylaminoethyl)amine (trenMe6), with different ligands at the fifth coordination position of tbp were studied in a powder form doped in diamagnetic zinc complexes by EPR and ENDOR. EPR shows that the copper complexes of tren and trenMe6 have a ground state with a dz2 unpaired electron orbital, and that some of the complexes are distorted from a trigonal symmetry to rhombic, to the contrary to expectations from the molecular formula. It is shown that a small structural or ligand-field distortion would give a recognizable spectral deviation from trigonal symmetry. It should be noticed that the hyperfine couplings of all the coordinating nitrogen atoms in each complex were observed by ENDOR, and that they were useful for calrifying the characteristic features of the electronic structures of the tbp complexes. The ligand fields at the fifth coordination position of tbp affects all of the coordination bonds as well as the spin distribution among the ligands. These ligand field effects on the electronic structures are discussed in reference to the ligand field parameters obtained by an EPR analysis. It is also shown that the ENDOR analysis well predicts the sp ratios of the coordinating orbitals of nitrogens, consistent with those obtained from the X-ray structural data on the complexes.
Charge Distribution Dependent on the Chelating Ratio. [Co(μ-bpym)(dbbq)2] vs. [{Co(dbbq)2}2(μ-bpym)] (bpym = 2,2′-bipyrimidine; dbbq = 3,6-di-t-butyl-1,2-benzoquinone)
Authors: Jung Ok-Sang , Jo Du Hwan , Lee Young-A , Chae Hee Kwon , Sohn Youn Soo
Published: June 2006

The preparation and characterization of [Co(μ-bpym)(dbbq)2] and [{Co(dbbq)2}2(μ-bpym)] (bpym = 2,2′-bipyrimidine; dbbq = 3,6-di-t-butyl-1,2-benzoquinone) have been established. The temperature-dependent magnetic moments (100—400 K) and variable-temperature near-infrared (NIR) absorption spectra are presented to show that the title complexes exhibit an equilibrium via a catechol to a cobalt intramolecular electron transfer. At temperatures below 200 K the mononuclear complex [Co(μ-bpym)(dbbq)2] has a charge distribution of [CoIII(μ-bpym)(dbcat)(dbsq)] (dbsq = 3,6-di-t-butyl-1,2-semiquinonato; dbcat = 3,6-di-t-butylcatecholato), whereas at temperatures beyond 290 K the mononuclear complex is predominantly in the [CoII(μ-bpym)(dbsq)2] form. From 200—290 K a mixture of Co(III) and Co(II) redox isomers exists at equilibrium in the solid state. In particular, a thermal analysis of a solid sample of the mononuclear complex discloses that the transition for the Co(III)/Co(II) is accompanied by a change in the heat content of 36 kJ mol−1, which may be closely related to the band at 3878 cm−1, assigned as a dbcat to Co(III) charge transfer. In striking contrast, the dinuclear complex [{Co(dbbq)2}2(μ-bpym)] is locked in a charge distribution of [{CoII(dbsq)2}2(μ-bpym)] when the temperature is 100—400 K.
Conformation Control of Model Peptides by Metal Ions. A New Type of Turn Structure Found in [(Boc–Cys–Pro–Leu–Cys–Gly–Ala)Hg]
Authors: Yamamura Takeshi , Arai Masaya , Yamane Tsutomu , Ukai Takeshi , Ushiyama Masato , Hirota Hiroshi
Published: June 2006

The structure of [(Boc–Cys1–Pro–Leu–Cys4–Gly–Ala–OMe)Hg], 1, in DMF(-d7) and DMSO(-d6) solutions was studied by X-ray absorption fine structure (XAFS), rotating frame nuclear Overhauser effect spectroscopy (ROESY), distance geometry (DG), molecular dynamics (MD), and restrained molecular dynamics (RMD). The XAFS study clarified that the inorganic center of compound 1 adopts a linear coordination with r(HG–S) = 2.33 Å. The NMR experiment revealed 33 atom approximate distances for the 1H-1H pairs of the main chain loop, including the side chains of the cysteinyl residues (ROESY). By a complementary use of DG, plain MD, and RMD for distance information from NMR as well as XAFS, we established that compound 1 adopts a new type of hybridized turn structure. The compound has two hydrogen bonds, Cys1 S-Leu HN and Pro CO-Cys4 HN, among which the former is common to the core sites in proteins, Cysi–X–Y–Cysi+3/M2+ (Zn2+, Fe2+), whereas the latter is common to the mirror image of the γ turn structure in proteins.
PM3 Analysis of Nitrone Cycloadditions to Methyl 4,4,4-Trifluoro-2-butenoate
Authors: Tanaka Kiyoshi , Imase Tatsuya , Iwata Satoru
Published: June 2006

3,4-Dihydroisoquinoline N-oxide (1) cycloadded with methyl 4,4,4-trifluoro-2-butenoate at 20 °C to give a mixture of the cycloadduct with a 1,10b-cis-configuration, methyl (1R*, 2R*, 10bR*)-2-trifluoromethyl-1,5,6,10b-tetrahydro-2 H-isoxazolo[3,2-a]isoquinoline-1-carboxylate, and its stereoisomer with a 1,10b-trans-configuration in a ratio of 3 : 1. Nitrone 1 cycloadded with methyl 2-butenoate to afford the cycloadduct with a 1,10b-cis-configuration exclusively. The stereoselectivity in the cycloadditions was reproduced by calculations of the transition structures by the PM3 method.
Novel Reaction between 3,4,5,6-Tetrachloro-1,2-benzoquinone and Bis-azomethines
Authors: Aly Ashraf A , Mohamed Nasr K , Hassan Alaa A , Mourad Aboul-Fetouh E
Published: June 2006

3,4,5,6-Tetrachloro-1,2-benzoquinone (o-CHL) reacted with N,N′-dicyclohexyl-1,2-ethanediimine 1a to give a transient condensation product, which underwent [4 + 2]cycloaddition reaction with another molecule of 1a. In a different manner, utilizing N,N′ -diaryl-1,2-ethanediimines 1b,c as a dienophile led to an initial production of substituted o-CHL, followed by a [4 + 2]cycloaddition reaction with another molecule of 1b,c. A similar behavior was observed on the reaction of N,N′-di(alkyl/aryl)-p-xylenediimines 1a—f with the same acceptor.
Synthesis of Cadinanolide Type of Tricyclic α-Methylene-γ-lactone Using Intramolecular Cyclization of α-Trimethylsilylmethyl-α,β-Unsaturated Ester with Cyclic Ketone
Authors: Kuroda Chiaki , Ito Kunihito
Published: June 2006

Fluoride-promoted intramolecular cyclization of ethyl 6-(2-oxocyclohex-1-yl)-2-(trimethylsilylmethyl)hex-2-enoate afforded ethyl 2-(1-hydroxybicyclo[4.4.0]decan-2-yl)acrylate as the major product, together with tricyclic α-methylene-γ-lactone, a model compound of cadinanolides. The former product was also converted to γ-lactone. The cyclization reaction promoted by TiCl4 gave the hydroxy ester and its dehydrated product. Both Lewis acid- and fluoride-promoted cyclizations gave a trans-decaline system mainly. This stereoselectivity is completely different from that of Reformatsky cyclization observed by Dreiding and co-workers.
Interaction of Carbodiimide with Human Erythrocytes: Hemolytic Properties Induced by High Pressure, Heating, and Hypotonic Medium
Authors: Yamaguchi Takeo , Miyamoto Yoshiya , Terada Shigeyuki
Published: June 2006

The effects of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) on the hemolysis of human erythrocytes were examined. To hemolyze, the erythrocytes were exposed to high pressure (200 MPa), heating (52 °C), or a hypotonic medium. Upon EDC treatment, the hemolysis induced by high pressure or heating was completely suppressed, whereas osmotic hemolysis was enhanced. In EDC-treated erythrocytes, high-molecular-weight aggregates of membrane proteins were formed by cross-linking of the membrane with the cytoskeleton, in addition to that of membrane proteins themselves. In such a cross-linking reaction, however, iron(II) in hemoglobin and thiol groups in membrane proteins remained stable. Although phosphate transport via band 3 was considerably suppressed by EDC, the intracellular K+ concentration was almost constant. These results suggest that high-pressure- or heat-induced hemolysis, compared with osmotic hemolysis, is suppressed by a stabilization of the cytoskeletal network.
Sulfonylation and Phosphinylation of Olefinic Compounds with Radical Species Generated by the Oxidation of Sodium Sulfinates and Diphenylphosphine Oxide
Authors: Mochizuki Takashi , Hayakawa Satoshi , Narasaka Koichi
Published: June 2006

Sodium arenesulfinates are oxidized with manganese(III) 2-pyridinecarboxylate or ammonium cerium(IV) nitrates to generate sulfonyl radicals, which add to olefinic compounds to afford sulfonylated products in good yield. When 1-vinyl cyclic alcohols are used as sulfonyl radical acceptors, sulfonylation proceeds with ring-enlargement. Diphenylphosphinyl radical can also be generated by treating diphenylphosphine oxide with manganese(III) 2-pyridinecarboxylate and reacts with olefinic compounds, giving phosphinylated products.
Theoretical Study of the Electronic Structure of 2,2′-Bisilole in Comparison with 1,1′-Bi-1,3-cyclopentadiene: σ*–π* Conjugation and a Low-Lying LUMO as the Origin of the Unusual Optical Properties of 3,3′,4,4′-Tetraphenyl-2,2′-bisilole
Authors: Yamaguchi Shigehiro , Tamao Kohei
Published: June 2006

The purpose of this work is the theoretical elucidation of the origin of the unusually long UV-vis absorption maximum, λmax = 398 nm, of 3,3′,4,4′-tetraphenyl-2,2′-bisilole, which we have observed recently. Several semiempirical and ab initio calculations have been performed for some model compounds, silole and 2,2′-bisilole, in comparison with their carbon analogs, cyclopentadiene and 1,1′-bi-1,3-cyclopentadiene, respectively. The PM3 calculations indicate that the silole ring has a considerably low-lying LUMO, arising from σ*–π* conjugation between a π-symmetry σ* orbital of the exocyclic σ bonds on silicon and a π* orbital of the butadiene skeleton. Ab initio calculations at the CIS/6-31G* level of theory suggest that the experimental large differences in the absorption maximum in the UV-vis spectra between the bisilole and the bicyclopentadiene derivatives are ascribed also to the low-lying LUMO level of the bisilole compared with the bicyclopentadiene. It is further demonstrated that the σ*–π* conjugation is enhanced by the molecular distortions, twisting and folding, of the bisilole skeleton present in the X-ray structure, resulting in the lowering of the LUMO level. The calculated data are supported by the redox potentials of some representative compounds, as determined by cyclic voltammetry measurements. The σ*–π* conjugation and the low-lying LUMO would thus be the origin of the unusual optical properties of bisilole derivatives.
Preparation of a DNA Complex with Lipoglutamide Having Tetraethylene Glycol Tails, and Its Application to DNA Delivery into Tumor Cells
Authors: Sato Toshinori , Akino Hiroyuki , Okahata Yoshio
Published: June 2006

We newly prepared a polyion complex of DNA with lipoglutamide, N,N′-bis(18-hydroxy-7,10,13,16-tetraoxaoctadecyl)-L-glutamide hydrochloride (abbreviated to 2EO4C6N+). Formation and characterization of the DNA/2EO4C6N+ complex were investigated by elemental analysis, melting temperature, and light-scattering measurements. Compaction of DNA by binding with the cationic 2EO4C6N+ was seen by multi-angle light scattering. Aggregation of the DNA/2EO4C6N+ complex was significantly depressed compared with the DNA complex without tetraethylene glycol. The DNA/2EO4C6N+ complex had low cytotoxicity and efficient internalization into tumor cells compared with native DNA.
Reactions of Benzyne with 1,3-Benzodithiole-2-thione and Related Compounds: Formation of Novel Tetracyclic Sulfonium Salts and Their Reactions Leading to Dibenzo-1,3,6,-trithiocin Derivatives
Authors: Nakayama Juzo , Kimata Atsuko , Taniguchi Hideki , Takahashi Fumihiko
Published: June 2006

A sulfur ylide intermediate, produced by a 1,3-dipolar cycloaddition of 1,3-benzodithiole-2-thione (5) with benzyne, was successfully trapped by hydrogen chloride to give a novel tetracyclic sulfonium salt, 9aH-9,10-dithia-4b-thioniaindeno[1,2-a]indene chloride (7), in good yield when benzyne was generated by the thermolysis of 2-carboxybenzenediazonium chloride (4). The reaction of ethylene trithiocarbonate with excess 4 provided a convenient one-pot synthesis of 7 in large quantities. The reduction of 7 with NaBH4 gave a novel ring compound, dibenzo[d,g][1,3,6]trithiocin (15), in 95% yield, while alkaline hydrolysis produced the 12-oxide derivative of 15. The treatment of 7 with t-BuOK gave 6,6′-bi(dibenzo[d,g][1,3,6]trithiocinylidene) in 84% yield. Also described are the reactions of benzyne with related compounds of 5.
Comparative Study of the Mutual Separation Characteristics and Mechanism for Neighboring Rare-Earth Elements from Binary Chloride Mixtures and Oxide Mixtures via Vapor Complexes
Authors: Wang Zhi-Chang , Yu Jin , Yu Yong-Li
Published: June 2006

A comparative study of the mutual separation characteristics and mechanism was made for neighboring rare-earth elements La, Ce, Pr, and Nd from their binary chloride mixtures and oxide mixtures using a chemical vapor-transport reaction under a suitable temperature and pressure gradient. The separation factors, expressed as the atomic ratios for the resulting chlorides, were observed within 6 h up to 21.4 for La : Ce, ≥100 for Pr : Ce, and 1.84 for Pr : Nd from the oxide mixtures; however, they were only 12.3 for La : Ce, 5.79 for Pr : Ce, and 1.32 for Pr : Nd from the chloride mixtures under identical reaction conditions, using AlCl3 as the sole complex former. It was also observed for the mutual separation from the oxide mixtures that the separation factors increased when KCl was added as another complex former, but decreased several times when either without chlorine in the carried gas, or without active carbon in the raw material, or under a poor vapor-transport condition. These results provide evidence that this reaction for the oxide mixtures would mainly be the combination of a carbothermic reduction-chlorination of the oxides, complexation of the chlorides, and transportation of the vapor complexes.
Preparation of Metallic Palladium Catalysts with Thermally Stable Surface Areas and Activities
Authors: Yada Satoru , Sasaki Tomoaki , Hiyamizu Makoto , Takagi Yuzuru
Published: June 2006

Pd metal catalysts were prepared by the reaction of palladium(II) chloride with sodium aluminate at pH 6—10. The Pd catalysts prepared at pH 10 contained only small amounts of Al (0.14 wt%), were the most thermally stable, and kept large specific surface areas and high catalytic activities in the hydrogenation of nitrobenzene even after hydrogen treatment at high temperatures up to 380 °C.
Novel Syntheses of Poly(o-aminobenzoic acid) and Copolymers of o-Aminobenzoic Acid and Aniline as Potential Candidates for Precursor of Polyaniline
Authors: Yan Hu , Wang Hung-Jen , Adisasmito Sanggono , Toshima Naoki
Published: June 2006

Poly(o-aminobenzoic acid) and copolymers of o-aminobenzoic acid and aniline were synthesized as excellent candidates for the precursor of polyaniline. The reaction conditions were optimized with emphasis on the isolated yield. The polymers were characterized by a number of techniques including infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, thermal analyses, and scanning electron microscopy. The yield of poly(o-aminobenzoic acid) was remarkably improved by addition of sodium hydroxide (an equivalent mole amount to the monomer) into the reaction system. Spectroscopic results indicate that the polymer has principally an Emeraldine structure. The copolymers were also obtained at high yield by addition of sodium hydroxide (an equivalent mole amount to o-aminobenzoic acid). The polymerization mechanism was briefly discussed on the basis of the pH effect upon the yield and easy elimination of the carboxyl group via a ring structure. The copolymer as well as poly(o-aminobenzoic acid) were found to be the precursors to produce polyaniline with elimination of carbon dioxide by heat treatment.
Chalcogenide Cluster Complexes of Chromium, Molybdenum, Tungsten, and Rhenium
Authors: Saito Taro , Imoto Hideo
Published: June 2006

Trinuclear, tetranuclear, hexanuclear, and dodecanuclear chalcogenide cluster complexes of chromium, molybdenum, tungsten, and rhenium have been synthesized and their molecular and electronic structures have been characterized. The structure-cluster valence electron relationships are analyzed and a new isoelectronic analogy is proposed.
Solid State NMR of 11B and 13C in Boron Carbide, B12C3 and 11B Enriched B12C3
Authors: Harazono Toshie , Hiroyama Yukiyo , Watanabe Tokuko
Published: June 2006

11B- and 13C-solid state NMR of boron carbide with different isotope ratios, B4C(11B/10B = 80.42/19.58; natural abundance isotope) and 11B4C(11B/10B = 99.5/0.5; 11B enriched sample), has been investigated. The linewidth of the icosahedral B (6h1and 6h2) in 11B-static NMR signal in 11B4C was greater in 11B4C than in B4C, which indicates that the B–B dipole–dipole interaction is the main mechanism for the broadening of the 11B-static NMR signal. The quadrupole coupling constant calculated from the signal position of (±1/2 ↔ ±3/2) transition was about 0.1 MHz. 11B-MAS spectra revealed the presence of at least two additional B sites (37 ppm and near −60 ppm) besides the icosahedral B sites (−6 ppm).
Quantum Mechanical Theory of Electron Transfer Reactions at Metal Electrodes
Authors: Sakata Tadayoshi
Published: June 2006

The quantum theory of electron transfer reactions at metal electrodes was studied. The obtained potential dependence of the electron transfer rate in the weak coupling case resembles the Butler–Volmer equation of classical electrochemistry. The volcano-shaped dependence of the hydrogen exchange current on the adsorption energy of hydrogen on various metals was explained microscopically, based on this theory. The mechanism of hydrogen evolution was also explained microscopically based on this theory. The exchange current density for hydrogen evolution at Pt electrode calculated quantitatively agreed well with the experimental value.
Unusual Spectral Shifts of Bis(4-aminophenyl)ether
Authors: Rajendiran Narayanasamy , Swaminathan Meenachisundram
Published: June 2006

Absorption and fluorescence spectra of Bis(4-aminophenyl)ether (DADPE) have been studied in different solvents and at various acid concentrations. The results are compared with the spectral data of 4-Aminodiphenyl ether (ADPE). The fluorescence spectra of DADPE are blue shifted relative to that of ADPE in polar and hydrogen-bonding solvents. A small, but unusual, red shift is observed in the fluorescence spectrum of the monocation relative to that of DADPE in water. These observations reveal that the effect of two amino groups in polar solvents is less than that of one amino group in the excited singlet state. The abnormally red-shifted fluorescence with a peak at around 422 nm at pH 3.5 is due to a dication-solvent exciplex. The formation of the dication-solvent exciplex leads to an excited state equilibria quite different from that in the ground state.
Charge-Transfer Complexation in an Aqueous Polyelectrolyte Solution. III. Complexation between Pyrenesulfonate or Anthracenesulfonate and Anthraquinonesulfonate Ions
Authors: Kawabata Yoshiya , Itaya Tomoyuki , Sasaki Yuki , Ochiai Hiroshi , Ueda Kazuyoshi , Imamura Akira
Published: June 2006

Charge-transfer (CT) complexations between 1-pyrenesulfonate ion (PyS−; donor) and 9,10-anthraquinone-2-sulfonate ion (2-AQS−; acceptor), and between anthracene-2-sulfonate ion (ACS−; donor) and 2-AQS− ion around the cationic polymers were studied by means of absorption and fluorescence spectroscopies as well as molecular-orbital calculations. The cationic polymers used in this study were poly(allylammonium) (PAAH+) and poly(1,1-dimethyl-3,5-dimethylenepiperidinium) (PDDP+). When solutions included only donor and acceptor molecules at low concentration, such as solutions of PyS− (1 × 10−4 M)/2-AQS− (1 × 10−4 M) and ACS− (1 × 10−4 M)/2-AQS− (1 × 10−4 M), they did not show any CT complex formation. However, the addition of polymers to these solutions exhibited charge-transfer absorption bands (CT band). A continuous variation method for CT bands of Na+PyS−/Na+2-AQS− in both PAAH+Cl− and PDDP+Cl− systems showed that a 1 : 1 type (PyS− : 2-AQS−) complex preferentially formed in the vicinity of these polyions. On the other hand, in the Na+ACS−/Na+2-AQS− system, a 1 : 2-type (ACS− : 2-AQS−) complex preferentially formed around PAAH+ and a 1 : 1-type complex formed around PDDP+. By comparing these results with our previous study between 9,10-dimethoxyanthracene-2-sulfonate and 2-AQS− in aqueous solution with the same polymers, it has become clear that the stoichiometries of the CT complexes and the peak positions of the observed CT bands are dependent upon the varieties of donor molecules. Molecular-orbital calculations have shown that there is a linear relationship between the calculated energy levels of the highest occupied molecular orbital (HOMO) of the donor molecules and the energies of the observed CT bands; that is, the donor molecule with a higher HOMO energy has the lower energy of the CT band.
Electrochemical Behavior of the Naphtoquinone Anchored onto a Gold Electrode through the Self-Assembled Monolayers of Aminoalkanethiol
Authors: Mukae Fumihiko , Takemura Hiroyuki , Takehara Kô
Published: June 2006

2,3-Dichloro-1,4-naphtoquinone (NQ) was anchored to a gold electrode surface through the self-assembled monolayers of aminoalkanethiols (AAT, HS(CH2)nNH2: n = 2, 5, and 8). The effect of the alkyl chain length of the AAT monolayer, which also acts as the spacer between the NQ molecule and the gold electrode surface, on the redox behavior of the immobilized NQ has been studied by using a voltammetric technique. The surface coverage of the anchored NQ was estimated to be 3.8 × 10−10 mol cm−2 in the case that 2-aminoethanethiol (HS(CH2)2NH2) was used as the monolayer constituent. The electron-transfer rate constant, ket, associated with the redox process of anchored NQ decreased from 9.7 s−1 at n = 2 to 0.78 s−1 at n = 8, with increasing the chain length of the AAT monolayer, though the redox potential of NQ was scarcely affected by the chain length. The tunneling barrier coefficient, β, of the electron transfer was estimated to be 0.36 Å−1, from the observed linear relationship between the ket value and the monolayer chain length.
Kinetics of Complexation between β-Cyclodextrin and 1-Propanol in Aqueous Solution by Ultrasonic Relaxation Method
Authors: Nishikawa Sadakatsu , Yamaguchi Sachiko
Published: June 2006

Ultrasonic absorption coefficients in aqueous solutions containing β-cyclodextrin and alcohols (ethanol and 1-propanol) have been measured in the frequency range from 3 to 220 MHz at 25 °C. Although a single relaxational absorption has been observed in solution with β-cyclodextrin and 1-propanol, it has not been found when the alcohol is ethanol. From the concentration dependence of the ultrasonic relaxation parameters, the cause of the relaxational absorption has been attributed to the perturbation of an equilibrium associated with the 1 : 1 complex formation (complexation) between β-cyclodextrin and 1-propanol. The rate and equilibrium constants as well as the standard volume change were determined for the complexation reaction of β-cyclodextrin and 1-propanol. The equilibrium constant determined in this study was found to be very consistent with the reported value for β-cyclodextrin and 1-propanol. The kinetic process for complexation between β-cyclodextrin and popular alcohols is discussed in relation to the sizes of the guest molecules.
Excimer Formation in Inclusion Complexes of β-Cyclodextrin with 1-Alkylnaphthalenes in Aqueous Solutions
Authors: Hamai Sanyo , Hatamiya Akira
Published: June 2006

In aqueous solutions, β-cyclodextrin (β-CD) has been found to form inclusion complexes with 1-methylnaphthalene, 1-ethylnaphthalene, 1-(chloromethyl)naphthalene, and 2-ethylnaphthalene. Addition of β-CD to aqueous solutions of 1-methylnaphthalene and 2-ethylnaphthalene has resulted in the observation of the excimer fluorescence of each compound. From simulations of the observed excimer fluorescence intensities of 1-methylnaphthalene and 2-ethylnaphthalene, the excimer fluorescence is concluded to be due to a 2 : 2 β-CD–alkylnaphthalene inclusion complex. In the cases of 1-ethylnaphthalene and 1-(chloromethyl)naphthalene, the excimer formation within the β-CD cavities seems to be prohibited due to the steric hindrance caused by a substituent, although the 2 : 2 β-CD–alkylnaphthalene inclusion complex is likely to be formed. Equilibrium constants for the formation of these 1 : 1 and 2 : 2 inclusion complexes have been evaluated from the monomer and excimer fluorescence intensity changes with β-CD concentration.
Internal Reference Compounds Available for the Determination of Binding Constants for Cyclodextrin Complexes by 1H NMR Spectrometry
Authors: Matsui Yoshihisa , Tokunaga Shuichi
Published: June 2006

The 1H NMR chemical shifts (δ’s) of the tetramethylammonium ion (TMA), methanol, and HDO, measured by using sodium 2,2-dimethyl-2-silapentane-5-sulfonate as an external reference, showed upfield shift with increasing concentration (c) of carbohydrates such as cyclodextrins (CD’s) and methyl glucopyranoside. The plots of δ vs. c gave straight lines with slopes proportional to the number of glucopyranoside residues involved in the carbohydrates, indicating that the upfield shifts are not due to inclusion phenomena but to a change in water structure with the formation of hydrogen bonds between carbohydrates and D2O. When an internal reference, TMA, was used instead, the 1H NMR signals of such organic molecules as acetonitrile, ethanol, 1-propanol, and 1-butanol showed uniform downfield shifts upon adding α-CD. The curve-fitting analysis of the plots of δ vs. c gave binding constants in agreement with those determined by other methods. It is concluded that the internal reference method is more reliable than the external one.
X-Ray Structures and Spectroscopic Studies of Diaqua- and Dichlorocopper(II) Complexes of 15-Crown-5 and 4′-Substituted Benzo-15-Crown-5 with a 3dz2 Ground-State Doublet
Authors: Li Yong
Published: June 2006

Crystallographic and spectroscopic investigations were carried out for Cu(II) complexes of 15-crown-5 (15C5) and 4′-substituted benzo-15-crown-5 (B15C5) derivatives. X-Ray diffraction measurements were performed for two single crystals of [Cu(15C5)(H2O)2](ClO4)2 and [Cu(B15C5)(H2O)2](ClO4)2, obtained from 60% HClO4 solutions. The results of the X-ray analysis demonstrated that these complexes take a seven-coordinate pentagonal bipyramidal geometry, in which the copper ion is located in the center of the crown ether cavity with two water molecules at the axial positions. The ESR spectra observed for these complexes in 60% HClO4 exhibited the characteristic g-anisotropy (gz < gx, gy), leading to an electronic configuration of a 3dz2 ground-state doublet. ESR and electronic absorption measurements were made for Cu(II) complexes of 4′-substituted B15C5 in systems of BF3–ether–water and of dry CHCl3 in which complexes having two chloride ions at the axial positions were produced. Although these systems showed the same remarkable substituent effects, clear differences were detected between them, attributable to the different axial ligands. The results of an extended Hückel MO calculation performed for the models of these complexes provide qualitative explanations for the experimental results.
Preparation and Characterization of Nickel(II), Palladium(II), and Platinum(II) Complexes Containing (2-Aminoethyl)dimethylphosphine or the Related Didentate Phosphine Ligands
Authors: Suzuki Takayoshi , Morikawa Akira , Kashiwabara Kazuo
Published: June 2006

Here are described several new nickel(II), palladium(II), and platinum(II) complexes of bis(chelate)-type with didentate phosphine ligands having an amino or thioether donor group: Me2PCH2CH2NH2 (edmp), Ph2PCH2CH2NH2 (edpp), Me2PCH2CH2NMe2 (dmedmp), or Me2PCH2CH2SMe (mtdmp). Bis(tetrafluoroborate) salts of [M(P–N or S)2]2+ (M = Ni, Pd, and Pt; (P–N or S) = the ligands above) have been prepared and the geometrical structures determined by NMR spectroscopy. All the palladium(II) complexes prepared in this study are cis-isomers, in contrast to the analogous Me2PCH2CH2S− (dmsp) complex (trans-[Pd(dmsp)2]), which indicates that the anionic phosphine-thiolate ligand prefers the trans geometry more than the neutral phosphine-amine or -thioether ligand does. The dichloride salts of the bis(edmp) complexes, cis-[M(edmp)2]Cl2 (M = Ni (4a), Pd(5a), and Pt(6a)), and those of the bis(edpp) complexes have been obtained as crystals, while the corresponding salts of dmedmp, mtdmp, and 8-(dimethylphosphino)quinoline complexes can not be isolated due to their oily properties. Further, addition of LiBF4 to a methanolic solution of 4a, 5a, or 6a gives exclusively a precipitate of the chloride tetrafluoroborate salt, cis-[M(edmp)2]Cl(BF4) (M = Ni (4c), Pd(5c), or Pt(6c)). The crystal structures of 4a, 5c, and 6a determined by X-ray analyses indicate a weak (not strong enough to form a five-coordinated complex) interaction between cis-[M(edmp)2]2+ and Cl− anion. The average M–N bond lengths in 4a, 5c, and 6a are considerably longer than those in the corresponding 1,2-ethanediamine complexes, owing to the strong trans influence of the –PMe2 group in edmp. The order of strength of the trans influence among NiII, PdII, and PtII triad metal series is non-periodical: NiII < PtII < PdII. This order is similar to the order among CoIII, RhIII, and IrIII triad metal series found in our previous study on fac-[M′(edmp)3]3+ (M′ = CoIII, RhIII, and IrIII) complexes.
Stereochemistry and Electrochemistry of Cobalt(II) and Cobalt(III) Complexes Containing Optically Active Tetradentate Schiff Base Ligands
Authors: Hirotsu Masakazu , Kojima Masaaki , Nakajima Kiyohiko , Kashino Setsuo , Yoshikawa Yuzo
Published: June 2006

Cobalt(II) complexes containing tetradentate Schiff base ligands with phenyl substituents, [Co(Schiff base)], have been prepared and the electrochemical properties are reported. The crystal structure of [Co{7-Phsal-(rac)-stien}], where the Schiff base ligand was derived from 2-hydroxybenzophenone and (rac)-1,2-diphenylethylenediamine, has been determined by X-ray structure analysis. Crystal data: monoclinic, P21/n, a = 13.956(2), b = 14.703(2), c = 17.808(3) Å, β = 112.21(1)°, V = 3383.0(9) Å3, Z = 4, and R = 0.052 and Rw = 0.039 for 3976 unique reflections with I > 3σ(I). The two phenyl groups in the N–N chelate moiety are in the axial positions and block the apical sites. In this complex, the redox potential of the Co(III)/Co(II) couple is 0.20 V vs. Ag/Ag+ in acetonitrile and becomes more positive by ca. 300 mV than that for [Co(salen)]. This large positive shift is attributed to the steric effect of the two axially disposed phenyl groups. The redox potentials of the analogous cobalt(II) Schiff base complexes, where (meso)-1,2-diphenylethylenediamine and (R)-1-phenylethylenediamine were used as a diamine, are also explained in terms of the steric effect of the phenyl substituents. The corresponding cobalt(III) Schiff base complexes with two additional axial ligands, [Co(Schiff base)(L)2]ClO4 (L = imidazole (im), 1-methylimidazole (Meim)), have been prepared. The steric interaction between the phenyl groups on the N–N chelate moiety and the axial ligands is discussed based on the X-ray structure, the circular dichroism (CD) spectra, and the 1H NMR spectra. The crystal structure determination of [Co{sal-(meso)-stien}(Meim)2]ClO4 has been performed. Crystal data: monoclinic, P21/c, a = 10.789(2), b = 20.512(3), c = 15.330(2) Å, β = 99.88(1)°, V = 3342.3(8) Å3, Z = 4, and R = 0.051 and Rw = 0.049 for 3414 unique reflections with I > 3σ(I). In order to study the steric effect of the phenyl substituents, the [Co(Schiff base)(L)2]ClO4 complexes have been prepared using (R)-1,2-propanediamine as a diamine. The different behavior shows that the interaction between the phenyl groups is sensitive to the orientation.
Structure and Some Properties of (Alkoxo)(subphthalocyaninato)boron(III)
Authors: Kasuga Kuninobu , Idehara Tsutomu , Handa Makoto , Ueda Yoichi , Fujiwara Takaji , Isa Kimio
Published: June 2006

A few (alkoxo)(subphthalocyaninato)boron(III) complexes, [BX(subpc)] (X = OMe, OEt, OBut, and OPh), were prepared and characterized. The molecular structure of [B(OEt)(subpc)] was determined by an X-ray structure analysis; the boron atom is situated 0.642 Å upward from the triangle plane of three isoindoline nitrogen atoms. The geometry of the boron atom is distorted tetrahedral, and the complex shows a wine-glass shape. The mass spectra showed that a part of the hydrogen atoms of the subphthalocyanine ring are displaced by the halogen atoms of boron trihalide or solvents. The complexes showed strong absorption bands at around 560 (Q band) and 300 nm (B band) in chloroform, respectively. The complexes decomposed in solution under irradiation with visible light. The first oxidative or reductive half-wave potential of [B(OEt)(subpc)] was observed at 1.06 V (vs. SCE) or −1.11 V, respectively.
Specific Salt Effect on the Solubility of fac-Tris(α-amino acidato)cobalt(III)
Authors: Yoshimura Yasuki
Published: June 2006

The salt effect on fac-tris(aniono)cobalt(III) of α-amino acids (fac-[Co(amino acidato)3]), such as d-proline and glycine, was examined by determining its solubility in various aqueous salt solutions. For a comparison, the solubilities of tris(2,4-pentanedionato)cobalt(III) ([Co(acac)3]) and l-phenylalanine (l-phalaH) were also determined. The enthalpy (ΔHs) and entropy of dissolution (ΔSs) were estimated from the temperature dependence of the solubility. While NaCl and Na2SO4 cause a decrease in the solubilities (salting-out effect) of [Co(acac)3] and l-phalaH, these salts result in an increase in the solubility (salting-in effect) of fac-[Co(amino acidato)3]. The salting-out of [Co(acac)3] is caused by an increase in ΔHs, while the salting-out of l-phalaH results from a decrease in TΔSs. On the other hand, the salting-in of fac-[Co(amino acidato)3] is caused by a decrease in ΔHs. These results suggest that the origin of the salt effect on fac-[Co(amino acidato)3] and l-phalaH differs from that of the salt effect on [Co(acac)3].
Ion Pair Charge-Transfer Complexes of Dithiolatocobaltates with Cationic Copper or Nickel Macrocycles: Crystal Structure and Magnetic Properties
Authors: Schmauch Georg , Chihara Teiji , Wakatsuki Yasuo , Hagiwara Masayuki , Kisch Horst
Published: June 2006

The complexes {[M(tim)]2+[Co(mnt)2]2−}, (M = Ni (NiCo), Cu (CuCo), tim = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene, mnt2− = cis-1,2-dicyano-1,2-ethylenedithiolato) have been isolated. NiCo and CuCo have isomorphous crystal structures (P1-), the basic feature of which is the presence of mixed donor–acceptor chains induced by short intrachain distances of 3.15 and 3.03 Å, respectively. For both NiCo and CuCo, an ion pair charge-transfer band is observed at 707 and 843 nm; application of the Hush model affords reorganization energies for electron transfer from the dianion to the dication of 89 and 104 kJ mol−1, respectively. The magnetic properties of the powder samples have been studied in the temperature range of 2 K to 300 K. In NiCo the diamagnetic [Ni(tim)]2+ acceptor induces antiferromagnetic coupling of the spin a half system [Co(mnt)2]2− along the a-axis over a distance of 6.3 Å. From the exchange coupling constant of J = −37 cm−1 a Weiss temperature of 26 K is calculated. Contrary to that, the magnetic orbitals of [Cu(tim)]2+ and [Co(mnt)2]2− remain uncoupled in CuCo.
Synthesis of a Bis(boronate) Compound Having s-Indacene Framework and Its Property as a Host Molecule for Dimethylaminopyridine
Authors: Sakurai Hidehiro , Iwasawa Nobuharu , Narasaka Koichi
Published: June 2006

A bis(boronate) compound (1) in which boronate components are situated on the same side of the planar s-indacene framework is synthesized from 1,5-dihydro-1,1,5,5-tetramethyl-s-indacene by OsO4-catalyzed dihydroxylation in the presence of dihydroxyphenylborane. The property of 1 as a host molecule has been examined with various compounds. The host 1 forms a 1 : 1 complex with 4-dimethylaminopyridine (DMAP) when an equimolar amount of DMAP is added; more concave-type complexes (2) are formed than convex-type complexes (3). When excess amounts of DMAP are present, a 1 : DMAP = 1 : 2 complex (4) can be isolated as a single crystal. This complex can be characterized by NMR measurements and X-ray analyses. These analyses indicate that the concave-type complex 2 does not have a bidentate coordination between the two boron–nitrogen atoms as proposed previously, but has a monodentate coordination form.
Synthesis of Chiral Crown Ethers Having Bromoarylene Moieties on Their Rim. Anomalous Behavior of Racemic Substrates in Cyclization to Crown Ethers
Authors: Kiyooka Syun-ichi , Tada Mitsuhiro , Kan Sachie , Fujio Mizue
Published: June 2006

Bis(binaphtho)-22-crown-5 and bis(binaphtho)-22-crown-4, having bromoarylene moities on their rim, were prepared from (R)- and (S)-2,2′-dihydroxy-1,1′-binaphthyl. An acyclic diol, bridged by two (R)-binaphthyl moieties, underwent cyclization reaction with diethylene glycol ditosylate to afford the corresponding (R,R)-bis(binaphtho)-22-crown-5 in a good yield (69%). A one-pot cyclization reaction of (R)-2,2′-dihydroxy-1,1′-binaphthyl with 2,6-bis(bromomethyl)bromobenzene resulted in a good yield (45%) of (R,R)-bis(binaphtho)-22-crown-4, having two symmetrical bromoarylene units. In contrast to the cases started with (R)- and (S)-2,2′ -dihydroxy-1,1′-binaphthyl, the racemate in cyclization reactions did not give the corresponding crown products in the expected proportion.
Self-Sensitized Photolysis of N-(1-Naphthoyl)-N-phenyl-O-(benzoyl-substituted benzoyl)hydroxylamines
Authors: Nagakubo Hiroshi , Kubota Gou , Kubo Kanji , Kaneko Tsuyoshi , Sakurai Tadamitsu , Inoue Hiroyasu
Published: June 2006

The mechanism of intramolecular triplet–triplet (T–T) energy transfer and subsequent reaction in N,O-diacylhydroxylamines was investigated using the model compounds N-(1-naphthoyl)-N-phenyl-O-(benzoyl-substituted benzoyl)hydroxylamines (NPB) with self-sensitization abilities. An examination of the UV absorption and phosphorescence behavior as well as of energy-minimized conformations of these relatively flexible model compounds established that T–T energy transfer from the benzophenone chromophore to the naphthoyl chromophore occurs in a nearly unit efficiency exhibiting only phosphorescence derived from the latter chromophore in both methanol–ethanol (1 : 1 v/v) and 2-chlorobutane at 77 K and is more likely to proceed by a “through-space” mechanism than by a “through-bond” mechanism. The self-sensitized photolysis of NPB with 366 nm light in methanol at room temperature was found to give the fragmentation products, N-phenyl-1-naphthalenecarboxamide (PNA), benzophenone (BP), and benzoyl-substituted benzoic acids (BBA), whereas no BBA was detected in the photolysis in 1,2-dichloroethane and acetonitrile. The finding that the reaction of NPB is efficiently quenched by trans-stilbene according to the Stern–Volmer equation in both methanol and 1,2-dichloroethane indicates that all the products come from the first excited triplet state of the naphthoyl chromophore. On the other hand, the enhanced hydrogen bonding ability of the medium resulted in an increase in the quantum yield for the formation of BBA (ΦBBA) accompanied by a decrease in ΦBA holding the magnitude of ΦBBA + ΦBA nearly constant. But neither ΦPNA nor the quantum yield for the disappearance of NPB was subject to such a hydrogen-bonding effect. This intriguing result was explained in terms of a mechanism in which the N–O bond cleavage in triplet NPB gives a vibrationally excited triplet radical pair whose relaxation is very slow compared to decarboxylation of the caged benzoyl-substituted benzoyloxyl radical in 1,2-dichloroethane. Solvation of this vibrationally hot radical pair through hydrogen bonding substantially promotes its relaxation eventually affording BBA.
Molecular Design of Boronic Acid-Based Dye Receptors for Nucleosides
Authors: Takeuchi Masayuki , Taguchi Masahiro , Shinmori Hideyuki , Shinkai Seiji
Published: June 2006

Chromophric receptors for nucleosides were designed utilizing the boronic acid–diol interaction which effectively operates in aqueous solution. Receptors consist of a boronic acid moiety and a dimethylaminophenylazo moiety. The boronic acid moiety forms a covalently-bonded ester linkage with the 2,3-diol group in nucleosides in a reversible manner and the anionic charge generated on the boron atom is stabilized intramolecularly by the pyridinium cation. The azo moiety can overlap with the heteroaromatic ring moiety in nucleosides to stabilize the complex. The complexation constants could be conveniently determined by the absorption spectral change. Comparison of the complexation constants with those of 2-deoxyadenosine without 2-OH and 1,4-anhydroerythritol without the heteroaromatic ring established that the complex formation is primarily due to the boronic acid–diol (2,3-diol) interaction and secondarily facilitated by the hydrophobic and/or π–π stacking interactions.
Asymmetric Synthesis of SM-9164, a Biologically Active Enantiomer of Antifungal Agent SM-8668
Authors: Miyauchi Hiroshi , Nakamura Toshio , Ohashi Naohito
Published: June 2006

SM-9164, a biologically active enantiomer of antifungal agent SM-8668, was prepared by asymmetric synthesis in 10 steps in 13% overall yield from commercially available 2-chloro-1-(2,4-difluorophenyl)ethanone. The crucial steps were Katsuki-Sharpless asymmetric epoxidation of the (E)-allylic alcohol and epimerization of the erythro-sulfone to the desired threo-isomer under basic conditions.
Ring-Opening Reactions of Cyclic Sufinate Esters with a Phenolic Leaving Group
Authors: Okuyama Tadashi , Takano Hideki , Senda Koji
Published: June 2006

The reactions of dibenzo[1,2]oxathiin 6-oxide (1a) and 3,4-dihydro-1,2-benzoxathiin 2-oxide (1b) with a phenolic leaving group were examined in acid and buffer solutions. The substrate 1b undergoes a ring opening in acid and at a higher pH, while 1a is stable in acid with a reverse ring closure predominating. The 18O-labeled 1a undergoes an isotope exchange in acid through a ring opening-closure. Although the ring opening of 1a and 1b is accelerated by buffer bases, owing to nucleophilic catalysis, a similar reaction of 3H-2,1-benzoxathiole 1-oxide with a benzylic alcohol leaving group is independent of the buffer concentration, or is decelerated by some amines. The results are accommodated by a mechanism involving a hypervalent addition intermediate with a varying rate-determining step.
An Efficient Synthesis of Unsymmetrical Dithioacetals from Sulfoxides and Thiols by the Magnesium Amide-Induced Pummerer-Type Reaction
Authors: Kobayashi Kazuhiro , Kawakita Masataka , Akamatsu Hideki , Morikawa Osamu , Konishi Hisatoshi
Published: June 2006

It has been found that the reactions of sulfoxides bearing hydrogen(s) at the α-position (R1SOCHR2R3: R1 = alkyl or Ph; R2 = H, alkyl, or Ph; R3 = H or Me) with thiols (R4SH: R4 = alkyl or aryl) in the presence of the (diisopropylamino)magnesium reagent, generated in situ from the reaction of ethylmagnesium bromide and diisopropylamine, in diethyl ether gave unsymmetrical dithioacetals (R1SCR2R3SR4) in isolated yields ranging from 44 to 91%.
Highly Stereocontrolled Access to 1,1,1-Trifluoro-2,3-epoxypropane via Lipase-Mediated Kinetic Resolution of 1,1,1-Trifluoro-3-(phenylthio)propan-2-ol and Its Application
Authors: Shimizu Makoto , Sugiyama Kouki , Fujisawa Tamotsu
Published: June 2006

1,1,1-Trifluoro-3-(phenylthio)propan-2-ol was prepared in high enantiomeric purity by lipase-mediated kinetic resolution of the corresponding esters. The resolved alcohol was successfully converted into 1,1,1-trifluoro-2,3-epoxypropane and/or used in the subsequent reactions as latent 1,1,1-trifluoro-2,3-epoxypropane via sulfonium salt formation.
Magnetic Field Effects on the Dopant-Exchange Process in Polypyrrole
Authors: Mogi Iwao
Published: June 2006

The electrochemical dopant-exchange (DE) process of p-toluenesulfonate-doped polypyrrole (PPy/TsO−) was studied in LiClO4 and LiBF4 aqueous solutions under high magnetic fields of up to 12 T. The application of magnetic fields to the redox process of the PPy/TsO− film or to the electropolymerization process shifts the undoping potential of the TsO− ion to a positive or negative side, respectively. As a result, the magnetic fields allow control of the plastic behavior in the DE process of the PPy/TsO− film. These results are discussed in connection with the effect of the diamagnetic orientation.