bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Photochemical Processes of Xanthene Dyes by Means of the Transient Absorption Spectra in the Visible/Near-IR Regions
Authors: Islam Shafiqul D-M , Yoshikawa Yuko , Fujitsuka Mamoru , Watanabe Akira , Ito Osamu
Published: June 2006

The rate constants for quenching of the triplet states of eosin and erythrosin (3D*) with various substrates have been evaluated using nanosecond laser flash photolysis while observing the transient absorption bands in the visible/near-IR regions. Intense transient absorption bands due to 3D* were observed at about 1040 nm. An energy-transfer reaction from 3D* to anthracene-9-carboxylic acid was confirmed by the appearance of the absorption band of the triplet state of the acid at 425 nm. The ion radicals of electron donors and electron acceptors were also observed with the decay of 3D*, indicating the occurrence of an electron-transfer reaction. High hydrogen-abstraction abilities of 3D* were also confirmed for substituted phenols and benzenethiols. The negative slopes of the Hammett plots indicate that the reaction center of 3D* has a highly electrophilic nature.
Fluorescence and Phosphorescence Properties of Naphthalene in Aqueous d-Glucose Solutions Containing 6-Deoxy-6-iodo-β-cyclodextrin at Room Temperature
Authors: Hamai Sanyo
Published: June 2006

In aqueous solutions, 6-deoxy-6-iodo-β-cyclodextrin (β-CDI) forms a 1 : 1 inclusion complex with naphthalene. The naphthalene fluorescence is quenched upon the formation of the inclusion complex with β-CDI. The room-temperature phosphorescence of naphthalene has been observed from aqueous naphthalene solutions containing both d-glucose and β-CDI. Although the room-temperature phosphorescence has also been observed from aqueous naphthalene solutions containing both d-glucose (5.0 g/5.0 mL) and β-cyclodextrin (1.0 × 10−2 mol dm−3), its intensity amounts to at most 9% of that containing d-glucose (5.0 g/5.0 mL) and β-CDI (1.0 × 10−3mol dm−3). In addition to the high viscosities of d-glucose solutions, the external heavy atom effects of β-CDI cause the appearance of the room-temperature phosphorescence. The room-temperature phosphorescence quantum yield of naphthalene in d-glucose (5.0 g/5.0 mL) solution containing β-CDI (1.0 × 10−3 mol dm−3) has been estimated to be 2.2 × 10−3, which is around 1.8% of the intrinsic phosphorescence quantum yield of naphthalene in ethanol at 77 K.
An Evaluation of the Overall Rotational Correlation Times of Tetraalkylammonium Ions in Solution. 13C NMR Relaxation Study
Authors: Masuda Yuichi , Tobita Junko , Muramoto Akiko
Published: June 2006

The 13C NMR spin-lattice and spin–spin relaxation times (T1 and T2), and the nuclear Overhauser effect (NOE) were measured for tetraalkylammonium ions (R4N+, R = C2H5 (Et), n-C3H7 (n-Pr), n-C4H9 (n-Bu), and n-C5H11 (n-Pen)) in the concentrated aqueous solutions of their bromides or chlorides. A minimum was observed in the temperature dependence of T1 for the α-carbon in each solution. The value was 1.2—1.4 times higher than that predicted assuming only the isotropic overall rotation of the R4N+ ion. This increase in the T1 minimum values was ascribed to the rotations around the N–α-C bonds with an restriction in the azimuthal angle for each bond. The ranges where the N–α-C bonds could rotate with the time scales much less than those for the overall rotations were determined by the values of the T1 minima for the corresponding R4N+ ions as ±20°, ±17°, ±20°, and ±20° centering the gauche conformations, respectively, for Et4N+, n-Pr4N+, n-Bu4N+, and n-Pen4N+. These values well reproduced the T2 and NOE values observed at various temperatures in the concentrated aqueous solutions of the R4N+ halides. By using the thus obtained ranges of the azimuthal angles, the overall rotational correlation times in the dilute aqueous solutions (0.01 mol kg−1) were also determined. The obtained rotational correlation times were compared with those calculated using the Stokes–Einstein–Debye equation and the effect of the hydrophobic hydration was discussed.
Crystal and Molecular Structures of RCH2CH2SCH3 (R = OCH3, SCH3)
Authors: Yokoyama Yoshihiro , Ohashi Yuji
Published: June 2006

The crystal structures of 1-methoxy-2-(methylthio)ethane (MMTE) and 1,2-bis(methylthio)ethane (BMTE), which are liquid materials at room temperature, have been analyzed by X-rays at 143 and 243 K, respectively. The crystal of MMTE belongs to the monoclinic system and the space group is P21/n. The cell dimensions are; a = 8.416(1), b = 7.817(2), c = 10.181(2) Å, β = 113.79(1)°, and V = 612.8(2) Å3. The MMTE molecule has a TTG conformer, which is different from the most stable one derived from the ab initio molecular orbital calculation on the MP2/6-31G* basis set. The crystal of BMTE belongs to the monoclinic system and the space group is P21/c. The cell dimensions are; a = 6.549(1), b = 5.835(1), c = 8.728(1) Å, β = 97.330(9)°, and V = 330.7(1) Å3. The BMTE molecule lies on an inversion center and has a GTG′ conformer, which is consistent with the most stable one derived from the ab initio calculation. The relative stability of these crystal structures and the possibility of crystal structures with the other conformers were examined by the molecular mechanics calculation. Trials to make a mixed crystal with MMTE and BMTE were in vain.
Effect of Guest Species on Inclusion Compound Formation of Deoxycholic Acid by Co-Grinding
Authors: Oguchi Toshio , Limmatvapirat Sontaya , Takahashi Chikako , Sungthongjeen Srisagul , Choi Woo Sik , Yonemochi Etsuo , Yamamoto Keiji
Published: June 2006

Deoxycholic acid (DCA) was ground with a guest compound by using a vibrational mill. Powder X-ray diffraction, differential scanning calorimetry, and fluorescence spectroscopic data indicated the formation of the inclusion complex in the ground mixture of DCA–phenanthrene and DCA–naphthalene systems. The DCA–naphthalene ground mixture was found to have higher crystallinity than the DCA–phenanthrene ground mixture, and this was assumed to relate to the difference in the crystallization temperature of the inclusion complex. When low-temperature grinding was performed for DCA and other aromatic hydrocarbons along with naphthalene and phenanthrene, all the ground mixtures were obtained in amorphous state. Crystallization of inclusion compounds from the amorphous ground mixtures was observed to occur at a higher temperature as the stoichiometric ratio (DCA/guest) of the compound increased. With regard to the formation of crystalline complex between DCA and a guest, such as naphthalene, by grinding at room temperature, a two-step mechanism was proposed: i.e., (i) amorphization of both DCA and guest crystals, and (ii) crystallization of the inclusion complex induced above a certain temperature.
Synthesis and Characterization of Hexadentate Cobalt(III) Complexes with New edta-Type Ligands Part 5. Structure and Absolute Configuration of the trans(O5)(−)546-Isomer of Lithium (Ethylenediamine-N,N,N′-triacetato-N′-3-propionato)cobaltate(III) Monohydrate, (−)546-trans(O5)-Li[Co(ed3ap)]·H2O. Strain Analysis of [Co(edta-Type)]− Chelates in Relation to Their Octahedral Distortion
Authors: Radanovic Dušan J , Miletic Vesna D , Ama Tomoharu , Kawaguchi Hiroshi
Published: June 2006

The preparation and resolution of the two hexadentate Co(III) complexes containing unsymmetrical edta-type ligands, [Co(ed3ap)]− (A) and [Co(u-eddadp)]− (B) (ed3ap = ethylenediamine-N,N,N′-triacetate-N′-3-propionate ion; u-eddadp = ethylenediamine-N-diacetate-N′-di-3-propionate ion) have been reexamined. The X-ray data are reported for the Λ-(−)546-trans(O)5-Li[Co(ed3ap)]·H2O for which the same (Λ) absolute configuration was predicted from the CD sign pattern of the lowest energy band. The complex crystallizes in the space group P21 (#4) of the monoclinic crystal system with a = 6.523(4), b = 15.025(7), c = 7.464(3) Å, β = 105.40(4)°, and Z = 2. The conformations of the chelate rings are found to be envelope for the glycinates and skew-boat (half-chair) for the β-alaninate ring. Structural parameters and strain analysis of [Co(edta-type)]− chelates are discussed in relation to the structure of the ligand and octahedral distortion of complexes. The CD and IR (carboxylate region) spectra of complexes A and B are also discussed.
Association Constants of Ferrocene with Cyclodextrins in Aqueous Medium Determined by Solubility Measurements of Ferrocene
Authors: Wu Ji-Shi , Toda Kei , Tanaka Akira , Sanemasa Isao
Published: June 2006

The association constants of ferrocene with cyclodextrins (CyD’s) in an aqueous medium at 25 °C have been determined by solubility measurements of ferrocene in both the absence and presence of CyD. The solubility of ferrocene in pure water was found to be (4.25 ± 0.02) × 10−5 mol dm−3 at 25.0 ± 0.1 °C. The β- and γ-CyD’s form only 1 : 1 complexes with ferrocene. The 1 : 1 association constants were determined to be (1.39 ± 0.21) × 102 (α), (1.65 ± 0.04) × 104 (β), and (9.04 ± 0.11) × 102 dm3 mol−1 (γ). The 2 : 1 (CyD : ferrocene) association constant was (2.36 ± 0.06) × 103 dm3 mol−1 (α). Ferrocene-included CyD precipitates were also prepared in water, and their stability upon drying in air was studied. The sublimation enthalpy of ferrocene in the temperature range of 290.65 to 298.15 K was estimated to be 74.2 ± 1.5 kJ mol−1.
Synthesis, Structure, and Thermolysis Mechanism of S-Alkoxythiazynes
Authors: Yoshimura Toshiaki , Ohkubo Masanori , Fujii Takayoshi , Kita Hiroshi , Wakai Youko , Ono Shin , Morita Hiroyuki , Shimasaki Choichiro , Horn Ernst
Published: June 2006

S-Alkoxy-S,S-diarylthiazynes were prepared by two methods: the alkaline hydrolysis of S,S-diaryl-N-halosulfilimines in aqueous alcohols and the reaction of S,S-diaryl-S-fluorothiazynes with sodium alkoxides. The structure of S,S-diphenyl-S-propoxythiazyne was determined by an X-ray crystallographic analysis, which showed a short SN bond length of 1.441(3) Å. The thermolysis of S-alkoxythiazynes gave elimination products, which were identified as the corresponding carbonyl compounds and N-unsubstituted S,S-diarylsulfilimines. Kinetic experiments for the thermolysis of the S-alkoxy-S,S-diarylthiazynes were carried out. The first-order kinetic behavior, a large kinetic isotope effect (kH/kD = 6.1) using S,S-diphenyl-S-[1,1-2H2]propoxythiazyne, a negative activation entropy (ΔS‡ = −30 J K−1mol−1), and a negative Hammett ρ-value (ρ = −0.35) on the phenyl group were obtained, suggesting that the reaction proceeds via a concerted five-membered cyclic transition state. A deviation from the ideal concerted transition state is discussed in comparison with that for sulfoxides.
Intramolecular Cyclization of 4-[3-(Trimethylsilyl)prop-1-en-1-yl]cyclohexanecarbaldehyde with Loss of Formyl Carbon
Authors: Kuroda Chiaki , Murase Atsushi , Suzuki Hideyuki , Endo Toru , Anzai Shuzo
Published: June 2006

Treatment of cis- and trans-4-[3-(trimethylsilyl)prop-1-en-1-yl]cyclohexanecarbaldehyde (2a and 2b) with tetrabutylammonium fluoride in dilute tetrahydrofuran afforded 7-vinylbicyclo[2.2.1]heptan-1-ol (3), the same product obtained from 4-[3-(trimethylsilyl)prop-1-en-1-yl]cyclohexanone (1). It was found that oxidative deformylation of 2a, b to 1 takes place under basic conditions before the cyclization to 3. It was also shown that cyclization of allylsilane with carbonyl does not proceed via an eclipsed conformation.
Photoamination of Alkenylnaphthalenes with Ammonia via Electron Transfer
Authors: Yasuda Masahide , Kojima Ryuji , Ohira Ryujiro , Shiragami Tsutomu , Shima Kensuke
Published: June 2006

The photoamination of 1-(2-methyl-1-propenyl)naphthalene (1a) with ammonia in the presence of p-dicyanobenzene (p-DCB) occurred selectively at the alkenyl group but not at the naphthyl group to give 1-(2-amino-2-methylpropyl)naphthalene (2a). Similarly, the photoamination of several kinds of alkenylnaphthalenes (1) proceeded selectively at the alkenyl group. The photoamination proceeded via the nucleophilic addition of ammonia to the cation radical of 1 generated by the photoinduced electron transfer to p-DCB to give the aminated radical after deprotonation. Distribution of the positive charge in 1+• and the stabilities of the aminated radicals were calculated by the PM3-UHF method. The stabilities of the aminated radicals agreed with the regioselectivity.
The Role of Arginine in Thrombin Receptor Tethered-Ligand Peptide in Intramolecular Receptor Binding and Self-Activation
Authors: Nose Takeru , Satoh Yusuke , Fujita Tsugumi , Ohno Motonori , Nakajima Masahide , Inoue Yoshihisa , Ogino Yoshio , Costa Tommaso , Shimohigashi Yasuyuki
Published: June 2006

Synthetic heptapeptide of the human thrombin receptor tethered-ligand peptide, H–Ser–Phe–Leu–Leu–Arg–Asn–Pro–NH2 (SFLLRNP), activates fully the thrombin receptor without thrombin. The functional role of Arg-5 was examined using a series of analogs having amino acid substitutions at position 5 in this assays was to assess the abilities to hydrolyze phosphoinositide in human neuroblastoma SH-EP cells and to aggregate the human platelet. The replacement of Arg-5 by Ala reduced the activity (9% activity of the parent peptide) in the PI-turnover assay, and abolished completely the platelet aggregation activity. SFLL/Lys/NP was also active, but moderately: 36% in PI-turnover and 12% in platelet aggregation. These results indicated that the electrostatic interaction of the Arg-guanidino group is important for a peptide to interact with the receptor. When citrulline or glutamine was placed at position 5 instead of arginine, the resulting SFLL/citrulline/NP and SFLL/Gln/NP were found to be potent in both assays. Since citrulline and glutamine possess a side chain which can serve as hydrogen donor and/or acceptor, the receptor activation of these peptides appears to be due to hydrogen bonding at this position. The molecular mechanisms to explain both electrostatic and hydrogen-bonding interactions were postulated based on the structural modeling of seven-transmembrane domain thrombin receptor.
Synthesis and Reduction of Octasilyl[4]radialene. Structure and Dynamic Study of [4]Radialene Dianion with Eight-Center Ten-Electron π-System
Authors: Matsuo Tsukasa , Sekiguchi Akira , Ichinohe Masaaki , Ebata Keisuke , Sakurai Hideki
Published: June 2006

The intramolecular reaction of 3,3,5,5,8,8,10,10,13,13,15,15,18,18,20,20-hexadecamethyl-3,5,8,10,13,15,18,20-octasilacycloicosa-1,6,11,16-tetrayne (1) with three molar amounts of [Mn(CO)3(Me-Cp)] in THF under photochemical and refluxing conditions produced octasilyl[4]radialene derivative (2). The reaction of 2 with alkali metals (Li, Na, and K) in THF gave dialkali metal salts of the corresponding dianion (4) with an eight-center ten-electron π-system. The molecular structure of dilithium salt of octasilyl[4]radialene dianion (4a) has been established by X-ray crystallography. The two lithium atoms are located above and below and are bonded to the atoms of the radialene framework to give a bis-CIP structure. The structural parameters of 4a are discussed in comparison to those of 2. The structure of 4a in solution has also been discussed on the basis of NMR spectroscopic data. The two Li+ ions of 4a are not fixed to the π-skeleton in toluene-d8, but are fluxional, giving a symmetric structure (bis-CIP) on the NMR time scale. In a solvating medium such as THF-d8, one of the Li+ ions dissociates to yield an ion pair (CIP and SSIP). Some evidence for the Li+ ion walk on the π-skeleton is demonstrated.
Coumarin and Thiocoumarin Dyes for Guest–Host Type Liquid Crystal Displays
Authors: Iwanaga Hiroki , Naito Katsuyuki , Sunohara Kazuyuki , Okajima Masaki
Published: June 2006

To realize bright and pure colors in Guest–Host type Liquid Crystal Displays (GH-LCDs), the solubilities and/or absorption coefficients of dichroic dyes which are dissolved in liquid crystals are the most important properties. We have found that a mixture of coumarin and anthraquinone dyes was very useful because it had a large absorption coefficient and little fluorescence. On the other hand, substitution of a sulfur atom for an oxygen atom of the coumarin dye contributes to increase its solubility to liquid crystals, particularly at low temperatures.
Effects of Pressure on the DNA Minor Groove Binding of Hoechst 33258
Authors: Tang Guo-Qing , Tanaka Naoki , Kunugi Shigeru
Published: June 2006

We investigated the pressure perturbations of DNA minor groove binding of the antibiotic drug Hoechst 33258 (2′-(4-hydroxyphenyl-5-(4-methyl-1-piperazinyl)-2,5′-bi-1H-benzimidazole trihydrochlolride) on fluorescent titrations and on restriction endonuclease protection assays. Significantly, pressure elevations were found to disturb the binding of Hoechst 33258 with poly(dA)·poly(dT) and poly[d(A–T)]·poly[d(A–T)] in opposite directions, which suggested different volume changes (sign and size) in their complexation reactions. The ability of Hoechst 33258 to provide the restriction endonuclease protection for plasmid DNA was notably enhanced by the application of pressure, implying that there is a large volume contraction following the EcoRI site-drug interaction. These data were explained by DNA hydration and its effects on the ligand complexation that is sequence dependent.
Estimation of the Surface-Diffusion Coefficient in Gas-Phase Adsorption Using Octadecylsilyl-Silica Gel
Authors: Miyabe Kanji , Takeuchi Shigeya , Tezuka Yoshisato
Published: June 2006

Surface-diffusion data in a gaseous adsorption system using an octadecylsilyl-silica gel as an adsorbent were analyzed according to a restricted Knudsen diffusion model. A linear correlation was confirmed between the ratio of the restriction energy for Knudsen diffusion to the isosteric heat of adsorption, Qst, and 1/(−Qst). It was proved that a linear correlation could be observed under the conditions that a linear free-energy relation and an enthalpy–entropy compensation in adsorption equilibrium were established. An estimation procedure of the surface-diffusion coefficient (Ds) was proposed based on the results. It was demonstrated that Ds of various adsorbates at given temperatures could be estimated with an error of less than about 50% from only one datum of the adsorption equilibrium constant measured at a different temperature. Similarly, Ds in gas-phase adsorption could be estimated from the evaporative energy of the adsorbates without experimental data.
Raman Spectral Studies of Aqueous Strontium Nitrate Solution Up to 450 °C and 40 MPa
Authors: Ikushima Yutaka , Hatakeda Kiyotaka , Saito Norio , Arai Masahiko
Published: June 2006

We have studied the structure of aqueous strontium nitrate solution (2.8 M) at temperatures up to 450 °C and pressures of 22.6, 30.0, and 40.0 MPa using Raman spectroscopy technique. The strontium ion forms two species; one is the bound species in contact more strongly with the NO3− like the monovalent cation, and the other is the free species separated from the NO3−. The relative ratio of the bound species to the free ones remains unaltered with an increase in temperature up to 375 °C; above this temperature, however, the ratio significantly increases. The half-width at half peak height (hwhh) for the bound species is larger than that for the free species; it increases at 375 °C or above, suggesting that the bound species relaxes faster than does the free species. The relaxation for the bound species becomes significantly faster at the critical temperature. The number of water molecules of hydration around Sr2+, nH2O, is estimated by the comparison of Raman intensity and previous XAFS data. As the temperature increases, the nH2O gradually decreases. The value shows a remarkable decrease above 370 °C, indicating the displacement of water molecules from the solvation shell around Sr2+ and the concomitant entry of NO3− into the shell at higher temperatures.
The Structural Stability of Seven-Coordinate Divalent Cations in the First Transition Series Relevant to the Water-Exchange Reaction Mechanism
Authors: Tsutsui Yuko , Wasada Hiroaki , Funahashi Shigenobu
Published: June 2006

We studied the structural stability of heptahydrated divalent cations in the first transition series as model intermediary species in associative reaction pathways for the water exchange of hexahydrated cations by ab initio molecular-orbital methods. All of the structures of heptacoordination are pentagonal bipyramidal with a distorted equatorial plane. The structural stabilities are strongly dependent on their d-electron configurations. An associative mechanism is possible for the water-exchange reactions of hexahydrated divalent cations having less than seven d electrons, because the seven-coordinate species are located at the local minima or at the saddle points on the potential-energy surface. The occupation of the antibonding b orbital induces a transition density corresponding to an antisymmetric distortion through an interaction with a low-lying 4s orbital. The large bonding interaction makes the heptahydrated manganese(II) ion to become located at a local minimum. The occupancy of antibonding a orbitals determines the pattern of the antibonding interaction. Hexahydrated divalent cations with d3, d6, and d7 configurations (vanadium(II), iron(II), and cobalt(II)) prefer a cis attack, while chromium(II) with a d4 configuration prefers a trans attack during the operative associative process of the water-exchange reaction.
IR Sensing of the Electronic Structure in the Mixed-Valence States of Iron Carbonyl-Attached Biferrocene and Terferrocene
Authors: Hirao Takashi , Aramaki Kunitsugu , Nishihara Hiroshi
Published: June 2006

Ferrocene, 1,1,″-biferrocene and 1,1″ : 1′″,1″″-terferrocene derivatives involving a (cycopentadiene)Fe(CO)3 moiety were synthesized; the ν(CO) peak frequency shifts during their redox processes were monitored by the IRAS technique. All the complexes give two ν(CO) peaks, which shift to higher wavenumbers (12—18 cm−1) by the oxidation from the most reduced (all Fe’s are Fe(II)) to the most oxidized (all Fe’s are Fe(III)) forms. The biferrocene derivative in the monocationic form gives peaks at wavenumbers between those for neutral and dicationic forms, probably because the rate of electron-transfer affording two electronic isomers, Red–Ox–[FeCO] and Ox–Red–[FeCO], where Red, Ox, and [FeCO] refer to reduced and oxidized forms of a ferrocene unit, and a [(η4-cyclopentadiene)Fe(CO)3] moiety, respectively, is slower than or comparable to the time scale of IR (1011—1012 s−1). The terferrocene derivative shows ν(CO) frequency changes corresponding to the three-step 1e− oxidation processes. The shift is most significant in the second oxidation step, implying that the largest change in charge is that of the ferrocene unit nearest to Fe(CO)3. This is in principle consistent with the elucidation of the oxidation process via thermodynamically favorable electronic isomers based on the interaction energy between neighboring oxidized and reduced sites:

Red–Red–Red–[FeCO] → Red–Ox–Red–[FeCO] → Ox–Red–Ox–[FeCO] → Ox–Ox–Ox–[FeCO].
Bis[(methanol){N-salicylidene-N′-(2-phenylimidazol-4-ylmethylidene)-1,3-propanediaminato}nickel(II)] Bridged by Di-μ-phenoxo Moiety and the Deprotonated Imidazolate-Bridged Cyclic-Tetranuclear Complex
Authors: Mimura Masaaki , Matsuo Toshihiro , Matsumoto Naohide , Takamizawa Satoshi , Mori Wasuke , Re Nazzareno
Published: June 2006

Protonated and deprotonated forms of nickel(II) complex with N-salicylidene-N′-(2-phenylimidazol-4-ylmethylidene)-1,3-propanediamine, 1 and 1′, were synthesized and characterized. The X-ray crystal structures of 1·H2O and 1′ were determined: 1·H2O, P21/n (No. 14), a = 11.642(2), b = 12.908(3), c = 15.264(2) Å, β = 96.642(1)°; 1′, I41/a (No. 88), a = 22.651(3), c = 13.950(7) Å. The crystal of 1·H2O assumes a dinuclear structure bridged by the di-μ-phenoxo moiety in an out-of-plane fashion with Ni–Ni = 3.173(1) Å and Ni–O = 2.126(3) Å of the Ni2O2 core and two perchlorate ions as counter anions, in which the nickel(II) ion assumes an octahedral coordination geometry with N3O3 donor atoms consisting of four donor atoms of a quadridentate ligand, a bridging phenoxo-oxygen atom, and an oxygen atom of methanol. A ferromagnetic interaction with J = +7.1 cm−1 operates between the two high-spin nickel(II) ions. 1 undergoes a deprotonation of the imidazole proton under basic conditions to give the deprotonated complex 1′. The crystal of 1′ consists of an electrically-neutral imidazolate-bridged cyclic-tetranuclear molecule with Ni–Ni = 6.339(2) Å and Ni–N = 2.051(7) Å, in which the nickel(II) ion assumes a square-pyramidal geometry with N4O donor atoms consisting of the quadridentate ligand and an imidazolate nitrogen of the adjacent nickel(II) complex. An antiferromagnetic interaction with J = −6.3 cm−1 is observed between the adjacent nickel(II) ions through the imidazolate group. Since the corresponding deprotonated copper(II) complex with the same ligand assumed an imidazolate-bridged zigzag-chain structure, the result with the nickel(II) complex demonstrates a very marked influence of the metal ion on the formation of the assembly structure.
Electronic Effect of Substituents on Cyclopalladation of the Solvated Palladium(II) Complexes with N-Benzyl Triamine [Pd(Sol){(4-XC6H4CH2)NH(CH2)3NR(CH2)3NH2}]2+(Sol = Solvent; R = Ph, H, and Me; X = H, Et, Me, MeO, Cl, and NO2)
Authors: Yagyu Takeyoshi , Iwatsuki Satoshi , Aizawa Sen-ichi , Funahashi Shigenobu
Published: June 2006

The solvated palladium(II) complexes with the potentially cyclopalladating monobenzyl triamine ligand, [Pd(CH3CN)(BnPhdptn)](BF4)2 (1) (BnPhdptn = N-(3-aminopropyl)-N′-benzyl-N-phenyl-1,3-propanediamine), [Pd(CH3CN)(Bndptn)](BF4)2(2) (Bndptn = N-(3-aminopropyl)-N′-benzyl-1,3-propanediamine), [Pd(CH3CN)(4-XC6H4CH2dptn)](BF4)2 (4-XC6H4CH2dptn = N-(3-aminopropyl)-N′-(4-substituted benzyl)-1,3-propanediamine; X = Me (3), MeO (4), Cl (5), and NO2 (6)), and [Pd(CH3CN)(4-XC6H4CH2Medptn)](BF4)2 (4-XC6H4CH2Medptn = N-(3-aminopropyl)-N′-(4-substituted benzyl)-N-methyl-1,3-propanediamine; X = Et (8), Me (9), MeO (10), Cl (11), and NO2 (12)) have been synthesized. The kinetics for the cyclopalladation of 1—6, [Pd(CH3CN)(BnMedptn)](BF4)2 (7) (BnMedptn = N-(3-aminopropyl)-N′-benzyl-N-methyl-1,3-propanediamine), 8—12 in N,N-dimethylformamide (DMF), and 7, 9, 11, and 12 at 25 °C in dimethyl sulfoxide (DMSO) have been investigated. The Hammett ρvalues for the rate constants at 25 °C obtained by variation of the 4-substituent on the benzyl group were −0.73 for 2—6 and −0.87 for 7—12 in DMF, and −0.67 for 7, 9, 11, and 12 in DMSO using the substituent constants for the meta position, σm. The difference in the rate constants for 1, 2, and 7 at 25 °C in DMF and the negative ρ values confirmed that the present cyclopalladation proceeds by the electrophilic attack of the palladium(II) center on the ortho benzyl carbon. We have also discussed the electronic effects of the solvent and the N-substituent of the bound triamine on the ρ values to arrive at a conclusion for the reaction mechanism of [Pd(solvent)(N-benzyltriamine)]-type complexes.
N,N′-Dialkyldiamide-Type Phosphate Protecting Groups for Fmoc Synthesis of Phosphotyrosine-Containing Peptides: Optimization of the Alkyl Group
Authors: Ueki Masaaki , Goto Mitsutaka , Okumura Jin , Ishii Yusuke
Published: June 2006

Synthesis and evaluation of three Fmoc–phosphotyrosine derivatives with a phosphate group protected as N,N′-dialkyldiamide (alkyl = Prn, Pri, and Bui) were studied. All the derivatives were obtained as crystals, among which the Buiderivative (4c) was the best in ease of preparation and excellence in cleavage property. Solid phase synthesis of a methionine-containing peptide, H–Tyr(PO3H2)–Val–Pro–Met–Leu–OH, could be done without any problems.
Syntheses of Phospholipids Containing 2-Nitrobenzyl Ester Moieties at the Terminals of Alkyl Chains and Properties of Photodegradable Liposomes from the Lipids
Authors: Yamaguchi Kazuo , Tsuda Yoshihiro , Shimakage Taka-aki , Kusumi Akihiro
Published: June 2006

Phospholipid 1a bearing 2-nitrobenzyl ester moieties as a photocleavable group at the terminal of alkyl chains was synthesized from the corresponding terminal carboxy-bearing phospholipid 2 by the reaction with 2-nitrophenyl-substituted diazomethane. Phospholipid, 1b bearing α-methyl-2-nitrobenzyl group, 1c bearing 4,5-dimethoxy-2-nitrobenzyl group, and 1d bearing α-methyl-4,5-dimethoxy-2-nitrobenzyl group were similarly synthesized by the use of the respective diazo compounds. The order of photolysis rates of 2-nitrobenzyl ester linkage of phospholipids by ultrahigh-pressure mercury lamp is 1b ≥ 1d > 1a > 1c. Liposomes of 1a—1d containing calcein in the inner aqueous layer were prepared by vortexing, sonication, and gel-filtration. UV irradiation resulted in fast release of the entrapped fluorescence dye. The order of release rates : 1b ≥ 1d > 1c > 1a is consistent with that of photolysis rates except for 1c, which has poor retention of the dye.
Functionalization of Inclusion Cavities of Bile Acid Hosts. Channel-Type Inclusion Compounds of Cholamide
Authors: Sada Kazuki , Kondo Takashi , Ushioda Masahiko , Matsuura Yoshiaki , Nakano Kazunori , Miyata Mikiji , Miki Kunio
Published: June 2006

Clathrate formation and crystal structures of 3α, 7α, 12α-trihydroxy-5β-cholan-24-amide (cholamide) have been investigated. Cholamide forms inclusion compounds with various organic compounds having hydrogen-bond (H-bond) donors. X-Ray crystallographic studies showed that cholamide has bilayer structures with molecular channels. The crystal structures are quite similar to those of channel-type inclusion crystals of cholic acid. Steric dimensions of the host cavities are identical, but cholamide has an H-bond ‘hook’ on the wall of the channels, while cholic acid does not. This difference is correlated with not only the inclusion abilities but also the molecular structures. Two H-bond donors of the amide group yield a hydrophilic inclusion cavity that includes H-bond acceptors, and one H-bond donor of the carboxylic acid gives a lipophilic inclusion cavity that includes non-polar or less polar compounds.
A Facile Synthesis of Trifluoromethylamines by Oxidative Desulfurization–Fluorination of Dithiocarbamates
Authors: Kanie Kiyoshi , Mizuno Katsuya , Kuroboshi Manabu , Hiyama Tamejiro
Published: June 2006

Trifluoromethylamines are easily synthesized from dithiocarbamates by a reagent system consisting of tetrabutylammonium dihydrogentrifluoride and an N-halo imide under mild conditions. When this reaction was applied to dithiocarbamates ArN(R)CS2Me at higher temperatures, the trifluoromethylation was accompanied by halogen substitution at the p-position of the Ar group. The synthesis of trifluoromethyl-substituted adenosine is also described.
Characterization of Electron Deficient Oxide Ion of Heat Treated MgO for Activation of Methane
Authors: Karasuda Takashi , Aika Ken-ichi
Published: June 2006

Electron deficient oxide ions on the heat-treated MgO were characterized by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and other methods (electron spin resonance (ESR) and Fourier transform infrared spectroscopy (FT-IR)). The O1s XP spectrum of MgO evacuated at 873 K has a very small shoulder peak (533.8 eV) at the higher binding energy (BE) side of the O2− peak (at 531.5 eV). Upon the evacuation of 973 K, this shoulder peak increased remarkably, and at the same time H2 started to be evolved (TPD). Since H2 must be produced from a dissolved water in the bulk or surface OH without forming O2, the surface oxygen must have a charge lower than 2. Thus, the shoulder peak was assigned to O−. This state was not observable by ESR and not reactive to methane at room temperature (FT-IR), while O− produced on the UV-irradiated MgO was ESR-observable and reactive. However, the heat-treated surface O− must react with methane during the oxidative coupling of methane (OCM) reaction at 973 K. The two kinds of states for O− on MgO are discussed from the standpoint of the defect chemistry.
Novel Offset Printing without a Developing Process Utilizing the UV-Photodecomposition of Polysilane
Authors: Nagayama Norio , Tachibana Yasuhiro , Yokoyama Masaaki
Published: June 2006

Utilizing a surface modification of polysilane film due to photodecomposition by patterned UV-light irradiation, we have confirmed that polysilanes have a potential application as a material for novel offset printing, which will enable us to skip the alkaline development process required in current offset printing. This has been achieved by a wettability change of photodecomposable polysilane and a modified fountain solution. It has been found that the hydrophilicity in the UV-exposed area is sufficiently maintained by a treatment with tris(2-hydroxyethyl)methylammonium iodide added to the fountain water, which rejects an oil ink in the printing process.
Silicic Acid Polymerization Catalyzed by Amines and Polyamines
Authors: Mizutani Tadashi , Nagase Hisato , Fujiwara Naohiko , Ogoshi Hisanobu
Published: June 2006

Amines, particularly polyamines, catalyzed the polycondensation of silicic acid in water. The resultant gel contained these polyamines with a N/Si molar ratio of up to 0.5. IR and powder X-ray studies showed that silica gel and polyamines are hybridized at a molecular level through hydrogen bonding. The gel adsorbed anionic dyes from water, whereas normal silica gel adsorbs cationic dyes. Induced CD was observed for the indigo carmine adsorbed on silica gel–poly(l-lysine) hybrid, showing that the hybrid provides a chiral environment to the adsorbate.
Stereoselection without Steric Effect but Controlled by Electronic Effect: Important Contribution of Ground State
Authors: Ohno Atsuyoshi
Published: June 2006

Stereoselectivity controlled by an electronic effect but not by a steric effect is presented. A modern concept of stereochemistry is proposed where stereochemistry is controlled by acceleration of the reaction instead of deceleration, as has been proposed based on classical concept. The mechanism of (net) hydride transfer from a dihydronicotinamide adenine dinucleotide (NADH)/dihydronicotinamide adenine dinucleotide phosphate (NADPH) analogue to certain oxidizing agents is discussed in relation to this modern stereochemistry concept. The reaction involves a preassociation complex where the stereochemistry of the reaction is defined. Only a complex that has appropriate intermolecular arrangement can proceed to the transition state. The difference in free energy between the two stereoisomers of the preassociation complex contributes to almost all of the difference in the free energy of activation for the stereoisomers in the transition state, then to the ratio of stereoisomers in the product. Thus, the transition state does not participate in determining the stereochemistry of the reaction.

Similarities between the present and enzymatic reactions from the viewpoint of the reaction scheme are also suggested.
Maturity of Finite Groups. An Application to Combinatorial Enumeration of Isomers
Authors: Fujita Shinsaku
Published: June 2006

The maturity of a finite group G is defined by examining how a dominant class (Q-conjugacy class) corresponding to a cyclic subgroup H contains conjugacy classes. If the ingeter q = |NG(H)|/|CG(H)| (called the maturity discriminant) is less than an Euler function φ(|H|), the group |G| is concluded to be unmatured concerning H, where NG(H) and CG(H) respectively denote the normalizer and the centralizer of H within G. A matured representation defined for a matured or an unmatured group is subduced into cyclic subgroups to give the corresponding monomials, which are applied to the combinatorial enumeration of isomers.
Structure of Liquid Chloroform as Investigated by Energy-Dispersive X-Ray Diffraction
Authors: Takahashi Akinori , Yano Yohko F , Iijima Takao
Published: June 2006

The structure of liquid chloroform has been investigated by energy-dispersive X-ray diffraction. For the stability of the sample thickness, even for a volatile liquid, a glass capillary tube has been used as a sample container. The intensity function has been accounted for by a bcc (body-centered cubic)-like local lattice structure model with a lattice constant of 6.24 Å. However, it has been necessary to replace a fraction (34%) of the nearest neighbors by super-near configurations in which molecules are rather tightly correlated. The correlation is, however, rapidly lost as the distance between molecules increases, and the long range structure is characterized by a large Prins parameter. The structure of liquid chloroform is much less ordered than that of carbon tetrachloride.
Ab Initio Size-Consistent Calculations of Effective Exchange Interactions in Mesoscopic Magnetic Clusters Composed of Triplet Methylenes and Quartet Nitrogen Atoms
Authors: Kawakami Takashi , Yamanaka Syusuke , Takano Yu , Yoshioka Yasunori , Yamaguchi Kizashi
Published: June 2006

The electronic structures of linear magnetic clusters composed of eleven triplet methylenes, eleven quartet nitrogen atoms, and five triplet methylenes plus six quartet nitrogen atoms were investigated by the unrestricted Hartree–Fock (UHF), post UHF and their spin-projected wavefunctions in combination with the Heisenberg model. The effective exchange integrals (Jab) in the Heisenberg model were calculated by the difference between the total energies of the highest spin (HS) and lowest spin (LS) UHF-based wavefunctions of the clusters. The Jab values by the UHF-based and spin-polarized DFT methods were compared with those of the SO-Cl, MRSDCI, CASSCF, CASPT2, and MRMP2 calculations in the case of small linear clusters, such as a triplet methylene dimer. The spin-polarized density functional (BLYP and B3LYP) calculations followed by the size-consistent spin projection were carried out for dimer, trimer, and clusters with eleven magnetic sites to obtain the Jab values, since the DFT methods were heavily utilized in solid state physics. It was found that all of the methods, except for DFT, provide similar Jab values in the magnetic region of the dimer, where the interatomic distance is longer than 3.0 Å. However, the spin crossover from the LS state to the HS state occurs at a larger distance in the cases of MRSDCI and MRMP2. The spin projection for LS spin-polarized wavefunctions becomes less important in the case of long linear clusters, such as (CH2)11. The DFT results are generally biased to stabilize the low-spin states. The implications of the calculated results are discussed in relation to the molecular magnetisms in mesoscopic molecular aggregates.
Molecular Structures of Some syn-[1.1]Metallocenophanes, anti-Ferrocenium[1.1]ruthenocenophane, and Their NMR Spectroscopies
Authors: Watanabe Masanobu , Sato Masaru , Nagasawa Akira , Motoyama Izumi , Takayama Toshio
Published: June 2006

The structures of ferroceno[1.1]ruthenocenophane-1,13-dione (1a) and related compounds have been analyzed by X-ray diffraction. The crystal form of 1a is orthorhombic, space group Pbc21, a = 6.0660(3), b = 13.371(1), c = 19.420(2) Å, V = 1575.1(2) Å3, and the final R = 0.043 and Rw = 0.054. The air-oxidation of ferroceno[1.1]ruthenocenophane (2a) in xylene at 400 K gives ferroceno[1.1]ruthenocenophane-1-one (3a), implying the oxidation of the methylene group to a carbonyl group. The crystal form of 3a is orthorhombic, space group Pbn21, a = 7.6460(7), b = 10.708(1), c = 19.587(2) Å, V = 1603.7(3) Å3, and the final R = 0.052 and Rw = 0.051. The same oxidation is found for [1.1]ferrocenophane (2b) giving [1.1]ferrocenophane-1-one (3b). The crystal form of 3b is orthorhombic, space group Pbnm, a = 7.5460(9), b = 10.6560(6), c = 19.8290(7) Å, V = 1594.4(2) Å3, and the final R = 0.070 and Rw = 0.077. All the structural data of 1a, 3a, and 3b showed their syn conformation about two bridging methylene groups and rigid structures caused by the good planarity of C5H4COC5H4 and C5H4CH2C5H4 planes. These rigid structural features give remarkable variable temperature NMR (VT-NMR) spectra caused by the appropriate rate constant of syna⇔synb motion in solutions. The ΔG‡(Tc) values of the motion are estimated to be about 60 kJ mol−1, which is more than six times larger than those of 2a and 2b. The anti-form of ferrocenium[1.1]ruthenocenophane formulated as [FeIII(C5H4CH2C5H4)2RuII]PF6 (4) was prepared by the oxidation of the syn-form 2a in sulfuric acid containing NH4PF6. This is the first example of the oxidative occurrence of the conformational change from syn- to anti-form. The crystal form of 4 is triclinic, space group P1, a = 9.350(2), b = 10.777(3), c = 10.980(3) Å, α = 91.84(3)°, β = 96.66(2)°, γ = 111.12(2)°, V = 1021.8(5) Å3 and the final R = 0.044 and Rw = 0.048. The cation contains largely twisted C5H4CH2C5H4 plane (the twist angle, 34.1—38.5°) and largely tilted and rotated Cp-rings of the Ru(C5H4)2 moiety.
Preparation, Characterization, and Some Properties of Novel Dinuclear Complexes with a Coordinated Bridging Disulfide Bond. Crystal Structures of ΔRΛS-[M2(2-aminoethanethiolato)4(cystamine)]2+ (M = IrIII, RhIII)
Authors: Miyashita Yoshitaro , Sakagami Narumi , Yamada Yasunori , Konno Takumi , Okamoto Ken-ichi
Published: June 2006

Novel dinuclear complexes, [M2(aet)4(cysta)]2+ (M = IrIII (1), RhIII (2); aet = NH2CH2CH2S−, cysta = NH2CH2CH2SSCH2CH2NH2), were prepared by the oxidation reactions of fac(S)-[M(aet)3]. The crystal structures of the complexes were determined by X-ray diffractions: 1Cl2·4H2O, monoclinic, P21/a, a = 12.427(2), b = 8.879(1), c = 13.387(1) Å, β = 91.947(10)°, V = 1476.3(3) Å3, Z = 2, and R = 0.031; 2Cl2·2H2O, monoclinic, P21/c, a = 11.788(2), b = 8.485(1), c = 14.800(2) Å, β = 112.980(9)°, V = 1362.9(3) Å3, Z = 2, and R = 0.023. In the structures of 1 and 2, two octahedral fac(S)-[M(aet)3] units are linked by a coordinated disulfide bond. Their disulfide sulfur atoms are bound to the Ir and Rh atoms more strongly than to the Co atom. Both complexes 1 and 2 take only the ΔRΛS configuration of ten possible isomers. The electronic absorption, 13C NMR, and infrared spectra exhibit characteristic behavior in relation to the disulfide bond. 1 and 2 are fairly stable in water, and their structures in solid are retained in solution. The reduction or oxidation of the dinuclear complexes causes a cleavage of the disulfide bond to afford the mononuclear thiolato or sulfinato complexes. The properties of the present complexes are also discussed in comparison with those of the mononuclear and/or polynuclear complexes with the corresponding metal ions.
Dinitrogen Tetraoxide Complexes of Iron(III) and Copper(II) Nitrates as Versatile Reagents for Organic Syntheses. Efficient Oxidative Deprotection of Silyl or Tetrahydropyranyl Ethers, Acetals, and Thioacetals
Authors: Firouzabadi Habib , Iranpoor Nasser , Zolfigol Mohammad Ali
Published: June 2006

Fe(NO3)3·1.5N2O4 and Cu(NO3)2·N2O4 are efficient reagents for oxidative deprotection of various silyl and tetrahydropyranyl ethers, acetals, and thioacetals in aprotic organic solvents. Fe(NO3)3·1.5N2O4 is also able to perform the reactions efficiently in the absence of solvents at room temperature. Over-oxidation of the products has not been observed in these reactions. A synergic effect of N2O4 upon the oxidation abilities of metal nitrates is observed.
Lewis Acid-Promoted Disproportionation Reaction of Aromatic Vinyl Ethers and Acetals and Its Application to the Synthesis of Paracotoin
Authors: Gong Young Dae , Tanaka Hiroko , Iwasawa Nobuharu , Narasaka Koichi
Published: June 2006

Aromatic vinyl ethers and acetals underwent a novel addition-fragmentation reaction affording olefins and esters in the presence of a Lewis acid. This reaction was applied to intramolecular cyclization reaction, giving five or six membered ring compounds in good yields. Paracotoin, an intermediate in the biosynthesis of shikimic acid, was synthesized using this cyclization reaction as the key step.
Saccharide Induction of Chiral Orientation of the Aggregate Formed from Boronic-Acid-Appended Amphiphiles
Authors: Kimura Taro , Takeuchi Masayuki , Shinkai Seiji
Published: June 2006

A boronic-acid-appended amphiphile bearing an azobenzene chromophore at the chain center, N-[4-(dihydroxyboryl)benzyl]-N-(10-{4-[(4-dodecyloxyphenyl)azo)]phenoxy}decyl)-N,N-dimethylammonium bromide (4) was synthesized. In aqueous media, compound 4 formed a scarcely-oriented aggregate in the absence of saccharides, but in the presence of saccharides the boronic acid groups formed saccharide complexes and the resultant amphiphiles formed well-ordered aggregates. The ΔH value in DSC depended on the inherent structure of the added saccharides. Although d-glucose and methyl α-d-glucopyranoside could only form less ordered aggregates, d-fructose and d-xylose formed well-ordered aggregates. The saccharide complexes with 4 became CD-active with the appearance of exciton-coupling bands inherent to the saccharides. The CD band intensity was increased with increasing saccharide concentration but decreased by a further increase in the saccharide concentration. These results indicate that the reversible boronic acid–saccharide interaction is useful to induce the chirality in the ordered aggregate structure, where saccharides are used as a trigger for the chiral induction.
Photoreactivities of Contact Charge-Transfer Complexes between 1,1-Diarylethenes and Oxygen Molecules. Dimerization and Oxygenation Accelerated in Medium Polar Solvent
Authors: Kojima Masanobu , Ishida Akito , Takamuku Setsuo
Published: June 2006

The selective excitation of contact charge-transfer (CCT) bands of 1,1-diarylethenes [Ar = 4-MeOC6H4 (1a); 4-MeC6H4 (1b); Ph (1c)] with molecular oxygen in CH2Cl2 and MeCN resulted in the formation of the corresponding 3,3,6,6-tetraaryl-1,2-dioxanes (2) as a primary product, together with diaryl ketones (3). The reaction mechanism and intermediates for the production of 2 and 3 were studied in terms of the effects of the solvent polarity, additives, substituents on the aromatic rings, and the excitation wavelength on the product distribution, as well as in terms of the result of the photolysis of 2. On the basis of these results, it was shown that 2 was produced through dimer cation radicals of 1, whereas 3 was formed through the photolysis of 2 and the autoxidation of 1 initiated by neutral radical species, which must have been generated by the reaction of monomer cation radicals of 1 (1•+) with a superoxide anion radical. In particular, the formation of 2 depended to a large degree on the solvent polarity; namely, 2 was produced more efficiently in CH2Cl2 with moderate polarity rather than in MeCN with high polarity. Moreover, the reactivities of monomer and dimer cation radicals of 1 were investigated by γ-radiolyis and pulse radiolysis. For 1a and 1b, the transient-absorption spectra of their dimer cation radicals trapped by oxygen molecules were directly observed at 365 ns after pulse irradiation. The reactivities of 1•+ are also discussed based on the optimum structure, charge density, and spin density, obtained by semi-empirical molecular orbital calculations (PM3 method).
Regioselective Arylation Reactions of Biphenyl-2-ols, Naphthols, and Benzylic Compounds with Aryl Halides under Palladium Catalysis
Authors: Satoh Tetsuya , Inoh Jun-ichi , Kawamura Yoshiki , Kawamura Yuichiro , Miura Masahiro , Nomura Masakatsu
Published: June 2006

Biphenyl-2-ols undergo regioselective mono- and diarylation upon a treatment with aryl iodides in the presence of a palladium catalyst in DMF using Cs2CO3 as a base to produce 1,1′ : 2′,1″-terphenyl-2-ol and 2′,6′-diphenylbiphenyl-2-ol and their derivatives. The reaction of 1-naphthol selectively occurs at its 8-position to give 8-aryl-1-naphthols. In the reaction of 2-naphthol with aryl bromides, diarylated compounds, 1-(2-arylphenyl)-2-naphthols, are formed as the single major products. Under similar conditions, benzyl ketones, phenylacetonitrile, and methyl phenylacetate are arylated at their benzylic position.