bluuebunny/crossref_metadata_2025 huggingface dataset:
Electroreduction of μ-Oxo Iron(III) Porphyrins Adsorbed on an Electrode Leading to a Cofacial Geometry for the Iron(II) Complex: Unexpected Active Site for the Catalytic Reduction of O2 to H2O
Authors: Oyaizu Kenichi , Haryono Agus , Natori Junichiro , Shinoda Hiroshi , Tsuchida Eishun
Published: September 2002

Acidification of a solution of (μ-oxo)bis[(5,10,15,20-tetraphenylporphyrinato)iron(III)] ([{Fe(tpp)}2O], II) in CH2Cl2 produced equimolar amounts of a hydroxoiron(III) complex [(tpp)FeIII(OH)] (III) and an iron(III) complex [(tpp)FeIII(ClO4)] (IV). The complex IV was isolated as a perchlorate salt, which crystallyzed in the triclinic space group P1-(#2); a = 11.909(3), b = 19.603(4), c = 10.494(3) Å, α = 95.74(2)°, β = 107.91(2)°, γ = 89.14(2)°, V = 2319.1(9) Å3, Z = 2, Dcalc = 1.328 g cm-3, μ(Mo Kα) = 4.35 cm-1, final R = 0.055 and Rw = 0.050. The crystal structure of IV revealed that ClO4- is coordinated to the iron atom, which may be driven by the preference of iron(III) to be five coordinate rather than four coordinate. Reduction of the complex II in the presence of acid by electrolysis and/or by a reducing agent, such as sodium dithionite, under argon produced [FeII(tpp)]. The addition of O2 to a solution of [Fe(tpp)] in acidic CH2Cl2 in the presence of an equimolar amount of the reducing agent produced the complex III. When the complex II was adsorbed on an electrode surface and placed in aqueous acidic electrolyte solutions, electroreduction of the adsorbate proceeded according to the half-reaction:

[{Fe(tpp)}2O]+2H++2e-→2[Fe(tpp)]+H2O, at 0.031—0.059 pH V (vs. SCE, pH>1.0). Based on these results, oxo-bridged iron(III) porphyrin dimers were used as electrocatalysts for the reduction of O2. The catalytic reduction of O2 proceeded at potentials in the vicinity of those for II. As a whole, the proportion of H2O as the product increased from 50% for adsorbed [(tpp)FeIIICl] to >90% for the adsorbed dimer. Thus, electroreduction of the dimer adsorbed on a carbon electrode immersed in aqueous acid produced two solid state, cofacially fixed iron(II) porphyrin molecules:

[PFeIIIOfeIIIP]ad+2H++2e-→[PFeII FeIIP]ad+H2O (P = porphyrin dianion). Coordination of molecular oxygen to the adjacent two iron(II) centers under acidic conditions allowed formation of O2-bridged iron(III) porphyrin [PFeIII(O2)FeIIIP]ad at the electrode surface. Electroreduction of the adsorbate under acidic conditions produced H2O and allowed the reformation of [PFeII FeIIP]ad. The implication is that the electroreduction of the adsorbed oxo-bridged dimer gives a cofacial geometry for PFeII on the electrode, facilitating the coordination and subsequent splitting of O2.
Extraction of Alkali Metal Ions and Tetraalkylammonium Ions with Ionic Surfactants Containing a Poly(oxyethylene) Chain
Authors: Sakai Yukio , Ono Kanako , Hidaka Tamotsu , Takagi Makoto , Cattrall Robert W
Published: September 2002

The effect of the poly(oxyethylene) (POE) chain length of ionic surfactants, expressed as C12H25-(OCH2CH2)-nOCH2C6H3(OH)(NO2) (n = 2—9), on the extraction of monovalent cations, including alkali metal and tetraalkylammonium (TAA) ions, was investigated. The extraction constants (Kex) with surfactants having a POE chain of n ≥ 6 were almost constant for each alkali metal ion. The Kex sequence was Li+ < Na+ < Cs+ ≤ K+ = Rb+. The extractability and selectivity largely decreased as n in the surfactant decreased (n < 6). The effect of the POE chain length was related to the stability of the alkali metal-POE complex. Unlike an alkali metal ion, the Kex values for all TAA ions were almost constant with surfactants of n = 2—8. These facts indicated that the surfactant extracts alkali metal ions by both complex formation with its POE chain and ion-pair formation with a terminal p-nitrophenolate anion. On the other hand, TAA ions were extracted simply by ion-pair formation with a p-nitrophenolate anion of the surfactant. The proposed structures are discussed from the viewpoint of the spectrum shift of the extracted species.
Solvent Extraction of Chromium(III) Perchlorate, Thiocyanate, Nitrate, Bromide, and Iodide with Trioctylphosphine Oxide in Hexane
Authors: Kusakabe Satoshi
Published: September 2002

Chromium(III) ion was extracted from aqueous 1 mol dm-3 NaX (X- = ClO4-, SCN-, NO3-, Br-, and I-) solutions with trioctylphosphine oxide (TOPO) in hexane at 298 K. The extraction was rapidly equilibrated, except from a NaNO3 solution. The number of TOPO molecules solvating to the extracted chromium(III) perchlorate and thiocyanate was 6. That to the bromide and iodide was 5. That to the nitrate was 5 at the beginning of extraction, and changed to 3 within a few hours of two-phase agitation. The hydration number of extracted Cr(ClO4)3·6TOPO was 17.2±0.5. The different solvation number of TOPO among these salts is supposed to be an unstable second hydration sphere of the extracted chromium(III) ion, which may be easily removed by the counter anions.
Fractional Distributions of Major-to-Ultratrace Elements in Coastal Seawater and Their Partitionings in Laboratory-Made Salts as Investigated by Inductively Coupled Plasma Atomic Emission Spectrometry and Inductively Coupled Plasma Mass Spectrometry with Aid of Membrane- and Ultra-filtration Techniques
Authors: Ji Shan , Yabutani Tomoki , Itoh Akihide , Haraguchi Hiroki
Published: September 2002

The coastal seawater sample was filtered with a membrane filter (pore size 0.45 μm), and the filtrate was further filtered with an ultrafiltration filter (molecular weight permeation limit of 10000 Da). Then, major-to-ultratrace elements in the particles which remained on the membrane filter, the membrane-filtered seawater, and the ultrafiltered seawater were determined by ICP-AES (inductively coupled plasma atomic emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). From these analytical results, the fractional distributions of each element in the particle, large molecule and small molecule fractions of seawater were estimated, where the distributions of the elements in the large molecule fraction were obtained as the differences between the elemental concentrations in membrane-filtered and ultrafiltered seawaters.

Furthermore, laboratory-made salts (Salts I—III) were prepared from original, membrane-filtered, and ultrafiltered seawaters. The concentrations of major-to-ultratrace elements in laboratory-made salts were also determined by ICP-AES and ICP-MS. It was found that alkali metals, alkaline earth metals, oxoanion-forming elements (V, Mo, W, U) and Cd were mostly contained in the small molecule fraction of seawater, and ca. 95—100% of them in salt, except for V, originated from those in the small molecule fraction. More than 50% of Al, Mn, Fe, Co, Ga, Y, rare earth elements (REEs) and Pb were contained as the particle constituents in seawater, but their intakes into salt were less than 50%. In addition, the fractional distributions of the following elements in the large molecule fraction of seawater were: Al 10%, Mn 4%, Fe 2%, Cu 23%, Zn 7%, Y 5%, REEs 3—15%, and Pb 30%. On the other hand, the intake factors of these elements in salt from the large molecule fraction were: Al 40%, Mn 5%, Fe 28%, Cu 20%, Zn 30%, Y 7%, REEs 5—30%, and Pb 55%. The results obtained in the present experiment suggest that the distributions of the elements in natural salt greatly depend on the chemical forms in seawater.
Chemical Approach to the Cu(II)-Phenoxyl Radical Site in Galactose Oxidase: Dependence of the Radical Stability on N-Donor Properties
Authors: Shimazaki Yuichi , Huth Stefan , Hirota Shun , Yamauchi Osamu
Published: September 2002

Copper(II) complexes of several new N3O-type tripodal ligands, 2,4-di(t-butyl)-6-{[bis(2-pyridyl)methyl]aminomethyl}phenol (HtbuL), 2,4-di(t-butyl)-6-{[(6-methyl-2-pyridyl)methyl](2-pyridylmethyl)aminomethyl}phenol (HtbuL(Mepy)), 2,4-di(t-butyl)-6-{bis[(6-methyl-2-pyridyl)methyl]aminomethyl}phenol (HtbuL(Mepy)2), and 2,4-di(t-butyl)-6-{[(1-methyl-2-imidazolyl)methyl][(6-methyl-2-pyridyl)methyl]aminomethyl}phenol (HtbuL(im)(Mepy)), were prepared. They were structurally characterized by the X-ray crystallographic method to have a square-pyramidal structure with a weakly coordinating group at an apical position. The phenol moiety of [CuCl(tbuL(Mepy))] (2), [CuCl(tbuL(Mepy)2)] (3), and [CuCl(tbuL(im)(Mepy))] (4) was revealed to be coordinated equatorially; it was converted to the phenoxyl radical upon oxidation with Ce(IV), giving a new absorption peak at 405—420 nm. ESR measurements at low temperatures and resonance Raman spectra established that the radical species has a Cu(II)-phenoxyl radical bond. The cyclic voltammograms exhibited a quasi-reversible redox wave at E1/2 = 0.56—0.61 V (vs. Ag/AgCl) corresponding to the formation of the phenoxyl radical, which displayed a first order decay with a half life of 65 and 62 min at -20 °C for 2 and 4, respectively, while that for 3 was only 9.0 min at -40 °C. The radical stability increased with the donor ability of the equatorial N ligands.
Characterization of LaCrO4 and NdCrO4 by XRD, Raman Spectroscopy, and ab Initio Molecular Orbital Calculations
Authors: Aoki Yoshitaka , Konno Hidetaka , Tachikawa Hiroto , Inagaki Michio
Published: September 2002

Single phase LnCrO4 (Ln = La-Nd) compounds were attempted to synthesize by the pyrolysis of precursors prepared from LnIII-CrVI mixed solutions. Only LaCrO4 and NdCrO4 were obtained as a single phase. LaCrO4 was monazite type (monoclinic, P21/n), as reported, and the cell parameters were refined to be a = 0.70369, b = 0.72348, c = 0.66918 nm and β = 104.950° by an X-ray Rietveld method. NdCrO4 was zircon type (tetragonal, I41/amd) and the cell parameters were a = 0.73107 and c = 0.66999 nm. It was found that CrO43- tetrahedra in LaCrO4 have C1 symmetry and the four Cr-O bond lengths are different, whereas those in NdCrO4 have D2d symmetry and all Cr-O bond lengths are 0.1702 nm. Detailed Raman spectra of LaCrO4 and NdCrO4 were measured and assigned to the vibrational modes of the CrO43- tetrahedra. Molecular orbital calculations indicated that the charge density on the chromium ions in the tetrahedra is much less than the nominal 5+ due to the migratory electrons from oxygen atoms, and nearly the same irrespective of the symmetry of tetrahedron, suggesting that the Cr-O bonds are strongly covalent in nature.
A Strongly Coupled Mixed Valence State Between Ru3 Clusters. Intramolecular Electron Transfer on the Infrared Vibrational Time Scale in a Pyrazine (pz) Bridged Dimer of Triruthenium Clusters, [{Ru3(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)] (abco = 1-azabicyclo[2,2,2]octane)
Authors: Yamaguchi Tadashi , Imai Naoyuki , Ito Tasuku , Kubiak Clifford P
Published: September 2002

A pyrazine bridged dimer of triruthenium clusters [{RuIII2RuII(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)] (abco =1-azabicyclo[2,2,2]octane, pz = pyrazine) gives an inter-cluster mixed valence state upon one electron reduction. The splitting of the reduction waves in cyclic voltammetry, ΔE, was 470 mV. This corresponds to a comproportionation constant for formation of the mixed valence state of 9.0 × 107. The IR spectrum of the mixed valence species in the ν(CO) region, measured by reflectance IR spectroelectrochemistry, showed a completely coalesced ν(CO) band. This represents delocalized redox behavior on the infrared vibrational timescale. The rate constant for intramolecular electron transfer was estimated to be 1 × 1012 s-1 at -18 °C by simulating the ν(CO) absorption bandshape. The mixed valence complex showed an intervalence charge transfer (ICT) band at 12500 cm-1. Hush analysis provides a spectroscopic estimate of HAB to be 2490 cm-1. Crystal structures of [{RuIII2RuII(μ3-O)(μ-CH3CO2)6(CO)(abco)}2(μ-pz)]·2CH2Cl2 and its precursor, [RuIII2RuII(μ3-O)(CH3CO2)6(CO)(abco)2]·CH2Cl2, were determined by X-ray crystallography. Trends in Ru-O(oxo) and Ru-O(acetate) distances in these compounds show that the divalent site is localized on the Ru center attached to the carbonyl ligand.
Chemical Stability of Large Organic Molecule-Metal Complexes Dissolved in Natural Water as Studied by Size Exclusion Chromatography/Inductively Coupled Plasma Mass Spectrometry
Authors: Itoh Akihide , Iwata Kosuke , Chiba Koichi , Haraguchi Hiroki
Published: September 2002

The chemical stability of large organic molecule-metal complexes (LOMMCs) dissolved in pond water were investigated by a hyphenated system of size exclusion chromatography/UV absorption detection/inductively coupled plasma mass spectrometry (SEC/UV/ICP-MS) after ultrafiltration using a filter with a molecular permeation limit larger than 10000 Da. LOMMCs dissolved in the preconcentrated pond water sample were observed at the retention times corresponding to molecular weights larger than 300000 Da (Peak I) and that of 10000—50000 Da (Peak II) in the chromatograms measured by UV absorption and ICP-MS. When the pH of the sample solution was varied from 7.0 to 0.5 by adding the HNO3 solution, the peak intensities of both Peak I and Peak II in these chromatograms decreased with the decrease in pH of the sample solution. These results indicate that LOMMCs were decomposed by addition of HNO3. Peak I was rapidly decomposed below pH 4, while Peak II was gradually decomposed over the pH range from 7.0 to 0.5. The decomposition curve of Peak I was similar to the solubility characteristics of hydroxides of Fe and Al. On the other hand, that of Peak II suggested the dissociations of metal complexes (Cu and Zn) with some biogenic organic molecules. It was concluded from these results that some colloidal particles of hydroxides of Fe and Al may be core materials of LOMMCs for Peak I, while some metal complexes with biogenic protein-like compounds may be LOMMCs for Peak II. The possible models for LOMMCs in pond water were proposed as ``a string-ball model'', which might interpret as the removal and preservation mechanisms for trace elements in natural water.
Novel Fluorescent Coumarin Reagents Appending 15-Crown-5 Ether for the Rapid and Self-Catalytic Derivatization of Carboxylic Acids
Authors: Masuda Toshinobu , Kaneko Takeshi , Tanaka Toshiharu , Goya Shujiro , Murata Chiyomi , Takadate Akira
Published: September 2002

Novel fluorogenic coumarin derivatives appending 15-crown-5 ether as more active catalytic site were designed and synthesized for the fluorescence derivatization of carboxylic acids. From the stability constants (Ks) for complexation with metal acetates in methanol, it was found that their catalytic abilities were superior to the corresponding benzo-15-crown-5 ether type reagent. However, the reactivity of these reagents in the derivatization of lauric acid was dependent on not only the catalytic ability of the introduced crown-ether but also on the appending position of that in a reagent molecule. Furthermore, the derivatized products showed remarkably high fluorescence quantum yields of above 0.8 in methanol and acetonitrile. Allowing to hold a certain function such as catalyst in a reagent molecule should serve as a new strategy for the development of excellent analytical reagents.
Synthesis, Crystal Structure, and Some Spectrochemical Properties of Optically Active S-Bridged Trinuclear Complex ΔΔ-[Ni{Co(aet)2(R-pn)}2]4+ (aet = 2-Aminoethanethiolate, R–pn = (R)–1,2-Propanediamine)
Authors: Yamada Yasunori , Maeda Yoko , Miyashita Yoshitaro , Fujisawa Kiyoshi , Konno Takumi , Okamoto Ken-ich
Published: September 2002

The reaction of cis-[CoCl2(R-pn)2]+ (R–pn = (R)–1,2-propanediamine) with [Ni(aet)2] (aet = 2–aminoethanethiolate) in water stereoselectively gave an S-bridged trinuclear complex, [Ni{Co(aet)2(R-pn)}2]4+, accompanied by the ligand-transfer of aet from Ni2+ to Co3+. The ΔΔ isomer of the trinuclear complex was selectively formed. The spectrochemical properties of theΔΔ isomer are also discussed in relation to the stereochemical behavior.
Conformational Studies of Cyclo(Pro-Leu-Aib)2by 1H Nuclear Magnetic Resonance Spectroscopy and Circular Dichroism
Authors: Wang Jun , Osada Satoshi , Kodama Hiroaki , Kondo Michio
Published: September 2002

The synthesis and conformational analysis of cyclo(Pro-Leu-Aib)2 by means of NMR technique are reported. The cyclohexapeptide was synthesized in the classical high-dilution solution method. Its yield in the cyclization reaction from linear hexapeptide active ester was lower than that of the analogous cyclo(Pro-Leu-Gly)2 previously reported. Two sets of amide proton signals for Leu and Aib in NMR spectra and temperature coefficients indicated an asymmetric conformation which contains both cis and trans Aib-Pro bonds. Here Pro amino acids occupy the positions i+2 of β-turns. The CD spectrum gave two negative bands at 202 and 230 nm, which is considered to be the sum of type II′ (when Aib-Pro is trans) and type VI (when Aib-Pro is cis) β-turns.
Practical Synthesis of (6-Chloro-3-pyridyl)methylamine by Highly Selective Hydrogenation of 6-Chloro-3-pyridinecarbonitrile with Improved Raney Nickel Catalyst
Authors: Tanaka Ken , Nagasawa Minoru , Sakamura Hideki
Published: September 2002

A practical synthesis of (6-chloro-3-pyridyl)methylamine (1), one of the key intermediates of neo-nicotinoid insecticides, by a highly selective hydrogenation of 6-chloro-3-pyridinecarbonitrile (4) is described. The use of an improved Raney nickel catalyst, prepared from an alloy of low nickel content (Ni 38%, Al 62%) and subjected to heat treatment in water (98 °C, 2 h) after leaching of aluminum, was highly effective for the selective hydrogenation of 4. The hydrogenation of 4 using this catalyst was carried out in EtOH-H2O [6 : 1 (v/v)] and NH3 at 50 °C and 1.2—1.4 kg cm-2 hydrogen pressure to give 1 in 86% yield and 3-pyridylmethylamine, a dechlorinated by-product, in 2% yield.
Structural/Physicochemical Properties of Corycavidine, a Key Intermetabolite in the Biosynthesis of Isoquinoline Alkaloids, Elucidated by X-Ray Crystallography, Solution Conformation and Thermal Behavior Analyses, and Energy Calculations
Authors: Kamigauchi Miyoko , Yoshida Mayumi , Saiki Kayoko , Sugiura Makiko , Nishijo Jujiro , In Yasuko , Ishida Toshimasa
Published: September 2002

The conformational/physicochemical features of corycavidine (1), 5,7,8,15-tetrahydro-3,4-dimethoxy-6,15-dimethyl-[1,3]benzodioxolo[5,6-e] [2]benzazecin-14(6H)-one, an important protopine-type alkaloid that serves as the key intermetabolite in the biosynthesis of isoquinoline alkaloids, were examined by X-ray crystallography, 1H NMR spectroscopy, as well as thermal analysis and energy calculations. Two stable conformations of 1, as proposed by energy calculations, were also observed in both the crystalline and solution states. Racemization of optically active 1, which was caused by heating of the crystal, was analyzed by differential-scanning calorimetry. By taking advantage of the H-2H replacement reaction at the C13 atom of 1, the rate of racemization in the C2H3O2H/NaO2H solution was measured as a function of the temperature; the energy barrier between both enantiomers was estimated to be 4.7 kcal mol-1. The crystallization of racemic 1 led to two different crystal forms, i.e., the racemic crystal and the conglomerate crystal (1 : 1 mixture of both enantiomeric crystals). This was probably due to the low energy difference between both crystals. These physicochemical behaviors are important for understanding the in vivo nonenzymatic racemization of 1 and its related alkaloids during metabolic processes.
Acylthio- and Thioacylthiophosphines [(RCES)nPPh3-n, E = O, S; n = 1—3]: Synthesis and Structural Analysis
Authors: Tani Kazuyasu , Matsuyama Kazuo , Kato Shinzi , Yamada Kohzaburo , Mifune Hirotaka
Published: September 2002

Stoichiometric reactions of alkali metal thio- and dithiocarboxylates with Ph2PCl, PhPCl2, and PBr3 gave the corresponding acylthio- and thioacylthiophosphines [(RCES)nPPh3-n, E = O, S; n = 1—3] 3—8 in moderate to good yields. The structures of (4-CH3C6H4COS)nPPh3-n (3d: n = 1, 4d: n = 2, 5d: n = 3) and (4-CH3C6H4CS2)2PPh (7b) were analyzed by X-rays. In the thiocarboxylate derivatives 3d, 4d, and 5d, the intramolecular interactions between the carbonyl oxygen and the central phosphorus atoms are weak and the thiocarboxylato ligands act as monodentates through the sulfur atoms. Similarly, in the dithiocarboxylate derivative 7b, the intramolecular interactions between the thiocarbonyl sulfur and the central phosphorus atoms are weak and the dithiocarboxylato ligands act as monodentates. The covalent phosphorus-sulfur and/or phosphorus-phenyl ipso-carbon bonds are nearly at right angles to one another, forming a distorted tetrahedron with the unshared electron pair orbital at the apex. The 31P NMR spectra of the thiocarboxylic acid derivatives 3—5 show downfield shifts with an increase in the number of thiocarboxylato ligands, whereas those of the dithiocarboxylic acid derivatives 6—8 show upfield shifts.
Evaluation of the Relative Magnitude of the β-Effect of Silicon and the γ-Effect of Tin by Intermolecular Competition
Authors: Sugawara Masanobu , Yoshida Jun-ichi
Published: September 2002

The relative magnitude of the β-effect of silicon and the γ-effect of tin was evaluated by intermolecular competition. An acetal was allowed to react with a 1 : 1 mixture of an allylsilane and a homoallylstannane in the presence of TMSOTf (trimethylsilyl trifluoromethanesulfonate); the former was found to be more reactive than does the latter, indicating that the β-silyl group activates the carbon-carbon double bond more effectively than the γ-stannyl group. This is consistent with the results of molecular-orbital calculations which indicate that the HOMO level of the allylsilane is higher than that of the homoallylstannane. The intermolecular competition between a homoallylstannane and a terminal alkene toward electrophilic reactions with an acetal have revealed that the former is more reactive than the latter. This result indicates that the stannyl group at the γ-position definitely activates the carbon-carbon double bond toward electrophiles.
Synthesis and Structural and Electronic Properties of the Mixed Complexes of Vinylene-Bridged Bis- and Tris(octaethylporphyrin)s with Ni(II), Pd(II), and Pt(II) Ions
Authors: Higuchi Hiroyuki , Shinbo Masatoshi , Usuki Masanobu , Takeuchi Makoto , Tani Keita , Yamamoto Koji
Published: September 2002

Various mixed complexes of vinylene-bridged bis- and tris(octaethylporphyrin)s (bis(OEP)-(M1-M2) and tris(OEP)-(M1-M2-M3)) with d8 transition-metal ions M(II) (M: M1, M2, and M3 = Ni or Pd or Pt) were synthesized by step-by-step and selective metallations of the respective free-bases (FB) with limited amounts of the metallation reagent. Metallation of tris(OEP)-(H2-H2-H2) started in the central OEP ring, with the vinylene linkages of the product retaining the same (E,E)-configuration as those in FB. On the other hand, metallation of (E)-bis(OEP)-(H2-H2) afforded the corresponding (E)-bis(OEP)-(M1-M2) predominantly, while metallation of (Z)-bis(OEP)-(H2-H2) was accompanied by a ready isomerization of the vinylene linkage to afford each pair of (E)- and (Z)-isomeric complexes under the similar conditions. Electronic absorption spectra of tris(OEP)-(M1-M2-M3) proved to be affected especially by the central OEP-M2 ring and by the heavier metals more intensively, resulting in the largest splitting of the Soret band for the Ni-Pd-Pt complex. Examination of the oxidation potential E1 values indicated that the electron-releasing abilities of tris(OEP)-(M1-M2-M3) are intensively reduced for the complex carrying at least two consecutive heavier metal OEP rings. In the case of bis(OEP)-(M1-M2), the (E)-isomeric series exhibited the reduction of the electron-releasing abilities regularly in order of the heavy metal complexes similarly to tris(OEP)-M, while the (Z)-isomeric series exhibited little dependence of the electron-releasing abilities upon the incorporated metals M.
Enhancement of Catalytic Activity of Chemically Modified Subtilisin Carlsberg in Benzene by Adjustment of Lyophilization Conditions
Authors: Kwon Oh Hyeong , Imanishi Yukio , Ito Yoshihiro
Published: September 2002

Alteration of the lyophilization conditions significantly enhanced not only the activity of insoluble native subtilisin Carlsberg but also that of solubilized enzyme in benzene. The catalytic activity (kcat/Km) for the transesterification reaction of N-acetyl-L-phenylalanine ethyl ester with 1-propanol in benzene was enhanced more than 1000 times by the solubilization (100-fold enhancement) and the adjustment of lyophilization conditions (10-fold enhancement). Subtilisin Carlsberg was modified with polyethylene glycol (PEG-Sub) so that it could be solubilized in organic solvents. The effects of pH of the aqueous enzyme solution, of salts, or of a substrate analog in the aqueous solution before the lyophilization process, on the catalytic activity of native subtilisin and PEG-Sub were investigated. The activities of both the native subtilisin and PEG-Sub depended on the pH. The activities of both PEG-Sub and the native subtilisin were enhanced by the presence of salts. The presence of a substrate analog, N-Ac-L-Phe, also enhanced the activity of the native subtilisin and PEG-Sub. These results demonstrated that the organic solvent-solubilized subtilisin was affected by the lyophilization conditions.
Effects of the Noncyclic Cyanamides on the Retrogradation of Waxy Corn Starch
Authors: Ogawa Kazuo , Aso Kenji , Ono Shin , Yoshimura Toshiaki , Rengakuji Seichi , Nakamura Yuuko , Yamazaki Isao , Murotani Satoru , Shimasaki Choichiro
Published: September 2002

The suppressive effects of noncyclic cyanamides (guanidine hydrochloride, urea, and thiourea) on the retrogradation of waxy corn starch (WCS) gel were examined using differential scanning calorimetry and X-ray powder diffraction. We demonstrated that thiourea, guanidine hydrochloride, and urea effectively suppressed the retrogradation of the WCS gel in this order.
Catalytic Activity of Rare Earth-Promoted SO42-/SnO2in the Oxidative Dehydrogenation of Ethylbenzene
Authors: Jyothi Thundi Madathil , Sreekumar Kurungot , Talawar Mahadev B , Belhekar Anagha Ashok , Rao Bollapragada S , Sugunan Sankaran
Published: September 2002

Rare earth-promoted (10%) sulfated SnO2 catalysts were prepared by different methods and have been characterized by employing XRD, SEM, Mercury porosimetry, BET surface-area analysis, TG-DTA, and IR spectroscopy. The strength of generated acid sites depends on the preparation method. A thermogravimetric analysis revealed that the removing the sulfate species from the catalyst surface took place at temperatures > 1193 K. The adsorption of butylamine and acetic acid was used to probe the acid-base properties of the catalysts. The catalytic activity of these materials in the oxidative dehydrogenation of ethylbenzene was tested at different temperatures. It was found that rare earth-modified sulfated tin oxide catalysts are more active when compared to the corresponding mixed-oxide systems and sulfated tin oxide. The combined effect of rare earth oxide and the sulfate anion leads to a enhanced oxidation activity. The existence of strong acid sites generated as a result of a sulfate treatment is involved in the activation of ethylbenzene; the addition of rare earth oxides brings about an enhancement of the reaction between the adsorbed oxygen atoms and the adsorbed ethylbenzene.
Preparation and Structure of [RhCl(nbd)(dmap)] (nbd = bicyclo[2.2.1]hepta-2,5-diene; dmap = 4-(N,N-dimethylamino)pyridine)
Authors: Takenaka Yasumasa , Osakada Kohtaro
Published: September 2002

4-(N,N-Dimethylamino)pyridine (dmap) reacts with [{RhCl(nbd)}2] to give [RhCl(nbd)(dmap)] (1), which was characterized by X-ray crystallography and NMR spectroscopy. The crystal structure and dynamic behavior of the molecule in solution are compared with those of [RhCl(nbd)(PPh3)] (2).
Behavior and Origin of Atmospheric NO2, SO2, and O3 in Mountains around the Kyoto Basin
Authors: Yamada Etsu , Kimura Mitsuo , Tomozawa Kenichi , Fuse Yasuro , Yamada Takeshi
Published: September 2002

The behavior and origin of atmospheric NO2, SO2, and O3 in mountains around the Kyoto basin were investigated by using passive samplers. Since these samplers are compact and need no batteries or pumps, they are appropriate for the measurement of atmospheric NO2, SO2, and O3 at low-level concentrations in mountains or forests. The sampling sites were Mt. Hiei, Mt. Daimonji, and 7 other mountains around the Kyoto basin, and 4 clean sites (Seryu, Kuroda, Sasari, Ashu) located about 20—30 km north of the Kyoto basin. The concentrations of atmospheric NO2, SO2, and O3 in mountains on three sides of the Kyoto basin were almost the same at the same altitude in the same season. The source of atmospheric NO2 in mountains around the Kyoto basin may be anthropogenic emission from automobiles or industrial areas, and NO2 concentration at clean sites far away from the Kyoto basin may become lower due to the diffusion of NO2. O3 concentration was higher as the altitude increased. Atmospheric O3 at mountains around the Kyoto basin has its origin in both stratospheric input and O3 production by photochemical reactions.
Synthesis of a Soluble Precursor Possessing an Nb-N Backbone Structure and Its Pyrolytic Conversion into Niobium-Based Ceramics
Authors: Cheng Fei , Sugahara Yoshiyuki , Kuroda Kazuyuki
Published: September 2002

Synthesis and pyrolysis of a soluble precursor possessing an Nb-N backbone structure were investigated. The precursor was prepared by aminolysis reaction of tetrakis(diethylamido)niobium with isopropylamine. The precursor was soluble in benzene, and had a polymeric structure possessing Nb-N-Nb imido-bridges. The precursor was pyrolyzed under NH3-N2 (at 600 °C for 2 h under NH3 and subsequently at 1350 °C for 8 h under N2) and Ar (at 1500 °C for 2 h) atmospheres. δ-NbN was obtained as a main crystalline phase after the pyrolysis of the precursor under NH3-N2, whereas pyrolysis of the precursor under Ar led to the formation of NbC as the only crystalline phase. More than 90% of niobium which was present in the precursor remained in both of the pyrolyzed products.
Photo- and Mechano-Catalytic Overall Water Splitting Reactions to Form Hydrogen and Oxygen on Heterogeneous Catalysts
Authors: Domen Kazunari , Kondo Junko N , Hara Michikazu , Takata Tsuyoshi
Published: September 2002

Recent progress of overall water splitting by photocatalysts and mechanocatalysts is briefly reviewed. In photocatalytic reactions, several new materials have been introduced, and the catalyst preparation has also been improved. As a result, a high quantum efficiency for overall water splitting of about 30% has been accomplished. In addition, recent progress in the understanding of the reaction mechanism is briefly introduced.

On the other hand, mechano-catalytic overall water splitting reaction has been recently discovered by the authors. The phenomenological aspects of this novel reaction are summarized, and some implications of the reaction mechanism are also described.
Mass-Spectrometric Study on Ion-Molecule Reactions of CH5+, C2H5+, and C3H5+ with Monosubstituted Benzenes Carrying a Hydroxy Group
Authors: Tsuji Masaharu , Arikawa Takeshi , Nishimura Yukio
Published: September 2002

The gas-phase ion-molecule reactions of CH5+, C2H5+, and C3H5+ with four monosubstituted benzenes carrying a hydroxy group in the substituent [PhX : X = OH, CH2OH, CH2CH2OH, and CH(OH)CH3] have been studied under a reactant-ion selective chemical ionization mode of an ion-trap type of GC/MS. The major product channel for PhOH is non-dissociative proton transfer leading to (M+H)+ ions, while that for the other three reagents is dissociative proton transfer leading to (M + H-H2O)+ ions in most cases. Small amounts of dissociative alkylation channels are found in some reactions with C2H5+ and C3H5+. The reaction mechanism is discussed based on the dependence of product-ion distributions on the reaction time and semi-empirical calculations of the energies of intermediates and products.
The Experimental Deformation Electron-Density Distributions of 4-Arylmethyleneamino-2,2,6,6-tetramethyl-1-piperidyloxyl (TEMPO) Radicals: Relations between Electron Densities and Intermolecular Interactions
Authors: Yasui Masanori , Kan-nari Eiji , Ishida Takayuki , Nogami Takashi , Iwasaki Fujiko
Published: September 2002

Some of the 4-arylmethyleneamino-TEMPO radicals (TEMPO = 2,2,6,6-tetramethyl-1-piperidyloxyl), such as 4-(4-chlorobenzylideneamino)TEMPO (1) and 4-(benzylideneamino)TEMPO (2), showed intermolecular ferromagnetic interactions at an extremely low temperature. The experimental electron-density distributions of these compounds were investigated by the X-ray diffraction method. Intensity data were measured at 100 K up to 2θmax (Mo K  α) = 120° and 95° for 1 and 2, respectively. Deformation electron-density distributions were calculated from the structure factors after the refinements by the multipole expansion method. These electron-density distributions suggested that the unpaired electron of the O radical atom was not located on the O atom, but was rather located in the π*-orbital of the N-O bond. Lone-pair densities of the radical O atom are located in the >N-O plane showing the sp2 hybridization. From the crystal structures, it has been proposed that the ferromagnetic interactions are transferred through CH…O interactions between radical O atoms and β-H atoms of the neighboring TEMPO rings. The β-H atoms of the neighboring TEMPO rings contact with the O atom in the direction toward the π*-orbital of the N-O bond, not in the direction of the lone-pair densities of the O atom. The present studies support the mechanism of the intermolecular ferromagnetic interactions through the β-H atoms. Studies of electron densities from the view point of the intermolecular interactions are important.
Effect of C132-Stereochemistry on the Molecular Properties of Chlorophylls
Authors: Furukawa Hiroyasu , Oba Toru , Tamiaki Hitoshi , Watanabe Tadashi
Published: September 2002

To elucidate the origin of differences in the monomeric properties of chlorophyll a and a′ (Chl a/a′; C132-(R/S)-epimers of Chl a), a series of Zn-Chl derivatives possessing a variety of C134 substituents were prepared. The (S)-epimers gave absorption and emission bands at slightly longer wavelengths than the corresponding (R)-epimers. The (S)-epimers had more intense CD peaks than the (R)-epimers. In comparison with Zn-Chl a/a′ (C134-Me), Zn-Chl with a bulky 2,4-dimethyl-3-pentyl moiety at the C134-position showed a greater difference between the 13C NMR chemical shifts of the epimers. These spectral differences between the (R)- and (S)-epimers were attributed to ruffling of the chlorin macrocycle, arising from a steric repulsion between the C132 and C17 moieties. The trend of the rate constant of epimerization, isomerization at the C132 position, in the C134-substituted Zn-Chls is in line with the above interpretation. The relationship between the spectroscopic and kinetic results and the distortion of the macrocycle is schematically represented.
Infrared Spectroscopic Study on Methane Adsorption Sites on Mesoporous Silicates
Authors: Yamazaki Tatsuya , Watanabe Michimasa , Saito Hiroaki
Published: September 2002

Some MCM-41 materials substituted by trivalent metal ion (Met-MCM-41; Met = Al, Fe, and Ga) were prepared, and their methane adsorption sites were investigated by IR spectroscopy. Three adsorption sites on Met-MCM-41 with different strengths of electric field were observed. They were assigned to pore wall site (0 V m-1), silanol site (ca. 4×109 V m-1), and Na+ site (ca. 6×109 V m-1), respectively. The amounts of silanol site in Met-MCM-41 were estimated to 2—3 mmol g-1, while the amounts of the Na+ site were 0.1—0.2 mol g-1. Methane molecules were preferentially adsorbed on the electrostatic sites (silanols and Na+sites) at low methane pressures, but as methane pressure increased, the amount of adsorption on the pore wall site became comparable to that on the silanol sites. Since the amounts of Na+ site estimated from methane adsorption on the Met-MCM-41 samples were less than the theoretical ones calculated from the compositions of starting materials, most of the Na+ sites were thought to be inaccessible for methane molecules.
Photosensitized Luminescence of Neodymium(III) Coordinated with 8-Quinolinolates in DMSO-d6
Authors: Iwamuro Mitsunori , Adachi Tomoko , Wada Yuji , Kitamura Takayuki , Nakashima Nobuaki , Yanagida Shozo
Published: September 2002

Some quinolinol derivatives possessing suitable triplet state energy were examined to sensitize the luminescence of neodymium ion (Nd(III)) as coordinating ligands. Photosensitized luminescence in the near-infrared region of four neodymium(III) complexes: tris(8-quinolinolato)neodymium(III) ([Nd(q)3]), tris(5,7-dichloro-8-quinolinolato)neodymium(III) ([Nd(Clq)3]), tris(5,7-dibromo-8-quinolinolato)neodymium(III) ([Nd(Brq)3]) and tris(5,7-diiodo-8-quinolinolato)neodymium(III) ([Nd(Iq)3]), were observed by selective excitation of the ligand moieties in DMSO-d6. Highly efficient intramolecular energy transfer from the excited ligand moieties to the central Nd(III) ion was successfully achieved by using the halogenated ligands.
Structures and Magnetic Properties of [o- and p-MePyNN+]2[Cu(ox)2] (MePyNN+ = Nitronyl Nitroxyl Radical Cation)
Authors: Oshio Hiroki , Yaginuma Taira , Ito Tasuku
Published: September 2002

Reactions of [o-MePyNN+]PF6 and [p-MePyNN+]PF6 with [n-Bu4N]2[Cu(ox)2] in acetonitrile yielded dark-blue crystals of [o-MePyNN+]2[Cu(ox)2]·2CH3OH (1) and [p-MePyNN+]2[Cu(ox)2]·2H2O (2), respectively, where [o-MePyNN+] or [p-MePyNN+] represents the 2-(2 or 4-N-methylpyridinium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazo-1-oxyl 3-oxide radical cation. X-ray structural analyses showed that the crystals of 1 and 2 are isomorphous. The coordination geometry of the Cu2+ ions in 1 and 2 is an elongated octahedron, and the equatorial and apical coordination sites of the Cu2+ ions are occupied by two oxalato groups and two radial cations, respectively. Magnetic susceptibility measurements for 1 and 2 revealed that the copper and radical centers are ferromagnetically coupled with J = +8.2(1) and +7.8(1) cm-1 (H = -2J∑SCu·Srad), respectively.
Formation of Two, One, and Zero-Dimensional Coordination Assemblies from Cd(II) Ion and 4,4′-Bipyridine
Authors: Aoyagi Masaru , Biradha Kumar , Fujita Makoto
Published: September 2002

Complexation of Cd(NO3)2 with 4,4′-bipyridine (4,4′-bpy) gave, depending on the L/M ratios and concentrations, two-dimensional, one-dimensional or zero-dimensional coordination assemblies, which were characterized by X-ray crystallography. The two dimensional structure was shown to be a non-interpenetrated square grid network in which the square cavities were occupied by water and nitrate ions. The one-dimensional polymer also formed a two-dimensional network with the assistance of O-H…N hydrogen bonds. The zero-dimensional structure was composed of two Cd2+ centers, four unidentate 4,4′-bpy, and a bridging bidentate 4,4′-bpy. The networks and the packing of these structures were analyzed in terms of coordination and hydrogen bonds.
Crystal Structure and Thermal Study of the Aqua(butyl)cobaloxime/α-Cyclodextrin Inclusion Complex
Authors: Chen Ying , Luo Lai-bin , Chen Hui-lan , Hu Chun-hua , Chen Jian , Zheng Pei-ju
Published: September 2002

The crystal structure of the aqua(butyl)cobaloxime/α-cyclodextrin inclusion complex was determined by single X-ray diffraction. It crystallizes in the orthorhombic space group P212121 with a = 14.083(3), b = 19.237(4), c = 24.517(5) Å and Z = 4. A thermogravimetric analysis has indicated that the thermal stability of the aqua(butyl) cobaloxime was increased in its α-cyclodextrin inclusion complex.
Assingments of Tri- and Tetrapeptide Sequences in Globular Proteins to the 18 Kinds of Local Structures along Helices and Their Propensities for Specific Local Structures
Authors: Narita Mitsuaki , Mochizuki Akihiko , Ohuchi Shoukichi
Published: September 2002

The genetic information for local structures along helices, encoded in local sequences of protein chains, was statistically investigated for tri- and tetrapeptide sequences (3- and 4-letter words) using the 411 analyzed protein chains. The 18 kinds of local structures adopted by tri- and tetrapeptide sequences were represented 1-dimensionally by using a single helix element and pairs of helix elements in parentheses, respectively. The local sequences have propensities for none to some specific local structures along helices. A local structure (LS)-value is introduced for the evaluation of the normalized preference (NP)-value of a local sequence for a particular local structure. It should be emphasized that N-capping tetrapeptide sequences of helices do not necessarily prevent helix elongation. Local structures adopted by tetrapeptide sequences are plastic, and a particular local structure along helices is determined by the sequence context of helices.
Enzymatic Synthesis of Soluble Polyphenol
Authors: Oguchi Takahisa , Tawaki Shin-ichiro , Uyama Hiroshi , Kobayashi Shiro
Published: September 2002

Enzymatic oxidative polymerization of phenol using peroxidase as catalyst has been carried out in a mixture of alcohol and buffer. Hydrogen peroxide (oxidizing agent) was added dropwise to the reaction mixture. Effects of the reaction parameters have been systematically investigated. The polymer solubility strongly depended on the buffer pH and content, and a polymer soluble in N,N-dimethylformamide (DMF) was obtained in good yields under appropriate reaction conditions. The solvent composition also affected the regioselectivity of the polymer. Purity and amount of the enzyme also affected the polymerization behaviors. By changing the concentration and addition rate of hydrogen peroxide, the molecular weight and solubility of the polymer could be controlled. Some solid properties of the resulting polyphenol were evaluated. From thermal analysis, the polymer was found to possess relatively high thermal stability.
Antibacterial Activity of Arg/Pro-Rich Bactenecin 5 Model Peptides and Their Interaction with Phospholipid Membranes
Authors: Niidome Takuro , Tsuiki Masashi , Tokunaga Yoko , Hatakeyama Tomomitsu , Aoyagi Haruhiko
Published: September 2002

H-Arg-Phe-Arg-Pro-Pro-Ile-Arg-(Arg-Pro-Pro-Phe)n-NH2 (n = 2—5 and 7), models of antibacterial bactenecin 5, were synthesized. The CD measurement showed that they took polyproline II-like conformations in neutral lipid vesicles at 25 and 50 °C, and in acidic ones at 25 °C. However, their conformations changed in acidic lipid vesicles at 50 °C. The membrane perturbation activity of the peptides was also found only for acidic lipid vesicles at 50 °C. The perturbation activity increased with increasing in the peptide chain length. All peptides exhibited negligible hemolytic activity for rabbit erythocytes, whereas they, except for the shortest peptide, had moderate or strong antibacterial activity against Gram-positive and Gram-negative bacteria. Together with the previous results, the N-terminal cationic portion and a certain peptide chain length were found to be important for antibacterial activity.
Structures and Ionization Energies of Some Bis- and Tris(3,4-dimetala-1-butyne-1,4-diyl)s Containing Group 14 Elements as Key Metal Atoms: Tetragermacycloocta-1,5-diyne, Hexasilacyclododeca-1,5,9-triyne, Hexagermacyclododeca-1,5,9-triyne, and Related Compounds
Authors: Nakadaira Yasuhiro , Komoriya Haruhiko , Kakuma Seiji , Kako Masahiro , Mochida Kunio , Yasui Masanori , Iwasaki Fujiko , Shimoda Masakatsu , Matsumoto Fuyuhiko , Yashikawa Masao
Published: September 2002

By X-ray crystallographic analysis, the molecular structure of 3,4,7,8-tetragermacycloocta-1,5-diyne 1b has been established to be planar and quite similar to that of silicon analog 3,4,7,8-tetrasilacycloocta-1,5-diyne 1a. The detailed comparison of structures of cyclic acetylene analogs including a group 14 element shows that ring strain induced by the ethynylene units may be released in a different manner by the carbocycle and by its group 14 metalloid analogs. In contrast to cycloocta-1,5-diynes, structures of the higher homologs, 3,4,7,8,11,12-hexasilacyclododeca-1,5,9-triyne 2a and 3,4,7,8,11,12-hexagermacyclododeca-1,5,9-triyne 2b were determined by X-ray crystallographic analyses to adopt a chair-like conformation. Ionization energies of these 3,4-dimetala-1-butyne-1,4-diyls in condensed phase were obtained by photoelectron spectroscopic methods.
Novel Carbon-Carbon Bond Formation through Mizoroki-Heck Type Reaction of Silanols and Organotin Compounds
Authors: Hirabayashi Kazunori , Ando Jun-ichi , Kawashima Jun , Nishihara Yasushi , Mori Atsunori , Hiyama Tamejiro
Published: September 2002

The reaction of dimethyl(phenyl)silanol with butyl acrylate in the presence of a stoichiometric amount of Pd(OAc)2 or by a combined use of 0.1 molar amount of Pd(OAc)2 and Cu(OAc)2/LiOAc (molar ratio 3/2) gave butyl cinnamate in 76% or 57% yield, respectively. The similar reaction with tributyl(phenyl)tin also proceeded in 77% yield. The organotin compound was shown to react faster than the silanol, although the tin reagent sometimes induced undesirable homo-coupling, while the reaction with silanol did not give such by-product.
Synthesis of Some New Sol-Gel Derived Metal-Organic Compounds and Their Hydrolysis-Condensation Reactions
Authors: Sener Sadiye , Sayilkan Hikmet , Sener Engin
Published: September 2002

This work comprised the following parts: a) hydrolysis of Ti(OEt)4 and Zr(OPr)4 with different amounts of water, b) complexation of the same alkoxides with varying amounts of 2-methylbutanoic and 3-methylbutanoic acids, and c) hydrolysis of complexation products with varying amounts of water.

All reactions were carried out at room temperature. The complex products were [Ti(OEt)3.2(2-MBA)0.8], [Ti(OEt)3.2(3-MBA)0.8], [Zr(OPr)2.5(2-MBA)1.5], and [Zr(OPr)3.3(3-MBA)0.7] (2-MBA: 2-methylbutanoate, 3-MBA: 3-methylbutanoate). The products were characterized by 1H NMR, FT-IR, and elemental analysis. While Ti(OEt)4, [Ti(OEt)3.2(2-MBA)0.8], and [Ti(OEt)3.2(3-MBA)0.8] were hydrolyzed with 1.30, 1.28, and 1.30 mol of water, Zr(OPr)4, [Zr(OPr)2.5(2-MBA)1.5], and [Zr(OPr)3.3(3-MBA)0.7] were hydrolyzed with 2.0, 0.96, and 1.10 mol of water, respectively. These products were characterized by gas chromatography (GC), Karl-Fischer coulometric titrations, and thermal analysis.
Chemoselective Transfer Hydrogenation Reactions over Calcined-Layered Double Hydroxides
Authors: Jyothi Thundi Madathil , Raja Thirumalaiswamy , Talawar Mahadev B , Sreekumar Kurungot , Rajagopal R , Rao Bollapragada S
Published: September 2002

The transfer hydrogenation of aromatics containing various reducible groups has been carried out employing isopropanol as a hydrogen donor in the presence of different calcined LDHs. It was found that the NiII-AlIII (mol ratio 3) catalyst is highly active in bringing about chemoselective reduction compared to other calcined LDHs.