bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Sulfide-Bridged Di- or Trinuclear Pyrrolylimido and Diazoalkane Complexes Derived from a Tungsten Dinitrogen Complex
Authors: Seino Hidetake , Mizobe Yasushi , Hidai Masanobu
Published: September 2002

Tungsten pyrrolylimido and diazoalkane complexes, cis,mer-[WCl2(NNC4H4)(PMe2Ph)3] and cis,mer-[WCl2(NN=CRR′)(PMe2Ph)3], which are readily derived from the dinitrogen complex cis-[W(N2)2(PMe2Ph)4], reacted with [PPh4]2[WS4] to give the sulfide-bridged di- or trinuclear pyrrolylimido and diazoalkane complexes, [PPh4][WCl(NNC4H4)(PMe2Ph)2(μ-S)2WS2] (4) and [PPh4][WCl(NN=CRR′)(PMe2Ph)2(μ-S)2WS2] (R = R′ = Me (5a); R = Me, R′ = Ph; R = H, R′ = p-MeC6H4), or [{WCl(NNC4H4)(PMe2Ph)2(μ-S)2}2W] (7) and [{WCl(NN=CMePh)(PMe2Ph)2(μ-S)2}2W]. Treatment of 4 or 5a with tetraalkylthiuram disulfide resulted in the formation of sulfide-dithiocarbamate complexes: [W(NNC4H4)(PMe2Ph)(S2CNR2)(μ-S)2WS(S2CNR2)] (R = Et, Pri (9b)) and [W(NN=CMe2)(PMe2Ph)(S2CNEt2)(μ-S)2WS(S2CNEt2)]. On the other hand, replacement of two PMe2Ph ligands in 4 and 5 by Ph2PCH2CH2PPh2 (dppe) afforded [PPh4][WCl(NNC4H4)(dppe)(μ-S)2WS2] and [PPh4][WCl(NN=CRR′)(dppe)(μ-S)2WS2] (R = R′ = Me; R = Me, R′ = Ph (12b)), where 12b has been shown to react further with [RhCl(cod)]2 (cod = 1,5-cyclooctadiene) to give a bimetallic trinuclear complex [WCl(NN=CMePh)(dppe)(μ-S)2W(μ-S)2Rh(cod)] (13). Detailed structures have been determined by X-ray analyses for 4, 5a, 7, 9b, and 13.
Photoreduction Processes of α-Dodecamolybdophosphate in Aqueous Solutions: Electrical Conductivity, 31P NMR, and Crystallographic Studies
Authors: Ishikawa Eri , Yamase Toshihiro
Published: September 2002

The photoreduction processes of α-[PMo12O40]3- (α-PMo12(0)) in aqueous solutions at pH 2.0 are discussed on the basis of the results of the electrical conductivities and 31P NMR spectra of photolytes, and the crystal structures of α-type two-electron and β-type four-electron reduction species isolated from photolytes as α-[(iPr)2NH2]4[HPMo12O40]·4H2O (1) (α-PMo12(II)) and β-[(iPr)2NH2]3[H4PMo12O40]·2H2O (2) (β-PMo12(IV)) : (i) A one-electron reduction species produced by the photoredox reaction of α-PMo12(0) with methanol is degraded to α-B-[H3PMo9O31(OH)3]3- (α-B-PMo9(0)) and MoV-containing Mo-triad species (Mo3). (ii) The formation of the α-type mono-protonated two-electron reduction species, α-[HPMo12O40]4- (α-PMo12(II)), results from the isomerization of the β-type two-electron reduction species, β-[PMo12O40]5- (β-PMo12(II)), which is produced by coupling between the one-electron reduced α-B-PMo9 (α-B-PMo9(I)) and Mo3. (iii) The β-type four-protonated four-electron reduction species, β-[H4PMo12O40]3- (β-PMo12(IV)) as a final product is produced by the disproportionation of α-PMo12(II). The change in the electrical conductivity of the photolytes during photolysis supports the above processes for the photoreduction of α-[PMo12O40]3- to β-[H4PMo12O40]3- at pH 2.0.
Syntheses, Structures, and Magnetic Properties of Di-μ3-Chloride-Bridged Tripalladium Compounds, [Pd3(μ3-Cl)2(HqnS)6]Cl2 (HqnS = Quinoline–2(1H)–thione) and [Pd3(μ3-Cl)2(Et2dtc)2(PPh3)2]·C6H6(Et2dtc = N, N′–Diethyldithiocarbamate)
Authors: Sugimoto Kunihisa , Kuroda-Sowa Takayoshi , Goto Tamotsu , Maekawa Masahiko , Munakata Megumu
Published: September 2002

Two triangular tripalladium compounds, [Pd3(μ3-Cl)2(HqnS)6]Cl2 (1) (HqnS = quinoline–2(1H)–thione), and [Pd3(μ3-Cl)2(Et2dtc)2(PPh3)2]·C6H6 (2) (Et2dtc = N, N′-diethyldithiocarbamate anion), were prepared. Their single crystal X-ray structure analyses revealed they have a similar trigonal bipyramidal framework of Pd3(μ3-Cl)2 with two chlorine atoms in apical positions. Each Pd atom in all clusters has two additional coordination sites to establish a square planar cis-PdL2(μ3-Cl)2 geometry. In compound 1, six sulfur atoms of six HqnS ligands with thion form are coordinated to the vacant sites of the Pd3(μ3-Cl)2 core. Two coordination sites of one of the three Pd atoms in 2 are occupied by two triphenylphosphines and those of the other two are coordinated by two S atoms of Et2dtc. Although both compounds have 50 valence electrons, only 1 shows paramagnetic behavior. Crystallographic data are as follows. 1: Pd3Cl4S6N6C54H42, triclinic, P1- a = 14.988(5), b = 17.328(3), c = 12.642(1) Å, α = 93.61(1), β = 96.06(2), γ = 71.79(2)°, V = 3099(1) Å3, and Z = 2. 2: Pd3Cl2P2S4N2C52H56, monoclinic, P21, a = 12.278(5), b = 17.426(6), c = 12.630(3) Å, β = 94.65(3)°, V = 2693(2) Å3, and Z = 2.
δMM*-πL Odd Electron Delocalization onto Aromatic Bridging Ligands in a Paramagnetic Dirhodium Complex and Intermolecular π-Stack Interaction in Crystal
Authors: Kawamura Takashi , Kachi Hisanori , Fujii Hiroshi , Kachi-Terajima Chihiro , Kawamura Yuzuru , Kanematsu Naohiro , Ebihara Masahiro , Sugimoto Kunihisa , Kuroda-Sowa Takayoshi , Munakata Megumu
Published: September 2002

The odd electron in the δRhRh* orbital of (3,1)-[Rh2(mhq)4py]+ (1+; Hmhq = 4-methyl-2-quinolinol) was estimated to be delocalized onto each π system of the four mhq bridges to the extent of ca. 9% based on its 1H NMR paramagnetic shifts. The experimental spin distribution in the mhq ligands is consistent with a model of mixing of the π HOMOs of the mhq ligands into the δRhRh* singly occupied molecular orbital (SOMO). In crystals of (3,1)-[Rh2(hq)4py] (2; Hhq = 2-quinolinol) and its cationic radical salts, 2 or 2+ molecules form intermolecular π-stack arrangements of hq ligands. Intermolecular interaction between 2+ molecules in crystal was studied by examining electronic spectra, magnetic susceptibility, ESR, and electrical conductance of its salts.
Analysis of Ion Association Reactions between Monovalent Polycyclic Aromatic Cations and Anions in Aqueous Solution as Studied by Capillary Zone Electrophoresis
Authors: Takayanagi Toshio , Ban Noriaki , Wada Eiko , Oshima Mitsuko , Motomizu Shoji
Published: September 2002

Ion association reactions between monovalent polycyclic aromatic cations and anions have been studied through the mobility change in capillary zone electrophoresis. When the cationic reagent possessing aromatic moieties was used, isomers of aromatic anions were well resolved. Apparent electrophoretic mobility of the anions decreased with an increase in the concentration of the cationic reagent in the migrating solution; the magnitude of the decrease was large when bulkier cations were used. The ion association constants obtained by analyzing the mobility change increased with an increase in the number of aromatic rings of either the pairing cations or the anions. The ion associates formed consist of monovalent cations and anions, and the ion association constant for an ion associate formed between 1-propylbenzo[f]quinolinium ion and pyrene-1-carboxylate ion was in the magnitude of 102.74 dm3 mol-1. Such ion associability was interpreted from the contribution of the stacking of aromatic moieties in an aqueous solution, in addition to the increase in the hydrophobicity.
Low-Temperature Heat Capacities and Ferromagnetic Phase Transition of the Organic Free Radical Ferromagnet, 4-(4-Chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl (CATMP)
Authors: Miyazaki Yuji , Matsumoto Tetsuya , Ishida Takayuki , Nogami Takashi , Sorai Michio
Published: September 2002

Heat capacities of the organic free radical ferromagnet, 4-(4-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl (CATMP) have been measured in the temperature range between 0.1 and 311 K. A ferromagnetic phase transition was observed at 0.28 K and a heat capacity hump was found above the transition temperature. This hump is due to the short-range order characteristic of low-dimensional magnetic spin systems. The enthalpy and entropy gains due to the ferromagnetic phase transition were estimated to be 4.06 J mol-1 and 5.71 J K-1 mol-1, respectively. This entropy agrees well with the theoretical value Rln 2 ( = 5.76 J K-1 mol-1) expected for the magnetic entropy of a spin system with the spin quantum number S = 1/2, where R is the gas constant. The heat capacity hump above the transition temperature is well accounted for in terms of the S = 1/2 two-dimensional ferromagnetic Heisenberg model of square lattice with the intralayer exchange interaction J/kB = 0.42 K, where the spin Hamiltonian H = -2JSi·Sj is adopted and kB stands for the Boltzmann constant. The analysis of the magnetic heat capacities below the transition temperature on the basis of the spin wave theory clarified that the magnetic system settles down in three-dimensional ferromagnetic order below the transition temperature with the interlayer exchange interaction J′/kB = 0.024 K.
Iron(III) Trifluoroacetate as an Efficient Catalyst for Solvolytic and Nonsolvolytic Nucleophilic Ring Opening of Epoxides
Authors: Iranpoor Nasser , Adibi Hadi
Published: September 2002

Iron(III) trifluoroacetate was used as an efficient and nonhygroscopic catalyst for the alcoholysis, hydrolysis, and acetolysis of epoxides. The addition of chloride, bromide, iodide, and nitrate ions to epoxides to produce the corresponding 2-halo and 2-nitratoalkanols and also the conversion of epoxides to acetonides and thiiranes were also performed efficiently in the presence of this catalyst.
Bisoxazoline and Bioxazoline Chiral Ligands Bearing 4-Diphenylmethyl Shielding Substituents. Diels-Alder Reaction of Cyclopentadiene with 3-Acryloyl-2-oxazolidinone Catalyzed by the Aqua Nickel(II) Complex
Authors: Kanemasa Shuji , Adachi Kenji , Yamamoto Hidetoshi , Wada Eiji
Published: September 2002

Enantiopure 2-amino-3,3-diphenyl-1-propanol has been synthesized by the hidantoin route starting from diphenylacetaldehyde, followed by subsequent functional group transformations and optical resolution by a chiral HPLC. This amino alcohol can be converted into two new chiral ligands: 4,4′-bis(diphenylmethyl)-2,2′-bioxazoline and 2,2′-isopropylidenebis(4-diphenylmethyloxazoline), and further to complexes with copper(II) trifluoromethanesulfonate and nickel(II) perchlorate hexahydrate. The nickel(II) aqua complex derived from the bisoxazoline effectively catalyzes the Diels-Alder reactions of cyclopentadiene with 3-acryloyl-2-oxazolidinone in high endo-selectivities and moderate enantioselectivities through a square planar transition structure.
A Convenient One Pot Allylation of Aldehydes with Allylic Halides Prepared in Situ from Allylic Alcohols in the Presence of Metallic Bismuth
Authors: Miyoshi Norikazu , Nishio Mami , Murakami Shunsuke , Fukuma Tomohiro , Wada Makoto
Published: September 2002

A convenient one pot allylation of aldehydes with allylic iodides prepared in situ from allylic alcohols by using trimethylsilyl chloride and sodium iodide proceeds smoothly in the presence of metallic bismuth to afford the corresponding homoallylic alcohols in good yields.
Multi-Layer Macromonocyclic Polyamines. I. Molecular Design and Synthesis of Component Monocyclic Precursors
Authors: Iwata Masaaki
Published: September 2002

We designed ``multi-layer macromonocyclic polyamines'' which might be appropriate polymorphismic molecular scaffolds as host-molecules in ionic or molecular interaction with small or large guest ions or molecules. In polymorphismic molecules, several macromonocyclic polyamines with the same and/or different ring sizes and nitrogen contents are connected to each other by alkylene spacers with various length of the chain. Actual target molecules are characterized by possessing methylene chain arrays of natural polyamines, and we have synthesized from simple starting materials fourteen component macromonocycles with various sizes, 12- to 34-membered rings containing three to eight nitrogen atoms, as essential building blocks required for construction of multi-layer molecules. Our method of synthesis was shown to be very efficient. In a final step, the N-protecting benzyl group was successfully removed by hydrogenation on 10%-Pd/C under 4 kg cm-2 H2 to give the cyclic amine precursors, which could be internal and terminal components in the architecture of the multi-layer molecules. The structures of synthesized compounds were characterized and confirmed by EA, 1H NMR, SIMS, and FAB(+) mass spectrometry.
Synthesis of Optically Pure Bisphosphine Oxides and Related Compounds
Authors: Sugiya Masashi , Nohira Hiroyuki
Published: September 2002

Optically pure bisphosphine oxides were conveniently synthesized by Kolbe electrolytic coupling reaction of carboxylic acids possessing a chiral phosphinoyl group in 60—65% isolated yield. This synthetic approach provides a variety of accesses to P-chiral bisphosphine ligands. Their absolute configurations were intercorrelated with that of the previous reported BisP*-borane. Asymmetric hydrogenation of α-(acylamino)acrylic acids by a rhodium complex with BisP* (R = t-octyl or 1,1,3,3-tetramethylbutyl) affords N-acylamino acids in 94—96% ee.
Reaction of Various Oxiranes and Carbon Dioxide. Synthesis and Aminolysis of Five-Membered Cyclic Carbonates
Authors: Iwasaki Takeshi , Kihara Nobuhiro , Endo Takeshi
Published: September 2002

Various oxiranes reacted with carbon dioxide at 100 °C using lithium bromide as a catalyst under atmospheric pressure to afford the corresponding five-membered cyclic carbonates quantitatively. The rate of the reaction increased as the bulkiness of substituents on the oxirane ring was reduced or an electron-withdrawing group was introduced on the oxirane ring. The stereochemistry of the reaction of oxirane and carbon dioxide was retention without loss of optical purity. When substituted phenylethylene carbonates were reacted with benzylamine, the selectivity to afford secondary alcohol increased as the electron-withdrawing ability of the para-substituent increased.
Acid-Catalyzed Condensation of Azulenes with 9-Anthracenecarbaldehyde and the Synthesis of (9-Anthryl)di(1-azulenyl)methyl and (1-Azulenyl)[10-(1-azulenyl)-9-anthryl]methyl Hexafluorophosphates
Authors: Ito Shunji , Fujita Miwako , Morita Noboru , Asao Toyonobu
Published: September 2002

Acid-catalyzed condensations of 1-methyl and 1,6-di-t-butylazulenes with 9-anthracenecarbaldehyde led us to unexpected 9-(1-azulenyl)-10-[(1-azulenyl)methylidene]-9,10-dihydroanthracenes 10a and 10b as major products, together with (9-anthryl)di(1-azulenyl)methanes 7a and 7b. Hydride abstraction from 7a, 7b, and 10b with DDQ afforded substituted (9-anthryl)di(1-azulenyl)methyl and (1-azulenyl)[10-(1-azulenyl)-9-anthryl]methyl hexafluorophosphates 6a, 6b·PF6- and 11b·PF6-, respectively. Their properties were fully characterized. The reaction of the 3-methyl derivatives 10a, however, did not afford the desired (3-methyl-1-azulenyl)[10-(3-methyl-1-azulenyl)-9-anthryl]methyl hexafluorophosphate (11a·PF6-), due to the low stabilities of 11a. While cations 6a and 6b prepared from 7a and 7b showed high stabilities with large pKR+ values (10.7±0.1 and 12.4±0.1, respectively), cation 11b exhibited relatively low stabilities with the pKR+ value of 5.0±0.1.
Formation, Structure, and Thionation of 1,2,4,5-Tetrathianes [cis- and trans-3,6-Bis(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-1,2,4,5-tetrathianes]
Authors: Ishii Akihiko , Omata Takenori , Umezawa Kazuyo , Nakayama Juzo
Published: September 2002

2,2,4,4-Tetramethyl-1-phenyl-6,7-dithiabicyclo[3.1.1]heptane was treated with 2KHSO5·KHSO4·K2SO4 to yield cis- and trans-3,6-bis(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-1,2,4,5-tetrathianes. The formation mechanism of the tetrathianes is discussed. X-Ray crystallography disclosed that the cis- and trans-isomers take twist and chair conformations, respectively, in the solid state. Variable-temperature 1H NMR spectroscopy in solution showed that the cis-isomer takes a twist conformation exclusively in the temperature range, whereas the trans-isomer exists as an equilibrium mixture of chair and twist conformers. The cis-tetrathiane reacted with Lawesson's reagent at 50 °C to give the corresponding di-2-thianyl disulfide.
Kinetic Studies on the Autoxidation of Cysteine Catalyzed by Copper Complexes : Catecholamines Stimulate the Autoxidation
Authors: Hanaki Akira , Kinoshita Tomoyuki , Ozawa Toshihiko
Published: September 2002

Catecholamines including epinephrine, norepinephrine, dopamine, and dihydroxyphenylalanine accelerated copper-catalyzed oxidation of cysteine under aerobic conditions, while they had no effect under anaerobic conditions. The efficiency of the catecholamines was arranged in the decreasing order as follows; epinephrine ≈ norepinephrine ≥ dopamine > dihydroxyphenylalanine. On the contrary, phenolic amines such as tyramine and tyrosine neither accelerate nor inhibit the autoxidation. The reaction can be elucidated by a ``sequentical mechanism'' which is composed of Eqs. I, II, III, IV, V, and VI :

where L is glycylglycine used as the buffer, and CyS- and Cat- denote cysteinate and catecholamine ions, respectively. The reactions (IV), (V), or both are considered to be rate-determining. The optimum pH for the autoxidation was observed at pH 7.5—7.6, and below pH 7.2 reaction (V) does not participate in the autoxidation system.
The Reaction of Nitrile Oxide-Quinone Cycloadducts. IV. Acid-Catalyzed Dealkylative Aromatization of the 1 : 1 -C=C-Adducts and Base-Induced Rearrangement Products of Aromatic Nitrile Oxides with 2,5- and 2,6-Dialkyl-p-benzoquinones
Authors: Mukawa Takashi , Muraoka Jun , Shiraishi Shinsaku
Published: September 2002

The 1,3-dipolar cycloadducts of aromatic nitrile oxides with 2,5- and 2,6-dialkyl-p-benzoquinones were treated with acetic anhydride/sulfuric acid to give isoxazole-fused hydroquinone diacetates in good yields. The base-induced rearrangement products from some of the 1,3-dipolar cycloadducts were treated with acetic anhydride/sulfuric acid to afford isoxazole-fused catechol diacetates and/or isoxazole-fused hydroquinone diacetates, depending on the slight difference in the substituents of the base-induced rearrangement products. The differences in the products are interpreted in terms of steric hindrance around the carbonyl and hydroxy moieties of the base-induced rearrangement products.
Electrochemical Hydrogenation of Organic Compounds on Poly[N-(5-carboxyhexyl)pyrrole] Film-Coated Electrodes Incorporating Palladium
Authors: Takano Nobuhiro , Seki Chigusa , Shimono Isao , Kobayashi Takanori , Takeuchi Takao
Published: September 2002

Poly[N-(5-carboxyhexyl)pyrrole] coated carbon-fiber electrodes incorporating palladium metal were prepared for the electrocatalytic hydrogenation of methyl α-oxobenzeneacetate, 2-cyclohexen-1-one, and diphenylacetylene in an ethanol-buffer solution. The reactions using these electrodes proceeded smoothly to give hydrogenated products in good yields.
An Efficient Method for the Synthesis of 4,5-Disubstituted Catechols
Authors: Ma Tingli , Kojima Takahiko , Matsuda Yoshihisa
Published: September 2002

4,5-Disubstituted catechols were prepared in high yields via successive Friedel-Crafts acylation in the presence of a Ti(IV) catalyst or I2 and reduction with triethylsilane of veratroles. This method provides an effective and well-regulated synthetic strategy toward catechol derivatives having a variety of substituents at the 4- and 5- positions.
Substituent Effect of 3,3,3-Trifluoropropyl Group on Organic Silanols. Palladium-Mediated Mizoroki-Heck Type and Cross-Coupling Reactions
Authors: Hirabayashi Kazunori , Kondo Tatsuhiro , Toriyama Fumihiko , Nishihara Yasushi , Mori Atsunori
Published: September 2002

The Mizoroki-Heck type reaction of methyl(phenyl)(3,3,3-trifluoropropyl)silanol (1a) with ethyl acrylate in the presence of Pd(OAc)2 (10 mol%) and Cu(OAc)2/LiOAc gave ethyl cinnamate in 70% yield. The palladium-catalyzed cross-coupling of 1a with 4-iodomethoxybenzene in the presence of Ag2O also afforded 4-methoxybiphenyl in 51% yield.
Catalysis of Polymer-Protected Ni/Pd Bimetallic Nano-Clusters for Hydrogenation of Nitrobenzene Derivatives
Authors: Lu Ping , Toshima Naoki
Published: September 2002

Poly(N-vinyl-2-pyrrolidone)-protected Ni/Pd bimetallic colloidal nanoparticles, prepared by the polyol reduction method, have been proved to have a nanometer-sized alloy structure with both metals at zerovalent state by our previous study of TEM, XRD, EXAFS, and XPS analyses. Here, dispersions of these bimetallic nanoclusters with different composition ratios are extensively examined as catalysts for the hydrogenation of various nitrobenzene derivatives: i.e., p-nitrotoluene, p-nitroanisole, 1-nitronaphthalene, p-nitrobenzonitrile, and methyl p-nitrobenzoate, at 30 °C under an atmospheric pressure of hydrogen. These bimetallic nanoclusters exhibit excellent catalytic properties for the reduction of a nitro group to an amino group with high selectivity. The catalytic activity strongly depends on the metal composition of the particles. The maximum catalytic activity can be observed at a certain intermediate composition ratio, being 3—4 times greater than that of a monometallic colloidal Pd catalyst. A bimetallic nanocluster with the mole ratio of Ni : Pd = 1/4 was the most active catalyst for the hydrogenation of para-substituted nitrobenzenes. An approximately linear relationship exists between the hydrogenation rate of the substrate with an electron-donating or electron-withdrawing group and the corresponding Hammett constant of the substituent, as well as between the hydrogenation rate and the LUMO energy level of the substrate.
Characterization of Sulfur on Pt-Alkali metal/Al2O3 Catalysts Treated with H2S by a Temperature-Programmed Reaction Using Deuterium and Its Role in the Dehydrogenation of Isobutane
Authors: Kobayashi Junya , Shimizu Takashi
Published: September 2002

This paper discusses the promotion of isobutane dehydrogenation due to sulfur species adsorbed on Pt-alkali metal (Li, Na, or K)/Al2O3 catalysts. A treatment with hydrogen sulfide at 833 K increased the selectivity to isobutene on all Pt-alkali metal/Al2O3 catalysts. The promotion effect of sulfurization was most significant on a Pt (1 wt%)-Na2O (3 wt%)/Al2O3 catalyst; the selectivity increased from almost 0 for a reduced catalyst to 75% for a sulfurized catalyst. The effect on the selectivity of the addition of alkali metals increased in the order sodium > potassium > lithium. Temperature-programmed reaction (TPR) experiments, conducted by flowing deuterium onto the sulfurized catalysts, were used to characterize the sulfur species that easily desorbed with hydrogen. The results indicated that HS- is the major species on the catalysts and that the adsorbed HS- bridges the PtSir and the Na2Sir particles. Re-reduction of the sulfurized Pt-Na2O/Al2O3 catalyst to remove the HS- decreased the selectivity from 75 to 8%, implying that HS- is effective in enhancing the selectivity.
Preparation of Microporous Silica Gel by Sol-Gel Process in the Presence of Ethylene Glycol Oligomers
Authors: Takahashi Ryoji , Sato Satoshi , Sodesawa Toshiaki , Suzuki Masanori , Ogura Katsuyuki
Published: September 2002

A microporous silica gel was prepared by a sol-gel process in the presence of ethylene glycol (EG) and its oligomers (oligoEG), and the pore formation process was investigated by using NMR and TG-DTA. The micropore volume changed with the polymerization degree of oligoEG, and showed a minimum at the trimer of EG. An attractive interaction between silanol and organic additives plays a key role in micropore formation: the interaction inhibits the bond formation of Si-O-Si during drying and heating, and heterogeneous domains which convert into micropore are formed after the combustion of additives. There are two kinds of interaction: one is ester (Si-OR) bond formation of a silanol with an end hydroxy group of additives; the other is hydrogen bonding between a silanol and an ether oxygen of additives. The former interaction is significant for EG. With increasing length of oligoEG, however, the former interaction rapidly disappears, while the latter becomes stronger. Because of a minimum in the combination of these interactions, the minimal volume of the micropore is observed.
Triangular Platinum(II) Cluster Complexes and Cluster Core Transformation from Square-Planar to Triangular Type
Authors: Yamaguchi Tadashi , Nishimura Nozomu , Shirakura Ken-ichi , Ito Tasuku
Published: September 2002

Reactions of [PtII4(μ-CH3COO)8] (1) with dioximes or with N,N′-dimethylethylenediamine induced a cluster core transformation from a square planar to a triangular type to afford PtII3 clusters.Three of these clusters have been characterized by X-ray analyses. The structure of the PtII3 cluster core is an approximate or regular isosceles triangle, two equidistant edges (2.51—2.56 Å) being somewhat shorter than the other (2.59—2.61 Å).The cluster core transformation proceeds through the substitution of the in-plane acetate ligands in 1 by incoming ligands followed by the removal of one Pt atom from the tetranuclear cluster core.An intermediate of the cluster core transformation, [{Pt4(CH3COO)4(dmgH)2(dmgH2)}2(μ-dmgH2)], was structurally characterized.It is a dimer of tetranuclear Pt(II) complex and consists of a triangular cluster unit and a mononuclear unit with square planar geometry.EHMO study and large 1JPt-Pt values of ca. 8000 Hz suggest the stability of the triangular PtII3 cluster core and the existence of strong Pt-Pt bonds.Ligands in the PtII3 cluster plane are labilized by trans effect of Pt-Pt bonds, although intramolecular hydrogen bonds reduce the lability. On the other hand, out-of-plane acetate ligands are substitution inert.
Electron-Transfer Process in Layered Photoreceptors Containing Azo Compounds
Authors: Shimada Tomoyuki , Sasaki Masaomi , Aruga Tamotsu , Umeda Minoru
Published: September 2002

Photoinduced electron transfer (ET) is the most essential process for carrier photogeneration in organic optoelectronic devices. In azo compound-based layered photoreceptors, carrier photogeneration is sensitized by hole transport material (HTM) incorporation. We investigated this process to elucidate the highly sensitizing mechanism. First, the photoinduced ET efficiency and overall quantum efficiency were measured and compared for the layered photoreceptor and the carrier generation layer. The result that the HTM enhances the photoinduced ET implies that the HTM works catalytically to diminish the activation energy. Although such extrinsic ET takes place independently of an electric field, the subsequent geminate pair dissociation depends on the electric field. Next, the energy-gap dependence of the ET was investigated by employing more than 50 photoreceptors to vary the energy gap over a wide range. The measured efficiency was plotted against the energy gap, in which an inverted region was not observed.
Structure Sensitivity of Platinum Catalysts for Decomposition Reaction of Diluted NO
Authors: Furusawa Takeshi , Aika Ken-ichi
Published: September 2002

Decomposition reactions of diluted (0.1%) NO without reductants were studied over alumina supported platinum catalysts with various platinum loadings. Supported catalysts with different dispersions of platinum particle (different particle sizes) were prepared by controlling platinum loading on alumina. The XRD measurements disclosed that the relative peak intensity of (111) layer increased with an increase in the particle size, suggesting that the XRD peak intensity was closely related to the surface structure of platinum particles. The activities (TOF) of NO decomposition increased with an increase in the particle size or the peak intensity of (111) structure. Temperature programmed desorption (TPD) of oxygen was also studied on these samples. The temperature of oxygen desorption decreased with an increase in the particle size or the ratio of (111) structure. The NO decomposition was reasonably explained, as it preceded more easily on the (111) surface where oxygen was weakly adsorbed on platinum. It was also pointed out that the surface structure was more sensitive for oxygen adsorption than the NO decomposition reaction.
Vibrational Relaxation of Chemically Excited SiO (ν = 1—5) Produced in the Reaction of Silane with O(1D)
Authors: Takahara Atsuko , Tezaki Atsumu , Matsui Hiroyuki
Published: September 2002

The state-resolved vibrational relaxation process of SiO was monitored in the excimer laser photolysis of N2O/SiH4/He mixtures, where vibrationally hot SiO (Tv = 5200 K) was produced by the reaction of SiH4+ O(1D). A frequency-doubled optical parametric oscillator was used as a widely tunable source to probe SiO (v = 0—7) by the laser-induced fluorescence technique. From an analysis of the observed relaxation profiles, the vibrational transition rate constants in collisions with He and N2O were evaluated against the vibrational level v = 1—5 of SiO. Previous theories for the V-T and V-V energy transfer were compared with the present experimental results.
Influence of the Naphthalene Derivative on the Luminescence Properties of CdS Particles Prepared by the Sol-Gel Method
Authors: Fujii Tsuneo , Tanaka Nobuaki , Tai Hideyuki , Obara Shiro , Ellis Arthur B
Published: September 2002

Adsorption from an ethanol solution of naphthalene (N) derivatives onto the surface of CdS particles encapsulated into silica glasses prepared by the sol-gel method quenches or enhances the yellow-green and red photoluminescence (PL) intensity of the semiconductor particle relative to its value in pure ethanol solvent. The enhancement is in the order 1,4-dimethyl-N > 1-chloro-N ≥ N ≥ 1-fluoro-N ≥ 1-methyl-N ≥ 1-bromo-N and quenching is in the order 1-nitro-N >2-carboxy-N. This order is understandable based on the electron-donating or electron-accepting abilities of the individual naphthalene derivatives. The changes in the PL intensity depend on the concentration and give good fits to the Langmuir adsorption isotherm model, yielding equilibrium constants for adduct formation on the order of ca. 103 M-1.
Magneto-Structural Correlations in Phenoxo-Bridged Metal(II) Compounds. Magnetic Properties of (R4N)2[Co2Cl4(4-XC6H4O)2] (X = H, CH3; R = CH3, C2H5)
Authors: Emori Shuji , Nakashima Michio , Mori Wasuke
Published: September 2002

Dinuclear compounds (R4N)2[Co2Cl4(4-XC6H4O)2] (X = H, CH3; R = CH3, C2H5) were prepared, and their temperature-variable magnetic susceptibilities were determined to evaluate the exchange-coupling strength's between the cobalt(II) ions. The coupling strength of (Et4N)2[Co2Cl4(4-CH3C6H4O)2] was considered in terms of its structural parameters and the electronic effects of the methyl substituent. Such magneto-structural correlations, together with those for copper(II), nickel(II), and iron(II) systems, confirm that the exchange couplings in phenoxo-bridged metal(II) compounds are affected concurrently by the s/p character of the hybrid orbitals on the bridging oxygen atom, by the electronic effects of the substituents on the aromatic ring, by the ionic radius and acidity of the metal(II) ion, as well as by the number of unpaired electrons and d character of the hybrid orbitals on the metal(II) ion.
Conversion of Methane to Methanol on Diiron and Dicopper Enzyme Models of Methane Monooxygenase: A Theoretical Study on a Concerted Reaction Pathway
Authors: Yoshizawa Kazunari , Suzuki Akiya , Shiota Yoshihito , Yamabe Tokio
Published: September 2002

We present theoretical analyses for the conversion of methane to methanol on a diiron model of soluble methane monooxygenase (sMMO) and on dicopper models of particulate methane monooxygenase (pMMO) using the hybrid density-functional-theory B3LYP method. Methane is proposed to be reasonably converted into methanol in a two-step concerted manner on the dinuclear enzyme models. The first step in our proposal is concerted H atom abstraction of methane via a four-centered transition state (TS1) and the second step is concerted methyl migration via a three-centered transition state (TS2). The general features of the electronic process are identical to those of the gas-phase process for the methane-methanol conversion by the bare FeO+ complex. The concerted H atom abstraction and the direct H atom abstraction via a transition state with a linear C-H-O(Fe) array are compared using the dinuclear models. The transition state for the direct H atom abstraction (TSd) on the diiron model is found in the spin undecet state; however, that on the dicopper models is found in the doublet state. Kinetic isotope effects (kH/kD) are calculated and analyzed for the concerted and the direct H atom abstraction mechanisms using the transition state theory. Calculated kH/kD values for the concerted process and the direct process are 9 and 14, respectively, at 300 K.
Phase Separation Behavior of (Palmitic Acid/Lignoceric Acid) Mixed Monolayer Based on a π-A Isotherm Measurement and a Scanning Probe Microscopic Observation
Authors: Kuramori Miyuki , Uchida Naoko , Suehiro Kazuaki , Oishi Yushi
Published: September 2002

The aggregation state of a mixed monolayer of palmitic acid (C16) and lignoceric acid (C24) was investigated on the basis of a π-A isotherm measurement and a scanning probe microscopic observation. The independence of the plateau and collapse pressures on the monolayer composition and the additivity of the average molecular area exhibited that the C16 and C24 molecules were immiscible in the monolayer, indirectly suggesting the presence of phase-separated domains in the system. Two kinds of regions with different heights were apparently observed on an atomic force microscope image of the mixed monolayers. The change in the area fraction with the composition, the film thickness and the difference in the lateral force of the two regions revealed that the (C16/C24) mixed monolayer was in a phase-separated state. This phase separation is probably due to an enthalpic contribution based on the difference in cohesive energy of each alkyl chain.
Temperature-Induced Phase Transitions in 1,3,5-Trimethylbenzene Crystal
Authors: Yamazaki Michiko , Tanaka Makiko , Inoue Tohru , Suzuki Yoshio , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi
Published: September 2002

The temperature effect on the Raman-active inter- and intramolecular vibrations of 1,3,5-trimethylbenzene crystal was studied. The spectral structure due to the intermolecular vibrations changed as the temperature was varied and the vibrational frequencies shifted discontinuously at about 95 and 195 K when the temperature rose from 77 K. For the intramolecular vibrations, a discontinuous shift of the vibrational frequencies of the ν1 and ν12 modes was observed at about 95 K. Thermograms obtained with a differential scanning calorimetry for the crystal show two endothermic peaks at 91 and 188 K as well as three endothermic peaks at 220, 222, and 227 K around the melting point. These observations indicate that the first-order phase transitions take place at 91 and 188 K under 1 atm in a 1,3,5-trimethylbenzene crystal, and that the crystal has three different crystal structures around the melting point between 220 and 227 K.
Intermolecular Interactions in Crystal Structures of Isomeric Mesogens with Two Ester Linkages
Authors: Tamura Kyoko , Hori Kayako
Published: September 2002

In order to make clear the influence of more than one polar group on packing modes of molecules and hence on liquid crystalline behavior, crystal structures have been determined for five mesogens with a general formula, CnH2n+1O-C6H4-X-C6H4-Y-C6H4-OCmH2m+1: I (n = m = 8, X = COO, Y = OCO), II (n = m = 8, X = OCO, Y = COO), VI (n = 8, m = 1, X = COO, Y = OCO), V (n = 8, m = 1, X = OCO, Y = COO), and VI (n = 8, m = 1, X = OCO, Y = OCO). Two symmetrical molecules I and II, in which the dipole moments cancel, have quite different crystal packings. Compounds II and V with the same core (the moiety except for chains) have similar packing modes in spite of different chain lengths. These facts are interpreted in terms of two factors: overlappings of planar moieties in cores, formed by the conjugation of a benzene ring with the attached ester linkage(s), and dipole-dipole interaction of polar groups. The crystal structures are closely related to the liquid crystalline phase sequences: imbricated structures (half-and-half overlapping of molecules) to the nematic character and smectic-like layer structures with the smectic one.
Behaviors of the One-Electron Reduction Species of {RuNO}6-Type Complexes. An Oxygen-Transfer Reaction Occurs in the Nitrosyl Site of cis-[Ru(NO·)X(bpy)2]n+ (X = ONO2 for n = 1, X = CH3CN, H2O for n = 2) ({RuNO}7-Type) to Give an Identical Nitro Species
Authors: Mukaida Masao , Sato Yoshinobu , Kato Hideji , Mori Mami , Ooyama Dai , Nagao Hirotaka , Howell F Scott
Published: September 2002

Degradation sequences of cis-[Ru(NO·)X(bpy)2]n+ (X = ONO2, OCHO, OCOMe, NO2, Cl for n = 1; X = CH3CN, H2O for n = 2) ({RuNO}7-type), a one-electron reduction species of {RuNO}6-type complexes, were investigated in CH3CN by monitoring using electrochemical techniques (both cyclic and hydrodynamic voltammetries). The results show that an oxygen transfer occurs effectively at the nitrosyl site of cis-[Ru(NO·)X(bpy)2]n+ (X = ONO2 for n = 1, X = CH3CN, H2O for n = 2) to give identical nitro species, cis-[Ru(NO2)(CH3CN)(bpy)2]+. The extent that the nitrosyl-to-nitro conversion proceeded, however, differs depending on the X ligands; X = CH3CN and H2O complexes gave the nitro species in almost 40% yield, while X = ONO2 complex afforded nearly 80%. The monitoring results of the degradation sequences, along with the differences in yields, suggest that different processes are operating separately in the oxygen-transfer reaction. We propose some possible processes for both reactions, although a further investigation is needed for a detailed explanation.
An Analysis of S-T0 Mixing Polarization of CIDEP in Terms of the Lennard-Jones Fluids: 1-Hydroxy-1-methylethyl Radical in 2-Propanol
Authors: Kitahama Yasutaka , Kimura Yoshifumi , Hirota Noboru
Published: September 2002

Calculations of the magnitudes of the polarization (PRPM) due to singlet-triplet (S-T0) mixing of the radical pair mechanism of chemically induced dynamic electron polarization (CIDEP) are made by numerically solving the stochastic Liouville equations for fluids in which intermolecular interactions are represented by the Lennard-Jones (LJ) potentials. PRPM and the relation between PRPM and the difference in the resonance frequencies of radicals of the pair (2Qab) are examined for the continuum and for various models with different relative strengths of solute-solute, solute-solvent, and solvent-solvent interactions.In the continuum, PRPM reaches the maximum value at small |J0| (J0 is the exchange interaction at a distance of the closest approach),and levels off at large |J0|, whereas in the LJ fluids it increases in the region of large |J0| and reaches a second maximum.At low temperatures, m, which is defined as the exponent in the form of PRPM ∝ Qabm, approaches 0 in the LJ fluids in the region of |J0| = 1011—1012 s-1.The calculated results are compared with the experimental results obtained for 1-hydroxy-1-methylethyl radicals in 2-propanol.The main features of the experimental observations are qualitatively better explained by the present models of the LJ fluids than by the continuum with |J0| = 1011—1012 s-1.These results are ascribed to the effect of the solvent structure which tends to keep the solvent-separated radical pair for a longer time.
Interactions of β- and γ-Cyclodextrins with Thionine and 2-Naphthalenesulfonate in Aqueous Solution
Authors: Hamai Sanyo
Published: September 2002

In aqueous solutions, a cationic dye, thionine (Th), has been found to form a 1 : 1 complex with 2-naphthalenesulfonate (2NS), which is an organic anion. An equilibrium constant for the formation of the complex has been evaluated to be 310 ± 20 mol-1 dm3 from the absorbance change of Th.The Th fluorescence is quenched by the formation of the complex. β-Cyclodextrin (β-CD) and γ-CD form a 1 : 1 and a 1 : 2 host-guest inclusion complex with Th, respectively.Equilibrium constants for the formation of the 1 : 1 β-CD-Th and 1 : 2 γ-CD-Th inclusion complexes have been evaluated to be 300 ± 20 mol-1 dm3 and 1.07 × 107 mol-2 dm6, respectively.The addition of γ-CD to a Th solution containing 2NS results in the formation of a 1 : 1 : 1 γ-CD-Th-2NS inclusion complex. From a simulation concerning the absorbance change, the equilibrium constant for the formation of the ternary 1 : 1 : 1 inclusion complex has been estimated to be 22600 mol-1 dm3, which is nearly the same as that (21500 mol-1 dm3) estimated from a simulation concerning the fluorescence intensity change.
Effect of High Magnetic Field on Copper Deposition from an Aqueous Solution
Authors: Tanimoto Yoshifumi , Yano Hiroshi , Watanabe Sin-ichi , Katsuki Akio , Duan Wenyong , Fujiwara Masao
Published: September 2002

Deposition of copper metal from a Cu2+/Zn liquid-solid redox reaction is studied in a high magnetic field gradient. A zinc wire is placed on a chromatography paper strip with a copper(II) chloride aqueous solution. At zero field, copper dendrite grows uniformly around the wire. In the presence of a magnetic field gradient (ca. 410 T2 m-1), the dendritic pattern changes drastically. The yields of copper dendrite and consumed copper ion increase by ca. 50% in the magnetic field. The results are interpreted in terms of the magnetic force-induced convection of the solution.
Cage Dynamics in the Third-Order Off-Resonant Response of Liquid Molecules: A Theoretical Realization
Authors: Okumura Ko , Bagchi Biman , Tanimura Yoshitaka
Published: September 2002

It is generally believed that the ultrafast initial spectroscopic response from the molecules in the condensed phase originates from small amplitude inertial motions within the cage formed by the nearest-neighbor solvent molecules surrounding the probe, or the cage effect. However, no quantitative estimate of this dynamics has been available for the currently popular experiments which measure the third-order off-resonant response. In this work, we fill this gap by a microscopic approach and demonstrate that the cage dynamics alone can produce the initial rise in the subpicosecond (ca. 200 fs) range in the third-order response. A simple analytical expression for the initial Gaussian time constant relevant to various kinds of the third-order off-resonant experiments is presented, which is found to be rather strongly dependent on the temperature. Connection with the non-polar solvation dynamics is also discussed.
Calorimetric and Magnetic Studies on a Ferromagnetic Phase Transition of the Metal-Assembled Complex MnCu(obbz)·H2O
Authors: Asano Kaori , Miyazaki Yuji , Mori Wasuke , Nakatani Keitaro , Kahn Olivier , Sorai Michio
Published: September 2002

Heat capacities of the metal-assembled ferromagnet MnCu(obbz)·H2O (obbz = oxamidobis(benzoato)) have been measured in the temperature region between 0.1 and 301 K by adiabatic calorimetry. A broad phase transition due to the three-dimensional ferromagnetic ordering was observed around 17 K. Above the transition temperature, a heat capacity tail arising from the short-range order characteristic of a low-dimensional magnet was found. The enthalpy and entropy gained by the phase transition are 227 J mol-1 and 12.7 J K-1 mol-1, respectively. This entropy acquisition is very close to the value Rln 5 ( = 13.4 J K-1 mol-1) expected for the spin manifold of the spin quantum number S = 2 ground state, where R stands for the gas constant. The thermal anomaly above the transition temperature can be accounted for in terms of the S = 2 two-dimensional ferromagnetic Heisenberg model rather than the one- or three-dimensional models. This suggests that this complex can be regarded as a two-dimensional ferrimagnet, in which strong antiferromagnetic interaction exists between a pair of Mn(II) (S = 5/2) and Cu(II) (S = 1/2) but the magnetic coupling between the pairs is very weak. Magnetic measurements for the complex revealed a bend of the hysteresis loop above the transition temperature and a magnetic relaxation below the transition temperature. These results lead to the conclusion that the broadness of the phase transition may be attributed to superparamagnetism caused by the fact that the present complex is prepared only in a fine powder.
Simultaneous Multielement Determination of Hydride- and Oxoanion-Forming Elements in Seawater by Inductively Coupled Plasma Mass Spectrometry after Lanthanum Coprecipitation
Authors: Yabutani Tomoki , Ji Shan , Mouri Fumihiko , Itoh Akihide , Chiba Koichi , Haraguchi Hiroki
Published: September 2002

The simultaneous multielement determination of trace elements in seawater, especially hydride- and oxoanion-forming elements, has been investigated by inductively coupled plasma mass spectrometry with the aid of lanthanum coprecipitation preconcentration. The optimum pH in lanthanum coprecipitation was pH 9.5; at this value, trace elements were well recovered and major constituents of seawater such as Na, Mg, K, and Ca were significantly reduced in the concentrated solutions. The recovery values obtained for V, Cr(III), Mn, As(III), As(V), Se(IV), Y, Sn, Sb(III), Sb(V), W, Bi, and U were more than 85% after lanthanum coprecipitation, while Cr(VI), Se(VI), and Mo(VI) provided poor recoveries of less than 30%. The reproducibility for coprecipitation was within 5% as relative standard deviation. The present method was applied to the determination of trace elements in coastal seawater reference material CASS-3. The analytical values for Mn, As, V, Y, Sb, W, and U were in fairly good agreement with the certified or literature values.
Preparations and Characterizations of Novel N, N′-Ethylene-Bridged-(S)-Histidyl-(S)-Tyrosine Derivatives and Their Copper(II) Complexes as Models of Galactose Oxidase
Authors: Yamato Kazuhiro , Inada Takanori , Doe Matsumi , Ichimura Akio , Takui Takeji , Kojima Yoshitane , Kikunaga Toshimitsu , Nakamura Shin , Yanagihara Naohisa , Onaka Tomoko , Yano Shigenobu
Published: September 2002

Structurally constrained ethyl (2S)-3-(4-hydroxyphenyl)-2-{[(3S)-3-(imidazole-4-yl)-methyl]-2-oxo-piperazine-1-yl}propionate (N,N′-ethylene-bridged-(S)-histidyl-(S)-tyrosine ethyl ester, eHY-OEt) was obtained by a one-pot reaction from (S)-histidine methyl ester and (S)-tyrosine ethyl ester with glyoxal. Four ligands, (Boc-Gly-eHY-OEt (HL1), Boc-Gly-eHY-NH2 (HL2), Ac-eHY-OEt (HL3), and Ac-eHY-NH2 (HL4), where Boc-Gly is t-butyloxycarbonyl-glycyl and Ac is acetyl) were derived from eHY-OEt. Also, corresponding copper(II) complexes, in which only amino acid side chains coordinate to the copper(II) ion, [Cu(L1-)2(H2O)] 1, [Cu(L2-)2(H2O)] 2, [Cu(L3-)2(H2O)] 3, and [Cu(L4-)2(H2O)] 4, were prepared and characterized by elemental analyses and the FAB-MS spectra. The conformational behaviors were confirmed by the 1H NMR spectra. UV-visible-NIR, CD and ESR spectra showed that copper(II) complexes are mononuclear square-pyramidal structures in both the solid and solution states. Cyclic voltammetry of HL1 and 1 showed irreversible ligand oxidation. The acid-dissociation constants of HL4 were obtained as 6.38 (pKa1) and 9.67 (pKa2) by potentiometric titration, and the complex formation constants of 4 were obtained as 7.16 (log K1) and 3.71 (log K2). Furthermore, thermogravimetric analyses (TGA) and differential thermal analyses (DTA) of 1 and 2 were measured.