bluuebunny/crossref_metadata_2025 huggingface dataset:
VUV Laser Chemistry—Formation of Hot Molecules and Their Reactions in the Gas Phase—
Authors: Yatsuhashi Tomoyuki , Nakashima Nobuaki
Published: September 2002

The hot molecule (S0**) is in a highly vibrationally excited state formed by rapid internal conversion from initially prepared electronic excited states. The importance and predominance of the S0** mechanism in VUV gas phase photochemistry has been demonstrated. In this account, the fundamental physicochemical properties of S0** are discussed in order to understand the characteristic features of S0** reactions, and VUV laser chemistry is reviewed from the following two points of view: 1) The generalization and classification of VUV chemistry for a variety of molecules, including the hot molecule mechanism and other competitive mechanisms; 2) A new strategy of multiphoton chemistry that employs hot molecule as an intermediate. Internal conversion is a dominant deactivation process for many molecules in the VUV region. Aromatic hydrocarbons and olefins are the representative examples of S0** reactions. However, fluorescence and intersystem crossing are major deactivation processes in some cases such as large condensed aromatic hydrocarbons. The reactions of chlorinated compounds and phenols are explained by other reaction mechanisms such as direct dissociation and predissociation. Carbonyl compounds and some amines are classified into the intermediate cases. Due to the large molar extinction coefficient and relatively long lifetime of S0**, the multiphoton absorption process can be induced by a single nanosecond laser pulse. As a result of fast internal conversion and intramolecular energy redistribution, the second photon and further photons will not be absorbed by the molecule in the electronic excited state but by that in the S0**, and the photon energy of the multiphoton is accumulated as vibrational energy. Therefore, ionization is minor process in the case of the multiphoton reaction of S0**. The neutral radical formation is predominant in the dissociation reaction, and the rate constant increases because the internal energy is multiplied by the multiphoton absorption process. The applications of these findings lie in the following: 1) Large molecules of which the single-photon hot molecule reaction rate is small; 2) Molecules which have been deemed to be photoinert.
Tetrathiapentalene Derivatives with Long Alkyl Chains
Authors: Kimura Shinya , Kurai Hiroyuki , Mori Takehiko , Mori Hatsumi , Tanaka Shoji
Published: September 2002

Bis-fused π-electron donors having alkylthio chains, CnTET-TTP (2-[4,5-bis(alkylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene; n = 2–4) have been synthesized. C2TET-TTP (1a) forms radical-cation salts with BF4- and ClO4-, which are metallic (σrt = 900-2500 S cm-1) down to helium temperatures. The I3 salts of C3TET-TTP (1b) and C4TET-TTP (1c) are semiconductive from room temperature (σrt = 0.041 and 0.025 S cm-1, respectively). (C2TET-TTP)2ClO4 has uniform stacks of the donors, and hats an elliptical Fermi surface characteristic of two-dimensional metals. (C4TET-TTP)I3 is dimeric, and can be regarded as a band insulator. These crystal structures demonstrate the tendency that the long alkyl chains increase the anion content, and stabilize the usual stacking structure as well as the dimerization.
Energy Transfer from Photoexcited Electronic States to the Thermal Modes
Authors: Terazima Masahide
Published: September 2002

Energy transfer processes from a photoexcited ion and molecules to solvents were studied from the rate of the temperature rise of the solvent using several newly developed techniques: temperature grating, temperature lens, acoustic peak delay, and molecular heater–molecular thermometer methods. These energy transfer processes are closely related to the well-studied vibrational relaxation (cooling) process but the overall energy transfer process can be monitored by detecting the time course of the matrix heating. In aqueous solution, most of the energy of a photoexcited ion transfers to the thermal mode within 2–3 ps after the populational relaxation to a lower electronic state. In organic solvents, the process is described by roughly two kinetics: fast ( ≤ 1 ps) and slow (20–30 ps). This two-phase kinetics was explained by a simple thermalization model; the initial fast process represents the energy transfer to the doorway molecules in the first solvent shell molecules and the slower one represents the thermal diffusion process from the hot solvent molecules to the bulk solvent molecules. A new molecular heater-molecular thermometer integrated system is also described.
Enzymatic Polymerization for Precision Polymer Synthesis
Authors: Kobayashi Shiro , Uyama Hiroshi , Ohmae Masashi
Published: September 2002

Our recent advances in enzymatic polymerization, defined as chemical polymer syntheses in vitro (in test tubes) via non-biosynthetic pathways catalyzed by an isolated enzyme, have been mainly reviewed. The major target macromolecules formed via the enzymatic polymerizations described in this article are polysaccharides, polyesters, and polyaromatics. For synthesis of polysaccharides and polyesters, hydrolases are used as catalysts; hydrolases catalyzing a bond-cleavage reaction by water induce the reverse reaction of hydrolysis, leading to polymer production by a bond-forming reaction in vitro. Specific enzyme catalysis provides a novel synthetic route with precise structure control not only for natural biopolymers such as cellulose, xylan, and chitin, but also for unnatural polysaccharides and polyesters, many of which are difficult to be synthesized by conventional methodologies. Oxidoreductases act as catalysts for oxidative polymerization of phenol, aniline, and their derivatives. A new class of phenolic polymers are synthesized without use of toxic formaldehyde under mild reaction conditions. Enzyme-model complexes also catalyze polymerizations for the synthesis of new high-performance polymeric materials.
Dimerization–Carbostannylation of Alkynes Catalyzed by a Palladium–Diimine Complex: Regioselectivity, Stereoselectivity and Mechanism
Authors: Yoshida Hiroto , Shirakawa Eiji , Nakao Yoshiaki , Honda Yuki , Hiyama Tamejiro
Published: September 2002

Double insertion of alkynes into the C–Sn bond of an alkynyl-, alkenyl-, allyl- or arylstannane proceeded in the presence of a palladium–diimine complex to afford highly conjugated alkenylstannanes with exclusive syn selectivity. Perfect regioselectivities were observed in the dimerization–carbostannylation of ethyl propiolate with a palladium–1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene complex, which allowed regio- and stereoselective synthesis of stannyl-substituted muconic acid derivatives. The π-conjugation of the dimerization–carbostannylation products was further extended through a cross-coupling or homocoupling reaction. A palladacyclopentadiene is proposed as an intermediate species.
Evaluation of Novel Local Structural Parameters of Acids and Bases for 1 : 1 Hydrogen-Bond Complexation. II. p-Fluorophenol, 5-Fluoroindole and Various Bases in Carbon Tetrachloride
Authors: Mishima Shozi , Nakajima Tsuyoshi , Tanaka Nobuaki
Published: September 2002

For 1 : 1 hydrogen-bond complexation in CCl4, novel local structural parameters, η° and ω°, representing the nature of the functional group and the residual moiety (supporting group) of acids and bases have been evaluated for two acids and 26 bases. An evaluation of the η° and ω° was carried out by using convergent linear relationships observed among the log K values of the bases against each couple of reference acids. The values of log K experimentally obtained were reproduced from the η°and ω° values within ±0.21 in the log K unit, excluding three exceptions. Family-independent linear relationships were observed between ω°b and the solute hydrogen bond basicity (β2H), and between ω°a and the solute hydrogen bond acidity (α2H) of the bases and acids. Linear relationships could be applied to estimate the ω°a and ω°b values from α2H and β2H values existing in the literature.
Magnetic Field Effects on the Lifetimes of Triplet Biradicals Photogenerated from Zinc(II) Tetraphenylporphyrin-Viologen Chain-Linked Compounds: Dependence on Spacer Chain Length and Environment
Authors: Ito Toshiyuki , Naka Masao , Miura Atsushi , Ujiie Tomomi , Nakamura Hiroshi , Matsuo Taku
Published: September 2002

The effects of magnetic fields on the lifetimes of chain-linked triplet biradicals (3BRs), generated by photoinduced electron transfer from zinc(II) tetraphenylporphyrin (ZnP) to appended viologen (V2+), were investigated in homogeneous solutions of acetonitrile-water and reversed micellar solutions of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) by means of laser flash photolysis. It was found that the decay rate constants (kobs) of the 3BRs increased significantly in the absence of magnetic fields as the number of carbon atoms (n) in the spacer chain between the ZnP and V2+ moieties increased, and then reached a constant value above n = 8. When the magnetic field was increased, the kobs values decreased. A sharp decrease in a low magnetic field was observed, followed by a gradual decrease as the magnetic field was increased, eventually reaching an asymptotic value under the high magnetic field (B > 100 mT) for the compounds with the longer spacer chains. In AOT/2,2,4-trimethylpentane/water reversed micellar solutions, the kobs values were smaller than those in MeCN–H2O homogeneous solutions; this trend became increasingly prominent the longer the spacer chain length. Therefore, the kobs values showed the opposite spacer chain length dependence in comparison with those in homogeneous solutions at B = 470 mT. These results were interpreted in terms of the variation of triplet-singlet energy separation with the interradical distance, Zeeman splitting of the triplet sublevels, electron–nuclear hyperfine coupling, and spin relaxation mechanisms.
Determination of Acidity Constants of Perfluoroalkanoic Acids
Authors: Moroi Yoshikiyo , Yano Hiroaki , Shibata Osamu , Yonemitsu Tadashi
Published: September 2002

Acidity constants (Ka) of perfluoroalkanoic acids were determined by pH titration and by electric conductivity for shorter alkanoic acids (C1 to C5) with 1 to 5 carbon atoms in the alkyl chain. The acidity constants obtained by the two methods are in good agreement. They increase from C1 (ethanoic) to C3 (butanoic acid) and then decrease from C3 to C5 (hexanoic acid) with increasing alkyl chain length. An abrupt decrease in the Ka value for the C5 acid occurred; the attempt to explain this in terms of viscosity of the solutions did not succeeded. The decrease in the Ka values with increasing alkyl chain length was substantiated by the values for C9 (decanoic) to C11 (dodecanoic) acids, which were determined from the solubility change with the solution pH. For the intermediate alkanoic acids (C6 to C8), the Ka values could not be determined precisely by these methods due to the extreme difficulty in separating the colloidal acid particles from the aqueous phase, because the particles have an emulsifying action of their own.
Unique Axial Interaction of a Quadruply-Bonded Cr(II)-Cr(II) with Two Pt(II) Atoms in the Linearly Aligned Pt-Cr-Cr-Pt Supported by Four 6-Diphenylphosphino-2-pyridonate Ligands
Authors: Tanaka Mitsuhiro , Mashima Kazushi , Nishino Masamichi , Takeda Sadamu , Mori Wasuke , Tani Kazuhide , Yamaguchi Kizashi , Nakamura Akira
Published: September 2002

Linearly aligned tetranuclear Pt(II)-Cr(II)-Cr(II)-Pt(II) complexes were prepared using a tridentate pyphos ligand (pyphos = 6-diphenylphosphino-2-pyridonate). The bonding between Cr(II) and Pt(II) was discussed on the basis of magnetic measurements. A dichromium complex, [Cr2(pyphos)4] (1), was prepared by the reaction of [Cr2(OAc)4] with the sodium salt of pyphos ligand. The complex 1 has four phosphorus atoms capable of holding transition metals at both of the axial positions of the Cr2 moiety. Three tetranuclear Pt(II)-Cr(II)-Cr(II)-Pt(II) complexes, i.e., [Cr2Pt2Me4(pyphos)4] (2), [Cr2Pt2Cl4(pyphos)4] (3), and [Cr2Pt2Cl2Me2(pyphos)4] (4), have been prepared by the addition of the respective platinum species, PtIIMe2, PtIICl2, and PtIIMeCl, to the axial positions of the Cr2 moiety of 1. Magnetic measurements of 1-4 together with a crystallographic study for the complexes 1 and 2 revealed that the quadruply-bonded Cr-Cr distance was delicately altered by the nature of the Pt atoms, i.e., the kind of substituents (Cl and/or Me) on the Pt atoms.
Ionization of Pyrene in Nonpolar Hydrocarbon Solvents as Studied by Simultaneous Two-Photon Ionization Spectra
Authors: Ogawa Teiichiro , Murata Daisuke , Soga Hirofumi , Nakashima Keiji
Published: September 2002

Pyrene has two photoconductivity thresholds in the wavelength region of 360–435 nm (two-photon energy: 5.70–6.89 eV) in nonpolar hydrocarbon and tetramethylsilane. The first one is located at 6.04–6.44 eV and the second one at 5.18–6.11 eV. The former was assigned to direct ionization and the latter to an ion-pair formation process. Direct ionization is the major process.
Gas-Phase Studies of Group-11 Cation (Cu+, Ag+, and Au+) Reactions with 2-Propanol in a Supersonic Beam-Expansion Source
Authors: Huang Ya-Chien , Su Po-Hua , Yeh Chen-Sheng
Published: September 2002

The gas-phase reactions of group-11 ions (Cu+,Ag+, and Au+) with 2-propanol were investigated using laser vaporization combined with supersonic beam expansion in a time-of-flight mass spectrometer. A number of reaction pathways, including assoication, dehydrogenation, and dehydration, were observed. Among these metal ions, Au+ is highly reactive toward 2-propanol. The experimental results are parallel to studies by Wilkins et al. using an FT-ICR mass spectrometer (J. Am. Chem. Soc., 107, 7316 (1985)). The geometries and binding energies of all complexes M+–L, where M+ = Cu+, Ag+ , and Au+, L = 2-propanol, acetone, propene, and H2O, were estimated using Møller–Plesset perturbation (MP2) and density functional theory (BLYP). The bond strengths of the complex ions involving gold revealed the strongest bonding, due to a relativistic effect. The energetic relationship between the reactants and the products facilitated an interpretation of the observed exit channels. Because of the supersonic beam source employed, larger clusters containing metal ions were generated as well. Because the cluster sizes with solvent molecules were ≥ 2, the reactivities were apparently limited to Cu+ and Ag+ clusters, while the reactive nature changed in Au+ along with the formation of acetone, lacking in the bare Au+ reactions. For larger clusters, calculations on Ag+–(2-propanol)2 and Ag+–(2-propanol)(acetone) complexes using BLYP were performed to obtain their energetics.
Photodissociation of N2O4 Multilayer Adsorbed on a Polycrystalline Au Substrate
Authors: Senga Takehito , Yabushita Akihiro , Inoue Yoshihiko , Kawasaki Masahiro , Sato Shinri
Published: September 2002

The photodissociation dynamics of N2O4 multilayers adsorbed on a polycrystalline Au substrate at 80–140 K was investigated. The Au substrate was mainly composed of domains with (111) structure. Time-of-flight spectra of the photofragment NO and O as well as infrared reflection absorption spectra for the surface adsorbed species on the Au substrate were measured. Typically, four to five monolayers of N2O4 adsorb on the Au substrate at 85 K were irradiated by the pulsed output of an excimer laser at λ = 193 and 351 nm. Photodissociation of the adlayers at 193 nm takes place by direct photoabsorption of N2O4. Since the top layers of N2O4 absorbed the UV light, superthermal NO and O photofragments are produced. Translationally and internally relaxed fragments are also produced from the photodissociation of the inner layers. At 351 nm, the bulk photoexcitation results in formation of slow NO photofragments. By comparing the effect of dissociation wavelengths, substrate temperatures and dose rates, it is shown that the photodissociation dynamics is governed by both the photoexcitation process and the adsorption state of N2O4 on the Au substrate.
Conformation Preferences of 1,1′-Bis(1-amino-4,4-dicyclopropyl-2,3-diaza-1,3-butadienyl)
Authors: Lam Yulin , Ma Ngai Ling , Liang Eping
Published: September 2002

The reaction of dicyclopropyl ketone with hydrazine sulfate and sodium cyanide afforded 1,1′-bis(1-amino-4,4-dicyclopropyl-2,3-diaza-1,3-butadienyl). The compound exists in the trans conformation in the solid-state and has a trans population of 91.2% in solution. Experimental data are compared with values estimated by ab initio calculations.
Synthesis and X-Ray Structural Study of Magnesium (1,3-Propanediaminetetraacetato)nickelate(II) Octahydrate, Mg[Ni(1,3-pdta)]•H2O. Structural Parameters and Strain Analysis of [M(1,3-pdta)]n− Complexes in Relation to Their Octahedral Distortion
Authors: Radanovic Dusan J , Ama Tomoharu , Kawaguchi Hiroshi , Draskovic Nenad S , Ristanovic Divna M , Janicijevic Svetlana
Published: September 2002

The hexadentate complex Mg[Ni(1,3-pdta)]•H2O (1,3-pdta = 1,3-propanediaminetetraacetate ion) was prepared and its structure established by X-ray crystallography. The complex salt crystallizes in the space group Pnna (# 52) of the orthorhombic crystal system with a = 13.251(2), b = 11.645(2), c = 13.818(3) Å and Z = 4. The Ni(II) ion is surrounded octahedrally by two nitrogen and four oxygen atoms of the ligand. The Mg cation is bonded octahedrally to six water molecules. Both complex ions utilize a two-fold symmetry axis that is present in the crystal. The conformations of the chelate rings were found to be envelope or twist for the glycinates and skew-boat for the six-membered diamine ring. A comparison of structures of hexadentate [M(1,3-pdta)]n− complexes shows an expected variation in their octahedral distortion depending on the central metal ion M. Some spectral characteristics of the complex studied have also been reported.
Europium(III)-N,N′-Ethylenebis(l-amino acid) Complexes as New Chiral NMR Lanthanide Shift Reagents for Unprotected α-Amino Acids in Neutral Aqueous Solution
Authors: Takemura Makoto , Yamato Kazuhiro , Doe Matsumi , Watanabe Masaaki , Miyake Hiroyuki , Kikunaga Toshimitsu , Yanagihara Naohisa , Kojima Yoshitane
Published: September 2002

Three N,N′-ethylenebis(l-amino acid) ligands have been obtained simultaneously with three α,α′-(1,4-piperazinediyl)bis[(S)-alkanoic acid] and four N,N′-ethylenedipeptide products, by reacting a mixture of l-histidine methyl ester and l-aspartic acid dimethyl ester with glyoxal in the presence of sodium cyanotrihydroborate in methanol. Europium(III) complexes with N,N′-ethylenebis(l-amino acid) ligands were useful as chiral NMR shift reagents for some unprotected natural α-amino acids as substrates in neutral aqueous solution, as characterized by large enantiomeric shift differences and unbroadened signal shapes on high-resolution NMR spectroscopy. In addition, the acid-dissociation constants of six bis(amino acid) ligands and the stability constant of the europium(III) complex with N,N′-ethylenedi(l-histidine) were obtained by potentiometric titration.
Effect of Second-Sphere Coordination 9. Partial Inclusion of Pentaammineruthenium(II) and Pentacyanoferrate(II) Complexes with Nitrogen Heterocycles into a Cyclodextrin Cavity
Authors: Ando Isao , Ujimoto Kikujiro , Kurihara Hirondo
Published: September 2002

The inclusion of pentaammineruthenium(II) and pentacyanoferrate(II) complexes with nitrogen heterocycles into cyclodextrins was investigated by UV-visible spectrophotometry, 1H-NMR spectroscopy, and cyclic voltammetry. The stability constants of the inclusion adducts of the metal complexes into cyclodextrins were determined by capillary electrophoresis. The complexes form adducts with cyclodextrins by the inclusion of an aromatic ligand moiety of the complex into the cavity of cyclodextrins. The adduct formation caused a modification of the redox behavior of the complex. The stability of the cyclodextrin adduct was influenced by the included aromatic ligand of the complex and the cavity size of cyclodextrin, especially the positive charge on the aromatic ligand.
Identification of Individual Si-Rich Particles Derived from Kosa Aerosol by the Alkali Elemental Composition
Authors: Kyotani Tomohiro , Koshimizu Satoshi
Published: September 2002

A method of scanning electron microscopy-energy dispersive X-ray microanalysis (SEM-EDX) has been investigated for the identification of individual Si-rich particles derived from Kosa aerosol. The elemental composition of individual Si-rich particles (α-quartz) having SiO2 content over 80% was determined by SEM-EDX using a standardless φ(ρz) correction program, and the results were normalized to 100% on the basis of oxide composition. The distribution of (Na2O+K2O)/SiO2(%) in individual Si-rich particles from real airborne particulate matters showed a sharp and clear seasonal variation. It was found that the distribution was closer to those in the China loess and desert sand in spring time compared to those of the non-Kosa aerosol, the distribution could be successfully used as an effective indicator. The distribution of (MgO+CaO)/SiO2(%) was also used for discrimination from Si-rich particles in some Japanese volcanic rocks such as Andesites. Individual Si-rich particles derived from Kosa aerosol were clearly discriminated from those derived from the Japanese igneous rocks by the proposed method. These results suggest that the alkali elemental composition of individual Si-rich particles is a useful indicator to identify the Kosa particles and to investigate transportation of the Kosa aerosol.
Isolation and Structural Characterization of New Samarium(III) Bromide–HMPA Complexes
Authors: Asakura Katsuo , Imamoto Tsuneo
Published: September 2002

The crystal structures of new samarium(III) bromide–HMPA complexes were accurately determined by single crystal X-ray analysis. The Lewis acidity of samarium(III) cation is discussed based on the crystal structures of several samarium(III)–HMPA complexes.
A Novel Protecting Group for Constructing Combinatorial Peptide Libraries
Authors: Tamiaki Hitoshi , Obata Tomoyuki , Azefu Yasuo , Toma Kazunori
Published: September 2002

3,4,5-Tris(octadecyloxy)benzyl alcohol, HO–Bzl(OC18)3, was prepared from gallic acid and stearyl bromide. Using conventional step-wise elongation, N,C-protected peptides, Fmoc–AAn–...–AA1–OBzl(OC18)3, were synthesized. The substituted benzyl esters were selectively cleaved by a treatment with 4 M hydrogen chloride in ethyl acetate to give Fmoc–AAn–...–AA1–OH and HO–Bzl(OC18)3. Thus, the substituted benzyl group is effective for the protection of C-terminal carboxyl groups in liquid-phase peptide synthesis. Because the substituted benzyl group has a moderately high molecular weight, Fmoc–AAn–...–AA1–OBzl(OC18)3 can be easily purified by size-exclusion chromatography; all protected peptides are eluted in the void fraction of a Sephadex LH-20 gel-filtration column. The combination of the carboxyl-protecting group Bzl(OC18)3 with simple purification by the gel-filtration gives a novel route for constructing combinatorial peptide libraries in the solution phase.
Synthesis of New Diaryl-Substituted Triple-Decker and Tetraaryl-substituted Double-Decker Lanthanum(III) Porphyrins and Their Porphyrin Ring Rotational Speed as Compared with that of Double-Decker Cerium(IV) Porphyrins
Authors: Ikeda Masato , Takeuchi Masayuki , Shinkai Seiji , Tani Fumito , Naruta Yoshinori
Published: September 2002

Tetraaryl-substituted cerium(IV) double-decker porphyrin (2D), tetraaryl-substituted lanthanum(III) double-decker porphyrin (3D), and diaryl-substituted lanthanum(III) triple-decker porphyrins (4T•Me and 4T•MeO) were newly synthesized and their porphyrin ring rotation rates were systematically estimated by means of a VT NMR spectroscopic method. In 2D the coalescence temperature (Tc) for the porphyrin ring rotation was higher than 110 °C, whereas in 3D it appeared at ca. 0 °C. In diaryl-substituted cerium(IV) double-decker porphyrin (5D) it appeared at 13 °C whereas in 4T•Me and 4T•MeO they were lower than −80 °C. These results consistently support the view that the porphyrin ring rotation rates in lanthanum(III)-based porphyrins are much faster than those in cerium(IV)-based porphyrins. The difference is reasonably explained by the difference in the ion size between these two metal ions. Since these sandwich-type porphyrins can act as novel scaffolds for designing positive allosteric recognition systems, La(III) complexes which feature the faster porphyrin ring rotation should be useful to develop more efficient positive allosteric systems.
Reduction of Organic Halides with Tri-2-furylgermane: Stoichiometric and Catalytic Reduction
Authors: Nakamura Tomoaki , Yorimitsu Hideki , Shinokubo Hiroshi , Oshima Koichiro
Published: September 2002

Tri-2-furylgermane proved to be an effective reagent for the radical reduction of organic halides. Treatment of 1-bromododecane with tri-2-furylgermane in THF at 25 °C in the presence of a catalytic amount of triethylborane afforded dodecane almost quantitatively. Radical cyclization of 2-iodoethanal allyl acetal afforded five-membered products under the same reaction conditions. These reactions proceeded with NaBH4 in the presence of a catalytic amount of germanium hydride. The reaction took place in water as well as in THF to give the corresponding reduced compounds in good yields.
The Rate Enhancement Effect of Protodesilylation of Arylsilane Derivatives
Authors: Utimoto Kiitiro , Otake Yasuyuki , Yoshino Hideaki , Kuwahara Eiko , Oshima Koichiro , Matsubara Seijiro
Published: September 2002

Protodesilylation of the aryl moiety in (p-methoxyphenyl)dimethylsilyl and (2,6-dimethoxyphenyl)dimethylsilyl groups proceeds much faster than that in a phenyldimethylsilyl group under acidic conditions; these aryl groups can be substituted with an F atom to give organosilyl fluoride even in the presence of an acid-sensitive group such as an alkenyl group.
Electroreductive Coupling of Aromatic Acyl Bromides to 1,2-Diketones
Authors: Kise Naoki , Ueda Nasuo
Published: September 2002

The direct electroreduction of aromatic acyl bromides gave aromatic 1,2-diketones. The best result was obtained using a Pb cathode in acetonitrile containing Bu4NClO4 as a supporting electrolyte. Aromatic acyl bromides substituted by an electron-donating group afforded 1,2-diketones in moderate-to-good yields, whereas acylated endiols were formed exclusively from aromatic acyl bromides substituted by an electron-withdrawing group.
Effects of the Proton Content of ZSM-5 and the Amount of Pt on the Hydrodesulfurization Activity of Pt/ZSM-5
Authors: Kurosaka Tadahiro , Sugioka Masatoshi , Matsuhashi Hiromi
Published: September 2002

The effects of the proton content of ZSM-5 and the amount of Pt on the hydrodesulfurization (HDS) activity of Pt/ZSM-5 were studied. The extent of proton exchange was shown to affect the reaction selectivity, the formation of aromatics, the cracking of hydrocarbons, and the dispersion of Pt. The HDS activity depended on the surface area of loaded Pt. A catalyst consisting of 5 wt% Pt supported on a 50% cation exchanged ZSM-5 gave a higher HDS activity than other tested catalysts and a small amount of cracking products.
Structural Study of Crystal Transition from Hexagonal to Rectangular Phase of Lignoceric Acid Monolayers
Authors: Kajiyama Tisato , Tominaga Ryota , Kojio Ken , Tanaka Keiji
Published: September 2002

Crystal transition behavior of lignoceric acid (LA) monolayer was structurally investigated by electron diffraction (ED) in conjunction with scanning force microscopy (SFM). LA molecules form two-dimensional hexagonal crystallites right after one spreads a solution at the air/water interface. The hexagonal-rectangular transition of the LA monolayer was attained by two different experimental procedures: monolayer compression under an isothermal condition and monolayer cooling under an isobaric condition. In the compression process, the hexagonal and rectangular phases coexisted in the monolayer at the surface pressure, π, of 10 mN m−1, which was slightly lower than the plateau pressure, and the subphase temperature of 293 K. When the π exceeded the plateau pressure, the hexagonal phase in the LA monolayer was entirely transformed to the rectangular one. High-resolution SFM showed that the crystal transition from the hexagonal to rectangular phase proceeded via a quasi-disordered phase upon compression. A similar hexagonal-rectangular transition was also observed during the monolayer cooling process at the π of 15 mN m−1. Based on SFM observation, we claimed that the molecular ordering or packing state in the rectangular lattice induced by cooling was better than that by the monolayer compression. Finally, the crystal transition mechanisms for these two procedures were proposed.
Characteristic Phase Transition of [C5H5NH]SbBr4 Having a Hypervalent Bond Studied by Single Crystal X-Ray Diffraction and 2H NMR
Authors: Yamada Koji , Tsuda Takuya , Holst Christian , Okuda Tsutomu , Ehrenberg Helmut , Svoboda Ingrid , Krane Hans-Georg , Fuess Hartmut
Published: September 2002

A characteristic second-order phase transition (Ttr = 251 K) of pyridinium tetrabromoantimonate(III) having hypervalent bonds was studied by means of the single-crystal X-ray diffraction and 2H NMR. The SbBr4- anion in [C5H5NH]SbBr4 forms an infinite zigzag chain of irregular SbBr6 octahedra by sharing two edges. This SbBr4- anion has C2 symmetry on the Sb atom perpendicular to the infinite chain. Hence, each octahedron has one symmetric trans Br(2)-Sb-Br(2) bond and two asymmetric trans Br(1)-Sb···Br(2) above Ttr. However, a structural refinement on Phase II at 110 K revealed a characteristic deformation of one symmetric trans Br(2)-Sb-Br(2) bond to an asymmetric one, i.e., one Sb-Br(2) bond becomes shorter by 0.113(2) Å and the other bond located at the trans position becomes longer by 0.129(2) Å. The structural refinement and the 2H NMR on an N-deuterated analog suggest that the N-H···Br hydrogen bond stabilizes the asymmetric trans Br-Sb···Br bond.
Magnetic Field Effects and Spin Dynamics of Radical Reactions in Solution
Authors: Hayashi Hisaharu , Sakaguchi Yoshio , Wakasa Masanobu
Published: September 2002

A pulsed magnet which is useful for the research of chemical reactions has recently been constructed by our group. Here, the world record of the maximum magnetic field (30 T) has been attained in this research area. An optical detected X-band ESR apparatus has also been developed by our group. The world’s best sensitivity and resolution have been realized in this apparatus. In this account, we review our recent results on new magnetic field effects and spin dynamics obtained with such novel methods as described above for radical reactions at room temperature in solution. In Section 1, typical mechanisms of MFEs on radical pairs such as the Δg mechanism and the relaxation mechanism are explained as the introduction of this review. In Section 2, the saturation of MFEs due to the Δg mechanism observed for radical pairs generated from the photoreduction of 4-methoxybenzophenone with benzenethiol in fluid solutions under ultrahigh fields are described. In Section 3, the saturation and reversion of MFEs due to the relaxation mechanism observed for radical pairs generated from the photoreduction of carbonyl and quinone compounds in micellar solutions under ultrahigh fields are reviewed. In Section 4, the first observation of MFEs on the reactions of three-spin systems generated photochemically in solution are introduced. In Section 5, we describe spin dynamics of radical pairs studied with our optically detected ESR apparatus for radical pairs generated from the photoreduction of carbonyl and quinone compounds in micellar solutions.
Monofunctionalized C60 Ions: Their Generation, Stability, and Reactions
Authors: Kitagawa Toshikazu , Takeuchi Ken’ichi
Published: September 2002

Though numerous investigations have appeared on the reduced and oxidized forms of parent C60, investigations on C60 ions that contain exohedral functional group(s) have been rather few. This account deals with the chemistry of such ions, in particular, the chemistry of monofunctionalized species RC60− and RC60+. Studies of the anions RC60− were initiated early in the history of the fullerene chemistry, and they are generally considered appreciably stable carbanions. This account focuses on our recent synthesis of a hydrocarbon salt and ionically dissociable hydrocarbons which contain the C60 framework. These are unusual classes of hydrocarbons that could be obtained by making use of the high thermodynamic stability of a hydrocarbon anion t-BuC60−. Some of the properties which are characteristic of these hydrocarbons are also discussed. In contrast, studies of the chemistry of the cation RC60+ have only recently been launched. In this account, advances in the studies of these cations, including observations of their existence, the evaluation of their stabilities, and the role of these cations as a reactive intermediate, are described.
In Situ Time-Resolved Energy-Dispersive XAFS Study on the Reduction Processes of Cu–ZSM-5 Catalysts
Authors: Yamaguchi Aritomo , Shido Takafumi , Inada Yasuhiro , Kogure Toshihiro , Asakura Kiyotaka , Nomura Masaharu , Iwasawa Yasuhiro
Published: September 2002

The reduction process of Cu–ZSM-5 was investigated by a time-resolved energy-dispersive XAFS (DXAFS) technique. The spectra were recorded every second and the entire spectra were analyzed to elucidate the dynamic change of the local structure around the Cu species. Two Cu–ZSM-5 samples with different Cu loadings were prepared by an ion-exchange method followed by calcination. In the low-loading sample (84% ion-exchanged), Cu2+ cations dispersed isolatedly in the channels of ZSM-5, while in the high-loading sample (104% ion-exchanged) CuO particles were formed. The isolated Cu2+ cations were reduced to isolated Cu2+ cations at 400–450 K and the Cu+ ions were reduced to Cu0 at 550–650 K. The curve fitting analysis of the DXAFS data revealed that Cu4–6 clusters were initially formed in the reduction process. The clusters went out to the outer surface and grew into big particles. On the contrary, the CuO particles on the outer surfaces were reduced directly to Cu0 metallic particles at ca. 450 K. The dynamic structure change around the Cu species in the zeolite during the reduction with H2 was monitored in situ by DXAFS technique for the first time.
Additive Effect of 1-Propanol and 2-Propanol on Molecular Organization of H2O in the Water-Rich Region: Excess Chemical Potential, Partial Molar Enthalpy and Volume of 1-Propanol in 1-Propanol–2-Propanol–H2O at 25 °C
Authors: Hu Jianhua , Chiang Wesley Min-Da , Westh Peter , Chen Daniel Heng Chi , Haynes Charles Allen , Koga Yoshikata
Published: September 2002

Excess chemical potential, μ1PE, partial molar enthalpy, H1PE and volume of 1-propanol, V1PE, were determined as a function of mole fraction of 1-propanol, x1P, in mixed solvents of aqueous 2-propanol with various initial mole fraction of 2-propanol, x2P0. The 1-propanol–1-propanol interaction functions, H1P–1PE ≡ N(∂H1PE/∂n1P), and V1P–1PE ≡ N(∂V1PE/∂n1P), were evaluated by graphical differentiation. The x1P-dependence of all these quantities indicates that 1-propanol and 2-propanol modify the molecular organization of H2O in the same and additive manner in the water-rich region. The additive effect of 1-propanol and that of 2-propanol are in the ratio of (0.07/0.08).
NH3 Dissociative Adsorption on Si(100)-(2×1) Surface: A B3LYP Quantum Chemical Cluster Model Study
Authors: Xu Xin , Kang Song-Yun , Yamabe Tokio
Published: September 2002

Dissociative adsorption of ammonia on the Si(100)-(2×1) surface has been investigated using the hybrid density functional B3LYP method and the Si9H12 one-dimer cluster model of the surface. The adsorption geometries and the reaction energetics from NH3(a) to NH2(a) and H(a) have been studied with Si basis sets varying from the standard all electron 6-31G(d) to the LanL2DZ with effective core potential, while keeping NH3 basis sets as 6-31G(d,p) in all cases. It was found that B3LYP/LanL2DZ is a reasonable level of theory for the calculations of not only the geometries, but also the reaction energetics. This provides a cost-effective way to extend the size of the Si cluster models and to study in details the energetics of the whole reaction path. Based on the experimental and theoretical results available, we recommend an “optimal” bond geometry of NH2(a) and H(a) on the Si(100)-(2×1) surface to be: Si–Si (symmetric dimer) 2.42 Å, Si–N 1.75 Å, Si–H 1.50 Å, N–H 1.01 Å, Si–Si–N 115°, Si-N-H 118°, Si–Si–H 111°, H–N–H 109°. The calculated results on the reaction energetics are in general agreement with the experimental findings as well as the previous theoretical ones.
Dual Photochromic Properties of 4-Dialkylamino-2-hydroxychalcones
Authors: Matsushima Ryoka , Fujimoto Shuichi , Tokumura Kunihiro
Published: September 2002

4-Dialkylamino-2-hydroxychalcones [3-(4-dialkylamino-2-hydroxyphenyl)-1-(substituted phenyl)-2-propen-1-ones] undergo reversible E/Z-photoisomerization in good quantum yields (0.2–0.4) in neutral aprotic solvents. The absorption bands of the photo-Z-isomers are significantly red-shifted from the E-isomers. By addition of acid, the photo-Z-isomers are converted to the flavylium ions with competitive reversion to the E-isomers. In aqueous ethanol solution, photochromic interconversion between chalcones and flavylium ions takes place rather slowly and less extensively.
Selenium Analogs of Tetrathiapentalene Derivatives with Long Alkyl Chains
Authors: Aragaki Masanobu , Kimura Shinya , Katsuhara Mao , Kurai Hiroyuki , Mori Takehiko
Published: September 2002

A novel selenium-containing bis-fused tetrathiafulvalene donor, C2TET-TS-TTP (2-[4,5-bis(ethylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-1,3,4,6-tetrathiapentalene), has been synthesized. The ClO4−, BF4−, and PF6− salts of C2TET-TS-TTP are isostructural, having uniform β-type structures. These salts are essentially metallic down to low temperatures.
Mass-Spectrometric Study on Ion-Molecule Reactions of CH5+, C2H5+, and C3H5+ with C8–C18 1-Olefins in an Ion Trap
Authors: Tanaka Yuki , Tsuji Masaharu
Published: September 2002

Chemical ionization of 1-olefins (CxH2x : x = 8–18) by the CH5+, C2H5+, and C3H5+ ions has been studied under a reactant-ion selective mode of an ion-trap type of GC/MS. In all the reactions, alkyl CyH2y+1+ (y = 3–x) and alkenyl CyH2y−1+ (y = 3–x) ions were observed. For long-chain reagents (x = 11–18), the CyH2y+1+ and CyH2y−1+ distributions peaked at C4 or C5 and C7, respectively, which were essentially independent of the reactant hydrocarbon ions. On the basis of observed distributions and calculated thermochemical data, it was concluded that the major reactions for the formation of CyH2y+1+ were proton transfer to a C=C bond and hydride-ion abstraction from the alkyl portion in the CH5+ reactions, proton transfer to a C=C bond in the C2H5+ reactions, and addition to a C=C bond in the C3H5+ reactions, while the major reactions for the formation of CyH2y−1+ were hydride-ion abstraction in the CH5+ reactions, alkanide-ion abstraction in the C2H5+ reactions, and addition to a C=C bond in the C3H5+ reactions.
Dinuclear Zinc Complexes of Phenol-Based “End-off” Compartmental Ligands: Synthesis, Structures and Phosphatase-Like Activity
Authors: Abe Ko-ji , Izumi Jun , Ohba Masaaki , Yokoyama Takusi , Okawa Hisashi
Published: September 2002

The phenol-based compartmental ligands of the “end-off” type, 2,6-bis{N-[2-(dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL1), 2-{N-[2-(dimethylamino)ethyl]iminomethyl}-6-{N-methyl-N-[2-(dimethylamino)ethyl]aminomethyl}-4-bromophenol (HL2), 2,6-bis{2-[(2-pyridyl)ethyl]iminomethyl}-4-methylphenol (HL3) and 2-[N,N-di(2-pyridylmethyl)aminomethyl]-6-{N-[2-(dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL4), have formed dinuclear zinc complexes: [Zn2(L1)(AcO)2]PF6 (1), [Zn2(L1)(NCS)3] (2), [Zn2(L2)(AcO)2]PF6 (3), [Zn2(L2)(NCS)3] (4), [Zn2(L3)(AcO)2]PF6 (5), [Zn2(L3)(NCS)3] (6), [Zn2(L4)(AcO)2]ClO4 (7), [Zn2(L4)(AcO)(NCS)2] (8) and [Zn2(L4)(NCS)3] (9). The crystal structures of 1, 5•(DMF)0.5(2-PrOH)0.5, 7•CHCl3, 8•(2-PrOH) and 9•3CHCl3 have been determined. Complexes 1 and 5•(DMF)0.5(2-PrOH)0.5 have a di-μ-acetato-μ-phenolato-dizinc(II) core comprised of two square-pyramidal Zn centers. 7•CHCl3 has a similar dinuclear core, but it is comprised of one square-pyramidal Zn and one pseudo-octahedral Zn. 8•(2-PrOH) has a μ-acetato-μ-phenolato-dizinc(II) core with a unidentate thiocyanato-N group on each Zn. 9•3CHCl3 exists in two different crystals: one has a μ-thiocyanato-N-μ-phenolato-dizinc(II) core, whereas the other has a μ-phenolato-dizinc(II) core. The diacetato complexes, 1, 3, 5 and 7, are stable in solution. Hydrolytic activities of the complexes toward tris(p-nitrophenyl) phosphate (TNP) have been studied in aqueous DMF by means of UV-visible spectroscopic and 31P NMR methods. Complexes 1, 3 and 5 have an activity to hydrolyze TNP into bis(p-nitrophenyl) hydrogenphosphate (HBNP) in aqueous DMF. In contrast, 7 showed little hydrolytic activity toward TNP in aqueous DMF.
Assignment of d–d Transitions of Square Planar [CuIIN4] Complexes Containing Imidate and Amine Ligands by Means of Polarized Crystal Spectra.
Authors: Akitsu Takashiro , Komorita Seiko , Urushiyama Akio
Published: September 2002

Square planar [CuN4] copper(II) complexes, Rb2[Cu(succim)4]•2H2O (1), trans-[CuL2(R-chea)(S-chea)] (2), trans-[CuL2(R-chea)2] (3), (succim = succinimidate, L = 5,5-diphenylhydantoinate, and chea = 1-cyclohexylethylamine) were prepared and crystal structures were determined. Crystal data for 1 are monoclinic with space group C2/m; a = 16.279(4), b = 8.382(3), c = 8.297(3) Å; β = 93.13(3) °; V = 1130.4(6) Å3; Z = 2. Crystal data for 2 are monoclinic with space group P21/c; a = 8.485(2), b = 9.7854(8), c = 26.334(4) Å; β = 92.83(1) °; V = 2183.8(5) Å3; Z = 2. Crystal data for 3 are monoclinic with space group P21; a = 8.472(2), b = 9.803(2), c = 26.331(6) Å; β = 92.67(2) °; V = 2184.6(8) Å3; Z = 2. The polarized crystal electronic spectra were determined for square planar [CuN4] 1, 2, and 3 and distorted square planar [CuN4] trans-[CuL2(R-phenea)(S-phenea)] (4) and trans-[CuL2(R-phenea)2][CuL2(S-phenea)2] (5) (phenea = 1-phenylethylamine). These spectra were deconvoluted by Gaussian curve fitting by considering selection rules for electric dipole transitions. The 3d orbital orders were determined to be dx2−y2 > dxy > dz2 > dyz,dzx for 1, dx2−y2 > dxy > dz2 > dyz > dzx for 2 and 3, and dx2−y2 > dxy > dz2 > dyz > dzx for 4 and 5 by means of polarized crystal spectra and angular overlap model (AOM) calculations. Since the dz2 → dx2−y2 transition could be observed separately for 4 for the first time, the present assignment could be established certainly. Distortion of [CuN4] chromophores decreases the peak wave numbers for a series of trans-[Cu(imidate)2(amine)2] complexes. The results of 1, 2, and 3 suggest that lone pairs of imidate ligands destabilize the dxy orbital by distributing in the [CuN4] plane.
Kinetics and Mechanisms of the Axial Ligand Substitution Reaction of the Head-to-head 2-Pyridonato-bridged cis-Diammineplatinum(III) Dinuclear Complex
Authors: Saeki Nami , Hirano Yuji , Sasamoto Yasunari , Sato Ichiro , Toshida Tsuyoshi , Ito Sousei , Nakamura Noriko , Ishihara Koji , Matsumoto Kazuko
Published: September 2002

The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex ([(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(H2O)]4+) with halide ions X− (X− = Cl− and Br−) to give monohalogeno and dihalogeno complexes were studied kinetically:

[(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(H2O)]4++X−  →← [(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(X)]3++H2O,

[(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(X)]3++X−  →← [(X)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(X)]2++H2O.

The acid dissociation constant (Kh1) of the axial aqua ligand in the HH dimer and the formation constants (K1X and K2X) of the monohalogeno and dihalogeno complexes were determined spectrophotometrically to be −log(Kh1/M) = 1.71 ± 0.04; log(K1Cl/M−1) = 5.93 ± 0.02, log(K2Cl/M−1) = 3.71 ± 0.00 for the reaction with Cl−, and log(K1Br/M−1) = 6.20 ± 0.05, log(K2Br/M−1) = 4.55 ± 0.01 for the reaction with Br−. The two platinum atoms are nonequivalent in the HH dimer, in which the first deprotonation occurs selectively to the water molecule on the Pt(N4) atom and the first nucleophilic substitution with X− occurs preferentially to the Pt(N2O2) atom, where the atoms in parentheses are the coordinating atoms. The first water substitution with X− proceeds via two similar substitution paths, whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule, providing a coordinatively unsaturated complex. These reaction paths are reasonably explained by the relative strength of the trans effect of the water, hydroxide, and halide ions in the monohalogeno complexes.
Copper(II) Complexes Resulting from the Oxygenation of (2,9-Dimethyl-1,10-phenanthroline)copper(I) Chloride in the Presence of Dimethylformamide
Authors: Oyaizu Kenichi , Ueno Masayoshi , Li Hong , Tsuchida Eishun
Published: September 2002

The oxygenation of (2,9-dimethyl-1,10-phenanthroline)copper(I) chloride in THF, followed by a treatment with DMF and acidification with HCl, afforded dichloro[2-(dimethylamino)(hydroxy)methyl-9-methyl-1,10-phenanthroline]copper(II) and (aqua)dichloro(2,9-dimethyl-1,10-phenanthroline)copper(II) quantitatively.
Weak Antiferromagnetism in a μ-Alkoxo-μ-Pyrazolato-Bridged Dinuclear Vanadium(IV) Complex
Authors: Mikuriya Masahiro , Minowa Kenichi , Nagao Nobuyuki
Published: September 2002

A vanadium(IV) complex with 2-hydroxy-N,N′-bis(1-methyl-3-hydroxy-3-phenyl-2-propen-1-ylidene)-1,3-propane-diamine (H3L), [(VO)2(L)(pz)] (Hpz = pyrazole), was synthesized and characterized by measurements of the magnetic moment and the electronic spectra. The X-ray crystal structure analysis shows that the compound has a dinuclear structure with two square-pyramidal N2O3 coordination environments, which are bridged by the alkoxo and the pyrazolato groups. The antiferromagnetic interaction between the two metal atoms is fairly weak.
Transformation of Isatin 3-Acylhydrazones under Acetylating Conditions: Synthesis and Structure Elucidation of 1,5′-Disubstituted 3′-Acetylspiro[oxindole-3,2′-[1,3,4]oxadiazolines]
Authors: Somogyi László
Published: September 2002

Several substituted isatin 3-acylhydrazones (e.g. 1a–k, n, p, t) have been synthesized. Under acetylating conditions they were transformed into selectively acetylated derivatives (e.g., 1l, n, o, q–s) and into the novel, title spiroheterocycles (2a–i). Some side reactions occurring under various acetylating conditions are also discussed.
Allosteric Binding of K+ to Crown Ether Macrocycles Appended to a Lanthanum Double Decker System
Authors: Robertson Andrew , Ikeda Masato , Takeuchi Masayuki , Shinkai Seiji
Published: September 2002

A benzocrown-appended lanthanum(III) porphyrin double decker has been synthesized which is capable of binding simple K+ in a cooperative, allosteric fashion to form a 1 : 4 complex. Analysis of this system by means of the Hill equation gave an overall binding constant (Kb) of 1.0 × 1014 (mol dm−3)−4 and a Hill coefficient of 4.0. This same system, however, binds Na+ in a conventional, linear fashion. These results indicate that the novel allosteric binding occurs as the result of 1 : 2 sandwich complexes between K+ and appended crown ether moieties of the two joined porphyrins. The suitability of lanthanum(III) over cerium(IV) for preparing this highly crowded double decker porphyrin is also noted.