bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphorescence Emission of 2,6-Diacetylpyridine: Role of N-Heteroatom and Effect of Hydrogen-Bonding
Authors: Sarkar S K , Ganguly T 
Published: July 2006

Abstract
The absorption, excitation, and luminescence spectra of 2,6-diacetylpyridine (DAP) and acetophenone (ACP) are investigated in nonpolar methylcyclohexane (MCH) and polar ethanol (EtOH) matrices at 300 K and 77 K. The emitting state of DAP is found to be the lowest triplet state of essentially nπ* nature. In the emitting lowest triplet nπ* states of DAP and ACP the carbonyl group is observed to be the chromophore. The comparative studies on the photophysical properties of DAP and ACP reveal that the introduction of a pyridinic nitrogen atom in the phenyl nucleus of ACP leads to large nonradiative transitions from the lowest 3noπ* due to vibronic interaction between this state and the pyridinic nNπ* state. In the case of ACP a weak ππ* fluorescence, in addition to phosphorescence is observed in EtOH glass matrix at 77 K. On the other hand in EtOH no such fluorescence is detected for DAP. The phosphorescence decay profile of DAP in presence of EtOH is found to be of single exponential indicating emission from a particular excited electronic state. It is suggested that due to comparatively much weaker hydrogen-bonding interaction between DAP molecule and EtOH solvent both intersystem crossing and internal conversion rates are little affected.
Heterogeneous Photocatalysis. VIII. Zinc Sulfide Catalyzed Hydrogen Formation from Water in the Presence of Sodium Formate
Authors: Kisch Horst , Bücheler Joachim 
Published: July 2006

Abstract
A suspension of n-ZnS in aqueous sodium formate photocatalyzes formation of hydrogen (72%) and carbon monoxide (27%). The stoichiometry of the hydrogen producing reaction is determined as HCO2Na+H2O=H2+HCO3Na. The quantum yield at 290 nm is 0.24 mol H2/Einstein and its wavelength-dependence parallels that of the anodic photocurrent measured photoelectrochemically. Reaction rates increase linearly with increasing light-intensity and do not change when the temperature is increased up to 70°C. No gaseous products are formed when nonaqueous formic acid is employed instead of formate, or when ZnS is dehydrated at 250°C before use or when CdS is substituted for ZnS. When THF or sulfur compounds are added to the solution, H2 is the only gaseous product. The dependence of the reaction rate on formate concentration points to a Langmuir-type adsorption of formate onto the semiconductor surface, Kads=26 M−1. In D2O/HCO2Na the initial rate does not change but the amount of CO increases to 60% and photocorrosion is much stronger than in H2O; the initial isotopic composition of 85, 10, and 5% changes to 63, 30, and 7% of D2, HD, and H2, respectively, when 400 mL of gas has been produced. In H2O/DCO2Na the rate decreases by a factor of 1.3 and the amount of CO is only 15%; only H2 but no D2 and HD are detectable. The hole scavenger KSCN does not influence the quantum yield of hydrogen formation while the electron scavenger NaNO3 induces a strong decrease and completely inhibits CO formation. Stern–Volmer analysis indicates that nitrate scavenges in addition to conduction band electrons also an intermediate CO2− radical. The latter has been identified by spin-trapping experiments.
N-Chlorosuccinimide-Promoted Oxidative Decarboxylation of α-Amino Acids in Aqueous Alkaline Medium
Authors: Ramachandran M S , Easwaramoorthy D , Rajasingh V , Vivekanandam T S 
Published: July 2006

Abstract
Kinetics of oxidation of twelve α-amino acids (AA) by N-chlorosuccinimide (NClS) in aqueous alkaline media have been studied and compared with those of N-bromosuccinimide (NBS) oxidation. Analysis of the results shows that the observed rate of oxidation is first-order in [oxidant] and zero-order in [substrate]. The rate of oxidation increases with increase in [OH−]free in [NClS], the exception being the amino acids having β-alkyl substituent such as valine, leucine etc. Perusal of the results shows that NC1S/NBS reacts with α-amino acid anion to produce α-amino acyl hypohalite which then decomposes in the rate-determining step to give the products. The intermediate α-amino acyl hypohalite is identified by UV-visible absorption spectra. Glycine behaves differently from other amino acids in both oxidants. The proposed mechanism is consistent with the observed kinetics.
Carbon-13 NMR Study of Naphthylmethanide Ions in Polar Solvents
Authors: Yokoyama Yukihiro , Takahashi Kensuke 
Published: July 2006

Abstract
The 13C NMR parameters for 1- and 2-naphthylmethanide ions were obtained in two polar solvents, THF and HMPA. Excess charge distributions in the ions are discussed in connection with the nature of the solvents.
An Improved Cyanoalkylation Method of Aldehydes Catalyzed by Electrogenerated Base in a DMF–H2O System
Authors: Torii Sigeru , Kawafuchi Hiroyuki , Inokuchi Tsutomu 
Published: July 2006

Abstract
Electrogenerated base (EG base) formed in a DMF–H2O (1.85 M)–Et4NOTs (0.1–0.2 M)–(Pt) system is effective for condensation of phenylacetonitrile and its related compounds with aldehydes, giving the corresponding cyanoalkylation compounds in good yields, and the concomitant dehydration of the adducts is minimized.
Preparation of 2-Oxabicyclo[2.2.2]oct-5-ene, 1,4-Dimethyl-2-oxabicyclo[2.2.2]oct-5-ene, and 6-Oxabicyclo[3.2.1]oct-3-ene
Authors: Inouye Yoshinobu , Tokuhisa Kenji , Mitsuya Morihiro , Kakisawa Hiroshi 
Published: July 2006

Abstract
Three bicyclic olefins having an allylic oxygen atom (see title) were prepared. Of those, 2-oxabicyclo[2.2.2]oct-5-ene could not be isolated in its pure state due to the volatility of the compound. The other two, however, could be isolated.
A Conductance Study of Zinc Halides and Perchlorate and of Magnesium Perchlorate in Propylene Carbonate–Tetrahydrofuran Mixtures at 25°C
Authors: Al-Najar A A , Abbo H S 
Published: July 2006

Abstract
The electrical conductances of zinc halides and perchlorate and of magnesium perchlorate in propylene carbonate (PC)–tetrahydrofuran (THF) (1:1 in volume) have been measured at 25 °C. The conductance data were analysed by a minimization technique using the Lee/Wheaton (L/W) and Murphy/Cohen (M/C) equations. The results indicate that all of these salts behave as “weak electrolytes”. Zinc and magnesium perchlorates were found to be anomalous in showing unusually high molar conductance, and in exhibiting a pronounced maximum conductances at low concentrations. Also, it was found that the mode of ionization is specific for the anion involved.
Rhodium Carbonyl Catalyzed Carbonylation of Unsaturated Compounds. IV. Carbonylation and Oligomerization of Diphenylacetylene Catalyzed by Co4(CO)12, Rh4(CO)12, and Ir4(CO)12 under Pressure of Carbon Monoxide
Authors: Hong Pangbu , Mise Takaya , Yamazaki Hiroshi 
Published: July 2006

Abstract
In the presence of Co4(CO)12, Rh4(CO)12, and Ir4(CO)12 catalysts the reaction of diphenylacetylene (1) in 2-propanol under pressure of carbon monoxide gave the hydrocarbonylation products 2 and/or 3 and the oligomers 4 and/or 5, in which the ratios depended on the catalyst employed.
Photoelectrochemical Study of n-InP: Redox Processes Using Electroluminescence as Mechanistic Probe
Authors: Manivannan Ayyakkannu , Hashimoto Kazuhito , Sakata Tadayoshi , Fujishima Akira 
Published: July 2006

Abstract
Electroluminescence (EL) due to band-band transition was observed for n-InP single crystal electrodes in solutions containing current doubling reagents like peroxodisulfate and various redox electrolytes. The mechanism for the EL emission in relation to surface properties of n-InP crystals in these electrolytes is presented. The cathodic decomposition process of n-InP electrodes involved in various electrolytes especially in peroxodisulfate medium has been analyzed from the EL emission as a function of electrode potential under steady state as well as pulsed conditions. The intensity of the EL signal depends on the electron density at the interface which is controlled by the potential and on the chemical composition of the electrode surface. Moreover, a hydrogen evolution reaction reduces the EL efficiency at higher cathodic potentials. Though the potential has no effect on the shape of the EL spectra, a significant change in EL intesity was observed. In all the electrolytes used the InP electrodes seem to decompose during cathodic polarization to form indium metal. The change in the surface composition plays an important role in the relation between potential and the EL intensity. Moreover, during pulsed polarization the EL behavior is different from the steady state conditions and also depends on the concentration of the electrolyte species.
Stability and Resonance Energy of Troponoid Compounds
Authors: Kurihara Teruo , Ishikawa Sumio , Nozoe Tetsuo , Aihara Jun-ichi 
Published: July 2006

Abstract
The fundamental skeleton of the tropones possessing a unique heptagonal structure is predicted to be aromatic with positive resonance energies and conforming to the topological charge stabilization rule (TCS rule). Similarly, naturally occurring tropolones also nicely fit the theory that conformity to the TCS rule gives a stable molecular system. Thus, many of the troponoids so far synthesized and those occurring in nature are energetically very stable molecules as well as being synthetically very accessible. The TCS rule applies very well to the formation mechanism of heterocycle-fused tropones. It is very likely that there are various reaction paths in nature which are compatible with the TCS rule for the formatin of tropylium compounds having annulated heterocycles.
Reaction of Organocobaloxime with Thiol under Irradiation
Authors: Kijima Masashi , Miyamori Kiyokatsu , Nakamura Tomoko , Sato Takeo 
Published: July 2006

Abstract
The reactivity of photoactivated organocobaloxime was investigated by the reaction of thiol. Alkyl(pyridine)cobaloxime and ethyl mercaptoacetate were irradiated with a tungsten lamp under anaerobic conditions in an organic solvent to give ethyl alkylthioacetate, diethyl 2,2′-dithioacetate, and ethoxycarbonylmethylthiocobaloxime. Mechanistic investigations were carried out to determine the reaction course. Sulfide was assumed to be produced via a homolytic substitution between alkylcobaloxime and disulfide formed during the reaction. Disulfide was formed from thiol catalytically in the presence of cobaloxime under anaerobic conditions. Homolytic methyl-transfer scarcely occurred from methylcobaloxime into thiol.
Catalysis of α-Fe and Fe1−xS toward the Hydrogenolysis of trans-Stilbene in Hydroaromatic Hydrocarbon Solvents
Authors: Futamura Shigeru , Fujimoto Ken-ichiro , Kamiya Yoshio 
Published: July 2006

Abstract
The Fe-catalyzed hydrogenolysis of trans-stilbene was carried out in aromatic hydrocarbon solvents at 380 °C. α-Fe and pyrrhotite catalyze bimolecular hydrogen transfer from hydroaromatic hydrocarbons to trans-stilbene and hydroaromatic hydrocarbon-mediated hydrogenolysis of trans-stilbene by molecular hydrogen at 380 °C. This catalyzed hydrogen transfer proceeds by radical mechanism. The product distribution is affected by the catalyst species. Pyrrhotite catalyzes the hydrogenation of trans-stilbene more effectively than α-Fe. Both the iron catalysts are inactive toward the cleavage of carbon to carbon single bond in bibenzyl.
Preparation and Characterization of a 345 nm Absorbing Reductant Derived from Dehydro-l-Ascorbic Acid
Authors: Tanaka Hidehiko , Kimoto Eiji 
Published: July 2006

Abstract
The addition of sodium hydroxide to an ethanolic dehydro-l-ascorbic acid solution produced a yellowish precipitate which was enriched by a reductant possessing absorption maxima at 345 and 225 nm. This reductant was purified by DEAE-Sepharose column chromatography and Cellulofine-gel chromatography; on the basis of physicochemical analyses it was deduced to be the 2,3-enediol form of 2,3-diketo-l-gulono-δ-lactone (2,3,6-trihydroxy-4-oxo-2-hexen-5-olide). The process, derived from dehydro-l-ascorbic acid, involved a hydrolytic cleavage of a 5-membered γ-lactone ring, conversion to the 2,3-enediol form and rearrangement to 6-membered δ-lactone. The marked bathochromic shift of the absorption maximum of this reductant from that of ascorbic acid (265 nm) could be due to an extended conjugation among the enediol group and two carbonyl groups on both sides.
Facile Reduction of Dithiocarbonates Derived from Secondary Alcohols with n-Bu3SnH–Et3B and Synthesis of 2-Furanthiones and 2-Furanones by Intramolecular Addition of Alkoxythiocarbonyl Free Radicals to Acetylenic Linkages
Authors: Nozaki Kyoko , Oshima Koichiro , Utimoto Kiitiro 
Published: July 2006

Abstract
The reduction of dithiocarbonates or thiocarbonates by n-Bu3SnH–Et3B easily gives the corresponding hydrocarbons. The intermediate alkoxythiocarbonyl radical equivalents are trapped by properly located carbon–carbon multiple bonds. The dithiocarbonates derived from either homopropargylic or homoallylic alcohols produce tetrahydrofuranones upon treatment with n-Bu3SnH–Et3B. Application of this new method to the conversion of carbonyl compounds into olefins is also described.
The Catalytic Activity of Hydrous Zirconium Oxide Calcined at Several Temperatures
Authors: Shibagaki Makoto , Takahashi Kyoko , Kuno Hideyuki , Matsushita Hajime 
Published: July 2006

Abstract
Hydrous zirconium oxide is an amorphous solid and has several catalytic activities. The oxide was changed to crystalline zirconia by calcination at a high temperature, and the catalytic activities were lowered. The correlation between the surface property and the catalytic activity was investigated on hydrous zirconium oxide calcined at several temperatures; the best activity was obtained in the oxide calcined at 300°C.
Studies of the Hydrous Silicon–Titanium(IV) Oxide Ion Exchanger. II. Affinity for Various Cations and Thermal Stability
Authors: Yamazaki Hiromichi , Kanno Yasuhito , Inoue Yasushi 
Published: July 2006

Abstract
The affiinity for various cations and the thermal stability were studied on hydrous silicon–titanium(IV) oxide ion exchangers with various titanium contents. An exchanger with 52 mol% Ti shows a higher affinity for an alkali metal ion having a smaller hydrated radius but similar affinity, which depends little on the pH′s of solutions, for alkaline earth metal ions, except for Ba2+. In the sorption of transition metal ions, the formation of a covalent bond is a factor in determining the selectivity of the exchanger, along with the remote coulombic interaction. The composition dependence of the affinities for Cs+, Ba2+, Co2+, Eu3+, and UO22+ was explained in terms of the acid-base properties of the exchangers. The exchangers with 37 to 67 mol% Ti do not suffer from any drastic change in the surface area and in the crystallinity upon heating up to 540 °C, and are much more heat-resistant than the component simple hydrous metal oxides. The degree of the decrease in the exchange capacity upon heat treatment is larger in exchangers with a higher titanium content. The effect of a heat treatment on the acid-base property and the affinity for cations was also studied.
Selenium Content and Its Oxidation State in Igneous Rocks, Rock-Forming Minerals, and a Reservoir Sediment
Authors: Tamari Yuzo , Ogawa Hideaki , Fukumoto Yuji , Tsuji Haruo , Kusaka Yuzuru 
Published: July 2006

Abstract
The selenium content of 188 samples (115 igneous rocks, 46 sedimentary rocks, and 27 sediments, including 38 rock-forming minerals and 25 rock reference materials) issued from the Geological Survey of Japan were determined. In these samples selenium was distributed over a wide range of concentrations, 0.1–19500 ng g−1. Especially, selenium was rich in alkali-feldspar (7.5–149 ng g−1) as well as in plagioclase (3.6–147 ng g−1), though not in mica (2.4–14.8 ng g−1) and quartz (0.6–6.4 ng g−1). Selenium, rich in feldspar, was easily dissolved as selenite with CO2-bubbling water. In a reservoir sediment-core (from the surface to 15-cm depth), selenite and much organically-complexed selenium were dissolved with 0.1 M hydrochloric acid and the subsequent 1 M sodium hydroxide solutions, respectively.
Salen-Capped Porphyrins as an Active Site Model of Metalloenzymes: Synthesis and Their Intramolecular Interactions between the Metal Complexes
Authors: Maruyama Kazuhiro , Kobayashi Fumikazu , Osuka Atsuhiro 
Published: July 2006

Abstract
Reversible Schiff base condensation of bis(salicylaldehyde)-linked porphyrins and ethylenediamine under high dilution gave salen-capped porphyrins in high yields. Site selective insertion of nickel(II) into the salen and zinc(II) into the porphyrin gave the corresponding Ni–Zn heterobinuclear complexes. The geometrical relationship between the two metal centers was estimated by 1H NMR spectroscopy. The porphyrin π electronic state of these Ni-salen-capped Zn-porphyrins was perturbed by their Ni-salen cap, which was studied by 400 MHz 1H NMR, UV-Vis spectra, fluorescence, and cyclic voltammetry measurements.
Spiral Growth on the Metal Complex Crystal
Authors: Tange Koichi , Suzuki Kazuo , Sasaki Ken-ichi , Kuroda Yasushige , Yoshikawa Yuzo 
Published: July 2006

Abstract
Spiral growth patterns were found on the crystals of (+)d-and (−)d-[Co(ox)(en)2]Cl·4H2O. The handedness of the spirals was statistically counted on each enantiomeric complex crystal. No stereoselectivity of the handedness suggests that the visible spirals do not arise from the molecular or crystal structural origin, but more macroscopic one.
In Situ Observation of a Dynamically Light-Induced Morphological Transformation at an n-MoS2 Electrode Surface by a Scanning Tunneling Microscope
Authors: Hinokuma Kohichiroh , Sakamaki Kenji , Fujishima Akira 
Published: July 2006

Abstract
A scanning tunneling microscope (STM) under photoelectrochemical control was used to investigate an in situ dynamically light-induced morphological transformation at an n-MoS2 electrode surface in CH3CN by the addition of I− ions. The anistropic photocorrosion rate around the “disk-like” cavities was extremely slow due to the effects of the added I− ions when compared to the results achieved by adding only H2O.
Studies on Aromatic Sesquiterpenes. XII. Synthesis of (±)-cis-5-Hydroxycalamenene
Authors: Tanaka Juichi , Adachi Kazuo 
Published: July 2006

Abstract
Starting from o-cresol, (±)-cis-5-5-hydroxycalamenene was synthesized through 4-isopropyl-5-methoxy-6-methyl-1-tetralone as a key intermediate and identified with the natural compound spectroscopically.
X-Ray Structures of Molybdenum(V) Tetraphenylporphyrins, MoO(tpp)NCS·CH2Cl2 and MoO(tpp)F
Authors: Imamura Taira , Furusaki Akio 
Published: July 2006

Abstract
The molecular structures of the title complexes have been determined by a single-crystal X-ray diffraction method. The crystals of MoO(tpp)NCS·CH2Cl2 (tpp= 5,10,15,20-tetraphenylporphyrinato) and MoO(tpp)F are triclinic and tetragonal respectively. An isothiocyanate ion is coordinated to the central molybdenum atom at an angle of 145° with the Mo–N(NCS) bond through the nitrogen atom. In both complexes, the molybdenum atoms are displaced toward oxo ligands from the 4N plane composed of pyrrole nitrogens.
Polymerization of Lipid Bilayer Initiated by a Redox Initiator: Effect of Polymerization on Dyes in the Inner Water Phase
Authors: Hasegawa Etsuo , Kimura Noboru , Hatashita Masanori , Tsuchida Eishun 
Published: July 2006

Abstract
The polymerization of the liposomal lipid bilayers of phoshpolipids having one or two diene groups was studied by the use of a redox initiator (NaHSO3/K2S2O8) at low temperature (8 °C). The soluble and insoluble polymers were obtained, respectively. The membrane polymerization itself had small effect on the dye in the inner water phase.
Unit Subduced Cycle Indices with and without Chirality Fittingness for Ih Group. An Application to Systematic Enumeration of Dodecahedrane Derivatives
Authors: Fujita Shinsaku 
Published: July 2006

Abstract
Subduction of the coset representations of Ih point group produces tables of unit subduced cycle indices (USCIs) with and without chirality fittingness (CF). These indices are applied to the enumeration of dodecahedrane derivatives with respect to their molecular formulas as well as to their symmetries. The USCIs are effective to the enumeration of such derivatives as having only achiral substituents on the vertices of a dodecahedrane skeleton. On the other hand, the USCI–CFs are used for enumerating dodecahedrane derivatives with achiral and chiral substituents. Substitutions on the edges of the dodecahedrane skeleton are also discussed in terms of the present USCI approach.
The Electrochemical Study of Ag(II) Complexes of Polyaza Macrocycles and Their Acetic Acid Derivatives
Authors: Kodama Mutsuo , Mahatma Anung Budhi , Koike Toru , Kimura Eiichi 
Published: July 2006

Abstract
Although an attempt to isolate pure crystallines of Ag(II) complexes failed, we could prepare stable aqueous solutions of the Ag(II) complexes of [15]aneN5, [16]aneN5, and their acetic acid derivatives by disproportionation reactions of Ag(I) induced by these polyaza macrocycles, and have investigated their electrochemical redox behaviors using conventional voltammetric methods. All Ag(II) complexes including the [14]aneN4 (cyclam) complex undergo a reversible two-electron reduction at DME (dropping mercury electrode). From the potential where the i2⁄(i1–i) ratio is unity, the log formation constants were determined to be 43.4, 43.6, 43.3, 39.3, and 42.5 for the cyclam, [15]aneN5, [16]aneN5, cyclam-tetraacetic acid, and [15]ane5-pentaacetic acid complexes, respectively. Cyclic voltammetric (CV) oxidation scans at the glassy carbon electrode showed a reversible one-electron response (separation of anodic and cathodic peak potentials, ΔEp′=70 mV; the ratio of anodic and cathodic peaks, (ip)c⁄(ip)a′=1), which can be ascribed to a reversible Ag(III)/Ag(II) redox change. Though the acetate groups attached to the nitrogen atoms contribute to the net destabilization of the Ag(II) complexes, they exert a large positive effect on the thermodynamic stability of the Ag(III) state.
Association of C5–C9 Normal Alkanes with Cyclodextrins in Aqueous Medium
Authors: Sanemasa Isao , Osajima Tomonori , Deguchi Toshio 
Published: July 2006

Abstract
The complex formation of cyclodextrin (CyD, host) with C5 to C9 normal alkanes (guests) has been studied in aqueous medium at 25°C by making use of the volatilization rate of alkane molecules from aqueous into gaseous phase. In the excess of the host, β- and γ-CyDs form 1:1 complexes, while α-CyD forms 1:1 and 2:1 (host: guest) complexes. With an increase in the chain length of alkane, association constants for three CyDs increased; in the case of α-CyD, the 1:1 association constant for C9 was identical to that for C8, while the 2:1 association constant continued to increase. The cavity size of CyD, the alkane chain length, and hydrophobicity and surface area of alkane molecules were taken into account to discuss the host-guest inclusion mechanism.
Substituent Effects on the Carbon-13 NMR Chemical Shifts of Cyclopropyl Carbons in p-Substituted(cis- and trans-2-Chlorocyclopropyl)benzenes
Authors: Kusuyama Yoshiaki , Kagosaku Tamami , Hasegawa Takeshi 
Published: July 2006

Abstract
Carbon-13 chemical shifts have been measured for the cyclopropyl carbon atoms of twenty one p- substituted (cis- and trans-2-chlorocyclopropyl)benzenes. The substituent induced chemical shifts (SCS) for the trans derivatives are shifted down field by electron-acceptor substituents and upfield by electron-donating substituents (normal SCS). This SCS trend is the same as those observed for the p-substituted cyclopropylbenzenes, while the SCS range is small because of the decreased polarization of C-1–C-2 bonding due to the attached chlorine atom. For the cis derivatives, SCS for C-1 and C-3(CH2) carbons were also normal, while no measurable SCS was observed for C-2(CCl). The SCS well fitted with the LSFE equation, indicating that the SCS were controlled mainly by a polar effect, except for C-2(CCl, cis).