bluuebunny/crossref_metadata_2025 huggingface dataset:
Tetrabutylphosphonium Cation as a Template in the Kinetics of the Crystallization of B-ZSM-5
Authors: Sundaramurthy Vedachalam , Lingappan Nachiappan
Published: September 2002

Pentasil zeolite, B-ZSM-5 and Al-ZSM-5, have been synthesized hydrothermally using orthoboric acid and sodium aluminate, respectively, with ethyl silicate-40 so as to obtain a gel mix with SiO2/M2O3 = 22 (where M = B or Al) employing a tetrabutylphosphonium bromide (TBPBr) template at temperatures of 423, 448, and 473 K. The crystallization kinetics followed by XRD, FTIR, and SEM studies clearly demonstrate the influence of the size of the hetero atoms on the rate of nucleation and crystallization. The values of the apparent activation energies for nucleation and crystal growth indicate that both nucleation and crystal growth are faster for the Al-ZSM-5 system than for the B-ZSM-5 system. Avrami-Erofeev parameters for both systems have been evaluated. Correlations were found between the kinetics of crystallization and the characteristics of the formed crystal. SEM pictures show similar, but larger sized, crystals for the Al-ZSM-5 system than those of the B-ZSM-5 system. XRD, FTIR, and chemical analysis have revealed that the mechanism operating during crystallization is the same, and that hetero atoms become incorporated with the framework during the nucleation step, itself, with boron at a slower rate.
The Direct Effects of Alkali Metal and Alkaline Earth Metal Perchlorates on the Equilibria of Acid-Base Indicators (Sulfonephthaleins) in Acetonitrile Solution
Authors: Hojo Masashi , Ueda Tadaharu , Kawamura Kazushi , Yamasaki Masanori
Published: September 2002

With the addition of alkali metal (M+) and alkaline earth metal (M2+) perchlorates, the cause of the color changes of several sulfonephthaleins of various pKa values, i.e., Thymol Blue, Phenol Red, Bromothymol Blue, and Bromocresol Green, in acetonitrile solutions were examined by means of spectrophotometry and 1H NMR. Upon the addition of ≥ 0.1 mol dm-3 LiClO4 to 1.0 × 10-4 mol dm-3 Phenol Red, the γ-sultone ring of the sulfonephthalein was cleaved to give absorption bands at around 410 and 500 nm. The band at 500 nm was assigned to the acid form, and that around 410 nm to a quinonoid structure (the intermediate form) which would be formed by deprotonation from the acid form. The effects of NaClO4 were much smaller than those of LiClO4. Magnesium and barium perchlorates caused larger effects than LiClO4; however, a nonmetallic salt, Et4NClO4, caused almost no effects. In addition, a purple-red colored species (λmax = 563 nm), a basic form, was also produced from Phenol Red by the addition of ≥ 0.2 mol dm-3 Mg(ClO4)2. Interestingly, the metal ions assisted not only the acid effects of CH3SO3H, but also the base effects of Et3N or 1,1,3,3-tetramethylguanidine on Phenol Red or Bromothymol Blue in acetonitrile. 1H NMR spectra of the sulfonephthaleins confirmed the opening of the γ-sultone rings in the presence of the metal salts. The ring cleavage upon the addition of the metal ions was considered from the standpoint of not ``medium effects'', but a direct chemical interaction between the metal ions and the sulfonate ion (function) in the sulfonephthaleins.
A Family of Dinuclear Vanadium(V) Complexes Containing the {OV(μ-O)VO}4+ Core: Syntheses, Structures, and Properties
Authors: Sangeetha Nimma Rajaiah , Pal Samudranil
Published: September 2002

Dark-brown complexes of {OV(μ-O)VO}4+ with the general formula [(VOL)2O] were isolated from reactions of bis(acetylacetonato)oxovanadium(IV) and aroylhydrazones of salicylaldehyde or of 5-methoxysalicylaldehyde (H2L, two H stand for the dissociable protons at the phenol and the amide functionalities) in acetonitrile. The infrared spectra of these complexes are consistent with the dianionic form of the ligands. The electronic spectral profiles are very similar and display strong absorptions in the range 425—263 nm due to ligand-to-metal charge transfer and intraligand transitions. The proton NMR spectra suggest that in solution the two ligands in each complex are magnetically equivalent. The complexes are redox active and display a reduction response in the potential range -0.28—0.47 V (vs. Ag/AgCl). The molecular structures of the complexes were determined by X-ray crystallography. The deprotonated dianionic planar ligands coordinate the metal ions through the phenolate-O, the imine-N, and the amide-O atoms forming a six-membered and a five-membered chelate ring. The metal ions in each complex are essentially in a square-pyramidal O4N coordination sphere. The O, N, O-donor ligand and the bridging oxygen atom constitute the square plane and the oxo group occupies the apical position. The metal center is displaced from the basal plane towards the apical oxo group by 0.44—0.57 Å. The V-O-V bridge angles in the complexes are very similar and within the range 112.86(13) to 115.89(12)°.
Observation of Molecular Alignments and Dimer Formation of Bis(5-alkylsalicylidene)ethylenediaminatonickel(II) in a Monolayer
Authors: Fujii Takashi , Miyamura Kazuo
Published: September 2002

A monolayer of bis(5-butylsalicylidene)ethylenediaminatonickel(II), prepared on highly oriented pyrolytic graphite by the Langmuir-Blodgett method, was observed by scanning tunnelling microscopy. The image revealed that one of the monolayers was comprised dimers of complexes, similar to that observed in the crystalline phase. The π-A isotherms of the analogues of various alkyl chain lengths were measured, and the critical area of the monolayer was found to decrease by 20% when the alkyl chain length decreased from 3 (propyl) to 2 (ethyl). This decrease of the critical area is explained by the presence of CH-π interactions between the π conjugated system of the salen moiety, and α- and γ-methylenes of the alkyl side chain.
Thermal Dehydrogenation Reacton of [N,N′-Bis(3-ethoxysalicylidene)-1,2-diphenyl-1,2-ethanediaminato]nickel(II) with [VO(salen)]NO3 in the Solid State
Authors: Hoshina Gakuse , Tsuchimoto Masanobu , Ohba Shigeru
Published: September 2002

A dehydrogenation reaction of the red-brown powder of [Ni(3-EtOsal-meso-stien)] (H2(3–EtOsal–meso–stien) = N,N′-bis(3-ethoxysalicylidene)-(R,S)(S,R)-1,2-diphenyl-1,2-ethanediamine) did not occur by heating solely in the air up to 210 °C. However, the reaction occurred upon heating together with [VO(salen)] (H2(salen) = N,N′-disalicylidene-1,2-ethanediamine) in the air at 190 °C, and a red powder of [Ni(3-EtOsalton)] (H2(3-EtOsalton) = N,N′-bis(3-ethoxysalicylidene)-1,2-diphenyl-1,2-ethenediamine) was obtained. The dehydrogenation reaction could also be carried out under Ar at 160 °C by mixing with [VO(salen)]NO3. These facts revealed that the oxidants in solid state dehydrogenation in air are the VV species originating from the VIV=O complex. The crystal structures of [Ni(3-EtOsal-meso-stien)]·CH3CN·H2O, (1); [Ni(3-EtOsal-rac-stien)]·0.5H2O, (2); and [Ni(3-EtOsalton)]·CH3OH·1.33H2O, (3) were determined by X-ray analyses. [Ni(3-EtOsalton)] was prepared in a dioxane solution of [Ni(3-EtOsalstien)] using DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) as an oxidant. The rac complex, [Ni(3-EtOsal-rac-stien)] (H2(3–EtOsal–rac–stien) = N,N′-bis(3-ethoxysalicylidene)-(R,R)(S,S)-1,2-diphenyl-1,2-ethanediamine), is less reactive in dehydrogenation than the meso in the solid state as well as in solution. The molecular structures in (1) and (2) indicate that the benzylic H atoms are sterically protected by phenyl groups in the rac complex, but are exposed to the oxidant in the meso complex.
A CIDEP Study on the Photosensitized Reaction of Maleimide with Xanthone: Addition Effect of Hydrochloric Acid
Authors: Ohara Keishi , Nagaoka Shin-ichi , Mukai Kazuo
Published: September 2002

The photosensitized reaction of maleimide (MI) with xanthone (Xn) in 2-propanol was investigated by the time-resolved EPR method. The emissive CIDEP spectrum observed in neat 2-propanol is predominantly assigned to two kinds of MI alkyl-type radicals. On the other hand, the absorptive spectrum of the MI anion radical has been newly observed in 2-propanol including hydrochloric acid. The addition effect of hydrochloric acid indicates the existence of two mechanisms for the photosensitization of MI by Xn. One is a typical triplet-triplet energy transfer followed by hydrogen abstraction by the triplet state of MI from the solvent. The other is an electron-transfer process to MI from the Xn ketyl radical produced primarily by a fast reaction of the triplet Xn with HCl. The spin-polarization transfer mechanism based on these photosensitization processes can successfully explain the present CIDEP results. The effect of water and the sensitizer dependence on the above reaction were also investigated.
A Novel-Type Mixed-Ligand Polyoxotungstolanthanoate, [Ln(BW11O39)(W5O18)]12- (Ln = Ce3+ and Eu3+)
Authors: Naruke Haruo , Yamase Toshihiro
Published: September 2002

Two isostructural anions, [Ln(BW11O39)(W5O18)]12- (Ln = Ce and Eu), were isolated as K+ salts from aqueous solutions containing tungstate, Ln3+, and BO33-, at pH = 7. An X-ray crystallographic analysis showed that the Ln3+ center in the anion is chelated by two kinds of tetradentate polyoxotungstate ligands, [W5O18]6- and α-[BW11O39]9- with a square antiprismatic LnO8 configuration, which are monovacant derivatives of [W6O19]2- and α-[BW12O40]5-, respectively. The anion is of approximate Cs symmetry, and the observable asymmetry of K-O bonding between two different K+ cations and the anion causes the two mirror planes within [(W5O18)Ln]3- and [(BW11O39)Ln]6- moieties to be canted to each other by 5.2° for Ln = Ce and 4.1° for Ln = Eu.
Reversibility in the Formation of Oxo(peroxo)porphyrinatomolybdenums
Authors: Fujihara Tetsuaki , Hoshiba Koji , Sasaki Yoichi , Imamura Taira
Published: September 2002

Reversibility in the formation reaction of a series of the oxo(peroxo)porphyrinatomolybdenums, [MoVIO(tmp)(O2)] 1, [MoVIO(tdcpp)(O2)] 2, [MoVIO(ttp)(O2)] 3, [MoVIO(tdmpp)(O2)] 4, and [MoVIO(tpp)(O2)] 5, was studied. In these dioxygen complexes with various porphyrin rings, two complexes, 2 and 4, were newly prepared by the solid-state reactions of corresponding Mo(IV) complexes with O2. All the complexes were characterized by IR, 1H NMR, and UV-vis spectroscopic measurements. In the reaction of O2 with [MoIVO(tdcpp)] 2r, which has bulky substituents with an electron-withdrawal character, the association rate constant was determined to be 1.2 × 10-2 dm3 mol-1 s-1 in toluene at 20 °C. The value of the rate constant is about one thirtieth of that for [MoIVO(tmp)] 1r, which also has bulky substituents. The result indicates that the electronic effects of the porphyrin rings, which reflect on the redox potentials of the central molybdenum ion, are important in determining kinetic and thermodynamic stability of the dioxygen complexes. All the dioxygen complexes undergo deoxygenation upon photoirradiation to give corresponding [MoIVO(por)]. The redioxygenation profiles of [MoIVO(por)] in the dark were also significantly affected by the steric bulkiness of the porphyrin ligands. While the bulky porphyrin complexes of 1 and 2 gave full recovery of the dioxygen complexes in the dark, less bulky porphyrin complexes of 3, 4, and 5 undergo some side reactions to Mo(V) species. The rate and extent of the Mo(V) complex formations increase with decreasing steric bulkiness.
Unsymmetrical Oxygenation Products of [Pd(mnt)2]2-: Syntheses and Crystal Structures of (Bu4N)2[Pd(mnt){O2S2C2(CN)2}] and One-Dimensional Coordination Polymer (Bu4N)2[AgPd(mnt) {O2S2C2(CN)2}]2 (mnt = 1,2-Dicyano-1,2-ethylenedithiolato)
Authors: Sugimoto Kunihisa , Kuroda-Sowa Takayoshi , Maekawa Masahiko , Munakata Megumu
Published: September 2002

Oxidation of [Pd(mnt)2]2- by H2O2 produces a sulfonyl-containing [Pd(mnt){O2S2C2(CN)2}]2- (12-). Addition of AgClO4 to 12- results in the formation of [AgPd(mnt){O2S2C2(CN)2}]22- (22-). Both compounds crystallize with a bulky cation Bu4N+ to form (Bu4N)21 and (Bu4N)22, which are characterized by single crystal X-ray analyses. 12- retains a planar structure except for the sulfonyl oxygen atoms. The electronic absorption band observed at 387 nm (sh) is assigned to d-d transition. 22- has a double-decker structure consisting of two [Pd(mnt){O2S2C2(CN)2}]2- anions bridged by two Ag(I) ions through Ag-S bonds. Two terminal CN groups in 22- coordinate to the neighboring Ag(I) ions, forming a one-dimensional chain structure. Crystallographic data are as follows. (Bu4N)21: PdS4O2N6C40H72, triclinic, P1-, a = 12.145(2), b = 10.991(3), c = 10.156(2) Å, α = 65.09(2), β = 88.93(2), γ = 84.97(2)°, Z = 1. (Bu4N)22: Ag2Pd2S8O4N10C48H72, monoclinic, P21/c, a = 9.649(2), b = 13.235(2), c = 25.107(2) Å, β = 91.03(1)°, Z = 2.
Competitive [3+2] and [4+2] Cycloaddition Reactions of 2-Furaldehyde Phenylhydrazone with Alkenes
Authors: Amarasekara Ananda S , Pathmasiri W Wimal
Published: September 2002

Maleimides react with 2-furaldehyde phenylhydrazone 1 at the furan ring to give 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones when equimolar mixtures are refluxed in benzene for shorter reaction times. Excess maleimides and longer reaction times give mixtures of 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones and 3-(1,3-dihydro-1,3-dioxo-4-isoindolyl)-1,6a-dihydropyrrolo[3,4-c]pyrazolo-4,6(3aH,5H)-diones resulting from [4+2] and [3+2] double-cycloaddition. Reactions of 1 with dimethyl acetylene dicarboxylate give the double-cycloaddition product dimethyl-3[4-hydroxy-2,3-bis(methoxycarbonyl)phenyl]-1-phenylpyrazole-4,5-dicarboxylate. Methyl acrylate and acrylonitrile gives only the [3+2] cycloaddition products, 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carboxylic methyl ester and 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carbonitrile, respectively.
Two-Step Concerted Mechanism for the Hydrocarbon Hydroxylation by Cytochrome P450
Authors: Yoshizawa Kazunari , Ohta Takehiro , Eda Masataka , Yamabe Tokio
Published: September 2002

A possible two-step mechanism for the hydrocarbon hydroxylation by the oxoferryl active species of cytochrome P450 is discussed. We propose that the catalytic reaction is initiated by the formation of a reactant complex involving a five-coordinate carbon species or a σ-complex, followed by concerted hydrogen and alkyl migrations which lead to the formation of a product complex involving alcohol as a ligand. The porphyrin ring is predicted from molecular mechanics and extended Hückel calculations to be significantly bent in the reactant complex and in the hydroxy intermediate to form an energetically preferred octahedral environment at the iron active center. Such bent structures for the porphyrin ring are consistent with observed cis-coordination geometries for the M(porphyrin)L2 complexes, in which M is a large transition-metal ion and L is a ligand. We suggest that possible inversion at the five-coordinate carbon species in the reactant complex can occur to lead to partial inversion of stereochemistry at a labeled carbon.
Synthesis of Dictyopterene A: Optically Active Tributylstannylcyclopropane as a Chiral Synthon
Authors: Itoh Toshiyuki , Inoue Hitomi , Emoto Sachie
Published: September 2002

Synthesis of (1S,2R)-1-[(E)-hex-1-en-1-yl]-2-vinylcyclopropane (dictyopterene A), which was isolated from the essential oil of algae of the genus Dictyopteris in Hawaii, has been demonstrated using optically active tributylstannylcyclopropane as a starting chiral synthon.
Synthesis of a Chiral Precursor for No-Carrier-Added (NCA) PET Tracer 6-[18F]Fluoro-L-dopa Based on Regio- and Enantioselective Alkylation of 2,4-Bis(chloromethyl)-5-iodoanisole
Authors: Kuroda Chiaki , Ochi Atsushi , Nakane Noritoshi , Umeyama Takashi , Muto Nobuko , Niimura Nami , Teramoto Yoshiki , Nogami Hiroyuki , Reddy Guvvala N
Published: September 2002

(2S,5S)-5-(3-Formyl-6-iodo-4-methoxybenzyl)-1-t-butoxycarbonyl-2-t-butyl-3-methyl-4-imidazolidinone (11), a chiral intermediate towards NCA PET tracer 6-[18F]fluoro-L-dopa (1), was synthesized from 3-iodoanisole in four steps. 3-Iodoanisole was first bischloromethylated to 2,4-bis(chloromethyl)-5-iodoanisole (14). Regio- and enantio-selective alkylation of 14 with (S)-1-(t-butoxycarbonyl)-2-t-butyl-3-methyl-4-imidazolidinone (12) afforded 33, which was then hydrolyzed and oxidized to the desired intermediate 11.
A Practical Synthesis of Optically Active (R)-2-Propyloctanoic Acid: Therapeutic Agent for Alzheimer's Disease
Authors: Hasegawa Tomoyuki , Yamamoto Hisashi
Published: September 2002

(R)-2-Propyloctanoic acid has been developed as a novel therapeutic agent for Alzheimer's disease. A large-scale synthesis of this candidate was achieved by using Oppolzer's camphorsultam as a chiral auxiliary under improved conditions. It was essential for the successful synthesis of this compound to utilize a new removal method for the chiral source with a combination of tetrabutylammonium hydroxide and hydrogen peroxide. The present process afforded the desired product in high yield with high optical purity.
The γ-Silicon Effect. IV. The Solvolysis Mechanism of 3-(Aryldimethylsilyl)propyl p-Toluenesulfonates
Authors: Nakashima Tohru , Fujiyama Ryoji , Kim Hyun-Joong , Fujio Mizue , Tsuno Yuho
Published: September 2002

Solvolysis rates of 3-(aryldimethylsilyl)propyl p-toluenesulfonates were determined in various solvents. The reaction mechanism of this simple γ-silyl system was clarified based on the solvent effect and the substituent effect analyses. The solvent effect on this system clearly showed the nucleophilic assistance of solvent, but failed to correlate linearly with the extended Winstein-Grunwald equation, substantiating that the reaction should not proceed through either the formation of the cation intermediate or the SN2 mechanism. This suggests that the reaction takes place in competition between γ-silyl-assisted (kSi) and solvent-assisted (ks) pathways, and that the competition ratio varies with solvents and with aryl substituents. Product analysis revealed that the former pathway gave only cyclopropane and the latter gave only the substitution products. The overall kt value could be dissected into the partial rate constants kSi and ks for the two pathways by using product ratios. The effects of aryl substituents at the γ-silyl atom on kSi pathway were correlated with unexalted σ° parameter, giving the ρ values of -1.0 in 60E and -1.32 in 97Tw, and reflecting the delocalization of incipient carbocationic charge by participation of the Si-Cγ bond. The substituent effects on the ks pathway were negligibly small; this is in line with the remote reaction center in the concerted SN2 mechanism.
Theoretical Valence Photoelectron and UV-visible Absorption Spectra of Four Stable Conductive Molecules Obtained by MO Calculations
Authors: Takaoka Kazuchiyo , Maeda Sigehiro , Miura Hidetoshi , Otsuka Takao , Endo Kazunaka , Chong Delano Pun
Published: September 2002

Theoretical valence photoelectron and UV-visible absorption spectra of four stable conductive molecules (N, N′-diphenyl-1,4-phenylenediamine (DPPD), p-quaterphenyl (PQP), 2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23H-porphyrin (OEP), and 29H, 31H-phthalocyanine (PC)) have been obtained by semiempirical HAM/3 and ZINDO MO calculations, respectively. The Al K  α photoelectron spectra were simulated using Gaussian lineshape functions of an approximate linewidth 0.10 Ek (Ek = E′k - WD), where E′k is the vertical ionization potential (VIP) of each MO and WD is a shift to account for sample work function and other energy effects, as stated in previous studies. The theoretical valence spectra of the four conductive compounds are in good accordance with the observed ones. The theoretical UV-visible absorption curves of DPPD, PQP, OEP, and PC were obtained after AM1 calculations with COSMO option to reflect solvent effects. The absorption curves as simulated with Gaussian lineshape functions of a constant linewidth of 0.003 eV. Correspond well to the observed spectra. For PC, the simulated spectrum which consists of 0.5 inner protonation (IP) and 0.5 outer protonation (OP) types for PC-ring shows much better agreement with the experimental spectrum in H2SO4 than the spectrum of either IP or OP type alone.
The Conformation of de Novo Designed Amphiphilic Peptides with Six or Nine L-2-(2,2,2-Trifluoroethyl)glycines as the Hydrophobic Amino Acid
Authors: Arai Toru , Imachi Takashi , Kato Tamaki , Nishino Norikazu
Published: September 2002

Amphiphilic 21-peptides with six and nine L-2-(2,2,2-trifluoroethyl)glycines as the hydrophobic amino acids and lysine and glutamic acid as the hydrophilic amino acids were synthesized. The CD spectra showed that these peptides with L-2-(2,2,2-trifluoroethyl)glycines took a random conformation in H2O. On the contrary, similar amphiphilic 21-peptides with leucine as the hydrophobic amino acids took a helical conformation in H2O. The peptides with L-2-(2,2,2-trifluoroethyl)glycines took a helical conformation in H2O containing a > 20% volume of 2,2,2-trifluoroethanol. These facts suggested the hydrophobic nature of the L-trifluoroethylglycines. The peptide with six L-2-(2,2,2-trifluoroethyl)glycines took a helical structure in methanol, however it slowly changed into the β-structure within 24 h. Interestingly, the peptide with nine L-2-(2,2,2-trifluoroethyl)glycines formed a stable helix under the same conditions. The peptide with nine L-2-(2,2,2-trifluoroethyl)glycines preferred a helical structure, probably because the assembling of the Tfeg side chains was more effective in forming its helix rather than the β-structure.
Catalytic Asymmetric Addition of Dialkylzinc to 3,4-Dihydroisoquinoline N-Oxides Utilizing Tartaric Acid Ester as a Chiral Auxiliary
Authors: Ukaji Yutaka , Shimizu Yuuko , Kenmoku Yuuichi , Ahmed Alauddin , Inomata Katsuhiko
Published: September 2002

The catalytic asymmetric addition of dialkylzinc to a carbon-nitrogen double bond in 3,4-dihydroisoquinoline N-oxides was achieved by utilizing a catalytic amount of 2-magnesium 3-zinc salt of dicyclopentyl (R,R)-tartrate to afford (S)-1-alkyl-2-hydroxy-1,2,3,4-tetrahydroisoquinolines. In order to realize higher enantioselectivity, it was crucial to add the nitrones slowly into dialkylzinc in the presence of a catalytic amount of the 2-magnesium 3-zinc salt of (R,R)-tartrate.
Synthesis and Properties of (η3-1-Methylallyl)palladium(II) Formates as Models of Intermediates in the Palladium-Catalyzed Reductive Cleavage of Allylic Carboxylates and Carbonates with Formic Acid
Authors: Oshima Masato , Sakamoto Toshiaki , Maruyama Yooichiroh , Ozawa Fumiyuki , Shimizu Isao , Yamamoto Akio
Published: September 2002

In order to gain insight into the mechanism of the regioselective formation of alkenes in the palladium-catalyzed reductive cleavage of allylic carboxylates or carbonates with formic acid, two types of (η3-1-methylallyl)palladium formates (P1 and P2 types) have been prepared as simple models of catalytic intermediates. The P1 type is a neutral complex coordinated with one tertiary phosphine ligand and a formato ligand: [Pd(η3-MeCHCHCH2)(O2CH)(L)] (L = PMePh2, PMe2Ph, PMe3, P(o-tolyl)3); the P2 type is a cationic complex bearing two tertiary phosphine ligands and a formate counter anion: [Pd(η3-MeCHCHCH2)L2]+CO2H- (L = PMePh2, PMe2Ph, PMe3). The structures and dynamic behavior of the complexes in solution have been examined in detail by NMR spectroscopy. Studies on the thermolysis of the P1 and P2-type complexes have clearly provided the following mechanistic viewpoints: (1) 1-butene and 2-butene are formed from the P1 species; (2) butadiene is liberated from the P2 species; (3) the ratio of 1-butene to 2-butene increases as the bulkiness of phosphine ligand increases. A mechanism involving two geometrical isomers of [Pd(η3-MeCHCHCH2)(H)(L)], which are formed by decarboxylation of the P1-type complexes, has been proposed for the formation of butenes.
Synthesis, Chemi- and Bioluminescence Properties, and Photolysis of a Coelenterazine Analogue Having a Photoreactive Azido Group
Authors: Zheng Jing Ling , Chen Feng Qi , Hirano Takashi , Ohmiya Yoshihiro , Maki Shojiro , Niwa Haruki , Ohashi Mamoru
Published: September 2002

A photoreactive analogue of coelenterazine having an azido group was synthesized. The analogue showed similar chemi- and bioluminescence properties to those of the natural coelenterazine. Photolysis of the analogue in the presence of diethylamine gave a derivative azepine as the major product.
A Convenient Synthesis of Trifluoromethyl Ethers by Oxidative Desulfurization-Fluorination of Dithiocarbonates
Authors: Kanie Kiyoshi , Tanaka Yoichiro , Suzuki Kazundo , Kuroboshi Manabu , Hiyama Tamejiro
Published: September 2002

Trifluoromethyl ethers R-OCF3 are easily synthesized from the corresponding dithiocarbonates R-OCS2Me (R = aryl or primary alkyl) by a reagent system consisting of 70% HF/pyridine and an N-halo imide. When the reaction is applied to R-OCS2Me wherein R = secondary alkyl, tertiary alkyl, or benzylic group, fluorination leading to the corresponding alkyl fluorides R-F is achieved, whereas a combination of 50% HF/pyridine and N-bromosuccinimide affords the corresponding trifluoromethyl ethers R-OCF3 (R = secondary).
Asymmetric Hydrosilylation of Ketones Using Trans-Chelating Chiral Peralkylbisphosphine Ligands Bearing Primary Alkyl Substituents on Phosphorus Atoms
Authors: Kuwano Ryoichi , Sawamura Masaya , Shirai Junya , Takahashi Masatoshi , Ito Yoshihiko
Published: September 2002

Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001—0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)-secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
An Efficient Method to Construct the A,B-Rings Component toward Total Syntheses of Phycocyanobilin and Its Derivative as a Photoprobe
Authors: Jayasundera Krishanthi Padmarani , Kinoshita Hideki , Inomata Katsuhiko
Published: September 2002

Total syntheses of phycocyanobilin and its derivative bearing a photoreactive group at the D-ring were accomplished by developing a new and efficient method for the construction of A,B-rings component, which consists of the Wittig-type new coupling reaction of 4-(1-methoxyethyl or 1-tosylethyl)-3-methyl-5-tosyl-1,5-dihydro-2H-pyrrol-2-one and a 2-formyl pyrrole derivative in the presence of nBu3P and a base, followed by reduction with aluminum amalgam and a subsequent acid or base treatment.
Ultrafast Energy Transfer Dynamics at Solid/Liquid Interfaces as Investigated by Photothermal Spectroscopy
Authors: Tsuyumoto Isao , Sawada Tsuguo
Published: September 2002

Recent studies on ultrafast energy transfer at solid/liquid interfaces were reviewed, focusing on our developed photothermal techniques: femtosecond transient reflectivity (fs-TR) method, femtosecond transient reflecting grating (fs-TRG) method, and picosecond surface plasmon resonance transient reflecting grating (ps-SPR-TRG) method. Firstly, Pt/auqoues electrolyte interfaces were measured using the fs-TR method. An ultrafast relaxation component of 20 fs was first observed in the Pt/HCl (aq) and Pt/H2SO4 (aq) interfaces, in which the anions (Cl- and SO42-) have strong affinity to the Pt surface. It was suggested that this is due to the scattering of non-thermalized electrons by adsorbed anions. Secondly, TiO2/KSCN (aq) interfaces were measured using the fs-TRG method. Ultrafast relaxation components (110—690 fs) were observed in the TRG signals. This marked the first observation of the contribution of nonequilibrium holes to the energy transfer at TiO2/KSCN (aq) interfaces. Thirdly, Au/NaCl (aq) interfaces were measured using ps-SPR-TRG method, focusing at both the behavior of hot electrons and thermal diffusion. The results indicated that an ultrafast energy transfer process occurs prior to the heat diffusion and this process is hindered by the adsorbed ions.
Conductive Copper Salts of 2,5-Disubstituted N,N′-Dicyanobenzoquinonediimines (DCNQIs): Structural and Physical Properties
Authors: Kato Reizo
Published: September 2002

Structural and physical properties of the Cu salts of a series of π-acceptors N,N′-dicyanobenzoquinonediimines (DCNQIs) are described. The most notable feature of this system is that 3d electrons in Cu interact with pπ electrons in DCNQI near the Fermi level. This unique feature has provided a lot of interesting solid state properties: the Mott transition triggered by the Peierls transition, the pressure-induced metal-insulator transition, the metal-insulator-metal (reentrant) transition, the three-dimensional Fermi surface, the anomalous isotope effects, the antiferromagnetic transition, the weak ferromagnetism, and the electron mass enhancement. The aim of this account is to give an overview of this unique pπ-d system.
Direct Study on the Unimolecular Decomposition of Methoxy Radicals: The Role of the Tunneling Effect
Authors: Oguchi Tatsuo , Miyoshi Akira , Koshi Mitsuo , Matsui Hiroyuki
Published: September 2002

The unimolecular decomposition of methoxy radicals, CH3O + M → CH2O + H + M (1a), has been directly studied by laser photolysis-laser-induced fluorescence method in the temperature range 610—740 K. Nearly linear pressure dependence of the first-order decay rate was observed in the investigated pressure range (100—450 Torr), and the second-order rate constants were derived for He and N2 buffer gases as: k0(He) = 2.8 × 10-9 exp (-84.3 kJ mol-1/RT) cm3 molecule-1 s-1 and k0(N2) = 4.3 × 10-9 exp (-84.1 kJ mol-1/RT) cm3 molecule-1 s-1, respectively. An RRKM calculation with a semiclassical one-dimensional tunneling treatment showed that the tunneling effect is essentially important in the present experimental conditions. The calculation indicates a non-linear pressure dependence of the rate constant even in the classical low-pressure limiting conditions, which is consistent with the experimental observations. The RRKM model (with threshold energy = 101.7 kJ mol-1) derived by the best fit to the experimental results is in good agreement with the theoretical investigations and the microcanonical rate constants measured by the stimulated emission pumping method.
Structure and Reactivity of Amphoteric Oxygen Species
Authors: Ishiguro Katsuya , Sawaki Yasuhiko
Published: September 2002

The structure and chemical properties of 1,3-dipolar peroxidic species (X+-O-O-) such as ozone (X = O), nitroso oxides or nitrenium peroxides (X = RN), carbonyl oxides or carbenium peroxides (X = R2C), and persulfoxides or sulfonium peroxides (X = R2S) have been attracting much attention from synthetic, biological, and theoretical standpoints. These active oxygen species can be classified into two types depending on whether the X+ is an enium (carbenium, nitrenium, silylenium etc.) ion or an onium (ammonium, oxonium, phosphonium, sulfonium etc.) ion, and their reactivities are quite different depending on the nature of X. The individual features as well as the overviews of structure and reactivities of these X-O-O species are reviewed. Ozone and nitroso oxides have an electrophilic character while carbonyl oxides usually act as a nucleophilic oxygen transfer agent, their reactivities being controlled by substituents. It is important to see whether or not XOO species can isomerize to the cyclic isomers. Although cyclic O3 is thermodynamically unstable, dioxiranes, the cyclic form of carbonyl oxides, have been isolated and fully characterized. It has been suggested that nitroso oxides isomerize to the cyclic form yielding the corresponding nitro compounds unimolecularly. In the case of persulfoxides (X = R2S), the dipolar structure (X+-O-O-) is important, their characteristic reaction being nucleophilic O-transfer to sulfoxides, while 3λ5-dioxaphosphirane (X = R3P) can exist only in the cyclic form, showing electrophilic reactivity. Effects of X's on structure and reactivity of these oxides were systematically examined by the density functional BLYP/6-31G* calculations. The inductive effect through σ-framework has been found to dominate the thermodynamic stabilities of carbonyl oxides, while the π-donating property of substituents governs the activation energy for the cyclization to dioxiranes.
Kinetics and Mechanism of Hexachloroplatinate(IV) Reduction by Some Neutralized α-Hydroxy Acids in a Carbonate-Hydrogencarbonate Buffer Medium
Authors: Pal Biswajit , Gupta Kalyan Kali Sen
Published: September 2002

The kinetics of hexachloroplatinate(IV) reduction by some neutralized α-hydroxy acids such as glycolic, lactic, α-hydroxyisobutyric, mandelic, atrolactic, and benzilic acids in a carbonate-hydrogencarbonate buffer medium have been investigated. Platinum(IV) is reduced by the substrates to platinum(II) in a one-step two-electron process, whereas the substrates are oxidized to give formaldehyde, acetaldehyde, acetone, benzaldehyde, acetophenone, and benzophenone for the respective reactions. The pseudo-first-order rate constant is independent of the initial [platinum(IV)] as well as [OH-]. The reaction rate increases with increasing [substrate], but decreases with increasing chloride concentration. The reactions obey the following rate expression:

−d[PtIV]t/dt=(kKe[A−][PtIV]t )/([Cl−]+Ke[A−])·

The reactions proceed through an initial 1 : 1 complex formation between the reactants, followed by decomposition of the complex to give the respective reaction products via C-C bond cleavage. The reactivity of the α-hydroxycarboxylate towards Pt(IV) are as follows: atrolactic acid > mandelic acid > benzilic acid > α–hydroxyisobutyric acid > lactic acid > glycolic acid. Thermodynamic parameters for the decomposition step have been evaluated. The mechanism of the reactions is discussed.
Inhibiting Effects of Group 6 Oxo-Anions on the Pitting Corrosion of Tin in Citrate-Chloride Solution
Authors: Assaf Fawzi Hassan
Published: September 2002

The effect of chloride ions on both anodic dissolution and pitting corrosion of tin metal in the aerated equimolar solutions 0.1 M (1 M = 1 mol dm-3) citrate-chlorid-oxo-anions (CrO42-, WO42-, and MoO42-) has been investigated. Different techniques were used, such as potentiodynamic, potentiostatic polarization, electrochemical impedance spectroscopy techniques. These were complemented by surface examination using scanning electron microscopy. Lower current values in the presence of equimolar (0.1 M) citrate-oxo-anions with addition of Cl- in various concentrations were observed, compared with those obtained in the oxo-anion free solutions. Thus, these oxo-anions might create a certain impediment or barrier to the attack of the aggressive Cl- on the metal surface. However, the addition of the studied anions at lower concentrations (10-3 and 10-2 M) in 0.1 mol dm-3 citrate-chloride, enhanced the active metal dissolution and passivity break down of tin. Retardation to a considerable extent was observed, however, at higher concentrations (5×10-2 and 10-1 M). All measurements using the different techniques, under the same conditions, confirmed that the order of reduced aggressiveness of Cl- was CrO42- > WO42- > MoO42-. This indicates that CrO42- remains the best inhibitor to prevent the pitting corrosion, probably through its ability to repair defects in the oxide film.
Production and Mass-Spectroscopic Characterization of Multiple Metal-Rich Alkali Halide Ion Clusters: Novel Structures and Properties
Authors: Sugai Toshiki , Shinohara Hisanori
Published: September 2002

Multiple metal-rich ion alkali halide clusters from solid crystals of NaF and CsI have been produced and characterized for the first time by a newly developed high-pressure laser-vaporization cluster source. The observed positive metal-rich clusters are NanFm+ (n ≈ 40, n-m = 1—9) and CsnIm+ (n ≈ 60, n-m = 0—5), which have enhanced intensities at n = 14, being independent of m, indicating the existence of multiple excess electrons. For negative clusters, NanFm- (n ≈ 40, n-m = -1—10) and CsnIm- (n ≈ 60, n-m = -2—3) have been observed. The NaF metal-rich negative clusters show two types of distinct magic numbers at n-m = 7 ((NaF)mNa7-) and n = 14 (Na14F13-x-, x = 0—4). The former and latter magic-number ions suggest the existence of a negative core ion of Na7- and a cubic 3×3×3 structure with multiple excess electrons, respectively. The present high-pressure laser-vaporization cluster source is suitable to produce these unstable clusters with a unique stoichiometry.
Studies on Photochemical Reactivities of 2-(Alkylcarbamoyl)quinolines
Authors: Ono Isao , Ikegami Tetsuo , Inayoshi Tomoko
Published: September 2002

The photochemistry of three types of 2-(alklylcarbamoyl)quinolines was studied. The illumination of 2-(diethylcarbamoyl)quinolines (1a, 1b, and 1c) afforded 2-(2-ethylaminopropionyl)quinolines (3a, 3b, and 3c) with a small amount of five-membered cyclic products, 1H-pyrrolo[3,4-b]quinolin-3(2H)-ones (4a, 4b, and 4c), both of which were formed via Type-II hydrogen-atom abstraction from the T1 state. 2-(Ethylcarbamoyl)quinoline (1d) did not undertake any photochemical change. The photochemical inactivity of 1d could be attributed to the unfavorable orientation of its carbamoyl substituent for intramolecular hydrogen-atom abstraction by a ring nitrogen. The illumination of 2-(alkylcarbamoyl)-3-methyl quinolines (2a and 2b) afforded 2-(N-acetyl-N-alkylcarbamoyl)-3-methyl quinolines (5a and 5b), which were suggested to be formed by the atmospheric oxidation of an unstable photoproduct formed via the S1 state.
Electrochemical Preparation of Poly(3-thiopheneacetic acid) and Its n-Type Semiconductor Property
Authors: Hara Kohjiro , Sayama Kazuhiro , Arakawa Hironori
Published: September 2002

3-Thiopheneacetic acid (3TA) was electrochemically oxidized and polymerized on indium tin oxide (ITO) electrodes in a 0.05 mol dm-3 tetrabutylammonium perchlorate (TBAP) acetonitrile solution; also, the photoelectrochemical properties of the resulting poly(3-thiopheneacetic acid) (P3TA) were studied. The film showed n-type semiconductor properties, although anion-doped conducting polymer prepared by electrochemical oxidation is generally of the p-type. An anodic photocurrent due to oxygen evolution from water was observed under white-light irradiation in a 0.1 mol dm-3 Na2SO4 aqueous solution. The anodic photocurrent density at 1.9 V vs. Ag/AgCl was 1.1 mA cm-2 and the flat-band potential of P3TA, estimated from the onset of an anodic photocurrent, was -0.1 V vs. Ag/AgCl. The band gap of P3TA was 2.4 eV, obtained from an hν vs. (hν PC)1/2 plot.
Absorption Spectra of C60-Excited States in Various Solvents: Their Dependence on the Ionization Potential of Solvent Molecules
Authors: Suzuki Isao , Tsuboi Yasuyuki , Miyasaka Hiroshi , Itaya Akira
Published: September 2002

Using a picosecond laser photolysis system, the absorption spectra of excited states of C60 in twelve solvents were measured in the 590—1190 nm wavelength range. The absorption spectra observed immediately after a 532 nm picosecond laser excitation and those in the late-time region depended upon the solvents. In particular, the former dependence was much larger than the latter one. Their spectral shapes did not correlate with either dielectric constant of the solvents or their refractive index, but with their ionization potential (Ip). The early-gated absorption spectra of C60 in solvents with a small Ip were extraordinary broad compared with those in solvents with a large Ip. In addition, the absorption changed to those observed in the late-time region both with a decay time constant of 1.2±0.05 ns and with keeping the isosbestic points. This time constant was the same as the lifetime of the C60-singlet excited state (1C60*) reported previously, and the presence of the isosbestic points was also the same as that observed during spectral evolution from Sn←S1 absorption of C60 to its Tn←T1 one. Combining the results of the resonance Raman spectra by Gallagher et al. with the present ones suggested that the solvent-dependent early-gated absorption spectra of the C60-excited state are ascribed to 1C60* with a distortion induced by specific interactions with solvents molecules through the donation of their π-electron density without forming obviously excited-state complexes. The transient absorption spectra observed immediately after the direct excitation of ground-state charge-transfer complexes formed between C60 and solvent molecules with a small Ip were not due to ionic species, but to 1C60*, suggesting that the photogenerated ionic species undergo a very rapid charge-recombination reaction to result in 1C60* and the ground-state solvent molecule. The absorption spectra in the late-time region, which showed a slight dependence on Ip of the solvent molecules, as aforementioned, were assigned to the Tn←T1 absorption of C60; the dependence was considered to be also ascribed to the same reason as that for 1C60*.
Ethylene Polymerization Catalyzed by Ruthenium and Iron Complexes Containing 2,6-Bis(2-oxazolin-2-yl)pyridine (Pybox) Ligand-Cocatalyst System
Authors: Nomura Kotohiro , Sidokmai Warit , Imanishi Yukio
Published: September 2002

RuX2(ethylene)(pybox) [X = Cl (1), I (2), and CF3SO3 (3); pybox = 2,6-bis[(4S)-4-isopropyl-2-oxazolin-2-yl]pyridine] complexes have exhibited moderate catalytic activity for ethylene homopolymerization and ethylene/1-hexene copolymerization in the presence of MAO. The incorporation of 1-hexene (27.2 mol%) in the resultant copolymer was confirmed by 13C NMR spectrum. The resonances corresponding to the triad sequence of HHH were negligible. A small rE·rH value of 0.32, where rE and rH are the monomer reactivity ratios of ethylene and 1-hexene, respectively, was thus obtained, indicating a significantly alternating tendency. FeCl2(pybox) (4) has also exhibited the activity for ethylene polymerization in the presence of MAO. The attempted copolymerization of ethylene with 1-hexene by 4 gave linear polyethylene without incorporating 1-hexene.
Energy Conversion from Proton Gradient to Electricity Based on Characteristic Redox Behavior of an Aqua Ruthenium Complex with a Quinone Ligand
Authors: Tsuge Kiyoshi , Kurihara Masato , Tanaka Koji
Published: September 2002

A ruthenium aqua complex having a quinone ligand, [Ru(trpy)(dbq)(H2O)](ClO4)2 (trpy = 2,2′:6′,2′′-terpyridine, dbq = 3,5-di-t-butyl-1,2-benzoquinone) ([Ru(q)(H2O)](ClO4)2) was prepared. Its electrochemical properties and electronic absorption spectra were measured in the presence of a base in acetone. The detailed analysis of those measurements revealed that the addition of a base caused not only the deprotonation but also the reduction of [Ru(q)(H2O)]2+. The redox reactions coupled with acid-base reactions were demonstrated from the large difference in redox properties of aqua and hydroxo complexes. Taking advantage of unique redox reactions induced by the acid-base equilibrium between aqua and hydroxo complexes, we have succeeded in constructing the first energy transducer which converts the proton gradient to electricity. A similar ruthenium aqua complex with a bipyridine ligand, [Ru(trpy)(bpy)(H2O)](ClO4)2, also reversibly dissociates a proton of aqua ligand. However, it has no ability to convert the proton gradient to electricity due to the lack of a suitable molecular orbital which can accommodate electrons on the electron-rich hydroxo ligand.
Rubrene Cation Radical Stabilized by Polyiodide Chains in the (Rubrene)I9 Crystal
Authors: Kameya Megumi , Naito Toshio , Inabe Tamotsu
Published: September 2002

A fused polycyclic aromatic compound, rubrene (RB), has been found to form a charge-transfer compound with iodine with the stoichiometry of RB·I9. The crystal is monoclinic, space group C2/c, a = 14.482(4), b = 16.676(8), c = 19.985(4) Å, β = 106.90(2)°, V = 4618(2) Å3, and Z = 4. In this crystal, a unique branched crank-shaped one-dimensional (I9-)∞ polyiodide chain is formed. RB is surrounded by the polyiodide, and its cation radical state, which is unstable under normal conditions, is stabilized. The formation of the RB cation radical has been confirmed by IR, VIS-NIR, and EPR spectroscopies. The magnetic susceptibility measurement has indicated the existence of superexchange interactions through the polyiodide.
Simultaneous Determination of Lanthanoids and Yttrium in Rock Reference Samples by Inductively Coupled Plasma-Mass Spectrometry Coupled with Cation Exchange Pretreatment
Authors: Lee Kyue-Hyung , Oshima Mitsuko , Takayanagi Toshio , Motomizu Shoji
Published: September 2002

The amounts of lanthanoids (Ln) and yttrium (Y) in eleven GSJ (Geological Survey of Japan, Tsukuba) rock reference materials have been determined. Fundamental studies on trace analysis of rock samples by inductively coupled plasma-mass spectrometry (ICP-MS) were conducted to obtain accurate contents of rare earth elements. The samples were dissolved using a conventional acid digestion technique, then treated on a cation exchange column for the removal of matrix components. Isobaric interferences from metal oxide ions were corrected based on the results of the experimentally obtained percentages of the metal oxide formation. A long-term stability test of the ICP-MS instrument with multielement standard solutions proved that all data obtained at concentration ranges from 0.01 to 10 ng ml-1 were reproducible, the drift of signals were less and the relative standard deviation (RSD) was within ±2.5%. The recoveries of Ln and Y from the cation exchange column were found to be (100±4)%. The results obtained for an igneous rock series showed good agreement with the recommended values given by GSJ, and their chondrite-normalized patterns were smooth.
Effect of the Hydrophobic Anion of Picrate on the Extraction of Europium(III) with Diamide
Authors: Naganawa Hirochika , Suzuki Hideya , Tachimori Shoichi , Nasu Akinobu , Sekine Tatsuya
Published: September 2002

The effect of the picrate (pic-) ion on Eu(III) extraction with a diamide (da) from aqueous nitric acid (0.001—0.1 mol dm-3) solutions into benzene was clarified on the basis of the stoichiometry of ion-pair extractions by analyzing the distribution data of Eu(III) and picric acid (Hpic). The extraction of Eu(III) with da was extremely enhanced by adding a hydrophobic anion of pic- to the liquid-liquid system. From analyses of the distribution data of Eu(III) and Hpic, it was concluded that the effect of the hydrophobic anion was caused by the extraction of a single ion-pair of [Eu(da)2](pic)3. The nitrate ion had no relation with the cooperative effect of da and pic-, i.e., the extraction of [Eu(da)2](NO3)3, [Eu(da)2](pic)(NO3)2, and [Eu(da)2](pic)2(NO3) was practically negligible as against the [Eu(da)2](pic)3 extraction. The cooperative effect was reduced by an increase in the aqueous HNO3 concentration, which was induced by a decrease in the pic- concentration in the aqueous phase; the dissociation of Hpic into pic- ion was suppressed by an increase in the H+ concentration, and a part of molecular Hpic was extracted into the organic phase. Furthermore, the extraction of Hpic was also enhanced by an increase in the da concentration in the organic phase, which also induced a decrease in the aqueous pic- concentration. This was found to be due to the formation of a 1 : 1 complex between da and Hpic. However, the extraction of the complexes between da and HNO3 was negligible in the acid concentration range in the present study.