bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Properties of Head-to-head, Head-to-tail, and Tail-to-tail Orientational Isomers of Extended Dihexylbithiophene–Octaethylporphyrin System [OEP–(DHBT)n–OEP] Connected with 1,3-Butadiyne Linkages
Authors: Higuchi Hiroyuki , Ishikura Takashi , Mori Kazumine , Takayama Yukari , Yamamoto Koji , Tani Keita , Miyabayashi Keiko , Miyake Mikio
Published: September 2002

An extended π-electronic conjugation system of dihexylbithiophene–octaethylporphyrin [OEP–(DHBT)n–OEP; n = 1–5], all the chromophores in which are connected with the linkage of 1,3-butadiyne (diacetylene), was synthesized by an oxidative cross-coupling reaction of the corresponding terminal acetylenes. Absorption spectral and electrochemical properties of the OEP–(DHBT)n–OEP system were examined. The results proved that the orientation of two 3-hexylthiophene (3HTh) rings of DHBT plays an important role in electronic communications between the two terminal OEP rings.
Stacked Porphyrin Arrays from Hydrogen-Bonded Porphyrin–Resorcinol 1D Chains
Authors: Tanaka Toshihiro , Endo Ken , Aoyama Yasuhiro
Published: September 2002

The Ni(II) complex of monoresorcinol derivative of a sterically unhindered tetraalkylporphyrin (3) affords adducts 3•(methanol) and 3•1.5(acetophenone). In the crystals, porphyrin 3 forms hydrogen-bonded (O–H···O–H) polyresorcinol chains with the porphyrin residues sticking out of the chains. The chains are self-assembled in such a manner as to give closely stacked interchain porphyrin columns, while the guest molecules are either firmly bound to the hydrogen-bonding sites (in the case of methanol) or incorporated in the channels running in parallel with the porphyrin stacks (in the case of acetophenone). The formation of such a stacked porphyrin array is not observed when the guest is changed to 4-heptanone or when the porphyrin is changed to a sterically hindered one 4 or 5 with full substitution at the meso- or the β-positions. The mode of interchain porphyrin stacking is discussed in light of the crystal structures of adducts 3•(4-heptanone), 4•pyridine, and 5•(2-nonanone).
Mechanistic Considerations on the Oxime–Nitrone Isomerization and Intramolecular Cycloaddition Reaction of 3-(Alk-2-enylamino)propionaldehyde Oximes
Authors: Noguchi Michihiko , Okada Hirofumi , Tanaka Masayuki , Matsumoto Satoshi , Kakehi Akikazu , Yamamoto Hidetoshi
Published: September 2002

3-(Alk-2-enylamino)- and 3-(acryloylamino)-2,2-dimethylpropionaldehyde oximes underwent thermally induced 1,3-dipolar cycloaddition under mild conditions, leading to perhydroisoxazolo[4,3-c]pyridine derivatives. The features of the intramolecular oxime–olefin cycloaddition in this system and the roles of the geminal methyl groups at the 2-position and the alkenylamino nitrogen in the oxime–nitrone isomerization process are discussed based on kinetic studies.
Kinetic Analysis of the Temperature Dependence of the Template-Directed Formation of Oligoguanylate from the 5′-Phosphorimidazolide of Guanosine on a Poly(C) Template with Zn2+
Authors: Kawamura Kunio , Umehara Masatosi
Published: September 2002

A kinetic study of the temperature dependence of the template-directed formation of oligoguanylate (oligo(G)) on polycytidylic acid (poly(C)) from the 5′-phosphorimidazolide of guanosine (ImpG) has been carried out in the presence of Zn2+ at 40–80 °C. It is surprising that a large amount of oligo(G) was formed at 40–60 °C and a small amount of oligo(G) was detected even at 80 °C. The rate constants of the template-directed formation of oligo(G) were determined at 40–60 °C, and the same trend, the rate constants increase with the chain length, was observed as that at lower temperatures. Besides, second-order rate plots of the hydrolyses of ImpG and oligo(G) were consistent with pseudo-second-order processes in the presence of 0.04 M Zn2+. The apparent activation energy determined from the Arrhenius plots decreases in the order hydrolysis of oligo(G) > formation of 4-mer ≈ formation of 3-mer ≈ hydrolysis of ImpG > formation of 2-mer. The kinetic analysis and computer simulations demonstrate the importance of the rate of 2-mer formation to determine the efficiency of the oligo(G) formation.
Preparation and Lectin Binding Property of Chitosan–Carbohydrate Conjugates
Authors: Sashiwa Hitoshi , Shigemasa Yoshihiro , Roy Renè
Published: September 2002

Chitosan–sialic acid conjugates were prepared using p-formylphenyl α-sialoside by reductive N-alkylation. The degree of substitution (DS) of conjugates could be controlled from 0.06 to 0.53 by the amount of sialoside. With the use of p-isothiocyanatophenyl α-sialoside, chitosan–sialic acid conjugates were also prepared with excellent efficiency. Chitosan–melibiose conjugates having α-galactosyl epitope were also prepared by reductive N-alkylation. These conjugates were transformed into water-soluble forms by N-succinylation and their protein binding property was tested using wheat germ agglutinin (WGA) or Griffonia simplicifolia (GSI-B4) lectin. Strong immunodiffusion bands were observed in all of conjugates, thus demonstrating the specific binding of epitope in conjugate to each lectins.
Kinetic Investigation on the Hydrolysis of Aryl(fluoro)(phenyl)-λ6-sulfanenitriles
Authors: Dong Tiaoling , Fujii Takayoshi , Murotani Satoro , Dai Huagang , Ono Shin , Morita Hiroyuki , Shimasaki Choichiro , Yoshimura Toshiaki
Published: September 2002

A kinetic investigation on the hydrolysis of aryl(fluoro)(phenyl)-λ6-sulfanenitriles was carried out in some aqueous and mixed aqueous-organic solutions. The pH-rate profiles showed that the hydrolysis consists of pH-independent, acid-catalyzed and base-catalyzed reactions. The neutral hydrolysis of fluoro-λ6-sulfanenitriles was found to proceed via an SN1 or an S-nitrilosulfonium cation-like transition state, which is characterized by a large negative Hammett ρ-value (ρ = −1.76 in water; −1.85 in CH3CN/H2O(1/4, v/v); −2.35 in TFE/H2O (1/1, v/v)), relatively large m-values (ca. 0.83 for fluoro(diphenyl)-λ6-sulfanenitrile; ca. 0.82 for fluoro(p-nitrophenyl)(phenyl)-λ6-sulfanenitrile against the solvent ionizing power YOTs-values in acetonitrile–water), a common ion effect in TFE/H2O, and a small salt effect. The large negative activation entropies (−60 – −101 J K−1 mol−1) were presumed to be due to strong solvation of F− with H2O in the reaction systems. The ease of ion dissociation of the S–F bond was examined by a theoretical calculation in a DFT method, to show that the SN1-like transition state is caused by a facile tendency of dissociation of the S–F bond of fluoro-λ6-sulfanenitriles. The acid-catalyzed hydrolysis was found to proceed via a more cation-like transition state involving a concerted proton transfer to the fluorine atom and breaking of the sulfur-fluorine bond in the λ6-sulfanenitrile. The alkaline hydrolysis probably takes place via an SN2 mechanism.
Asymmetric Bis(alkoxycarbonylation) Reaction of Terminal Olefins Catalyzed by Palladium in the Presence of Copper(I) Triflate and a Chiral Bioxazoline Ligand
Authors: Takeuchi Susumu , Ukaji Yutaka , Inomata Katsuhiko
Published: September 2002

A palladium-catalyzed asymmetric bis(alkoxycarbonylation) reaction of terminal olefins in the presence of copper(I) triflate was achieved by using a chiral bioxazoline ligand, (4S,4′S)-4,4′-dibenzyl-4,4′,5,5′-tetrahydro-2,2′-bioxazole, under normal pressure of carbon monoxide and oxygen at 25 °C to give the corresponding optically active mono-substituted succinates with enantioselectivity up to 66% ee.
Conformational Preference of β-Aryldehydroalanine. Solid-State Conformation of Tripeptide Possessing a (Z)-β-(1-Pyrenyl)dehydroalanine Residue in the Second Position
Authors: Inai Yoshihito , Oshikawa Tatsuo , Yamashita Mitsuji , Hirabayashi Tadamichi , Kurokawa Yuji
Published: September 2002

In this paper we attempted to reveal how a large β-substituent (pyrenyl group) of dehydroresidue affects the structural and conformational preferences of (Z)-β-substituted α,α-dehydroalanine. An X-ray crystallographic analysis was carried out for Boc–l-Ala–ΔZPyr–l-Val–OMe (Boc = t-butyloxycarbonyl; OMe = methoxy) possessing a novel (Z)-β-(1-pyrenyl)dehydroalanine (ΔZPyr) residue. Single crystals were obtained by slow evaporation from an ethanol solution in the monoclinic space group P21. The bond lengths and bond angles of the ΔZPyr residue were essentially similar to other β-substituted dehydroalanines. The tripeptide took a type II β-turn conformation involving an intramolecular hydrogen bond between CO(Boc) and NH(Val), like small peptides possessing a (Z)-β-(1-naphthyl)dehydroalanine or a (Z)-β-phenyldehydroalanine residue. The similarity between ΔZPyr and other dehydroalanines in structural property and conformational preference should be responsible for the non-planarity of the ΔZPyr residue to give an extremely high energy in the planar orientation of the pyrenyl group relative to the Cα=Cβ-Cγ plane; the non-planarity should weaken the π-conjugation effect of the pyrenyl group on the structural property and conformational preference of the ΔZPyr residue. The pyrenyl rings were packed in a partially overlapped face-to-face orientation with the shortest center-to-center distance of 5.96 Å. The CD spectrum of a KBr disk prepared from the crystal showed strong excitonic interactions between pyrenyl groups, reflecting a regular arrangement of the pyrenyl groups in the crystal structure.
Synthesis of 2H-Chromenes through the Reduction of Chromones with 9-BBN
Authors: Eguchi Tetsuya , Hoshino Yukio
Published: September 2002

Chromones were regioselectively reduced to 2H-1-benzopyrans through the 1,2-addition of 9-borabicyclo[3.3.1]nonane. Although transition-metal complexes did not have a catalytic effect on the reaction, only by using palladium(II) chloride, could both 2H-1-benzopyran and dihydro-1-benzopyran be obtained to a similar extent. Also, the reduction of chromone using other organoboranes led not to 2H-1-benzopyran, but rather to chromanone through the reduction of only an olefin moiety.
Synthesis, Crystal Structure, and Some Spectrochemical Properties of S-Bridged Hexanuclear Zinc(II) Complex with 2-Aminoethanethiolate: Formation of Zn3S3- and Zn4S4-Cyclic Cores
Authors: Yamada Yasunori , Miyashita Yoshitaro , Fujisawa Kiyoshi , Okamoto Ken-ichi
Published: September 2002

The reaction of [Zn(aet)2] (aet = 2-aminoethanethiolate) with Zn(ClO4)2•6H2O in aqueous acetonitrile gave an S-bridged hexanuclear complex, [{Zn(aet)}4{Zn(aet)2}2]4+, accompanied by the ligand-transfer of aet from [Zn(aet)2] units to Zn2+ ions. In the hexanuclear complex, all of the Zn and S atoms are included in the Zn3S3- and/or Zn4S4-cyclic structures.
Intramolecular Cyclizations of o-Substituted β,β-Difluorostyrenes: Synthesis of 3-Fluorinated Isochromenes and Isothiochromenes
Authors: Wada Yukinori , Ichikawa Junji , Katsume Tadayuki , Nohiro Tomoko , Okauchi Tatsuo , Minami Toru
Published: September 2002

β,β-Difluorostyrenes bearing an oxygen (OH) or a sulfur (SH, SCOCH3) nucleophile linked by a methylene unit to the ortho carbon are prepared from 2,2,2-trifluoroethyl p-toluenesulfonate via the in situ generation of 2,2-difluorovinylboranes and their palladium-catalyzed cross-coupling reaction with aryl iodides. These styrene derivatives readily undergo intramolecular nucleophilic substitution of the oxygen and sulfur with loss of fluorine under basic conditions, leading to 3-fluoroisochromenes and 3-fluoroisothiochromenes in high yields.
Synthesis and Properties of a Series of the Longest Oligothiophenes up to the 48-mer
Authors: Sumi Naoto , Nakanishi Hidetaka , Ueno Shinpei , Takimiya Kazuo , Aso Yoshio , Otsubo Tetsuo
Published: September 2002

A series of the longest class of oligothiophenes extended at intervals of seven thiophene units from the 6-mer up to the 48-mer has been synthesized by a combination of the random Eglinton coupling reaction of mono- and di-ethynylsexithiophenes and a subsequent sodium sulfide-induced cyclization reaction of the resulting oligo(sexithienylene-diethynylene)s. Their structures were well characterized by MALDI-TOF MS and 1H NMR spectroscopy. The molecular weights of the oligothiophenes and oligo(sexithienylene-diethynylene)s, measured by gel-permeation liquid chromatography using the polystyrene standard, are nearly double the actual ones, indicating that they keep highly rigid rod-type shapes. According to a molecular model, the molecular lengths of the longest oligothiophene 48-mer and the longest oligo(sexithienylene-diethynylene) reach approximately 18.6 nm and 25.0 nm, respectively. In the electronic absorption and emission spectra, the π–π* transitions of the oligothiophenes demonstrate progressive red shifts with increasing chain length up to the 20-mer. In the cyclic voltammograms, furthermore, the first oxidation potentials tend to continue negative shifts up to the 34-mer. In accordance with these spectral changes, the doped conductivities steadily increase and approach that of a structurally related polymer.
Syntheses of Chiral Solid Catalysts Using Menthol and Application to the Asymmetric Diels–Alder Reaction
Authors: Nagasawa Tomomi , Kudo Nozomi , Hida Yoshiyuki , Ito Kazuaki , Ohba Yoshihiro
Published: September 2002

A chiral solid catalyst as a heterogeneous Lewis acid prepared from trimethylaluminum, menthol and tetrachlorobisphenol A has been found to promote the asymmetric Diels–Alder reaction of 2-methyl-2-propenal with cyclopentadiene and is a reuseable catalyst.
Monodentate, Didentate, and Tridentate Ligation of a Schiff-Base Ligand in a Tetranuclear Zinc(II) Complex
Authors: Mikuriya Masahiro , Ikemi Shinichiro , Lim Jong-Wan
Published: September 2002

A tetranuclear zinc(II) complex with 2,6-bis(salicylideneaminomethyl)-4-methylphenol (H3L), [Zn4(L)2(pz)2]•2CH3CN (Hpz = pyrazole), was synthesized and characterized by 1H NMR spectroscopy and a single-crystal X-ray diffraction method. Each Schiff-base L3- acts as a monodentate, a didentate, and a tridentate ligand for four zinc atoms to form a Z-shaped tetranuclear structure.
A Novel Photosensitive Silicone Ladder Polymer: Synthesis, Photochemical, and Thermal Characteristics
Authors: Yasuda Naoki , Yamamoto Shigeyuki , Adachi Hiroshi , Nagae Suguru , Wada Yuji , Yanagida Shozo
Published: September 2002

A negative working photosensitive silicone ladder polymer (PVSQ) based on polyphenylsilsesquioxane with vinyl groups as a reactive substituents in the side chain, and 2,6-bis(azidobenzylidene)-4-methylcyclohexanone (BA) as a photocrosslinker, has been developed. The monodisperse PVSQ was synthesized by co-polymerization of trichlorophenylsilane and trichloro(vinyl)silane with potassium hydroxide in isobutyl methyl ketone. The PVSQ film showed excellent transparency above 280 nm and high solubility in organic solvents. The photosensitive PVSQ containing 3 wt% of BA showed the sensitivity of 40 mJ cm−2 when it was exposed to 365 nm light (i-line) followed by development with a mixture solution of anisole and xylene at 25 °C. The photosensitive PVSQ film also showed high thermal stability (decomposition temperature: 520 °C) and low dielectric constant (3.2/1 MHz), demonstrating a high potential for application to LSI production.
Convenient Route to Both Enantiomerically Pure Forms of trans-4,5-Dihydroxy-2-cyclopenten-1-one: Efficient Synthesis of the Neocarzinostatin Chromophore Core
Authors: Toyama Koji , Iguchi Satoru , Sakazaki Hayato , Oishi Tohru , Hirama Masahiro
Published: September 2002

An enantioselective synthesis of an epoxybicyclo[7.3.0]dodecenediyne core system of the neocarzinostatin chromophore has been achieved via intramolecular acetylide addition and palladium-mediated coupling of iodocyclopentene 5 with alkyne 6. The key cyclopentene moiety, trans-4,5-dihydroxy-2-cyclopenten-1-one 7, was conveniently prepared in both enantiomerically pure forms via enzymatic desymmetrization of meso-3,4,5-trans,trans-trihydroxycyclopentene derivatives.
Design, Synthesis, Structure, and Spectroscopic and Electrochemical Properties of Phthalocyanines
Authors: Kobayashi Nagao
Published: September 2002

The synthesis and spectroscopic and electrochemical properties of crown-ether substituted metallophthalocyanines (MCRPcs), optically active phthalocyanines (Pcs), subphthalocyanines (SubPcs), low symmetrical Pcs, ring-expanded Pcs, and novel oligomers of Pcs studied mainly by the author over the last 20 years have been reviewed, together with the electrocatalytic reduction of dioxygen using water soluble Pcs. MCRPcs form, on addition of certain kinds of cation, cofacial dimers through a two-step three-stage process. SubPcs react with isoindolediimines to produce mono-substituted Pc and Pc analogues. Optically active Pcs have been prepared to show the beauty and usefulness of circular dichroism spectroscopy. Ring-expanded or -shrunk and low symmetrical Pc analogues have helped in exploiting the relationship between size, symmetry, and spectroscopic and electrochemical properties of large aromatic molecules. Molecular orbital calculations on these compounds have succeeded in reproducing many of the experimental properties. New types of cofacial and planar dimers have been prepared, occasionally with a new concept. Water-soluble iron and cobalt Pcs electrocatalyze the reduction of dioxygen. When a four-electron reduction was attained, the reduction proceeded via hydrogen peroxide, and could be explained by a mechanism of electrochemical catalyst regeneration. The results for these compounds are occasionally compared with those of porphyrin systems.
Resonance Raman Spectra of Cytochrome c Oxidase in Whole Mitochondria
Authors: Takahashi Toshinari , Ogura Takashi
Published: September 2002

Resonance Raman spectra of cytochrome c oxidase in intact whole mitochondria were selectively observed. The Raman bands observed at 576, 517, and 369 cm-1 for the carbon monoxide-bound state were assigned to the δFe–C–O, νFe–CO, and δFe–C–O modes, respectively, of heme a3-CO complex based on the 13C18O isotopic frequency shifts. These frequencies are essentially the same as those observed for solubilized cytochrome c oxidase, which implies that the environmental structure of the dioxygen reducing site in the solubilized state is not very much altered. It is likely that the dioxygen reducing reaction studied so far for solubilized enzyme is also valid for intact whole mitochondria.
Optimizing Vibrational Population Transfer at Surfaces through Infrared Excitation
Authors: Bonn Mischa , Wolf Martin
Published: September 2002

We present an experimental and theoretical study of vibrational excitation of the C–O stretch vibration of carbon monoxide adsorbed on a ruthenium Ru(001) surface with ultrashort femtosecond infrared (IR) laser pulses. Broadband IR excitation leads to the transfer of a significant fraction of the CO molecules to their first (∼15%) and second (∼5%) vibrationally excited states. We reproduce the observed excited state spectra by solving the three-level Bloch equations and discuss possibilities to optimize the degree of localized vibrational excitation of a specific bond of surface molecules through IR excitation by tuning the pulse duration and central frequency.
Developing Vibrational Infrared Near Field Spectroscopy to Characterize Polymer Structures on Surfaces: Identification and Reduction of Topographic Coupling Artifacts
Authors: Akhremitchev Boris B , Walker Gilbert C
Published: September 2002

We report efforts to develop infrared near field microscopy for the characterization of polymer surfaces. The new near field microscope is adapted from an atomic force microscope with custom optics to create a high spatial resolution imaging platform. In addition, we report developments of analytical and finite difference approaches relating the rough sample/light interaction, the resultant near field optical signal, and the chemical structure of the sample. Simulations of the role of a topographic coupling artifact of the observed near field signal, and a method to overcome that artifact are presented.
Time-Resolved Infrared Absorption Studies of Surface OH Groups on TiO2 Particles Irradiated by UV Pulses
Authors: Yamakata Akira , Ishibashi Taka-aki , Onishi Hiroshi
Published: September 2002

The shift of vibrational frequency of surface OH groups on TiO2 particles induced by UV pulse irradiation has been studied by time-resolved IR absorption spectroscopy. By the UV irradiation of the TiO2 particles, the absorption intensity at 3696 cm-1 was decreased and that at 3654 cm-1 was increased. These changes were gradually recovered on a millisecond time scale. The transient changes were interpreted by a small (< 0.1 cm-1) shift of a ν(O–H) band at 3677 cm-1. The temperature jump triggered by the UV pulse caused the shift.
Fluorescence from the Highly Excited States and Vibrational Energy Relaxation in Directly Linked Porphyrin Arrays
Authors: Song Nam Woong , Cho Hyun Sun , Yoon Min-Chul , Jeoung Sae Chae , Yoshida Naoya , Osuka Atsuhiro , Kim Dongho
Published: September 2002

The fluorescence decay profiles of zinc(II) 5,15-di-(3,5-di-tert-butylphenyl) porphyrin monomer (Z1) and its meso, meso-linked dimer (Z2), trimer (Z3) and tetramer (Z4) were investigated by using the fluorescence upconversion technique. Fluorescence from the S2 state in Z1 was observed to decay with the time constant of 1.2 ps at 460 nm. Corresponding fluorescence rise due to the internal conversion from S2 to S1 states in Z1 was also observed at 635 nm with the time constant of 1.5 ps. The S2 state lifetime of Z2 was largely reduced (90 fs) due to the participation of exciton-split Soret band as a ladder type deactivation channel. Fluorescence decay profile and time-resolved spectra in 530 – 600 nm region revealed that the intramolecular vibrational relaxation (IVR) rate is retarded as the excess vibrational energy decreases in the porphyrin arrays as well as in Z1. The IVR rate was increased from Z1 to Z2 probably due to the additional normal modes related with the inter-unit bond as an efficient internal bath. Furthermore it was observed that a bottleneck in the bath modes limits the increase of IVR rate with the increased number of internal modes in the arrays over Z2 molecule.
Time-Resolved Charge Transfer in “Push-Pull” Stilbenes
Authors: Oberlé Jean , Jonusauskas Gediminas , Abraham Emmanuel , Lapouyade René , Rullière Claude
Published: September 2002

Intramolecular Charge Transfer (ICT) processes of 4-dimethylamino-4′-nitrostilbene (DNS) in solution are studied by pump-probe absorption spectroscopy with a 100 fs time resolution. The results are compared to transient CARS experiments. Pump-probe results confirm the formation of a radiative ICT state in low polar solvents. In a highly polar solvent (acetonitrile), the formation of a short-lived non-radiative ICT state is observed for the first time. CARS experiments support structural changes associated to ICT processes in highly polar solvents.
Ultrafast Intramolecular Electron Transfer Studied by Picosecond and Stationary Raman Spectroscopy
Authors: Werncke Wolfgang , Wachsmann-Hogiu, Sebastian , Dreyer Jens , Vodchits Alexander Ivanovich , Elsaesser Thomas
Published: September 2002

Ultrafast photoinduced intramolecular electron transfer (ET) of betaine-30 (B-30) is studied in different solvents by resonance Raman spectroscopy. We apply stationary and picosecond time-resolved Raman techniques combined with ab initio Hartree–Fock calculations. Picosecond Raman spectroscopy of the first excited singlet state allows to monitor changes of vibrational frequencies due to ET. From the intense Raman lines of the stationary resonance Raman spectra we predict relevant geometric changes of B-30 due to ET which are confirmed by calculations of geometrical changes between the ground and excited electronic states of B-30. The torsional motion between the phenolate and the pyridinium rings as well as nitrogen pyramidalization play an essential role in electron transfer. Vibrational modes accepting the bulk of excess energy after back-electron transfer are identified by time-resolved anti-Stokes resonance Raman spectroscopy. In particular, the highest-frequency mode of the resonance Raman spectrum exhibiting a large Franck–Condon factor is most effective in accepting energy. Mode specific excitation of B-30 after back-electron transfer results in nonequilibrium vibrational populations within the first few picoseconds and subsequent quasi-equilibrium populations of hot Raman active modes. The observed vibrational kinetics can be qualitatively understood by a solvent dependent interplay of direct vibrational excitation and intramolecular vibrational energy redistribution.
Excited State Structure and Dynamics of p-Benzoquinone and Bromanil from Time-Resolved Resonance Raman Spectra and Simulation
Authors: Puranik Mrinalini , Umapathy Siva
Published: September 2002

p-Benzoquinone and its halogen substituted derivatives are known to have differing reactivities in the triplet excited state. While bromanil catalyzes the reduction of octaethylporphyrin most efficiently among the halogenated p-benzoquinones, the reaction does not take place in presence of the unsubstituted p-benzoquinone (T. Nakano and Y. Mori, Bull. Chem. Soc. Jpn.,  67, 2627 (1994)). Understanding of such differences requires a detailed knowledge of the triplet state structures, normal mode compositions and excited state dynamics. In this paper, we apply a recently presented scheme (M. Puranik, S. Umapathy, J. G. Snijders, and J. Chandrasekhar, J. Chem. Phys.,  115, 6106 (2001)) that combines parameters from experiment and computation in a wave packet dynamics simulation to the triplet states of p-benzoquinone and bromanil. The absorption and resonance Raman spectra of both the molecules have been simulated. The normal mode compositions and mode specific excited state displacements have been presented and compared. Time-dependent evolution of the absorption and Raman overlaps for all the observed modes has been discussed in detail. In p-benzoquinone, the initial dynamics is along the C=C stretching and C–H bending modes whereas in bromanil nearly equal displacements are observed along all the stretching coordinates.
Ultrafast Excited State Relaxation of the Chromophore of the Green Fluorescent Protein
Authors: Litvinenko Konstantin Leonid , Webber Naomi Marica , Meech Stephen Roy
Published: September 2002

Excited state relaxation in a synthetic analogue of the green fluorescent protein chromophore is investigated. Evidence is presented for rapid ground state recovery through internal conversion, with a minor channel populating a long lived bottleneck state. The rate constant for internal conversion is observed to be weakly dependent on medium viscosity over a wide range, but appears to be thermally activated. The rate constant for internal conversion does however depend on the charge of the chromophore. Some speculations on the nature of the protein chromophore interactions which might suppress this radiationless channel are made.
Real-Time Spectroscopy of the Excited-State Excitons in Porphyrin J-Aggregates
Authors: Kano Hideaki , Kobayashi Takayoshi
Published: September 2002

The excited exciton (S2-exciton originating from the second-excited state of the molecules) was studied by real-time spectroscopy with 30-fs pulses. The ultrafast dynamics due to the S2–S1 internal conversion process were clearly observed in the pump–probe signal. The signal was modulated by the coherent molecular vibrations with 241 ± 4 cm-1 and 319 ± 4 cm-1 frequencies. The phase of the oscillation indicates that not only the ground state but also the excited state contribute to the oscillatory signal. The excited-state wave-packet motion was explained by dynamic intensity borrowing mechanism from the S2 S0-transitions to the S1 S0-transitions.
Effect of Pump and Probe Light Field on Picosecond Time-Resolved Resonance Raman Spectra of S1 trans-Stilbene. Disagreement between Stokes- and Anti-Stokes Scattering Frequencies
Authors: Iwata Koichi
Published: September 2002

Picosecond time-resolved spontaneous resonance Raman spectra of the first excited singlet (S1) state of trans-stilbene were measured with various power densities of pump or probe light, for both the Stokes and anti-Stokes scattering regions. Careful calibration of the peak positions of the 285 cm-1 Raman bands reveals that the Stokes scattering band and the anti-Stokes scattering band shift to the same direction in absolute wavenumber, or to the opposite directions in Raman shift, when the pump or probe power density is increased. The direction of the wavenumber shift caused by the pump light field is opposite to that caused by the probe. Because of these apparent peak shifts, the Stokes Raman band and the anti-Stokes Raman band are recorded at different Raman shifts. The intrinsic change of the vibrational level spacing and the apparent peak shift caused by the pump or probe light field can be clearly separated by calculating the “symmetric” and “anti-symmetric” components from the Stokes and anti-Stokes peak positions. The experimental results are not explained by the optical Stark effect in its simplest form. Possible mechanisms to account for the results are discussed.
Far-Infrared Absorption Measurements of Polypeptides and Cytochrome c by THz Radiation
Authors: Yamamoto Kohji , Tominaga Keisuke , Sasakawa Hiroaki , Tamura Atsuo , Murakami Hidetoshi , Ohtake Hideyuki , Sarukura Nobuhiko
Published: September 2002

Pulsed terahertz (THz) radiation and black-body radiation are applied to measure far infrared (FIR) absorption spectra of polypeptides and cytochrome c in the wavenumber region from 7 cm-1 to 160 cm-1. In the region from 7 cm-1 to 55 cm-1, FIR absorption cross sections of polyglycine and poly-L-alanine in powder are greater than those of glycine and L-alanine in powder. On the other hand, FIR absorption spectra of cytochrome c in lyophilized powder show little dependence on protein structures. The structures of biopolymers are investigated by mid-IR absorption (polypeptides and cytochrome c) and by resonance Raman scattering (cytochrome c). FIR spectral features of biopolymers in the THz frequency region are qualitatively discussed in terms of density of states and homogeneous/inhomogeneous broadening.
Crystal Structure of Bis(2,2′-bipyridine)(purine-6-thione)ruthenium(II) Complex
Authors: Yamanari Kazuaki , Nozaki Tsuyoshi , Fuyuhiro Akira , Kaizaki Sumio
Published: September 2002

Two bis(2,2′-bipyridine)ruthenium(II) complexes containing purine-6-thione were prepared. The crystal structure of [Ru(H2put)(bpy)2](ClO4)2·2.5H2O (bpy = 2,2′-bipyridine; H2put = 7H-purine-6(1H)-thione) revealed that the H2put ligand coordinates through the S6/N(7) donors and can form the double N–H···N intermolecular hydrogen bonds in the crystal.
Low Frequency Modes in Heme Proteins
Authors: Rosca Florin , Kumar Anand T N , Ionascu Dan , Ye Xiong , Demidov Andrey A , Champion Paul M
Published: September 2002

The technique of femtosecond coherence spectroscopy is applied to heme protein samples. Strong oscillations are detected near 40 cm-1 in all of the samples studied. Additional modes near 80, 120, and 160 cm-1 are observed in the photochemically active samples. A simple harmonic model is not able to account for the observed relative intensities of these modes or the carrier wavelength dependence of their frequency and phase. As a result, we develop an anharmonic model where the oscillatory signal is damped as the result of heterogeneity in the potential surface. The source of the heterogeneity in the anharmonic potential surface is correlated with the inhomogeneous broadening of the Soret band. The higher harmonics in the photochemically active samples demonstrates that the anharmonic mode is strongly coupled to the ligand photodissociation reaction (i.e., upon photolysis it is displaced far from equilibrium). Moreover, the observation of the ∼40 cm-1 oscillations in all of the iron based heme protein samples, including porphine and protoporphyrin IX model compounds, suggests that this mode is associated with nuclear motion of the core of the porphyrin macrocycle. As a result, we suggest that the reaction coupled oscillations at ∼40 cm-1 and ∼80 cm-1 are a direct reflection of anharmonic heme doming dynamics.
Two Dimensional Infrared Spectroscopy: Studies of the Dynamics of Structures with Femtosecond Pulse Fourier Transform Correlation Spectroscopy
Authors: Hochstrasser Robin M , Ge Nien-Hui , Gnanakaran Sandrasegaram , Zanni Martin T
Published: September 2002

Features of heterodyned infrared photon echo experiments that generate two and three dimensional infrared spectra are described. The relationship of these spectra to structures, correlated fluctuations, energy transfer and orientational motions are illustrated with experimental and simulated examples.
Regio- and Stereochemical Study of Sex Pheromone of Pine Sawfly; Diprion nipponica
Authors: Tai Akira , Syouno Emi , Tanaka Kazuki , Fujita Morifumi , Sugimura Takashi , Higashiura Yasutomo , Kakizaki Masashi , Hara Hideho , Naito Tikahiko
Published: September 2002

Regio- and stereoisomers of 1,2,ω-trimethyldecyl propionate (ω = 5–9) were prepared from stereochemically pure chiral building blocks as sex pheromone candidates of a pine sawfly; Diprion  nipponica. Among the synthesized candidates, (1S,2R,8S)-1,2,8-trimethyldecyl propionate was found to be the sex pheromone of D.  nipponica, based on compatibility of its GC-MS data with that of the extract of females, and its significantly high pheromone activity in a field bioassay. The field bioassay of the synthesized compounds also revealed that (1S,2R,8R)-1,2,8-trimethyldecyl propionate, (1S,2R,7S)-1,2,7-trimethyldecyl propionate, and (1S,2R,6S)-1,2,6-trimethyldecyl propionate could attract male sawflies to some extent as pheromone mimics.
Polarization Specific Ultrafast Nuclear Dichroic Responses: Raman Spectral Density Recovery and Coherent Coupling Effects
Authors: Ziegler Lawrence D , Peng Jian , Constantine Steven
Published: September 2002

The frequency selected dichroic ultrafast responses of neat carbon tetrachloride are reported as a function of pump and probe polarization orientations in a standard two beam experimental configuration. The recovery of the Raman spectral density from these experimental observations is demonstrated. The influence of coherent coupling effects, in this one color, electronically nonresonant class of ultrafast pump–probe experiments is considered. While their contribution to Raman spectral densities via birefringent observations can be neglected, these terms can only be eliminated from the dispersed dichroic technique for Raman spectral density recovery when two-color pump–probe studies are performed.
Chirality-Specific Nonlinear Spectroscopies in Isotropic Media
Authors: Fischer Peer , Albrecht Andreas C
Published: September 2002

Sum or difference frequency generation (SFG or DFG) in isotropic media is in the electric-dipole approximation only symmetry allowed for optically active systems. The hyperpolarizabilty giving rise to these three-wave mixing processes features only one isotropic component. It factorizes into two terms, an energy (denominator) factor and a triple product of transition moments. These forbid degenerate SFG, i.e., second harmonic generation, as well as the existence of the linear electrooptic effect (Pockels effect) in isotropic media. This second order response also has no static limit, which leads to particularly strong resonance phenomena that are qualitatively different from those usually seen in the ubiquitous even-wave mixing spectroscopies. In particular, the participation of two (not the usual one) excited states is essential to achieve dramatic resonance enhancement. We report our first efforts to see such resonantly enhanced chirality specific SFG.
SFG Spectroscopy of CO/Ni(111): UV Pumping and the Transient Hot Band Transition of Adsorbed CO
Authors: Bandara Athula , Kano Satoru S , Onda Ken , Katano Satoshi , Kubota Jun , Domen Kazunari , Hirose Chiaki , Wada Akihide
Published: September 2002

A UV excitation by a picosecond pulse at 266 nm induced an unusual shoulder on the νCO = 1 ← 0 resonance peak of CO/Ni(111) monitored by sum-frequency generation (SFG) of visible and IR pulses. The observed line shape was reproduced by the use of a dipole-dipole interaction model with the coherent potential approximation (CPA) where the hot band transition with a population ratio of 0.3 to 0.7 (v = 1 to v = 0) was assumed. Neither the transition to the two-phonon bound state nor the coupling with the low-frequency phonon modes explained the observed changes. The shoulder appeared only during the UV excitation, which indicated that the electronically driven excitation, presumably by the hot electrons generated by the irradiation, dominated the process. As possible mechanisms, the involvement of an intermediate negative ion resonance state and/or the non-adiabatic coupling of electronic states with C–O stretching mode were considered.
Magnetic Orientation of Lysozyme Crystals
Authors: Tanimoto Yoshifumi , Yamaguchi Rieko , Kanazawa Yuji , Fujiwara Masao
Published: September 2002

Magnetic orientation of Lysozyme crystals was studied in horizontal magnetic fields (< 1 T). The critical field and critical volume are estimated to be 0.5–0.8 T and ca. 33.6 µm3, respectively. The experimental factors affecting magnetic orientation are discussed.
Molecular Wavepacket Decomposition by Nonlinear Interferometry
Authors: Cina Jeffrey A , Humble Travis S
Published: September 2002

We show that nonlinear interferometry with pairs of phase-locked pulse-pairs can determine the complex overlap of an evolving excited-state nuclear wavepacket with a collection of wavepackets moving in specified ways in the ground-state potential. We outline a procedure through which this information can be inverted to yield the form of an evolving wavepacket directly from experimental data.
The Thermodynamic Studies of the Molecular Interactions of Diethyl- and Dibutyltin(IV) Dichloride with Free Base meso-Tetraarylporphyrins
Authors: Asadi Mozaffar , Zabardasti Abedien , Ghasemi Jahanbakhsh
Published: September 2002

The thermodynamic parameters for the interactions of Et2SnCl2 and Bu2SnCl2 with para-substituted meso-tetraphenylporphyrins (H2T(4-X)PP; X = OCH3, CH3, H, Cl) were determined. The overall formation constants K (mol-2 dm6), where (K = K1×K2), were calculated by using UV–vis spectrophotometry titration, and a data refinement was carried out with a computer program, SQUAD. The adducts had a 2 : 1 composition of R2SnCl2 to porphyrin. The overall formation constants decreased with decreasing electron releasing of porphyrins and increasing steric hindrance on an organotin compound, as follow: H2T(4-CH3O)PP > H2T(4-CH3)PP > H2TPP > H2T(4-Cl)PP and Et2SnCl2 > Bu2SnCl2.
Synthesis, Characterization, and Binding of [Cr(naphen)(H2O)2]+ with DNA: Experimental and Modeling Study
Authors: Vaidyanathan Vaidyanathan Ganesan , Vijayalakshmi Rajamanickam , Subramanian Venkatesan , Nair Balachandran Unni
Published: September 2002

A chromium(III) complex of naphen, where naphen denotes 1,2-bis(naphthylideneamino)ethane having the basic salen structure, with an extended aromatic system, has been synthesized and characterized using UV–visible, infrared and ESI mass spectra. Absorption titration and thermal denaturation studies revealed that [Cr(naphen)(H2O)2]+ binds to DNA with moderate strength. Relative viscosity measurements clearly indicate that it binds to DNA by an intercalative mode. This observation is in contrast to an observation with the parent complex, [Cr(salen)(H2O)2]+, which prefers groove binding. Intercalation of the complex results in a change in the helicity of CT DNA, which is reflected in the CD spectrum of DNA in the presence of [Cr(naphen)(H2O)2]+. The binding constant of the complex to CT DNA has been estimated to be (0.51 ± 0.07)×104 M-1 (1 M = mol dm-3), which is lower than the values reported for classical intercalators. Modeling studies with the dodecamer d(GCGCAATTGCGC)2 show that as a result of the intercalation of [Cr(naphen)(H2O)2]+ the vertical separation of the bases increases by 2.67 Å in one strand and by 1.89 Å in the other.
Optically Active S-Bridged CoIIIM (M = PtII, HgII, AuI) Polynuclear Complexes Derived from ΔΔ-[Ni{Co(aet)2(R-pn)}2]4+(aet = 2-Aminoethanethiolate, R-pn = (R)-1,2-Propanediamine)
Authors: Yamada Yasunori , Miyashita Yoshitaro , Fujisawa Kiyoshi , Okamoto Ken-ichi
Published: September 2002

The substitution reaction of ΔΔ-[Ni{Co(aet)2(R-pn)}2]4+ (aet = 2-aminoethanethiolate, R-pn = (R)-1,2- propanediamine) with an equimolar K2[PtCl4] stereoselectively produced an optically active S-bridged trinuclear complex, ΔΔ-[Pt{Co(aet)2(R-pn)}2]4+ (1). A similar reaction with equimolar Hg(ClO4)2·6H2O also selectively gave the trinuclear complex, ΔΔ-[Hg{Co(aet)2(R-pn)}2]4+ (2). Contrary to 1 and 2, a tetranuclear complex, ΔΔ-[Au2{Co(aet)2(R-pn)}2]4+ (3), was obtained by a two-molar-equivalent addition of [AuCl{S(CH2CH2OH)2}]. The crystal structures of 1, 2, and 3 were determined by X-ray crystallography. Each of the Co atoms in 1, 2, and 3 is coordinated by one R-pn and two aet ligands to form an octahedron with a Δ configuration. The Pt atom in 1 is coordinated by four S atoms from two Δ-cis(S)-[Co(aet)2(R-pn)]+ units to take a square-planar geometry. Although the Hg atom in 2 is also surrounded by four S atoms from two Δ-cis(S)-[Co(aet)2(R-pn)]+ units, the geometry around the Hg center is of an appreciably distorted tetrahedron. On the other hand, each of the two Au atoms is bridged by an S atom from one cis(S)-[Co(aet)2(R-pn)]+ unit and an S atom from another unit to form a Co2Au2S4 eight-membered ring. These complexes are characterized based on the electronic absorption, CD, and 13C NMR spectra.
Development of New Three Component Photo-Polymerization Systems Efficient Even Near the Infrared Region
Authors: Kimura Masaru , Mitekura Hirofumi , Fujie Tsutomu , No Tomoko
Published: September 2002

Several visible light initiators of polymerization have been reported mainly as a two component system consisting of a radical-generator and a sensitizing dye possessing absorption bands from 400 to 550 nm. Electron transfer from the excited dye to the radical-generator has been proposed for the two component system. For the purpose of improving the sensitivity and extending light wave length up to near the infrared region, a three component visible light-initiating system has been explored— the combination of a bimolecular visible light-initiating system and electron-donating subsidiary additives. We think if electron transfer from the donor to the excited dye takes place, the dye radical would be generated before the de-excitation of the dye. The generated dye radical should be a better electron donor to the radical-generator because the de-excitation process is blocked by filling the singly occupied HOMO of the excited dye. We tested electron donors such as ferrocene, ruthenocene, (E)-9-julolidinylruthenocenylethylene (E-J-Ru), and p-dimethylaminocinnamylruthenocen (E-DA-Ru) as the electron-donating additives, various sensitizing dyes, and radical generators. When E-J-Ru or E-DA-Ru, the cyanine dyes, and 2,4,6-tris(trichloromethyl)-1,3,5-triazine TCT were selected, the new three component system worked more efficiently than the corresponding two component system, even near the infrared region.
A Succinct Route to the Synthesis of Multi-Labelled [D, 13C] α-Methyl Aromatic Ketones
Authors: Coumbarides Gregory Socrates , Eames Jason , Weerasooriya Neluka
Published: September 2002

A series of multi-labelled aromatic ketones were efficiently synthesized using a simple deprotonation–deuteriation/alkylation strategy. The yields were high and the pro ducts are synthetically useful.
Effect of the Flow Rate of H2 in the Reduction Process on the Physical and Catalytic Properties of H2-Reduced Pt/MoO3
Authors: Matsuda Takeshi , Hanai Ayako , Uchijima Fumiko , Sakagami Hirotoshi , Takahashi Nobuo
Published: September 2002

The surface area of H2-reduced Pt/MoO3 decreased with increasing the flow rate of H2 in the reduction process at 773 K, while the opposite tendency was observed at 523 and 623 K. The surface area was found to depend on the extent of reduction, which was raised by an increase in the H2 flow rate. The largest surface area, about 300 m2 g-1, was obtained at a reduction degree of 64%. A study of reduction with a mixture of H2 and H2O showed that the extent of reduction declined in the presence of H2O. We suggest from these results that the reduction of Pt/MoO3 was prohibited by the action of H2O produced by the reduction. The pentane isomerization activity of H2-reduced Pt/MoO3 was also dependent on the extent of reduction. The highest isomerization activity was obtained at a reduction degree of 76%. H2-reduced Pt/MoO3 exhibited a comparable catalytic activity for pentane isomerization to Pt/H-mordenite.
Dynamics of Molecules and Clusters Studied by Low-Temperature Matrix-Isolation Infrared Spectroscopy and Density-Functional-Theory Calculations
Authors: Nakata Munetaka
Published: September 2002

This article presents an account of applications of low-temperature matrix-isolation (MI) infrared spectroscopy combined with density-functional-theory (DFT) calculations to studies of dynamics of molecules and clusters. The MI technique using a conventional Fourier transform infrared (FTIR) spectrophotometer can measure infrared spectra of less stable isomers, clusters produced by photolysis or supersonic-jet expansion, electronically excited species, and unstable radicals. The observed wavenumbers are compared with the calculated values obtained by the DFT calculation and are used for accurate identification of the structures, including conformations around some rotational axes. Thus photoreaction mechanisms of molecules and clusters are elucidated.
Structures and Magnetism of Cyanide-Bridged Bimetallic Compounds: Design of Complex-Based Magnetic Materials
Authors: Okawa Hisashi , Ohba Masaaki
Published: September 2002

This account concerns the synthesis, structures and magnetism of cyanide-bridged bimetallic network compounds. The study aims at the development of molecular-based magnetic materials. Different network structures, from one-dimensional to three-dimensional, are synthesized by the reaction of [M(CN)6]n- with a cationic constituent such as [Ni-(diamine)2]2+, [Ni(triamine)]2+, [Mn(salen)]+, [Mn(en)]2+, etc., in the absence or presence of an appropriate counter ion. Magnetostructural studies for those bimetallic compounds have clarified fundamental factors contributing to magnetic ordering in bulk, magnetic nature (ferromagnetism or metamagnetism) and magnetic phase-transition temperature (Tc). The strategies for gaining high Tc magnetic material and modulating magnetic nature by a change in network structure are described.
Multielement and Morphological Characterization of Industrial Waste Incineration Fly Ash as Studied by ICP-AES/ICP-MS and SEM-EDS
Authors: Fujimori Eiji , Shiozawa Ryuji , Iwata Seiko , Chiba Koichi , Haraguchi Hiroki
Published: September 2002

The leachabilities of major-to-ultratrace elements in industrial waste incineration fly ash (IWIFA) were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) in order to characterize IWIFA. The leaching data of about 50 elements in the IWIFA sample could be obtained in the concentration range from mg g-1 to sub-µg g-1, when HNO3 and aqua regia were used as the leachants. In addition, morphological observations of IWIFA particles were performed by a scanning electron microscope with an energy dispersive X-ray spectrometer (SEM-EDS) before and after the leaching treatment of the IWIFA samples. From the data for the leaching and morphological observations, the chemical states of the elements in IWIFA were elucidated as follows: (i) core materials of fly ashes were mostly composed of stable oxides of major elements such as Si, Al, Ti, and Fe; (ii) Cu, Zn, Mo, Cd, and Bi were mainly adsorbed on the surface of fly ash particles in the forms of acid soluble compounds; (iii) Mn, Co, Ni, and Pb were partly taken into the core materials of fly ash particles, and partly adsorbed on the fly ash particles; and (iv) Sb, Cr, Sn, In, and W were contained as rather stable compounds in IWIFA.