Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 75 , Issue 5
Showing 1-39 articles out of 39 articles from the selected issue
  • Hiro-o Hamaguchi, Koichi Iwata
    Type: scientific monograph
    2002 Volume 75 Issue 5 Pages 883-897
    Published: 2002
    Released: May 15, 2002
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    Structure and dynamics of the lowest excited singlet state of trans-stilbene (the S1 state of tSB) in solution are discussed with an emphasis placed on the elucidation of the mechanism of the trans–cis photoisomerization. Structure of S1 tSB in solution is first discussed based on the time-resolved Raman spectral data and their isotope substitution effects. Original data for an asymmetrically deuteriated tSB, tSB-d5, are presented to confirm the ethylene-like structure of the central C–C linkage of S1 tSB. Next, the time-, temperature-, and solvent-dependent band shape changes of the olefinic C=C stretch band are discussed in terms of the solvent induced dynamic polarization. It is shown that the dynamic polarization model accounts very well, not only for the observed band shape changes, but also for their relevance to the isomerization mechanism. A new microscopic view on the photoisomerization of tSB is thus presented. Picosecond energy dissipation process of S1 tSB is then discussed in relation to the microscopic solvation structure in chloroform. Finally, the mechanism of a new bimolecular reaction between S1 tSB and carbon tetrachloride is discussed on the basis of the diffusion-controlled reaction model.
  • Todd A. Heimer, Edwin J. Heilweil
    Type: scientific monograph
    2002 Volume 75 Issue 5 Pages 899-908
    Published: 2002
    Released: May 15, 2002
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    Broadband femtosecond and longer timescale mid-infrared and far-infrared (THz) probing techniques being explored at NIST using multi-element, mid-infrared focal plane arrays and solid-state THz generators/detectors are presented. Ultrafast infrared pulse generation, detection and pump-probe spectroscopy schemes are first reviewed in detail. These methods are used to examine transitory vibrational, chemical and electron transfer phenomena amenable to time-resolved infrared spectroscopy. Direct monitoring of electron transfer rates (> 5×1012 s) from dye sensitizers ([Ru(dceb)(bpy)2]+2 and Ru(dcb)2(NCS)2 derivatives) anchored to semiconductor solar-cell substrates (nanoparticle TiO2, ZrO2 and SnO2 films) is accomplished by measuring increased mid-IR absorption originating from C=O groups and injected electrons in the substrate. Coherent control of CO-stretching vibrational overtone population distributions in liquid-phase metal-hexacarbonyl systems using deliberately chirped mid-IR excitation pulses has also been explored. Identification of molecular steric and diffusional properties involved in internal ring-closing reaction dynamics of ultraviolet (UV) photo-dissociated (RCp)Mn(CO)3 systems in n-hexane will be presented. Terahertz spectroscopic methods and pulsed THz spectra of calf-thymus DNA, proteins and model dipeptides are also presented and their potential use for extracting bio-molecular functional dynamics discussed.
  • Dorte Madsen, Jens Stenger, Jens Dreyer, Peter Hamm, Erik T. J. Nibber ...
    Type: technical report
    2002 Volume 75 Issue 5 Pages 909-917
    Published: 2002
    Released: May 15, 2002
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    We inspect the O–H stretching vibration of the medium-strong hydrogen bond in phthalic acid monomethyl ester in nonpolar solution by use of single-colour spectrally integrated femtosecond mid-infrared spectroscopy. We derive amplitude and phase characteristics of the coherent modulations of the pump-probe signals as a function of excitation wavelength. We exclude the role of Fermi resonances in the oscillatory contribution to the pump–probe signals. The observed periodic feature is due to wave packet motion of an underdamped out-of-plane 100 cm-1 mode that modulates the hydrogen bond distance. This low-frequency mode anharmonically coupled to the O–H stretching vibration is impulsively excited by the ultrashort mid-infrared pump pulse.
  • Robert Laenen, Andy Thaller
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 919-924
    Published: 2002
    Released: May 15, 2002
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    Sub-picosecond IR-spectroscopy is applied to aqueous NaCl solutions with low concentrated HDO–molecules acting as local probes for the strength of the H-bonds. We find a notable lengthening of the OH-lifetime by the presence of the dissolved ions by a factor of almost 3 up to 2.7 ps at 273 K in comparison to neat water. Simultaneously the average reorientation of the OH–dipoles slows down to 11 ps (273 K) and 4 ps (343 K) while also structural relaxation is found to proceed slower as compared to the case of neat water.
  • Robert Laenen, Konstantinos Simeonidis, Alfred Laubereau
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 925-932
    Published: 2002
    Released: May 15, 2002
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    We demonstrate sub-picosecond spectroscopy of an isotopic water mixture presenting strong evidence for four major spectral components within the OH-band of HDO in the solvent D2O peaked at approximately 3330 cm-1 (I), 3390 cm-1 (II), 3460 cm-1 (III), and 3520 cm-1 (IV). Species I and IV are. proposed to give rise for discrete components with local hexagone and weakly bound structures, respectively. The remaining species are most probably related to combination tones with hydrogen bridge bond vibrations. Furthermore we summarise the findings on the vibrational and spectral dynamics of water as determined by time-resolved IR-spectroscopy of HDO molecules dissolved at low concentration in D2O.
  • Benjamin James Matthewson, Amar Flood, Matthew Ian James Polson, Chris ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 933-942
    Published: 2002
    Released: May 15, 2002
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    The ligand dipyrido[3,2-a:2′,3′-c]phenazine (dppz) and its deuterated analogues, d4-dppz, d6-dppz, d10-dppz, and [ReCl(CO)3] complexes with these ligands have been synthesized. Using DFT calculations it is possible to calculate a geometry of the ligand such that it matches the crystallographic data for a variety of dppz complexes. B3LYP/6-31G(d) frequency calculations correspond closely to the experimental IR and Raman data. Analysis of the calculated normal modes of vibration reveals the presence of a number of modes that are localized to the ring sections of the dppz-framework. Modes 79, 78, 77, 50, and 49, which lie at 1602, 1586, 1576, 1071, and 1034 cm-1, respectively, in the experimental spectra of dppz correspond to phenanthroline-based modes. Modes 68 and 67, lying at 1414 and 1402 cm-1 in dppz are phenazine-based vibrations. These provide an insight into the nature of the MLCT transitions for metal complexes with dppz. The preferential enhancement of phenanthroline-based modes in the resonance Raman spectra of these complexes strongly suggests the π* accepting MO is of phenanthroline character. DFT calculations (B3LYP/6-31G(d)) on the radical anion reveal the elongation of bonds about the pyrimidine ring. The frequency calculations also reveal significant changes in the vibrational spectra for dppz•- from the neutral ligand. Experimental resonance Raman data for the electrochemically reduced [ReCl(CO)3(dppz)]- and the deuterated analogues show distinct isotope shifts that may be correlated to results obtained from the calculations. The characteristic bands observed in these spectra are phenanthroline-based. They may be correlated with time-resolved resonance Raman spectra of Ru(II) and Re(I) complexes.
  • Yun-Liang Li, Dongqi Wang, David Lee Phillips
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 943-948
    Published: 2002
    Released: May 15, 2002
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    We present transient resonance Raman spectra and density functional theory calculations that indicate the iso-dibromoacetic acid (Br–BrCHCOOH) species can be produced in noticeable amounts following ultraviolet photolysis of dibromoacetic acid in cyclohexane solution. We compare the properties of the iso-dibromoacetic acid species to those previously found for the related iso-dibromomethane species. We briefly discuss the potential utility of using iso-dibromoacetic acid in cyclopropanation reactions to make substituted cyclopropane products.
  • Masayuki Yoshizawa, Hirokazu Aoki, Hideki Hashimoto
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 949-955
    Published: 2002
    Released: May 15, 2002
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    Raman signals of excited states in all-trans-β-carotene have been investigated using recently developed femtosecond time-resolved Raman spectroscopy. The Raman signals are distinguished from other absorbance changes due to highly excited states using temporal and spectral dependence on the Raman pump pulse. The negatively stimulated Raman signals due to the 2Ag- excited state are explained by the Raman transition from the vibrational excited levels. The vibrational relaxation of the 2Ag- state has fast and slow kinetics. The fast one has a time constant of 0.6 ps, but the other is slower than the internal conversion to the ground state. Since the molecule exists in the vibrationally excited levels through the relaxation kinetics, the vibrational features in β-carotene are quite important with relation to energy transfer in photosynthesis.
  • Hiromi Okamoto, Mariko Kinoshita, Shigeru Kohtani, Ryoichi Nakagaki, K ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 957-963
    Published: 2002
    Released: May 15, 2002
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    Infrared spectra of the ground, charge transfer (CT), and locally excited (LE) states of isotope-labeled 4-(dimethylamino)benzonitriles (DMABNs) in the region between 1700 and 900 cm-1 are reported. The isotopomers measured are normal DMABN, NC–C6H415NMe2 (dimethylamino nitrogen labeled DMABN), and NC–C6H2D2–NMe2 (3,5-dideuterated DMABN). The infrared spectrum of the excited CT state of DMABN-d2 is consistent with the previous band assignments for normal DMABN and DMABNs isotopically labeled on dimethylamino group. For the LE state of normal DMABN, three bands are observed at 1481, 1415, and 1399 cm-1. This is in contrast with a previously reported transient infrared spectrum, where positions of bands due to the transient do not shift from the ground state ones. The band at ca. 1481 cm-1 is observed for normal and 15N labeled DMABN, but not for DMABN-d2. Except for this point, the band positions are almost identical for the three isotope-labeled species. The vibrational transitions observed at ca. 1415 and 1398 cm-1 are hence attributed to modes with atomic displacements localized on methyl groups and/or the part of the benzonitrile moiety adjacent to the cyano group or the cyano group itself. Quantum chemical calculations of the vibrational spectra for the CT and LE states of DMABN at present do not correctly reproduce the experimental spectra, which means that more accurate calculations are needed for a reliable analysis of these spectra.
  • Yasuhisa Mizutani, Teizo Kitagawa
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 965-971
    Published: 2002
    Released: May 15, 2002
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    The formation of the (d, d) excited state of (meso-tetraphenylporphyrinato)nickel(II) ([Ni(tpp)]) upon (π, π*) excitation, and its vibrational energy relaxation were monitored by picosecond time-resolved resonance Raman spectroscopy. Stokes resonance Raman bands due the (d, d) excited state instantaneously appeared upon the photoexcitation into the (π, π*) excited state. Their intensities decayed with a time constant of about 250 ps, which corresponds to electronic relaxation from the (d, d) excited state to the electronic ground state. This is consistent with the results of ultrafast absorption measurements reported by Eom et al. [H. S. Eom, S. C. Jeoung, D. Kim, J. H. Ha, and Y. R. Kim, J. Phys. Chem. A, 101, 3661 (1997)]. Anti-Stokes ν4 (macrocycle in-plane mode) intensities of [Ni(tpp)] in the (d, d) excited state appeared promptly and decayed with a time constant of 3.6 ± 0.6 ps. The rise and decay of anti-Stokes intensity are interpreted as vibrational excitation due to the excess energy and intermolecular vibrational energy transfer to the surrounding solvent molecules, respectively. The φ4 mode, which is mainly ν(CC) of the peripheral phenyl groups, gave no detectable anti-Stokes intensity although the mode gave appreciable Stokes intensity. This means that the φ4 mode is left vibrationally less excited than the ν4 mode in the process of vibrational energy relaxation and that intramolecular vibrational energy redistribution is not completed in a subpicosecond time regime. These results for [Ni(tpp)] demonstrate that the vibrational modes of peripheral groups are vibrationally less excited shortly after the formation of the (d, d) excited state and that energy redistribution in the peripheral groups takes place in picoseconds, such a short time is competitive with vibrational energy transfer to the surrounding solvent molecules.
  • John B. Asbury, Yongqiang Wang, Tianquan Lian
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 973-983
    Published: 2002
    Released: May 15, 2002
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    Peak shift dynamics of CO stretching modes of [Re(R2-bpy)(CO)3Cl] [R = COOH and COOEt] complexes in their MLCT excited state were studied in polar solvents using femtosecond visible pump and IR probe spectroscopy. For Re complex in dimethyl formamide, peak shift magnitudes for the three CO stretching modes are different but their dynamics are identical. Comparison in different alcohols showed that peak shift magnitude increases with solvent dielectric constant and peak shift time follows the trend of solvation time. The observed peak shift is attributed to solvation-induced time-dependent vibrational Stokes shift. A general theory based on the Onsager dielectric continuum model of solute solvent interaction and time-dependent reaction field was developed to qualitatively describe time-dependent vibrational Stokes shift. The theory predicts that the peak shift correlation function is determined by solvent dielectric relaxation at the vibration frequency, and the peak shift magnitudes are solvent and normal mode dependent. Although the observed trend of solvation-induced vibrational Stokes shift is consistent with the theoretical predictions, other contributions such as solute polarizability should also be included in more complete models. Solvation induced vibrational Stokes shift may be a general phenomenon in time-resolved vibrational spectroscopy of molecules undergoing significant change in charge or charge distribution.
  • Peter Hamm, Sander Woutersen
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 985-988
    Published: 2002
    Released: May 15, 2002
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    Several approaches to calculate the coupling between the two amide I modes of the glycine dipeptide are compared. The full (φ, ψ) conformational space of the molecule is explored, and conditions for the validity of the different approaches are discussed.
  • Christoph Scheurer, Shaul Mukamel
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 989-999
    Published: 2002
    Released: May 15, 2002
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    We survey the principles for the design of multidimensional vibrational spectroscopies that draw upon the analogy with liquid or solid state NMR and EPR spectroscopy. The much faster time-scales and the different energy regime in laser spectroscopy provide additional possibilities that lack magnetic spectroscopy counterparts. We also discuss the notion of through-bond vs through-space couplings between localized vibrations, which are of different nature than in NMR.
  • Toshinari Takahashi, Takashi Ogura
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1001-1004
    Published: 2002
    Released: May 15, 2002
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    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.
  • Mischa Bonn, Martin Wolf
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1005-1010
    Published: 2002
    Released: May 15, 2002
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    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.
  • Boris B. Akhremitchev, Gilbert C. Walker
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1011-1018
    Published: 2002
    Released: May 15, 2002
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    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.
  • Akira Yamakata, Taka-aki Ishibashi, Hiroshi Onishi
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1019-1022
    Published: 2002
    Released: May 15, 2002
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    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.
  • Nam Woong Song, Hyun Sun Cho, Min-Chul Yoon, Sae Chae Jeoung, Naoya Yo ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1023-1029
    Published: 2002
    Released: May 15, 2002
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    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.
  • Tatsuya Fujino, Sergei Yu. Arzhantsev, Tahei Tahara
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1031-1040
    Published: 2002
    Released: May 15, 2002
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    Photoisomerization dynamics and the electronic relaxation process of trans-azobenzene after the S2(ππ*) ← S0 photoexcitation were investigated in solution by femtosecond and picosecond time-resolved spectroscopy (UV-visible absorption, Raman, and fluorescence). Femtosecond time-resolved absorption spectrosocopy was performed to observe the transient absorption of the S2 and S1 states. Immediately after photoexcitation, a very broad transient absorption peaked at 475 and 600 nm was observed. This transient absorption decayed repidly within 0.5 ps, and this ultrafast component was attributed to the Sn ← S2(ππ*) absorption. After the decay of the S2 state, a transient absorption showing peaks at 410 nm and 500 nm was observed, which was ascribable to the S1 state. This transient absorption is similar to the Sn ← S1 absorption that is observed after S1 ← S0 photoexcitation. Picosecond time-resolved Raman measurements were carried out to obtain information about the molecular structure of azobenzene in the S1 state. The NN stretching frequency in the S1 spectrum was determined with use of 15N-substituted azobenzene, and it was found that the NN stretching frequency in the S1 state is very close to that in the S0 state (1428 cm-1 in the S1 and 1440 cm-1 in the S0). This fact indicated that the NN bond retains a double bond character in the S1 state. A strong similarity was also found between the S1 and S0 Raman spectra. The double bond nature of the NN bond as well as the similarity between the S1 and S0 Raman spectra indicates that the observed S1 state has a planar structure around the NN bond. The Raman data indicate that the observed S1 state is not a twisted excited state that appears during the rotational isomerization, but is the excited state that is populated during the S2 → S1 → S0 relaxation process while retaining a planar molecular structure. Anti-Stokes Raman measurements were performed to obtain information about the vibrational relaxation process. The anti-Stokes Raman spectra showed that the S1 state was highly vibrationally excited. It was also observed that the hot bands due to the S0 state appear after the decay of the S1 state and these S0 hot bands disappear with a time constant of ∼16 ps in hexane. Femtosecond time-resolved and steady-state fluorescence measurements were performed and they revealed that the S2 → “planar” S1 relaxation process is the major relaxation pathway following S2 photoexcitation. The quantum yield of the S2 → “planar” S1 electric relaxation was evaluated by comparing the intensity of the S2 and S1 fluorescence, and it was found to be almost unity. A series of time-resolved spectroscopy demonstrated that the S2 rotational isomerization mechanism, which had been believed so far, does not exist. It has been clarified that the isomerization occurs in the S1 state after S2 → S1 relaxation. Consequently, it is concluded that the isomerization of azobenzene takes place in the S1 state by inversion in cases of both S2 and S1 photoexcitation.
  • Jean Oberlé, Gediminas Jonusauskas, Emmanuel Abraham, Ren&eacut ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1041-1047
    Published: 2002
    Released: May 15, 2002
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    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.
  • Wolfgang Werncke, Sebastian Wachsmann-Hogiu,, Jens Dreyer, Alexander I ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1049-1055
    Published: 2002
    Released: May 15, 2002
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    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.
  • Mrinalini Puranik, Siva Umapathy
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1057-1064
    Published: 2002
    Released: May 15, 2002
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    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.
  • Konstantin Leonid Litvinenko, Naomi Marica Webber, Stephen Roy Meech
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1065-1070
    Published: 2002
    Released: May 15, 2002
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    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.
  • Hideaki Kano, Takayoshi Kobayashi
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1071-1074
    Published: 2002
    Released: May 15, 2002
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    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.
  • Koichi Iwata
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1075-1082
    Published: 2002
    Released: May 15, 2002
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    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.
  • Kohji Yamamoto, Keisuke Tominaga, Hiroaki Sasakawa, Atsuo Tamura, Hide ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1083-1092
    Published: 2002
    Released: May 15, 2002
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    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.
  • Florin Rosca, Anand T. N. Kumar, Dan Ionascu, Xiong Ye, Andrey A. Demi ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1093-1101
    Published: 2002
    Released: May 15, 2002
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    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.
  • Robin. M. Hochstrasser, Nien-Hui Ge, Sandrasegaram Gnanakaran, Martin ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1103-1110
    Published: 2002
    Released: May 15, 2002
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    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.
  • Lawrence D. Ziegler, Jian Peng, Steven Constantine
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1111-1118
    Published: 2002
    Released: May 15, 2002
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    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.
  • Peer Fischer, Andreas C. Albrecht
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1119-1124
    Published: 2002
    Released: May 15, 2002
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    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.
  • Athula Bandara, Satoru S. Kano, Ken Onda, Satoshi Katano, Jun Kubota, ...
    Type: Others
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1125-1132
    Published: 2002
    Released: May 15, 2002
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    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.
  • Yoshifumi Tanimoto, Rieko Yamaguchi, Yuji Kanazawa, Masao Fujiwara
    Type: Introduction
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1133-1134
    Published: 2002
    Released: May 15, 2002
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    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.
  • Jeffrey A. Cina, Travis S. Humble
    Type: Introduction
    Subject area: TP
    2002 Volume 75 Issue 5 Pages 1135-1136
    Published: 2002
    Released: May 15, 2002
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    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.
  • Mozaffar Asadi, Abedien Zabardasti, Jahanbakhsh Ghasemi
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 5 Pages 1137-1141
    Published: 2002
    Released: May 15, 2002
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    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.
  • Vaidyanathan Ganesan Vaidyanathan, Rajamanickam Vijayalakshmi, Venkate ...
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 5 Pages 1143-1149
    Published: 2002
    Released: May 15, 2002
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    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.
  • Yasunori Yamada, Yoshitaro Miyashita, Kiyoshi Fujisawa, Ken-ichi Okamo ...
    Type: Others
    Subject area: AI
    2002 Volume 75 Issue 5 Pages 1151-1157
    Published: 2002
    Released: May 15, 2002
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    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.
  • Masaru Kimura, Hirofumi Mitekura, Tsutomu Fujie, Tomoko No
    Type: Others
    Subject area: OB
    2002 Volume 75 Issue 5 Pages 1159-1162
    Published: 2002
    Released: May 15, 2002
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    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.
  • Gregory Socrates Coumbarides, Jason Eames, Neluka Weerasooriya
    Type: Introduction
    Subject area: OB
    2002 Volume 75 Issue 5 Pages 1163-1164
    Published: 2002
    Released: May 15, 2002
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    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.
  • Takeshi Matsuda, Ayako Hanai, Fumiko Uchijima, Hirotoshi Sakagami, Nob ...
    Type: Others
    Subject area: AM
    2002 Volume 75 Issue 5 Pages 1165-1171
    Published: 2002
    Released: May 15, 2002
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    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.
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