bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
Magnetic orientation of Lysozyme crystals was studied in horizontal magnetic fields (&lt; 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

Abstract
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

Abstract
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 &gt; H2T(4-CH3)PP &gt; H2TPP &gt; H2T(4-Cl)PP and Et2SnCl2 &gt; 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.