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Hewitt P, Shultz DA, Kirk ML. Rules for Magnetic Exchange in Azulene-Bridged Biradicals: Quo Vadis? J Org Chem 2021; 86:15577-15587. [PMID: 34644082 DOI: 10.1021/acs.joc.1c02085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Electronic coupling through organic bridges facilitates magnetic exchange interactions and controls electron transfer and single-molecule device electron transport. Electronic coupling through alternant π-systems (e.g., benzene) is better understood than the corresponding coupling through nonalternant π-systems (e.g., azulene). Herein, we examine the structure, spectroscopy, and magnetic exchange coupling in two biradicals (1,3-SQ2Az and 1,3-SQ-Az-NN; SQ = the zinc(II) complex of spin-1/2 semiquinone radical anion, NN = spin-1/2 nitronylnitroxide; Az = azulene) that possess nonalternant azulene π-system bridges. The SQ radical spin density in both molecules is delocalized into the Az π-system, while the NN spin is effectively localized onto the five-atom ONCNO π-system of NN radical. The spin distributions and interactions are probed by EPR spectroscopy and magnetic susceptibility measurements. We find that J = +38 cm-1 for 1,3-SQ2Az and J = +9 cm-1 for 1,3-SQ-Az-NN (H=-2JS^SQ·S^SQorNN). Our results highlight the differences in exchange coupling mediated by azulene compared to exchange coupling mediated by alternant π-systems.
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Affiliation(s)
- Patrick Hewitt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Martin L Kirk
- Department of Chemistry, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
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2
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Morgenroth M, Scholz M, Guy L, Oum K, Lenzer T. Ultrafast excited-state dynamics of thin films consisting of helicene-like molecules based on dibenzo[ c,h]acridine. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1959072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
| | - Mirko Scholz
- Physikalische Chemie, Universität Siegen, Siegen, Germany
| | - Laure Guy
- Univ. Lyon, ENS de Lyon, CNRS UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie, Lyon, France
| | - Kawon Oum
- Physikalische Chemie, Universität Siegen, Siegen, Germany
| | - Thomas Lenzer
- Physikalische Chemie, Universität Siegen, Siegen, Germany
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3
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Scholz M, Hoffmann C, Klein JR, Wirtz M, Jung G, Oum K. Exploring Differences in Excited-State Properties of Styryl-BODIPY Chromophores upon Change from α- to β-Substitution. Z PHYS CHEM 2019. [DOI: 10.1515/zpch-2019-1374] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
We present a femtosecond pump-probe UV-Vis broadband transient absorption spectroscopy study of two styryl-substituted BODIPY chromophores with different position of the substituent. The α-substituted isomer shows typical BODIPY-type spectral features, such as sharp absorption and emission bands, a small Stokes shift and an excited-state lifetime in the 4 ns range, which only weakly depends on the solvent. In contrast, β-styryl-BODIPY features much broader steady-state absorption and emission spectra and a larger Stokes shift, particularly in polar solvents. Transient absorption spectroscopy including a complete global kinetic analysis reports a substantial decrease in S1 lifetime to 300 ps for polar solvents upon change from α- to β-substitution. In the case of the α-isomer, TD-DFT calculations identify a typical “cyanine-type” electron rearrangement upon S0 → S1 excitation accompanied by a slight reduction in dipole moment. In contrast, the same transition in the β-isomer shows strong intramolecular charge transfer (ICT) character involving a substantial increase in dipole moment. Assuming a simple energy-gap-law argument, the accelerated nonradiative decay of the β-isomer in polar solvents may be linked to the decrease of the S1(ICT)-S0 energy difference. BODIPY dyes with a conjugated substituent in β-position therefore suffer a substantial loss in fluorescence brightness in polar environments compared with their α-substituted counterparts. This might limit their applicability in fluorescence imaging.
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Affiliation(s)
- Mirko Scholz
- University of Siegen , Physical Chemistry , Adolf-Reichwein-Str. 2 , 57076 Siegen , Germany
| | - Caroline Hoffmann
- Biophysical Chemistry , Saarland University , Campus Building B2.2 , 66123 Saarbrücken , Germany
| | - Johannes R. Klein
- University of Siegen , Physical Chemistry , Adolf-Reichwein-Str. 2 , 57076 Siegen , Germany
| | - Marcel Wirtz
- Biophysical Chemistry , Saarland University , Campus Building B2.2 , 66123 Saarbrücken , Germany
| | - Gregor Jung
- Biophysical Chemistry , Saarland University , Campus Building B2.2 , 66123 Saarbrücken , Germany
| | - Kawon Oum
- University of Siegen , Physical Chemistry , Adolf-Reichwein-Str. 2 , 57076 Siegen , Germany
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4
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Balevičius V, Wei T, Di Tommaso D, Abramavicius D, Hauer J, Polívka T, Duffy CDP. The full dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating. Chem Sci 2019; 10:4792-4804. [PMID: 31183032 PMCID: PMC6521204 DOI: 10.1039/c9sc00410f] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 03/29/2019] [Indexed: 01/04/2023] Open
Abstract
In some molecular systems, such as nucleobases, polyenes or sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale. Where does this energy go or among which degrees of freedom it is being distributed at such early times?
In some molecular systems, such as nucleobases, polyenes or the active ingredients of sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale, raising questions such as: where does this energy go or among which degrees of freedom it is being distributed at such early times? Here we use transient absorption spectroscopy to track excitation energy dispersing from the optically accessible vibronic subsystem into the remaining vibrational subsystem of the solute and solvent. Monitoring the flow of energy during vibrational redistribution enables quantification of local molecular heating. Subsequent heat dissipation away from the solute molecule is characterized by classical thermodynamics and molecular dynamics simulations. Hence, we present a holistic approach that tracks the internal temperature and vibronic distribution from the act of photo-excitation to the restoration of the global equilibrium. Within this framework internal vibrational redistribution and vibrational cooling are emergent phenomena. We demonstrate the validity of the framework by examining a highly controversial example, carotenoids. We show that correctly accounting for the local temperature unambiguously explains their energetically and temporally congested spectral dynamics without the ad hoc postulation of additional ‘dark’ states. An immediate further application of this approach would be to monitor the excitation and thermal dynamics of pigment–protein systems.
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Affiliation(s)
- Vytautas Balevičius
- School of Chemical and Biological Sciences , Queen Mary University of London , Mile End Road , London E1 4NS , UK .
| | - Tiejun Wei
- School of Chemical and Biological Sciences , Queen Mary University of London , Mile End Road , London E1 4NS , UK .
| | - Devis Di Tommaso
- School of Chemical and Biological Sciences , Queen Mary University of London , Mile End Road , London E1 4NS , UK .
| | - Darius Abramavicius
- Institute of Chemical Physics , Vilnius University , Sauletekio av. 9 , Vilnius , LT-10222 , Lithuania
| | - Jürgen Hauer
- Fakultät für Chemie , Technical University of Munich , Lichtenbergstraße 4 , D-85748 Garching , Germany.,Photonics Institute , TU Wien , Gußhausstraße 27 , 1040 Vienna , Austria
| | - Tomas Polívka
- Institute of Physics and Biophysics , Faculty of Science , University of South Bohemia , Branišovská 1760 , 37005 České Budějovice , Czech Republic
| | - Christopher D P Duffy
- School of Chemical and Biological Sciences , Queen Mary University of London , Mile End Road , London E1 4NS , UK .
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5
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Excited-state dynamics of 3,3′-dihydroxyisorenieratene and (3R,3′R)-zeaxanthin: Observation of vibrationally hot S0 species. Arch Biochem Biophys 2018; 646:137-144. [DOI: 10.1016/j.abb.2018.03.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 03/13/2018] [Accepted: 03/26/2018] [Indexed: 11/19/2022]
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6
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Scholz M, Flender O, Lenzer T, Oum K. Ultrafast Excited-State Dynamics of all-trans-Capsanthin in Organic Solvents. J Phys Chem A 2017; 121:8380-8388. [DOI: 10.1021/acs.jpca.7b08252] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mirko Scholz
- Physikalische Chemie, Universität Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| | - Oliver Flender
- Physikalische Chemie, Universität Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| | - Thomas Lenzer
- Physikalische Chemie, Universität Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
| | - Kawon Oum
- Physikalische Chemie, Universität Siegen, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
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7
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Rivera-Rivera LA, Wagner AF, Sewell TD, Thompson DL. Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath. J Chem Phys 2015; 142:014303. [PMID: 25573557 DOI: 10.1063/1.4904314] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is ∼100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane "simultaneously" colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed-phase densities.
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Affiliation(s)
- Luis A Rivera-Rivera
- Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211-7600, USA
| | - Albert F Wagner
- Argonne National Laboratory, Chemical Sciences and Engineering Division, Argonne, Illinois 60439, USA
| | - Thomas D Sewell
- Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211-7600, USA
| | - Donald L Thompson
- Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211-7600, USA
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8
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Ehlers F, Scholz M, Schimpfhauser J, Bienert J, Oum K, Lenzer T. Collisional relaxation of apocarotenals: identifying the S* state with vibrationally excited molecules in the ground electronic state S0*. Phys Chem Chem Phys 2015; 17:10478-88. [DOI: 10.1039/c4cp05600k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The S* signal of carotenoids corresponds to vibrationally hot molecules in the ground electronic state S0*.
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Affiliation(s)
- Florian Ehlers
- Georg-August-Universität Göttingen
- Institut für Physikalische Chemie
- 37077 Göttingen
- Germany
| | - Mirko Scholz
- Universität Siegen
- Physikalische Chemie 2
- 57076 Siegen
- Germany
| | | | - Jürgen Bienert
- Max-Planck-Institut für biophysikalische Chemie
- 37077 Göttingen
- Germany
| | - Kawon Oum
- Universität Siegen
- Physikalische Chemie 2
- 57076 Siegen
- Germany
| | - Thomas Lenzer
- Universität Siegen
- Physikalische Chemie 2
- 57076 Siegen
- Germany
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9
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Molloy MS, Snyder JA, Bragg AE. Structural and Solvent Control of Nonadiabatic Photochemical Bond Formation: Photocyclization of o-Terphenyl in Solution. J Phys Chem A 2014; 118:3913-25. [DOI: 10.1021/jp501988g] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Molly S. Molloy
- Department
of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Joshua A. Snyder
- Department
of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Arthur E. Bragg
- Department
of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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10
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Ernsting N, Lenzer T, Oum K. Time-resolved laser spectroscopy of nonreactive processes in ionic liquids and their binary mixtures with organic solvents and CO2. J Mol Liq 2014. [DOI: 10.1016/j.molliq.2013.08.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Collins P, Carpenter BK, Ezra GS, Wiggins S. Nonstatistical dynamics on potentials exhibiting reaction path bifurcations and valley-ridge inflection points. J Chem Phys 2013; 139:154108. [DOI: 10.1063/1.4825155] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Arden-Jacob J, Drexhage KH, Druzhinin SI, Ekimova M, Flender O, Lenzer T, Oum K, Scholz M. Ultrafast photoinduced dynamics of the 3,6-diaminoacridinium derivative ATTO 465 in solution. Phys Chem Chem Phys 2013; 15:1844-53. [PMID: 23247684 DOI: 10.1039/c2cp43493h] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The excited state dynamics of the dye ATTO 465, a well-known fluorescence marker for biological applications, have been characterized in various solvents including THF, ethanol, methanol, water and the highly polar protic ionic liquid 2-hydroxyethylammonium formate (2-OH-EAF) by combining results from time-correlated single-photon counting (TCSPC) and ultrafast pump-supercontinuum probe (PSCP) spectroscopy as well as steady-state absorption and fluorescence. In water, 2-OH-EAF and two fluorinated alcohols, there is a pronounced blue-shift and broadening of the S(0) → S(1) absorption band and also a larger Stokes shift than in the other solvents, indicating a particular influence of hydrogen-bonding interactions. S(1) lifetimes from TCSPC at 25 °C range from 3.3 ns to 5.6 ns. An unusual increase in the S(1) lifetime with temperature is observed for ethanol and methanol, however water behaves in the opposite way. The behavior can be tentatively explained by a solvent- and temperature-dependent "proximity effect", where coupling of the close-lying S(1) and S(2) states influences the intramolecular relaxation rate of the dye. In addition, temperature-dependent complex equilibria of ATTO 465 with solvent molecules may influence the measured lifetimes. Several excited-state absorption (ESA) transitions are identified in the PSCP spectra, which are in good agreement with the position of the UV bands in the steady-state absorption spectra. Small shifts of the stimulated emission and ESA bands are consistent with solvation dynamics in the excited electronic state. An additional ~16 ps component in water, visible over the entire spectral range, is tentatively ascribed to a fast IC channel which is accessed by a fraction of ATTO 465 molecules.
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Affiliation(s)
- Jutta Arden-Jacob
- Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany
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13
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Oum K, Lohse PW, Flender O, Klein JR, Scholz M, Lenzer T, Du J, Oekermann T. Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films. Phys Chem Chem Phys 2012; 14:15429-37. [DOI: 10.1039/c2cp42961f] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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14
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Gutkowski KI, Fernández-Prini R, Aramendía PF, Japas ML. Critical Effects on Attractive Solutes in Binary Liquid Mixtures Close to Their Consolute Point: A New Experimental Strategy. J Phys Chem B 2011; 115:15303-12. [DOI: 10.1021/jp209007y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Karin I. Gutkowski
- Gerencia Química, CAC, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429-Buenos Aires, Argentina
| | - Roberto Fernández-Prini
- Gerencia Química, CAC, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429-Buenos Aires, Argentina
- INQUIMAE/DQIAQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428-Buenos Aires, Argentina
| | - Pedro F. Aramendía
- INQUIMAE/DQIAQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428-Buenos Aires, Argentina
| | - M. Laura Japas
- Gerencia Química, CAC, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429-Buenos Aires, Argentina
- Escuela de Ciencia y Tecnología, Universidad Nacional de San Martín, Martín de Irigoyen 3100, 1650-San Martín, Provincia Buenos Aires, Argentina
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15
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Burdzinski G, Sliwa M, Zhang Y, Delbaere S. Early Events in the Photochemistry of 1,2,3-Thiadiazole Studied by Ultrafast Time-Resolved UV–Vis and IR Spectroscopies. J Phys Chem A 2011; 115:14300-5. [DOI: 10.1021/jp2055238] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gotard Burdzinski
- Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Michel Sliwa
- Université Lille Nord de France, CNRS-UMR 8516, Lille1, LASIR, F-59655 Villeneuve d’Ascq, France
| | - Yunlong Zhang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, United States
| | - Stéphanie Delbaere
- Université Lille Nord de France, CNRS UMR 8516, UDSL, F-59006 Lille, France
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16
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Fujii N, Mizuno M, Mizutani Y. Direct Observation of Vibrational Energy Flow in Cytochrome c. J Phys Chem B 2011; 115:13057-64. [DOI: 10.1021/jp207500b] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Naoki Fujii
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Misao Mizuno
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Yasuhisa Mizutani
- Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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17
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Golibrzuch K, Ehlers F, Scholz M, Oswald R, Lenzer T, Oum K, Kim H, Koo S. Ultrafast excited state dynamics and spectroscopy of 13,13'-diphenyl-β-carotene. Phys Chem Chem Phys 2011; 13:6340-51. [PMID: 21365078 DOI: 10.1039/c0cp02525a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast transient broadband absorption spectroscopy based on the Pump-Supercontinuum Probe (PSCP) technique has been applied to characterize the excited state dynamics of the newly-synthesized artificial β-carotene derivative 13,13'-diphenyl-β-carotene in the wavelength range 340-770 nm with ca. 60 fs cross-correlation time after excitation to the S(2) state. The influence of phenyl substitution at the polyene backbone has been investigated in different solvents by comparing the dynamics of the internal conversion (IC) processes S(2)→ S(1) and S(1)→ S(0)* with results for β-carotene. Global analysis provides IC time constants and also time-dependent S(1) spectra demonstrating vibrational relaxation processes. Intramolecular vibrational redistribution processes are accelerated by phenyl substitution and are also solvent-dependent. DFT and TDDFT-TDA calculations suggest that both phenyl rings prefer an orientation where their ring planes are almost perpendicular to the plane of the carotene backbone, largely decoupling them electronically from the polyene system. This is consistent with several experimental observations: the up-field chemical shift of adjacent hydrogen atoms by a ring-current effect of the phenyl groups in the (1)H NMR spectrum, a small red-shift of the S(0)→ S(2)(0-0) transition energy in the steady-state absorption spectrum relative to β-carotene, and almost the same S(1)→ S(0)* IC time constant as in β-carotene, suggesting a similar S(1)-S(0) energy gap. The oscillator strength of the S(0)→ S(2) transition of the diphenyl derivative is reduced by ca. 20%. In addition, we observe a highly structured ground state bleach combined with excited state absorption at longer wavelengths, which is typical for an "S* state". Both features can be clearly assigned to absorption of vibrationally hot molecules in the ground electronic state S(0)* superimposed on the bleach of room temperature molecules S(0). The S(0)* population is formed by IC from S(1). These findings are discussed in detail with respect to alternative interpretations previously reported in the literature. Understanding the dynamics of this type of artificial phenyl-substituted carotene systems appears useful regarding their future structural optimization with respect to enhanced thermal stability while keeping the desired photophysical properties.
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Affiliation(s)
- Kai Golibrzuch
- Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Göttingen, Germany
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18
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Lohse PW, Kuhnt J, Druzhinin SI, Scholz M, Ekimova M, Oekermann T, Lenzer T, Oum K. Ultrafast photoinduced relaxation dynamics of the indoline dye D149 in organic solvents. Phys Chem Chem Phys 2011; 13:19632-40. [DOI: 10.1039/c1cp22429h] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Fernández-Prini R, Laura Japas M, Marceca E. Near-critical and supercritical dilute solutions viewed from macroscopic and molecular-scale perspectives. J Supercrit Fluids 2010. [DOI: 10.1016/j.supflu.2010.10.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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20
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Kajiya D, Saitow KI. Site-Selective Solvation in Supercritical CO2Observed by Raman Spectroscopy: Phenyl Group Leads to Greater Attractive Energy than Chloro Group. J Phys Chem B 2010; 114:16832-7. [DOI: 10.1021/jp107820j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Daisuke Kajiya
- Natural Science Center for Basic Research and Development (N-BARD) and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima, Hiroshima 739-8526, Japan
| | - Ken-ichi Saitow
- Natural Science Center for Basic Research and Development (N-BARD) and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-hiroshima, Hiroshima 739-8526, Japan
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21
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Mikheev YA, Guseva LN, Ershov YA. The nature of chromaticity of triphenylmethane, xanthene, phthalocyanine, and thiazine dyes. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2010. [DOI: 10.1134/s003602441010016x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Schwarzer D, Troe J, Votsmeier M, Zerezke M. Collisional deactivation of vibrationally highly excited azulene in supercritical xenon/ethane mixtures. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19971010336] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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23
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Hold U, Lenzer T, Luther K, Reihs K, Symonds A. Collisional energy transfer probabilities in the deactivation of highly vibrationally excited aromatics. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19971010331] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Kajiya D, Saitow KI. Solute−Solvent Intermolecular Interactions in Supercritical Xe, SF6, CO2, and CHF3 Investigated by Raman Spectroscopy: Greatest Attractive Energy Observed in Supercritical Xe. J Phys Chem B 2010; 114:8659-66. [DOI: 10.1021/jp101217s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daisuke Kajiya
- Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Ken-ichi Saitow
- Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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Branigan ET, van Staveren MN, Apkarian VA. Solidlike coherent vibronic dynamics in a room temperature liquid: Resonant Raman and absorption spectroscopy of liquid bromine. J Chem Phys 2010; 132:044503. [DOI: 10.1063/1.3291610] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Mikheev YA, Guseva LN, Ershov YA. Reversible isomerization of chromogenic dimers and the nature of azulene chromaticity. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2010. [DOI: 10.1134/s0036024410110269] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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27
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Lenzer T, Ehlers F, Scholz M, Oswald R, Oum K. Assignment of carotene S* state features to the vibrationally hot ground electronic state. Phys Chem Chem Phys 2010; 12:8832-9. [DOI: 10.1039/b925071a] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Voskresenska V, Wilson RM, Panov M, Tarnovsky AN, Krause JA, Vyas S, Winter AH, Hadad CM. Photoaffinity labeling via nitrenium ion chemistry: protonation of the nitrene derived from 4-amino-3-nitrophenyl azide to afford reactive nitrenium ion pairs. J Am Chem Soc 2009; 131:11535-47. [PMID: 19624129 DOI: 10.1021/ja902224m] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phenyl azides with powerful electron-donating substituents are known to deviate from the usual photochemical behavior of other phenyl azides. They do not undergo ring expansion but form basic nitrenes that protonate to form nitrenium ions. The photochemistry of the widely used photoaffinity labeling system 4-amino-3-nitrophenyl azide, 5, has been studied by transient absorption spectroscopy from femtosecond to microsecond time domains and from a theoretical perspective. The nitrene generation from azide 5 occurs on the S(2) surface, in violation of Kasha's rule. The resulting nitrene is a powerful base and abstracts protons extremely rapidly from a variety of sources to form a nitrenium ion. In methanol, this protonation occurs in about 5 ps, which is the fastest intermolecular protonation observed to date. Suitable proton sources include alcohols, amine salts, and even acidic C-H bonds such as acetonitrile. The resulting nitrenium ion is stabilized by the electron-donating 4-amino group to afford a diiminoquinone-like species that collapses relatively slowly to form the ultimate cross-linked product. In some cases in which the anion is a good hydride donor, cross-linking is replaced by reduction of the nitrenium ion to the corresponding amine.
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Affiliation(s)
- Valentyna Voskresenska
- Department of Chemistry and the Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
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Zhang Y, Kubicki J, Platz MS. Ultrafast UV−Visible and Infrared Spectroscopic Observation of a Singlet Vinylcarbene and the Intramolecular Cyclopropenation Reaction. J Am Chem Soc 2009; 131:13602-3. [DOI: 10.1021/ja905992p] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Yunlong Zhang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Jacek Kubicki
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Matthew S. Platz
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
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Skarmoutsos I, Dellis D, Samios J. The Effect of Intermolecular Interactions on Local Density Inhomogeneities and Related Dynamics in Pure Supercritical Fluids. A Comparative Molecular Dynamics Simulation Study. J Phys Chem B 2009; 113:2783-93. [DOI: 10.1021/jp809271n] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ioannis Skarmoutsos
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| | - Dimitris Dellis
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| | - Jannis Samios
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
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31
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Liu KL, Lee SJ, Chen IC, Hsu CP, Yeh MY, Luh TY. Excited-State Dynamics of [(1,1′-Biphenyl)-4,4-diyldi-2,1-ethenediyl]bis(dimethylsilane). J Phys Chem A 2009; 113:1218-24. [DOI: 10.1021/jp807662g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | - Chao-Ping Hsu
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115, Republic of China
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Schmierer T, Schreier WJ, Koller FO, Schrader TE, Gilch P. Impact of vibrational excitation on the kinetics of a nascent ketene. Phys Chem Chem Phys 2009; 11:11596-607. [DOI: 10.1039/b915451e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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33
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Dvořák M, Fidler V, Lohse PW, Michl M, Oum K, Wagener P, Schroeder J. Ultrafast intramolecular electronic energy transfer in rigidly linked aminopyrenyl–aminobenzanthronyl dyads—a femtosecond study. Phys Chem Chem Phys 2009; 11:317-23. [DOI: 10.1039/b813232a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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34
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Burdzinski G, Marciniak B. Photoinduced ultrafast ring-opening reaction in trithianes in solution. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.09.055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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35
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Wang J, Burdzinski G, Kubicki J, Platz MS. Ultrafast UV−Vis and IR Studies of p-Biphenylyl Acetyl and Carbomethoxy Carbenes. J Am Chem Soc 2008; 130:11195-209. [DOI: 10.1021/ja803096p] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jin Wang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Gotard Burdzinski
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Jacek Kubicki
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Matthew S. Platz
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
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36
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Wang J, Zhang Y, Kubicki J, Platz MS. Ultrafast studies of some diarylcarbenes. Photochem Photobiol Sci 2008; 7:552-7. [PMID: 18465011 DOI: 10.1039/b800041g] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photochemistry of 5-diazo-10,11-dihydrodibenzo[a,d]diazocycloheptene (DDBC) and 9-diazoanthrone (DAN) were studied by ultrafast time resolved techniques. The excited states of these diazo compounds were observed by UV-Vis spectroscopy and were found to decay in 300 fs. The diazo excited state decays led to the appearance and first direct observation of singlet 5-diazo-10,11-dihydrodibenzo[a,d]cycloheptenylidene (DBC) and 9-anthronylidene (AN). The dynamics of DBC and AN were studied in acetonitrile, cyclohexane and methanol. The lifetimes of (1)DBC are 83 ps and 72 ps in acetonitrile and cyclohexane, respectively. The lifetime of (1)DBC shortens to 9 ps in methanol due to rapid reaction with the solvent. The lifetime of (1)AN is 87 ps and 66 ps in acetonitrile and cyclohexane, respectively. In methanol, the lifetime of (1)AN cannot be determined due to spectral overlap of (1)AN and cation ANH+. The decays of (1)DBC and (1)AN are controlled by intersystem crossing (ISC) in acetonitrile and cyclohexane and the rates of ISC of (1)DBC or (1)AN are similar in these two solvents. This differs from the solvent dependence of other diarylcarbene intersystem crossing rates. This is attributed to the relatively large singlet-triplet (S-T) gaps of these carbenes and this factor dominates the influence of solvent.
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Affiliation(s)
- Jin Wang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
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Fujiwara H, Terazima M, Kimura Y. Transient grating study on vibrational energy relaxation of bridged azulene–anthracene’s. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.01.067] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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38
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Wang J, Kubicki J, Gustafson TL, Platz MS. The Dynamics of Carbene Solvation: An Ultrafast Study of p-Biphenylyltrifluoromethylcarbene. J Am Chem Soc 2008; 130:2304-13. [DOI: 10.1021/ja077705m] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jin Wang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Jacek Kubicki
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Terry L. Gustafson
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
| | - Matthew S. Platz
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio, 43210, and the Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
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Middleton CT, Cohen B, Kohler B. Solvent and Solvent Isotope Effects on the Vibrational Cooling Dynamics of a DNA Base Derivative. J Phys Chem A 2007; 111:10460-7. [PMID: 17910423 DOI: 10.1021/jp0740595] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vibrational cooling by 9-methyladenine was studied in a series of solvents by femtosecond transient absorption spectroscopy. Signals at UV and near-UV probe wavelengths were assigned to hot ground state population created by ultrafast internal conversion following electronic excitation by a 267 nm pump pulse. A characteristic time for vibrational cooling was determined from bleach recovery signals at 250 nm. This time increases progressively in H2O (2.4 ps), D2O (4.2 ps), methanol (4.5 ps), and acetonitrile (13.1 ps), revealing a pronounced solvent effect on the dissipation of excess vibrational energy. The trend also indicates that the rate of cooling is enhanced in solvents with a dense network of hydrogen bonds. The faster rate of cooling seen in H2O vs D2O is noteworthy in view of the similar hydrogen bonding and macroscopic thermal properties of both liquids. We propose that the solvent isotope effect arises from differences in the rates of solute-solvent vibrational energy transfer. Given the similarities of the vibrational friction spectra of H2O and D2O at low frequencies, the solvent isotope effect may indicate that a considerable portion of the excess energy decays by exciting relatively high frequency (>/=700 cm-1) solvent modes.
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Affiliation(s)
- Chris T Middleton
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
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Pritchina EA, Gritsan NP, Burdzinski GT, Platz MS. Study of Acyl Group Migration by Femtosecond Transient Absorption Spectroscopy and Computational Chemistry. J Phys Chem A 2007; 111:10483-9. [PMID: 17894474 DOI: 10.1021/jp073707h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The primary photophysical and photochemical processes in the photochemistry of 1-acetoxy-2-methoxyanthraquinone (1a) were studied using femtosecond transient absorption spectroscopy. Excitation of 1a at 270 nm results in the population of a set of highly excited singlet states. Internal conversion to the lowest singlet npi* excited state, followed by an intramolecular vibrational energy redistribution (IVR) process, proceeds with a time constant of 150 +/- 90 fs. The 1npi* excited state undergoes very fast intersystem crossing (ISC, 11 +/- 1 ps) to form the lowest triplet pipi* excited state which contains excess vibrational energy. The vibrational cooling occurs somewhat faster (4 +/- 1 ps) than ISC. The primary photochemical process, migration of acetoxy group, proceeds on the triplet potential energy surface with a time constant of 220 +/- 30 ps. The transient absorption spectra of the lowest singlet and triplet excited states of 1a, as well as the triplet excited state of the product, 9-acetoxy-2-methoxy-1,10-anthraquinone (2a), were detected. The assignments of the transient absorption spectra were supported by time-dependent DFT calculations of the UV-vis spectra of the proposed intermediates. All of the stationary points for acyl group migration on the triplet and ground state singlet potential energy surfaces were localized, and the influence of the acyl group substitution on the rate constants of the photochemical and thermal processes was analyzed.
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Affiliation(s)
- Elena A Pritchina
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
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Wang J, Kubicki J, Burdzinski G, Hackett JC, Gustafson TL, Hadad CM, Platz MS. Early Events in the Photochemistry of 2-Naphthyl Azide from Femtosecond UV/Vis Spectroscopy and Quantum Chemical Calculations: Direct Observation of a Very Short-Lived Singlet Nitrene. J Org Chem 2007; 72:7581-6. [PMID: 17824713 DOI: 10.1021/jo070865w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Exposure of 2-naphthyl azide in acetonitrile at ambient temperature to femtosecond pulses of 266 nm light produces a transient absorption with maxima at 350 and 420 nm. The carrier of the 350 nm band decays more rapidly than that of the 420 nm band which has a lifetime of 1.8 ps. Analogous experiments with 1-chloro-2-naphthyl azide in methanol allow the assignment of the 350 nm band to a singlet excited state of 2-naphthyl azide and the carrier of the 420 nm band to singlet 2-naphthylnitrene. This reactive intermediate has the shortest lifetime of any singlet nitrene observed to date and is a true reactive intermediate. Computational studies at the RI-CC2 level of theory support these conclusions and suggest that initial excitation populates the S2 state of 2-naphthyl azide. The S2 state, best characterized as a pi --> (pi*, aryl) transition, has a geometry similar to S0. S2 of 2-naphthyl azide can then populate the S1 state, a pi --> (in-plane, pi*, azide) excitation, and in the S1 state, electron density is depleted along the proximal N-N bond. S1 is dissociative along that N-N coordinate to form the singlet nitrene, and with a barrier of only approximately 5 kcal/mol for N2 extrusion.
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Affiliation(s)
- Jin Wang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
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Fukuda M, Kajimoto O, Terazima M, Kimura Y. Application of the transient grating method to the investigation of the photo-thermalization process of malachite green in room temperature ionic liquids. J Mol Liq 2007. [DOI: 10.1016/j.molliq.2006.12.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Wang J, Burdzinski G, Gustafson TL, Platz MS. Ultrafast Study of p-Biphenylyldiazoethane. The Chemistry of the Diazo Excited State and the Relaxed Carbene. J Am Chem Soc 2007; 129:2597-606. [PMID: 17290992 DOI: 10.1021/ja067213u] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ultrafast photolysis of p-biphenylyldiazoethane (BDE) produces an excited state of the diazo compound in acetonitrile, cyclohexane, and methanol with lambdamax = 490 nm and lifetimes of less than 300 fs. The decay of the diazo excited state correlates with the growth of singlet carbene absorption at 360 nm. The optical yields of diazo excited states produced by photolysis of p-biphenylyldiazomethane (BDM) and BDE are the same; however, the optical yield of singlet p-biphenylylmethylcarbene (1BpCMe) is 30-40% less than that of p-biphenylylcarbene (1BpCH) in all three solvents. The results are explained by rearrangement in the excited state (RIES) of BDE to form p-vinylbiphenyl (VB) in parallel with extrusion of nitrogen to form 1BpCMe in reduced yield. This interpretation is consistent with product studies (ethanol-OD in cyclohexane) which indicate that there is an approximately 25% yield of VB that is formed by a mechanism that bypasses the relaxed singlet carbene. The decay of 1BpCMe is biexponential, and that of 1BpCH is monoexponential. This is attributed either to efficient relaxation of vibrationally excited 1BpCMe by 1,2 migration of hydrogen to form VB (minor) or to the increased number of low-frequency vibrational modes provided by the methyl group (major). A methyl group retards the rate of intersystem crossing (ISC), relative to a hydrogen atom, and ISC is more rapid in nonpolar solvents. Reaction of 1BpCMe with methanol is much faster than spin equilibration. Both the lifetime of 1BpCMe and 1BpCH are the same in cyclohexane and in cyclohexane-d12. This demonstrates that spin equilibration is faster than reaction of either carbene with the solvent. The lifetimes of 1BpCMe and 1BpCMe-d3 are the same in cyclohexane. This indicates that 1,2 hydrogen migration of 1BpCMe to form VB is slower than spin equilibration in cyclohexane. In acetonitrile, however, the lifetime of 1BpCMe-d3 is 1.5 times longer than that of 1BpCMe in the same solvent. Thus, in acetonitrile, where ISC is slow, the rate of 1,2 hydrogen shift of 1BpCMe is competitive with ISC. In cyclohexene, the lifetime of 1BpCH is shortened relative to that in cyclohexane. The lifetime of 1BpCMe is the same in cyclohexene and cyclohexane. The data indicate that spin relaxation is slow relative to reaction of 1BpCH with neat alkene but that spin relaxation is fast for 1BpCMe relative to reaction with neat cyclohexene.
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Affiliation(s)
- Jin Wang
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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Wang J, Burdzinski G, Kubicki J, Platz MS, Moss RA, Fu X, Piotrowiak P, Myahkostupov M. Ultrafast Spectroscopic Study of the Photochemistry and Photophysics of Arylhalodiazirines: Direct Observation of Carbene and Zwitterion Formation. J Am Chem Soc 2006; 128:16446-7. [PMID: 17177362 DOI: 10.1021/ja067205d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ultrafast photolysis (lambdaex = 270, 350, or 360 nm) of bromophenyl, chlorophenyl, fluorophenyl, and fluoro-para-trifluoromethylphenyl diazirines produces transient species which absorb broadly in the UV and visible regions. Transient decay can be fit to either mono- or biexponential functions (tau1 approximately 0.3-10 ps, tau2 approximately 10-350 ps; dependent on solvent and halogen). Fluoro- and chlorophenylcarbene are formed within the time resolution of the spectrometer (300 fs, 270 nm excitation). Bromophenyl diazirine decay (270 nm excitation) correlates with the growth of bromophenylcarbene. Solvent and substituent effects on the slower decays of the transient absorptions are consistent with assigning the carriers of transient absorption in the visible region to ring-opened zwitterionic species.
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Affiliation(s)
- Jin Wang
- Department of Chemistry, The Ohio State University, Columbus, OH 43210, USA
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Burdzinski G, Hackett JC, Wang J, Gustafson TL, Hadad CM, Platz MS. Early Events in the Photochemistry of Aryl Azides from Femtosecond UV/Vis Spectroscopy and Quantum Chemical Calculations. J Am Chem Soc 2006; 128:13402-11. [PMID: 17031952 DOI: 10.1021/ja061520i] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photochemistry of para- and ortho-biphenylyl azides and 1-naphthyl azide was studied by ultrafast spectroscopy. In every case, the singlet azide second excited states were observed by transient absorption spectroscopy and were found to have lifetimes of hundreds of femtoseconds. The decay of the S(2) states of the azides was accompanied by the growth of transient absorption of the corresponding singlet nitrenes. The intermediate S(1) state of the azides could not be observed due to its low instantaneous concentration resulting from fast fragmentation and nitrene formation. Quantum chemical calculations predict that the S(2) state of the azide is bound and that there is a much lower barrier toward arylnitrene formation from the S(1) state of the azide. Vibrational cooling of para-biphenylnitrene (11 ps) was experimentally observed. The lifetime of singlet ortho-biphenylnitrene was 16 ps in acetonitrile and was not affected by perdeuteration of the aryl ring. The lifetime of singlet 1-naphthylnitrene is 12 ps in acetonitrile at ambient temperature.
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Affiliation(s)
- Gotard Burdzinski
- Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, 85 Umultowska, Poznan 61-614, Poland
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Hare PM, Crespo-Hernández CE, Kohler B. Solvent-Dependent Photophysics of 1-Cyclohexyluracil: Ultrafast Branching in the Initial Bright State Leads Nonradiatively to the Electronic Ground State and a Long-Lived1nπ* State. J Phys Chem B 2006; 110:18641-50. [PMID: 16970494 DOI: 10.1021/jp064714t] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The modified nucleic acid base, 1-cyclohexyluracil, was studied by femtosecond transient absorption spectroscopy in protic and aprotic solvents of varying polarity. UV excitation at 267 nm populates the lowest-energy bright state, a (1)pipi* state, which has a lifetime of 120-270 fs, depending on the solvent. In all solvents, this initial bright state population bifurcates with approximately 60% undergoing subpicosecond nonradiative decay to the electronic ground state and the remaining population branching to a singlet dark state. The latter absorbs between 340 and 450 nm. The latter state is assigned to the lowest-energy (1)npi* state. It decays to the electronic ground state with a lifetime that varies from 26 ps in water to at least several nanoseconds in aprotic solvents. The results suggest that the two nonradiative decay pathways identified for photoexcited uracil in recent quantum chemical calculations (Matsika, S. J. Phys. Chem. A. 2004, 108, 7584) are simultaneously operative in a wide variety of solvent environments. The lowest-energy triplet state was also detected by transient absorption. The triplet population appears in a few picoseconds and is not formed from the thermalized (1)npi* state. It is suggested that high spin-orbit coupling is found only along initial segments of the nonradiative decay pathways. Efficient intersystem crossing prior to vibrational cooling offers a possible explanation for the wavelength-dependent triplet yields seen in single DNA bases.
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Affiliation(s)
- Patrick M Hare
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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47
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Wang J, Burdzinski G, Gustafson TL, Platz MS. Ultrafast Study ofp-Biphenylyldiazomethane andp-Biphenylylcarbene. J Org Chem 2006; 71:6221-8. [PMID: 16872208 DOI: 10.1021/jo061029+] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
p-Biphenylyldiazomethane was excited by femtosecond pulses of UV light in acetonitrile, in cyclohexane, and in methanol. Ultrafast photolysis produces a singlet excited state of p-biphenylyldiazomethane with lambdamax = 490 nm, and lifetimes of less than 300 fs in acetonitrile, in cyclohexane, and in methanol. The decay of the excited state is accompanied by the growth of transient absorption with lambdamax = 360 nm. The carrier of this transient absorption is attributed to singlet p-biphenylylcarbene, a result that is consistent with the predictions of TD-DFT calculations. The singlet carbene lifetimes are 200 and 77 ps in acetonitrile and cyclohexane, respectively, and are controlled by intersystem crossing to the lower energy triplet state. The transient absorption does not decay to baseline in acetonitrile, because of the formation of nitrile ylide. The equilibrium mixture of singlet and triplet p-biphenylylcarbene reacts with acetonitrile to form a nitrile ylide (lambdamax = 370 nm), and with cyclohexane by C-H insertion 1-20 ns after the laser pulse. The singlet carbene lifetime is only 7.9 ps in methanol, owing to a rapid reaction with the solvent. Reaction with the solvent gives rise, in part, to a p-biphenylylbenzyl cation (lambdamax = 450 nm, tau = 6.3 ps) in methanol.
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Affiliation(s)
- Jin Wang
- Department of Chemistry, Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
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Abstract
▪ Abstract Modern ultrafast spectroscopic techniques provide new opportunities to study chemical reaction dynamics in liquids and hold the possibility of obtaining much of the same detailed information available in gases. Vibrational energy transfer studies are the most advanced of the investigations and demonstrate that it is possible to observe state-specific pathways of energy flow within a vibrationally excited molecule (intramolecular vibrational relaxation) and into the surrounding solvent molecules (intermolecular energy transfer). Energy transfer in liquids and gases share many common aspects, but the presence of the solvent also alters the relaxation in both obvious and subtle ways. Photodissociation is amenable to similarly detailed study in liquids, and there are informative new measurements. Bimolecular reactions have received the least attention in state-resolved measurements in liquids, but the means to carry them much further now exist. Studying photodissociation and bimolecular reaction of molecules prepared with initial vibrational excitation in liquids is a realistic, but challenging, goal.
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Affiliation(s)
- Christopher G Elles
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
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Grimm C, Kandratsenka A, Wagener P, Zerbs J, Schroeder J. Photoinduced Isomerization Kinetics of Diiodomethane in Supercritical Fluid Solution: Local Density Effects. J Phys Chem A 2006; 110:3320-9. [PMID: 16509658 DOI: 10.1021/jp055608e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The density dependence of diiodomethane photoinduced isomerization in supercritical (sc) CO2, CHF3, and C2H6 was investigated by transient absorption spectroscopy, covering a fluid density range from 0.7 to 2.5 (in reduced units). The solvent-caged photoproduct iso-diiodomethane is formed even at the lowest density, and its yield increases about 4-fold over the whole range. At the same time, isomer formation rate constants increase by roughly an order of magnitude and show little variation between CO2, C2H6, and CHF3. Furthermore, the formation rate constant decreases significantly with increasing excitation energy. We propose an isomer formation mechanism involving a rapidly established preequilibrium between a solvent-caged iodine atom-methyliodide radical pair and a loosely bound iodine-methyliodide radical complex, from which the reaction subsequently proceeds to the isomer. The latter step seems to be controlled by collisional stabilization of the initially hot radical moiety, as the formation rate constant increases linearly with sc solvent viscosity. The model predicts a quadratic dependence of relative isomer yield on fluid density. A corresponding correlation is found with the local fluid density, calculated via solute-solvent radial distribution functions obtained from molecular dynamics (MD) simulations.
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Affiliation(s)
- Christian Grimm
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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KIMURA Y, AMITA F, FUJISAWA T. Non-linear Laser Spectroscopy in Supercritical Fluids. ACTA ACUST UNITED AC 2006. [DOI: 10.4131/jshpreview.16.87] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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