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Ghosh R, Datta S, Mora AK, Modak B, Nath S, Palit DK. Dynamics of hydrogen bond reorganization in the S1(ππ*) state of 9-Anthracenecarboxaldehyde. J Photochem Photobiol A Chem 2023. [DOI: 10.1016/j.jphotochem.2022.114379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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2
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Zhao J, Jin B, Dong H. Decoding Solvent Polarity Related Excited State Behaviors for the Novel Amino NH‐type 3TfAPI Fluorophore. ChemistrySelect 2022. [DOI: 10.1002/slct.202203254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Jinfeng Zhao
- College of Physical Science and Technology Shenyang Normal University Shenyang 110034 China
- Institute of Molecular Sciences and Engineering Institute of Frontier and Interdisciplinary Science Shandong University Qingdao 266237 China
| | - Bing Jin
- Institute of Molecular Sciences and Engineering Institute of Frontier and Interdisciplinary Science Shandong University Qingdao 266237 China
| | - Hao Dong
- Hebei Key Laboratory of Physics and Energy Technology Department of Mathematics and Physics North China Electric Power University Baoding 071003 China
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3
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Intramolecular Charge Transfer of Curcumin and Solvation Dynamics of DMSO Probed by Time-Resolved Raman Spectroscopy. Int J Mol Sci 2022; 23:ijms23031727. [PMID: 35163647 PMCID: PMC8835799 DOI: 10.3390/ijms23031727] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/25/2022] [Accepted: 01/31/2022] [Indexed: 02/04/2023] Open
Abstract
Intramolecular charge transfer (ICT) of curcumin in dimethyl sulfoxide (DMSO) solution in the excited state was investigated by femtosecond electronic and vibrational spectroscopy. Excited-state Raman spectra of curcumin in the locally-excited and charge-transferred (CT) state of the S1 excited state were separated due to high temporal (<50 fs) and spectral (<10 cm−1) resolutions of femtosecond stimulated Raman spectroscopy. The ultrafast (0.6–0.8 ps) ICT and subsequent vibrational relaxation (6–9 ps) in the CT state were ubiquitously observed in the ground- and excited-state vibrational modes of the solute curcumin and the νCSC and νS=O modes of solvent DMSO. The ICT of curcumin in the excited state was preceded by the disruption of the solvation shells, including the breakage of hydrogen bonding between curcumin and DMSO molecules, which occurs at the ultrafast (20–50 fs) time scales.
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4
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Savenko ES, Kostjukov VV. Coumarin 102 excitation in aqueous media: contributions of vibronic coupling and hydration. NEW J CHEM 2022. [DOI: 10.1039/d1nj05615h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For the first time, vibronic coupling was considered when analyzing the excitation of coumarin C102.
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Affiliation(s)
- Evgeniy S. Savenko
- Physics Department, Sevastopol State University, Universitetskaya st., 33, Sevastopol, 299053, Crimea
| | - Victor V. Kostjukov
- Physics Department, Sevastopol State University, Universitetskaya st., 33, Sevastopol, 299053, Crimea
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5
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Jeon K, Jen M, Lee S, Jang T, Pang Y. Intramolecular Charge Transfer of 1-Aminoanthraquinone and Ultrafast Solvation Dynamics of Dimethylsulfoxide. Int J Mol Sci 2021; 22:ijms222111926. [PMID: 34769357 PMCID: PMC8584543 DOI: 10.3390/ijms222111926] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/29/2021] [Accepted: 11/01/2021] [Indexed: 11/16/2022] Open
Abstract
The intramolecular charge transfer (ICT) of 1-aminoanthraquinone (AAQ) in the excited state strongly depends on its solvent properties, and the twisted geometry of its amino group has been recommended for the twisted ICT (TICT) state by recent theoretical works. We report the transient Raman spectra of AAQ in a dimethylsulfoxide (DMSO) solution by femtosecond stimulated Raman spectroscopy to provide clear experimental evidence for the TICT state of AAQ. The ultrafast (~110 fs) TICT dynamics of AAQ were observed from the major vibrational modes of AAQ including the νC-N + δCH and νC=O modes. The coherent oscillations in the vibrational bands of AAQ strongly coupled to the nuclear coordinate for the TICT process have been observed, which showed its anharmonic coupling to the low frequency out of the plane deformation modes. The vibrational mode of solvent DMSO, νS=O showed a decrease in intensity, especially in the hydrogen-bonded species of DMSO, which clearly shows that the solvation dynamics of DMSO, including hydrogen bonding, are crucial to understanding the reaction dynamics of AAQ with the ultrafast structural changes accompanying the TICT.
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Karbalaei Khani S, Geissler B, Engelage E, Nuernberger P, Hättig C. Tracing absorption and emission characteristics of halogen-bonded ion pairs involving halogenated imidazolium species. Phys Chem Chem Phys 2021; 23:7480-7494. [PMID: 33876108 DOI: 10.1039/d1cp00009h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We investigate how the absorption and fluorescence of halogenated imidazolium compounds in acetonitrile solution is influenced by the presence of counterions and the ability to act as halogen-bond donors. Experimental measurements and quantum chemical calculations with correlated wavefunction methods are applied to study three monodentate halogen-bond complexes of iodo-imidazolium, iodo-benzimidazolium and bromo-benzimidazolium cations with triflate counterions, and a bidentate complex of bis(iodo-benzimidazolium) dications with chloride as counterion. The three monodentate complexes with triflate counterions relax after photoexcitation to minima on the S1 potential energy surface where the C-I bond and the IO halogen bond are partially broken. For the bidentate complex with the smaller chloride counterion the halogen-bond interaction stays intact in the S1 minimum that is reached by relaxation from the Franck-Condon point. In a complementing experimental approach, stationary absorption and emission as well as transient fluorescence spectra are recorded for iodo- and bromo-benzimidazolium in acetonitrile. Variation of the counterion, substitution of the iodine by bromine, hydrogen, or methyl, and the comparison to theory allows the identification of spectroscopic signatures and photoinduced dynamics associated with ion-pairing.
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7
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Fresch E, Peruffo N, Trapani M, Cordaro M, Bella G, Castriciano MA, Collini E. The effect of hydrogen bonds on the ultrafast relaxation dynamics of a BODIPY dimer. J Chem Phys 2021; 154:084201. [PMID: 33639732 DOI: 10.1063/5.0038242] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The influence of hydrogen bonds (H-bonds) in the structure, dynamics, and functionality of biological and artificial complex systems is the subject of intense investigation. In this broad context, particular attention has recently been focused on the ultrafast H-bond dependent dynamical properties in the electronic excited state because of their potentially dramatic consequences on the mechanism, dynamics, and efficiency of photochemical reactions and photophysical processes of crucial importance for life and technology. Excited-state H-bond dynamics generally occur on ultrafast time scales of hundreds of femtoseconds or less, making the characterization of associated mechanisms particularly challenging with conventional time-resolved techniques. Here, 2D electronic spectroscopy is exploited to shed light on this still largely unexplored dynamic mechanism. An H-bonded molecular dimer prepared by self-assembly of two boron-dipyrromethene dyes has been specifically designed and synthesized for this aim. The obtained results confirm that upon formation of H-bonds and the dimer, a new ultrafast relaxation channel is activated in the ultrafast dynamics, mediated by the vibrational motions of the hydrogen donor and acceptor groups. This relaxation channel also involves, beyond intra-molecular relaxations, an inter-molecular transfer process. This is particularly significant considering the long distance between the centers of mass of the two molecules. These findings suggest that the design of H-bonded structures is a particularly powerful tool to drive the ultrafast dynamics in complex materials.
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Affiliation(s)
- Elisa Fresch
- Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Nicola Peruffo
- Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Mariachiara Trapani
- CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, c/o Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, V.le F. Stagno D'Alcontres 31, 98166 Messina, Italy
| | - Massimiliano Cordaro
- Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, V.le F. Stagno D'Alcontres 31, 98166 Messina, Italy
| | - Giovanni Bella
- Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, V.le F. Stagno D'Alcontres 31, 98166 Messina, Italy
| | - Maria Angela Castriciano
- CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, c/o Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, V.le F. Stagno D'Alcontres 31, 98166 Messina, Italy
| | - Elisabetta Collini
- Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, 35131 Padova, Italy
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8
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Jen M, Jeon K, Lee S, Hwang S, Chung WJ, Pang Y. Ultrafast intramolecular proton transfer reactions and solvation dynamics of DMSO. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2019; 6:064901. [PMID: 31867409 PMCID: PMC6920016 DOI: 10.1063/1.5129446] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 11/21/2019] [Indexed: 05/27/2023]
Abstract
Ultrafast intramolecular proton transfers of 1,2-dihydroxyanthraquinone (alizarin-h2) and its deuterated product (alizarin-d2) in dimethyl sulfoxide (DMSO) have been investigated by femtosecond stimulated Raman spectroscopy. The population dynamics in the solute vibrational mode of νC=O and the coherent oscillations observed in all of the skeletal vibrational modes νC=O and νC=C clearly showed the ultrafast excited-state intramolecular proton transfer dynamics of 110 and 170 fs for alizarin-h2 and alizarin-d2, respectively. Interestingly, we have observed that the solvent vibrational modes νS=O and νCSC may also represent ultrafast structural dynamics at the frequencies for its "free" or "aggregated" species. From the kinetic analysis of the νS=O and νCSC modes of DMSO, the ultrafast changes in the solvation or intermolecular interactions between DMSO molecules initiated by the structural changes of solute molecules have been thoroughly investigated. We propose that the solvent vibrational modes νS=O and νCSC of DMSO can be used as a "sensor" for ultrafast chemical reactions accompanying the structural changes and subsequent solute-solvent interactions.
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Affiliation(s)
| | | | - Sebok Lee
- Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, South Korea
| | - Sunjoo Hwang
- Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, South Korea
| | - Won-jin Chung
- Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, South Korea
| | - Yoonsoo Pang
- Department of Chemistry, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, South Korea
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9
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Thongyod W, Buranachai C, Pengpan T, Punwong C. Fluorescence quenching by photoinduced electron transfer between 7-methoxycoumarin and guanine base facilitated by hydrogen bonds: an in silico study. Phys Chem Chem Phys 2019; 21:16258-16269. [PMID: 31304496 DOI: 10.1039/c9cp02037c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this study, the effects of hydrogen bond (H-bond) formation on fluorescence quenching of 7-methoxycoumarin (7MC) via photo-induced electron transfer from a guanine base (Gua) are investigated using a combined quantum mechanics/molecular mechanics simulation. The electronic structure is calculated by the floating occupation molecular orbital complete active space configuration interaction modification on a semiempirical method. Then the full multiple spawning method is employed for the dynamics simulations on multiple electronic states. The methods employed here are validated by simulating direct dynamics of 7MC (without Gua) and compared with available experimental results. Our computational results are in good agreement with the previously reported experimental results in terms of spectroscopic properties of 7MC. In the case of a H-bonded 7MC-Gua complex, the results from constrained dynamics simulations and single-point calculations suggest that the electron transfer occurs on the second excited state and it depends not only on the H-bond length but also on the intermolecular planarity between 7MC and Gua. Moreover, a proton coupled electron transfer can occur at ≈1 Å of H-bond length, where a proton from Gua is also transferred together with the electron to 7MC. The obtained simulations are expected to be greatly beneficial for designing effective fluorescently labeled nucleotide probes as well as providing information for precise fluorescence signal interpretation.
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Affiliation(s)
- Wutthinan Thongyod
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand. and Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Songkhla 90112, Thailand
| | - Chittanon Buranachai
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand. and Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Songkhla 90112, Thailand
| | - Teparksorn Pengpan
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand.
| | - Chutintorn Punwong
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand.
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10
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Ghosh R, Mora AK, Nath S. Disentangling Time Scales of Vibrational Cooling, Solvation, and Hydrogen Bond Reorganization Dynamics Using Ultrafast Transient Infrared Spectroscopy of Formylperylene. J Phys Chem B 2019; 123:4408-4414. [DOI: 10.1021/acs.jpcb.9b01920] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rajib Ghosh
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Aruna K. Mora
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Sukhendu Nath
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
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11
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Jagadeesha K, Ramu YL, Ramegowda M, Lokanath NK. Excited state hydrogen atom transfer in micro-solvated dicoumarol: A TDDFT/EFP1 study. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2019; 208:325-330. [PMID: 30342342 DOI: 10.1016/j.saa.2018.10.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 10/01/2018] [Accepted: 10/11/2018] [Indexed: 06/08/2023]
Abstract
Ground (S0) and excited (S1) state properties of dicoumarol (DC) are investigated by applying density functional theory (DFT) and time dependent DFT (TDDFT) interfacing with the effective fragment potential (EFP) method of solvation. Benzene and pyrone rings of the each 4-hydroxy coumarin (4HC) moiety are in a plane and these planes are twisted by 180° with respect to each other. Two intra-molecular hydrogen bonds (HB) CO⋯HO exist between the carbonyl (CO) and hydroxyl (OH) groups of different 4HC moieties (4HC-1 and 4HC-2). DC(H2O)3 complex is formed using the original EFP model (EFP1). Four inter-molecular HBs are established by the carbonyl and hydroxyl oxygen atoms of 4HC-1 and 4HC-2 moieties; two HBs with two solvent molecules on one side of the complex and other two HBs with one solvent molecule at the other side. In S1 state, the hydrogen atomtransfer takes place only from the hydroxyl group of 4HC-1 to the carbonyl group of 4HC-2. The natural charge analysis and the modification of HBs manifest the intra-molecular charge transfer (ICT) from one 4HC moiety to another. Theoretical and experimental studies of the absorption spectra, and the theoretical study of potential energy curves of OH bonds at both S0 and S1 states affirm the hydrogen atom transfer from the hydroxyl group of 4HC-1 to the carbonyl group of 4HC-2 moiety.
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12
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Singh AK, Das S, Karmakar A, Kumar A, Datta A. Solvation and hydrogen bonding aided efficient non-radiative deactivation of polar excited state of 5-aminoquinoline. Phys Chem Chem Phys 2018; 20:22320-22330. [PMID: 30124696 DOI: 10.1039/c8cp03590c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The mechanism of efficient fluorescence quenching of 5-aminoquinoline in alcoholic solvents.
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Affiliation(s)
- Avinash Kumar Singh
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
| | - Sharmistha Das
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
| | - Abhoy Karmakar
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
| | - Anuj Kumar
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
| | - Anindya Datta
- Department of Chemistry
- Indian Institute of Technology Bombay
- Mumbai 400076
- India
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13
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Ghosh R, Mora AK, Nath S, Palit DK. Ultrafast Dynamics of Hydrogen Bond Breaking and Making in the Excited State of Fluoren-9-one: Time-Resolved Visible Pump–IR Probe Spectroscopic Study. J Phys Chem B 2017; 121:1068-1080. [DOI: 10.1021/acs.jpcb.6b11293] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rajib Ghosh
- Radiation and Photochemistry
Division, Bhabha Atomic Research Centre, Mumbai-400094, India
| | - Aruna K. Mora
- Radiation and Photochemistry
Division, Bhabha Atomic Research Centre, Mumbai-400094, India
| | - Sukhendu Nath
- Radiation and Photochemistry
Division, Bhabha Atomic Research Centre, Mumbai-400094, India
| | - Dipak K. Palit
- Radiation and Photochemistry
Division, Bhabha Atomic Research Centre, Mumbai-400094, India
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14
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Ramegowda M, Ranjitha KN, Deepika TN. Exploring excited state properties of 7-hydroxy and 7-methoxy 4-methycoumarin: a combined time-dependent density functional theory/effective fragment potential study. NEW J CHEM 2016. [DOI: 10.1039/c5nj02917a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen bond dynamics, C–OH bond contracting, O–H bond stretching and O–H⋯O HB strengthening reveal the ESHT in 4MU at the S1state.
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15
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Barman N, Sahu K. Anomalous modulation of photoinduced electron transfer of coumarin 102 in aniline-dimethylaniline mixture: dominant role of hydrogen bonding. Phys Chem Chem Phys 2015; 16:27096-103. [PMID: 25388669 DOI: 10.1039/c4cp04441j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In a previous study, we reported a striking observation that photoinduced electron transfer (PET) from aniline (AN) to photoexcited coumarin 102 (C102) can be accelerated by adding an inert component (cyclohexane or toluene) to the neat electron donor solvent AN (Phys. Chem. Chem. Phys., 2014, 16, 6159-6166). The H-bond linking the electron donor (D, AN) and the acceptor (A, C102) was proposed to dictate the PET process. To account for the unusual variation of quenching pattern with AN mole fraction, two possible reasons were cited - (1) the D-A (AN-C102) H-bonding may be modulated due to change in polarity of the medium or (2) the additional D-D (AN-AN) H-bonding may restrain the D-A H-bonding to adjust optimally for the PET. Here, we investigate the PET of C102 in an AN-dimethylaniline (DMA) mixture to negate the polarity variation. Since, both AN and DMA have similar polarities, the polarity of the mixture should remain invariant at all compositions. Nevertheless, we found that the fluorescence quantum yield and lifetime of C102 in the mixtures follows a similar unusual trend as observed earlier in the AN-toluene or AN-cyclohexane mixtures; it first decreases up to a particular mole fraction (XD) of the H-bond donor AN and, thereafter, increases on further enrichment of the donor. The observed PET modulation may be rationalized by considering efficient PET in the 1 : 1 H-bonded C102-AN complex but less efficient PET in higher order C102-(AN)n≥2 complexes, where additional D-D (AN-AN) H-bonding may influence the key C102-AN H-bonding and thus inhibit the PET process.
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Affiliation(s)
- Nabajeet Barman
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
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16
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Barman N, Singha D, Sahu K. Faster photoinduced electron transfer in a diluted mixture than in a neat donor solvent: effect of excited-state H-bonding. Phys Chem Chem Phys 2015; 16:6159-66. [PMID: 24562294 DOI: 10.1039/c4cp00025k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In a neat electron-donating solvent (in this case aniline), photoinduced electron transfer (PET) from the solvent to an excited acceptor (e.g. a coumarin fluorophore) may be anticipated to be the most efficient because of the close contact of the acceptor with many donors. Addition of an inert component would most likely retard the PET process by replacing some donors from the neighbourhood of the acceptors. Surprisingly, we found dramatic acceleration of PET (6-10 fold enhancement compared to neat aniline), for coumarin 102 (C102) dissolved in a binary mixture of aniline and an inert solvent (cyclohexane or toluene). The PET induced fluorescence follows an anomalous trend against the mole fraction of aniline (XAN); first quenches up to certain XAN (0.075 for cyclohexane; 0.13 for toluene), thereafter, enhances with increase in XAN. Although the non-interacting component cannot directly participate in the PET process, it may modulate C102-aniline H-bonding association by changing the polarity of the medium or by disrupting the aniline-aniline H-bond. The study clearly illustrates the dominant role of hydrogen bonding in activating the electron transfer rate where standard thermodynamics predicts very weak donor-acceptor interaction.
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Affiliation(s)
- Nabajeet Barman
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
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17
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Fukui Y, Ohta K, Tominaga K. Vibrational dynamics of the CO stretching of 9-fluorenone studied by visible-pump and infrared-probe spectroscopy. Faraday Discuss 2015; 177:65-75. [DOI: 10.1039/c4fd00169a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We studied the effects of hydrogen bonds on the vibrational structures and vibrational dynamics of the CO stretching mode of 9-fluorenone (FL) in the electronically excited state in aprotic and protic solvents using sub-picosecond visible-pump and IR-probe spectroscopy. The transient IR spectrum of the CO stretching band in methanol-d4 has two bands at 1529.9 cm−1 and 1543.4 cm−1, which are assigned to an FL-solvent complex and free FL, respectively. In the aprotic solvents, the CO stretching bands show blue-shifts in time. This shift is due to vibrational cooling, which is derived from anharmonic couplings with some low-frequency modes. Interestingly, a red-shift is observed at later delay time for the band at 1529.9 cm−1 in methanol-d4. A possible mechanism of this spectral shift is related to the hydrogen bond dynamics between the solute and solvent.
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Affiliation(s)
- Yuki Fukui
- Department of Chemistry
- Graduate School of Science
- Kobe University
- Molecular Photoscience Research Center
- Kobe University
| | - Kaoru Ohta
- Department of Chemistry
- Graduate School of Science
- Kobe University
- Molecular Photoscience Research Center
- Kobe University
| | - Keisuke Tominaga
- Department of Chemistry
- Graduate School of Science
- Kobe University
- Molecular Photoscience Research Center
- Kobe University
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18
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Barman N, Sahu K. Reduced fluorescence quenching of coumarin 102 at higher phenol mole fractions in cyclohexane–phenol and anisole–phenol solvent mixtures: role of competitive hydrogen bonding. RSC Adv 2014. [DOI: 10.1039/c4ra11251b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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19
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Hessz D, Hégely B, Kállay M, Vidóczy T, Kubinyi M. Solvation and protonation of coumarin 102 in aqueous media: a fluorescence spectroscopic and theoretical study. J Phys Chem A 2014; 118:5238-47. [PMID: 24945906 DOI: 10.1021/jp504496k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ground- and excited-state protonation of Coumarin 102 (C102), a fluorescent probe applied frequently in heterogeneous systems with an aqueous phase, has been studied in aqueous solutions by spectroscopic experiments and theoretical calculations. For the dissociation constant of the protonated form in the ground state, pKa = 1.61 was obtained from the absorption spectra; for the excited-state dissociation constant, pKa* = 2.19 was obtained from the fluorescence spectra. These values were closely reproduced by theoretical calculations via a thermodynamic cycle (the value of pKa* also by calculations via the Förster cycle) using an implicit–explicit solvation model (polarized continuum model + addition of a solvent molecule). The theoretical calculations indicated that (i) in the ground state, C102 occurs primarily as a hydrogen-bonded water complex, with the oxo group as the binding site, (ii) this hydrogen bond becomes stronger upon excitation, and (iii) in the ground state, the amino nitrogen atom is the protonation site, and in the excited state, the carboxy oxygen atom is the protonation site. A comprehensive analysis of fluorescence decay data yielded the values kpr = 3.27 × 10(10) M(–1) s(–1) for the rate constant of the excited-state protonation and kdpr = 2.78 × 10(8) s(–1) for the rate constant of the reverse process (kpr and kdpr were treated as independent parameters). This, considering the relatively long fluorescence lifetimes of neutral C102 (6.02 ns) and its protonated form (3.06 ns) in aqueous media, means that a quasi-equilibrium state of excited-state proton transfer is reached in strongly acidic solutions.
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Affiliation(s)
- Dóra Hessz
- Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences , P.O. Box 286, 1519 Budapest, Hungary
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Mohammed OF, Xiao D, Batista VS, Nibbering ETJ. Excited-state intramolecular hydrogen transfer (ESIHT) of 1,8-dihydroxy-9,10-anthraquinone (DHAQ) characterized by ultrafast electronic and vibrational spectroscopy and computational modeling. J Phys Chem A 2014; 118:3090-9. [PMID: 24684387 DOI: 10.1021/jp501612f] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S2) and 1,10-quinone (S1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S2 and S1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S2/S1 relaxation to either the ground or triplet state.
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Affiliation(s)
- Omar F Mohammed
- Solar and Photovoltaics Engineering Research Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
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Poorabdollah H, Omidyan R, Solimannejad M, Azimi G. Hydrogen bond strengthening of cis-trans glyoxal dimers in electronic excited states: a theoretical study. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2014; 122:337-342. [PMID: 24317260 DOI: 10.1016/j.saa.2013.11.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 10/02/2013] [Accepted: 11/02/2013] [Indexed: 06/02/2023]
Abstract
The second-order approximate coupled-cluster (CC2) method was performed to investigate the excited state hydrogen-bonding properties of Glyoxal (C2H2O2, Gl) dimers. Since the strengthening and weakening of hydrogen bonds can be investigated by monitoring the vibrational absorption spectra of some hydrogen-bonded groups in different electronic states, the infrared spectra of the hydrogen-bonded Gl-Gl complexes in both of the ground state and the S1 electronically excited state are calculated using the MP2/CC2 methods respectively. We demonstrated that the intermolecular hydrogen bond C=O⋯H-C between two glyoxal molecules is significantly strengthened in the electronically excited S1 state upon photoexcitation of the hydrogen-bonded Gl-Gl complexes.
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Affiliation(s)
| | - Reza Omidyan
- Department of Chemistry, University of Isfahan, 81746-7344 Isfahan, Iran.
| | - Mohammad Solimannejad
- Quantum Chemistry Group, Department of Chemistry, Faculty of Sciences, Arak University, Arak 38156-8-8349, Iran
| | - Gholamhasan Azimi
- Department of Chemistry, University of Isfahan, 81746-7344 Isfahan, Iran
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22
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Su J, Tian D. Strengthening of hydrogen bonded coumarin 102 in ethanol solvent upon photoexcitation. NEW J CHEM 2014. [DOI: 10.1039/c3nj00810j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Messina F, Prémont-Schwarz M, Braem O, Xiao D, Batista VS, Nibbering ETJ, Chergui M. Ultrafast Solvent-Assisted Electronic Level Crossing in 1-Naphthol. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201301931] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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24
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Messina F, Prémont-Schwarz M, Braem O, Xiao D, Batista VS, Nibbering ETJ, Chergui M. Ultrafast Solvent-Assisted Electronic Level Crossing in 1-Naphthol. Angew Chem Int Ed Engl 2013; 52:6871-5. [DOI: 10.1002/anie.201301931] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Indexed: 11/12/2022]
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Barman N, Singha D, Sahu K. Fluorescence Quenching of Hydrogen-Bonded Coumarin 102-Phenol Complex: Effect of Excited-State Hydrogen Bonding Strength. J Phys Chem A 2013; 117:3945-53. [DOI: 10.1021/jp4019298] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nabajeet Barman
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Debabrata Singha
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Kalyanasis Sahu
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
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26
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Jha SK, Ji M, Gaffney KJ, Boxer SG. Site-specific measurement of water dynamics in the substrate pocket of ketosteroid isomerase using time-resolved vibrational spectroscopy. J Phys Chem B 2012; 116:11414-21. [PMID: 22931297 DOI: 10.1021/jp305225r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Little is known about the reorganization capacity of water molecules at the active sites of enzymes and how this couples to the catalytic reaction. Here, we study the dynamics of water molecules at the active site of a highly proficient enzyme, Δ(5)-3-ketosteroid isomerase (KSI), during a light-activated mimic of its catalytic cycle. Photoexcitation of a nitrile-containing photoacid, coumarin183 (C183), mimics the change in charge density that occurs at the active site of KSI during the first step of the catalytic reaction. The nitrile of C183 is exposed to water when bound to the KSI active site, and we used time-resolved vibrational spectroscopy as a site-specific probe to study the solvation dynamics of water molecules in the vicinity of the nitrile. We observed that water molecules at the active site of KSI are highly rigid, during the light-activated catalytic cycle, compared to the solvation dynamics observed in bulk water. On the basis of this result, we hypothesize that rigid water dipoles at the active site might help in the maintenance of the preorganized electrostatic environment required for efficient catalysis. The results also demonstrate the utility of nitrile probes in measuring the dynamics of local (H-bonded) water molecules in contrast to the commonly used fluorescence methods which measure the average behavior of primary and subsequent spheres of solvation.
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Affiliation(s)
- Santosh Kumar Jha
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, USA
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27
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Messina F, El-Zohry AM, Mohammed OF, Chergui M. The Role of Site-Specific Hydrogen Bonding Interactions in the Solvation Dynamics of N-Acetyltryptophanamide. J Phys Chem B 2012; 116:10730-8. [DOI: 10.1021/jp305363y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Fabrizio Messina
- Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide
(LSU), ISIC, Faculté des Sciences de Base, station 6, CH-1015
Lausanne-Dorigny, Switzerland
| | - Ahmed M. El-Zohry
- Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide
(LSU), ISIC, Faculté des Sciences de Base, station 6, CH-1015
Lausanne-Dorigny, Switzerland
- Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt
| | - Omar F. Mohammed
- Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt
| | - Majed Chergui
- Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide
(LSU), ISIC, Faculté des Sciences de Base, station 6, CH-1015
Lausanne-Dorigny, Switzerland
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28
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Ghosh HN, Adamczyk K, Verma S, Dreyer J, Nibbering ETJ. On the role of hydrogen bonds in photoinduced electron-transfer dynamics between 9-fluorenone and amine solvents. Chemistry 2012; 18:4930-7. [PMID: 22389093 DOI: 10.1002/chem.201102994] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 12/23/2011] [Indexed: 11/09/2022]
Abstract
Using ultrafast fluorescence upconversion and mid-infrared spectroscopy, we explore the role of hydrogen bonds in the photoinduced electron transfer (ET) between 9-fluorenone (FLU) and the solvents trimethylamine (TEA) and dimethylamine (DEA). FLU shows hydrogen-bond dynamics in the methanol solvent upon photoexcitation, and similar effects may be anticipated when using DEA, whereas no hydrogen bonds can occur in TEA. Photoexcitation of the electron-acceptor dye molecule FLU with a 400 nm pump pulse induces ultrafast ET from the amine solvents, which is followed by 100 fs IR probe pulses as well as fluorescence upconversion, monitoring the time evolution of marker bands of the FLU S(1) state and the FLU radical anion, and an overtone band of the amine solvent, marking the transient generation of the amine radical cation. A comparison of the experimentally determined forward charge-separation and backward charge-recombination rates for the FLU-TEA and FLU-DEA reaction systems with the driving-force dependencies calculated for the forward and backward ET rates reveals that additional degrees of freedom determine the ET reaction dynamics for the FLU-DEA system. We suggest that hydrogen bonding between the DEA molecules plays a key role in this behaviour.
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Affiliation(s)
- Hirendra N Ghosh
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
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29
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Theoretical study on the excited-state photoinduced electron transfer facilitated by hydrogen bonding strengthening in the C337–AN/MAN complexes. COMPUT THEOR CHEM 2012. [DOI: 10.1016/j.comptc.2012.01.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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30
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Ghosh HN, Verma S, Nibbering ETJ. Ultrafast Forward and Backward Electron Transfer Dynamics of Coumarin 337 in Hydrogen-Bonded Anilines As Studied with Femtosecond UV-Pump/IR-Probe Spectroscopy. J Phys Chem A 2010; 115:664-70. [DOI: 10.1021/jp108090b] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Hirendra N. Ghosh
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai −400085, India
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max Born Strasse 2A, D-12489, Berlin, Germany
| | - Sandeep Verma
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai −400085, India
| | - Erik T. J. Nibbering
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max Born Strasse 2A, D-12489, Berlin, Germany
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31
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Wang R, Hao C, Li P, Wei NN, Chen J, Qiu J. Time-dependent density functional theory study on the electronic excited-state hydrogen-bonding dynamics of 4-aminophthalimide (4AP) in aqueous solution: 4AP and 4AP-(H2O)1,2 clusters. J Comput Chem 2010; 31:2157-63. [DOI: 10.1002/jcc.21504] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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32
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Mondal JA, Samant V, Varne M, Singh AK, Ghanty TK, Ghosh HN, Palit DK. The Role of Hydrogen-Bonding Interactions in the Ultrafast Relaxation Dynamics of the Excited States of 3- and 4-Aminofluoren-9-ones. Chemphyschem 2009; 10:2995-3012. [DOI: 10.1002/cphc.200900325] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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33
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Mohammed O, Kwon OH, Othon C, Zewail A. Charge Transfer Assisted by Collective Hydrogen-Bonding Dynamics. Angew Chem Int Ed Engl 2009; 48:6251-6. [DOI: 10.1002/anie.200902340] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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34
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Mohammed O, Kwon OH, Othon C, Zewail A. Charge Transfer Assisted by Collective Hydrogen-Bonding Dynamics. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200902340] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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35
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Zhou P, Song P, Liu J, Han K, He G. Experimental and theoretical study of the rotational reorientation dynamics of 7-animocoumarin derivatives in polar solvents: hydrogen-bonding effects. Phys Chem Chem Phys 2009; 11:9440-9. [DOI: 10.1039/b910043a] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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36
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Zhao GJ, Han KL. Time-dependent density functional theory study on hydrogen-bonded intramolecular charge-transfer excited state of 4-dimethylamino-benzonitrile in methanol. J Comput Chem 2008; 29:2010-7. [PMID: 18351604 DOI: 10.1002/jcc.20957] [Citation(s) in RCA: 253] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The time-dependent density functional theory (TDDFT) method was carried out to investigate the hydrogen-bonded intramolecular charge-transfer (ICT) excited state of 4-dimethylaminobenzonitrile (DMABN) in methanol (MeOH) solvent. We demonstrated that the intermolecular hydrogen bond C[triple bond]N...H-O formed between DMABN and MeOH can induce the C[triple bond]N stretching mode shift to the blue in both the ground state and the twisted intramolecular charge-transfer (TICT) state of DMABN. Therefore, the two components at 2091 and 2109 cm(-1) observed in the time-resolved infrared (TRIR) absorption spectra of DMABN in MeOH solvent were reassigned in this work. The hydrogen-bonded TICT state should correspond to the blue-side component at 2109 cm(-1), whereas not the red-side component at 2091 cm(-1) designated in the previous study. It was also demonstrated that the intermolecular hydrogen bond C[triple bond]N...H-O is significantly strengthened in the TICT state. The intermolecular hydrogen bond strengthening in the TICT state can facilitate the deactivation of the excited state via internal conversion (IC), and thus account for the fluorescence quenching of DMABN in protic solvents. Furthermore, the dynamic equilibrium of these electronically excited states is explained by the hydrogen bond strengthening in the TICT state.
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Affiliation(s)
- Guang-Jiu Zhao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
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37
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Wells NP, McGrath MJ, Siepmann JI, Underwood DF, Blank DA. Excited State Hydrogen Bond Dynamics: Coumarin 102 in Acetonitrile−Water Binary Mixtures. J Phys Chem A 2008; 112:2511-4. [DOI: 10.1021/jp710889t] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Nathan P. Wells
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Matthew J. McGrath
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - J. Ilja Siepmann
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - David F. Underwood
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - David A. Blank
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
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38
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39
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Petkova I, Mudadu MS, Singh A, Thummel RP, van Stokkum IHM, Buma WJ, Waluk J. Structure and Photophysics of 2-(2‘-Pyridyl)benzindoles: The Role of Intermolecular Hydrogen Bonds. J Phys Chem A 2007; 111:11400-9. [DOI: 10.1021/jp0735841] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Irina Petkova
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
| | - Maria S. Mudadu
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
| | - Ajay Singh
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
| | - Randolph P. Thummel
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
| | - Ivo H. M. van Stokkum
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
| | - Wybren Jan Buma
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
| | - Jacek Waluk
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland, Institute of Organic Chemistry, Bulgarian Academy of Sciences, Akad. G. Bontchev bl. IX, Sofia 1113, Bulgaria, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Chemistry, University of Houston, Houston, Texas, 77204-5003, and Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The
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40
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Zhao GJ, Liu JY, Zhou LC, Han KL. Site-selective photoinduced electron transfer from alcoholic solvents to the chromophore facilitated by hydrogen bonding: a new fluorescence quenching mechanism. J Phys Chem B 2007; 111:8940-5. [PMID: 17616225 DOI: 10.1021/jp0734530] [Citation(s) in RCA: 573] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Solute-solvent intermolecular photoinduced electron transfer (ET) reaction was proposed to account for the drastic fluorescence quenching behaviors of oxazine 750 (OX750) chromophore in protic alcoholic solvents. According to our theoretical calculations for the hydrogen-bonded OX750-(alcohol)(n) complexes using the time-dependent density functional theory (TDDFT) method, we demonstrated that the ET reaction takes place from the alcoholic solvents to the chromophore and the intermolecular ET passing through the site-specific intermolecular hydrogen bonds exhibits an unambiguous site selectivity. In our motivated experiments of femtosecond time-resolved stimulated emission pumping fluorescence depletion spectroscopy (FS TR SEP FD), it could be noted that the ultrafast ET reaction takes place as fast as 200 fs. This ultrafast intermolecular photoinduced ET is much faster than the diffusive solvation process, and even significantly faster than the intramolecular vibrational redistribution (IVR) process of the OX750 chromophore. Therefore, the ultrafast intermolecular ET should be coupled with the hydrogen-bonding dynamics occurring in the sub-picosecond time domain. We theoretically demonstrated for the first time that the selected hydrogen bonds are transiently strengthened in the excited states for facilitating the ultrafast solute-solvent intermolecular ET reaction.
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Affiliation(s)
- Guang-Jiu Zhao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
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41
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Zhao GJ, Han KL. Ultrafast Hydrogen Bond Strengthening of the Photoexcited Fluorenone in Alcohols for Facilitating the Fluorescence Quenching. J Phys Chem A 2007; 111:9218-23. [PMID: 17608458 DOI: 10.1021/jp0719659] [Citation(s) in RCA: 332] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The time-dependent density functional theory (TDDFT) method was performed to investigate the excited-state hydrogen-bonding dynamics of fluorenone (FN) in hydrogen donating methanol (MeOH) solvent. The infrared spectra of the hydrogen-bonded FN-MeOH complex in both the ground state and the electronically excited states are calculated using the TDDFT method, since the ultrafast hydrogen-bonding dynamics can be investigated by monitoring the vibrational absorption spectra of some hydrogen-bonded groups in different electronic states. We demonstrated that the intermolecular hydrogen bond C=O...H-O between fluorenone and methanol molecules is significantly strengthened in the electronically excited-state upon photoexcitation of the hydrogen-bonded FM-MeOH complex. The hydrogen bond strengthening in electronically excited states can be used to explain well all the spectral features of fluorenone chromophore in alcoholic solvents. Furthermore, the radiationless deactivation via internal conversion (IC) can be facilitated by the hydrogen bond strengthening in the excited state. At the same time, quantum yields of the excited-state deactivation via fluorescence are correspondingly decreased. Therefore, the total fluorescence of fluorenone in polar protic solvents can be drastically quenched by hydrogen bonding.
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Affiliation(s)
- Guang-Jiu Zhao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
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42
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Zhao GJ, Han KL. Early Time Hydrogen-Bonding Dynamics of Photoexcited Coumarin 102 in Hydrogen-Donating Solvents: Theoretical Study. J Phys Chem A 2007; 111:2469-74. [PMID: 17388339 DOI: 10.1021/jp068420j] [Citation(s) in RCA: 523] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To study the early time hydrogen-bonding dynamics of chromophore in hydrogen-donating solvents upon photoexcitation, the infrared spectra of the hydrogen-bonded solute-solvent complexes in electronically excited states have been calculated using the time-dependent density functional theory (TDDFT) method. The hydrogen-bonding dynamics in electronically excited states can be widely monitored by the spectral shifts of some characteristic vibrational modes involved in the formation of hydrogen bonds. In this study, we have demonstrated that the intermolecular hydrogen bonds between coumarin 102 (C102) and hydrogen-donating solvents are strengthened in the early time of photoexcitation to the electronically excited state by theoretically monitoring the stretching modes of C=O and H-O groups. This is significantly contrasted with the ultrafast hydrogen bond cleavage taking place within a 200-fs time scale upon electronic excitation, proposed in many femtosecond time-resolved vibrational spectroscopy experiments. The transient hydrogen bond strengthening behaviors in excited states of chromophores in hydrogen-donating solvents, which we have demonstrated here for the first time, may take place widely in many other systems in solution and are very important to explain the fluorescence-quenching phenomena associated with some radiationless deactivation processes, for example, the ultrafast solute-solvent intermolecular electron transfer and the internal conversion process from the fluorescent state to the ground state.
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Affiliation(s)
- Guang-Jiu Zhao
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
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43
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Ma C, Du Y, Kwok WM, Phillips DL. Femtosecond Transient Absorption and Nanosecond Time-Resolved Resonance Raman Study of the Solvent-Dependent Photo-Deprotection Reaction of Benzoin Diethyl Phosphate. Chemistry 2007; 13:2290-305. [PMID: 17154320 DOI: 10.1002/chem.200600893] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A combined femtosecond transient absorption (fs-TA) and nanosecond time-resolved resonance Raman (ns-TR3) study was performed to directly detect the dynamics and elucidate the mechanism of the excited state deactivation and solvent-dependent photo-deprotection pathways for benzoin diethyl phosphate (BDP) in neat acetonitrile (MeCN) and 75 % H2O/25 % MeCN. Comparison of the TA spectral evolution observed in the two solvents provides explicit evidence that the photophysical deactivation of the BDP singlet excited state has little solvent dependence. The TA spectra also indicate the related internal conversion (IC) and intersystem crossing (ISC) processes occur rapidly on hundreds of femtoseconds and approximately 2-3 ps time scales, respectively. From this and in conjunction with a photochemistry study and ground state resonance Raman (RR) measurements, the TA results reveal that the phenacyl localized BDP triplet state (that is mainly npi* nature) is the common and immediate precursor to the photo-deprotection reaction in both solvents. However, the triplet deprotection follows different pathways in neat MeCN versus the largely water containing solvent. The deprotection reaction in MeCN was determined to occur with a approximately 11 ns time constant and the reaction was found to be an unimolecular process leading to elimination of the diethyl phosphoric acid apparently concurrent with cyclization to yield the benzofuran product. In the water mixed solvent, the triplet reaction was observed to proceed with a approximately 15 ns time constant and the reaction leads to not only the deprotection-cyclization but also a heterolytic dissociation to release the diethyl phosphate anion through a branching and competing mechanism. The ns-TR3 spectra combined with relevant DFT calculations have been used to characterize the dynamics, structure and vibrational frequencies to help identify the important intermediates as well as to explore the reaction pathway leading to formation of the solvolysis product in the largely water solvent. A consecutive mechanism has been revealed for the heterolysis-solvolysis reaction in the water mixed solvent. The present work provides direct and irrevocable evidence for the dynamics and mechanistic description of the overall photophysics and deprotection related photochemistry for BDP.
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Affiliation(s)
- Chensheng Ma
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., PR China
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Kumbhakar M, Goel T, Nath S, Mukherjee T, Pal H. Microenvironment in the corona region of triblock copolymer micelles: temperature dependent solvation and rotational relaxation dynamics of coumarin dyes. J Phys Chem B 2007; 110:25646-55. [PMID: 17181202 DOI: 10.1021/jp063839v] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dynamic Stokes' shift and fluorescence anisotropy measurements using coumarin-153 (C153) and coumarin-151 (C151) as the fluorescence probes have been carried out in aqueous poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20 (P123) and poly(ethylene oxide)100-poly(propylene oxide)70-poly(ethylene oxide)100 (F127) block copolymer micelles with an aim to understand the water structures and dynamics in the micellar corona region. It has been established that the probes reside in the micellar corona region. It is indicated that the corona regions of P123 and F127 micelles are relatively less hydrated than the Palisade layers of neutral micelles like Triton-X-100 and Brij-35. From the appraisal of total Stokes' shift values for the probes in the two block copolymer micelles, it is inferred that the F127 micelle is more hydrated than the P123 micelle. It is observed that the dynamic Stokes' shift values for both of the probes remain more or less similar at all the temperatures studied in the P123 micelle. For C153 in F127, however, the observed Stokes' shift is seen to decrease quite sharply with temperature, though it remains quite similar for C151. Moreover, the fraction of the unobserved initial dynamic Stokes' shift is appreciably higher for both the probes in the F127 micelle compared to that in P123. Over the studied temperature range of 293-313 K, the spectral shift correlation function is described adequately by a bi-exponential function. Rotational relaxation times for C153 in both the micelles show a kind of transition at around 303 K. These results have been rationalized assuming collapse of the poly(ethylene oxide) (PEO) blocks and formation of water clusters in the corona region due to dehydration of poly(ethylene oxide) blocks with an increase in temperature. A dissimilar probe location has been inferred for the differences in the results with C153 and C151 probes in F127. Comparison of the microviscosity and the hydration of the block copolymer micelles has also been made with those of the other commonly used neutral micelles, for a better understanding of the results in the block copolymer micelles.
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Affiliation(s)
- Manoj Kumbhakar
- Radiation & Photochemistry Division, Bhabha Atomic Research Center, Mumbai 400 085, India.
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Structure and Reactivity of Organic Intermediates as Revealed by Time-Resolved Infrared Spectroscopy. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/9780470133576.ch2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
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Espagne A, Paik DH, Changenet-Barret P, Martin MM, Zewail AH. Ultrafast Photoisomerization of Photoactive Yellow Protein Chromophore Analogues in Solution: Influence of the Protonation State. Chemphyschem 2006; 7:1717-26. [PMID: 16847839 DOI: 10.1002/cphc.200600137] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We investigate solvent viscosity and polarity effects on the photoisomerization of the protonated and deprotonated forms of two analogues of the photoactive yellow protein (PYP) chromophore. These are trans-p-hydroxybenzylidene acetone and trans-p-hydroxyphenyl cinnamate, studied in solutions of different polarity and viscosity at room temperature, by means of femtosecond fluorescence up-conversion. The fluorescence lifetimes of the protonated forms are found to be barely sensitive to solvent viscosity, and to increase with increasing solvent polarity. In contrast, the fluorescence decays of the deprotonated forms are significantly slowed down in viscous media and accelerated in polar solvents. These results elucidate the dramatic influence of the protonation state of the PYP chromophore analogues on their photoinduced dynamics. The viscosity and polarity effects are, respectively, interpreted in terms of different isomerization coordinates and charge redistribution in S(1). A trans-to-cis isomerization mechanism involving mainly the ethylenic double-bond torsion and/or solvation is proposed for the anionic forms, whereas "concerted" intramolecular motions are proposed for the neutral forms.
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Affiliation(s)
- Agathe Espagne
- UMR CNRS-ENS 8640 Pasteur, Département de Chimie, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
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Espagne A, Changenet-Barret P, Plaza P, Martin MM. Solvent Effect on the Excited-State Dynamics of Analogues of the Photoactive Yellow Protein Chromophore. J Phys Chem A 2006; 110:3393-404. [PMID: 16526618 DOI: 10.1021/jp0563843] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We previously reported that two analogues of the Photoactive Yellow Protein chromophore, trans-p-hydroxycinnamic acid (pCA(2-)) and its amide derivative (pCM-) in their deprotonated forms, undergo a trans-cis photoisomerization whereas the thioester derivative, trans-p-hydroxythiophenyl cinnamate (pCT-), does not. pCT- is also the only one to exhibit a short-lived intermediate on its excited-state deactivation pathway. We here further stress the existence of two different relaxation mechanisms for these molecules and examine the reaction coordinates involved. We looked at the effect of the solvent properties (viscosity, polarity, solvation dynamics) on their excited-state relaxation dynamics, probed by ultrafast transient absorption spectroscopy. Sensitivity to the solvent properties is found to be larger for pCT- than for pCA(2-) and pCM-. This difference is considered to reveal that either the relaxation pathway or the reaction coordinate is different for these two classes of analogues. It is also found to be correlated to the electron donor-acceptor character of the molecule. We attribute the excited-state deactivation of analogues bearing a weaker acceptor group, pCA(2-) and pCM-, to a stilbene-like photoisomerization mechanism with the concerted rotation of the ethylenic bond and one adjacent single bond. For pCT-, which contains a stronger acceptor group, we consider a photoisomerization mechanism mainly involving the single torsion of the ethylenic bond. The excited-state deactivation of pCT- would lead to the formation of a ground-state intermediate at the "perp" geometry, which would return to the initial trans conformation without net isomerization.
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Affiliation(s)
- Agathe Espagne
- Département de Chimie, Ecole Normale Supérieure (UMR CNRS 8640 PASTEUR), 24 rue Lhomond, 75231 Paris Cedex 05, France
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Ma C, Kwok WM, Chan WS, Du Y, Kan JTW, Toy PH, Phillips DL. Ultrafast Time-Resolved Transient Absorption and Resonance Raman Spectroscopy Study of the Photodeprotection and Rearrangement Reactions of p-Hydroxyphenacyl Caged Phosphates. J Am Chem Soc 2006; 128:2558-70. [PMID: 16492039 DOI: 10.1021/ja0532032] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The kinetics and mechanism of the photodeprotection and rearrangement reactions for the pHP phototrigger compounds p-hydroxyphenacyl diethyl phosphate (HPDP) and diphenyl phosphate (HPPP) were studied using transient absorption (TA) and picosecond time-resolved resonance Raman (ps-TR(3)) spectroscopy. TA spectroscopy was employed to detect the dynamics of the triplet precursor decay as well as to investigate the influence of the solvent and leaving group on the triplet quenching process. Ps-TR(3) spectroscopy was used to directly monitor the formation dynamics for the photosolvolytic rearrangement product and its solvent and leaving group dependence. The TA and TR(3) spectroscopy experiments were also used to characterize the structural and electronic properties of the triplet precursor to the HPDP and HPPP deprotection reactions. The solvent effect observed in conjunction with the leaving group dependence of the triplet decay dynamics are consistent with a concerted solvent assisted triplet cleavage through a heterolytic mechanism for the HPDP and HPPP photodeprotection process. Correlation of the dynamics between the deprotection and rearrangement processes reveals there is a consecutive mechanism and the involvement of an intermediate between the two reaction steps. The reaction rate of the deprotection and rearrangement steps and the influence of the solvent and leaving group were determined and evaluated based on kinetic modeling of the dynamical data obtained experimentally for HPDP and HPPP in H(2)O/MeCN mixed solvents with varying water concentration in the solvent system. A solvation complex with a contact ion pair character was proposed to be the intermediate involved in the deprotection and rearrangement pathway. The results here combined with our previous study on the photophysical events occurring on the early picosecond time scale (Ma; et al. J. Am. Chem. Soc. 2005, 127, 1463-1472) provide a real time overall mechanistic description for the photodeprotection and rearrangement reactions of pHP caged phosphate phototrigger compounds.
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Affiliation(s)
- Chensheng Ma
- Contribution from the Department of Chemistry, The University of Hong Kong, SAR, P R China
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Samant V, Singh AK, Ramakrishna G, Ghosh HN, Ghanty TK, Palit DK. Ultrafast Intermolecular Hydrogen Bond Dynamics in the Excited State of Fluorenone. J Phys Chem A 2005; 109:8693-704. [PMID: 16834271 DOI: 10.1021/jp050848f] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Steady-state fluorescence and time-resolved absorption measurements in pico- and femtosecond time domain have been used to investigate the dynamics of hydrogen bond in the excited singlet (S(1)) state of fluorenone in alcoholic solvents. A comparison of the features of the steady-state fluorescence spectra of fluorenone in various kinds of media demonstrates that two spectroscopically distinct forms of fluorenone in the S(1) state, namely the non-hydrogen-bonded (or free) molecule as well as the hydrogen-bonded complex, are responsible for the dual-fluorescence behavior of fluorenone in solutions of normal alcoholic solvents at room temperature (298 K). However, in 2,2,2-trifluoroethanol (TFE), a strong hydrogen bond donating solvent, emission from only the hydrogen-bonded complex is observed. Significant differences have also been observed in the temporal evolution of the absorption spectroscopic properties of the S(1) state of fluorenone in protic and aprotic solvents following photoexcitation using 400 nm laser pulses. An ultrafast component representing the solvent-induced vibrational energy relaxation (VER) process has been associated with the dynamics of the S(1) state of fluorenone in all kinds of solvents. However, in protic solvents, in addition to the VER process, further evolution of the spectroscopic and dynamical properties of the S(1) state have been observed because of repositioning of the hydrogen bonds around the carbonyl group. In normal alcohols, two different kinds of hydrogen-bonded complex of the fluorenone-alcohol system with different orientations of the hydrogen bond with respect to the carbonyl group and the molecular plane of fluorenone have been predicted. On the other hand, in TFE, formation of only one kind of hydrogen-bonded complex has been observed. These observations have been supported by theoretical calculations of the geometries of the hydrogen-bonded complexes in the ground and the excited states of fluorenone. Linear correlation between the lifetimes of the equilibration process occurring because of repositioning of the hydrogen bonds and Debye or longitudinal relaxation times of the normal alcoholic solvents establish the fact that, in weakly hydrogen bond donating solvents, the hydrogen bond dynamics can be described as merely a solvation process. Whereas, in TFE, hydrogen bond dynamics is better described by a process of conversion between two distinct excited states, namely, the non-hydrogen-bonded form and the hydrogen-bonded complex.
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Affiliation(s)
- Vaishali Samant
- Radiation Chemistry & Chemical Dynamics Division, Bhabha Atomic Research Center, Mumbai 400089, India
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Mondal JA, Ghosh HN, Mukherjee T, Palit DK. S2 Fluorescence and Ultrafast Relaxation Dynamics of the S2 and S1 States of a Ketocyanine Dye. J Phys Chem A 2005; 109:6836-46. [PMID: 16834039 DOI: 10.1021/jp0508498] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamics of the excited singlet (both the S2 and S1) states of a ketocyanine dye, namely, 2,5-bis[(2,3-dihydroindolyl)-propylene]-cyclopentanone (KCD), have been investigated in different kinds of media using steady-state absorption and emission as well as femtosecond transient absorption spectroscopic techniques. Steady-state fluorescence measurements, following photoexcitation of KCD to its second excited singlet state, reveal dual fluorescence (emission from both the S2 and S1 states) behavior. Although the intensity of the S2 --> S0 fluorescence is weaker than that of the S1 --> S0 fluorescence in solutions at room temperature (298 K), the former becomes as much as or more intense than the latter in rigid matrixes at 77 K. The lifetime of the S2 state is short and varies between 0.2 and 0.6 ps in different solvents. After its creation, the S2 state undergoes two simultaneous processes, namely, S2 --> S0 fluorescence and S2 --> S1 internal conversion. Time-resolved measurements reveal the presence of an ultrafast component in the decay dynamics of the S1 state. A good correlation between the lifetime of this component and the longitudinal relaxation times (tauL) of the solvents suggests that this component arises due to solvation in polar solvents. More significant evolution of the spectroscopic properties of the S1 state in alcoholic solvents in the ultrafast time domain has been explained by the occurrence of the repositioning of the hydrogen bonds around the carbonyl group in the excited state of KCD. In 2,2,2-trifluoroethanol, a strongly hydrogen bond donating solvent, it has even been possible to establish the existence of two distinct forms of the S1 state, namely, the non-hydrogen-bonded (or free) molecule and the hydrogen-bonded complex.
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Affiliation(s)
- Jahur A Mondal
- Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
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