1
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Imamura K, Yamazaki T, Yokogawa D, Higashi M, Sato H. Nuclear magnetic shielding of molecule in solution based on reference interaction site model self-consistent field with spatial electron density distribution. J Chem Phys 2020; 152:194102. [DOI: 10.1063/5.0008903] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Kosuke Imamura
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Takeshi Yamazaki
- 1QB Information Technologies (1QBit), 200-1285 West Pender Street, Vancouver, British Columbia V6E 4B1, Canada
| | - Daisuke Yokogawa
- Graduate School of Arts and Science, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Masahiro Higashi
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8520, Japan
| | - Hirofumi Sato
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
- Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8520, Japan
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
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2
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Maschietto F, Sanz García J, Campetella M, Ciofini I. Using density based indexes to characterize excited states evolution. J Comput Chem 2019; 40:650-656. [PMID: 30549077 DOI: 10.1002/jcc.25750] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 09/10/2018] [Accepted: 09/13/2018] [Indexed: 12/24/2022]
Abstract
With the aim of offering new computational tools helping in the description of photochemical reactions and phenomena occurring at the excited state, we present in this work the capability of a density based index (Π) in locating decay channels from higher to lower excited states. The Π index, previously applied to disclose non-radiative decay channels from the first excited state to the ground state, is very simple in its formulation and can be evaluated, practically with no extra computational cost, and coupled to any quantum method able to provide excited states densities. Indeed, this index relies only on the knowledge of energetics and electron densities of the different electronic states involved in the decay. In the present work, we show the proficiency of the Π index in the general case of decay between excited states by applying it to two model systems well characterized both theoretically and experimentally. In both cases, this descriptor was successful in spotting the regions where excited states are more likely to decay, thus suggesting its potential interest for further application in the design of new compounds. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Federica Maschietto
- Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris, F-75005, Paris, France
| | - Juan Sanz García
- Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris, F-75005, Paris, France
| | - Marco Campetella
- Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris, F-75005, Paris, France
| | - Ilaria Ciofini
- Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris, F-75005, Paris, France
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3
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Georgieva I, Aquino AJA, Plasser F, Trendafilova N, Köhn A, Lischka H. Intramolecular Charge-Transfer Excited-State Processes in 4-(N,N-Dimethylamino)benzonitrile: The Role of Twisting and the πσ* State. J Phys Chem A 2015; 119:6232-43. [PMID: 25989536 PMCID: PMC4476306 DOI: 10.1021/acs.jpca.5b03282] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
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The
structural processes leading to dual fluorescence of 4-(dimethylamino)benzonitrile
in the gas phase and in acetonitrile solvent were investigated using
a combination of multireference configuration interaction (MRCI) and
the second-order algebraic diagrammatic construction (ADC(2)) methods.
Solvent effects were included on the basis of the conductor-like screening
model. The MRCI method was used for computing the nonadiabatic interaction
between the two lowest excited ππ* states (S2(La, CT) and S1(Lb, LE)) and the
corresponding minimum on the crossing seam (MXS) whereas the ADC(2)
calculations were dedicated to assessing the role of the πσ*
state. The MXS structure was found to have a twisting angle of ∼50°.
The branching space does not contain the twisting motion of the dimethylamino
group and thus is not directly involved in the deactivation process
from S2 to S1. Polar solvent effects are not
found to have a significant influence on this situation. Applying Cs symmetry restrictions, the ADC(2) calculations
show that CCN bending leads to a strong stabilization and to significant
charge transfer (CT). Nevertheless, this structure is not a minimum
but converts to the local excitation (LE) structure on releasing the
symmetry constraint. These findings suggest that the main role in
the dynamics is played by the nonadiabatic interaction of the LE and
CT states and that the main source for the dual fluorescence is the
twisted internal charge-transfer state in addition to the LE state.
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Affiliation(s)
- Ivelina Georgieva
- †Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Adélia J A Aquino
- ‡Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States.,§Institute for Theoretical Chemistry, University of Vienna, A-1090 Vienna, Austria
| | - Felix Plasser
- §Institute for Theoretical Chemistry, University of Vienna, A-1090 Vienna, Austria
| | - Natasha Trendafilova
- †Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Andreas Köhn
- ∥Institute for Theoretical Chemistry, University of Stuttgart, 70569 Stuttgart, Germany
| | - Hans Lischka
- ‡Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States.,§Institute for Theoretical Chemistry, University of Vienna, A-1090 Vienna, Austria
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4
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Theoretical Study of the Electronic Excited States and Fluorescence Spectra of Squaraine in Solution. J SOLUTION CHEM 2014. [DOI: 10.1007/s10953-014-0224-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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5
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Sato H. A modern solvation theory: quantum chemistry and statistical chemistry. Phys Chem Chem Phys 2013; 15:7450-65. [DOI: 10.1039/c3cp50247c] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Mao M, Ren MG, Song QH. Thermodynamics and Conformations in the Formation of Excited States and Their Interconversions for Twisted Donor-Substituted Tridurylboranes. Chemistry 2012; 18:15512-22. [DOI: 10.1002/chem.201201719] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Indexed: 11/10/2022]
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7
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LI JUANQIN, LI XIANGYUAN, WANG FENG. A THEORETICAL STUDY ON DUAL FLUORESCENCE OF 4-DIMETHYLAMINOPYRIDINE BY POLARIZABLE CONTINUUM MODEL. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633608004143] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Dual fluorescence spectra of 4-dimethylaminopyridine (DMAP) is investigated using time-dependent density functional theory and complete active space self-consistent field methods. Electronic absorption and emission spectra of DMAP have been investigated in three solvents, that is, cyclohexane, chloroform, and acetonitrile. The present study reveals that the dual fluorescence phenomena of DMAP appear in the cases of acetonitrile and chloroform, but not in cyclohexane. The electronic structures of the ground state and the intramolecular charge transfer states are, therefore, studied in order to reveal the insight of dual fluorescence. Our theoretical results suggest that the twisting of dimethylamino moiety in DMAP is necessary for the intramolecular charge transfer. The mechanism of the dual fluorescence of DMAP is discussed based on the twisted intramolecular charge transfer model and the dual fluorescence phenomenon is explained theoretically.
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Affiliation(s)
- JUAN-QIN LI
- College of Chemical Engineering and State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610065, P. R. China
| | - XIANG-YUAN LI
- College of Chemical Engineering and State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610065, P. R. China
| | - FENG WANG
- Center for Molecular Simulation, Swinburne University of Technology, Hawthorn, Melbourne, Vic. 3122, Australia
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8
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Fdez Galván I, Martín ME, Muñoz-Losa A, Aguilar MA. Dual Fluorescence of Fluorazene in Solution: A Computational Study. J Chem Theory Comput 2011; 7:3694-701. [PMID: 26598264 DOI: 10.1021/ct2005227] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fluorazene molecule presents dual fluorescence in polar solvents. Its absorption and emission properties in gas phase and in acetonitrile solution have been studied theoretically using the complete active space second-order perturbation//complete active space self-consistent field quantum methodology and average solvent electrostatic potential from molecular dynamics for the solvent effects. In gas phase, two optimized excited-state geometries were obtained, one of them corresponds to a local excitation (LE), and the other is an intramolecular charge transfer (ICT) and lies higher in energy. In acetonitrile solution, a second ICT structure where the molecule remains planar is found, and the energy differences are reduced. Fluorescence energies from LE and the planar ICT have a good agreement with the experimental bands, but emission from the bent ICT has too low an energy.
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Affiliation(s)
- Ignacio Fdez Galván
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura , Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - M Elena Martín
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura , Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - Aurora Muñoz-Losa
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura , Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - Manuel A Aguilar
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura , Avda. de Elvas s/n, 06071 Badajoz, Spain
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9
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Fdez. Galván I, Martín ME, Muñoz-Losa A, Sánchez ML, Aguilar MA. Solvent Effects on the Structure and Spectroscopy of the Emitting States of 1-Phenylpyrrole. J Chem Theory Comput 2011; 7:1850-7. [DOI: 10.1021/ct2001182] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Ignacio Fdez. Galván
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - M. Elena Martín
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - Aurora Muñoz-Losa
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - M. Luz Sánchez
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - Manuel A. Aguilar
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
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10
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Chan CTL, Cheng CCW, Ho KYF, Kwok WM. Femtosecond broadband time-resolved fluorescence and transient absorption study of the intramolecular charge transfer state of methyl 4-dimethylaminobenzoate. Phys Chem Chem Phys 2011; 13:16306-13. [DOI: 10.1039/c1cp21627a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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11
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12
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Galván IF, Martín ME, Aguilar MA. Theoretical Study of the Dual Fluorescence of 4-(N,N-Dimethylamino)benzonitrile in Solution. J Chem Theory Comput 2010; 6:2445-54. [DOI: 10.1021/ct9006713] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ignacio Fdez. Galván
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - M. Elena Martín
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
| | - Manuel A. Aguilar
- Química Física, Edif. José María Viguera Lobo, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain
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13
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Rhinehart JM, Mehlenbacher RD, McCamant D. Probing the Charge Transfer Reaction Coordinate of 4-(Dimethylamino)benzonitrile with Femtosecond Stimulated Raman Spectroscopy. J Phys Chem B 2010; 114:14646-56. [DOI: 10.1021/jp1023982] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Justin M. Rhinehart
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| | | | - David McCamant
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
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14
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Santhosh K, Banerjee S, Rangaraj N, Samanta A. Fluorescence Response of 4-(N,N′-Dimethylamino)benzonitrile in Room Temperature Ionic Liquids: Observation of Photobleaching under Mild Excitation Condition and Multiphoton Confocal Microscopic Study of the Fluorescence Recovery Dynamics. J Phys Chem B 2010; 114:1967-74. [DOI: 10.1021/jp910704y] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Kotni Santhosh
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India, and Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Sanghamitra Banerjee
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India, and Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Nandini Rangaraj
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India, and Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Anunay Samanta
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India, and Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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15
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Hayaki S, Kido K, Sato H, Sakaki S. Ab initio study on SN2 reaction of methyl p-nitrobenzenesulfonate and chloride anion in [mmim][PF6]. Phys Chem Chem Phys 2010; 12:1822-6. [DOI: 10.1039/b920190b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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16
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Yang JS, Lin CK, Lahoti AM, Tseng CK, Liu YH, Lee GH, Peng SM. Effect of Ground-State Twisting on the trans → cis Photoisomerization and TICT State Formation of Aminostilbenes. J Phys Chem A 2009; 113:4868-77. [DOI: 10.1021/jp807748t] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jye-Shane Yang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
| | - Cheng-Kai Lin
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
| | - Anand M. Lahoti
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
| | - Chung-Kai Tseng
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
| | - Yi-Hung Liu
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
| | - Gene-Hsiang Lee
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
| | - Shie-Ming Peng
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617, and Department of Chemistry, National Central University, Chungli, Taiwan 32001
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17
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Iida K, Yokogawa D, Ikeda A, Sato H, Sakaki S. Carbon dioxide capture at the molecular level. Phys Chem Chem Phys 2009; 11:8556-9. [DOI: 10.1039/b906912g] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Yang JS, Liau KL, Li CY, Chen MY. Meta conjugation effect on the torsional motion of aminostilbenes in the photoinduced intramolecular charge-transfer state. J Am Chem Soc 2007; 129:13183-92. [PMID: 17918840 DOI: 10.1021/ja0741022] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The photochemical behavior of a series of trans-3-(N-arylamino)stilbenes (m1, aryl = 4-substituted phenyl with a substituent of cyano (CN), hydrogen (H), methyl (Me), or methoxy (OM)) in both nonpolar and polar solvents is reported and compared to that of the corresponding para isomers (p1CN, p1H, p1Me, and p1OM). The distinct propensity of torsional motion toward a low-lying twisted intramolecular charge-transfer (TICT) state from the planar ICT (PICT) precursor between the meta and para isomers of 1CN and 1Me reveals the intriguing meta conjugation effect and the importance of the reaction kinetics. Whereas the poor charge-redistribution (delocalization) ability through the meta-phenylene bridge accounts for the unfavorable TICT-forming process for m1CN, it is such a property that slows down the decay processes of fluorescence and photoisomerization for m1Me, facilitating the competition of the single-bond torsional reaction. In contrast, the quinoidal character for p1Me in the PICT state kinetically favors both fluorescence and photoisomerization but disfavors the single-bond torsion. The resulting concept of thermodynamically allowed but kinetically inhibited TICT formation could also apply to understanding the other D-A systems, including trans-4-cyano-4'-(N,N-dimethylamino)stilbene (DCS) and 3-(N,N-dimethylamino)benzonitrile (3DMABN).
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Affiliation(s)
- Jye-Shane Yang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617.
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19
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Chiba M, Tsuneda T, Hirao K. Long-range corrected time-dependent density functional study on fluorescence of 4,4′-dimethylaminobenzonitrile. J Chem Phys 2007; 126:034504. [PMID: 17249881 DOI: 10.1063/1.2426335] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Dual fluorescence of 4,4(')-dimethylaminobenzonitrile (DMABN) was theoretically investigated on the basis of long-range corrected time-dependent density functional theory. Excited-state geometry optimization states and single-point energy calculations with and without solvent effect were carried out. It has been explained that DMABN emits dual fluorescence only in polar solvents through locally excited (LE) and charge transfer (CT) states. It was, however, concluded from this study that although the main spectrum of dual fluorescence in acetonitrile solvent is clearly due to twisted intramolecular CT fluorescence, small secondary fluorescence in acetonitrile may also emanate from CT fluorescence during the DMABN twisting process. This conclusion is supported by an experimental interpretation on polarization spectroscopy. It was also found that the optimized DMABN geometries have certain wagging angles for the CT state and no wagging angle for the LE state. This may support an early experimental hypothesis that the dual fluorescence of DMABN is induced by the wagging mode due to vibronic coupling between LE and CT states. Consequently, the authors propose a fluorescence mechanism of DMABN in gas phase and in acetonitrile solvent: the main absorption proceeds to the CT state in both situations. In gas phase, single fluorescence is chiefly emitted from the LE state through the internal conversion from CT to LE states. Dual fluorescence in acetonitrile solvent may only be emitted from the CT state.
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Affiliation(s)
- Mahito Chiba
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
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20
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Fuss W, Schmid WE, Kuttan Pushpa K, Trushin SA, Yatsuhashi T. Ultrafast relaxation and coherent oscillations in aminobenzonitriles in the gas phase probed by intense-field ionization. Phys Chem Chem Phys 2007; 9:1151-69. [PMID: 17325762 DOI: 10.1039/b611877a] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
4-Aminobenzonitrile derivatives have two excited states of similar energy: besides the benzene-like L(b) state (also termed "locally excited" or LE state) one with charge-transfer (CT) character that is slightly higher in the isolated molecules. The CT state can be lowered by solvents of suitable polarity, so that dual fluorescence can be observed in them. It is controversial along which coordinate this state is displaced, although the amino-group twist is a wide-spread assumption. We investigated a number of such compounds by transient ionization in the gas phase, initially exciting the higher-lying L(a) state (S(2)). Here we briefly review the previous results on 4-(dimethylamino)benzonitrile (the prototype of this class of molecules), 4-piperidino-, pyrrolidino- and pyrrolyl-benzonitrile and compare them with new results on 4-aminobenzonitrile and on the bridged derivative N-methyl-6-cyano-1,2,3,4-tetrahydroquinoline (NMC6). Although in the latter two molecules the CT state has never been detected before, we find the same relaxation path for all compounds: From S(2), the wave packet passes through a conical intersection (CI); from there part of it reaches the S(1) (L(b)) state directly, whereas another part temporarily populates the CT state (also in NMC6), from where it goes around the CI also to the L(b) well. The wave packet directly reaching the L(b) well oscillates there along coordinates involving amino-group twist and wagging or molecular arching and a quinoidal distortion. These coordinates must be components of the CI displacement vector. A vibration involving bond-length alternation of the benzene ring is ascribed to a momentum caused by the electronic symmetry change in the CI, i.e., to the nonadiabatic coupling vector. Also the CT state involves amino-group twist, as to conclude from the anisotropy of the corresponding signal. The six-membered aliphatic ring in NMC6 hinders the twist and raises the CT state to an energy that is, however, still below the L(a) state, so that it can be temporarily populated in a barrierless process. Also in aminobenzonitrile the CT state is between L(a) and L(b) and is reached from L(a) without a barrier. The twist is rationalized by vibronic interaction with a higher state that is pi-antibonding between the amino group and the aromatic ring.
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Affiliation(s)
- Werner Fuss
- Max-Planck-Institut für Quantenoptik, D-85741 Garching, Germany
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Yang JS, Liau KL, Hwang CY, Wang CM. Photoinduced Single- versus Double-Bond Torsion in Donor−Acceptor−Substituted trans-Stilbenes. J Phys Chem A 2006; 110:8003-10. [PMID: 16805484 DOI: 10.1021/jp060296g] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electronic absorption and fluorescence spectra, quantum yields for fluorescence (Phi(f)) and trans --> cis photoisomerization (Phi(tc)), and fluorescence lifetimes of trans-4-(N-arylamino)-4'-cyanostilbenes (2H, 2Me, 2OM, 2CN, and 2Xy with aryl = phenyl, 4-methylphenyl, 4-methoxyphenyl, 4-cyanophenyl, and 2,5-dimethylphenyl, respectively), trans-4-(N-methyl-N-phenylamino)-4'-cyanostilbene (2MP), trans-4-(N,N-diphenylamino)-4'-cyanostilbene (2PP), trans-4-(N-methyl-N-phenylamino)-4'-nitrostilbene (3MP), and three ring-bridged analogues 2OMB, 2MPB, and 3MPB are reported. Whereas fluorescence and torsion of the central double bond account for the excited decay of the majority of these donor-acceptor substituted stilbenes in both nonpolar and polar solvents (i.e., Phi(f) + 2Phi(tc) approximately 1), exceptions are observed for 2OM, 3MP, and 3MPB in solvents more polar than THF and for 2Me and 2MP in acetonitrile as a result of the formation of a weakly fluorescent and isomerization-free twisted intramolecular charge transfer (TICT) state (i.e., Phi(f) + 2Phi(tc) << 1). The TICT state for 2OM, 2Me, and 2MP results from the torsion of the stilbenyl-anilino C-N single bond, but the torsion of the styryl-anilino C-C bond is more likely to be responsible for the TICT state formation of 3MP and 3MPB. In conjunction with the behavior of aminostilbenes 1, a guideline based on the values of Phi(f) and Phi(tc) for judging the importance of a TICT state for trans-stilbenes is provided. Accordingly, the TICT state formation is unimportant for the excited decay of trans-4-(N,N-dimethylamino)-4'-cyanostilbene (DCS). In contrast, our results support the previously proposed TICT state for trans-4-(N,N-dimethylamino)-4'-nitrostilbene (DNS).
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Affiliation(s)
- Jye-Shane Yang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617.
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Druzhinin SI, Ernsting NP, Kovalenko SA, Lustres LP, Senyushkina TA, Zachariasse KA. Dynamics of Ultrafast Intramolecular Charge Transfer with 4-(Dimethylamino)benzonitrile in Acetonitrile. J Phys Chem A 2005; 110:2955-69. [PMID: 16509618 DOI: 10.1021/jp054496o] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The kinetics of the intramolecular charge-transfer (ICT) reaction of 4-(dimethylamino)benzonitrile (DMABN) in the polar solvent acetonitrile (MeCN) is investigated by fluorescence quantum yield and picosecond time-correlated single photon counting (SPC) experiments over the temperature range from -45 to +75 degrees C, together with femtosecond Sn <-- S1 transient absorption measurements at room temperature. For DMABN in MeCN, the fluorescence from the locally excited (LE) state is strongly quenched, with an unquenched to quenched fluorescence quantum yield ratio of 290 at 25 degrees C. Under these conditions, even very small amounts of the photoproduct 4-(methylamino)benzonitrile (MABN) severely interfere, as the LE fluorescence of MABN is in the same spectral range as that of DMABN. The influence of photoproduct formation could be overcome by a simultaneous analysis of the picosecond and photostationary measurements, resulting in data for the activation barriers Ea (5 kJ/mol) and Ed (32 kJ/mol) of the forward and backward ICT reaction as well as the ICT reaction enthalpy and entropy: DeltaH (-27 kJ/mol) and DeltaS [-38 J/(mol K)]. The reaction hence takes place over a barrier, with double-exponential fluorescence decays, as to be expected in a two-state reaction. From femtosecond transient absorption down to 200 fs, the LE and ICT excited state absorption (ESA) spectra of DMABN in n-hexane (LE) and in MeCN (LE and ICT) and also of 4-aminobenzonitrile in MeCN (LE) are obtained. For DMABN in MeCN, the quenching of the LE and the rise of the ICT ESA bands occurs with a single characteristic time of 4.1 ps, the same as the ICT reaction time found from the picosecond SPC experiments at 25 degrees C. The sharp ICT peak at 320 nm does not change its spectral position after a pump-probe delay time of 200 fs, which suggests that large amplitude motions do not take place after this time. The increase with time in signal intensity observed for the LE spectrum of DMABN in n-hexane between 730 and 770 nm, is attributed to solvent cooling of the excess excitation energy and not to an inverse ICT --> LE reaction, as reported in the literature.
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Affiliation(s)
- Sergey I Druzhinin
- Max-Planck-Institut für biophysikalische Chemie, Spektroskopie und Photochemische Kinetik, 37070 Göttingen, Germany.
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