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Wega J, Vauthey E. Bimolecular photoinduced symmetry-breaking charge separation of perylene in solution. Photochem Photobiol Sci 2024; 23:93-105. [PMID: 38133700 PMCID: PMC10834668 DOI: 10.1007/s43630-023-00504-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/05/2023] [Indexed: 12/23/2023]
Abstract
Photoinduced symmetry-breaking charge separation (SB-CS) results in the generation of charge carriers through electron transfer between two identical molecules, after photoexcitation of one of them. It is usually studied in systems where the two reacting moieties are covalently linked. Examples of photoinduced bimolecular SB-CS with organic molecules yielding free ions remain scarce due to solubility or aggregation issues at the high concentrations needed to study this diffusion-assisted process. Here we investigate the excited-state dynamics of perylene (Pe) at high concentrations in solvents of varying polarity. Transient absorption spectroscopy on the subnanosecond to microsecond timescales reveal that self-quenching of Pe in the lowest singlet excited state leads to excimer formation in all solvents used. Additionally, bimolecular SB-CS, resulting in the generation of free ions, occurs concurrently to excimer formation in polar media, with a relative efficiency that increases with the polarity of the solvent. Moreover, we show that SB-CS is most efficient in room-temperature ionic liquids due to a charge-shielding effect leading to a larger escape of ions and due to the high viscosity that disfavours excimer formation.
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Affiliation(s)
- Johannes Wega
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1205, Geneva, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1205, Geneva, Switzerland.
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2
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Bertocchi MJ, Bajpai A, Moorthy JN, Weiss RG. New Insights into an Old Problem. Fluorescence Quenching of Sterically-Graded Pyrenes by Tertiary Aliphatic Amines. J Phys Chem A 2017; 121:458-470. [DOI: 10.1021/acs.jpca.6b11382] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Alankriti Bajpai
- Department
of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India
| | - Jarugu N. Moorthy
- Department
of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India
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3
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Ghosh M, Roy B, Majhi K, Mora AK, Nath S, Sinha S. Fluorescence quenching of 9-cyanoanthracene by metallo-octaethylporphyrins in cyanobenzene. J PORPHYR PHTHALOCYA 2015. [DOI: 10.1142/s1088424615500819] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Investigations are carried out on the nature of photoinduced electron transfer reactions within some metallo-octaethylporphyrin (zinc octaethylporphyrin and magnesium octaethylporphyrin) donors and acceptor 9-cyanoanthracene in cyanobenzene at 300 K by steady state and time-resolved spectroscopic methods. Acceptor is selectively excited at 366 nm and 374 nm for steady state and time-resolved measurements, respectively, where donor metalloporphyrins possess negligible absorbance. Evidence is found for simultaneous occurrence of Förster's type singlet–singlet energy transfer process along with electron transfer. High exergonic values of Gibbs free energy change for both forward and back electron transfer reactions indicate the possibility of occurrences of these two consecutive processes in the Marcus inverted region.
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Affiliation(s)
- Mihir Ghosh
- Integrated Science Education and Research Center, Siksha-Bhavana, Visva-Bharati, Santiniketan 731 235, India
| | - Biswajit Roy
- Integrated Science Education and Research Center, Siksha-Bhavana, Visva-Bharati, Santiniketan 731 235, India
| | - Koushik Majhi
- Integrated Science Education and Research Center, Siksha-Bhavana, Visva-Bharati, Santiniketan 731 235, India
| | - Aruna K. Mora
- Radiation & Photochemistry Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India
| | - Sukhendu Nath
- Radiation & Photochemistry Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India
| | - Subrata Sinha
- Integrated Science Education and Research Center, Siksha-Bhavana, Visva-Bharati, Santiniketan 731 235, India
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4
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Rosspeintner A, Vauthey E. Bimolecular photoinduced electron transfer reactions in liquids under the gaze of ultrafast spectroscopy. Phys Chem Chem Phys 2014; 16:25741-54. [PMID: 25356933 DOI: 10.1039/c4cp03862b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Because of their key role in many areas of science and technology, bimolecular photoinduced electron transfer reactions have been intensively studied over the past five decades. Despite this, several important questions, such as the absence of the Marcus inverted region or the structure of the primary reaction product, have only recently been solved while others still remain unanswered. Ultrafast spectroscopy has proven to be extremely powerful to monitor the entire electron transfer process and to access, with the help of state-of-the-art theoretical models of diffusion-assisted reactions, crucial information like e.g. the intrinsic charge separation dynamics beyond the diffusion limit. Additionally, extension of these experimental techniques to other spectral regions than the UV-visible, such as the infrared, has given a totally new insight into the nature, the structure and the dynamics of the key reaction intermediates, like exciplexes and ions pairs. In this perspective, we highlight these recent progresses and discuss several aspects that still need to be addressed before a thorough understanding of these processes can be attained.
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Affiliation(s)
- Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest Ansermet, Geneva, Switzerland.
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Koch M, Letrun R, Vauthey E. Exciplex Formation in Bimolecular Photoinduced Electron-Transfer Investigated by Ultrafast Time-Resolved Infrared Spectroscopy. J Am Chem Soc 2014; 136:4066-74. [DOI: 10.1021/ja500812u] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Marius Koch
- Department
of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Romain Letrun
- Department
of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
| | - Eric Vauthey
- Department
of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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6
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Rosspeintner A, Angulo G, Vauthey E. Bimolecular photoinduced electron transfer beyond the diffusion limit: the Rehm-Weller experiment revisited with femtosecond time resolution. J Am Chem Soc 2014; 136:2026-32. [PMID: 24400958 DOI: 10.1021/ja4118279] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To access the intrinsic, diffusion free, rate constant of bimolecular photoinduced electron transfer reactions, fluorescence quenching experiments have been performed with 14 donor/acceptor pairs, covering a driving-force range going from 0.6 to 2.4 eV, using steady-state and femtosecond time-resolved emission, and applying a diffusion-reaction model that accounts for the static and transient stages of the quenching for the analysis. The intrinsic electron transfer rate constants are up to 2 orders of magnitude larger than the diffusion rate constant in acetonitrile. Above ∼1.5 eV, a slight decrease of the rate constant is observed, pointing to a much weaker Marcus inverted region than those reported for other types of electron transfer reactions, such as charge recombination. Despite this, the driving force dependence can be rationalized in terms of Marcus theory.
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Affiliation(s)
- Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva , 30 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
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7
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Koch M, Rosspeintner A, Adamczyk K, Lang B, Dreyer J, Nibbering ETJ, Vauthey E. Real-Time Observation of the Formation of Excited Radical Ions in Bimolecular Photoinduced Charge Separation: Absence of the Marcus Inverted Region Explained. J Am Chem Soc 2013; 135:9843-8. [DOI: 10.1021/ja403481v] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Marius Koch
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
| | - Arnulf Rosspeintner
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
| | - Katrin Adamczyk
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - Bernhard Lang
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
| | - Jens Dreyer
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - Erik T. J. Nibbering
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211
Geneva 4, Switzerland
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Banerji N, Bhosale SV, Petkova I, Langford SJ, Vauthey E. Ultrafast excited-state dynamics of strongly coupled porphyrin/core-substituted-naphthalenediimide dyads. Phys Chem Chem Phys 2011; 13:1019-29. [DOI: 10.1039/c0cp01544j] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Rosspeintner A, Kattnig DR, Angulo G, Landgraf S, Grampp G. The Rehm-Weller experiment in view of distant electron transfer. Chemistry 2008; 14:6213-21. [PMID: 18506871 DOI: 10.1002/chem.200701841] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The driving-force dependence of bimolecular fluorescence quenching by electron transfer in solution, the Rehm-Weller experiment, is revisited. One of the three long-standing unsolved questions about the features of this experiment is carefully analysed here, that is, is there a diffusional plateau? New experimental quenching rates are compiled for a single electron donor, 2,5-bis(dimethylamino)-1,3-benzenedicarbonitrile, and eighteen electron acceptors in acetonitrile. The data are analysed in the framework of differential encounter theory by using an extended version of the Marcus theory to model the intrinsic electron-transfer step. Only by including the hydrodynamic effect and the solvent structure can the experimental findings be well modelled. The diffusional control region, the "plateau", reveals the inherent distance dependence of the reaction, which is shown to be a general feature of electron transfer in solution.
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Affiliation(s)
- A Rosspeintner
- Graz University of Technology, Technikerstrasse 4/I, 8010 Graz, Austria
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10
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Rothe C, King S, Monkman A. Long-range resonantly enhanced triplet formation in luminescent polymers doped with iridium complexes. NATURE MATERIALS 2006; 5:463-6. [PMID: 16648857 DOI: 10.1038/nmat1630] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Accepted: 03/10/2006] [Indexed: 05/08/2023]
Abstract
The current drive to produce cheap, flexible plastic displays has led to rapid improvements in device efficiency. Inclusion of highly phosphorescent heavy-metal organic complexes as dopants ensures that both singlet and triplet excitations formed on charge recombination can be used efficiently to emit light. However, the inclusion of these dopants affects the photophysics of the host in a surprising way, generating a ten- to twenty- fold instantaneous increase in the number of host triplet states, independent of host triplet energy, quenching up to 95% of all singlet states. Once created however, these triplets are only weakly quenched by the same mechanism. We ascribe this to a resonant, remote intermolecular heavy-atom effect that greatly increases the inter-system crossing rate of the host polymer arising through the strong overlap of the delocalized pi orbitals of the host and ligands. This mechanism competes effectively with Förster energy transfer, and operates over large distances.
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Affiliation(s)
- Carsten Rothe
- O.E.M Research Group, Department of Physics, University of Durham, Durham DH1 3LE, UK
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11
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Pagès S, Lang B, Vauthey E. Ultrafast Excited State Dynamics of the Perylene Radical Cation Generated upon Bimolecular Photoinduced Electron Transfer Reaction. J Phys Chem A 2006; 110:7547-53. [PMID: 16774195 DOI: 10.1021/jp0615252] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ultrafast ground state recovery (GSR) dynamics of the radical cation of perylene, Pe(*+), generated upon bimolecular photoinduced electron transfer in acetonitrile, has been investigated using pump-pump-probe spectroscopy. With 1,4-dicyanobenzene as electron acceptor, the free ion yield is substantial and the GSR dynamics of Pe(*+) was found to depend on the time delay between the first and second pump pulses, Deltat(12), i.e., on the "age" of the ion. At short Deltat(12), the GSR dynamics is biphasic, and at Deltat(12) larger than about 500 ps, it becomes exponential with a time constant around 3 ps. With trans-1,2-dicyanoethylene as acceptor, the free ion yield is essentially zero and the GSR dynamics of Pe(*+) remains biphasic independently of Deltat(12). The change of dynamics observed with 1,4-dicyanobenzene is ascribed to the transition from paired to free solvated ion, because in the pair, the excited ion has an additional decay channel to the ground state, i.e., charge recombination followed by charge separation. The rate constants deduced from the analysis of these GSR dynamics are all fully consistent with this hypothesis.
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Affiliation(s)
- Stéphane Pagès
- Department of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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12
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Investigations of bimolecular photoinduced electron transfer reactions in polar solvents using ultrafast spectroscopy. J Photochem Photobiol A Chem 2006. [DOI: 10.1016/j.jphotochem.2005.12.019] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Levy D, Arnold BR. Analysis of Charge-Transfer Absorption and Emission Spectra on an Absolute Scale: Evaluation of Free Energies, Matrix Elements, and Reorganization Energies. J Phys Chem A 2005; 109:8572-8. [PMID: 16834256 DOI: 10.1021/jp052532d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The relationship between the absorption and emission spectra of the charge-transfer complexes formed between a series of methyl-substituted benzene donors with 1,2,4,5-tetracyanobenzene as acceptor in 1,2-dichloroethane was examined in detail. The association constants for charge-transfer complex formation and the emission quantum yields for these complexes were used to place the experimental absorption and emission spectra on absolute scales. The simultaneous analysis of these spectra is valid only when the Mulliken two-state model is justified. For several of the complexes included in this study the electron-transfer parameters, including the electronic coupling matrix elements, obtained from the analysis of the individual absorption and emission spectra are in close agreement. The simultaneous analysis of the combined absorption and emission spectra leads to a well-defined set of electron-transfer parameters for these complexes. In other complexes, where the two-state model does not apply because of the influence of localized excited states on the absorption spectrum, analysis of the absorption and emission spectra led to significantly different sets of electron-transfer parameters. It is demonstrated that the electronic coupling matrix elements are a very sensitive indicator of the influence of localized excited states on these spectra.
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Affiliation(s)
- Dustin Levy
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA
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14
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Nicolet O, Banerji N, Pagès S, Vauthey E. Effect of the Excitation Wavelength on the Ultrafast Charge Recombination Dynamics of Donor−Acceptor Complexes in Polar Solvents. J Phys Chem A 2005; 109:8236-45. [PMID: 16834210 DOI: 10.1021/jp0532216] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effect of the excitation wavelength on the charge recombination (CR) dynamics of several donor-acceptor complexes (DACs) composed of benzene derivatives as donors and of tetracyanoethylene or pyromellitic dianhydride as acceptors has been investigated in polar solvents using ultrafast time-resolved spectroscopy. Three different wavelength effects have been observed. (1) With complexes exhibiting two well-separated charge-transfer bands, the CR dynamics was found to be slower by a factor of about 1.5 upon excitation in the high-energy band. This effect was measured in both fast and slow relaxing solvents and was discussed in terms of different DAC geometries. (2) When the CR is faster than diffusive solvation, a slowing down of the CR with increasing excitation wavelength accompanied by an increase of the nonexponential character of the dynamics was measured. This effect appears only when exciting on the red edge of the charge-transfer absorption band. (3) When the driving force for CR is small, both nonequilibrium (hot) and thermally activated CR pathways can be operative. The results obtained with such a complex indicate that the relative contribution of these two paths depends on the excitation wavelength.
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Affiliation(s)
- Olivier Nicolet
- Department of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
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15
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Pagès S, Lang B, Vauthey E. Ultrafast Spectroscopic Investigation of the Charge Recombination Dynamics of Ion Pairs Formed upon Highly Exergonic Bimolecular Electron-Transfer Quenching: Looking for the Normal Region. J Phys Chem A 2003. [DOI: 10.1021/jp036796g] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Stéphane Pagès
- Department of Physical Chemistry, University of Geneva, 30 quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Bernhard Lang
- Department of Physical Chemistry, University of Geneva, 30 quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Eric Vauthey
- Department of Physical Chemistry, University of Geneva, 30 quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
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