Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission

Handle URI:
http://hdl.handle.net/10754/625742
Title:
Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission
Authors:
Dean, Jacob C. ( 0000-0002-3047-3197 ) ; Zhang, Ruomeng; Hallani, Rawad K.; Pensack, Ryan D.; Sanders, Samuel N.; Oblinsky, Daniel G.; Parkin, Sean R.; Campos, Luis M.; Anthony, John E.; Scholes, Gregory D. ( 0000-0003-3336-7960 )
Abstract:
Quantitative singlet fission has been observed for a variety of acene derivatives such as tetracene and pentacene, and efforts to extend the library of singlet fission compounds is of current interest. Preliminary calculations suggest anthradithiophenes exhibit significant exothermicity between the first optically-allowed singlet state, S1, and 2 × T1 with an energy difference of >5000 cm−1. Given the fulfillment of this ingredient for singlet fission, here we investigate the singlet fission capability of a difluorinated anthradithiophene dimer (2ADT) covalently linked by a (dimethylsilyl)ethane bridge and derivatized by triisobutylsilylethynyl (TIBS) groups. Photophysical characterization of 2ADT and the single functionalized ADT monomer were carried out in toluene and acetone solution via absorption and fluorescence spectroscopy, and their photo-initiated dynamics were investigated with time-resolved fluorescence (TRF) and transient absorption (TA) spectroscopy. In accordance with computational predictions, two conformers of 2ADT were observed via fluorescence spectroscopy and were assigned to structures with the ADT cores trans or cis to one another about the covalent bridge. The two conformers exhibited markedly different excited state deactivation mechanisms, with the minor trans population being representative of the ADT monomer showing primarily radiative decay, while the dominant cis population underwent relaxation into an excimer geometry before internally converting to the ground state. The excimer formation kinetics were found to be solvent dependent, yielding time constants of ∼1.75 ns in toluene, and ∼600 ps in acetone. While the difference in rates elicits a role for the solvent in stabilizing the excimer structure, the rate is still decidedly long compared to most singlet fission rates of analogous dimers, suggesting that the excimer is neither a kinetic nor a thermodynamic trap, yet singlet fission was still not observed. The result highlights the sensitivity of the electronic coupling element between the singlet and correlated triplet pair states, to the dimer conformation in dictating singlet fission efficiency even when the energetic requirements are met.
KAUST Department:
KAUST Solar Centre, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
Citation:
Dean JC, Zhang R, Hallani RK, Pensack RD, Sanders SN, et al. (2017) Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission. Phys Chem Chem Phys 19: 23162–23175. Available: http://dx.doi.org/10.1039/c7cp03774k.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Phys. Chem. Chem. Phys.
Issue Date:
18-Aug-2017
DOI:
10.1039/c7cp03774k
Type:
Article
ISSN:
1463-9076; 1463-9084
Sponsors:
The authors gratefully acknowledge the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant No. DE-SC0015429. SNS thanks the NSF GRFP for funding (grant DGE 11-44155). JEA and RKH thank the U.S. National Science Foundation (grant CMMI-1255494) for support of organic semiconductor synthesis. Triplet sensitization measurements were done using resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DESC0012704.
Additional Links:
http://pubs.rsc.org/en/Content/ArticleLanding/2017/CP/C7CP03774K#!divAbstract
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DC FieldValue Language
dc.contributor.authorDean, Jacob C.en
dc.contributor.authorZhang, Ruomengen
dc.contributor.authorHallani, Rawad K.en
dc.contributor.authorPensack, Ryan D.en
dc.contributor.authorSanders, Samuel N.en
dc.contributor.authorOblinsky, Daniel G.en
dc.contributor.authorParkin, Sean R.en
dc.contributor.authorCampos, Luis M.en
dc.contributor.authorAnthony, John E.en
dc.contributor.authorScholes, Gregory D.en
dc.date.accessioned2017-10-03T12:49:37Z-
dc.date.available2017-10-03T12:49:37Z-
dc.date.issued2017-08-18en
dc.identifier.citationDean JC, Zhang R, Hallani RK, Pensack RD, Sanders SN, et al. (2017) Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission. Phys Chem Chem Phys 19: 23162–23175. Available: http://dx.doi.org/10.1039/c7cp03774k.en
dc.identifier.issn1463-9076en
dc.identifier.issn1463-9084en
dc.identifier.doi10.1039/c7cp03774ken
dc.identifier.urihttp://hdl.handle.net/10754/625742-
dc.description.abstractQuantitative singlet fission has been observed for a variety of acene derivatives such as tetracene and pentacene, and efforts to extend the library of singlet fission compounds is of current interest. Preliminary calculations suggest anthradithiophenes exhibit significant exothermicity between the first optically-allowed singlet state, S1, and 2 × T1 with an energy difference of >5000 cm−1. Given the fulfillment of this ingredient for singlet fission, here we investigate the singlet fission capability of a difluorinated anthradithiophene dimer (2ADT) covalently linked by a (dimethylsilyl)ethane bridge and derivatized by triisobutylsilylethynyl (TIBS) groups. Photophysical characterization of 2ADT and the single functionalized ADT monomer were carried out in toluene and acetone solution via absorption and fluorescence spectroscopy, and their photo-initiated dynamics were investigated with time-resolved fluorescence (TRF) and transient absorption (TA) spectroscopy. In accordance with computational predictions, two conformers of 2ADT were observed via fluorescence spectroscopy and were assigned to structures with the ADT cores trans or cis to one another about the covalent bridge. The two conformers exhibited markedly different excited state deactivation mechanisms, with the minor trans population being representative of the ADT monomer showing primarily radiative decay, while the dominant cis population underwent relaxation into an excimer geometry before internally converting to the ground state. The excimer formation kinetics were found to be solvent dependent, yielding time constants of ∼1.75 ns in toluene, and ∼600 ps in acetone. While the difference in rates elicits a role for the solvent in stabilizing the excimer structure, the rate is still decidedly long compared to most singlet fission rates of analogous dimers, suggesting that the excimer is neither a kinetic nor a thermodynamic trap, yet singlet fission was still not observed. The result highlights the sensitivity of the electronic coupling element between the singlet and correlated triplet pair states, to the dimer conformation in dictating singlet fission efficiency even when the energetic requirements are met.en
dc.description.sponsorshipThe authors gratefully acknowledge the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy through Grant No. DE-SC0015429. SNS thanks the NSF GRFP for funding (grant DGE 11-44155). JEA and RKH thank the U.S. National Science Foundation (grant CMMI-1255494) for support of organic semiconductor synthesis. Triplet sensitization measurements were done using resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DESC0012704.en
dc.publisherRoyal Society of Chemistry (RSC)en
dc.relation.urlhttp://pubs.rsc.org/en/Content/ArticleLanding/2017/CP/C7CP03774K#!divAbstracten
dc.titlePhotophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fissionen
dc.typeArticleen
dc.contributor.departmentKAUST Solar Centre, King Abdullah University of Science and Technology, Thuwal, Saudi Arabiaen
dc.identifier.journalPhys. Chem. Chem. Phys.en
dc.contributor.institutionDepartment of Chemistry, Princeton University, Princeton, USAen
dc.contributor.institutionDepartment of Chemistry, University of Kentucky, Lexington, USAen
dc.contributor.institutionDepartment of Chemistry, Columbia University, New York, USAen
kaust.authorHallani, Rawad K.en
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