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Williams ML, Schlesinger I, Jacobberger RM, Wasielewski MR. Mechanism of Ultrafast Triplet Exciton Formation in Single Cocrystals of π-Stacked Electron Donors and Acceptors. J Am Chem Soc 2022; 144:18607-18618. [PMID: 36178390 DOI: 10.1021/jacs.2c08584] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ultrafast triplet formation in donor-acceptor (D-A) systems typically occurs by spin-orbit charge-transfer intersystem crossing (SOCT-ISC), which requires a significant orbital angular momentum change and is thus usually observed when the adjacent π systems of D and A are orthogonal; however, the results presented here show that subnanosecond triplet formation occurs in a series of D-A cocrystals that form one-dimensional cofacial π stacks. Using ultrafast transient absorption microscopy, photoexcitation of D-A single cocrystals, where D is coronene (Cor) or pyrene (Pyr) and A is N,N-bis(3'-pentyl)-perylene-3,4:9,10-bis(dicarboximide) (C5PDI) or naphthalene-1,4:5,8-tetracarboxydianhydride (NDA), results in formation of the charge transfer (CT) excitons Cor•+-C5PDI•-, Pyr•+-C5PDI•-, Cor•+-NDA•-, and Pyr•+-NDA•- in <300 fs, while triplet exciton formation occurs in τ = 125, 106, 484, and 958 ps, respectively. TDDFT calculations show that the SOCT-ISC rates correlate with charge delocalization in the CT exciton state. In addition, time-resolved EPR spectroscopy shows that Cor•+-C5PDI•- and Pyr•+-C5PDI•- recombine to form localized 3*C5PDI excitons with zero-field splittings of |D| = 1170 and 1250 MHz, respectively. In contrast, Cor•+-NDA•- and Pyr•+-NDA•- give triplet excitons in which |D| is only 1240 and 690 MHz, respectively, compared to that of NDA (2091 MHz), which is the lowest energy localized triplet exciton, indicating that the Cor-NDA and Pyr-NDA triplet excitons have significant CT character. These results show that charge delocalization in CT excitons impacts both ultrafast triplet formation as well as the CT character of the resultant triplet states.
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Affiliation(s)
- Malik L Williams
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Itai Schlesinger
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Robert M Jacobberger
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R Wasielewski
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
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Drummond BH, Aizawa N, Zhang Y, Myers WK, Xiong Y, Cooper MW, Barlow S, Gu Q, Weiss LR, Gillett AJ, Credgington D, Pu YJ, Marder SR, Evans EW. Electron spin resonance resolves intermediate triplet states in delayed fluorescence. Nat Commun 2021; 12:4532. [PMID: 34312394 PMCID: PMC8313702 DOI: 10.1038/s41467-021-24612-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 06/22/2021] [Indexed: 11/09/2022] Open
Abstract
Molecular organic fluorophores are currently used in organic light-emitting diodes, though non-emissive triplet excitons generated in devices incorporating conventional fluorophores limit the efficiency. This limit can be overcome in materials that have intramolecular charge-transfer excitonic states and associated small singlet-triplet energy separations; triplets can then be converted to emissive singlet excitons resulting in efficient delayed fluorescence. However, the mechanistic details of the spin interconversion have not yet been fully resolved. We report transient electron spin resonance studies that allow direct probing of the spin conversion in a series of delayed fluorescence fluorophores with varying energy gaps between local excitation and charge-transfer triplet states. The observation of distinct triplet signals, unusual in transient electron spin resonance, suggests that multiple triplet states mediate the photophysics for efficient light emission in delayed fluorescence emitters. We reveal that as the energy separation between local excitation and charge-transfer triplet states decreases, spin interconversion changes from a direct, singlet-triplet mechanism to an indirect mechanism involving intermediate states.
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Affiliation(s)
- Bluebell H Drummond
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
- Centre for Advanced Electron Spin Resonance (CAESR), Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK
| | - Naoya Aizawa
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, Japan
| | - Yadong Zhang
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - William K Myers
- Centre for Advanced Electron Spin Resonance (CAESR), Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK
| | - Yao Xiong
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Matthew W Cooper
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Stephen Barlow
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Qinying Gu
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
| | - Leah R Weiss
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Alexander J Gillett
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
| | - Dan Credgington
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
| | - Yong-Jin Pu
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, Japan
| | - Seth R Marder
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Emrys W Evans
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK.
- Department of Chemistry, Swansea University, Swansea, UK.
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Schlesinger I, Powers-Riggs NE, Logsdon JL, Qi Y, Miller SA, Tempelaar R, Young RM, Wasielewski MR. Charge-transfer biexciton annihilation in a donor-acceptor co-crystal yields high-energy long-lived charge carriers. Chem Sci 2020; 11:9532-9541. [PMID: 34094218 PMCID: PMC8162030 DOI: 10.1039/d0sc03301d] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Organic donor-acceptor (D-A) co-crystals have attracted much interest due to their important optical and electronic properties. Co-crystals having ⋯DADA⋯ π-stacked morphologies are especially interesting because photoexcitation produces a charge-transfer (CT) exciton, D˙+-A˙-, between adjacent D-A molecules. Although several studies have reported on the steady-state optical properties of this type of CT exciton, very few have measured the dynamics of its formation and decay in a single D-A co-crystal. We have co-crystallized a peri-xanthenoxanthene (PXX) donor with a N,N-bis(3-pentyl)-2,5,8,11-tetraphenylperylene-3,4:9,10-bis(dicarboximide) (Ph4PDI) acceptor to give an orthorhombic PXX-Ph4PDI ⋯DADA⋯ π-stacked co-crystal with a CT transition dipole moment that is perpendicular to the transition moments for S n ← S0 excitation of PXX and Ph4PDI. Using polarized, broadband, femtosecond pump-probe microscopy, we have determined that selective photoexcitation of Ph4PDI in the single co-crystal results in CT exciton formation within the 300 fs instrument response time. At early times (0.3 ≤ t ≤ 500 ps), the CT excitons decay with a t -1/2 dependence, which is attributed to CT biexciton annihilation within the one-dimensional ⋯DADA⋯ π-stacks producing high-energy, long-lived (>8 ns) electron-hole pairs in the crystal. These energetic charge carriers may prove useful in applications ranging from photovoltaics and opto-electronics to photocatalysis.
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Affiliation(s)
- Itai Schlesinger
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Natalia E Powers-Riggs
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Jenna L Logsdon
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Yue Qi
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Stephen A Miller
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Roel Tempelaar
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Ryan M Young
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Michael R Wasielewski
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
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Kemp TJ. The Aryl Cation – the Trapping and Characterisation of a Hyper-Reactive Species. PROGRESS IN REACTION KINETICS AND MECHANISM 2019. [DOI: 10.3184/007967403103165431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The article traces the development of the epr and optical spectroscopic characterisation and progressive theoretical understanding of the aryl cation, starting from the initial cryogenic epr study of 2,5-dialkoxyl-4-morpholinophenyl cation, which defined unambiguously its triplet state character, through simple MO, ab initio and DFT calculations on substituted aryl cations, to picosecond laser photolysis studies in fluorinated solvents, noting especially the early and vital contribution of Martyn Symons.
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Affiliation(s)
- Terence J. Kemp
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
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Steiner U. A triplet mechanism for magnetic field modulation of photochemical quantum yields. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19810850311] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ghosh S, Stuart C, Ozarowski A, Misra A, Maki A. ODMR of the photoexcited triplet state of donor–acceptor complexes of naphthalene donor with pyromellitic dianhydride, 1,2,4,5-tetracyanobenzene, and 1,3,5-trinitrobenzene acceptors. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(02)01915-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Misra A, Blair M, Stuart C, Ozarowski A, Casas-Finet JR, Maki AH. Phosphorescence and Optically Detected Magnetic Resonance of Polynucleotide Complexes of Tryptophan- and 5-Methyltryptophan-Containing Peptide Stereoisomers. J Phys Chem B 2002. [DOI: 10.1021/jp013879t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ajay Misra
- Department of Chemistry, University of California, Davis, California 95616, and AIDS Vaccine Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201
| | - Michael Blair
- Department of Chemistry, University of California, Davis, California 95616, and AIDS Vaccine Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201
| | - Christina Stuart
- Department of Chemistry, University of California, Davis, California 95616, and AIDS Vaccine Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201
| | - Andrzej Ozarowski
- Department of Chemistry, University of California, Davis, California 95616, and AIDS Vaccine Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201
| | - Jose R. Casas-Finet
- Department of Chemistry, University of California, Davis, California 95616, and AIDS Vaccine Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201
| | - August H. Maki
- Department of Chemistry, University of California, Davis, California 95616, and AIDS Vaccine Program, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Maryland 21702-1201
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Kozankiewicz B, Al-Abbas J, Prochorow J. Migration of electronic excitation energy in the charge-transfer crystal of pyromellitic dianhydride-phenanthrene. Chem Phys Lett 1995. [DOI: 10.1016/0009-2614(95)00162-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Fukazawa N, Fukumura H, Masuhara H, Prochorow J. A picosecond diffuse reflectance laser photolysis study on phenanthrene—pyromellitic dianhydride charge-transfer crystal. Chem Phys Lett 1994. [DOI: 10.1016/0009-2614(94)00205-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Gundel D, Frick J, Krzystek J, Sixl H, von Schütz J, Wolf H. A quasi-neutral triplet state of TCNQ in phenazine/TCNQ and fluorene/TCNQ CT crystals. Chem Phys 1989. [DOI: 10.1016/0301-0104(89)80030-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Steidl P, von Borczyskowski C, Fujara F, Prass B, Stehlik D. Photochemical reactions in doped fluorene single crystals involving hydrogen abstraction in different reaction geometries. J Chem Phys 1988. [DOI: 10.1063/1.454157] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Kozankiewicz B. The origin of delayed fluorescence in charge-transfer crystals: pyromellitic dianhydride-phenanthrene crystal. Chem Phys Lett 1987. [DOI: 10.1016/0009-2614(87)87145-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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The 1:1 charge-transfer crystal fluorene-1,2,4,5-tetracyanobenzene (F-TCNB): triplet excitons, optical and structural properties. Chem Phys 1986. [DOI: 10.1016/0301-0104(86)87001-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Bos FC, Schmidt J. Photoinduced reorientation in an electron donor–acceptor complex: An optically detected ENDOR study of triplet traps in anthracene/tetracyanobenzene. J Chem Phys 1986. [DOI: 10.1063/1.450604] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Agranovich V, Gartstein Y, Zakhidov A, Bussimer P. An adiabatic local model for the internal structure of charge-transfer excitons: Dimers and trimers. Chem Phys Lett 1984. [DOI: 10.1016/0009-2614(84)85227-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Agostini G, Corvaja C, Giacometti G, Pasimeni L. ESR and DF ODMR studies of photoexcited triplets in single crystals of t-stilbene-1,2,4,5-tetracyanobenzene (1:2) complex. Chem Phys 1984. [DOI: 10.1016/0301-0104(84)85269-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Metzger RM. Madelung energy and theoretical zero‐field splittings of (2:1) tetramethyltetraselenafulvalenium hexafluorophosphate [(TMTSF)2PF6]. J Chem Phys 1981. [DOI: 10.1063/1.441842] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Evaluation of the triplet fine structure tensor in the DA-complex anthracene-PMDA by triplet-doublet resonance (TDR) recorded in the photocurrent. Chem Phys 1979. [DOI: 10.1016/0301-0104(79)85133-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Magnetic Properties of Triplet States. ACTA ACUST UNITED AC 1979. [DOI: 10.1016/b978-0-12-227204-2.50007-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2023]
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Radical pair formation from excited states in doped aromatic crystals. I. Epr studies of the guest-host system acridine-fluorene. Chem Phys 1979. [DOI: 10.1016/0301-0104(79)85101-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Keijzers CP, Bagus PS, Worth JP. Self‐consistent field molecular orbital wavefunctions for the ground and excited states of the PMDA molecule. J Chem Phys 1978. [DOI: 10.1063/1.437124] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Keijzers CP, Duran J, Haarer D. Spin polarization of charge‐transfer triplet excitons in phenanthrene–PMDA single crystals. J Chem Phys 1978. [DOI: 10.1063/1.437061] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Soos ZG, Keller HJ, Moroni W, Nöthe D. PHENAZINE CATION RADICAL SALTS: CHARGE-TRANSFER COMPLEXES WITH TCNQ. Ann N Y Acad Sci 1978. [DOI: 10.1111/j.1749-6632.1978.tb39437.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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