Photogeneration of spin quintet triplet–triplet excitations in DNA-assembled pentacene stacks
Photogeneration of spin quintet triplet–triplet excitations in DNA-assembled pentacene stacks
Singlet fission (SF), an exciton-doubling process observed in certain molecular semiconductors where two triplet excitons are generated from one singlet exciton, requires correctly tuned intermolecular coupling to allow separation of the two triplets to different molecular units. We explore this using DNA-encoded assembly of SF-capable pentacenes into discrete π-stacked constructs of defined size and geometry. Precise structural control is achieved via a combination of the DNA duplex formation between complementary single-stranded DNA and the local molecular geometry that directs the SF chromophores into a stable and predictable slip-stacked configuration, as confirmed by molecular dynamics (MD) modeling. Transient electron spin resonance spectroscopy revealed that within these DNA-assembled pentacene stacks, SF evolves via a bound triplet pair quintet state, which subsequently converts into free triplets. SF evolution via a long-lived quintet state sets specific requirements on intermolecular coupling, rendering the quintet spectrum and its zero-field-splitting parameters highly sensitive to intermolecular geometry. We have found that the experimental spectra and zero-field-splitting parameters are consistent with a slight systematic strain relative to the MD-optimized geometry. Thus, the transient electron spin resonance analysis is a powerful tool to test and refine the MD-derived structure models. DNA-encoded assembly of coupled semiconductor molecules allows controlled construction of electronically functional structures, but brings with it significant dynamic and polar disorders. Our findings here of efficient SF through quintet states demonstrate that these conditions still allow efficient and controlled semiconductor operation and point toward future opportunities for constructing functional optoelectronic systems.
5431–5438
Osborne, Sarah R.E.
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Gorman, Jeffrey
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Weiss, Leah R
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Sridhar, Akshay
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Panjwani, Naitik A.
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Divitini, Giorgio
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Budden, Peter
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Palecek, David
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Ryan, Seán T. J.
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Rao, Akshay
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Collepardo-Guevara, Rosana
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El-Sagheer, Afaf
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Brown, Tom
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Behrends, Jan
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Friend, Richard H.
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Auras, Florian
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8 March 2023
Osborne, Sarah R.E.
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Gorman, Jeffrey
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Weiss, Leah R
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Sridhar, Akshay
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Panjwani, Naitik A.
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Divitini, Giorgio
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Budden, Peter
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Palecek, David
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Ryan, Seán T. J.
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Rao, Akshay
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Collepardo-Guevara, Rosana
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El-Sagheer, Afaf
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Brown, Tom
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Behrends, Jan
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Friend, Richard H.
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Auras, Florian
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Osborne, Sarah R.E., Gorman, Jeffrey, Weiss, Leah R, Sridhar, Akshay, Panjwani, Naitik A., Divitini, Giorgio, Budden, Peter, Palecek, David, Ryan, Seán T. J., Rao, Akshay, Collepardo-Guevara, Rosana, El-Sagheer, Afaf, Brown, Tom, Behrends, Jan, Friend, Richard H. and Auras, Florian
(2023)
Photogeneration of spin quintet triplet–triplet excitations in DNA-assembled pentacene stacks.
Journal of the American Chemical Society, 145 (9), .
(doi:10.1021/jacs.2c13743).
Abstract
Singlet fission (SF), an exciton-doubling process observed in certain molecular semiconductors where two triplet excitons are generated from one singlet exciton, requires correctly tuned intermolecular coupling to allow separation of the two triplets to different molecular units. We explore this using DNA-encoded assembly of SF-capable pentacenes into discrete π-stacked constructs of defined size and geometry. Precise structural control is achieved via a combination of the DNA duplex formation between complementary single-stranded DNA and the local molecular geometry that directs the SF chromophores into a stable and predictable slip-stacked configuration, as confirmed by molecular dynamics (MD) modeling. Transient electron spin resonance spectroscopy revealed that within these DNA-assembled pentacene stacks, SF evolves via a bound triplet pair quintet state, which subsequently converts into free triplets. SF evolution via a long-lived quintet state sets specific requirements on intermolecular coupling, rendering the quintet spectrum and its zero-field-splitting parameters highly sensitive to intermolecular geometry. We have found that the experimental spectra and zero-field-splitting parameters are consistent with a slight systematic strain relative to the MD-optimized geometry. Thus, the transient electron spin resonance analysis is a powerful tool to test and refine the MD-derived structure models. DNA-encoded assembly of coupled semiconductor molecules allows controlled construction of electronically functional structures, but brings with it significant dynamic and polar disorders. Our findings here of efficient SF through quintet states demonstrate that these conditions still allow efficient and controlled semiconductor operation and point toward future opportunities for constructing functional optoelectronic systems.
Text
jacs.2c13743
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More information
Accepted/In Press date: 24 February 2023
e-pub ahead of print date: 24 February 2023
Published date: 8 March 2023
Additional Information:
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 670405). This work has been performed using resources provided by the Cambridge Tier-2 system operated by the University of Cambridge Research Computing Service (http://www.hpc.cam.ac.uk), funded by the EPSRC Tier-2 capital grant EP/P020259/1. A.S. and R.C.G. thank funding from the Winton Advanced Research Programme for the Physics of Sustainability. R.H.F., F.A., and Y.L. acknowledge support from the Simons Foundation (grant 601946). L.R.W. thanks funding from the UChicago/AIMR joint research center. A.E.-S. and T.B. acknowledge funding from UK BBSRC grant BB/R008655/1. The authors acknowledge Anthony J. Petty II and John E. Anthony for fruitful discussion on pentacene mesylation and azidification and for providing the 2,9-dibromopentacene.
Identifiers
Local EPrints ID: 476962
URI: http://eprints.soton.ac.uk/id/eprint/476962
ISSN: 0002-7863
PURE UUID: dd821a78-88cc-4062-bef2-51e621e269ff
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Date deposited: 22 May 2023 16:58
Last modified: 12 Sep 2024 01:40
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Contributors
Author:
Sarah R.E. Osborne
Author:
Jeffrey Gorman
Author:
Leah R Weiss
Author:
Akshay Sridhar
Author:
Naitik A. Panjwani
Author:
Giorgio Divitini
Author:
Peter Budden
Author:
David Palecek
Author:
Seán T. J. Ryan
Author:
Akshay Rao
Author:
Rosana Collepardo-Guevara
Author:
Afaf El-Sagheer
Author:
Jan Behrends
Author:
Richard H. Friend
Author:
Florian Auras
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