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Conformational, Host, and Vibrational Effects Giving Rise to Dynamic TADF Behavior in the Through-Space Charge Transfer, Triptycene Bridged Acridine-Triazine Donor Acceptor TADF Molecule TpAT-tFFO

Miranda-Salinas, Hector; Rodriguez-Serrano, Angela; Kaminski, Jeremy M.; Dinkelbach, Fabian; Hiromichi, Nakagawa; Kusakabe, Yu; Kaji, Hironori; Marian, Christel M.; Monkman, Andrew P.

Conformational, Host, and Vibrational Effects Giving Rise to Dynamic TADF Behavior in the Through-Space Charge Transfer, Triptycene Bridged Acridine-Triazine Donor Acceptor TADF Molecule TpAT-tFFO Thumbnail


Authors

Angela Rodriguez-Serrano

Jeremy M. Kaminski

Fabian Dinkelbach

Nakagawa Hiromichi

Yu Kusakabe

Hironori Kaji

Christel M. Marian



Abstract

We present a joint experimental and theoretical study of the through-space charge transfer (CT) TADF molecule TpAT-tFFO. The measured fluorescence has a singular Gaussian line shape but two decay components, coming from two distinct molecular CT conformers, energetically only 20 meV apart. We determined the intersystem crossing rate (1 × 107 s–1) to be 1 order of magnitude faster than radiative decay, and prompt emission (PF) is therefore quenched within 30 ns, leaving delayed fluorescence (DF) observable from 30 ns onward as the measured reverse intersystem crossing (rISC) rate is >1 × 106 s–1, yielding a DF/PF ratio >98%. Time-resolved emission spectra measured between 30 ns and 900 ms in films show no change in the spectral band shape, but between 50 and 400 ms, we observe a ca. 65 meV red shift of the emission, ascribed to the DF to phosphorescence transition, with the phosphorescence (lifetime >1 s) emanating from the lowest 3CT state. A host-independent thermal activation energy of 16 meV is found, indicating that small-amplitude vibrational motions (∼140 cm–1) of the donor with respect to the acceptor dominate rISC. TpAT-tFFO photophysics is dynamic, and these vibrational motions drive the molecule between maximal rISC rate and high radiative decay configurations so that the molecule can be thought to be “self-optimizing” for the best TADF performance.

Citation

Miranda-Salinas, H., Rodriguez-Serrano, A., Kaminski, J. M., Dinkelbach, F., Hiromichi, N., Kusakabe, Y., …Monkman, A. P. (2023). Conformational, Host, and Vibrational Effects Giving Rise to Dynamic TADF Behavior in the Through-Space Charge Transfer, Triptycene Bridged Acridine-Triazine Donor Acceptor TADF Molecule TpAT-tFFO. Journal of Physical Chemistry C, 127(18), 8607-8617. https://doi.org/10.1021/acs.jpcc.2c07529

Journal Article Type Article
Online Publication Date Apr 27, 2023
Publication Date 2023
Deposit Date May 16, 2023
Publicly Available Date May 16, 2023
Journal The Journal of Physical Chemistry C
Print ISSN 1932-7447
Electronic ISSN 1932-7455
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 127
Issue 18
Pages 8607-8617
DOI https://doi.org/10.1021/acs.jpcc.2c07529
Public URL https://durham-repository.worktribe.com/output/1173722

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