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Vibronic effects accelerate the intersystem crossing processes of the through-space charge transfer states in the triptycene bridged acridine–triazine donor–acceptor molecule TpAT-tFFO

Kaminski, Jeremy M.; Rodríguez-Serrano, Angela; Dinkelbach, Fabian; Miranda-Salinas, Hector; Monkman, Andrew P.; Marian, Christel M.

Vibronic effects accelerate the intersystem crossing processes of the through-space charge transfer states in the triptycene bridged acridine–triazine donor–acceptor molecule TpAT-tFFO Thumbnail


Authors

Jeremy M. Kaminski

Angela Rodríguez-Serrano

Fabian Dinkelbach

Christel M. Marian



Abstract

Quantum chemical studies employing combined density functional and multireference configuration interaction methods suggest five excited electronic states to be involved in the prompt and delayed fluorescence emission of TpAT-tFFO. Three of them, a pair of singlet and triplet charge transfer (CT) states (S1 and T1) and a locally excited (LE) triplet state (T3), can be associated with the (Me → N) conformer, the other two CT-type states (S2 and T2) form the lowest excited singlet and triplet states of the (Me → Ph) conformer. The two conformers, which differ in essence by the shearing angle of the face-to-face aligned donor and acceptor moieties, are easily interconverted in the electronic ground state whereas the reorganization energy is substantial in the excited singlet state, thus explaining the two experimentally observed time constants of prompt fluorescence emission. Forward and reverse intersystem crossing between the singlet and triplet CT states is mediated by vibronic spin–orbit interactions involving the LE T3 state. Low-frequency vibrational modes altering the distance and alignment of the donor and acceptor π-systems tune the S1 and T3 states (likewise S2 and T3) into and out of resonance. The enhancement of intersystem crossing due to the interplay of vibronic and spin–orbit coupling is considered a general feature of organic through-space charge-transfer thermally activated delayed fluorescence emitters.

Citation

Kaminski, J. M., Rodríguez-Serrano, A., Dinkelbach, F., Miranda-Salinas, H., Monkman, A. P., & Marian, C. M. (2022). Vibronic effects accelerate the intersystem crossing processes of the through-space charge transfer states in the triptycene bridged acridine–triazine donor–acceptor molecule TpAT-tFFO. Chemical Science, 13(23), https://doi.org/10.1039/d1sc07101g

Journal Article Type Article
Acceptance Date Feb 16, 2022
Online Publication Date May 20, 2022
Publication Date 2022
Deposit Date Jul 19, 2022
Publicly Available Date Mar 29, 2024
Journal Chemical Science
Print ISSN 2041-6520
Electronic ISSN 2041-6539
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 13
Issue 23
DOI https://doi.org/10.1039/d1sc07101g

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