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Issue 12, 2020

Exploiting trifluoromethyl substituents for tuning orbital character of singlet and triplet states to increase the rate of thermally activated delayed fluorescence

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Abstract

This work shows that trifluoromethyl (CF3) substituents can be used to increase the rate of thermally activated delayed fluorescence (TADF) in conjugated organic molecules by tuning the excitonic character of the singlet and triplet excited states. The synthesis and detailed photophysical characterization of four new functionalized donor–acceptor–donor (D–A–D) compounds using CF3-substituted-thioxanthene-S,S-dioxide and dimethylacridine units are presented. Several compounds are reported to exhibit rapid blue/green thermally activated delayed fluorescence with major delayed fluorescence lifetime components of ≈1–2 μs. Changes in the orbital character of singlet and triplet states (local vs. charge transfer) result in significant changes in rates of delayed fluorescence, despite similar ΔEST values. The change in orbital character is well supported by TD-DFT calculations. Electrochemical measurements reveal strong shifts in redox potentials that can be induced by σ-electron withdrawing CF3 substituents. Trifluoromethyl substituted compounds with a wider ΔEST also perform more efficiently than might be expected due to the demonstrated changes in excited state character. This study reveals important photophysical and molecular design implications for the future development of TADF emitters.

Graphical abstract: Exploiting trifluoromethyl substituents for tuning orbital character of singlet and triplet states to increase the rate of thermally activated delayed fluorescence

Supplementary files

Article information


Submitted
29 Jun 2020
Accepted
22 Jul 2020
First published
29 Jul 2020

This article is Open Access

Mater. Chem. Front., 2020,4, 3602-3615
Article type
Research Article

Exploiting trifluoromethyl substituents for tuning orbital character of singlet and triplet states to increase the rate of thermally activated delayed fluorescence

J. S. Ward, A. Danos, P. Stachelek, M. A. Fox, A. S. Batsanov, A. P. Monkman and M. R. Bryce, Mater. Chem. Front., 2020, 4, 3602 DOI: 10.1039/D0QM00429D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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