Excited State Dynamics of Thermally Activated Delayed Fluorescence from an Excited State Intramolecular Proton Transfer System

Long, Yun; Mamada, Masashi; Li, Chunyong; dos Santos, Paloma Lays; Colella, Marco; Danos, Andrew; Adachi, Chihaya; Monkman, Andrew

doi:10.1021/acs.jpclett.0c00498

Excited State Dynamics of Thermally Activated Delayed Fluorescence from an Excited State Intramolecular Proton Transfer System

Long, Yun; Mamada, Masashi; Li, Chunyong; dos Santos, Paloma Lays; Colella, Marco; Danos, Andrew; Adachi, Chihaya; Monkman, Andrew

Authors

Yun Long

Masashi Mamada

Dr Chunyong Li chunyong.li@durham.ac.uk
Laser Science Experimental Officer

Paloma Lays dos Santos

Marco Colella

Dr Andrew Danos andrew.danos@durham.ac.uk
Senior Experimental Officer

Chihaya Adachi

Professor Andrew Monkman a.p.monkman@durham.ac.uk
Professor

Abstract

We describe the photophysical processes that give rise to thermally activated delayed fluorescence in the excited state intramolecular proton transfer (ESIPT) molecule, triquinolonobenzene (TQB). Using transient absorption and time-resolved photoluminescence spectroscopy, we fully characterize prompt and delayed emission, phosphorescence, and oxygen quenching to reveal the reverse intersystem crossing mechanism (rISC). After photoexcitation and rapid ESIPT to the TQB-TB tautomer, emission from S1 is found to compete with thermally activated ISC to an upper triplet state, T2, very close in energy to S1 and limiting photoluminescence quantum yield. T2 slowly decays to the lowest triplet state, T1, via internal conversion. In the presence of oxygen, T2 is quenched to the ground state of the double proton transferred TQB-TC tautomer. Our measurements demonstrate that rISC in TQB occurs from T2 to S1 driven by thermally activated reverse internal conversion from T1 to T2 and support recent calculations by Cao et al. (Cao, Y.; Eng, J.; Penfold, T. J. Excited State Intramolecular Proton Transfer Dynamics for Triplet Harvesting in Organic Molecules.

Citation

Long, Y., Mamada, M., Li, C., dos Santos, P. L., Colella, M., Danos, A., …Monkman, A. (2020). Excited State Dynamics of Thermally Activated Delayed Fluorescence from an Excited State Intramolecular Proton Transfer System. Journal of Physical Chemistry Letters, 11(9), 3305-3312. https://doi.org/10.1021/acs.jpclett.0c00498

Journal Article Type	Article
Acceptance Date	Apr 3, 2020
Online Publication Date	Apr 15, 2020
Publication Date	May 7, 2020
Deposit Date	Apr 20, 2020
Publicly Available Date	Apr 21, 2020
Journal	Journal of Physical Chemistry Letters
Publisher	American Chemical Society
Peer Reviewed	Peer Reviewed
Volume	11
Issue	9
Pages	3305-3312
DOI	https://doi.org/10.1021/acs.jpclett.0c00498

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