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Spin-Vibronic Intersystem Crossing and Molecular Packing Effects in Heavy Atom Free Organic Phosphor

Lookup NU author(s): Dr Thomas PopeORCiD, Dr Julien EngORCiD, Professor Thomas Penfold



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


We present a detailed investigation into the excited state properties of a planar D3h symmetric azatriangulenetrione, HTANGO, which has received significant interest due to its high solid-state phosphorescence quantum yield and therefore potential as an organic room temperature phosphorescent (ORTP) dye. Using a model linear vibronic coupling Hamiltonian in combination with quantum dynamics simulations, we observe that intersystem crossing (ISC) in HTANGO occurs with a rate of āˆ¼1010 sāˆ’1, comparable to benzophenone, an archetypal molecule for fast ISC in heavy metal free molecules. Our simulations demonstrate that the mechanism for fast ISC is associated with the high density of excited triplet states which lie in close proximity to the lowest singlet states, offering multiple channels into the triplet manifold facilitating rapid population transfer. Finally, to rationalize the solid-state emission properties, we use quantum chemistry to investigate the excited state surfaces of the HTANGO dimer, highlighting the influence and importance of the rotational alignment between the two HTANGO molecules in the solid state and how this contributes to high phosphorescence quantum yield.

Publication metadata

Author(s): Pope T, Eng J, Monkman A, Penfold TJ

Publication type: Article

Publication status: Published

Journal: Journal of Chemical Theory and Computation

Year: 2024

Volume: 20

Issue: 3

Pages: 1337ā€“1346

Online publication date: 25/01/2024

Acceptance date: 04/01/2024

Date deposited: 26/01/2024

ISSN (print): 1549-9618

ISSN (electronic): 1549-9626

Publisher: American Chemical Society


DOI: 10.1021/acs.jctc.3c01220


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