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

Pope, Thomas; Eng, Julien; Monkman, Andrew; Penfold, Thomas J

Abstract

We present a detailed investigation into the excited state properties of a planar 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 ∼10 s , 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.

Citation

Pope, T., Eng, J., Monkman, A., & Penfold, T. J. (2024). Spin-Vibronic Intersystem Crossing and Molecular Packing Effects in Heavy Atom Free Organic Phosphor. Journal of Chemical Theory and Computation, 20(3), 1337–1346. https://doi.org/10.1021/acs.jctc.3c01220

• Journal Article Type: Article
• Acceptance Date: Jan 4, 2024
• Online Publication Date: Jan 25, 2024
• Publication Date: Feb 13, 2024
• Deposit Date: Mar 14, 2024
• Publicly Available Date: Mar 14, 2024
• Journal: Journal of chemical theory and computation
• Print ISSN: 1549-9618
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 20
• Issue: 3
• Pages: 1337–1346
• DOI: https://doi.org/10.1021/acs.jctc.3c01220
• Public URL: https://durham-repository.worktribe.com/output/2234269