MIND THE SINGLET-TRIPLET GAP: PHOTOELECTRON SPECTROSCOPY OF 1,3,4,6,9B-PENTAAZAPHENALENE
Wilson, Kenneth
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7115.pdf
MG03_1.pdf
MG03_1.pptx
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https://hdl.handle.net/2142/122606
Description
Title
MIND THE SINGLET-TRIPLET GAP: PHOTOELECTRON SPECTROSCOPY OF 1,3,4,6,9B-PENTAAZAPHENALENE
Author(s)
Wilson, Kenneth
Contributor(s)
Garand, Etienne
Issue Date
2023-06-19
Keyword(s)
Mini-symposium: Spectroscopy with Cryogenic Ion Traps
Abstract
The vast majority of closed-shell organic molecules follow Hund’s rule, namely: their first excited triplet state (T₁) lies energetically below their first excited singlet state (S₁). Recent computational studies, however, suggest that energetic inversion of these states is possible in a family of closed-shell species known as azaphenalenes. The phenomenon is believed to arise from (i) minimal overlap between highest-occupied and lowest-unoccupied molecular orbitals, and (ii) stabilization of the S₁ state via coupling to higher-excited electronic configurations. Despite experimental efforts to confirm S₁-T₁ inversion in an azaphenalene species using optical techniques (1), quantification of the T₁ energy–and thus the S₁-T₁ gap–is precluded by the spin selection rule. Using photoelectron spectroscopy, which circumvents the spin selection rule, we report a S₁-T₁ gap for 1,3,4,6,9b-pentaazaphenalene of either 374 cm−¹ or -374 cm−¹ (± 46 meV), pending definitive assignment of the S state. Once confirmed, these results will have important implications in the fields of organic light-king for high-level quantum chemical calculations of electronically excited states.
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7115.pdf
MG03_1.pdf
MG03_1.pptx
