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This content will become publicly available on December 1, 2025

Title: Ultrafast Excited State Dynamics of a Verdazyl Diradical System
While the photophysics of closed-shell organic molecules is well established, much less is known about open-shell systems containing interacting radical pairs. In this work, we investigate the ultrafast excited state dynamics of a singlet verdazyl diradical system in solution using transient absorption (TA) spectroscopy for the first time. Following 510 nm excitation of the excitonic S0 → S1 transition, we detected TA signals in the 530–950 nm region from the S1 population that decayed exponentially within a few picoseconds to form a vibrationally hot S0* population via internal conversion. The dependence of the S1 decay rate on solvent and radical–radical distance revealed that the excited state possesses charge-transfer character and likely accesses the S0 state via torsional motion. The ultrafast internal conversion decay mechanism at play in our open-shell verdazyl diradicals is in stark contrast with other closed-shell, carbonyl-containing organic chromophores, which exhibit ultrafast intersystem crossing to produce long-lived triplet states as the major S1 decay pathway.  more » « less
Award ID(s):
1900491
PAR ID:
10552439
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
MDPI
Date Published:
Journal Name:
Photochem
Volume:
4
Issue:
4
ISSN:
2673-7256
Page Range / eLocation ID:
404 to 416
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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