The Hidden Role of Through-Bond Energy Transfer in FRET-Dyes: A Quantum Dynamics Perspective
Nikita A Shekhovtsov1, Mark B Bushuev1
1Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, 3, Acad. Lavrentiev Ave., Novosibirsk, 630090, Russia.
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Energy transfer in fluorescent donor-acceptor pairs is typically governed by one of two mechanisms: Förster Resonance Energy Transfer (FRET) or Through-Bond Energy Transfer (TBET). In contrast to FRET, TBET has been widely assumed to require π-conjugation between the donor and acceptor units. In this work, we introduce a versatile strategy for simulating nonadiabatic quantum dynamics in large molecular systems and apply it to a dye CouXan featuring a coumarin donor, a xanthene acceptor and a non-π-conjugated diazinane linker. We demonstrate that strong vibronic coupling drives highly efficient TBET with a remarkable rate constant of 6.8 × 1012 s-1 even in the absence of π-conjugation, surpassing the known FRET rate (8.0 × 1010 s-1) by 2 orders of magnitude. This finding challenges the present understanding of energy transfer in donor-acceptor pairs and reveals that classical FRET architectures can harbor ultrafast through-bond channels of exciton deactivation.
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