Ultrafast Intersystem-Crossing Dynamics and Breakdown of the Kasha–Vavilov’s Rule of Naphthalenediimides

The fluorescence quantum yield of a red naphthalenediimide dye (rNDI) with amino and Br core substituents has been found to decrease by a factor of almost 2 by going from S1 ← S0 to S2 ← S0 excitation. Time-resolved spectroscopic measurements reveal that this deviation from the Kasha–Vavilov’s rule...

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Published in:The journal of physical chemistry letters 2015-06, Vol.6 (11), p.2096-2100
Main Authors: Yushchenko, Oleksandr, Licari, Giuseppe, Mosquera-Vazquez, Sandra, Sakai, Naomi, Matile, Stefan, Vauthey, Eric
Format: Article
Language:English
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Summary:The fluorescence quantum yield of a red naphthalenediimide dye (rNDI) with amino and Br core substituents has been found to decrease by a factor of almost 2 by going from S1 ← S0 to S2 ← S0 excitation. Time-resolved spectroscopic measurements reveal that this deviation from the Kasha–Vavilov’s rule is due to an ultrafast, < 200 fs, intersystem-crossing (ISC) from the S2 state to the triplet manifold, due to the ππ* → nπ* character of the transition and to the presence of the heavy Br atom. In non-core substituted naphthalenediimide (pNDI), ISC is slower, ∼2 ps, and was found to be reversible on a time scale shorter than that of vibrational cooling. The fluorescence and triplet quantum yields of rNDI, thus, can be substantially changed by a simple variation of the excitation wavelength.
ISSN:1948-7185
1948-7185
DOI:10.1021/acs.jpclett.5b00882