TY - JOUR AU - Yushchenko, Oleksandr AU - Licari, Giuseppe AU - Mosquera-Vazquez, Sandra AU - Sakai, Naomi AU - Matile, Stefan AU - Vauthey, Eric TI - Ultrafast Intersystem-Crossing Dynamics and Breakdown of the Kasha–Vavilov’s Rule of Naphthalenediimides PY - 2015 JF - Journal of Physical Chemistry Letters JA - J. Phys. Chem. Lett. SN - 1948-7185 VL - 6 IS - 11 SP - 2096 EP - 2100 L1 - http://pubs.acs.org/doi/pdf/10.1021/acs.jpclett.5b00882 L2 - http://pubs.acs.org/doi/full/10.1021/acs.jpclett.5b00882 L3 - http://dx.doi.org/10.1021/acs.jpclett.5b00882 L4 - http://www.unige.ch/sciences/chifi/publis/pics/double/ref01479.png M3 - 10.1021/acs.jpclett.5b00882 UR - http://dx.doi.org/10.1021/acs.jpclett.5b00882 N2 - 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. ID - 1479 ER -