TY  - JOUR
A1  - Hoche, Joscha
A1  - Schulz, Alexander
A1  - Dietrich, Lysanne Monika
A1  - Humeniuk, Alexander
A1  - Stolte, Matthias
A1  - Schmidt, David
A1  - Brixner, Tobias
A1  - Würthner, Frank
A1  - Mitric, Roland
T1  - The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes
JF  - Chemical Science
N2  - Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM),i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran   (DCBT).   We   measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law.This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier.
KW  - solvent-dependent fluorescence yield
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198707
UR  - https://doi.org/10.1039/C9SC05012D
VL  - 10
ER  -