The deactivation of the singlet excited state of 9-cyano-10-(dimethylamino)anthracene (CDA) in a variety of solvents predominantly takes place by way of internal conversion (IC), with a yield of ∼0.97 in n-propylcyanide, whereas intersystem crossing and intramolecular charge transfer (ICT) only play a minor role. The ICT reaction leads to dual fluorescence, from a locally excited (LE) and a charge transfer (CT) state. The CT/LE fluorescence quantum yield ratio Φ′(CT)/Φ(LE) becomes larger with increasing solvent polarity, from ∼0.1 in cyclopentane to 3.7 in n-propylcyanide at -92°C. The LE and CT fluorescence decays, with shortest decay times of several tens of picoseconds, are measured as a function of temperature and a growing-in of the CT fluorescence is observed at -110°C in n-propylcyanide. The occurrence of IC is connected with the amino twist angle relative to the anthracene plane of CDA in the ground state. The S2 fluorescence reported for CDA in the literature is attributed to the presence of a small amount of a highly fluorescing impurity.
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