Electronic processes in hetero-excimers and the mechanism of fluorescence quenching

The electronic processes have been studied in the charge transfer type complex of pyrene and N,N-dimethylaniline, which is formed only in the electronically excited state. The change of the electronic structure of the complex caused by the interaction with the polar solvent molecules has been demonstrated by measuring the fluorescence quantum yield and the fluorescence decay time of the complex in various solvents, and has been interpreted by means of quantum chemical considerations. On the basis of these results, it has been pointed out that a strong charge transfer in the excited state can lead to the fluorescence quenching without the ionic dissociation.