New N-triazinyl derivatives were synthesized by reaction of cyanuric chloride with 1- and 9-aminoanthracenes and subsequent nucleophilic substitution of chlorine atoms on triazinyl ring with methoxy and/or phenylamino groups. The compounds were characterized by (1)H and (13)C NMR and mass spectra. The influence of the chemical structure and solvent polarity on the UV/Vis absorption and fluorescence spectra and fluorescence quantum yields were investigated. Semi-empirical computations revealed highly polar CT states in singlet excited state manifold connected with charge-transfer from the hydrocarbon moiety to the triazinyl ring. The relationships between the CT-to-emitting state energy gap, solvent polarity and fluorescence quantum yield were discussed.
Fluorescence anisotropy measurements were performed on a set of multichromophoric compounds, which contain a different number of aminopyrenyl moieties linked to a triazine ring, in order to reveal the nature of both the electronic excited states and relaxation pathways of the compounds. Our experimental results complement quantum chemical calculations. We propose that the lowest excited state from which fluorescence proceeds is localized on a single individual aminopyrene moiety. In contrast, excitation to a higher excited state is likely followed by a migration of energy to another nearby aminopyrene chromophore before the internal conversion to the emitting state takes place. We suggest that this migration is responsible for the experimentally measured decrease of fluorescence anisotropy of the studied compounds.
