The photophysical Characterisation of Novel 3,9-Dialkyloxy- and Diacyloxyperylenes.

The fundamental photophysical properties of three symmetrically substituted 3,9-perylene analogues were examined in a diverse range of solvents. All three compounds exhibited solvent-dependent fluorescence quantum yield, which was lower than that of perylene or its diimides. Whilst the absence of a large excited state dipole moment suggests that there is no preferential charge accumulation in one side of the molecules, the data suggest that intramolecular electron transfer occurs and that such an event causes additional photochemical mechanisms in chlorinated compounds where the fluorescence quantum yield is lower than in all other solvents and the values of the fluorescence decay change significantly. The dyes could be an interesting new class of fluorescence tags for labeling biomolecules and as dyes for organic photovoltaic materials.