Excited state properties of bis-1,8-naphthalimides

A series of novel bis-1,8-naphthalimides (bis-1,8-NI), each of which consists of a 4alkylamino-1,8-NI electron donor and an unsubstituted 1,8-NI electron acceptor, has been investigated. Time-resolved fluorescence and fluorescence quantum yields have been measured and the results indicate that fluorescence arising from the 4-alkylamino-1,8-NI residue can be quenched by intramolecular charge transfer from the 4-alkylamino-1,8-NI donor to the un-substituted 1,8-NI acceptor. The transient triplet absorption for the unsubstituted 1,8-NI component in bis-1,8-NI has been studied by selective excitation using a 337 nm N2 laser. We found that triplet quenching is an intramolecular process, and that the triplet quenching rate is faster than that of monomeric 1,8-NI quenched by external aliphatic amine in a solvent.