Steady state and time-resolved studies on the redox behaviour of 1,8-naphthalimide in the excited state

Abstract

The redox behaviour of 1,8-naphthalimide in its first excited singlet state is investigated by steady state and time-resolved studies. Efficient fluorescence quenching of this compound by aromatics and amines is interpreted in terms of a charge transfer mechanism. It is shown that the fluorescence quenching in some cases proceeds through exciplex formation. Weak exciplex emission is seen even in polar solvent such as acetonoitrile. Picosecond time-resolved transient absorption studies enables characterization of S₁→S_n absorption of the 1,8-napthalimide compound, and the temporal behaviour of the transient absorption in polar solvents led us to believe that ionic products are exclusively formed from the singlet state. In non-polar solvents, the lack of observation of the ionic products is explained in terms of geminate recombination.