Intermolecular photoinduced electron-transfer of 1,8-naphthalimides in protic polar solvents.

The intermolecular photoinduced electron transfer (PET) processes of 1,8-naphthalimide (NI) derivatives including NI-linker-phenothiazine dyads were investigated in a protic H(2)O/CH(3)CN (v/v=1:1) solvent using ns-laser flash photolysis with 355 nm-laser excitation. NI derivatives are surrounded by H(2)O in the ground state in H(2)O/CH(3)CN. The T(1)-T(n) absorption band of (3)NI* was observed at around 470 nm. The transient absorption band at around 410 nm increased concomitantly with the decay of (3)NI* in H(2)O/CH(3)CN. This implies that hydrated NI anion radical (NI*(-)) is primarily generated via the quenching of (3)NI* by NI at the diffusion control rate. This intermolecular PET did not occur in aprotic CH(3)CN. The formation and decay times of NI*(-) showed strong dependence on the concentration of NI. Then, we suggest that NI*(-) could undergo proton abstraction to give ketyl radical species of NI [NI(H)*] in H(2)O/CH(3)CN.