A series of naphthalimide derivatives (TNP and TNM) were synthesized by incorporating a triphenylamine unit (TPA) into the chromophore of 1,8-naphthalimide. Their steady-state absorption, fluorescence and transient fluorescence were investigated, indicating that there exist efficient Förster-type singlet energy transfer and photo-induced electron transfer (PIET). As a consequence, the fluorescence of TNP and TNM was quenched distinctly, which is mainly arisen from the intramolecular PIET process between the units of TPA and naphthalimide. The fluorescent tuning on and off can be achieved by the stimuli of acid, which will protonate the central nitrogen atom of triphenylamine unit to stop the PIET process. The mechanism can be utilized as the design of fluorescent switching based on the process of fluorescent quenching and recovering.

Key words: triphenylamine, naphthalimide, fluorescent quenching, luminescence tuning