Design, synthesis and sensor activity of a highly photostable blue emitting 1,8-naphthalimide

This work reports on the design, synthesis and photophysical properties of a highly photostable blue emitting 1,8-naphthalimide, containing hindered amine radical scavenger moiety and a tertiary amine cation receptor. The novel compound was configured as “fluorophore-spacer-receptor” system based on photoinduced electron transfer. Photophysical characteristics of the examined compound were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compound to detect cations was evaluated by the changes in its fluorescence intensity in the presence of metal ions (Cu2+, Pb2+, Cd2+, Ni2+, Co2+, Fe3+ and Zn2+) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer resulting in enhancement of the 1,8-naphthalimide fluorescence intensity. Among the tested metal ions only Cu2+ was efficiently detected. Also, it is clearly shown that the 2,2,6,6-tetramethylpiperidine fragment, incorporated in the structure of the novel 1,8-naphthalimide, considerably improves the sensorʹs photostability, sensitivity and selectivity.