Design and synthesis of highly photostable fluorescence sensing 1,8-naphthalimide-based dyes containing s-triazine UV absorber and HALS units

Two novel highly photostable yellow-green emitting 1,8-naphthalimide-based dyes, containing active fragments of both a hindered amine radical scavenger (HALS) and an s-triazine UV absorber were designed as multifunctional additives capable of simultaneously chemically fluorescent dyeing and photostabilization of polymers. They showed substantially higher photostability in respect to other similar fluorescent dyes, not containing either UV absorber or HALS component in their molecules. Novel compounds were also configured as "fluorophore-spacer-receptor" systems based on photoinduced electron transfer by incorporation a tertiary cation receptor at the C-4 position of the 1,8-naphthalimide fluorophore. The ability of the new compounds to detect cations was evaluated by the changes in their fluorescence intensity in the presence of metal ions and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer leading to an enhancement in the dye fluorescence intensity. The results obtained indicate the potential of the novel compounds as highly photostable and efficient "off-on" pH switchers and fluorescent detectors for metal ions with pronounced selectivity towards Cu²⁺ ions.