Attachment of a 1,8‐Naphthalimide Moiety to a Conjugated Polythiophene Efficiently Improves the Sensing Abilities of Naphthalimide‐Based Materials

A novel polythiophene-based conjugated polymer bearing 1,8-naphthalimide-based pendants is prepared by a two-step modification of regioregular poly[3-(6-bromohexyl)thiophene] involving a nucleophilic substitution reaction of the bromide end-groups with sodium azide followed by a robust, copper-catalyzed Huisgen click reaction with a novel 1,8-naphthalinmide derivative containing an active, N-substituted propyne group. Both the polymer and the highly luminescent-active synthesized dye are extensively studied in solution by UV-vis spectroscopy, photoluminescence, NMR, light-scattering and isothermal titration calorimetry. The materials prepared are considered potential chemosensors for different transition metals, such as Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+. Luminescence quenching shows that these materials have a higher sensitivity to Fe2+ than to the other metal ions tested. Moreover, the 1,8-naphthalimide-based conjugated polymer is more efficiently quenched by Fe2+ metal ions, at a significantly lower concentration and with a higher binding constant than its parent 1,8-naphthalimide derivative, thus indicating a high potential for sensor development.