Unique Naphthalimide‐Imidazole Turn Off Fluorosensor for Selective Sensing of Fe +3 and Bioimaging Applications

ABSTRACT A novel imidazole‐functionalized naphthalimide fluorosensor (NF‐1) is developed for selective and sensitive Fe +3 detection. The NF‐1 exhibited significant fluorescence quenching upon Fe +3 binding, with 63.6% efficiency in a THF‐H₂O (7:3, v/v) solvent system. The Job's plot confirmed 1:1 binding stoichiometry with a binding constant of 5 × 10 10 M −1 . The detection limit was 3.07 μM. The NF‐1 responded immediately to Fe +3 , reaching stability within 60 s. It maintained fluorescence stability over pH 5–12. The [ NF‐1 –Fe +3 ] complex showed consistent quenching across the various pH ranges. The fluorescence is efficiently restored upon EDTA addition followed by confirmation of reversible Fe +3 coordination. The Molecular docking studies revealed strong binding interactions with target enzymes. This indicates the molecule as a potential drug candidate. The DFT calculations showed a HOMO‐LUMO energy gap of −2.94 eV, indicating moderate reactivity. The bioimaging studies confirmed the intracellular Fe +3 detection using this sensor. The MTT assay in A549 cells demonstrated over 85% cell viability at 50 μM. These findings established NF‐1 as an efficient, selective, and reversible Fe +3 sensor suitable for environmental monitoring, real‐time detection, and bioimaging applications.