Synthesis of naphthalimide-based benzothiazole as reversible fluorescent probe for the selective detection of Fe³⁺...

Fluorescent probes are widely employed in metal ion detection because of their high responsiveness and ability to distinguish between different ions. These probes provide continuous, non-invasive monitoring of ions, making them valuable for diagnostic and therapeutic applications. Herein, we synthesized a fluorescent probe 1 having a naphthalimide-benzothiazole skeleton for the selective detection of Fe³⁺ ions. The optical characteristics of the probe exhibit ratiometric behavior in absorption spectroscopy, whereas a "turn-off" fluorescence response is observed upon interaction with Fe³⁺ ions. These perturbations could be attributed to the formation of a metal-probe complex, thereby altering the electronic configuration. Further, the LOD for Fe³⁺ was determined to be 1.05 μM. The probe was found to exhibit reversibility and recyclability in the presence of a chelating agent, EDTA. The electronic structure analysis of the probe and its Fe³⁺ complex was conducted using Density Functional Theory (DFT) methods. It exhibits a decrease in HOMO-LUMO energy gap upon metal coordination, suggesting enhanced stability and reactivity. The probe also exhibits favorable nonlinear optical properties, with a significant hyperpolarizability value, highlighting its potential for optical applications. Additionally, the topological analysis revealed the spatial localization of the electrons in the probe and its complex. To gain biological insights, in silico studies of probe 1 were carried out with DNA and serum proteins such as HSA and BSA, underscoring its dual functionality as both a probe and a potential therapeutic agent. Molecular docking studies further substantiated the favorable interactions between probe 1 and its biological targets (HSA and BSA), thereby confirming its biological relevance and supporting its potential for efficient target-specific delivery in the human body when used as a therapeutic agent.