ESIPT Active Schiff Base Fluorescent Sensor for Selective and Sensitive Detection of Co(II) Ions: Experimental, DFT...

A novel fluorescent Schiff base chemosensor, N'¹,N'⁶-bis((E)-3,5-dibromo-2-hydroxybenzylidene)adipohydrazide (DBSA), has been developed for the detection of Cobalt (II) ions. DBSA exhibits distinct fluorescence enhancement upon interacting with Co(II) ions via photoinduced electron transfer (PET). The developed sensor demonstrates a remarkable sensitivity, with the detection limits of 9.9 nM for Co(II) ions, which aligns well with the Environmental Protection Agency (EPA) regulatory thresholds for drinking water contaminants. Structural characterization by LC-MS, FTIR coupled with Job's plot and NMR titration studies confirm the formation of DBSA-Co complex with a binding constant of 4.61 × 10⁶ M^- 1. The chemo sensor exhibits a quantum yield of 0.082, highlighting its potential applicability in photochemical processes. Computation studies were used to further investigate the binding interactions with Co²⁺ ions. The practical utility of DBSA has been validated through successful analyses in varied aqueous matrices, including tap water, lake water and recycled water. Cytotoxicity assessment via MTT assays on SH-SY5Y cells confirms excellent biocompatibility of the probe. This work presents a significant advancement in the design of efficient molecular probes for environmental monitoring, offering a robust platform for the concurrent detection of transition-metal ions in aqueous systems.