Selective Turn-On Luminescent Recognition of Perchlorate Ion Using Pyridyl-Benzimidazole-Based Probe

Anions play a crucial role in various environmental, chemical, and biological processes. Among various anions, the production of perchlorate (ClO₄ ^-) ion is expected to rise in upcoming years, and thus, an efficient method for the detection of perchlorate ion is highly desirable. In this effort, a pyridyl-benzimidazole-based luminescent probe (RSB1) containing two N-H donor sites has been synthesized for selective detection of perchlorate ion. Different spectral techniques such as FT-IR, NMR, ESI-mass, UV-Vis, and fluorescence analyses have been used to characterize this probe. High selectivity of RSB1 for ClO₄ ^- was realized even in presence of strongly interfering species in aqueous-acetonitrile (CH₃CN-H₂O; 4:1, v/v) solution. Notably, RSB1 served as a "turn-on" perchlorate-responsive probe and exhibited an emission enhancement at 363 nm when excited at 300 nm. The detection limit (LoD) and the binding constant (K_b) values were depicted to be 0.121 μM and 2.6 × 10⁵ M^-1, respectively, while the binding mechanism for RSB1-ClO₄ ^- was validated via Job's plot, NMR, and DFT analyses. Furthermore, this probe was successfully employed to trace perchlorate in real samples such as tap water, distilled water, and soil samples with good to excellent recovery values.