A Dual Signalling On-Off Quinoline Imidazole Conjugate: a Fluorescent Chemosensor for Fe²⁺and Hg²⁺ Ions and...

Quinoline imidazole conjugate (PABIQO) was synthesized by one-pot condensation of benzil with 6-methoxy-2-oxo-quinoline-3-carbaldehyde and ammonium acetate in the presence of a non-toxic and inexpensive catalyst, p-toluene sulphonic acid (PTSA). It has been characterized by ¹H NMR, C¹³ NMR and HRMS and was subjected to absorption and emission studies. The photonics of the compound PABIQO showed selectivity and sensitivity towards Fe²⁺ and Hg²⁺ inCH₃CN: H₂O(1:1v/v) at pH 7.4 in PBS buffer. Fluorescence titration, Jobs Plot and Stern-Volmer analysis confirmed 2:1 binding stoichiometry for Fe²⁺ ions and 1:1for Hg²⁺ ions with a binding constant of 7.36 × 10^-3 M^-1 and 5.080 × 10^-3 M^-1 with a detection limit of 1.75 × 10^-6 M and 1.125 × 10^-6 M respectively with a dual analyte interaction. The stoichiometry ratio was confirmed by HRMS analysis. Further, the compound PABIQO was subjected to density functional studies which were in conformity with the experimental results. Additionally, cytotoxicity studies were also carried out which demonstrated the utility of PABIQO as a fluorescent probe for detecting metal ions in live cells, underscoring its potential for bioanalytical and diagnostic applications.