A Distinctly Fluorescent Dual Channel Schiff Base Chemosensor for Detecting Noxious Ions in Aqueous Medium

ABSTRACT A new Schiff base chemosensor 2,2'‐((4‐hydroxyphenyl)methylene)bis(azanylylidene))bis(methanylylidene))bis(4‐chlorophenol) (HAMC) derived from 5‐chloro‐2‐hydroxybenzaldehyde is synthesized by one pot synthesis approach and is characterized by IR, UV–visible, 1 H NMR, 13 C NMR, and mass spectral studies. The optimized structure, Mulliken charges, HOMO‐LUMO energy gap and the movement of electrons with the Schiff base chemosensor HAMC is studied by DFT analysis. The results of UV–visible spectral study are further substantiated through TD‐DFT. The cation and anion sensing potential of the Schiff base chemosensor is investigated by absorption and emission methods. The detection experiment is performed in aqueous methanolic medium. The Schiff base chemosensor HAMC is capable of detecting hazardous ions namely Hg(II), Ca(II), CN − , and S 2− . The cation detection process is delineated as due to CHEF effect and hindered ESIPT and with respect to anions the detection is interpreted as due to deprotonation followed by delocalization of electrons. From Job's plot, the coordination/association of the Schiff base sensor HAMC is determined as 1:1 with respect to all detected ions. The limit of detection was found to be in the order of 10 −5 M for both cations and anions. The antimicrobial efficacy of the Schiff base chemosensor HAMC is scrutinized toward antibacterial organisms Staphylococcus aureus , Klebsiella pneumoniae , and antifungal organisms Aspergillus Niger and Candida Albicans . The efficacy is very high toward A. Niger .