Synthesis and studies of selective chemosensors for anions and cations by azo-containing salicylaldimine-based receptors

Abstract

Three new chromogenic receptors containing electron-withdrawing groups appended to the azophenol moiety were synthesized, characterized, and their chromogenic behavior toward various anions and cations investigated. These chemosensors show visual changes towards biologically relevant anions like F⁻ and OH⁻, and also towards various cations such as Cu²⁺, Co²⁺, Ni²⁺, Mn²⁺, and Zn²⁺. Yet, other anions such as Cl⁻, Br⁻, and NO₃ ⁻ could not cause any color change. The sensing action was further confirmed by UV–Vis titration. ¹H-NMR experiments were carried out to explore the nature of interaction between receptors with F⁻ and OH⁻. The binding constants (K _a) of the host–guest complexes formed were determined.

Keywords:

• Chemosensor
• Transition metal azo complexes
• Receptors

Acknowledgement

The authors would like to thank the Research Council of Arak University for financial support of this research.