Ion sensing with a calix[4]arene bifunctional receptor with thiosemicarbazone moieties and naphthalene chromophore

We have developed a chemosensor using calix[4]arene, which features a thiosemicarbazone binding/sensing unit and a naphthalene chromogenic group. Our objective was to understand the intricate binding affinity of these chemosensors towards a diverse range of anions and cations using UV–Visible, HNMR and IR spectroscopic techniques. We showed that this chemosensor can form complexes with Ag(I) or Cu (II) and to detect CN⁻ or F⁻ ions by deprotonation of thiosemicarbazone. To understand the behavior of these interactions, our analysis provides information on the interaction patterns between the receptors and the ions. The sulfur and imine nitrogen on the thiosemicarbazone substituent are vital sites of engagement for cation ions, as evidenced by the observed changes in IR. HNMR studies for interaction with anions indicate the involvement of the thiosemicarbazone hydrogens. Interactions taking place during complex formation with cations lead to changes in the color of the solution or solid complex, easy to follow by UV–Vis spectrocopy. Our study improves the understanding of molecular recognition of this chemosensor, highlighting its potential for ion- selective detection.