Five novel hydrazones derived from substituted isatins were synthesized as potential anion sensors. Using UV-VIS, FTIR, NMR and fluorescence spectroscopy, these compounds' tautomeric equilibrium and Z-E photoisomerization were studied in DMF and CHCl₃, depending on the hydrazone concentrations, the presence of basic anions and light stimulation. Anion recognition aspects (PF₆-, HSO₄-, Br-, Cl-, NO₃-, F- and CH₃COO-) and these receptors' detection limits were also studied. We also tested the light-stimulated ON-OFF functionality of these compounds in the presence or absence of these anions.
Keywords: UV-Vis spectroscopy; anion sensors; intramolecular interaction; on/off switches.