Design, synthesis and evaluation of a new calix[4]arene based molecular receptor for multiple ion selectivity

The hydrophobic and conformational motifs of calix[4]arene stereostructure and plausible binding characteristics of heterocyclic 2-oxo-1,2-dihydroquinoline-4-carbohydrazide have been deployed for the design and synthesis of a new molecular receptor, 4 for multi-ion recognition. The target molecule was synthesized through the condensation of 3 with 2-oxo-1,2-dihydroquinoline-4-carbohydrazide (6) in refluxing ethanol. It has been determined that 4 exhibits an exclusive color change from colorless to yellow as well as a 5.5 fold increase in the fluorescence intensity upon interaction with fluoride due to formation of multiple hydrogen bonds. Consequent to fluoride induced deprotonation, 4 displays a dual selectivity for Cu2+ and Ni2+ ions from amongst plethora of investigated cations.