Calix[4]arene based neutral receptor for dihydrogen phosphate anion

A series of novel calix[4]arene hydrazone and semicarbazone based neutral receptors have been synthesized and characterized by IR, UV–vis, and NMR spectroscopies. The preliminary UV–vis and 1H NMR titration experiments revealed that 25,26,27,28-tetrapropoxycalix[4]arene tetra-semicarbazone can recognize H2PO4− through a 1:1 binding-stoichiometry in preference over other anions (Cl−, Br−, I−, HSO4−, ClO4−, and CH3COO−).