Novel chromogenic ligands for lithium and sodium based on calix[4]arene tetraesters

Abstract

Two new chromogenic calix[4]arene tetraesters bearing nitrophenol residues display a striking cation-selective shift in absorbance maximum from the ultraviolet to the visible region in the presence of base upon addition of lithium ion or, to a lesser extent, sodium ion; the metal salt causes a change from colourless to yellow, the colour density being concentration dependent.