Rendering a calixarene having dipyridyl pendants soluble in water results in different species with smaller binding constants

Sulfonato groups were introduced into the backbone of a dipyridyl-based calixarene to obtain a novel water-soluble compound able to complex Co(II) and Cu(II). Spectrophotometric titrations pointed out that the new ligand complexes Co(II) and Cu(II) in water, but with stoichiometries and stabilities that are different from the analogous water insoluble calixarene.