Synthesis, characterisation and complex forming ability towards ferric ions of oligo(ether–amide)s of Jeffamines ED® and chelidamic acid

New chelating oligo(ether–amide)s (CA–PE)s containing chelidamic acid residues in the main chain were prepared by reacting chelidamic acid with Jeffamines ED® in the presence of N,N′-dicyclohexylcarbodiimide and 4-dimethylaminopyridine. A mixture of products having one or two polyether sequences with chelidamate end-groups was obtained. It was found spectrophotometrically that CA–PE polymers formed a complex with Fe3+ at pH 3–6 having a maximum absorbance in the 472–495 nm range. Fe3+ ion complexes of CA–PE were water soluble, except Fe3+–CA–PE600. The stoichiometric ratio between chelidamic acid residues of oligo(ether–amide)s CA–PE and Fe3+ ions was found to be 2 at pH 5 by the method of shift of equilibrium. A hydroxypyridine structure of the chelidamic acid residues in the complex was suggested.