The increasing interest in the synthesis of aza crown compounds due to their important diverse application in supramolecular chemistry 1, 2, 3, 4 and 5 stimulates the imaginative skill of synthetic chemists. Various changes have been made to the basic crown ether structure in order to enhance the selectivity of the ligands and the stability of complexes formed with both metal and organic cations and to use them as models of protein–metal binding sites in biological systems, 6, ...
