Preparation of New Bis(8-aminoquinoline) Ligands and Comparison with Bis(8-hydroxyquinoline) Ligands on Their Ability to Chelate CuII and ZnII

New bis(8-aminoquinoline) ligands linked on the C2 carbon atom of both quinolines have been prepared. When the linker includes a one-atom amino group, the corresponding compound is an excellent chelator of Cu-II ions and forms a mononuclear species with high metal ion selectivity relative to Zn-II chelation. This selectivity for Cu-II ions was not observed for a bis(8-hydroxyquinoline) analogue. The chelating properties of these ligands are compared to those of the bis(8-aminoquinoline) ligands with different linkers between their N8 nitrogen atoms. The N8-linked bis(8-aminoquinoline) ligands have a higher affinity for Cu-II when the linker includes a three-atom unit or when the linker is linked directly through the N8 atom. Other ligands, including that with a dimethylamino linker on C2, are less efficient and seem to chelate Cu-II and Zn-II with an affinity that is similar to that for dipicolylamine. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)