Anion Control Selectivity of Neutral N4-Type Schiff Base Extractants Towards Transition Metal Ions

Two n4-type schiff base ligands named n,n'-bis(2-pyridylmethylidene)-1,2-diiminoethane (l1) and n,n'-bis(2-pyridylmethylidene)-1,3-diiminopropane (l2) have beensynthesized by the reaction of pyridine-2-carbaldehyde with ethylenediamine andpropylenediamine, respectively. the binding abilities of l1 and l2 in dichloromethane towardscu2+, cd2+, co2+, ni2+, zn2+ and pb2+ ions were evaluated by performing competitive extractionexperiments on the mixtures containing theses ions from aqueous picrate and nitrate media asa function of the aqueous phase ph. the results show a pronounced selectivity of the ligands towardscopper and cadmium ions among the tested metal ions. it is shown that the copper/cadmiumselectivity of the ligands is profoundly influenced by the nature of anions accompanyingthe extracted complexes. in fact, the ligands are more efficient complexing agent for cadmium ionsin the presence of nitrate and acetate anions, whereas this selectivity changes towards copper ionsin the presence of picrate, perchlorate and thiocyanat ions.