Abstract
A series of ionophores based on diaza 18-crown-6 units possessing amide and sulfonamide functions were prepared. Their complexing properties were investigated in solvent polymeric membrane electrodes. The influence of the structure of ligands, prepared on the selectivity of complexation, was examined with special respect to lead ions. Substantial changes were observed, when methyl substituent in benzene rings was replaced with hydrogen, bromomethyl or nitro group. All results were rationalized on basis of steric and electronic effects. The synthesis and complexation studies of supramolecular compounds is of continuous interest [1]. Several types of ionophores were designed for medicine, biochemistry and environmental pollution monitoring [2]. For pollution monitoring some of ionophores, selective towards heavy metal cations, are of general interest. Previously, we have shown that macrocyclic polyether diamides can be readily prepared [3] and successfully applied in ion-selective electrodes [4], showing high selectivity towards Pb 2+ over other divalent cations. This result prompted us to the conclusion that the introduction of external amide function into the macrocyclic ring can increase the stability of electrodes and improve the complexing properties of ionophores towards divalent cations. This paper deals with the preparation of a series of external macrocyclic diamides derived from diaza-18-crown-6. Complexing properties of prepared compounds were investigated in ion-selective polymeric membranes system with a special respect to lead cation.
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