COMPLEX FORMATION BETWEEN SOME DI- AND TERVALENT HEAVY METAL CATIONS AND DIAZA CROWN ETHERS AND CRYPTANDS IN AQUEOUS SOLUTION

Abstract

The complexation of some di- and tervalent heavy metal cations in aqueous solution with diaza crown ethers and cryptands has been studied using pH-metric titrations. The macrobicyclic cryptands form more stable complexes with these cations compared with diaza crown ethers. The size of the cavity also influences the stability of the complexes formed. In contrast to EDTA only ion-dipole and covalent interactions between the ligands and the cations take place. Thus, it is not surprising that the complex stabilities of the diaza crown ethers and the cryptands with heavy metal cations are smaller than the stabilities of the cation EDTA complexes.

Key Words:

• Cryptands
• diaza crown ethers
• complexes
• stability constants
• heavy metals