NEW PHENOL-CONTAINING BIS(AZACROWN ETHER)S - SYNTHESIS AND COMPLEXING PROPERTIES

A simple synthesis of phenol-containing bis(azacrown ether)s by the treatment of N-methoxymethyl-substituted azacrowns with phenols has been elaborated. Temperature conditions have been found for selectively introducing into one phenolic ring both one and two monoazacrown ether substituents. New symmetric 14a-e and asymmetric 15 phenol-bridged bis(azacrown ether)s exhibited strong complexation abilities towards both alkali and especially alkaline-earth metal cations. All measurements have been carried out using the pH-metric titration technique. Complexation constant values in neutral (K-1) and in alkaline (K-2) media are in the order: monocyclic 1b-d < bicyclic ligands 14a-c. In all cases, K-2 > K-1. These results show participation of phenolic ions in the complex formation process. In an alkaline medium, bis(azacrown ether)s 14b, 14e and 14d showed high selectivity towards Li+, Ba+2 and Sr+2, respectively.