Sodium-selective macrocyclic polyamine carriers having pyridine-functionalized sidearms

Abstract

A new type of sodium-selective carrier molecule was developed which was characterized by a pyridine-functionalized arm and a parent polyamine ring. Although the parent macrocyclic polyamines are well recognized as potential ligands of ‘soft’ heavy and transition metal cations, pyridinearmed triamine and tetraamine macrocycles show specific ionophoric activity for the ‘hard’ Na⁺ cation. ¹³C NMR binding experiments strongly supported the idea that these polyamine carriers completely encapsulated a Na⁺ cation via sidearm–macroring interaction. Their unique cationbinding properties offered selective and efficient membrane transport of the Na⁺ cation. Since their complexation and transport behaviour is largely different from that observed with conventional macrocycles, the present study provides a new possibility for the design of a macrocyclic polyamine carrier exhibiting a specific transport function.