Design and synthesis of ionophores with multiple receptor sites: solution nuclear magnetic resonance studies of their interaction with chloride, sodium and potassium ions

Abstract

Ionophores of the bis(crown ether) type, with polyamine linkers, examples of which are known to bind simultaneously to a cation and its counter anion, have been prepared. One-pot reductive amination, used to couple a benzo-crown aldehyde with aliphatic (both linear and cyclic) and aromatic polyamines, proved to be the most efficient route. A strong inhibition of one synthetic route (amine benzylation) was observed. The competitive interaction between chloride and other anions for binding with the protonated ionophores was examined using ³⁵Cl NMR spectroscopy. Sandwich complexing of potassium contrasting with single-face complexation of sodium was demonstrated by ¹³C NMR spectroscopy.