Halide anion recognition by new acyclic quaternary polybipyridinium and polypyridinium receptors

Abstract

New acyclic quaternary polybipyridinium receptors containing 5,5′- and 4,4′-disubstituted N,N′-dimethyl-2,2′-bipyridinium moieties (L¹–L⁶) and a polypyridinium receptor L⁷ have been synthesised. ¹H NMR titration studies in deuteriated DMSO show these receptors complex chloride and bromide anions, with a 1:1 stoichiometric ligand: chloride stability constant evaluations suggesting the amide containing polypyridinium receptor (L⁷) forms the most thermodynamically stable chloride anion complex. Square-wave voltammetric investigations showed some of the polypyridinium receptors to recognise electrochemically the chloride anion.