Electrochemical response to anions by neutral ferrocenyl receptors containing 2,2′-bipyridyl arms

Abstract

Abstract New mono- and 1,1′-bis-amide-linked 2,2′-bipyridine substituted ferrocenyl ligands, L2 and L1, have been prepared. Voltammetric and 1H-NMR investigations of anion binding have been performed. The neutral bis-amide ligand L1 forms a complex with the dihydrogenphosphate anion, and electrochemical recognition of H2PO4− is observed in organic electrolytes. Comparison with the behavior of the mono-amide ligand L2 and of the carboxyester-containing ligands L3 and L4 highlights the benefit of multidentate binding and the importance of hydrogen bonding to amide protons in H2PO4− complexation to L1. The voltammetric behavior of the different ligands in the presence of F−, Cl− and HSO4− can be interpreted mainly in terms of ion pairing with the oxidized, cationic forms of the ligands. In addition, catalytic oxidation of Cl− and oxidative degradation of the ferrocenyl ligands, leading to the formation of [FeIIIClx]3−x species, are observed in the presence of chloride anions.