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

New monor and 1,1'-bis-amide-linked 2,2'-bipyridine substituted ferrocenyl ligands, L-2 and L-1, have been prepared. Voltammetric and H-1-NMR investigations of anion binding have been performed. The neutral bis-amide ligand L-1 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 L-2 and of the carboxyester-containing ligands L-3 and L-4 highlights the benefit of multidentate binding and the importance of hydrogen bonding to amide protons in H2PO4- complexation to L-1. 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. (C) 1999 Elsevier Science S.A. All rights reserved.