Complexation and electrochemical sensing of anions by amide-substituted ferrocenyl ligands

New amide-containing ferrocenyl ligands, L1-5 were prepared and the voltammetric and H-1 NMR investigations of anion binding were carried out in organic media. The electrochemical recognition ability of L1-5 towards F-, HSO4-, H2PO4- and ATP(2-) is based on the synergy between H-bonding to amide protons in anion complexation to reduced, neutral ligands and ion-pairing interactions developed with the oxidized, cationic form of the ligands. The strength of the anion-ligand interactions depends on the number of ferrocene centers and amide groups in the receptor, and on the accessibility of the binding sites. Clear two-wave cyclic voltammetry features allowed the amperometric titration of H2PO4- and ATP(2-) by ligands L-4 and L-5 built from a cyclotriveratrylene structural unit, and containing a combination of three ferrocene centers with three (L-4) or six (L-5) amide groups. (C) 2001 Elsevier Science B.V. All rights reserved.