Ferrocenoyl-amino acids: redox response towards di- and trivalent metal ions

The interaction of six ferrocene-amino acid conjugates (Fc–CO–Gly–OH (2a), Fc–CO–Asp–OH (3a), Fc–CO–Glu–OH (4a), 1,1′-Fc(CO–Gly–OH) (2b), 1,1′-Fc(CO–Asp–OH) (3b), and 1,1′-Fc(CO–Glu–OH) (4b)) with Mg2+, Ca2+, Zn2+, La3+, and Tb3+ was investigated in aqueous solutions using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Addition of metal ions to solutions caused, in some cases, large changes in the half-wave potential, E1/2. Our electrochemical results show that the Gly systems, 2a and 2b, show a preference for binding Mg2+, whereas the Asp and Glu conjugates prefer binding Ln3+.