Transition metal cation and phosphate anion electrochemical recognition in water by new polyaza ferrocene macrocyclic ligands

New polyaza ferrocene macrocyclic ligands 4-7 have been synthesised and with 4, copper(II) and nickel(II) transition metal complexes isolated. Electrochemical investigations reveal these redox-active ligands can electrochemically sense various transition metal cations in polar organic solvents and in water at high pH values with ligands 4 and 5. Aqueous electrochemical competition experiments with Ni2+, Cu2+, and Zn2+ suggest 4 and 5 exhibit a selectivity preference for the copper(II) cation. At lower pH values (6-8) the respective protonated polyammonium forms of 4, 5 and 7 complex and electrochemically detect the biologically important phosphate anions, ATP and hydrogen phosphate in the aqueous environment.