Modulation of the metal recognition properties of a new type of azaferrocenophane-based chemosensors: co-ordination chemistry towards Mg2+, Ca2+, Zn2+ and Ni2+

Abstract

The structure–redox chemistry relationship of a new type of azaferrocenophane-based chemosensors, 3 and 4, in the presence of protons and several kinds of metal ions, has been studied. Electrochemical studies, carried out in CH₂Cl₂, in the presence of increasing amounts of Mg²⁺, Ca²⁺, Zn²⁺ and Ni²⁺ showed that the wave corresponding to the Fc/Fc⁺ couple of the uncomplexed ligands is gradually replaced by a new reversible wave at more positive potentials corresponding to the Fc/Fc⁺ couple of the complexed ligands. The maximum shift of the ferrocene oxidation wave was found for 4b in the presence of Mg²⁺, whereas for 3f a selective sensing response for Mg²⁺ in the presence of hydrated Ca²⁺ cations was observed, with a concomitant highly visual output response consisting of a deep purple colour.