Anion recognition by acyclic redox-responsive amide-linked cobaltocenium receptors

Abstract

New acyclic tripodal mono- and 1,1′-bis-substituted amide-linked cobaltocenium ligands have been prepared. Proton NMR spectroscopic and cyclic voltammetric anion co-ordination investigations reveal that the combination of a positively charged cobaltocenium unit together with an amide N–H group are the essential components for the molecular and electrochemical recognition of anionic guest species. Correlations were found to exist between Hammett σ_p values of electron-donating and -withdrawing substituents of monosubstituted aryl amide cobaltocenium derivatives and relative magnitudes of halide-anion induced perturbations of the amide proton NMR chemical shift and cathodic shift of the respective cobaltocenium–cobaltocene reduction redox couple.