Pyrenyl-functionalized ferrocenes for multisignaling recognition of anions

Abstract

New mono- and di-substituted pyrene-appended ferrocenes bearing amide or amide–sulfonamide binding sites, 1–4, have been synthesized, and their anion recognition abilities have been investigated. In CH₃CN solution, all receptors show distinctive electrochemical sensing of F⁻ and H₂PO₄⁻ with a large cathodic shift in the ferrocene/ferrocenium redox potential, with 4 showing the strongest anion binding ability. In addition, receptors 3 and 4 bearing amide–sulfonamide binding sites also exhibit fluorescence response to AcO⁻ and H₂PO₄⁻ with a large enhancement in their emission intensity. The binding mechanisms between 3 and anions are also investigated by ¹H NMR titration and DFT calculations.