Redox-gated recognition of dihydrogen phosphate using a ferrocene-tethered non-symmetric aryl-triazole pentad

Anions play many roles in our environment. Consequently, the development of synthetic receptors capable of targeted anion binding is of ongoing importance. While many such receptors are known, simplified designs and measurement approaches are always beneficial. Herein, we report the synthesis of a non-symmetric aryl-triazole pentad receptor appended with a single ferrocene, its electrochemistry, and the selective binding to dihydrogen phosphate (H2PO4-) anions of its oxidised form over various environmentally prevalent anions (HSO4-, Cl-, NO3-). The receptor was constructed using a modular architecture with simple installation of a ferrocene unit using click chemistry. Electrochemical analysis on the receptor revealed that addition of H2PO4- anion led to a shift in the redox peaks of the receptor (FcP) towards more negative potentials, indicating higher anion affinity was achieved after the ferrocene was oxidised to its cationic form (FcP(+)). This work verifies prior studies on the efficacy of cationic charge in simpler receptor design for the creation of functional host-guest systems.