Chiral Metallopolymers for Redox-Mediated Enantioselective Interactions

Synthetic chiral platforms can be a powerful platform for enantioselective interactions, especially when coupled with redox-mediated electrochemical processes. While metallopolymers are versatile platforms for molecularly selective binding, their application for chiral applications is limited. In particular, the recognition and separation of biologically relevant chiral molecules can be key for biomanufacturing and diagnostics. Here, the design of chiral redox-polymers enables electrochemically-controlled enantioselective interactions, and supramolecular chirality is leveraged for enhancing recognition towards target enantiomers. Chiral redox-metallopolymers are synthesized based on Ugi's amine-inspired chiral monomers, and their enantioselective recognition toward ionic enantiomers such as tryptophan and naproxen is demonstrated, with higher enanhcement provided by the chiral redox-polymer over the single-site, chiral building bloack itelf. 2D nuclear magnetic resonance spectroscopy and solid-state circular dichroism support the emergence of supramolecular chirality resulting from the intramolecular interaction between the ferrocene and the alkyl group in the backbone. The half potential shift of the redox-polymers behaves linearly from 0% to 100%ee l-tryptophan to enable enantiomer quantification. Investigation on solvent polarity and pH effect reveal that the enantioselective mechanism is attributed to the subtle balance between hydrogen bonding and pi-pi interaction. This study highlights the potential of chiral redox-metallopolymers as platforms for electrochemically-modulated enantioselective interactions towards a range of amino acids and pharmaceutical carboxylates.