Planar Chiral Metallopolymers for Electrochemically Mediated Enantioselective Separations

The molecular design of redox-responsive interactions can unlock new pathways for enantioselective separations. While chiral redox molecules are powerful platforms for molecular recognition, their implementation in enantioselective separations has remained elusive due to limitations in enantioselectivity and a lack of robust redox electrosorbents. Here, we design a redox-responsive polymer with planar chirality that can achieve exceptional enantioselectivity for the separation of biomolecules. Planar chirality is generated through the insertion of a substituent onto the cyclopentadienyl ring of an oxazoline-conjugated ferrocene with the stereochemical synthesis route guided by the point chirality at the oxazoline moiety. These planar chiral ferrocenes demonstrated significantly stronger enantioselective interactions than the equivalent ferrocenes with only point chirality. Electronic structure calculations revealed the key role of planar chirality, where the inserted functional groups can either coordinatively or antagonistically contribute to complexation, resulting in enhanced enantioselective interactions. Planar chiral metallopolymers were synthesized and evaluated for electrochemical enantioselective adsorption of N-Boc-proline, with over 99% enantiomeric excess achievable within seven theoretical stages in a multistage cascade. Planar chirality combined with redox electrochemistry offers a promising path for electrochemically mediated enantioselective separations.