Tweezer Type Cationic C-H Hydrogen Bond Donor Host Monomer Assisted Synthesis of an Imprinted Receptor with High Affinity and Selectivity for Sulfonated Target Molecules

We report the design and synthesis of high affinity and selective sulfonate-binding imprinted polymers using tweezer type functional monomers featuring parallel two imidazolium sites and phenyl sulfonic acid (PSA). The complexation in the pre-polymerization complex and stoichiometry of the bis-imidazolium functional monomer with PSA was evaluated by UV, 1H NMR titration supported by modeling. The combination of hydrophobic phosphorus hexafluoride counter anion to the imidazolium functional moieties and the lipophilic template phenyl sulfonic acid in tetrabutylammonium salt form in acetonitrile have produced extremely tight recognition binding sites combined with ionic and C-H hydrogen bond donors within imprinted polymers. Results from rebinding isotherm assays found that polymers displayed remarkable affinity to PSA with Ka = 104 to 105 M-1 in organic as well as aqueous solvents. The binding pocket of the developed receptor showed unprecedented selectivity for PSA when imprinted polymers competed with equimolar quantities of isosteric analytes, i.e., phenyl sulfonic acid and phenyl phosphonic acid.