MOLECULAR RECOGNITION BY POLYMER-SUPPORTED REAGENTS DEFINED THROUGH LINEAR FREE-ENERGY RELATIONSHIP STUDIES

The degree of molecular recognition displayed by polymer-supported phosphinic acid, sulfonic acid, and tertiary amine ligands in the complexation of neutral phenols, anilines, and benzoic acids has been defined through Hammett-type correlations. The total amount complexed is an additive function of an active-site interaction plus a solvent interaction. No solvent effect is observed when the solute/solvent solubility parameters are comparable. The intensity of the active-site interaction between the polymer ligand and the molecular functional group is determined by varying the electron density at the active site through substituents on the aromatic ring. The phosphinic resin absorbs moderate levels of the anilines (25%-75%), with electron-donating substituents increasing the percent absorbed. The sulfonic resin strongly absorbs the anilines (95%-97%) regardless of the substituent. The tertiary amine resin absorbs 50%-75% of the benzoic acids, with electron-withdrawing substituents increasing the level of absorption. Moderate interaction energies thus permit targeted molecule-polymer recognition as the active-site electron density is varied. © 1990, American Chemical Society. All rights reserved.