The new open chain and macrocyclic hosts for oxoanions are synthesized by supplementing additional binding secondary carboxyamido functional groups to the parent bicyclic guanidinium anchor group. The complexation with different oxoanions as seen by the isothermal calorimetric analysis showed very high affinity towards various oxoanions in acetonitrile and DMSO. The chiral macrocyclic guanidinium host displayed enantiomeric discrimination for the aspartate and tartrate dianions. The dissection of the free energy of association ∆G into its enthalpy and entropy components was necessary to understand supramolecular binding principles in solution. As a corollary, it lays the foundation for the rational design in artificial receptors for oxoanions.
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