Carboxylated pillar[n]arene (n = 5-7) host molecules: high affinity and selective binding in water

Water-soluble carboxylated pillar[n]arenes (n = 5-7) or WPns were discovered to be high affinity host molecules with selective binding for different guests based on a systematic investigation. We chose 22 dyes or guests and determined the value of K_a for 51 supramolecular complexes. It was discovered that the electrostatic interactions, π-π stacking and hydrophobic effect were the driving force for high affinity supramolecular encapsulation. WPns had selective binding toward suitable guests based on their sizes and molecular structures. Based on the above discovery, a guest (guest 21) was designed, which bound with WP7 3.3-fold tighter compared to methyl viologen.