Synthesis, conformational and host-guest properties of water-soluble pillar[5]arene

Water-soluble pillar[5]arene was synthesized by the introduction of carboxylate anions at both upper and lower rims. When cationic viologen salt was mixed with the water-soluble pillar[5]-arene in aqueous media, a very stable 1 : 1 host-guest complex was formed.