Organic pollutants in water-soluble cavitands and capsules: contortions of molecules in nanospace

We report on the binding properties of deep cavitands for various industrial pollutants in water. Depending on the guest type, monomeric cavitands, dimeric capsules or both acted as receptors and formed complexes. The complexation studies revealed unique binding modes of long n -alkyl chain alcohols and n -alkylbenzenes. In cavitands, the hydroxy group of alcohols was found to be anchored at the polar rim while the rest of the chain undergoes fast coiling and folding. In capsules, regioselective bending of the polar end was observed. Accommodation of n -alkylbenzenes in capsules proceeded through folding of the alkyl chain over the aromatic ring. Water-miscible pollutants tetrahydropyran and 1,4-dioxane were also complexed by cavitands in aqueous media. The reported findings suggest the future use of water soluble cavitands in industrial waste treatment.