Solvent effect on complexation reactions

The inclusion complexation of aromatic amines with cucurbit6]uril (CB6]) capped with alkali metal cations was studied spectrophotometrically. We showed that CB6] capped with alkali metal cations forms a 1:1 inclusion complex with the aromatic amine guests (neutral organic molecules), independent of the length of guest molecules. The effects of salts on the inclusion constants of CB6] in the presence of different alkali salts were examined and it was found that the inclusion constants increased in the order of alkali cation Cs⁺ < Na⁺ < K⁺, suggesting the interaction of amine guests with the capped alkali metal cation. Further, the structures of the inclusion complexation of aromatic amines with CB6] were characterized by ¹H NMR measurements. Based on the results, the inclusion abilities of CB6] capped with alkali metal cations are discussed.