Complex formation of cucurbit[6]uril with amines in the presence of different salts

The complex formation of cucurbit6]uril with cyclohexylmethylamine hydrochloride and hexylamine hydrochloride has been studied in aqueous solution using potentiometric titrations. The influence of salts like NaCl, KCl, RbCl, CsCl, BaCl₂ and tetramethylammonium chloride and tetraethylammonium perchlorate on the complex formation with amines has been studied at different concentrations of these salts. With increasing salt concentration the stability constants for the complex formation with cyclohexylamine hydrochloride and hexylamine hydrochloride decreases. However, no specific influence is observable. These results show that 2:1 complexes between these salts and cucurbituril are not formed or that their concentration in solution is rather low.