The determination of complex stabilities between different cyclodextrins and dibenzo-18-crown-6, cucurbit[6]uril, decamethylcucurbit[5]uril, cucurbit[5]uril, p-tert-butylcalix[4]arene and p-tert-butylcalix[6]arene in aqueous solutions using a spectrophoto

The solubility of dibenzo-18-crown-6, cucurbit[6]uril, decamethylcucurbit[5]uril, cucurbit[5]uril, p-tert-butylcalix[4]arene and p-tert-butylcalix[6]arene in aqueous solution increases in the presence of α-, β- and γ-cyclodextrin due to complex formation. The stability constants of the complexes formed are determined from UV-spectrophotometric measurements. Even without the knowledge of the molar absorptivities and of the solubilities of the guest molecules, the calculation of the stability constants is possible. The cavity size of the cyclodextrins used has only a minor influence upon the stability constants of the complexes formed in solution. The different guest molecules do not fit completely into the cavities of the cyclodextrin molecules. Obviously, supramolecular hosts like, e.g. dibenzo-18-crown-6 or calixarenes form complexes with cyclodextrins.