Cucurbituril and beta-cyclodextrin as hosts for the complexation of organic dyes

The complexation of neutral organic molecules by cucurbituril and beta-cyclodextrin in formic acid was studied by means of spectrophotometric titrations. In the case of beta-cyclodextrin the composition of the solvent has almost no influence upon the stability of the complexes formed. This situation is completely different for cucurbituril. Due to its interactions with protons the measured stability constants of the complexes formed with organic molecules increase with decreasing acid concentration. At low acid concentrations cucurbituril forms more stable complexes with organic molecules than beta-cyclodextrin.