INCLUSION BY CYCLODEXTRINS TO CONTROL DYE AGGREGATION EQUILIBRIA IN AQUEOUS-SOLUTION

Oxazine 1 perchlorate (A) and oxazine 170 perchlorate (D) were selected to investigate the influence of cyclodextrins (CDs) on the dyes' aqueous solution aggregation equilibria. Through equilibrium processes, these days form inclusion complexes with β- and γ-CD. The amphiphile hexane sulfonate can be coincluded with D in γ-CD. We report determination of the stoichiometries of all inclusion complexes and measurement of all equilibrium constants; temperature effect data on some of the latter are also included. This study clearly demonstrates that proper size matching between the guest and the host's cavity leads to substantially larger equilibrium constants. All experimental measurements for each dye rely on changes in absorption intensities of the individual long wavelength monomer and dimer absorption bands. Because H-dimers are formed, the dimer absorption bands are blue-shifted relative to the monomer bands and only the monomers fluoresce. Although, in the absence of CDs, A is mostly monomer and D is mostly dimer or larger aggregate, the intercession of CDs can be used to force A to mostly dimer and D to mostly monomer. © 1990, American Chemical Society. All rights reserved.