INFLUENCE OF FLUORINATED ALCOHOLS ON CYCLODEXTRIN - PYRENE COMPLEXATION

An investigation of the effect of fluorinated alcohols on complexation between pyrene and beta- and gamma-cyclodextrin (CD) in aqueous solution is reported. Using fluorescence spectrophotometric analysis, pyrene I/III vibronic band ratios were monitored upon the addition of CD, both in the absence and presence of fluorinated alcohols, as well as in the presence of their nonfluorinated alcohol analogs. The fluorinated alcohols studied were 2,2,2-trifluoroethanol and 2,2,3,3,3-pentafluoro-1-propanol. In aqueous solution, the alcohols were found to have no effect on the pyreneI/III ratio in the absence of CD, but a strong effect when CD was present. For beta-CD, the stoichiometry of the CD/pyrene complex was found to be predominantly 2 : 1, whereas for gamma-CD it was 1 : 1. Apparent complexation equilibrium constants for the CD/pyrene complexes in the absence and presence of the alcohols were calculated by use of nonlinear regression analysis. Interactions between the alcohols and CDs were also investigated using H-1 and F-19 techniques.