Fluorescence Characterization of the Cyclodextrin/Pyrene Complex Interaction with Chiral Alcohols and Diols

The chiral properties of cyclodextrins (CDs) facilitate the formation of diastereomeric complexes with a number of pesticides and pharmaceuticals which are also frequently composed of one or more chiral centers. The roles of chirality and structural volume in CD binding to a homologous series of linear, chiral alcohols and diols are evaluated by comparing the trend in the pyrene fluorescence I/III band ratio and the hydrophobicity for the CD/pyrene complex with CD/pyrene complexes incorporating achiral alcohols. Stronger hydrophobicity is observed for complexes capped by chiral alcohols relative to complexes formed with a similar achiral counterpart, suggesting the importance of the alcohol chiral center. Furthermore, the diols induce a more hydrophobic environment than their alcohol counterparts with the β-CD/pyrene complex, while the converse is the case for the γ-CD systems. The systems involving γ-CD were also compared by use of pyrene fluorescence lifetime measurements.