The binding of fluorophores to beta-cyclodextrin derivatives

β-cyclodextrin (β-CD) is a seven-unit cyclic sugar molecule with a toroidal shape, a hydrophilic exterior and a hydrophobic cavity. It has been suggested that pyrene (P) forms a 2:1 (P(β-CD)2) complex with β-CD, where pyrene lies in-between the two wider rims of the β-CD. We examined this hypothesis by comparing the spectral properties of pyrene in the presence of substituted β-CDs. These properties include the shape and lifetime of pyrene fluorescence and the effect on pyrene fluorescence of added iodide quencher and alcohol. The derivatives studied included those with substituents only on the narrow rim, and those with substitution on both the narrow and wide rims. Our evidence indicates that a 2: 1 complex is f01meli when there is no substitution on the wider rim of the β-CD molecule. The complexing patterns of β-CDs with two other fluorophores have also been examined: 2-acetylnaphthalene (2-AN) and N-phenyl-2-naphthylamine (NP-2-NA). The analysis using 2-AN utilized only the methylated β-CDs, while the NP-2-NA analysis only examined the p-CD monomer