Facile Dimerization and Circular Dichroism Characteristics of 6-O-(2-Sulfonato-6-naphthyl)-β-cyclodextrin

A monofunctional derivative of β-cyclodextrin (β-CD) containing a 2-sulfonato-6-naphthyl group at the primary face (1:  β-CD-NS) was prepared. The concentration dependences of fluorescence, circular dichroism (c.d.), and NMR spectra of 1 have been investigated and compared with the spectral changes associated with complexation of 6-methoxy-2-naphthalenesulfonate (MNSS) with β-CD. When the concentration of 1 was increased, the following were observed:  the enhancement of the concentration-normalized fluorescence intensity; an increase in molar ellipticities of the negative band around 280 nm; a more pronounced exciton coupling band around 230 nm in c.d. spectra; and an upfield shift of NMR signals from aromatic protons. The concentration dependent fluorescent intensity and molar ellipticity data fitted well to the monomer−dimer equilibrium of 1 with the dimerization constant of 9700 ± 2500 M-1. The dimerization constant is much larger than the association constants of MNSS with β-CD (510 ± 40 M-1) and 1 wi...