Fluorescence and Circular Dichroism Studies on Host-Guest Complexation of γ-Cyclodextrin Bearing Two 2-Naphthyl Moieties

Article abstract of DOI:10.1246/bcsj.59.465

Host-guest complexation of γ-cyclodextrin bearing two 2-naphthyl moieties (1) has been studied by circular dichroism and fluorescence spectroscopic methods.The exciton coupling band observed in the naphthalene ¹L_a transition region shows that the two naphthyl moieties of 1 take a chiral orientation in the cavity.The guest binding of 1 changes the circular dichroism pattern, finally affording a negative band, but hardly influences the fluorescence pattern in which excimer emission is predominant.These phenomena suggest that a guest molecule is included in the cavity of 1 by extruding two naphthyl moieties from the cavity so as to make the moieties to act as hydrophobic caps.Dimethyl sulfoxide (DMSO) was found to be effective to change both fluorescence and circular dichroism patterns, increasing monomer-like emission and converting the exciton coupling pattern to a simple negative band.These results suggest that the two naphthyl moieties are not in proximal positions in DMSO-rich solutions.