Energy Transfer and Guest Responsive Fluorescence Spectra of Polyrotaxane Consisting of α-Cyclodextrins Bearing Naphthyl Moieties

We constructed a polyrotaxane (1) composed of about 15 α-cyclodextrins, each bearing roughly two naphthalene units and a polyethylene glycol (PEG) as a threading chain with adamantane groups at both ends. The product was characterized by 1H NMR, 13C NMR, and absorption spectroscopies. We observed that photoenergy transfer occurs from the naphthalene units of 1 to 5-dimethylamino-1-naphthalenesulfonyl (dansyl) of dansyl modified β-cyclodextrin (Dnsβ-CD) when Dnsβ-CD forms a complex with each terminal adamantane moiety of the polyrotaxane. This energy transfer was reduced by the addition of adamantanol, which acts as a competitive binder for Dnsβ-CD.