Spectral Narrowing of UV-Visible Absorption and Emission Spectra of Anthracene-Derivatives in β-Cyclodextrin Nanocavity: Effects of Host/Guest Stoichiometry

Cyclodextrins (CD) are cyclic oligosaccharides consisting of six or more D-glucopyranose units, the interior of which forms a hydrophobic cavity. In the present study, we employed the CD confinement effects as a tool to suppress an electronic decoherence of guest wavefunction by reducing intermolecular interactions between a guest molecule and the surrounding environment. Effects of host/guest stoichiometry on the decoherence suppresion were investigated by comparing native β-CD with trimethyl-β-CD that should form only a 1:1 complex. Both fluorecence and fluorecence-excitation spectra of inclusion complexes exhibited spectral narrowings only for the β-CD host, suggesting that the formation of barrel-type β-CD dimer plays a key role for the pronounced spectral narrowings.