Heterocyclic Quinol‐Type Fluorophores: Solid‐State Fluorescence Change in Crystals of Benzo[b]naphtho[1,2‐d]furan‐6‐one‐Type Fluorophore upon Inclusion of Organic Solvent Molecules

The crystals of benzo[b]naphtho[1,2‐d]furan‐6‐one‐type fluorophores (1) exhibit sensitive colour and fluorescence change upon enclathration of organic solvent molecules. The crystal of fluorophore 1b (R = Bu) exhibits fluorescence decrease upon inclusion of cyclohexane; however, the crystal of fluorophore 1c (R = Ph) exhibits a drastic fluorescence enhancement upon inclusion of chloroform. To elucidate the enclathrated guest effects on the photophysical properties of the crystals, the X‐ray crystal structures of the guest‐free and guest‐inclusion compounds were determined. On the basis of the spectroscopic data and the crystal structures, the effects of the enclathrated guest on the solid‐state photophysical properties of the clathrate compounds are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)