Fluorescent mono- and tetra-dansylated cavitands: synthesis and acid sensitivity

Two fluorescent tetra- and mono-dansylated resorcinarene cavitands were prepared and fully characterized. The X-ray structure of mono-dansylated resorcinarene cavitand was obtained. Their intrinsic absorption and fluorescence properties were studied. These properties were strongly sensitive to the presence of perchloric acid, as evidenced by the appearance of isobestic points upon protonation of the dansyl dimethylamino functions. The decreasing of the fluorescence emission intensity upon titration with perchloric acid was explained by the excited state interactions between the dansyl groups of the resorcinarene. Fluorescence quantum yields (Phi(F)) of mono- and tetra-dansylated cavitands and the reference compound were determined using dansyl chloride as reference in acetonitrile.