Fluorescent Molecular Sensing System Based on Tri-Pyrenes-Labeled γ-Cyclodextrin at the Hetero Rim

Fluorescent active host labeled at the upper and lower rims of γ-cyclodextrin, namely, mono-3 A -deoxy-3 A -pyrenebutylamido-6X,Y-O-bis-pyrenebutylate-mono-altro-γ-cyclodextrin (γ-3) has been synthesized as a chemosensor for steroidal guests using fluorescence spectra change upon a guest addition. The γ-3 shows monomer and excimer fluorescence, which results in an increase of the intensity of monomer and decrease of excimer fluorescence with a host–guest binding in the cyclodextrin cavity. The extent of monomer and excimer fluorescence variations of γ-3 was used as an indication for the sensing ability for the guests examined. The guest-induced fluorescence changes were measured for 10−7 M solutions of γ-3. The sensing parameters (ΔI ex /I0ex and ΔI mon /I0mono) were used to describe the sensing ability of γ-3. The values of ΔIex/I0ex describe that γ-3 shows less selectivity for guests than that of mono-3 A -deoxy-3 A -pyrenebutylamido-6 X -O-mono-pyrenebutylate-mono-altro-γ-cyclodextrin (γ-2), and the values of Δ Imon/I0mono show that γ-3 shows higher sensitivity and selectivity than that of γ-2.