Host–guest interaction of flavanone and 7-aminoflavone with C-Hexylpyrogallol[4]arene

In this paper, we report the structures of the host–guest complexes of flavanone and 7-aminoflavone (guests) with C-Hexylpyrogallol[4]arene (host). The study of the host–guest binding is carried out using UV–Visible absorption, steady-state and time-resolved fluorescence, and 2D ROESY spectroscopy. The stoichiometry and the binding constant of the C-Hexylpyrogallol[4]arene–guest complexes are reported based on absorption and fluorescence titrations. Both flavanone and 7-aminoflavone form 1:1 complexes with the host with binding constant values of 1.71 × 104 mol−1 dm3 and 2.06 × 104 mol−1 dm3 respectively. Fluorescence quenching of the two flavonoids on complex formation occurs and the Stern–Volmer constants are reported. The mode of binding of flavanone and 7-aminoflavone with the host molecule is optimized with 2D ROESY and the structures of the inclusion complexes are proposed.