Host–guest association of coumarin 343 with β-cyclodextrin and C-hexylpyrogallol[4]arene: opposite fluorescent behavior and prototropic characteristics

Abstract

We report here the stoichiometry and the binding strength of coumarin 343 (C343) with β-cyclodextrin (β-CD) and with C-hexylpyrogallol[4]arene (C-HPA) using absorption, steady state fluorescence, time-resolved fluorescence and 2D ROESY NMR spectroscopic techniques. The effect of pH on C343 in water and in the presence of β-CD or C-HPA is studied. The ground state and the excited state pKa values for the neutral-monocation equilibrium of C343 are reported. The opposite fluorescence behavior of C343 in the presence of β-CD and in C-HPA is discussed.