Supramolecular threaded complexes from fullerene-crown ether and π-extended TTF derivatives

A series of pi-extended TTFs (exTTFs) bearing one (8, 16,19) or two (14) dibenzylammonium units have been threaded through a dibenzo-24-crown-8 (DB24CS) ring covalently linked to a C-60 sphere. Whereas 8 and 14 were prepared in a multistep synthetic procedure involving Sonogashira cross-coupling reactions affording rigid donors, exTTFs 16 and 19 were prepared by direct esterification reactions leading to more flexible systems. Complexation experiments carried out by H-1 NMR titration and fluorescence studies show the formation of stable supramolecular dyads with binding constants ranging from 103 to 104 m(-1). Although the UV/Vis and CV studies reveal the lack of interaction between the electroactive species (C60 and exTTF) in the ground state, fluorescence data indicate the presence of an electronic interaction in the excited state.