Binding of chloride anion to a tetrathiafulvalene calix[4]pyrrole (TTF-C4P) donor results in ET to Li+@C-60 to produce the radical pair (TTF-C4P(center dot+)/Li+C60 center dot-), the structure of which was characterized by X-ray crystallographic analysis. The addition of tetraethylammonium cation, which binds more effectively than Li+C60 center dot- as a guest within the TTF-C4P cavity, leads to electron back-transfer, restoring the initial oxidation states of the donor and acceptor pair.