Electrochemical and structural studies on microcrystals of the (C60)x(CTV) inclusion complexes (x = 1, 1.5; CTV = cyclotriveratrylene)

The electrochemical reduction of microcrystals of (C-60)(x)(CTV) (x = 1, 1.5; CTV = cyclotriveratrylene) complexes adhered to electrode surfaces in contact with CH3CN (0. 10 mol L-1 Bu4NClO4) results in initial formation of (C-60(-))(x)(CTV) which is followed by the liberation of the reduced fullerene anion from the CTV cavity. The released fullerene anion then reacts with the Bu4N+ electrolyte cation to form surface-confined (Bu4N)C-60 species which can in turn be further reduced to solid-state and/or solution-phase multi-charged fullerene anions or oxidized to C-60(solid). The expelled CTV diffuses from the surface of the electrode into the bulk solution to form (Bu4N+)(CTV) species. The peak potential for one-electron reduction of solid (C-60)(x)(-) (CTV) is positively shifted by about 50 mV (x = 1) or 80 mV (x = 1.5) relative to the value for pure C60 microcrystals. These and results with other supramolecular complexes available in the literature suggest that the contact area between host and guest molecules as well as the position of high electron density area of the host are important factors that stabilize the host--guest complexes during/after the addition of electrons to the fullerene. The improved crystal structure determination of (C-60)(CTV)(toluene)(0.5) using X-ray diffraction data at 173 K shows a two-dimensional close packed array of fullerenes with a third of these devoid of CTV.