Formation of redox-active, two-component films by electrochemical reduction of C60 and transition metal complexes

Electrochemical reduction of C-60 in 4:1 toluene/acetonitrile solution in the presence of (PhCN)(2)PdCl2, Ir(CO)(2)Cl(p-toluidine), or (CF3Co2)(4)Rh-2 produces three different, redox-active, black films that coat the electrode. These films are insoluble in common organic solvents and adhere strongly to the electrode surface. Film formation has been monitored by multiscan cyclic voltammetry, which gives information about the requirements for film growth. The three different films (on the original electrodes) can be transferred to a solution of acetonitrile that contains only the supporting electrolyte, tetra(n-butyl)ammonium perchlorate, where the films retain their redox activity. Each film displays a significant decrease in resistivity (i.e. a window of conductivity) in the potential region in which it is grown and in which it displays redox activity. The films have been examined by scanning electron microscopy, which shows variations in the nature of the three films' morphologies with the film formed from (PhCN)(2)PdCl2 displaying the greatest uniformity and smoothest surface. Analysis of the films by infrared spectroscopy and laser desorption mass spectrometry reveals that intact C-60 units are present within each film. Treatment of the palladium/C-60 film with triphenylphosphine results in film dissolution and the formation of the previously characterized complex, (eta(2)-C-60)Pd(PPh3)(2) The rhodium/C-60 film dissolves in pyridine and F-19{H-1} NMR spectroscopy reveals that (CF3CO2)(4)Rh-2 is extracted intact from the film. The structure of the films is discussed in terms of covalent bonding between the fullerenes and the metal atoms or complexes within the film.