Fullerenium Salts: A New Class of C60-Based Compounds

摘要

Abstract: We report here on the preparation and characterization of a fullerenium salt in the solid state,nwhere the fullerene is in the 2 oxidized state. To succeed in this long-standing challenge, we exploit thenoxidizing power of one of the strongest Lewis acids, AsF5. The weak nucleophilic character of its conjugatenbase is essential in stabilizing the fullerene dication in a crystal lattice. High-resolution structural analysisnof this compound, with the formula C60(AsF6)2, indicates that the highly reactive C60n2 units are arrangednaccording to a novel 1D “zigzag” polymer structure. The molecules are connected by an alternating sequencenof four-membered carbon rings ([2 2] cycloaddition) and single C C bonds. The long awaited high-Tcnsuperconductivity and magnetism, expected in a hole-doped C60 compound, are replaced instead by ansemiconducting behavior, quite probably originating from the reduced crystal and molecular symmetry uponnpolymerization. The small value of the energy gap (approximately 70 meV) suggests, nevertheless, thenproximity of a metallic phase.