The bulk synthesis of the [2 + 2] dimer of fullerene C 60 was achieved by the solid-state mechanochemical reaction of C 60 with KCN by the use of a high-speed vibration milling (HSVM) technique. This reaction took place also by the use of potassium salts such as K 2 CO 3 and CH 3 -CO 2 K, metals such as Li, Na, K, Mg, Al, and Zn, and organic bases such as 4-(dimethylamino)-and 4-aminopyridine. Under optimum conditions, the reaction afforded only the dimer C 120 and unchanged C 60 in a ratio of about 3:7 (by weight) regardless of the reagent used. The dimer C 120 was fully characterized by IR, UV-vis, 13 C NMR, and TOF MS spectroscopies, cyclic voltammetry, and differential scanning calorimetry. Comparison of the IR and 13 C NMR spectral data of C 120 with those reported for all-carbon C 60 polymers implied that the [2 + 2] dimer C 120 represents the essential subunit of these polymers. The dimer C 120 underwent facile dissociation into two C 60 molecules by heat, HSVM treatment, exposure to room light, or electrochemical reduction. The dimer C 120 encapsulating 3 He in one of the C 60 cages was synthesized and was used to confirm the scrambling of a C 60 cage between the monomer and the dimer during the HSVM reaction. A possible mechanism for the selective formation of the dimer C 120 is proposed.

No abstract