The Reaction of Fullerene C60 with Phthalazine:: The Mechanochemical Solid-State Reaction Yielding a New C60 Dimer versus the Liquid-Phase Reaction Affording an Open-Cage Fullerene

The reaction of fullerene C-60 with phthalazine was studied both in solution and in the solid state using the high-speed vibration-milling technique. The reaction in solution gave open-cage fullerene derivative 1 in 44% yield by a one-pot reaction. In contrast, the solid-state reaction afforded dimeric derivative 2 as the sole product. Dimeric derivative 2 was found to undergo intramolecular [2 + 2] cycloaddtion between the two C-60 cages located in close proximity to give a new C-60 dimer 6 in quantitative yield. The structures of these new derivatives of C-60 were determined by spectroscopic methods, and the electrochemical behavior of 2 and 6 was also studied.