The reaction of fullerene C(60) with phthalazine: the mechanochemical solid-state reaction yielding a new C(60) 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.