Groundwork for a rational synthesis of C60:: Cyclodehydrogenation of a C60H30 polyarene

A C60H30 polycyctic aromatic hydrocarbon (PAH) that incorporates all 60 carbon atoms and 75 of the 90 carbon-carbon bonds required to form the fullerene C-60 has been synthesized in nine steps by conventional laboratory methods. Laser irradiation of this C60H30 PAH at 337 nanometers induces hydrogen loss and the formation of C-60, as detected by mass spectrometry. A specifically labeled [C-13(3)] C60H30 retains all three C-13 atoms during the cage formation process. A structurally related C48H24 PAH that lacks the three peripheral benzene rings cannot be transformed into C-60, whereas the next higher homolog, a C80H40 PAH, degrades to the C60H30 PAH, which then loses hydrogen to give [60]fullerene. These control experiments verify that the C-60 is formed by a molecular transformation directly from the C60H30 PAH and not by fragmentation and recombination in the gas phase.