Groundwork for a Rational Synthesis of C 60 : Cyclodehydrogenation of a C 60 H 30 Polyarene

Abstract

A C 60 H 30 polycyclic 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 C 60 H 30 PAH at 337 nanometers induces hydrogen loss and the formation of C 60 , as detected by mass spectrometry. A specifically labeled [ 13 C 3 ]C 60 H 30 retains all three 13 C atoms during the cage formation process. A structurally related C 48 H 24 PAH that lacks the three peripheral benzene rings cannot be transformed into C 60 , whereas the next higher homolog, a C 80 H 40 PAH, degrades to the C 60 H 30 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 C 60 H 30 PAH and not by fragmentation and recombination in the gas phase.