Thermodynamic rearrangement synthesis and NMR structures of C1, C3, and T isomers of C60H36

The structures of three C60H36 isomers, produced by high-temperature transfer hydrogenation of C(60) in a 9,10-dihydroanthracene melt, was accomplished by 2D (1)H-detected NMR experiments, recorded at 800 MHz. The unsymmetrical C(1) isomer is found to be the most abundant one (60-70%), followed by the C(3) isomer (25-30%) and the least abundant T isomer (2-5%). All three isomers are closely related in structure and have three vicinal hydrogens located on each of the 12 pentagons. Facile hydrogen migration on the fullerene surface during annealing at elevated temperatures is believed to be responsible for the preferential formation of these thermodynamically most stable C60H36 isomers. This hypothesis was further supported by thermal conversion of C60H36 isomers to a single C(3v) isomer of C60H18.