High-resolution C-13 NMR studies of high-pressure-polymerized C-60: Evidence for the [2+2] cycloaddition structure in the rhombohedral two-dimensional C-60 polymer

We report on C-13 NMR measurements of a rhombohedral two-dimensional polymer of C-60 obtained under high pressure. By spinning the sample up to 12 kHz, we were able to identify six resonances at 149.1, 147.9, 145.2, 139.6, 134.8, and 73.5 ppm. The static distortion of the C-60 molecules induced by the transformation under pressure must be at the origin of the observed inequivalent carbons in the polymer. The C-13 NMR line shape simulation of the obtained spectrum is compatible with the suggested polymeric structures where the C-60 molecules are connected by [2 + 2] cycloadditions.