Theoretical evidence for the major isomers of fullerene C-84 based on C-13NMR chemical shifts

Geometry optimizations for three isomers of fullerene C-84, 21, 22 and 23, have been performed by density functional theory (DFT) at the B3LYP/6-31G* level of theory. C-13 NMR chemical shifts were evaluated by the GIAO method employing 6-31G* and 6-311G** basis sets. Isomers 22 and 23 are predicted to have essentially equal energies and isomer 21 to be 16 kcal mol(-1) less stable. The calculated C-13 NMR chemical shifts of isomers 22 and 23 agree nicely with experimental data while the results of isomer 21 show large di fferences, indicating that isomer 22 is the experimentally observed D-2 iso mer.