Structure, Stability, and NMR Properties of Lower Fullerenes C₃₈−C₅₀ and Azafullerene C₄₄N₆

A systematic survey of the complete set of isomers of fullerenes C38, C40, C42, C44, C46, C48, C50 and azafullerene C44N6 is reported. All isomeric structures were optimized using first-principle density functional theory at the B3LYP/6-31G* level. The isomeric structures with the lowest energies are C38:17, C40:38, C42:45, C44:75, C44:89, C46:109, C48:171, and C50:270. The ground-state structure of the azafullerene C44N6 in the framework of C50:270 has D3 symmetry. The 13C NMR chemical shifts and nucleus-independent chemical shifts (NICS) for the stable isomers of each fullerene are presented.