Ab initio helium NMR chemical shifts of endohedral fullerene compounds He@Cn (n = 32−180)

Helium NMR chemical shifts have been computed at the gauge including atomic orbitals (GIAO)-SCF/dz(C), tzp(He)//MNDO level for the endohedral fullerene compounds He@Cn (n = 32, 36, 50, 60, 70, 76, 78, 80, 82, 120, 180). The endohedral He shielding increases in the sequence C60 < C84 < C82 < C78 < C76 < C70, in accord with recent London calculations. For the smaller fullerenes (n < 60), large endohedral shieldings are computed, e.g. δ(He) = −30.3 ppm for He@C50 (D5h), while a nearly constant endohedral chemical shift of ≈ −17 ppm is predicted for the symmetric large fullerenes C120 and C180.