Zusammenfassung
The Computed [GIAO (Gauge Including Atomic Orbitals)-SCF/tzp(He),dz(C,H)//SCF/3-21G] endohedral helium NMR chemical shifts for various He@C60H36 isomers (in parentheses) are −10.8 (T), −7.4 (D3d'), −6.1 (S6), −3.4 (Th), and −5.6 ppm (D3d). Despite 12 unusually long
CC bonds (1.646 Å at SCF/3-21G), the T form has the lowest energy of all isomers studied and is more stable than Th by 59 kcal/mol (SCF/3-21G level). The computed δ(3He) values depend primarily on the numbers of benzene rings present. It is suggested that the 3He labeling and NMR technique, assisted by the computational results presented, could provide new information concerning the nature of the products arising from Birch reduction and hydrogenation reactions of C60.
