13C NMR Pattern of Sc3N@C80. Structural Assignment of the First Fullerene With Adjacent Pentagons

Reveles et al. "13C NMR Pattern of Sc3N@C80. Structural Assignment of the First Fullerene With Adjacent Pentagons"
JPCA 109, 7068 (2005)


Using a combination of computation and experiment, these guys have determined that the C80 cage containing Sc3N@C80 hs adjacent pentagons. Now typically there is a 70-90 kJ/mol penalty for having fused pentagons, so it's not a particularly energetically feasible configuration. This is enshrined as the "Isolated Pentagon Rule", which serves as a way of screening out a lot of the unfeasible geometries wehn trying to determine the structure. Of course, when you start putting metals inside, all bets are off, as they can have substantial interactions with the cage.