ABSTRACT
Since the discovery of C60 Buckminsterfullerene1 in 1985 and its isolation and unequivocal characterization2,3 in 1990, almost all fullerene research has focused on the stable species Cn (n = 60 and ≥70), all of which conform to the Pentagon Isolation Rule (PIR).4,5 The PIR maintains that the stability of C60, C70, and higher fullerenes is due to the fact that these fullerenes possess structures with nonabutting pentagons, whereas fullerenes with n < 70 (except for n = 60) must possess abutting pentagons. This rule applies only to the underivatized fullerenes and the addition of moieties that disrupt the sp2 hybridization can stabilize structures with abutting pentagons.
