A missing link in the transformation from asymmetric to symmetric metallofullerene cages implies a top-down fullerene formation mechanism.
Although fullerenes were discovered nearly three decades ago, the mechanism of their formation remains a mystery. Many versions of the classic 'bottom-up' formation mechanism have been advanced, starting with C2 units that build up to form chains and rings of carbon atoms and ultimately form those well-known isolated fullerenes (for example, I(h)-C60). In recent years, evidence from laboratory and interstellar observations has emerged to suggest a 'top-down' mechanism, whereby small isolated fullerenes are formed via shrinkage of giant fullerenes generated from graphene sheets. Here, we present molecular structural evidence for this top-down mechanism based on metal carbide metallofullerenes M2C2@C1(51383)-C84 (M = Y, Gd). We propose that the unique asymmetric C1(51383)-C84 cage with destabilizing fused pentagons is a preserved 'missing link' in the top-down mechanism, and in well-established rearrangement steps can form many well-known, high-symmetry fullerene structures that account for the majority of solvent-extractable metallofullerenes.
1] Virginia Tech Carilion Research Institute, Roanoke, Virginia 24016, USA [2] Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
Jianyuan
J
Zhang
Faye L
FL
Bowles
Daniel W
DW
Bearden
W Keith
WK
Ray
Tim
T
Fuhrer
Youqing
Y
Ye
Caitlyn
C
Dixon
Kim
K
Harich
Richard F
RF
Helm
Marilyn M
MM
Olmstead
Alan L
AL
Balch
Harry C
HC
Dorn
D018360:Crystallography, X-Ray; D037741:Fullerenes / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D012997:Solvents / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry*
D037741:Fullerenes; D012997:Solvents; D015019:Yttrium; D005682:Gadolinium