50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
Cs@Cn
48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
K@Cn
Rb@Cn
Group I Group I MetallofullerenesDonate 1 electron to cage M+@C2n
− Distribution similar to empty cages C60 and C70 dominant
n = 60
n = 70
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Ca@Cn
Ba@Cn
44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84
Sr@Cn
Group II metals• Donate 2 electron to cage M2+@C2n
2−
• M@C50 exhibits dominance as well as M@C60 M@C70 no longer dominant
n = 50 60
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Sc@Cn
Y@Cn
Group III metals• Donate 3 electron to cage• M3+@C2n
3−
• Now, M@C44 dominates • M@C50 is also abundant.• M@C60 no longer dominates
n = 44
n = 50
n = 60
Clear correlation to charge transfer and growth
• More charge transferred, the distribution of fullerenes shifts to very small metallofullerenes
• Thus, when more charge is transferred they “grow slower”. As the number of transferred electrons are increased, the growth distribution is shifts to smaller fullerenes.
• This can explain why the larger metallofullerenes appear to only form as a small fraction of, for example, empty cage C60. Under conditions where empty cage C60 dominates of C2n distribution, the M@C2n distributions exhibits mostly small fullerenes…….which will likely “react away” in the solid state, in solution, or air.
• Charge transfer appears to be extremely important in determining metallofullerenes formation. It is likely the most important growth factor
C84
+ carbon vapor
C84
1,1751,1701,165
m/z1,6001,5001,4001,3001,2001,1001,000900
1165 1170 1175
Gd@C82 Gd@C82 calculated
Gd@C84
Metallofullerenes “grow slower” than empty cages in carbon vapor?
+ carbon vapor
C84
m/z20001900180017001600150014001300120011001000900800700600
Compare Gd@C80 to C84
from our Nature Communications paper
50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
Cs@C2n
48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
Rb@C2n
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Ca@C2n
44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Ba@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70
Sc@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Y@C2n
Cs@C60
Cs@C70
Ca@C50
48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90
K@C2n
K@C60
K@C70
Rb@C70
Rb@C60
Ba@C50
Ca@C60
Sc@C44Ca@C70
Ba@C70
Ba@C60
44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84
Sr@C2n
Sr@C60
Sr@C50
Sr@C70
Sc@C50
Sc@C60
Y@C50Y@C44
Y@C50
Group I metals• Donate 1 electron to cage• M+@C2n
−
• Distribution similar to empty cages (ie, C60 and C70 dominate)
Group II metals• Donate 2 electron to cage• M2+@C2n
2−
• M@C50 exhibit much greater abundance, although M@C60 just a bit more dominate. M@C70 forms in lower abundance
Group III metals• Donate 3 electron to cage• M3+@C2n
3−
• Now, M@C44 dominates over other endo cages. M@C50 is also highly abundant.
• M@C60 no longer dominates
Comparison of Group I, II, III metallofullerene growth distributions
m/z20001900180017001600150014001300120011001000900800700600
Metallofullerenes “grow slower” than empty cages in carbon vapor?
La2@C80
+ carbon vapor
m/z
1,8001,7001,6001,5001,4001,3001,2001,1001,000
La2@C82
La2@C80
C84
+ carbon vapor
C84
Compare growth of La2@C80 to C84
from our Nature Communications paper
C84
+ carbon vapor
C84
1,1751,1701,165
m/z1,6001,5001,4001,3001,2001,1001,000900
1165 1170 1175
Gd@C82 Gd@C82 calculated
Gd@C84
Metallofullerenes “grow slower” than empty cages in carbon vapor?
+ carbon vapor
C84
m/z20001900180017001600150014001300120011001000900800700600
Compare Gd@C80 to C84
from our Nature Communications paper
Does more charge transfer from metal to cage render metallofullerenes less reactive?
• That could explain striking difference in growth of metallofullerenes vs empty cages
• Thus, as one moves from Group I to Group III metals, M@C2n should become less reactive due to more transfer to cage. Thus, Group III would exhibit a greater distribution of smaller fullerenres than Group II, and Group I
• A good test of this is to look at the Lanthanides• It is known there are two groups of lanthanides, those that
transfer 3 electrons to cage M3+@C2n
3-
La, Ce, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Lu
• And those that only transfer 2 electrons to cage M2+@C2n
2-
Sm, Eu, Tm, Yb
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
La@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Ce@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Pr@C2n
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Sm@C2n
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Eu@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Tb@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Dy@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Ho@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Er@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Nd@C2n
44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82
Yb@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Lu@C2n
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Gd@C2n
Comparison of Lanthanides
La@C44
La@C50
La@C60
Tb@C44 Tb@C50
Tb@C60
Sm@C44
Sm@C50
Sm@C70
Sm@C60
M3+@M@C2n3− Lanthanides
M2+@M@C2n2− Lanthanides
• Striking difference for Sm, Eu, Tm, Yb
These are M2+@M@C2n2−
M@C60 > M@C50 >M@C70
M@C44 is weak
Matches Group II metal M@C2n distributions (for example, Sr@C2n below), which can, of course, only donate 2 electrons
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
La@C2n
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Sm@C2n
Comparison of Lanthanides
La@C44La@C50
La@C60
Sm@C44
Sm@C50
Sm@C70
Sm@C60
M3+@M@C2n3− Lanthanides
M2+@M@C2n2− Lanthanides
• La, Ce, Nd, Gd, Tb, Dy, Ho, Er, Lu all exhibit the same distributions
M@C44 > M@C50 >M@C60
M@C60 relatively weak for these M3+@M@C2n
3− Lanthanides
Matches the growth distributions of the Group III metals….for example, Y@C2n below
44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84
Sr@C2n
Sr@C60
Sr@C50
Sr@C70
36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80
Y@C2nY@C50Y@C44
Y@C50
Clear correlation to charge transfer and growth
• More charge transferred, the distribution of fullerenes shifts to very small metallofullerenes
• Thus, when more charge is transferred they “grow slower”. As the number of transferred electrons are increased, the growth distribution is shifts to smaller fullerenes.
• This can explain why the larger metallofullerenes appear to only form as a small fraction of, for example, empty cage C60. Under conditions where empty cage C60 dominates of C2n distribution, the M@C2n distributions exhibits mostly small fullerenes…….which will likely “react away” in the solid state, in solution, or air.
• Charge transfer appears to be extremely important in determining metallofullerenes formation. It is likely the most important growth factor