Chemistry Reference
In-Depth Information
Chapter 4
Understanding the Exohedral Functionalization
of Endohedral Metallofullerenes
Marc Garcia-Borràs, Sílvia Osuna, Josep M. Luis, Marcel Swart
and Miquel Solà
Abstract
The endohedral metallofullerenes (EMFs) and their exohedral functional-
ized derivatives present an increasing attention due to their potential applications in
materials science and medicine. However, the current understanding of the reactivity
of endohedral metallofullerenes is still very incomplete. In this chapter, we present
a thorough study of the Diels-Alder (DA) reactivity of
D
3h
-C
78
,Sc
3
N@
D
3h
-C
78
,
Y
3
N@
D
3h
-C
78
,Ti
2
C
2
@
D
3h
-C
78
,
Sc
3
N@
D
5h
-C
80
,Lu
3
N@
D
5h
-C
80
,Gd
3
N@
D
5h
-
C
80
„Sc
3
N@
I
h
-C
80
,Lu
3
N@
I
h
-C
80
-C
80
,Gd
3
N@
I
h
-C
80
,Y
3
N@
I
h
-C
80
,La
2
@
I
h
-
C
80
,Y
3
@
I
h
-C
80
,Sc
3
C
2
@
I
h
-C
80
,Sc
4
C
2
@
I
h
-C
80
,Sc
3
CH@
I
h
-C
80
,Sc
3
NC@
I
h
-
C
80
,Sc
4
O
2
@
I
h
-C
80
,Sc
4
O
3
@
I
h
-C
80
, and La@
C
2v
-C
82.
We have studied both the
thermodynamic and the kinetic regioselectivity, taking into account when it was re-
quired the free rotation of the metallic cluster inside the fullerene. This systematic
investigation was possible only because we use the Frozen Cage Model, which is a
low-cost approach to determine the EMF exohedral regioselectivity. Our study has
allowed the correction of two wrong experimental assignations of DA adducts, high-
lighting the key role of computational studies to achieve a deep understanding of
exohedral reactivity of the EMFs. The incarceration of the metallic cluster reduces
the reactivity of the EMFs respect to the hollow fullerenes. Our results also show that
bond distances, pyramidalization angles, LUMOs shape, charge transfer, and cluster
volume are the key factors that determine the DA regioselectivity of the fullerenes
and EMFs. However, none of them can be used alone to predict which bond will
