Chemistry Reference
In-Depth Information
Fig. 4.9
Comparison of the Gibbs reaction barriers and reaction energies (in kcal mol
−
1
) for the
DA reaction over [5, 6] and [6, 6] bonds of X@
I
h
-C
80
(X
Sc
3
N, Lu
3
N, Y
3
N, La
2
,Y
3
,Sc
3
C
2
,
Sc
4
C
2
,Sc
3
CH, Sc
3
NC, Sc
4
O
2
, and Sc
4
O
3
) EMFs. Only energies for the lowest energy orientations
of the metal cluster are considered. The
dotted
(
striped
)
lines
indicate the lowest and highest
(average) Gibbs reaction barriers and reaction energies for each case. (Adapted with permission
from (Garcia-Borràs et al.
2013c
). Copyright 2013 Wiley)
=
Classical Clusters (La
2
,Y
3
)
The charge transfer and HOMO- LUMO gaps are prac-
tically the same in the two considered cases as presented in Table
4.2
. Therefore,
the main factors that differentiate their reactivity are the volume of the cluster and
the fullerene deformation energy. A larger volume of the inner cluster (and so a
higher fullerene deformation energy) leads to an increase of the exohedral reactivity
of the classical EMF. As observed in the TNT cases, the preference for the [6, 6]
addition increases for those systems that have a larger cluster volume and fullerene
deformation energy, which is the case for Y
3
.
Metallic
Carbide
(Sc
3
C
2
,S
4
C
2
),
hydrocarbide
(Sc
3
CH),
and
carbonitride
(Sc
3
NC)
For these types of
I
h
-C
80
EMFs in general the reaction barriers decrease
