Chemistry Reference
In-Depth Information
Table 4.2
Metallic cluster volumes, charge transferred to the fullerene cage, EMFs HOMO- LUMO
gaps, and fullerene deformation energies in X@
I
h
-C
80
species
X
V
a
Charge
b
HOMO- LUMO
c
E
def
.
Sc
3
N
453.1
1.279
2.294
6.9
Lu
3
N
473.1
1.425
2.516
20.5
Y
3
N
496.4
1.362
2.540
20.1
Y
3
491.4
1.570
1.236
e
13.9
La
2
369.5
1.542
1.287
5.5
Sc
3
CH
471.3
1.253
2.520
8.5
Sc
3
NC
473.9
1.189
2.294
14.9
2.264
e
16.3
Sc
4
C
2
571.2 1.044 2.021 13.8
Sc
4
O
2
550.3 1.196 1.709 8.5
Sc
4
O
3
562.1 1.126 2.294 9.4
a
Volume measured by the GEPOL93(Pascual-Ahuir et al.
1994
) procedure. Values given in Å
3
b
Charge transferred from the metal cluster to the
I
h
-C
80
cage measured as the sum of Hirshfeld
charges of all fullerene C atoms obtained at B3LYP-dDsC/TZP//BP86-D
2
/DZP. Values given in
atomic units
c
HOMO- LUMO gap of EMFs at B3LYP-dDsC/TZP//BP86-D
2
/DZP level. Values given in eV
d
Fullerene deformation energy due to the presence of the inner metallic cluster, calculated as the
energy difference between
I
h
-C
80
distorted geometry (the EMF cage) and the
I
h
-C
80
optimized one
at B3LYP-dDsC/TZP//BP86-D2/DZP level. Values given in kcal mol
−
1
e
For open-shell species, the HOMO-LUMO gap was calculated as the difference between the
lowest
Sc
3
C
2
484.1
1.100
α
non-occupied spinorbital and the highest
α
occupied spinorbital
when the charge transferred to the cage decreases and the volume of the metallic clus-
ter increases (see Table
4.2
). This implies that also for these EMFs larger fullerene
deformation energies decrease reaction barriers. The only exception for the latter
observation is the Sc
4
C
2
@
I
h
-C
80
EMF. Also for this type of EMFs the [6, 6] addi-
tion is preferred from a kinetic point of view for the EMF that has the larger metallic
cluster encapsulated (i.e. Sc
4
C
2
), while [5, 6] addition is the one preferred for the
other cases. But under thermodynamic control, the most favored addition is the one
corresponding to the [5, 6] position for all the present studied cases.
Metallic Oxide (Sc
4
O
2
,Sc
4
O
3
)
The spherical shape of the metallic oxide clusters
makes this class of EMFs significantly different from the rest of the considered cases.
The [5, 6] addition is preferred in all cases, especially for Sc
4
O
3
@
I
h
-C
80
, from both
thermodynamic and kinetic points of view. Moreover, by increasing the cluster size
the reaction becomes more regioselective, and the EMF more reactive (lower reaction
barriers and more negative reaction energies).
As a whole, our results show that the reactivity of EMFs is lower than the empty
I
h
-C
80
fullerene. The exothermicity of the reactions in EMFs tends to decrease
when the charge transfer to the cage increases because the cage has less electron
