Chemistry Reference
In-Depth Information
Table 1 The inversion barrier (kcal/mol) and the bowl depth (
) of some highly substituted
Å
corannulenes
a
Compound
G
{
inv
R
ʔ
Bowl depth
References
41
3,5-C
6
(CH
3
)
2
H
3
-
0.88
[
39
]
44
Ph
-
0.85
[
39
]
8.7
b
0.85
b
45
Me
[
62
]
0.72, 0.68
b
t
-Bu
45
4.5
[
68
]
45
CF
3
-
0.79
[
69
]
48
SPh
-
0.94
Siegel et al.,
unpublished results
49
3,5-C
6
(CH
3
)
2
H
3
-
0.94
[
39
]
50
Manisyl
12.1
0.94
[
70
]
0.49
b
, 0.51
c
52
Cl
-
[
71
,
72
]
2.2
b
0.58
b
54
Me
[
62
]
55
C
C-
n
-Bu
-
0.60
[
73
]
57
4-C
6
H
4
Cl
2.5
0.25
[
74
]
8.28
b
0.49 [
75
]
a
Based on experimental data and X-ray structure if not otherwise mentioned
b
Calculated value
c
The structure was determined by gas-phase electron diffraction
58a
SPh
Corannulene (1) displays interesting electrochemical properties. The reduction
states of 1 lie between those of the neutral hydrocarbon and the tetraanion
(1
4-
/4Li
+
). Reduction of 1 at
78
C with excess lithium metal in [D
8
]-THF over
a period of several days led to a series of three color changes, first to green, then to
purple, and finally to brownish-red [
76
]. Quenching this solution with water gave
tetrahydrocorannulene as the major product accompanied by small amounts of
dihydrocorannulene and 1. More recently, the structure of [Na(DME)
3
]
+
[1
] was
analyzed by X-ray crystallography, and its bowl depth (0.85
) was found to be
Å
slightly shallower than the parent 1 [
77
].
The first and second reduction potentials and the first oxidation potential of
corannulene measured by CV (cyclic voltammetry) strongly depend on measured
conditions, such as temperature, solvent, and electrolytes [
34
,
68
,
78
]. The third
reduction potential was observed when the experiment was conducted with a
suitable combination of solvent and electrolyte at low temperature (below 213 K)
[
68
]. The reduction potentials of corannulene and their comparisons with other
functionalized derivatives are presented in Table
3
(cf. Sect.
2.2.2
).
The electrochemical properties of 1 allow it to give rise to electrochemilumi-
nescence [
69
]. When a solution of 1 is treated with coreactants, such as benzoyl
peroxide or arylamine, an intense blue light is generated. In addition, simple
corannulene derivative 1,2-bis(trifluoromethyl)corannulene (23c) can potentially
be applied as a electrically conductive material. The electron-accepting ability
of trifluoromethyl groups cause 23c to have charge-carrier mobility displays as
>
0.9 cm
2
V
1
s
1
[
41
].
