Chemistry Reference
In-Depth Information
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(
P
)-(12,8)-[4]CC
Molar ratio: 22%
Isolated yield: 19%
Hex
(
M
)-(12,8)-[4]CC
Molar ratio: 22%
Isolated yield: 19%
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(
P
)-(11,9)-[4]CC
Molar ratio: 19%
Isolated yield: 15%
Hex
(
M
)-(11,9)-[4]CC
Molar ratio: 19%
Isolated yield: 14%
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(10,10)-[4]CC
AABB
Molar ratio: 13%
Isolated yield: 11%
(10,10)-[4]CC
ABAB
Molar ratio: 5%
Isolated yield: 4%
Fig. 40 Isomers of [4]CC [
44
]
crystallized for X-ray diffraction studies. Nakamura found that this molecule had
remarkable bond consistency. While fullerene exhibits bond length alternation, the
20
-electrons in the
cis
-annulene equator appeared to be fully delocalized with
bond lengths of 1.40 and 1.43
˚
. The outer double bonds are much shorter,
conforming more to a Kekul
´
structure than a graphitic model and may be
explained by the geometric constraint of the fullerene skeleton. NCIS calculations
also confirmed the aromaticity of this novel structure [
68
]. For the first time, this
synthesis validated the idea that discrete, double-stranded aromatic belts can be
systematically constructed with organic synthesis. These modified fullerene
structures were found to be fluorescent with a quantum yield of
π
ϕ ¼
0.18 and a