Chemistry Reference
In-Depth Information
Br
n
BuLi
+
2
Br
32
33
34
Chloranil
HO
OH
OsO
4
36
DMSO, CF
3
COOH
35
O
O
365 nm
PMMA, RT
37
7
Fig. 13 Photogeneration of heptacene 7 in a PMMA matrix from
α
-diketone 37 [
48
]
Fig. 14
Green color
of heptacene isolated in an argon matrix at 10 K. Reprinted with permission
from [
52
]. Copyright 2007 Royal Society of Chemistry
acene radical anion formation and allows assignment of the remaining electronic
transitions to radical cations. The longest wavelength absorption of the heptacene
radical cation is observed at 2,134 nm in solid argon [
22
,
52
].
An unexpected observation was made after the actual matrix isolation
experiments: during warm-up of the optical substrate from 10 K to room tempera-
ture, the green color of the heptacene molecule (see inset of Fig.
14
) disappeared
and a yellow material was obtained at room temperature [
22
]. This differed from
the behavior of pentacene and hexacene, which could be recovered from the optical
substrate as blue and green materials, respectively. With heptacene, however,
