Chemistry Reference
In-Depth Information
Fig. 7 Triangular [4]
phenylene dyad 44 [
62
]
O
O
O
O
O
2
N
NO
2
44
SO
2
Cl
S
1) Br
2
,FeBr
3
,DCE,
2) SnCl
2
,HCl,AcOH,
3) RBr, NaOH, EtOH
42%
S
S
NaI, CuI, Cu, L
dioxane,
45%
Br
Br
46
PPA
PhCH
3
,
76%
SO
2
Cl
S
45
S
S
R=
L=
NH
HN
47
Scheme 13 Synthesis of thioether-substituted biphenylene 47 [
63
]
Fig. 8 Thioether-substituted
fluorenes 48 and 49 [
63
]
Et
Et
S
S
S
S
48
49
Table 6 Conductance and
first oxidation potential of
PAHs 47-49 [
63
]
10
3
)
1/2
(V vs Ag/Ag
+
)
Compound
Conductance (G
0
47
3.6
0.2
0.509
48
3.5
0.3
0.633
4.4
0.3
48
0.627
48 and 49 (Fig.
8
)[
63
]. The essential biphenylene-forming reaction was achieved by
Ullman coupling of the 2,2-dibromobiaryl 45. Acidic cyclization of 46 is completely
regioselective at the
position would
involve a carbocation cation intermediate with greater cyclobutadiene character.
The conductances of compounds 47-49 were measured using a scanning tunnel
microscope (STM) based break-junction technique. Results from the conductance
and first oxidation potentials are summarized in Table
6
. Surprisingly, although
biphenylene 47 is more easily oxidized than the fluorene analogues, decreasing
oxidation potential did not seem to correlate with increasing conductivity. These
b
position to give 47, as cyclization at the
a
