4
to be effective in this regard. Chao, Miller, and Kuo
5
6
2b in 71% and 67% yields, respectively. In general, IBX
1
does not cleave vicinal 1,2-diols, although strained and
0
have predicted that cyanated pentacenes should be quite
amenable for use as n-type organic semiconductors because
of their deep LUMO and narrower HOMO-LUMO gap
sterically restricted syn 1,2-diols 1a and 1b were oxidized to
1
1
give dialdehydes 2a and 2b via C-C bond cleavages. 2a
and 2b are useful intermediates for various chemical
modifications such as oxidations, reductions, and conden-
sations. The reaction of 2a with NH OH HCl in pyridine
(
E ). However the derivatization of pentacene is quite
g
difficult due to its insolubility in common organic solvents
7
and only a few types of cyanated acenes have been prepared.
Even the simplest 6,13-dicyanopentacene and 5,12-dicya-
nonaphthacene have not been achieved due to their syn-
thetic difficulties.
2
3
gave 5,12-dihydroxyiminomethylnaphthacene 3a in 99%
yield, which was then treated with Ac O or MsCl to afford
2
DC-NAP in 80% yield. In a similar manner, DC-PEN was
obtained in 33% overall yield from 1b.
In this paper, we present the novel synthesis, properties,
and OFET performances of 5,12-dicyanonaphthacene
(
DC-NAP) and 6,13-dicyanopentacene (DC-PEN). In
the DC-NAP and DC-PEN structures, the most reactive
peri-positions are effectively cyanated. To the best of our
knowledge this is the first report on the synthesis of
symmetrically cyanated pentacene.
Figure 1. (a) ORTEP drawing of DC-NAP and (b) crystal
˚
˚
structure of DC-NAP. a = 3.79021(12) A, b = 12.8608(4) A,
˚
c = 13.5027(4) A, R = 94.054(2)ꢀ, β = 92.358(2)ꢀ, γ =
9
1.872(2)ꢀ, Z = 2.
Single crystals of DC-NAP (Figure 1) were obtained as
Scheme 1. Synthesis of DC-NAP and DC-PEN
red needles from slow diffusion of chlorobenzene into a
solution of DC-NAP in chloroform. The structure of DC-
NAP is planar as was observed for naphthacene. The CN
group is slightly bent in plane relative to the peripheral
phenyl group, but not to the naphthyl group: angles of CN
groups to the phenyl ring are 119.4(2)ꢀ and 117.5(2)ꢀ and the
angles of C-C-N are 178.5(3)ꢀ and 178.2(3)ꢀ, respectively.
In sharp contrast to naphthacene, which forms a herring-
1
2
bone structure, the crystal structure of DC-NAP is a face-
to-face slipped π-stacking structure with an intermolecular
˚
distance of 3.472 A. 5-Cyanonaphthacene is known to
adopt a herringbone structure but 5,11-dicyanonaphtha-
cene has been reported to adopt the face-to-face slipped π-
stacking structure, which is similar to our result.
7a
The absorption and fluorescence spectra of dicyano
acenes in chloroform are shown in Figure 2 and in Table
S1 in the Supporting Information. The absorbance max-
ima of DC-NAP and DC-PEN are significantly red-shifted
by 65 and 74 nm relative to parent naphthacene and
The synthesis of DC-NAP and DC-PEN is shown in
Scheme 1. Diols 1a and 1b were easily prepared in gram
8
scale quantities following literature procedures. Pre-
viously, Murdock et al. reported the conversion of 1a to
2
9
a using Pb(OAc) with AcOH in 20% yield. However,
4
13
pentacene. This is due to the efficient π-conjugation of
this reaction was not applicable to the conversion of 1b to
b. Thus, we used o-iodoxybenzoic acid (IBX) mediated
oxidative cleavage reactions of 1a and 1b, which afforded
,12-diformylnaphthacene 2a and 6,13-diformylpentacene
2
(8) Yamada, H.; Yamashita, Y.; Kikuchi, M.; Watanabe, H.; Oku-
jima, T.; Uno, H.; Ogawa, T.; Ohara, K.; Ono, N. Chem.;Eur. J. 2005,
5
1
1, 6212–6220.
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P. F.; Lee, V. J.; Izzo, P. T.; Lang, S. A.; Angier, R. B. J. Med. Chem.
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(
4) Kuo, M. Y.; Chen, H. Y.; Chao, I. Chem.;Eur. J. 2007, 13, 4750–
758.
5) Kaur, I.; Jia, W.; Kopreski, R. P.; Selvarasah, S.; Dokmeci,
4
(
M. R.; Pramanik, C.; McGruer, N. E.; Miller, G. P. J. Am. Chem.
Soc. 2008, 130, 16274–16286.
(
6) Liu, C. C.; Mao, S. W.; Kuo, M. Y. J. Phys. Chem. C 2010, 114,
2316–22321.
7) (a) Li, A.; Wen, S. H.; Song, J. L.; Deng, W. Q. Org. Electron. 2009,
0, 1054–1059. (b) Swartz, C. R.; Parkin, S. R.; Bullock, J. E.; Anthony,
2007, 5, 767–771.
2
(12) Robertson, J. M.; Sinclair, V. C.; Trotter, J. Acta Crystallogr.
1961, 14, 697–704.
(13) Because of the low solubility in chloroform, the absorption
(
1
J. E.; Mayer, A. C.; Malliaras, G. G. Org. Lett. 2005, 7, 3163–3166.
spectrum of pentacene was measured in chlorobenzene.
Org. Lett., Vol. 13, No. 6, 2011
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