Synthesis and characterization of 2,8-diazaperylene-1,3,7,9-tetraone, a new anthracene diimide containing six-membered imide rings

Article abstract of DOI:10.1021/ol200659c

A successful synthesis of novel diimides, namely anthracene diimide containing six-membered imide rings, with potential application in organic electronics is reported. The single crystal of 5a exhibits a close interplanar spacing of 3.45 A between molecul

Full text of DOI:10.1021/ol200659c

ORGANIC
LETTERS
2011
Vol. 13, No. 10
2560–2563
Synthesis and Characterization of
2,8-Diazaperylene-1,3,7,9-tetraone,
a New Anthracene Diimide Containing
Six-Membered Imide Rings
Ali Reza Mohebbi, Cedric Munoz, and Fred Wudl*
Department of Chemistry and Biochemistry and Center for Polymers and
Organic Solids, University of California, Santa Barbara, California 93106,
United States
wudl@chem.ucsb.edu
Received March 11, 2011
ABSTRACT
A successful synthesis of novel diimides, namely anthracene diimide containing six-membered imide rings, with potential application in organic
˚
electronics is reported. The single crystal of 5a exhibits a close interplanar spacing of 3.45 A between molecules in a stack.
Aromatic polyimides are among the strongest polymeric
engineering materials,1 a prime example being Kapton.
The majority of the aromatic polyimides are five-mem-
bered ring cyclic imides based on pyromellitic dianhydride
(structure 1).1 Six-membered ring polyimides based on
naphthalene and perylene are considerably more rare.
Surprisingly, according to SciFinder, polyimides based
on structure 5 are unknown.
Organic semiconductors have been of great research
interest for use in low cost, ultrathin, and flexible products
such as flexible transistors, displays, and photovoltaics.2ꢀ5
While many p-channel organic semiconductors have been
thoroughly characterized and have achieved acceptable
device performance and stability, n-channel organic
semiconductors are less numerous.6 There are several
examples that are being explored for the latter, such as
copper hexadecafluorophthalocyanine (F16CuPc),7 C60
and its derivatives,8 chemically modified oligothiophenes,9
perfluoropentacene (F14C22),10 and rylene diimides.11,13
Recently, rylenes and related aromatic cores, particularly
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2003, 15, 33. (c) Facchetti, A.; Deng, Y.; Wang, A. C.; Koide, Y.;
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r
10.1021/ol200659c
Published on Web 04/19/2011
2011 American Chemical Society

particularly in comparing 4 with 5. This is easiest seen
when comparing the structures upon the addition of an
electron and the subsequent stabilization of the radical
anion, as shown in Figure 2.
Figure 1. Chemical structure of some diimide molecules.
benzene, naphthalene, perylene, and linear anthracene
diimide small molecules (Figure 1) have received attention
for their high electron affinities, high electron mobility,
excellent thermal and oxidative stability, and finally, ro-
ꢀ
12
bustness vis-a-vis environmental stresses. They are,
therefore, promising candidates for a variety of organic
electronic applications.
Figure 2. Rational for the design of 5. In 4 the radical anion
cannot be stabilized without disturbing the aromatic sextets
(400).
Compared to work on naphthalene and perylene
(rylene) diimides,13 there have been very few reports on
benzene and anthracene diimides.14 Devices based on the
latter, bearing the same N-substituents, exhibit mobilities
an order of magnitude lower than the naphthalene and
perylene analogues.11d This result is probably related to
their structural difference, possibly five- vs six-membered
imide rings (Figure 1).
Herein, we report the synthesis of a new monomer for
polyimides as well as an electron-deficient semiconductor
based on the previously unknown anthracene-1,9:5,10-
tetracarboxylic diimide containing six-membered imide
rings 5aꢀd. We also report ab initio molecular orbital
calculations of electron distribution in anthracene diimides
of 4 and 5.
Figure 2 shows that even though in both cases one gains
an aromatic sextet upon addition of an electron to 4 and 5,
providing a driving force for this process. However,
whereas in 5 the spin and charge find themselves adjacent
to a carbonyl for further stabilization by delocalization
(50), in 4 two aromatic sextets need to be sacrificed for the
equivalent stabilization (400). This concept was verified by
electrochemical results (vide infra). In fact, 5 is a slightly
stronger acceptor than 3and a much stronger acceptor than 4.
Scheme 1 outlines the synthetic route for compound 5.
The synthesis started with acid chloride formation, fol-
lowed by intramolecular FriedelꢀCrafts cyclization reac-
tion of 9,10-bis(carboxymethyl)anthracene 6 to produce 7
The design of molecules 5 was based on a relatively
simple valence bond view of the anthracene nucleus,
Scheme 1. Synthesis of Anthracene Diimides 5aꢀc. a
(11) (a) Katz, H. E.; Lovinger, A. J.; Johnson, J.; Kloc, C.; Siegrist,
T.; Li, W.; Lin, Y. Y.; Dodabalapur, A. Nature 2000, 404, 478. (b)
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Phys. 2004, 95, 6396. (c) Jones, B. A.; Ahrens, M. J.; Yoon, M.;
Facchetti, A.; Marks, T. J.; Wasielewski, M. R. Angew. Chem., Int.
Ed. 2004, 43, 6363. (d) Zhan, X.; Facchetti, A.; Barlow, S.; Marks, T. J.;
Ratner, M. A.; Wasielewski, M. R.; Marder, S. R Adv. Mater. 2011, 23,
268.
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Chem. Mater. 2007, 19, 2703. (b) Katz, H. E.; Johnson, J.; Lovinger,
A. J.; Li, W. J. Am. Chem. Soc. 2000, 122, 7787. (c) Chen, H. Z.; Ling,
M. M.; Mo, X.; Shi, M. M.; Wang, M.; Bao, Z. Chem. Mater. 2007, 19,
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€
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a Reagents and conditions: (a) (i) SOCl2, 80 °C, (ii) AlCl3,
ClCH2CH2Cl; (b) PBr5, chlorobenzene; (c) DMSO, 100 °C; (d) Oxone,
acetic acid; (e) n-alkylamine, 80 °C.
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Org. Lett., Vol. 13, No. 10, 2011
2561

in an overall yield of 70%.15 Without any purification,
compound 7 was brominated to obtain 8. A suitable single
crystal of 8 was obtained by slow evaporation from solution
in dichloromethane (Supporting Information, Figure 5-1).
A solvolytic reaction of 8 in DMSO resulted in bis-
aceanthrylene-1,2-dione 9,16 which was subsequently oxi-
dized to the carboxylic acid anhydride 10 by Oxone.17
Anhydride 10 is highly fluorescent in solution (Supporting
Information, Section.3).
Anhydride 10 can be used as a starting material for the
general preparation of 5 by condensation with primary
amines. The heptyl, octyl, and cyclohexyl drivatives 5bꢀd
were prepared from 10 and pure amines. The butyl derivative
5a was obtained from 10 and the corresponding amine in the
presence of toluene as solvent.17 The structures and
1
purities of 5aꢀd were verified by HNMR, 13C NMR,
and high-resolution mass spectroscopy (Supporting
Information, section 2).
Figure 4. Fluorescence spectra of compounds 3 (red) and 5b
(black) in CH2Cl2 as solvent.
shift of 45 and 50 nm, respectively. Compound 5b exhibits
a fluorescence quantum yield of 71% in solution.
The electronic properties of the new anthracene dicarbox-
yimides 5aꢀcwere examined by cyclic voltametry (Figure 5).
The electrochemical reduction potential of the first wave in
chlorobenzene vs SCE is ꢀ0.22 V for anthracene diimide 5b,
slightly less negative than those of naphthalene and perylene
diimides 2 (ꢀ0.27 V) and 3 (ꢀ0.33 V), respectively,
but much less negative than anthracene diimide 4
(ꢀ1.1 V).14b The two outstanding features are that 5b,
relative to 3 and 4, has two well-separated, fully rever-
sible processes. The LUMO energy level of 5b is slightly
lower than those of 2 and 3 but much lower than that
of 4. They are, therefore, promising candidates for an
air-stable n-channel semiconductor.
Figure 3. UV/vis absorption spectra of compounds 3 (blue), 5b
(black), and 2 (red) in the solid state and in CH2Cl2 as solvent.
Figure 3 shows the optical absorption of anthracene
diimide (5b), perylene diimide (3), and naphthalene diimide
(2), the latter two for comparison. The solution UV/vis
spectrum of 5b shows an optical absorption centered around
480 nm. This absorption is red-shifted by approximately 100 nm
relative to 2 and blue-shifted by approximately 50 nm
relative to 3. Therefore, optical spectroscopy of 5 shows a
band gap of ∼2.2 eV, reflecting a πꢀπ* gap approximately
the same as 3 (∼2.2 eV) , but smaller than 4 (∼2.6 eV)14b and
2 (∼2.9 eV).
Fluorescence spectra of 3 and 5b are exhibited in Figure 4.
Both compounds show high fluorescence in solution with a
maximum at 525 and 575 nm, corresponding to a Stokes
Figure 5. Cyclic voltammograms of 2, 3, and 5b in chloroben-
zene, 0.1 M TBBF4. Scan rate = 100 mV/s. Platinum as working
electrode, wave at ca. 0.7 eV is the internal Fc/Fcþ reference.
(15) (a) Amin, S.; Balanikas, G.; Hiie, K.; Hussain, N.; Geddie, J. E.;
Hecht, S. S. J. Org. Chem. 1985, 50, 4642. (b) Ryu, D.; Park, E.; Kim,
D. S.; Yan, S.; Lee, J. Y.; Chang, B. Y.; Ahn, K. H. J. Am. Chem. Soc.
2008, 130, 2394.
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9299.
Density functional theory (DFT) calculations were per-
formed at the B3LYP level of theory with a 6-31G* basis
2562
Org. Lett., Vol. 13, No. 10, 2011

A single crystal of 5a was obtained relatively easily by
slow evaporation from solution in dichloromethane
(Figure 7). The molecular structure shows a nearly planar
core (dihedral angle of ∼4° defined by the planes of
anthracene and 6-membered imide rings). The crystal
structure is a slip-stacked face-to-face molecular packing
Table 1. Optical and Electrochemical Data
theoretical data experimental data
c
λa
HOMO
(eV)
LUMO
(eV)
HOMO
(eV)
LUMOb
(eV)
Eg
entry (nm)
(eV)
˚
with a minimum interplanar spacing of 3.45 A. This motif
and the planar core augurs well for efficient charge-trans-
port properties.
2
3
4
430
545
475
ꢀ6.55
ꢀ5.97
ꢀ5.76
ꢀ6.00
ꢀ3.65
ꢀ3.70
ꢀ3.15
ꢀ3.80
2.90
2.27
2.61
2.20
ꢀ6.30
ꢀ6.33
ꢀ2.82
ꢀ3.51
5b 560
a The intercept of the slope of the absorption tail and the minimum
absorption. b Calculated by measuring the difference between the onset
of reduction and the half-wave potential of the ferrocene standard.
c Calculated from λonset
.
set using the Gaussian 0318 program. The calculated
orbital energies and the tendency of decreasing LUMO
energy from 5-membered diimide to 6-membered diimide
are in good agreement with the experimentally obtained
results (see Table 1). In fact, the DFT calculation shows
that the amine nitrogen in the 6-membered rings, in
contrast to 5-membered rings, is directly involved in
efficient delocalization of electrons with the anthracene
backbone, thus increasing the effective conjugation length
and resulting in a low-lying LUMO energy level and
excellent oxidative stability (Figure 6).
Figure 7. Crystallographic order of compound 5a: (a)
single-molecule; (b) and (c) viewed along two different
crystallographic directions. N,N0 groups have been removed
for clarity.
In summary, we designed and synthesized new electron-
accepting molecules based on a previously unknown an-
thracene diimide containing six-membered imide rings.
The precursor to the imides, the bis anhydride,19 is a new
monomer for polyimides. Compared to a previously re-
ported anthracene diimide containing five-membered
imide rings 4,13b our new anthracene diimides 5aꢀd exhibit
better electron-accepting properties with potential appli-
cation in organic electronics. The theoretical data explain
very well the electronic difference in molecular structure of
5 and 4 and also are in good agreement with experimental
data.
Figure 6. Anthracene rylene diimide structures and lowest un-
occupied molecular orbital (LUMO) distribution.
Acknowledgment. This work was supported by Ko-
narka Technologies Inc. and Department of Energy
(Grant No. DE-FG02-08ER46535). Technical assis-
tance from Dr. Guang Wu for the crystal structure is
acknowledged.
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H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A.,
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J. A. Gaussian, Inc., Pittsburgh, 2003.
Supporting Information Available. Spectroscopic and
other data for compounds 7ꢀ10 and 5aꢀd and crystal-
lographic data for compounds 5a and 8. This material is
available free of charge via the Internet at http://pubs.acs.
org.
(19) Kinoshita, A.; Suzuki, T.; Sakimura, T. Jpn. Kokai Tokkyo
Koho, JP 05333574 A19931217, 1993.
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