Hybrid rylene arrays via combination of stille coupling and C-H transformation as high-performance electron transport materials

Article abstract of DOI:10.1021/ja301184r

Hybrid rylene arrays have been prepared via a combination of Stille coupling and C-H transformation. The ability to extend the π system along the equatorial axis of rylenes not only leads to broadened light absorption but also increases the electron affinity, which can facilitate electron injection and transport with ambient stability.

Full text of DOI:10.1021/ja301184r

Communication
pubs.acs.org/JACS
Hybrid Rylene Arrays via Combination of Stille Coupling and C−H
Transformation as High-Performance Electron Transport Materials
Wan Yue,†,‡ Aifeng Lv,†,‡ Jing Gao,†,‡ Wei Jiang,† Linxiao Hao,†,‡ Cheng Li,†,‡ Yan Li,*,†
Lauren E. Polander,§ Stephen Barlow,§ Wenping Hu,† Simone Di Motta,∥ Fabrizia Negri,*,∥
Seth R. Marder,*,§ and Zhaohui Wang*,†
†Beijing National Laboratory for Molecular Science, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of
Sciences, Beijing 100190, China
‡Graduate School of the Chinese Academy of Sciences, Beijing 100190, China
§School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, 901
Atlantic Drive NW, Atlanta, Georgia 30332-0400, United States
∥Dipartimento di Chimica “G. Ciamician”, Universita
̀
di Bologna, Via F. Selmi 2, 40126 Bologna, Italy, and INSTM, UdR Bologna,
Italy
S
* Supporting Information
ABSTRACT: Hybrid rylene arrays have been prepared
via a combination of Stille coupling and C−H trans-
formation. The ability to extend the π system along the
equatorial axis of rylenes not only leads to broadened light
absorption but also increases the electron affinity, which
can facilitate electron injection and transport with ambient
stability.
Figure 1. Perylene diimides 1, naphthalene diimides 2, and hybrid
rylene arrays 3.
he design, synthesis, and characterization of new high-
T
performance organic semiconductors are important for
the development of next-generation optoelectronic devices.1 To
date, there has been a tremendous effort to narrow the gap in
performance (ambient stability, mobility, etc.) between organic
semiconductors with n-channel field-effect transistor (FET)
behavior and their leading p-channel counterparts. Naphthalene
tetracarboxylic diimides (NDIs) and perylene tetracarboxylic
diimides (PDIs) are among the most promising building blocks
for achieving this challenging goal.2 We became interested in
examining hybrid rylene arrays formed by lateral fusion of PDIs
and NDIs, since they could possibly lead to materials that
would have broad absorption and high electron affinity (EA)
and, depending on the substitution on the nitrogen atoms,
could be processable and have a strong tendency to π-stack.3,4
We are particularly interested in the design and synthesis of
novel π-extended electron-poor molecules based on rylene
diimides with unique optoelectronic properties. Recently, some
of us reported the facile homocoupling of tetrahalogenated
PDIs to give triply linked oligo-PDIs via Ullmann reaction and
C−H transformation5 and its use in obtaining a series of
functionalized graphene-ribbon-type molecules.6 Quite re-
cently, tetracene tetracarboxylic diimides have also been
synthesized via direct double ring extension of electron-
deficient NDIs involving metallacyclopentadienes.7 Herein we
present a facile one-pot synthesis of a new family of hybrid
rylene diimide arrays (3, Figure 1) via a combination of Stille
coupling and C−H transformation. In general, successful
extension of the π system along the equatorial axis of rylenes
can lead to increased optical absorption and in particular to
higher EA, facilitating electron injection and increasing the
possibility of transport with ambient stability, although there
are exceptions (e.g., expansion of perylene diimides to
coronene diimides leads to blue-shifted absorption and
increased LUMO energies).8 Indeed, the hybrid rylene arrays
exhibit excellent organic thin-film transistor (OTFT) character-
istics under ambient conditions.
Stille cross-couplings have proved to be an especially popular
tool for carbon−carbon bond formation because of the air and
moisture stability of organotin reagents as well as the excellent
functional group compatibility.9 Trialkyltin derivatives are
usually obtained from halogen-substituted aromatics via
halogen−lithium exchange followed by reaction of the lithium
intermediate with trialkyltin chloride.10 Since NDIs and PDIs
are not stable toward alkyllithiums, this approach is not
applicable, and until recently, their tin derivatives have
remained hypothetical. However, some of us have recently
reported that mono- and distannyl NDI derivatives can be
obtained by coupling of the corresponding mono- and dibromo
derivatives with Bu3Sn−SnBu3 in the presence of Pd2(dba)3
and P(o-tol)3 in toluene.11 The same procedure was used to
Received: February 6, 2012
Published: March 21, 2012
© 2012 American Chemical Society
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Journal of the American Chemical Society
Communication
synthesize the 2-tributyltin- and N,N′-dioctyl-substituted NDI 5
(Scheme 1).
active layers in organic photovoltaic cells.13 The absorption
spectrum of the singly linked NDI−PDI compound 8 is
essentially a superposition of those of the NDI and PDI units
(380 and 527 nm, respectively; Figure 2), suggesting weak
a
Scheme 1. Synthesis of Hybrid Rylene Arrays
Figure 2. UV−vis absorption spectra of hybrid rylene arrays 8
(magenta), 9 (green), 10a (black), and 10b (blue) in chloroform
(bottom) and a comparison with the corresponding TDDFT/6-31G*-
computed spectra not including vibronic structures (top).
communication between the NDI and PDI, as implied by the
significant computed twist angle between the two rylene units
(see Figure S1). This conclusion is further supported by a
comparison of the computed absorption spectra of the NDI,
the PDI, and 8 (see Figure S4). In contrast, the absorption
spectra of the doubly linked hybrid NDI−PDI and NDI−PDI−
NDI arrays are more complicated, with low-energy maxima
bathochromically shifted to ca. 610 nm (Figure 2). An analysis
in terms of the orbital nature of the TD-B3LYP/6-31G*-
computed electronic transitions of 9 and 10 sheds more light
on the nature of the lowest-energy transitions. As shown in
Figure 3, the HOMOs of the arrays are mainly localized on the
PDI unit, while the LUMOs are mainly localized on the NDI
unit(s). As a result, the weak lowest-energy transition, which is
dominated by the HOMO → LUMO excitation, displays some
charge-transfer character (see Figure S6), which is also the
a
Conditions: (a) Pd2(dba)3, P(o-tol)3, Bu3Sn−SnBu3, toluene, reflux;
(b) Pd(PPh3)4, CuI, toluene, reflux; (c) Pd(PPh3)4, toluene, reflux.
Yields: 5 (80%), 8 (25%), 9 (33%), 10a (46%), 10b (40%), and 10c
(35%).
Inspired by the previous creation of fused aromatic rings via
Ullmann reaction and C−H transformation, we envisaged that
the cross-coupling of this key intermediate 5 with halogenated
PDIs would provide a straightforward and promising method
for construction of fused hybrid NDI−PDI arrays via Stille
coupling and C−H transformation. Accordingly, 1,12-dichlori-
nated perylene diimide 612 was chosen as model substrate;
cross-coupling with 5 using Pd(PPh3)4 and CuI remarkably
afforded singly linked and doubly linked compounds, named
singly linked NDI−PDI 8 and hybrid NDI−PDI array 9,
respectively. Encouraged by the success of this annulation, we
used readily available 1,6,7,12-tetrachloro perylene diimides 7
to check the scope of our procedure. By this method, different
substituents can be conveniently introduced into the extended
hybrid NDI−PDI−NDI array 10.
Because of the steric encumbrance effect involving the
oxygen atoms of the NDI and the neighboring hydrogens of the
PDI, the B3LYP/6-31G*-optimized geometries of 9 and 10
predict their cores to be markedly nonplanar, while the NDI
and PDI units in the singly linked array 8 are found to be
almost perpendicular (see Figures S1−S3 in the Supporting
Information). Similarly to PDI arrays,5d the heliciform and
nonheliciform structures correspond to the lowest-energy
conformers of 9 and 10 (see Table S1).
Figure 3. Energies and shapes of B3LYP/6-31G* frontier orbitals
(HOMOs and LUMOs) of model PDI, NDI, 8, 9, and 10, showing the
dominant orbital parentage across the hybrid rylene arrays.
As we expected, the hybrid rylene arrays show broad
absorption with high absorptivity over much of the visible
region, suggesting the possible application of these arrays as
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Journal of the American Chemical Society
Communication
origin of the underestimation of its energy at the TD-B3LYP/6-
31G* level. The next transition, which has a higher intensity,
deserves a comment, since its energy decreases considerably in
going from 9 (ca. 480 nm) to 10 (ca. 550 nm). This band is
dominated by a π → π* electronic excitation to the LUMO
from an occupied orbital bearing the same parentage for 9 and
10. The occupied π orbital is highly delocalized on the
extended π core (see Figures S7−S8) since it results from PDI
and NDI orbitals that have suitable energy and shape to mix
strongly. Therefore, the energy of this transition decreases
remarkably with the extension of the aromatic core by fusion of
NDI and PDI units.
Figure 4. (left) Output and (right) transfer characteristics of organic
FETs consisting of thin films of hybrid rylene array 10b with a
mobility of 0.25 cm2 V−1 s−1 and an on/off ratio of 107.
The redox properties of these hybrid rylene arrays were
investigated by cyclic voltammetry in dichloromethane (vs Ag/
AgCl). The half-wave reduction potentials of the representative
compounds are −0.63 and −1.11 V for NDI; −0.56 and −0.82
V for PDI; −0.49, −0.64, −0.88, and −1.17 V for singly linked
NDI−PDI 8; −0.19, −0.52, −1.14, and −1.38 V for hybrid
NDI−PDI array 9; and −0.16, −0.35, −0.63, and −0.84 V for
hybrid NDI−PDI−NDI array 10a. The first reduction
potentials of these hybrid rylene arrays are much less negative
than those of parent the NDI and PDI (Table 1), indicating
transformation. The success of π-system extension along the
equatorial axis of rylenes not only leads to a dramatically
broadened absorption spectrum but also increases the electron
affinities to facilitate electron injection and transport with
ambient stability. One of these hybrid rylene arrays exhibits
excellent OTFT characteristics under ambient conditions.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental details and characterization data for all new
compounds; absorption spectrum of hybrid rylene array 10c;
cyclic voltammograms of hybrid rylene arrays 8, 9, and 10; and
computational details and additional computational results.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Table 1. Optoelectronic Properties and Energy Levels of
Hybrid Rylene Arrays
a
b
c
d
e
λ1(nm)
E1r (V)
EA (eV)
IP (eV)
Eg (eV)
f
NDI
380
527
532
608
610
614
613
−0.63
−0.56
−0.49
−0.19
−0.16
−0.20
3.90
3.91
3.98
4.24
4.28
4.26
4.35
7.02
6.21
6.19
6.10
6.20
6.16
6.25
3.12
2.30
2.21
1.86
1.92
1.90
1.90
g
PDI
8
AUTHOR INFORMATION
Corresponding Author
yanli@iccas.ac.cn; fabrizia.negri@unibo.it; seth.marder@
chemistry.gatech.edu; wangzhaohui@iccas.ac.cn
■
9
10a
10b
10c
−0.12
Notes
a
b
Peak in the visible region. Half-wave redox potential (in V vs Ag/
The authors declare no competing financial interest.
AgCl) measured in CH2Cl2 at a scan rate of 0.1 V/s with ferrocene as
c
an internal potential marker. Estimated from the onset potential of
d
ACKNOWLEDGMENTS
the first reduction wave. Ionization potential estimated from the EA
■
e
and Eg. Band-gap energy obtained from the edge of the absorption
For financial support of this research, we thank the National
Natural Science Foundation of China (91027043, 21190032,
20721061), the 973 Program (2011CB932301,
2012CB932903), NSFC−DFG Joint Project TRR61, Solvay,
the Chinese Academy of Sciences, the STC Program of the
National Science Foundation (DMR-0120967), and Italian
PRIN 2008, Project JKBBK4.
f
spectrum. NDI: N,N′-di-n-octylnaphthalene-1,2:6,7-tetracarboxylic
g
acid diimide. PDI: N,N′-bis(2,6-diisopropylphenyl)perylene-3,4:9,10-
tetracarboxylic acid diimide.
that they are considerably stronger electron acceptors. The EAs
of these compounds were estimated from the onset potentials
of the first reduction waves; those of the fused arrays are all in
excess of 4.2 eV, meeting the criterion for achieving air-stable
electron transport.3b,4c
REFERENCES
■
(1) (a) Facchetti, A. Mater. Today 2007, 10, 28. (b) Usta, H.;
Facchetti, A.; Marks, T. J. Acc. Chem. Res. 2011, 44, 501.
Thin films of the hybrid rylene array 10b with thicknesses of
40−60 nm were spin-coated from a chloroform solution onto
octadecyltrichlorosilane-treated SiO2/Si substrates. Gold elec-
trodes with width/length of 1 mm/0.05 mm were applied on
the organic thin films through a shadow mask, affording a
bottom-gate top-contact device configuration. All devices were
tested under ambient conditions. The unannealed thin-film
devices showed a moderate electron mobility of 0.02 cm2 V−1
s−1. Thermal annealing of the thin films led to a substantial
improvement in the device performance. The highest electron
mobility (0.25 cm2 V−1 s−1) was achieved after annealing at 220
°C and was accompanied by a high current on/off ratio of 107
(Figure 4).
(2) For recent reviews, see: (a) Wurthner, F.; Stolte, M. Chem.
̈
Commun. 2011, 47, 5109. (b) Huang, C.; Barlow, S.; Marder, S. R. J.
Org. Chem. 2011, 76, 2386. (c) Weil, T.; Vosch, T.; Hofkens, J.;
Peneva, K.; Mullen, K. Angew. Chem., Int. Ed. 2010, 49, 9068.
̈
(3) (a) Jones, B. A.; Ahrens, M. J.; Yoon, M.-H.; Facchetti, A.; Marks,
T. J.; Wasielewski, M. R. Angew. Chem., Int. Ed. 2004, 43, 6363.
(b) Gsanger, M.; Oh, J. H.; Konemann, M.; Hoffken, H. W.; Krause,
̈
̈
̈
A.-M. ; Bao, Z.; Wurthner, F. Angew. Chem., Int. Ed. 2010, 49, 740.
̈
(c) Schmidt, R.; Oh, J. H.; Sun, Y.-S.; Deppisch, M.; Krause, A.-M. ;
Radacki, K.; Braunschweig, H.; Konemann, M.; Erk, P.; Bao, Z.;
̈
Wurthner, F. J. Am. Chem. Soc. 2009, 131, 6215.
̈
(4) (a) Guo, X.; Watson, M. D. Org. Lett. 2008, 10, 5333. (b) Yan,
H.; Chen, Z.; Zheng, Y.; Newman, C.; Quinn, J. R.; Dotz, F.; Kastler,
̈
M. Nature 2009, 457, 679. (c) Jones, B. A.; Facchetti, A.; Wasielewski,
M. R.; Marks, T. J. J. Am. Chem. Soc. 2007, 129, 15259. (d) Katz, H. E.;
Lovinger, A. J.; Johnson, J.; Kloc, C.; Siegrist, T.; Li, W.; Lin, Y.-Y.;
In summary, a new family of hybrid rylene arrays has been
prepared via a combination of Stille coupling and C−H
5772
dx.doi.org/10.1021/ja301184r | J. Am. Chem. Soc. 2012, 134, 5770−5773

Journal of the American Chemical Society
Communication
Dodabalapur, A. Nature 2000, 404, 478. (e) Thalacker, C.; Roger, C.;
̈
Wurthner, F. J. Org. Chem. 2006, 71, 8098. (f) Gao, X.; Di, C.; Hu, Y.;
̈
Yang, X.; Fan, H.; Zhang, F.; Liu, Y.; Li, H.; Zhu, D. J. Am. Chem. Soc.
2010, 132, 3697. (g) Hu, Y.; Gao, X.; Di, C.; Yang, X.; Zhang, F.; Liu,
Y.; Li, H.; Zhu, D. Chem. Mater. 2011, 23, 1204.
(5) (a) Qian, H.; Wang, Z.; Yue, W.; Zhu, D. J. Am. Chem. Soc. 2007,
129, 10664. (b) Qian, H.; Yue, W.; Zhen, Y.; Di Motta, S.; Di Donato,
E.; Negri, F.; Qu, J.; Xu, W.; Zhu, D.; Wang, Z. J. Org. Chem. 2009, 74,
6275. (c) Shi, Y.; Qian, H.; Li, Y.; Yue, W.; Wang, Z. Org. Lett. 2008,
10, 2337. (d) Qian, H.; Negri, F.; Wang, C.; Wang, Z. J. Am. Chem.
Soc. 2008, 130, 17970. (e) Zhen, Y.; Wang, C.; Wang, Z. Chem.
Commun. 2010, 46, 1926.
(6) (a) Wu, Y.; Zhen, Y.; Ma, Y.; Zheng, R.; Wang, Z.; Fu, H. J. Phys.
Chem. Lett. 2010, 1, 2499. (b) Wang, H.; Su, H.; Qian, H.; Wang, Z.;
Wang, X.; Xia, A. J. Phys. Chem. A 2010, 114, 9130.
(7) (a) Yue, W.; Gao, J.; Li, Y.; Jiang, W.; Di Motta, S.; Negri, F.;
Wang, Z. J. Am. Chem. Soc. 2011, 133, 18054. (b) Katsuta, S.; Tanaka,
K.; Maruya, Y.; Mori, S.; Masuo, S.; Okujima, T.; Uno, H.; Nakayama,
K.; Yamada, H. Chem. Commun. 2011, 47, 10112. (c) Suraru, S.-L.;
Zschieschang, U. Z.; Klauk, H.; Wurthner, F. Chem. Commun. 2011,
̈
47, 11504.
(8) (a) Rohr, U.; Schlichting, P.; Bohm, A.; Gross, M.; Meerholz, K.;
̈
Brauchle, C.; Mullen, K. Angew. Chem., Int. Ed. 1998, 37, 1434.
̈
̈
(b) Adachi, M.; Nagao, Y. Chem. Mater. 2001, 13, 662. (c) Eversloh, C.
L.; Li, C.; Mullen, K. Org. Lett. 2011, 13, 4148. (d) Li, Y.; Xu, L.; Liu,
̈
T.; Yu, Y.; Liu, H.; Li, Y.; Zhu, D. Org. Lett. 2011, 13, 5692.
(9) (a) Kosugi, M.; Sasazawa, K.; Shimizu, Y.; Migita, T. Chem. Lett.
1977, 301. (b) Milstein, D.; Stille, J. K. J. Am. Chem. Soc. 1978, 100,
3636.
(10) (a) Littke, A. F.; Schwarz, L.; Fu, G. C. J. Am. Chem. Soc. 2002,
124, 6343. (b) Zhang, L.; Tan, L.; Hu, W.; Wang, Z. J. Mater. Chem.
2009, 19, 8216.
(11) Polander, L. E.; Romanov, A. S.; Barlow, S.; Hwang, D. K.;
Kippelen, B.; Timofeeva, T. V.; Marder, S. R. Org. Lett. 2012, 14, 918.
(12) Zhen, Y.; Qian, H.; Xiang, J.; Qu, J.; Wang, Z. Org. Lett. 2009,
11, 3084.
(13) Li, C.; Wonneberger, H. Adv. Mater. 2012, 24, 613.
5773
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