Synthesis of 2,5,8,11,14,17-hexafluoro-hexa-peri-hexabenzocoronene for n-type organic field-effect transistors

Article abstract of DOI:10.1021/ol702158a

(Chemical Equation Presented) A fluorine-substituted hexa-peri- hexabenzocoronene was synthesized as a thermostable active material for n-type semiconductors. The LUMO and HOMO energy levels, estimated by UV-vis and photoelectron spectroscopy, were lower

Full text of DOI:10.1021/ol702158a

ORGANIC
LETTERS
2007
Vol. 9, No. 23
4817-4820
Synthesis of
2,5,8,11,14,17-Hexafluoro-hexa-peri-
hexabenzocoronene for n-Type Organic
Field-Effect Transistors
Yoshihiro Kikuzawa,* Tomohiko Mori, and Hisato Takeuchi
Toyota Central Research and Laboratories, Inc., Nagakute, Aichi, 480-1192, Japan
e1319@mosk.tytlabs.co.jp
Received September 2, 2007
ABSTRACT
A fluorine-substituted hexa-peri-hexabenzocoronene was synthesized as a thermostable active material for n-type semiconductors. The LUMO
and HOMO energy levels, estimated by UV vis and photoelectron spectroscopy, were lower by 0.5 eV than those of hexa-peri-hexabenzocoronene.
A field-effect transistor fabricated by vacuum sublimation showed n-type performance with a field-effect mobility of 1.6
on/off ratio of 104. The electron-withdrawing effect of the fluorine substituents changed the polarity from p-type to n-type.
−
-
2
×
10 cm2/Vs and an
Over the past decade, organic field-effect transistors (OFETs)1
have attracted much interest due to their possible applications
as flexible displays, inexpensive sensors, and printable
devices. Electron-transport (n-type) and hole-transport (p-
type) organic materials are also essential for the fabrications
of p-n junction devices and complementary logic circuits.
Positive-type OFETs such as those based on acenes2 and
oligothiophenes3 have been extensively studied and have
excellent characteristics, whereas n-type OFETs are relatively
rare, with unsatisfactory performance. It has recently been
reported that p-type compounds with electronegative groups
may be used as high-performance n-type materials.4 For
example, perfluoropentacene (pentacene substituted with
(3) (a) Chesterfield, R. J.; Newman, C. R.; Pappenfus, T. M.; Ewbank,
P. C.; Haukaas, M. H.; Mann, K. R.; Miller, L. L.; Frisbie, C. D. AdV.
Mater. 2003, 15, 1278. (b) Ie, Y.; Umemoto, Y.; Kaneda, T.; Aso, Y. Org.
Lett. 2006, 8, 5381. (c) Ie, Y.; Nitani, M.; Ishikawa, M.; Nakayama, K.;
Tada, H.; Kaneda, T.; Aso, Y. Org. Lett. 2007, 9, 2115. (d) Yamamoto, T.;
Takimiya, K. J. Am. Chem. Soc. 2007, 129, 2224.
(4) (a) Facchetti, A.; Deng, Y.; Wang, A.; Koide, Y.; Sirringhaus, H.;
Marks, T. J.; Friend, R. H. Angew. Chem., Int. Ed. 2000, 39, 4547. (b)
Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue, Y.;
Sato, F.; Tokito, S. J. Am. Chem. Soc. 2004, 126, 8138. (c) Ando, S.;
Nishida, J.; Fujiwara, E.; Tada, H.; Inoue, Y.; Tokito, S.; Yamashita, Y.
Chem. Mater. 2005, 17, 1261. (d) Yoon, M.-H.; DiBenedetto, S. A.;
Facchetti, A.; Marks, T. J. J. Am. Chem. Soc. 2005, 127, 1348. (e) Ando,
S.; Nishida, J.; Tada, H.; Inoue, Y.; Tokito, S.; Yamashita, Y. J. Am. Chem.
Soc. 2005, 127, 5336. (f) Ando, S.; Murakami, R.; Nishida, J.; Tada, H.;
Inoue, Y.; Tokito, S.; Yamashita, Y. J. Am. Chem. Soc. 2005, 127, 14996.
(g) Naraso; Nishida, J.; Kumaki, D.; Tokito, S.; Yamashita, Y. J. Am. Chem.
Soc. 2006, 128, 9598.
(1) For recent reviews on OFETs, see: (a) Karz, H. E.; Bao, Z.; Gilat,
S. L. Acc. Chem Res. 2001, 34, 359. (b) Dimitrakopoulos, C. D.; Malenfant,
P. R. L. AdV. Mater. 2002, 14, 99. (c) Newman, C. R.; Frisbie, C. D.;
Demetrio, A.; da Silva Filho, D. A.; Bre´das, J.-L.; Ewbank, P. C.; Mann,
K. R. Chem. Mater. 2004, 16, 4436. (d) Sun, Y.; Liu, Y.; Zhu, D. J. Mater.
Chem. 2005, 15, 53. (e) Anthony, J. E. Chem. ReV. 2006, 106, 5028. (f)
Muccini, M. Nat. Mater. 2006, 5, 605. (g) Murphy, A. R.; Fre´chet, J. M.
J. Chem. ReV. 2007, 107, 1066. (h) Zaumseil, J.; Sirringhaus, H. Chem.
ReV. 2007, 107, 1296.
(2) (a) Klauk, H.; Halik, M.; Zschieschang, U.; Schmid, G.; Radlik, W.;
Weber, W. J. Appl. Phys. 2002, 92, 5259. (b) Briseno, A. L.; Miao, Q.;
Ling, M.-M.; Reese, C.; Meng, H.; Bao, Z.; Wudl, F. J. Am. Chem. Soc.
2006, 128, 15576. (c) Tang, M. L.; Okamoto, T.; Bao, Z. J. Am. Chem.
Soc. 2006, 128, 16002.
10.1021/ol702158a CCC: $37.00
© 2007 American Chemical Society
Published on Web 10/16/2007

fluorines) was prepared with the aim of changing the polarity
of pentacene to n-type;4b however, pentacene disproportion-
ation occurred during sublimation for purification and
fabrication.5 The development of thermally and chemically
stable organic materials is thus necessary.
Scheme 1. Attempted Synthesis of 6F-HBC by
Cyclotrimerization
Hexa-peri-hexabenzocoronene (HBC) derivatives,6 pio-
neered by Mu¨llen and co-workers,7 show a very high
chemical stability. The rigidity and planarity of their
π-conjugated cores results in self-assembly of the molecules,
leading to high carrier mobility. With the addition of
functional groups around the periphery, HBCs have been
shown to exhibit solubility, discotic liquid crystallinity, and
additional intermolecular interactions that result in the
formation of columnar stacks.8 The formation of a decyloxy-
and fluorine-substituted HBC (2,5,8,11,14,17-hexakis(decyl-
oxy)-1,3,4,6,7,9,10,12,13,15,16,18-dodecafluoro-hexa-peri-
hexabenzocoronene)9 and perfluoroalkyl-substituted HBCs10
has also been reported. HBC and alkyl-substituted HBCs
exhibit p-type OFET activity,11 whereas fluorine-substituted
HBCs will be expected to show n-type performance. We are
interested in the development of n-type HBCs and report
herein the synthesis, thermostability, and n-type activity of
a new fluorine-substituted HBC that possesses only hydro-
and fluoro-substituents.
We attempted to synthesize 2,5,8,11,14,17-hexafluoro-
hexa-peri-hexabenzocoronene, 6F-HBC, by a well-estab-
lished method7c that involved cobalt-catalyzed cyclotrimer-
ization of 4,4′-difluorodiphenylacetylenes 112 to hexakis(4-
fluorophenyl)benzene 2 (Scheme 1). Although cyclotrimer-
ization of bis(4-trifluoromethylphenyl)acetylenes had previ-
ously been achieved by Jenny’s group,10b in this case 1 did
not react and was recovered. Consequently, another method
via cyclopentadienone was used (Scheme 2).7c Tetrakis(4-
fluorophenyl)cyclopentadienone 313 was prepared by an
Knoevenagel condensation with 1,3-bis(4-fluorophenyl)-2-
propanone and 4,4′-difluorobenzil; Diels-Alder reaction with
1 and 3 gave 2 in 72% yield. Compound 6F-HBC was
obtained by cyclodehydrogenation with FeCl3 (47% yield)
and with AlCl3/Cu(OTf)2 (64%), in contrast to the reaction
of hexakis(4-trifluoromethylphenyl)benzene, which showed
no reaction with either FeCl3 or AlCl3/Cu(OTf)2.10b It can
be seen that, in contrast to the trifluoromethyl substituents,
the fluorine substituents of 2 do not preclude this Scholl-
type cyclodehydrogenation to extend the π-conjugated
system.10
Because 6F-HBC was insoluble in common organic
solvents, it was purified by sublimation to give a yellow
powder that was identified by elemental analysis. The product
was also analyzed using MALDI-TOF MS. Signals at m/z
) 630 were observed in both positive and negative mode;
these were assigned as M•+ and M•-, respectively. These
data indicate that highly pure 6F-HBC was obtained and
confirm the absence of insufficiently reacted byproducts.14
The thermostability of 6F-HBC was estimated by thermo-
gravimetric analysis (TGA). The results were slightly inferior
to those obtained for HBC, but the weight loss at 500 °C
(5) Roberson, L. B.; Kowalik, J.; Tolbert, L. M.; Kloc, C.; Zeis, R.; Chi,
X.; Fleming, R.; Wilkins, C. J. Am. Chem. Soc. 2005, 127, 3069.
(6) (a) Iyer, V. S.; Wehmeier, M.; Brand, J. D.; Keegstra, M. A.; Mu¨llen,
K. Angew. Chem., Int. Ed. 1997, 36, 1604. (b) Watson, M. D.; Fechtenko¨tter,
A.; Mu¨llen, K. Chem. ReV. 2001, 101, 1267. (c) Grimsdale, A. C.; Mu¨llen,
K. Angew. Chem., Int. Ed. 2005, 44, 5592. (d) Wu, J.; Pisula, W.; Mu¨llen,
K. Chem. ReV. 2007, 107, 718.
(7) (a) Herwig, P.; Kayser, C. W.; Mu¨llen, K.; Spiess, H. W. AdV. Mater.
1996, 8, 510. (b) Schmidt-Mende, L.; Fechtenko¨tter, A.; Mu¨llen, K.; Moons,
E.; Friend, R. H.; MacKenzie, J. D. Science 2001, 293, 1119. (c)
Fechtenko¨tter, A.; Tchebotareva, N.; Watson, M.; Mu¨llen, K. Tetrahedron
2001, 57, 3769. (d) Pisula, W.; Kastler, M.; Wasserfallen, D.; Pakula, T.;
Mu¨llen, K. J. Am. Chem. Soc. 2004, 126, 8074. (e) Kastler, M.; Pisula, W.;
Wasserfallen, D.; Pakula, T.; Mu¨llen, K. J. Am. Chem. Soc. 2005, 127,
4286. (f) Breiby, D. W.; Bunk, O.; Pisula, W.; Sφlling, T. I.; Tracz, A.;
Pakula, T.; Mu¨llen, K.; Nielsen, M. M. J. Am. Chem. Soc. 2005, 127, 11288.
(8) (a) Lee, M.; Kim, J.-W.; Peleshanko, S.; Larson, K.; Yoo, Y.-S.;
Vaknin, D.; Markutsya, S.; Tsukruk, V. V. J. Am. Chem. Soc. 2002, 124,
9121. (b) Hill, J. P.; Jin, W.; Kosaka, A.; Fukushima, T.; Ichihara, H.;
Shimomura, T.; Ito, K.; Hashizume, T.; Ishii, N.; Aida, T. Science 2004,
304, 1481. (c) Yamamoto, Y.; Fukushima, T.; Jin, W.; Kosaka, A.; Hara,
T.; Nakamura, T.; Saeki, A.; Seki, S.; Tagawa, S.; Aida, T. AdV. Mater.
2006, 18, 1297. (d) Zhang, G.; Jin, W.; Fukushima, T.; Kosaka, A.; Ishii,
N.; Aida, T. J. Am. Chem. Soc. 2007, 129, 719. (e) Yamamoto, Y.;
Fukushima, T.; Saeki, A.; Seki, S.; Tagawa, S.; Ishii, N.; Aida, T. J. Am.
Chem. Soc. 2007, 129, 9276.
(9) Zhang, Q.; Prins, P.; Jones, S. C.; Barlow, S.; Kondo, T.; An, Z.;
Siebbeles, L. D. A.; Marder, S. R. Org. Lett. 2005, 7, 5019.
(10) (a) Spraul, B. K.; Suresh, S.; Glaser, S.; Perahia, D.; Ballato, J.;
Smith, D. W., Jr. J. Am. Chem. Soc. 2004, 126, 12772. (b) Alameddine,
B.; Aebischer, O. F.; Amrein, W.; Donnio, B.; Deschenaux, R.; Guillon,
D.; Savary, C.; Scanu, D.; Scheidegger, O.; Jenny, T. A. Chem. Mater.
2005, 17, 4798.
(11) (a) van de Craats, A. M.; Warman, J. M.; Fechtenko¨tter, A.; Brand,
J. D.; Harbison, M. A.; Mu¨llen, K. AdV. Mater. 1999, 11, 1469. (b) van de
Craats, A. M.; Stutzmann, N.; Bunk, O.; Nielsen, M. M.; Watson, M.;
Mu¨llen, K.; Chanzy, H. D.; Sirringhaus, H.; Friend, R. H. AdV. Mater. 2003,
15, 495. (c) Mori, T.; Takeuchi, H.; Fujikawa. H. J. Appl. Phys. 2005, 97,
066102.
(13) Elce, E.; Hay, A. S. J. Polym. Sci., Part A: Polym. Chem. 1995,
(12) Mio, M. J.; Kopel, L. C.; Braun, J. B.; Gadzikwa, T. L.; Hull, K.
L.; Brisbois, R. G.; Markworth, C. J.; Grieco, P. A. Org. Lett. 2002, 4,
3199.
33, 1143.
(14) Feng, X.; Wu, J.; Enkelmann, V.; Mu¨llen, K. Org. Lett. 2006, 8,
1145.
4818
Org. Lett., Vol. 9, No. 23, 2007

Scheme 2. Synthesis of 6F-HBC
Figure 2. Photoelectron spectra of HBC (O) and 6F-HBC (b).
substrate, is shown in Figure 1, along with a spectrum of
HBC. There is little difference in shape between the two
spectra, and the HOMO-LUMO energy gap of both materi-
als, obtained from the end absorptions, is 2.7 eV. Based on
photoelectron spectra (Figure 2), the HOMO energy levels
of HBC and 6F-HBC were found to be 5.4 and 5.9 eV,
respectively; thus, the LUMO levels were estimated at 2.7
was less than 2%, which indicates that fluorine substituents
have little effect on the thermostability of HBCs.
The UV-vis absorption spectrum of a thin film of 6F-
HBC, prepared by vacuum sublimation onto a quartz
Figure 3. Output (upper) and transfer (lower) characteristics of
an OFET with 6F-HBC as an active layer.
Figure 1. UV-vis spectra of HBC (- - -) and 6F-HBC (s).
Org. Lett., Vol. 9, No. 23, 2007
4819

and 3.2 eV, respectively. It was concluded that the introduc-
tion of fluorine substituents lowered the LUMO energy level,
facilitating electron injection.
An OFET device with top contact configuration was
fabricated.15 As shown in Figure 3, 6F-HBC shows n-type
performance, in that the drain current (Id) increases with
positive gate voltage (Vg). The electron field-effect mobility
and on/off ratio were estimated from the saturated regime;
values of 1.6 × 10-2 cm2/Vs and 104, respectively, were
obtained.
those of HBC. A FET device based on this material showed
good n-type performance with high carrier mobility. The
introduction of six fluorine substituents as electron-with-
drawing groups resulted in n-type behavior of this HBC
derivative.
Acknowledgment. We thank Mrs. Keiko Fukumoto and
Mr. Kazuo Okamoto (Toyota Central Research and Labo-
ratories, Inc.) for NMR analysis and MALDI-TOF MS
measurements, respectively.
In conclusion, we synthesized a hexafluoro-hexa-peri-
hexabenzocoronene with thermostability equal to that of
hexa-peri-hexabenzocoronene. Both the HOMO and LUMO
energy levels of the new fluorine-substituted HBC, measured
by UV-vis and photoelectron spectroscopy, were lower than
Supporting Information Available: Full experimental
details, synthesis, and characterization of all compounds. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(15) See Supporting Information for the details of the device fabrication.
OL702158A
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Org. Lett., Vol. 9, No. 23, 2007