surpassing that of amorphous silicon have been devel-
oped over the past decades, including triphenylenes,7
phthalocyanines,8 porphyrins,9 hexabenzocoronene,10 and
truxenes.11 In contrast, n-type disk-shaped molecular sys-
tems are still much underdeveloped.12 Even more so, there
lacks a detailed study of their electronic properties in the
context of thin film devices.
compounds, measured both in the context of field effect
transistors and by the space-charge limited-current
(SCLC) model, show drastically different directional ani-
sotropy. As revealed by X-ray scattering and atomic force
microscopic (AFM) analyses, a strong correlation between
the film morphology and the charge transport behavior
has been established.
n-Type naphthalenetetracarboxylic diimide (NDI) and
perylenetetracarboxylic diimide (PDI)-based materials
have become increasingly attractive due to their high
charge-carrier mobilities, superior light absorption in the
wavelength range of visible light, and high thermal, che-
mical, and photostability.13 Incorporating these electron-
deficient units into c3-symmetric disk-shaped molecular
skeletons poses as an appealing approach toward achieving
good optical, electronic, and self-assembly properties.12e
Herein, we report the investigation of a series of novel n-
type disk-shaped molecules that contain a triphenylene
core fused with three naphthaleneimide imidazole or per-
yleneimide imidazole “arms” (Scheme 1). As a result of
extended conjugation, the fusion has led to enhanced
optical properties along with well-aligned frontier orbital
energies. Moreover, charge carrier mobilities of these
Scheme 1. Synthetic Scheme and Molecular Structures of TP-
TNI, TP-TPI, NI, and PIa
(7) (a) Kumar, S. Liq. Cryst. 2004, 31, 1037–1059. (b) Sarhan,
A. A. O.; Bolm, C. Chem. Soc. Rev. 2009, 38, 2730–2744.
(8) (a) Chu, C.-W.; Shrotriya, V.; Li, G.; Yang, Y. Appl. Phys. Lett.
ꢀ
2006, 88, 1535041–3. (b) Fischer, M. K. R.; Lopez-Duarte, I.; Wienk,
€
M. M.; Martı
Am. Chem. Soc. 2009, 131, 8669–8676. (c) de la Escosura, A.; Martı
Dıaz, M. V.; Torres, T.; Grubbs, R. H.; Guldi, D. M.; Neugebauer, H.;
´
nez-Dı
´
az, M. V.; Janssen, R. A. J.; Bauerle, P.; Torres, T. J.
a TP-TNI and TP-TPI are obtained as a mixture of symmetric and
asymmetric isomers, with only the structures of symmetric ones shown.
´
nez-
´
Winder, C.; Drees, M.; Sariciftci, N. S. Chem.;Asian J. 2006, 1À2, 148–
154.
(9) (a) Sun, Q.; Dai, L.; Zhou, X.; Li, L.; Li, Q. Appl. Phy. Lett. 2007,
91, 253505/1–253505/3. (b) Sakurai, T.; Tashiro, K.; Honsho, Y.; Saeki,
A.; Seki, S.; Osuka, A.; Muranaka, A.; Uchiyama, M.; Kim, J.; Ha, S.;
Kato, K.; Takata, M.; Aida, T. J. Am. Chem. Soc. 2011, 133, 6537–6540.
(10) (a) Shklyarevskiy, I. O.; Jonkheijm, P.; Stutzmann, N.; Wasser-
berg, D.; Wondergem, H. J.; Christianen, P. C. M.; Schenning, A. P. H.
Scheme 1 shows the synthesis of the naphthaleneimide-
based trimer TP-TNI, the peryleneimide-based trimer
TP-TPI, and their respective single “arm” counterparts,
i.e. naphthaleneimide imidazole (NI) and peryleneimide
imidazole (PI). The trimeric TP-TNI and TP-TPI are
obtained as a statistical mixture of cis- (symmetric) and
trans- (asymmetric) isomers from the condensation reaction
between hexaaminotriphenylene and the corresponding
anhydrides. Branched swallow-tail alkyl chains are em-
ployed as the imide substituent to endow good solubility in
common organic solvents. Both TP-TNI and TP-TPI give
very broad NMR spectra across a wide range of tempera-
tures. Nevertheless, their identities are fully supported by
mass spectrometry and elementary analyses. The trimers
are thermally stable above 400 ꢀC as revealed by thermo-
gravimetric analysis (TGA). No thermal transitions could
be observed in differential scanning calorimetry (DSC) in a
wide temperature range from 20 to 350 ꢀC at various
scanning rates (10 and 2 ꢀC minÀ1) (Figures S1ÀS2,
Supporting Information, SI).
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C. J. Am. Chem. Soc. 2006, 128, 10700–10701. (c) Plunkett, K. N.;
Godula, K.; Nuckolls, C.; Tremblay, N.; Whalley, A. C.; Xiao, S. X.
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The optical properties of these compounds are inves-
tigated in both solution and thin film. The UVÀvis
spectra of TP-TNI and TP-TPI in CHCl3 solution reveal
(Figure 1a) broad absorption in the visible region, with
maxima at 502 nm (ε = 25 600 MÀ1 cmÀ1) and 624 nm
(ε = 49200 MÀ1 cmÀ1), respectively. The absorption spec-
trum of TP-TNI is significantly red-shifted as compared to
those of monomeric NI as a result of more extensive
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