Soluble Twisted Diarenoperylenes: Synthesis, Characterization, and Device Performance

Article abstract of DOI:10.1021/acs.orglett.8b01810

Two stable TIPS-ethynyl functionalized polycyclic aromatic hydrocarbons (PAHs), dibenzo[a,j]perylene (TIPS-DBP), and dinaphtho[a,j]perylene (TIPS-DNP), which contain two rows of linear acenes joined by benzene rings, have been synthesized and characterized. It is found that the two twisted PAHs easily form one-dimensional charge-transport systems with short C-C contacts. The crystal of TIPS-DBP shows a hole mobility up to 0.17 cm² V^-1s^-1, while the crystal of TIPS-DNP shows a hole mobility up to 0.74 cm² V^-1 s^-1.

Full text of DOI:10.1021/acs.orglett.8b01810

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Soluble Twisted Diarenoperylenes: Synthesis, Characterization, and
Device Performance
Xinyue Liu,† Meng Chen,† Chengyi Xiao,† Ning Xue,† and Lei Zhang*,†,‡
†College of Energy, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical
Technology, Beijing 100029, China
‡State Key Lab of Organic−Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China
S
* Supporting Information
ABSTRACT: Two stable TIPS-ethynyl functionalized polycyclic aromatic
hydrocarbons (PAHs), dibenzo[a,j]perylene (TIPS-DBP), and dinaphtho-
[a,j]perylene (TIPS-DNP), which contain two rows of linear acenes joined by
benzene rings, have been synthesized and characterized. It is found that the
two twisted PAHs easily form one-dimensional charge-transport systems with
short C−C contacts. The crystal of TIPS-DBP shows a hole mobility up to
0.17 cm2 V−1s−1, while the crystal of TIPS-DNP shows a hole mobility up to 0.74 cm2 V−1 s−1.
uring the past decades, the linear acenes have been
Dstudied extensively for their interesting optoelectronic
properties and potential device applications.1 However, it is
now clear that large linear acenes that have relatively high
carrier mobilities readily undergo photoinduced oxidation,
dimerization, or polymerization due to the biradical character
in the ground state.2 In recent years, different strategies have
been developed to prepare stable linear acenes through the
addition of either electron-withdrawing or bulky substituents
on the reactive sites to decrease the lowest unoccupied
molecular orbital (LUMO) energy levels.1−3 On the other
hand, peri-fusing two rows of linear acenes together has
recently emerged as another promising strategy to topologi-
cally tune their π electron structures, which can significantly
affect stability and optoelectronic properties.4 In addition to
providing the possibility of preparing two-dimensional nano-
graphenes or double helicenes,5 this strategy indeed has
Figure 1. Representative PAHs which contain two rows of tetracene
allowed for the resulting polycyclic aromatic hydrocarbons
moieties with different fusion modes.
(PAHs) with an additional Clar sextet, which typically are
more stable than linear analogs with only one Clar sextet.6
Therefore, there has been a large amount of synthetic
activity to prepare peri-fused PAH systems.7 For example,
displays a biradical character but with a relatively large
biradical index (y0 = 0.72).10 In contrast, a Z-shaped acene
Briseno et al., Frigoli et al., Tykwinski et al., and Chen et al.
which contains two tetracene moieties joined at the zigzag
positions by an antiaromatic pentalene unit, reported by Chi
and co-workers, is extremely stable with a half-life of 54 days
(Figure 1).11 Interestingly, by replacement of six-membered
rings with five-membered rings in tetrabenzo[a,f,j,o]perylene, a
new nonplanar cyclopenta-fused PAH with two benzo[b]-
fluorene subunits, reported by Miao and co-workers in 2015,
exhibits a hole mobility up to 1.0 cm2 V−1 s−1.12 These results
have demonstrated that the fusion mode and molecular
geometry have significant effects on the electronic properties,
independently reported a series of compounds so-called
bistetracenes that contain two rows of tetracene moieties
fused at the zigzag positions with different fusion modes
(Figure 1).8 These molecules with two Clar sextets exhibit
charge carrier mobilities in the range of 0.1 to 6.1 cm2 V−1 s−1
with remarkable stability in solution. However, Mullen and
̈
Feng synthesized another “bistetracene” molecule, tetrabenzo-
[a,f,j,o]perylene, in which two tetracenes are joined by the
central benzene ring, which was found to possess a singlet
biradical character (y0 = 0.61) in the ground state that easily
undergoes Diels−Alder reaction with oxygen (Figure 1).9
Notably, a planar zigzag-edged nanographene, 4-peri-acene
(peri-tetracene), reported by the same group very recently, also
Received: June 11, 2018
© XXXX American Chemical Society
A
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Letter
stability, and solubility of the PAHs, which are critical for
device applications.7−13
anion and subsequently by nucleophilic addition reaction with
diketones 4 and 10 gave the relative alcohol derivatives,
followed by a reductive aromatization with SnCl2, providing
the desired products TIPS-DBP and TIPS-DNP in 18% and
56% yields, respectively, which are soluble in common solvents
and purified via silica gel column chromatography. The
molecular structures were unambiguously characterized by
NMR, mass spectrometry, and X-ray crystallography (see the
Supporting Information).
Despite the intriguing molecular properties, it is a particular
challenge to prepare peri-fused PAHs, probably due to the
extremely low solubility and unexpected reactivity of the
intermediates.3c,14 Herein, we describe the synthesis of two
triisopropylsilyl(TIPS)-ethynyl functionalized PAHs, dibenzo-
[a,j]perylene (TIPS-DBP) and dinaphtho[a,j]perylene (TIPS-
DNP), by fusion of benzenes and naphthalenes to perylenes,
respectively. The resulting PAHs can be regarded as two rows
of anthracene and tetracene moieties peri-joined by the
benzene ring, which have twisted conformations due to the
steric hindrance of their cove regions. It should be noted that
recent studies have demonstrated that nonplanar PAH systems
usually exhibit high solubility and stability, and self-assemble
into special supermolecular structures demonstrating efficient
charge transport.15 In particular, we envision that the fusion
mode within dinaphtho[a,j]perylene and “bistetracene” mole-
cules could lead to key differences in electronic structure,
stability, solubility and transport properties, which provide
deep understanding of the structure−property relationships in
nonplanar peri-fused PAHs. In addition, TIPS-ethynyl
substituents on the PAHs are expected to increase the
solubility, crystallinity, and stability of acenes.1b,c
The UV−vis absorption spectra of TIPS-DBP and TIPS-
DNP were measured in chloroform solution (Figure 2A). The
Figure 2. (A) UV−vis spectra of TIPS-DBP and TIPS-DNP in
chloroform solution (10−5 M). (B) Electrochemical properties of
TIPS-DBP and TIPS-DNP in dichloromethane with tetrabutylam-
monium hexafluorophosphate (TBAPF6, 0.1 M) as the supporting
electrolyte.
Scheme 1 shows the synthesis of soluble twisted
diarenoperylenes. To prepare TIPS-DBP and TIPS-DNP,
Scheme 1. Synthetic Steps to TIPS-DBP and TIPS-DNP
two spectra are generally similar in shape and exhibit two
major absorption bands: a set of absorption bands at short
wavelength, and a broad longest wavelength absorption band,
which are characteristic of the acene-like derivatives.17 As
expected, the longest wavelength absorption value for TIPS-
DNP (λmax = 719 nm) shows a red shift of approximately 100
nm relative to TIPS-DBP due to the extended conjugation
length. The optical gaps are 1.84 and 1.59 eV for TIPS-DBP
and TIPS-DNP, respectively.
The cyclic voltammograms (CV) of TIPS-DBP and TIPS-
DNP exhibit two well-defined, reversible oxidation and
reduction waves (Figure 2B). For TIPS-DBP, the half-wave
reduction−oxidation potentials are at −1.86, −1.48, 0.38, 0.94
V and LUMO/HOMO are estimated to be −3.52/−5.11 eV
(relative to Fc/Fc+, 4.8 eV). For TIPS-DNP, the half-wave
reduction−oxidation potentials are at −1.61, −1.30, 0.21, 0.70
V, and the LUMO/HOMO are estimated to be −3.58/−4.94
eV. These values indicate that the fusion of two additional
benzene rings onto the TIPS-DBP leads to a significant
increase of HOMO levels, but a minor influence on LUMO
levels. The density functional theory (DFT) calculations
indicate that the two compounds possess very similar
HOMO and LUMO distributions (see Figure S2, Supporting
Information). Their orbitals are distributed over the aromatic
cores and CC bonds. The calculated HOMO/LUMO by
DFT are −4.48/−2.45 eV for TIPS-DBP and −4.29/−2.68 eV
for TIPS-DNP, respectively, which are in good agreement with
the trend of the experimental values.
dibenzo[a,j]perylene-dione 4 and dinaphtho[a,j]perylene-
dione 10 are the key intermediate compounds. Diketone 4
was first synthesized by rearrangement of dilactone in
polyphosphoric acid.16 Herein, we developed a new synthetic
route to prepare 4 by a simple two-step pathway. A Suzuki
coupling reaction between commercially available compounds
1 and 2 allowed us to prepare diester 3 in a 30% yield. A
subsequent acid-prompted (CF3SO3H/CH3SO3H) cyclization
of 3 provided 4 in 63% yield. Initially, we attempted to prepare
diester 9 via a Suzuki coupling reaction between 1 and 5, but
only starting materials were recovered. When the Suzuki
reaction between 6 and 7 was conducted, the expected 9 was
isolated in 5% yield along with 30% yield of 8. Unfortunately,
the change of catalyst, solvent, and base had a very minor
positive effect on the yield of 9. However, we were pleased to
discover that 8 could serve as a starting material to react with 7
to afford 9 in an acceptable yield of 41%, which was readily
converted to diketone 10 with 46% yield. With diketones in
hand, lithiation of TIPS-acetylene with n-BuLi to form its
Single crystals of TIPS-DBP and TIPS-DNP that were
suitable for X-ray structure determination, were readily grown
from hexane and chloroform. Single-crystal XRD revealed that
the two molecules have twisted conformations with significant
bending of alkyne substituents (CAr−Csp−Csp ≈ 176−178°,
and Csp−Csp−Si ≈ 171−176°) (Figure 3A,B). Like other
twisted PAHs, these two PAHs are chiral, with P,P- and M,M-
B
DOI: 10.1021/acs.orglett.8b01810
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Organic Letters
Letter
Figure 3. ORTEP drawing structures with 50% probability of (A)
TIPS-DBP and (B) TIPS-DNP. Crystal packing of (C) TIPS-DBP
and (D) TIPS-DNP. (M,M-Enantiomers are in red, P,P-enantiomers
are in green; TIPS substituents and hydrogen atoms are omitted for
clarity.)
Figure 4. Transfer (left) and output (right) curves of OFET devices
based on single-crystalline microfibers: (A) TIPS-DBP and (B)
TIPS-DNP.
enantiomers in the crystals. For TIPS-DBP, it crystallizes in
the Pca21 space group and has eight molecules per unit cell,
which have slightly different cove region angles (see Figure S3,
Supporting Information). In contrast to p-CF3Ph-substituted
dibenzo[a,j]perylene, which adopts two-dimensional herring-
bone-like packing, in the crystal of TIPS-DBP, M,M- and P,P-
enantiomers form a one-dimensional (1-D) π-stacking motif
with an alternate arrangement and the TIPS-ethynyl
substituents in adjacent enantiomers are arranged in a rotation
angle of 45° (Figure 3C). This type of intermolecular
organization is reminiscent of the TIPS-ethynyl functionalized
angular acenes with small aspect ratios, which give rise to a 1-D
columnar arrangement with a rotation of TIPS-ethynyl groups
in adjacent molecules to alleviate the unfavorable electrostatic
interactions found in perfectly cofacial π−π stacking and steric
repulsion between the bulky TIPS substituents as well.4d,e The
short C−C contacts between adjacent enantiomers are in the
range of 3.33−3.38 Å, which are shorter than double the van
der Waals radius of carbon. For TIPS-DNP, it crystallizes in
the P42/n space group and has four molecules per unit cell.
The two tetracene moieties are slightly curved and lead to
different cove region angles (42.6° and 43.8°, Figure S3,
Supporting Information). Similar to TIPS-DBP, the TIPS-
DNP crystal contains a pair of enantiomers that form 1-D π-
stacking motif in an alternating fashion to each other with the
TIPS-ethynyl groups arranged in a larger rotation angle of 85°,
as shown in Figure 3D. There are multiple short C−C contacts
between adjacent molecules in the range of 3.31−3.38 Å,
which exist only between two tetracene moieties. The π−π
distance between the benzene rings joining the two tetracene
moieties, which are parallel with each other, is 3.87 Å within a
given stack. Subsequently, we evaluated the intrinsic charge
carrier mobilities of the semiconductors in the form of single-
crystalline microfibers with crystal dimensions of half μm wide
and hundreds μm long, which were prepared by slow
evaporation of toluene solution (see Figure S4, Supporting
Information). The single crystalline field-effect transistors were
fabricated by a “gold strips” technique on the octadecyltri-
chlorosilane (OTS) treated substrate (OTS-SiO2/Si) with Au
as electrodes.18 Parts A and B of Figure 4 show the output and
transfer characteristics of TIPS-DBP and TIPS-DNP micro-
fibers tested under ambient conditions. Compared to p-CF3Ph-
substituted dibenzo[a, j]perylene, which exhibits an ambipolar
behavior with a maximum electron mobility of 0.002
cm2V−1s−1 and a maximum hole mobility of 0.04 cm2 V−1
s−1, TIPS-DBP shows exclusively p-type charge transport with
an average mobility of 0.09 cm2 V−1 s−1 and a maximum
mobility up to 0.17 cm2 V−1 s−1. In contrast, TIPS-DNP shows
an average hole mobility of 0.33 cm2 V−1 s−1, and the highest
mobility is up to 0.74 cm2 V−1 s−1, which is one of the highest
of the TIPS-ethynyl functionalized polyacenes, with 1-D
packing that is unfavorable for efficient charge transport due
to the insulating TIPS substituents between different stacks,
resulting in inefficient electronic interactions between different
stacks.8
Finally, we tested the stability of TIPS-DBP and TIPS-DNP
in solution. TIPS-DBP and TIPS-DNP were dissolved in
chloroform (10−5 M) solution and were then exposed to
ambient light and air at room temperature (see Figure S5,
Supporting Information). The measured half-lives of TIPS-
DBP and TIPS-DNP are 33 and 200 h, respectively. The
improved stability is attributed to the additional Clar sextets
and TIPS ethynyl substituents to kinetically stabilize PAHs, as
well as the steric congestion at the central benzene ring which
is known to slow the decomposition rate of linear acenes.19
Our results also confirm that the stability of the “bistetracene”
molecules highly relies on its fusion modes.
In conclusion, we have described the synthesis of two TIPS-
functionalized nonplanar PAHs with different conjugation
lengths. A comparative study of the two compounds indicates
that the molecular geometry plays an important role on the
optical and electrochemical properties, stability, and device
performance. Our results also demonstrate that the fusion
mode has a significant effect on the stability of this class of
molecules. In addition, the two twisted PAHs easily produce
one-dimensional charge-transport systems with short C−C
contacts. The crystal of TIPS-DBP shows a hole mobility up to
0.17 cm2 V−1 s−1, while the crystal of TIPS-DNP shows a hole
mobility up to 0.74 cm2 V−1 s−1. We are currently exploring the
relationship between the molecular geometry and the stability
as well as for synthesis of even larger, expanded π-conjugated
PAHs with highly twisted conformations for organic devices.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.8b01810.
C
DOI: 10.1021/acs.orglett.8b01810
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Detailed synthesis and characterization, CV, DFT
Letter
G.; Mali, K. S.; Castiglioni, C.; De Feyter, S. D.; Tommasini, M.;
̈
llen, K. J. Am. Chem. Soc. 2016, 138, 4726.
(8) (a) Zhang, L.; Fonari, A.; Liu, Y.; Hoyt, A. L.; Lee, H.; Granger,
Narita, A.; Feng, X.; Mu
calcula-tions, X-ray crystallographic data, and NMR
spectra (PDF)
́
D.; Parkin, S.; Russell, T. P.; Anthony, J. E.; Bredas, J. − L.;
Coropceanu, V.; Briseno, A. L. J. Am. Chem. Soc. 2014, 136, 9248.
(b) Sbargoud, K.; Mamada, M.; Jousselin-Oba, T.; Takeda, Y.;
Tokito, S.; Yassar, A.; Marrot, J.; Frigoli, M. Chem. - Eur. J. 2017, 23,
5076. (c) Reus, C.; Lechner, M. P.; Schulze, M.; Lungerich, D.; Diner,
C.; Gruber, M.; Stryker, J. M.; Hampel, F.; Jux, N.; Tykwin-ski, R. R.
Chem. - Eur. J. 2016, 22, 9097. (d) Wang, Z.; Li, R.; Chen, Y.; Tan, Y.;
Accession Codes
CCDC 1840440−1840441 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Tu, Z.; Gao, X.; Dong, H.; Yi, Y.; Zhang, Y.; Hu, W.; Mu
Chen, L. J. Mater. Chem. C 2017, 5, 1308.
(9) Liu, J.; Ravat, P.; Wagner, M.; Baumgarten, M.; Feng, X.; Mu
len, K. Angew. Chem., Int. Ed. 2015, 54, 12442.
̈
llen, K.;
̈
l-
AUTHOR INFORMATION
■
(10) Ajayakumar, M. R.; Fu, Y.; Ma, J.; Hennersdorf, F.; Komber,
H.; Weigand, J. J.; Alfonsov, A.; Popov, A. A.; Berger, R.; Liu, J.;
Corresponding Author
*E-mail: zhl@mail.buct.edu.cn.
ORCID
Mullen, K.; Feng, X. J. Am. Chem. Soc. 2018, 140, 6240.
̈
(11) Dai, G.; Chang, J.; Luo, J.; Dong, S.; Aratani, N.; Zheng, B.;
Huang, K.; Yamada, H.; Chi, C. Angew. Chem., Int. Ed. 2016, 55, 2693.
(12) Gu, X.; Xu, X.; Li, H.; Liu, Z.; Miao, Q. J. Am. Chem. Soc. 2015,
137, 16203.
Lei Zhang: 0000-0002-0162-7222
Notes
(13) (a) Liu, J.; Narita, A.; Osella, S.; Zhang, W.; Schollmeyer, D.;
The authors declare no competing financial interest.
Beljonne, D.; Feng, X.; Mu
(b) Liu, J.; Osella, S.; Ma, J.; Berger, R.; Beljonne, D.; Schollmeyer,
D.; Feng, X.; Mullen, K. J. Am. Chem. Soc. 2016, 138, 8364.
̈
llen, K. J. Am. Chem. Soc. 2016, 138, 2602.
ACKNOWLEDGMENTS
■
̈
L.Z. thanks the National Science Foundation of China
(NSFC) (21672020) and Beijing Natural Science Foundation
(2182049). X.L. thanks the Distinguished Scientist Program at
BUCT (buctylkxj02). C.X. thanks China Postdoctoral Science
Foundation (2017M610744).
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