Diarylfluorenes-based π-stacked molecules: Synthesis, X-ray crystallography, and supramolecular light-emitting devices

Article abstract of DOI:10.1016/j.tet.2013.02.090

A series of intramolecular π-stacked molecules as new-concept supramolecular organic semiconductors have been designed by means of the ortho-substituted steric hindrance of diarylfluorenes and facile synthesized via the key step of BF₃·Et₂O-mediated Friedel-Crafts reaction of carbinols. Their intramolecular π-π stacking interactions were corroborated by the X-ray crystallography, NMR, as well as theoretical simulation. The supramolecular organic light-emitting devices exhibited an anomalous electroluminescence with a maximum luminance of ca. 1282 cd/m ², a luminous efficiency of 0.24 cd/A, and a turn-on voltage of 9 V. The π-stacked semiconductors are potential models of supramolecular semiconductors and optoelectronics.

Full text of DOI:10.1016/j.tet.2013.02.090

Tetrahedron 69 (2013) 6317e6322
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Diarylfluorenes-based
p-stacked molecules: synthesis, X-ray
crystallography, and supramolecular light-emitting devices
Yang Yang a, Jian-Feng Zhao a, Ran-Ran Liu a, Jie-Wei Li a, Ming-Dong Yi a, Guo-Hua Xie c,
,
a
a
a
c
Ling-Hai Xie a , Yong-Zheng Chang , Cheng-Rong Yin , Xin-Hui Zhou , Yi Zhao ,
*
Yan Qian a, Wei Huang a
,b,
*
a Center for Molecular Systems and Organic Devices (CMSOD), Key Laboratory for Organic Electronics & Information Displays (KLOEID) and
Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications (NUPT), Nanjing 210046, China
b Jiangsu-Singapore Joint Research Center for Organic/Bio-Electronics & Information Displays and Institute of Advanced Materials,
Nanjing University of Technology, Nanjing 211816, China
c State Key Laboratory on Integrated Optoelectronics, College of Electronics Science and Engineering, Jilin University, 2699 Qianjin Street,
Changchun 130012, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 August 2012
Received in revised form 17 February 2013
Accepted 26 February 2013
Available online 15 March 2013
A series of intramolecular p-stacked molecules as new-concept supramolecular organic semiconductors
have been designed by means of the ortho-substituted steric hindrance of diarylfluorenes and facile
synthesized via the key step of BF3$Et2O-mediated FriedeleCrafts reaction of carbinols. Their intra-
molecular
pep stacking interactions were corroborated by the X-ray crystallography, NMR, as well as
theoretical simulation. The supramolecular organic light-emitting devices exhibited an anomalous
electroluminescence with a maximum luminance of ca. 1282 cd/m2, a luminous efficiency of 0.24 cd/A,
Keywords:
and a turn-on voltage of 9 V. The
p
-stacked semiconductors are potential models of supramolecular
p-Stacks
semiconductors and optoelectronics.
Diarylfluorenes
Ó 2013 Published by Elsevier Ltd.
FriedeleCrafts reaction
Organic complex
Non-covalent bond
1. Introduction
1,8-diarylbiphenylene,11 naphthalenes,12 trietycephene,13 cyclo-
phane,14 and helicene,15 have been employed to construct intra-
Supramolecular interactions in biomolecules and materials have
been attracted much attention after the concept of supramolecular
chemistry proposed by Lehn,1 and many effects have been made to
explore the intermolecular supramolecular systems.2 For example,
they have been designed for the detector of explosive TNT,3 mo-
lecular tweezers as well as other molecular machines.4 In contrast,
intramolecular supramolecular molecules have been neglected in
the past two decades in despite of the discovery of DNA with the
molecular p-stacked systems. However, most of them have
complicated and laborious synthetic routes with the low yields
owing to the existence of the large strain forces. Examples were
rare investigated in the framework of organic electronics.
Designing and synthesizing intramolecular organic
p-stacked
molecules are the first step to explore the unique functionalities
of supramolecular organic semiconductors (SOSs) and devices.
In our previous works, we found that a diarylfluorene with the-
intramolecular
p
-stacked motifs.5 In fact, intramolecular
p-stacked
unique intramolecular
lography.16,17 In the articles, we ingeniously constructed
intramolecular -stacked molecules as SOS by designing the or-
tho-substituted steric hindrance of diarylfluorenes. A series of
intramolecular -stacked molecules had been successfully syn-
thesized via BF3$Et2O-catalyzed FriedeleCrafts reactions (BFR).
Their chemical structures and -stacked motifs had been un-
ambiguously confirmed by the X-ray crystallography, 1H NMR, 13
pep stacking motifs in the X-ray crystal-
motifs have exhibited unique conformational change for non-
volatile flash memories and other unique properties in the area of
p
organic electronics.6 Besides, intramolecular
p-stacked systems
have also been used as fluorescence-based sensors,7 probe8 and
offer an effective channel for triplet energy transfer and excimer
emissions.8,9 Up to date, several scaffolds, including norbornane,10
p
p
C
NMR spectra, and elemental analysis. There was an anomalous
excimer electroluminescence in the organic light-emitting
device with a configuration of ITO/MoOx(2 nm)/NPB(30 nm)/
DPBPFT(30 nm)/TPBi(10 nm)/Bebq2(30 nm)/LiF(1 nm)/Al.
* Corresponding authors. Tel./fax: þ86 25 8586 6396; e-mail addresses: iamlhxie@
njupt.edu.cn (L.-H. Xie), iamwhuang@njupt.edu.cn, iamdirector@fudan.edu.cn (W.
Huang).
0040-4020/$ e see front matter Ó 2013 Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.tet.2013.02.090

6318
Y. Yang et al. / Tetrahedron 69 (2013) 6317e6322
2. Results and discussion
The yield of reported DPTF (Scheme 2) was improved to 63% from
10% under HCl/AcOH.16 Chemical structures of the above products
2.1. Synthesis
were confirmed by 1H and 13C NMR, X-ray crystallography, and
elements analysis. In order to confirm the intramolecular p-stacked
Before we synthesized various intramolecular
p
-stacked
motifs in ortho-substituted diarylfluorenes, X-ray crystallography
and NMR spectra as well as theoretically calculation were con-
ducted to make comparison with the corresponding isomers.
3diarylfluorenes with the ortho-substituted steric hindrance effect,
we first examined the BFR of tertiary alcohols with the
3-phenylthiophene derivatives according to our previous works.17
We found that the reaction time highly impacted on the pro-
duction, as depicted in Scheme 1. The BFR of 3-phenylthiophenes
occurred first in the 2-position to give ortho-substituted diary-
2.2. Crystal structure
Crystal structure is the most direct visible tool for
p-stacked
motifs. Fortunately, single crystals of TP-2PF (Fig. 1a, b) and DPBPFT
(Fig. 1c, d) were obtained from a CH2Cl2/alcohol solution. TP-2PF
lfluorenes (TP-2PF) with intramolecular
of 60% at reaction time of w2 h.
p-stacked motifs at a yield
Scheme 1. Kinetic and thermodynamic-controlled processes of BF3$Et2O-mediated FriedeleCrafts reaction (BFR).
Interestingly, a counterpart isomer (TP-5PF) with the 5-position
substitution of 3-phenylthiophenes was obtained when reaction
time was extended to 12 h and the conversion yield of 96%. It was
reasonable to explain that the former were kinetic-controlled
products while the latter were thermodynamic-controlled prod-
ucts. It is expected that electrophilic substitution occurs initially at
2-postion of thiophene because the 9-phenylfluorenyl moieties are
an activating group. It was known that the FriedeleCraft reactions
are reversible process. The product of TP-2PF is congested molecule
with higher steric hindrance and strain force than the isomer
TP-5PF that favored thermodynamic reaction control. When the
reaction time elongates, TP-5PF takes prevalence over less favor-
able TP-2PF by chemical equilibration. This similar process also has
been observed in another BFR of PTFOH with SITF to give the
SITFe2PTF and SITFe5PTF with the yield of 59% at the reaction time
of 2 h and 93% at the reaction time of 12 h, respectively. The explain
can be also supported by the electrophilic substituted bromination
of 3-phenylthiophene according to the literature.18 Furthermore,
time-dependent FriedeleCrafts reactions under the catalyzed BF3
and boron tris(trifluoromethanesu1fonate) were ever observed by
Olah et al..19 However, it does still not make sure the reaction
mechanism suffer from the cationic process in consideration of the
formation byproduct of dehydroxy 9-phenylfluorene according to
our previous observation.17
Scheme 2. The syntheses of the intramolecular
phenylfluorenyl tertiary alcohol (PFOH) with different thiophene substrates with the
ortho-substituted steric hindrance effect.
p-stacked molecules via the BFR of
and DPBPFT showed typical congested molecules with obviously
intramolecular
p-stacked motifs between fluoren-9-yl rings and
After the above analysis, several intramolecular
p-stacked dia-
phenyl groups at the 3-position of thiophene cores. The distance
between these two kinds of face-to-face stacked groups (Fig. 1b) in
TP-2PF was in the range of 3.118e4.378 A, which was a nonparallel
stacked mode owing to the steric hindrance effect. Furthermore,
fluoren-9-yl rings exhibited an obvious bend curve owing to the
same effect, which offered an important tool to control the curve of
rylfluorenes were designed and synthesized by BFR of tertiary
alcohols with different electron-rich arylthiophenes, as shown in
Scheme 2. BFR of 3-phenylthiophene and 3,4-diphenylthiophene
with PFOH of about 2 equiv at the same condition gave the prod-
ucts PBPFT and DPBPFT with the yields of 65% and 85%, respectively.
ꢀ

Y. Yang et al. / Tetrahedron 69 (2013) 6317e6322
6319
p-stacked motifs, its NMR exhibits the typical aromatic chemical
shift zone among 7.00e7.50 ppm at the corresponding protons of a,
b, and c of thiopheneephenyls, which is reasonable according to
the literature.21 With respect to TP-5PF, the doublets and triplets of
protons a, b, and c exhibit upfield shift to 6.38, 6.80, and 6.91 ppm
for TP-2PF. With the increasing intensity of
pep stacking in-
teractions, regular upfield shifts are also observed in PBPFT with the
a, b, c peaks of 6.30, 6.72, and 6.84 ppm and DPBPFT with 5.84, 6.35,
and 6.50 ppm, respectively. Undoubtedly, these upfield shift
phenomena could be ascribed to electromagnetic shielding effect
from the intramolecular rotation constrained and mutually stack-
ing interactions between thiopheneephenyl and fluorenyl groups.
2.4. Photophysical properties
To further explore their optoelectronic properties, UVevis
absorption and photoluminescence (PL) spectra of TP-5PF, TP-2PF,
PBPFT, and DPBPFT have been performed. As shown in Fig. 3a, it
presents similar absorbance profiles above all, where the two dis-
tinct feature absorption bands were located at around 265 and
310 nm in their diluted solutions.22 A sharp peak at 312 nm was
Fig. 1. Single crystal X-ray structures of TP-2PF (a, b) and DPBPFT (c, d) with ORTEP
drawing and the distances of intramolecular -stacked motifs.
p
(a)
1.0
aromatics with different electronic structures. DPBPFT as a strained
molecules exhibited the unique gear-shaped configuration with the
0.8
ꢀ
p-stacked distance of 3.418, 3.553, and 3.787 A (Fig. 1d). Other
DPBPFT
modeling diarylfluorene-based intramolecular
cules without crystal structures have been conducted to simulate
p-stacked mole-
PBPFT
0.6
TP-2PF
TP-5PF
the optimized molecular configurations as shown in Table S1. They
0.4
also exhibited corresponding intramolecular
teractions. It should be noted that they are antiparallel trapezium-
shaped -stacked systems. The optimized molecular geometries
pep stacking in-
0.2
p
0.0
also had been calculated by theoretical simulation (Table S1). The
250
300
350
400
450
distances of arylearyl plane were confirmed to be in the range of
3.4e3.8 A, which offered new channel for the charge transfer and
energy transfer.
Wavelength (nm)
ꢀ
(b)
0.08
0.06
0.04
0.02
0.00
1.0
2.3. 1H NMR
0.8
0.6
0.4
0.2
0.0
Chemical shifts of the protons of reaction molecules are highly
400 420 440 460 480
Wavelength(nm)
shielded in the NMR spectrum owing to intramolecular p-stacked
interactions.20 Fig. 2 shows the 1H NMR spectra of these com-
pounds characterized in CDCl3. For TP-5PF without intramolecular
DPBPFT (290 nm)
PBPFT (290 nm)
TP-2PF (300 nm)
TP-5PF (305 nm)
300
360
420
480
Wavelength(nm)
(c)
Fig. 2. The aromatic region of 1H NMR (400 MHz, CDCl3) spectra of TP-5PF, TP-2PF,
PBPFT, and DPBPFT with part well-defined resonance assignments (signals marked by
a, b, c, and m, etc. ascribe to corresponding protons; signals on vertical top of the arrow
were from residual CHCl3 in CDCl3).
Fig. 3. The normalized UVevis absorption (a) and PL (b) of TP-5PF, TP-2PF, PBPFT, and
DPBPFT in chloroform (10ꢀ6 mol/L) (inset one is a magnified image of PL spectra.).
(c) Their original photoluminescence in chloroform (10ꢀ6 mol/L) (inset one is magni-
fied image.).

6320
Y. Yang et al. / Tetrahedron 69 (2013) 6317e6322
observed in DPBPFT that has 5 nm red-shift when making
comparison with that of PBPFT at 307 nm. Similarly, the kinetic
controlled TP-2PF offered another 4 nm red-shift in its low-energy
absorption peak at 309 nm when compared with 305 nm for
TP-5PF. All the UVevis spectra exhibited concentration-dependent
characteristics, which might be due to restricted motion under the
high concentration, resulting in a new tailed absorption long-
wavelength band (See S8b). The PL profile of PBPFT (blue dot
line) has two emission bands, with a unique sharp peak at 312 nm.
DPBPFT (red square line) exhibited gradually ca. 4 nm red-shift
from 332 nm (PBPFT) to 336 nm as an additional phenyl sub-
stitution at 5-position of thiophene moiety. Furthermore, the
thermodynamic controlled isomer TP-5PF lead to a 3 nm red-shift
as 331 nm with a longer tailed band 360e400 nm, compared
with TP-2PF (328 nm, triangle pink line). Noted that, a broad band
between ca. 420 and 480 nm of DPBPFT was observed (inset of
Fig. 3b), considered as excimer (no absorbance at longer wave-
length in Fig. 3a), which provide robust evidence of the existence of
variable-temperature and magnetic fields for supramolecular spin-
tronics. DPBPFT-based device B displayed blue color with Commission
Internationale de l’Eclairage (CIE) coordinates of (0.21, 0.16) under the
voltage of 15 V. Compared with device A, device B exhibited a maxi-
mum luminance of ca. 1282 cd/m2 with a luminous efficiency of
0.24 cd/A and a turn-on voltage of 9 V.
3. Conclusion
We have observed thermodynamic-controlled and kinetic-
controlled processes in the BF3$Et2O-catalyzed FriedeleCrafts
reaction (BFR) of tertiary alcohols.
A series of complex
diarylfluorenes-based intramolecular -stacked molecules as the
p
SOS models have been synthesized by means of the ortho-
substituted steric hindrance design via the key step of the BFR at
the yields of 60e85%. Intramolecular
p-stacked motifs in these
organic complexes result in an excimer emission in the concen-
trated solution. Supramolecular light-emitting devices (SLEDs)
have been fabricated with unique electroluminescent spectra,
brightness of 1282 cd/m2 and current efficiency of 0.24 cd/A.
Organic complexes and supramolecular devices offer the unique
models to investigate structureefunction relationship for organic
electronics, optoelectronics, mechatronics, and spintronics.
the stronger intramolecular p-stacks in DPBPFT than PBPFT, TP-2PF,
and TP-5PF from the normalized and original PL spectra of these
compounds.
2.5. Device
4. Experimental section
4.1. General information
Multilayer supramolecular organic light-emitting diodes
(SOLEDs) were fabricated to investigate the electroluminescence of
diarylfluorene-based intramolecular
p-stacked molecules with the
device configurations of (A): ITO/MoOx(2 nm)/NPB(30 nm)/
DPBPFT(30 nm)/TPBi(40 nm)/LiF(1 nm)/Al; and (B): ITO/MoOx(2 nm)/
NPB(30 nm)/DPBPFT(30 nm)/TPBi(10 nm)/Bebq2(30 nm)/LiF(1 nm)/
Al. DPBPFT (See SD). The current densityevoltage and luminan-
ceevoltage characteristics for devices A and B were plotted in Fig. 4a,
together with their EL spectra of DPBPFT (Fig. 4b, c). DPBPFT-based
devices showed two distinctly major peaks at ca. 435 nm for A (ca.
442 nm for B) and ca. 650 nm for A (ca. 650 nm for B) under different
current density. The first peaks originated from the excimer emission
4.1.1. Chemicals. Magnesium turnings, thiophene, and fluorenone
were used without further purification. 3-Phenylthiophene, 2,5-
dibromo-3-phenylthiophene, 3,4-diphenylthiophene, 9-phenyl-
fluoren-9-ol,24 and 9-(3-phenylthiophen-2-yl)-fluoren-9-ol, were
prepared as previously reported.16 THF and diethyl ether were
dried over sodium benzophenone ketyl anion radical and distilled
under a dry nitrogen atmosphere immediately prior to use. All
reactions involving organometallic reagents were carried out un-
der nitrogen.
of the intramolecular
to that of -stacked PVK likely due to the electromers or triplet exciton
according to the literature.6,23 These EL results indicated the existence
of the intramolecular -stacked motifs, offering a well-defined model
p-stacked motifs. Thesecond peaks were similar
p
4.1.2. Characterization. 1H and 13C NMR in CDCl3 was recorded at
400 MHz. Chemical shifts were reported in parts per million (d), and
p
the signals were designated as follows: s (singlet), d (doublet), t
(triplet), and m (multiplet). For the MALDIeTOF MS spectra, the
spectra were recorded in reflective mode, and no substrate was
to investigate the origin of ca. 620e680 nm under the conditions of
used. Absorption spectra (1
and emission spectra (1 M in CHCl3) were recorded upon excita-
m
M in CHCl3) were measured at 25 ꢁC,
(a)
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
A Current Density
B Current Density
A Luminance
m
tion at the absorption maxima in the degassed CHCl3 solvent after
saturating with argon. Differential scanning calorimetry (DSC)
analyses were performed under N2, the samples were ramped at
10 ꢁC/min from 30 ꢁC to 360 ꢁC, then quenched at 10 ꢁC/min to
room temperature. Thermogravimetric analyses (TGA) were per-
formed conducted under a heating rate of 10 ꢁC/min and a nitrogen
flowing rate of 20 cm3/min. Geometry optimizations and electronic
analysis were carried out at the B97-D25,26 including Rꢀ6 project
and TZVP27,28 basis sets with polarization functions (except for
hydrogen).
B Luminance
-100
-100
9
10 11 12 13 14 15 16 17 18
Voltage (V)
(b)
(c)
0.035
0.035
A
B
0.030
0.025
0.020
0.015
0.010
0.005
0.000
0.030
2
100 mA/cm
2
2
2
2
100 mA/cm
200 mA/cm
300 mA/cm
400 mA/cm
4.2. Data for X-ray structure analysis
0.025
0.020
0.015
0.010
0.005
0.000
2
2
2
200 mA/cm
300 mA/cm
400 mA/cm
Crystallographic data for TP-2PF and DPBPFT were saved as the
files of CCDC 817167.cif and CCDC 817168.cif, respectively. Data
were collected at room temperature on a detector with graphite-
ꢀ
monochromated Mo K
a
radiation (
l
¼0.71073 A). The absorption
300
400
500
600
700
800
300
400
500
600
700
800
correction was applied by integration based on the crystal shape.
Structures were solved by direct methods and refined against F2
with the full-matrix and least-squares methods. Hydrogen atoms
were found by difference Fourier syntheses and were refined.
Wavelength (nm)
Wavelength(nm)
Fig. 4. Current densityevoltageeluminance (a) and EL spectra of the OLED devices A
(b) and B (c) made by DPBPFT.

Y. Yang et al. / Tetrahedron 69 (2013) 6317e6322
6321
4.2.1. Crystal data for TP-2PF. C29H20S, M¼400.53, T¼273(2) K,
the remaining crude product was purified by silicon gel chroma-
tography (petroleum etheredichloromethane) to yield the final
products.
ꢀ
ꢀ
monoclinic, C2/c, Z¼8, a¼27.159(4) A, b¼7.6566(12) A,
3
ꢀ
ꢁ
ꢀ
c¼20.530(3) A,
a
¼90ꢁ,
b
¼100.852(3)ꢁ,
g
¼90 , V¼4192.9(12) A ,
F(000)¼1680, rcalcd¼1.269 Mg mꢀ3
,
m
(Mo K
a
)¼0.168 mmꢀ1
,
2
qmax¼52ꢁ, reflections collected/unique 10,633/4091 (Rint¼0.0564),
4.4.1. 3-Phenyl-2-(9-phenyl-fluoren-9-yl)thiophene (TP-2PF). This
compound was prepared following the above-mentioned general
procedures using 3-phenylthiophene (1.60 g, 10 mmol, 1 equiv),
9-phenyl-fluoren-9-ol (2.84 g, 11 mmol, 1.1 equiv), and BF3$Et2O
(1.5 mL, 12 mmol, 1.2 equiv). After 2 h of reaction, 2.40 g TP-2PþF was
obtained with a 60% yield. Mp: 127 ꢁC. GC/MS (m/z): 400 (M ). 1H
parameters 271, Final R1¼0.0402 (I>2
s
(I)), wR2¼0.1075 (I>2
s (I)),
R1¼0.0564 (all data), wR2¼0.1125 (all data), S¼0.948 (all data).
4.2.2. Crystal data for DPBPFT. C54H36S, M¼716.93, T¼291(2) K,
ꢀ
ꢀ
3
ꢀ
monoclinic, P21/c, Z¼4, a¼12.007(10) A, bꢁ¼13.674(11) A,
ꢀ
c¼26.541(17) A,
a
¼90.00ꢁ,
b
¼116.90(3)ꢁ,
g
¼90.00 , V¼3886(5) A ,
NMR (400 MHz, CDCl3, ppm)
d
: 6.38e6.40 (d, J¼7.7, 2H), 6.78e6.82
F(000)¼1504, rcalcd¼1.225 Mg mꢀ3
,
m
(Mo K
a
)¼0.121 mmꢀ1
,
(m, 3H), 6.90e6.93 (t, J¼7.2, 1H), 7.09e7.12 (t, J¼7.5, 2H), 7.14e7.15
(d, J¼5.2, 1H), 7.19e7.21 (m, 4H), 7.23 (s, 1H), 7.35e7.37 (d, J¼7.7,
2H), 7.40e7.43 (m, 2H), 7.48e7.50 (d, J¼7.5, 2H). 13C NMR (100 MHz,
2
qmax¼49.98ꢁ,
reflections
collected/unique
18,874/6856
(Rint¼0.1182), parameters 496, Final R1¼0.0569 (I>2
s
(I)),
wR2¼0.0979 (I>2
s
(I)), R1¼0.1430 (all data), wR2¼0.1219 (all data),
CDCl3, ppm) d: 150.2, 145.9, 143.4, 140.28, 140.0, 137.1, 131.6, 128.9,
S¼0.827 (all data). Crystal data for CCDC 817167 and 817168
contained the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_-
request/cif.
128.0, 127.9, 127.5, 127.2, 126.9, 126.6, 125.9, 122.1, 119.9, 61.9. Anal.
Calcd for: C29H20S: C, 86.96; H, 5.03; Found: C, 86.99; H, 5.22.
4.4.2. 3-Phenyl-5-(9-phenylfluoren-9-yl)thiophene
(TP-5PF). This
compound was prepared following the reacting condition above
using TP-2PF (0.40 g, 1.0 mmol, 1 equiv) and BF3$Et2O (0.15 mL,
1.2 mmol, 1.2 equiv). After 12 h of reaction, 0.38 g TP-5PF was ob-
tained with the yield of 96%. GC/MS (m/z): 400 (Mþ). Mp: 146 ꢁC. 1H
4.3. Device fabrication and characterization
All the devices were fabricated onto pre-patterned indiumetin
NMR (400 MHz, CDCl3, ppm) d: 7.18 (s, 1H), 7.21e7.24 (m, 3H),
oxide (ITO) with a sheet resistance of 10
U
/sq. The substrates were
7.27e7.30 (m, 4H), 7.32e7.35 (m, 4H) 7.38e7.42 (t, J¼7.4, 2H),
sonicated sequentially with detergent, 2-propanol, acetone, and de-
ionized water, then dried in an oven, and finally treated in an
ultravioleteozone chamber. After the organic deposition, 100 nm-
thick Al was covered directly on the organic layers to serve as
cathode. The cathode area defines an active device area of 2ꢂ2 mm2
through a shadow mask. EQE was measured in an integrated sphere,
following the method mentioned in the literature.8,10,29 All mea-
surements were carried out in ambient environment without en-
capsulation. Two potential undoped devices (A, B) of DPBPFT were
fabricated with multilayer configurations. Configuration of device A
ITO/MoOx(2 nm)/NPB(30 nm)/DPBPFT (30 nm)/TPBi(40 nm)/LiF
(1 nm)/Al; Bebq2 was added in device B. Configuration of device
B ITO/MoOx(2 nm)/NPB(30 nm)/DPBPFT(30 nm)/TPBi(10 nm)/
Bebq2(30 nm)/LiF(1 nm)/Al. All devices had the same total thickness
of organic films (100 nm). In devices A and B, DPBPFT served as the
blue light emitter, a thin-layer MoOx (2 nm) and LiF (1 nm) acted
as anode and cathode buffer layers, and NPB acted as the hole-
injecting and transporting layers. Bebq2 and TPBi were used as
the electron-transporting layer and hole/exciton blocking layer.
NPB represents N,N0-diphenyl-N,N0-bis(1,10-biphenyl)-4,40-diamine,
TPBi represents 1,3,5-tris-(N-phenylbenzi-midazole-2-yl)-benzene,
and Bebq2 represents bis(10-hydroxybenzo[h]qinolinato) beryl-
lium. Fig. 4 compares the luminance (L)evoltage (V)ecurrent den-
sity (J) characteristics, CEeluminanceepower efficiency (PE)
characteristics, normalized EL spectra, and external quantum effi-
ciencies of devices A and B, respectively.
7.47e7.49 (d, J¼7.9, 2H), 7.55e7.57 (d, J¼7.6, 2H), 7.78e7.79 (d,
J¼7.5, 2H). 13C NMR (100 MHz, CDCl3, ppm)
d: 150.9, 150.3, 145.2,
141.5, 139.9, 135.9, 128.7, 128.3, 128.0, 127.8, 127.7, 127.1, 127.1, 126.3,
126.2, 125.7, 120.3, 119.3, 62.4. Anal. Calcd for: C29H20S: C, 86.96; H,
5.03; Found: C, 86.80; H, 5.18.
4.4.3. 3-Phenyl-2,5-bis(9-phenylfluoren-9-yl)thiophene (PBPFT). This
compound was synthesized according to the general procedures
above using 3-phenylthiophene (0.322 g, 2 mmol, 1 equiv), 9-
phenyl-fluoren-9-ol (1.14 g, 4.4 mmol, 2.2 equiv), and BF3$Et2O
(0.6 mL, 4.8 mmol, 2.4 equiv). After 12 h of reaction, starting material
was no longer detectable by TLC, the yield of PBPFT was 65%. Mp:
145 ꢁC. 1H NMR (400 MHz, CDCl3, ppm)
d
: 6.29e6.31 (d, J¼7.7, 2H),
6.45 (s, 1H), 6.70e6.74 (t, J¼7.6, 2H), 6.82e6.86 (t, J¼7.4, 1H),
7.05e7.09 (t, J¼7.5, 2H), 7.13e7.14 (m, 3H), 7.16 (s, 1H), 7.18 (s, 1H),
7.20e7.21 (m, 5H), 7.27e7.29 (d, J¼7.5, 2H), 7.31e7.33 (m, 4H),
7.33e7.38 (t, J¼7.5, 2H) 7.46e7.50 (t, J¼8.3, 4H), 7.74e7.76 (d, J¼7.5,
2H). 13C NMR (100 MHz, CDCl3, ppm)
d: 150.7, 150.1, 146.1, 145.6,
144.9, 142.5, 139.9, 139.8, 138.9, 137.1, 130.8, 128.8, 128.1, 127.9, 127.8,
127.7, 127.5, 127.4, 127.2, 127.1, 126.9, 126.7, 126.6, 126.3, 125.7, 120.2,
119.8, 62.2, 62.1. Anal. Calcd for: C48H32S: C, 89.96; H, 5.03; Found: C,
89.90; H, 5.14.
4.4.4. 3,4-Diphenyl-2,5-bis(9-phenylfluoren-9-yl)thiophene (DPBPFT).
This compound was prepared following the general procedures
above using 3,4-diphenylthiophene (0.236 g, 1.0 mmol 1 equiv), 9-
phenyl-fluoren-9-ol (0.57 g, 2.2 mmol, 2.2 equiv), and BF3$Et2O
(0.30 mL, 2.4 mmol, 2.4 equiv). After 12 h of reaction, 0.61 g DPBPFT
4.4. General procedure for FriedeleCrafts reaction of 9-
phenyl-fluoren-9-ol (PFOH) and 9-(3-phenylthiophen-2-yl)-
fluoren-9-ol (PTFOH) with various aryl substrates
was obtained with 85% yield. 1H NMR (400 MHz, CDCl3, ppm)
d:
5.84e5.86 (d, J¼7.0, 4H), 6.33e6.37 (t, 4H), 6.48e6.52 (t, 2H),
7.09e7.11 (d, J¼1.5, 2H), 7.12e7.13 (t, J¼1.7, 4H), 7.14e7.144 (d, J¼1.3,
2H), 7.16e7.19 (m, 6H), 7.33 (s, 2H), 7.35e7.36 (d, J¼1.8, 2H)
7.418e7.422 (d, J¼1.7, 2H), 7.44 (s, 4H), 7.45e7.46 (d, J¼2.0, 2H). 13C
A solution of BF3$Et2O in appropriate dichloromethane (15 mL)
was added dropwise to the mixed solution of tertiary alcohols and
aryl substrates in dichloromethane of appropriate amount
(60 mL). The reaction mixture was stirred at room temperature
(25 ꢁC) until starting material was no longer detectable by TLC
(2e12 h). Ethanol (10 mL) and water (30 mL) were successively
added to quench the reaction. Different phases were then sepa-
rated and the aqueous phase was extracted with dichloro-
methane. The combined dichloromethane layers were washed
and dried with anhydrous MgSO4. After removal of the solvent,
NMR (100 MHz, CDCl3, ppm) d: 150.5, 145.7, 141.7, 140.5, 140.0, 135.9,
130.1, 128.0, 127.8, 127.1, 127.1, 127.1, 126.5, 125.8, 125.0, 119.8,
62.1. Anal. Calcd for: C54H36S: C, 90.47; H, 5.06; Found: C, 90.41; H,
5.12.
4.4.5. 20-(9-(4-Phenylthiophen-2-yl)-fluoren-9-yl)spiro[fluorene-
9,80-indeno[2,1-b]thiophene] (SITFe5PTF). This compound was
synthesized according to the reacting condition as TP-2PF using

6322
Y. Yang et al. / Tetrahedron 69 (2013) 6317e6322
20-(9-(3-phenylthiophen-2-yl)-fluoren-9-yl)spiro[fluorene-9,80-
indeno[2,1-b]thiophene] (SITFe2PTF) (0.645 g, 1.0 mmol, 1 equiv)
and BF3$Et2O (0.15 mL, 1.2 mmol, 1.2 equiv). After 12 h of reaction,
starting material was no longer detectable by TLC, 0.60 g SITFe5PTF
was obtained with a 93% yield. Mp: 308 ꢁC. 1H NMR (400 MHz,
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CDCl3, ppm)
d
: 6.55e6.57 (d, J¼7.6, 1H), 6.80e6.82 (d, J¼7.5, 2H),
6.90e6.94 (t, J¼7.8, 1H), 7.09e7.13 (t, 2H), 7.21e7.22 (m, 2H),
7.23e7.25 (m, 2H), 7.31e7.35 (m, 7H), 7.39e7.43 (t, 2H), 7.45e7.46
(m, 3H), 7.70e7.72 (d, J¼7.6, 2H), 7.74e7.76 (d, J¼7.5, 4H) 13C NMR
(100 MHz, CDCl3, ppm) d: 154.0, 152.3, 150.1, 149.8, 148.2, 147.5,
146.5, 141.5, 141.4, 139.4, 139.1, 135.8, 128.7, 128.4, 128.0, 127.8, 127.8,
127.4, 127.1, 126.3, 126.0, 125.4, 125.4, 123.9, 123.3, 120.3, 120.0,
119.5, 119.2, 117.8, 64.3, 59.9. Anal. Calcd for: C46H28S2: C, 85.68; H,
4.38; Found: C, 85.70; H, 4.35.
Acknowledgements
The authors acknowledge financial support from National Basic
Research Program of China (973 Program, 2009CB930601), National
Natural Science Foundation of China (21274064, BZ2010043,
20974046, 20774043, 51173081, 50428303, 61136003, 21144004,
51273092, 61106058), the Program for New Century Excellent Talents
in University (NCET-11-0992), Natural Science Foundation of Jiangsu
Province (BK2011761, BK2008053, BK2009025, 10KJB510013).
€
€
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Supplementary data
Copies of 1H NMR and 13C NMR for all new compounds, as well
as X-ray and TGA data for TP-2PF and DPBPFT; PL spectra, DSC, and
normalized EL (for DPBPFT) data, as well as geometry optimized
structures for all new compounds. Supplementary data related to
this article can be found at http://dx.doi.org/10.1016/j.tet.2013.
02.090.
17. Xie, L. H.; Hou, X. Y.; Hua, Y. R.; Tang, C.; Liu, F.; Fan, Q. L.; Huang, W. Org. Lett.
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