Synthesis and characterization of fluorene and carbazole dithienosilole derivatives for potential applications in organic light-emitting diodes

Article abstract of DOI:10.1016/j.tet.2012.08.056

Several fluorene or carbazole-based dithienosiloles (DTSs) have been synthesized and their thermal, photophysical, and electrochemical properties have been systematically investigated. These compounds show high thermal stability with glass transition temp

Full text of DOI:10.1016/j.tet.2012.08.056

Tetrahedron 68 (2012) 9278e9283
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and characterization of fluorene and carbazole dithienosilole
derivatives for potential applications in organic light-emitting diodes
,
Hyoungkeun Park a, Yingli Rao b, Maria Varlan b, Jinho Kim a, Soo-Byung Ko b, Suning Wang b
*
,
,
Youngjin Kang a
*
a Division of Science Education & Department of Chemistry, Kangwon National University, Chuncheon 200-701, Republic of Korea
b Department of Chemistry, Queen’s University, Kingston, Ontario, K7L 3N6, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 17 July 2012
Received in revised form 17 August 2012
Accepted 17 August 2012
Available online 1 September 2012
Several fluorene or carbazole-based dithienosiloles (DTSs) have been synthesized and their thermal,
photophysical, and electrochemical properties have been systematically investigated. These compounds
show high thermal stability with glass transition temperature above 110 ꢀC as well as decomposition
temperatures at w400 ꢀC. Intense green emission is observed in the spectral region of 500e510 nm for
all compounds (FPL¼0.31e0.80), that is, attributed to both the 5,50-substituents of the DTS ring and DTS-
based
pep transition. Based on the emission spectra at 77 K, the triplet energy for these compounds
*
Keywords:
Dithiensilole
Thermal properties
Photophysical properties
Electrochemical behaviors
Organic light-emitting diodes
was calculated to be within 2.1e2.2 eV, indicating that they may be used as host materials for red
emitters in organic light-emitting diodes (OLEDs). All compounds exhibit reversible oxidation and
possess low-lying LUMO energies, owing to the conjugated fluorene/carbazole substituents on the DTS.
This along with the high thermal/electrochemical stabilities and high fluorescent quantum efficiencies
makes the new DTSs compounds promising candidates for use in OLEDs as emitters, host and electron-
transporting materials.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
5,50-position of the DTS main chain can improve the efficiency of
the materials in organic electronics and photovoltaics.4 Such
Five-membered and dithiophene-fused silacyclopentadienes
and dithienosiloles (DTSs) have recently attracted intense research
interest for applications in organic electronics because of their
unique photophysical properties.1 These compounds possess low-
lying LUMO energy levels, compared to other cyclopentadiene an-
alogues. In addition they exhibit highly efficient electron-
transporting properties in organic light-emitting diodes (OLEDs),
compared to the standard electron transport material Alq3 (q¼8-
hydroxyquinolinato).2 DTSs containing a 2,20-bithiophene bridged
functional groups play a key role in enhancing thermal stability,
film uniformity, and quantum efficiency of copolymers. Both
fluorene and carbazole units have interesting electronic proper-
ties, however, synthetic approach and photophysical properties
of fluorene or carbazole-based DTS derivatives with small mo-
lecular weight have never been reported.5 We have recently re-
ported the synthesis and photophysical study of a series of 5,50-
naphthyl functionalized DTS derivatives.2a The introduction of
the naphthyl segment into the DTS core allows these molecules
to have high thermal stability, low-lying LUMO energy levels,
high quantum efficiency so that they can be used as efficient
electron-transporting materials in OLEDs. It has been found that
the photophysical properties and electronic structures of these
DTS derivatives are strongly dependent on the nature of 5,50-
substituents. It was therefore deduced that the introduction of
a carbazole or fluorene functional group within a DTS unit would
be an ideal module in developing new materials for use in or-
ganic electronics. With these considerations, we report the
syntheses of symmetrical fluorene and carbazole functional
group functionalized DTS derivatives at the 5-position of the
ring, as well as their photophysical, thermal, and electrochemical
properties.
by a silicon atom at 3,30-position have a greater
p-conjugation
within the bithiophene moiety due to the greater coplanarity
reinforced by the silicon bridge. Nonetheless, studies on photo-
physical properties and potential applications of DTS-based small
molecules are scarce due to the synthetic limitations, as compared
to those of DTS-based polymers.3
It has been demonstrated previously that the introduction of
fluorene and/or carbazole copolymer functional groups into the
* Corresponding authors. Tel.: þ82 33 250 6737; fax: þ82 33 242 9598 (Y.K.); tel.:
þ1 613 533 6941; fax: þ1 613 533 6669 (S.W.); e-mail addresses: suning.wang@
chem.queensu.ca (S. Wang), kangy@kangwon.ac.kr (Y. Kang).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.08.056

H. Park et al. / Tetrahedron 68 (2012) 9278e9283
9279
2. Results and discussion
structures and composition of compounds 1e4 have been con-
firmed by NMR spectroscopy, mass spectrometry, and elemental
analysis.
2.1. Synthesis and thermal properties
The most widely adopted methodology for device fabrication in
the OLED industry is the vacuum deposition technique under high
temperature. It is therefore important that the materials used in
The synthetic methodology for the fluorene or carbazole-
functionalized DTS derivatives, 1e4, is shown in Scheme 1. Vari-
Scheme 1. Reagents and conditions: Method A: n-BuLi, ZnCl2(tmeda), Pd(PPh3)4, reflux (THF), 12e24 h, yield:10e20%; Method B: n-BuLi, ClSnMe3, Pd(PPh3)2Cl2/LiCl, reflux (THF),
12e24 h, yield: 30e55%; Method C: n-BuLi, InCl3, Pd(dppf)Cl2, reflux (THF), 12e24 h, yield: 50e60%.
ous cross-coupling reaction methods were employed to achieve
efficient and optimized reaction conditions for compounds 1e4.
Breaking of the SieC (thiophene) bond occurs readily in the pres-
ence of a base according to our recent findings. Cross-coupling
methods that do not involve the use of a base, such as Stille6 and
Negishi7 coupling reactions were therefore used to minimize this
bond-breaking problem. For examples, products 1e4 were ob-
tained in 10e20% yield from the reaction of 5,50-diiododithienosi-
lole with corresponding ZnAr2 (2.5 equiv) in the presence of
2e5 mol % Pd(PPh3)4 (Method A), while the better results were
obtained with SnAr2 (2.5 equiv) in the presence of 2e5 mol % of
Pd(PPh3)2Cl2 and LiCl (3.0 equiv) in THF (70 ꢀC, 12e24 h), producing
compounds 1e4 in 30e55% yield (Method B). These coupling re-
actions, however, produced compounds 1e4 in poor to moderate
yields. As an alternative method, a new cross-coupling synthetic
mass production of OLEDs have high thermal stability.8 In order to
investigate the thermal stability of all complexes, thermogravi-
metric analysis (TGA) and DSC (differential scanning calorimetry)
data were recorded for all compounds. The representative results of
1 and 3 are shown in Figs. 1 and 2. All compounds have shown to be
highly stable up to 350 ꢀC without any degradation under N2 at-
mosphere. Weight loss for compound 3 caused by escaping of
solvent molecules from the solid was observed at 200 ꢀC, but
compound 3 is stable up to 350 ꢀC. The 5% weight loss of 1, 2, 3, and
4 is at 405, 412, 433, and 447 ꢀC, respectively. These results indicate
that compounds 2 and 4, bearing either two phenyl or carbazole
units at 3- and 5-position of DTS ring, respectively, have better
thermal stability than the other two analogues. Compound 4 has
relatively larger molecular weight, which may be responsible for
the highest decomposition temperature among four compounds.
Fig. 1. TGA (left) and DSC (right) data of 1 and 3.
process established by our group has been adopted using indium
reagents as a nucleophilic agent. Compounds 1e4 have been ob-
tained in satisfactory yields (50e60%) using corresponding indium
nucleophiles and Pd(dppf)Cl2 as a catalyst for (Method C). The re-
sults are summarized in Scheme 1. All four compounds are stable in
air and soluble in common organic solvents, including hexane. The
In order for a molecule to be suitable for use in OLEDs, it should
have high glass transition (Tg) temperature with a Tg value greater
than 110 ꢀC, to ensure the morphological stability of the material.9 All
the compounds show glass transitions in both the first and second
heating/cooling cycles as demonstrated in Fig. 1. The glass transition
temperatures for all four compounds follow the order of 3>1>4>2.

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H. Park et al. / Tetrahedron 68 (2012) 9278e9283
(b)
(a)
Fig. 2. (a) Absorption and emission spectra of 1e4 in CH2Cl2 at 298 K. (b) Emission spectra of 1e4 at 77 K.
Compounds 1, 3, and 4 have a glass transition at either near 110 ꢀC or
higher, while compound 2 exhibits much lower glass transition
temperature (86 ꢀC). The Tg values observed for all compounds are
considerably higher than those of other DTS-based small molecules2a
or polymers.4b,10 reported previously. These observations strongly
indicate that the fluorene orcarbazole functional groups enhance the
thermal stability of the DTS segments than any other derivatives.
and normalized fluorescence emission spectra of compounds 1e4
in dilute CH2Cl2 measured at 298 and 77 K are shown in Fig. 2.
The absorption spectra of all compounds are similar in solution
in the region of 390e500 nm. Compounds 1e4 display a distinct
and strong band at 430 nm, characteristic of 5,50-substituted DTSs
as illustrated in Fig. 2. These characteristic electronic transitions can
be attributed to
pep transitions originating from the p-conjuga-
*
tion chain extended from the conjugated fluorene or carbazole
substituents on the DTS core. Absorptions of 1 and 2 exhibit a red-
shift of 5e10 nm as compared to those of 3 and 4, indicating that
2.2. Photophysical and electrochemical properties
the
p-conjugation between the DTS core and the two outer fluo-
Table 1 summarizes photophysical data and photoluminescence
rene moieties 1 and 2 is more effective compared to the carbazole
groups in 3 and 4. The replacement of a methyl group with a phenyl
group on the Si atom induces little change in absorption energy:
MeePh (1; lmax¼434 nm) versus PhePh (2; lmax¼436 nm) and
MeePh (3; lmax¼429 nm) versus PhePh (4; lmax¼427 nm).
Intense green emission with lmax at w500e510 nm is observed
for all compounds. The emission energy of 1e4 is significantly red-
shifted, compared to 5,50-bisalkyldithienosilole compounds2b but
comparable to that of 5,50-bisnaphthyldithienosiloles,2a which can
quantum efficiency (FPL) of compounds 1e4. UVevis absorption
Table 1
Absorption, luminescence, and thermal data of 1, 2, 3, and 4
d
Absorption,
Emission, lmax [nm]
FPL T1 (eV), Tg
Td
lmax [nm],
s
(ms)e (ꢀC) (ꢀC)f
Solution Film 77 Kc
at 298 K at
3
[104 Mꢁ1
cmꢁ1
]
a
298
Kb
be attributed to the greater p-conjugation of the DTS system due to
1 287(2.67), 337(2.02), 498
434 (5.19)
2 284 (2.49), 340 (2.17), 503
436 (4.63)
3 244 (7.66), 276 (4.76), 501
316 (2.92), 429 (4.21)
4 246 (7.04), 304 (4.21), 508
427 (2.24)
500
504
504
510
501/531 0.31 2.09,
0.12(7)
500/534 0.35 2.14,
0.11(1)
500/531 0.80 2.16,
0.12(3)
500/535 0.46 2.18,
0.10(2)
128.5 405.5
80.6 412.3
146.0 433.8
106.8 447.2
the addition of fluorene and carbazole substituents. Compounds
1e4 do not show any obvious emission color change from solution
to the solid state (PMMA film) as shown in Table 1 and Fig. 3, in-
dicating that intermolecular interactions or aggregations at low
concentration do not have significant impact on luminescence of
these molecules. However, a visible red-shift in emission up to
530 nm was observed for all compounds 1e4 as the concentration
of all compounds in PMMA film was increased (see Supplementary
data), a phenomenon that can be due to an occurrence of aggre-
gation and excimer formation in high doping levels.11 Among
compounds 1e4, the fluorene-substituted compound 1 has the
shortest emission wavelength, while the carbazole-substituted
compound 4 has the longest emission wavelength, the two values
differed by w10 nm.
a
The absorption spectra were measured in CH2Cl2 solution; [M]¼2.0e3.0ꢂ10ꢁ5
Doped into PMMA at 10 wt %.
In frozen Me/THF glass.
.
b
c
d
Photoluminescence quantum efficiency (FPL) measured in CH2Cl2, relative to
9,10-diphenylanthracene (FPL¼0.9), (error rangezꢃ5%).
e
Triplet energy (T1) was determined by emission maximum at 77 K and phos-
phorescence lifetime in excited state (millisecond regime).
f
Decomposition temperature (Td) was defined as 5% of weight loss under N2
atmosphere.
Fig. 3. (a) Photographs showing the emission color of compounds 1e4 in solution and PMMA film. (b) Emission spectra of 1e4 in PMMA film (10 wt %).

H. Park et al. / Tetrahedron 68 (2012) 9278e9283
9281
The fluorescence spectra of all compounds at 77 K display well-
resolved vibrational features along with minimal blue shifted
emission energy in contrast to the spectra at ambient temperature
(Fig. 2b). The phosphorescence spectra of all compounds were
obtained at 77 K using a time-resolved phosphorimeter with a de-
lay lifetime of 1 ms. The lmax of the phosphorescent peak is at
570e590 nm with a decay lifetime of w0.1 ms (see Table 1). Details
for phosphorescent emission are depicted in Supplementary data.
The triplet energy levels of all compounds were estimated to be
2.1e2.2 eV as derived from the emission maxima of the molecules
at 77 K; 2.09 eV for 1, 2.14 for 2, 2.16 eV for 3, and 2.18 eV for 4,
respectively. It is noteworthy that these values imply that all
compounds are suitable host materials for fluorescent red emitter.
The fluorescence quantum yields (VPL) of all compounds were
estimated by using 9,10-diphenylanthracene (DPA) as a reference
(VPL¼0.9). When studied alongside the DPA reference, the fluo-
rescence quantum yields of all compounds show moderate and
comparable quantum efficiency following the order of 3>4>2>1.
The quantum efficiency (VPL¼0.80) of compound 3 is truly im-
pressive, more than twice as high as the other three DTSs.
contribution (
s
*
) from the silicon atom. This calculation results are
similar to that reported for 5,50-bisnaphthyldithienosiloles.2a
The HOMO and LUMO energy levels of both 2 and 4 from DFT
calculations are shown in Fig. 4. The energies of the HOMO and
LUMO for 2 are lower by about 0.19 and 0.33 eV, respectively, as
compared to those for 4. The difference in value of the LUMO en-
ergy levels between the two molecules is much larger than that of
HOMO energy levels. The HOMOeLUMO energy gap (3.0 eV) for
both compounds, however, is very similar in value. These theoret-
ical calculations provide an evidence that the luminescence ob-
served in compounds 1e4 originates from the DTS-based
transitions with contribution of the Si atom.
pep
*
s
*
To investigate the electrochemical behavior of 1e4, cyclic vol-
tammetry experiments were carried out using ferrocene (Fc/Fcþ) as
the internal standard. All compounds showed quasi-reversible
oxidations in CH3CN (see Supplementary data). Interestingly,
compounds 1 and 4 show two reversible oxidation waves (Fig. 5),
while compounds 2 and 3 exhibit only one single reversible oxi-
dation each. However, an irreversible oxidation pattern has often
been observed in DTS derivatives according to previous reports.2
Based on these observations, fluorene and carbazole functional
groups provide the DTS derivatives greater electrochemical stabil-
ity. Similar reversible oxidation has also been reported in dithieno
[2,3-b:3,2-e][1,4]thiasiline (DTTS).15
To further understand the photophysical properties of 1e4, we
have scrutinized their electronic structures using density functional
theory (DFT). The computational calculations were performed
through Gaussian09 software package.12 B3LYP exchange-
correlation functional13 and 6-31G(d) basis set14 in DFT calculation
are applied for the geometry optimization. Due of the similar pho-
tophysical properties of 1e4, computational work was only per-
formed for compounds 2 and 4 as representative examples. From
optimized structures, small dihedral angles between DTS ring and
the two outer substituent groups are observed to be 24.8ꢀ for 2 and
ox
The oxidation potentials ðE Þ for 1, 2, 3, and 4 are at 0.87, 0.89,
1=2
0.84, and 0.85 V (vs Ag/AgCl), corresponding to 0.43, 0.45, 0.40, and
0.41 V (vs Fc/Fcþ), respectively. Using an oxidation potential of
ferrocene/ferrocenium (4.8 eV below the vacuum level),16 the
HOMO levels for 1, 2, 3, and 4 were deduced to be ꢁ5.23, ꢁ5.25,
ꢁ5.20, and ꢁ5.21 eV, respectively, which are comparable to those of
diaryldithiensiloles reported by Oshita2b and Ko1e et al.
26.4ꢀ for 4, respectively. These observations indicate that
p-conju-
gation of two outer functional groups via DTS ring occurs effectively.
The optical bandgap was determined by absorption edge (2.52 eV
for 1, 2.52 eV for 2, 2.54 eV for 3, and 2.53 eV for 4). The estimated
LUMO values were calculated to be ꢁ2.71 eV for 1, ꢁ2.73 eV
for 2, ꢁ2.66 eV for 3, and ꢁ2.68 eV for 4, respectively.
Electrochemical data and HOMO/LUMO levels of 1e4 are summa-
rized in Table 2. These small energy gaps suggest that the fluorene
As shown in Fig. 4, the HOMO levels of 2 and 4 mainly involve
contributions of
substituents without any contribution from the silicon atom,
whereas the LUMO level is largely dominated by orbital con-
tributions from DTS and the substituents along with a small
p
orbitals from the DTS backbone and the 5,50-
p
*
Fig. 4. Isodensity surface plots of the HOMO and LUMO for 2 and 4 (isodensity value¼0.02).

9282
H. Park et al. / Tetrahedron 68 (2012) 9278e9283
a
10
5
b
-2.5
LUMO
-2.66
-2.68
-2.71
-2.73
0
-3.0
-5
HOMO
-5.20
-5.21
-10
-15
-5.23
-5.25
-5.5
1
2
3
4
500
1000
1500
2000
Potential (mV) vs Ag/AgCl
Fig. 5. (a) CV diagram of 1 measured in CH3CN using Ag/AgCl as a reference electrode and Bu4NPF6 (0.5 mM) as an electrolyte at a scan rate of 100 mV/s. (b) Comparison of HOMO
and LUMO energies of 1e4 estimated from CV and optical energy gap.
and carbazole groups bound to the DTS ring at the 5,50-position in-
duce effective -conjugation forall compounds. The low-lying LUMO
levels for the1e4 molecules suggestthat all compounds may be good
were freshly distilled and further treated appropriate drying agents
prior to use. Conventional Schlenk line techniques were used, and
reactions were carried out under nitrogen atmosphere unless
otherwise noted. Starting materials, 5,50-diiodo-1-methyl-10-phe-
nyldithienosilole, 5,50-diiodo-1,10-diphenyldithienosilole were
prepared using previously reported methodologies.2a
p
candidates as electron-transporting materials in OLEDs.
Table 2
Electrochemical data and HOMO/LUMO energies of 1, 2, 3 and 4
[V]a
Egopt [eV]b
HOMO [eV]c
LUMO [eV]c
ox
Compound
E
4.2. Measurement
1=2
1
2
3
4
0.43
0.45
0.40
0.41
2.52
2.52
2.54
2.53
ꢁ5.23
ꢁ5.25
ꢁ5.20
ꢁ5.21
ꢁ2.71
ꢁ2.73
ꢁ2.66
ꢁ2.68
1H NMR spectra were recorded with a Bruker Avance 300 MHz
or 400 MHz spectrometer instrument. The absorption and photo-
luminescence spectra were acquired on a PerkineElmer Lambda 2S
UVeVisible spectrometer and a Perkin LS fluorescence spectrom-
eter, respectively. The fluorescence quantum yields (FPL) were de-
termined by using 9,10-diphenylanthracene (0.9) as a reference
according to literature methods.17 Quantum yields were corrected
as follows:
a
b
c
ox
1=2
E
¼ ðEpc þ EpaÞ=2; (vs Fc/Fcþ).
Optical bandgap Egopt from the absorption edge.
HOMO and LUMO energies were determined using the following equations:
EHOMOðeVÞ ¼ ꢁeðEox þ 4:8Þ; ELUMOðeVÞ ¼ ðEHOMO ꢁ EgoptÞ:
1=2
It is noted that the substituents on the Si atom have a small
impact on the LUMO energy. Compounds 2 and 4 have slightly
lower LUMO energy levels than those of compounds 1 and 3, which
may be attributed to the electron withdrawing nature of the phenyl
group bound to the silicon atom. The HOMOeLUMO energy trend is
also consistent with the slight red-shift of emission energy of the
phenyl substituted DTS compounds (2 and 4), compared to the
corresponding methyl analogues (1 and 3).
À
Á
ꢀ
ꢁ
A
A
rh2s Ds
sh2r Dr
À
Á
s ¼ r
where the s and r designate the sample and reference samples,
respectively, A is the absorbance at lex, h is the average refractive
index of the appropriate solution, and D represents the integrated
area under the corrected emission spectrum.18 Cyclic voltammetry
was carried out with a BAS 100B (Bioanalytical Systems, Inc.) under
nitrogen atmosphere in a one-compartment electrolysis cell con-
sisting of a platinum wire working electrode, a platinum wire
counter electrode, and a quasi Ag/AgCl reference electrode. Cyclic
voltammograms were monitored at scan rates of either 100 mV sꢁ1
or 50 mV sꢁ1 and recorded in distilled acetonitrile. The concen-
tration of the complex was maintained at 0.5 mM or less and each
3. Conclusion
The one-step synthesis of a series of fluorene and carbazole-based
DTS derivatives by using indium nucleophiles in the presence of Pd(II)
catalyst has been achieved. Investigation on the thermal, photo-
physical, and electrochemical properties of the new DTS compounds
demonstrated that introduction of conjugated fluorene/carbazole
substituents on the DTS system leads to high thermal stability, re-
versible electrochemical behaviors, and intense green emission.
Among the four compounds, compound 3 exhibits bright green
emission with high a quantum efficiency. Our finding provides valu-
able insights for future design and development of new organic ma-
terials with multi-functionality based on the DTS linkage as a key
building block. Additional examination of OLEDs performance fabri-
catedbyusingthesederivativesaseitherhostorelectron-transporting
materials is currently being investigated in our laboratory.
solution contained 0.1
M
of tetrabutyl ammoniumhexa-
fluorophosphate (TBAP) as an electrolyte. The ferrocenium/ferro-
ox
cene couple (E
: 0.40 V) was used as the internal standard.
onset
Thermogravimetric analysis (TGA) was performed under nitrogen
on a TA instruments SDT Q600. The sample was heated using
a 10 ꢀC/min heating rate from 30 ꢀC to 700 ꢀC under N2 atmosphere.
Differential scanning calorimetry (DSC) was conducted with TA
instruments DSC Q2000. The sample was heated at 10 ꢀC/min from
20 ꢀC to 350 ꢀC under a N2 gas flow rate of 50 mL/min. An empty
aluminum pan was used as a standard.
4. Experimental section
4.3. Theoretical calculation
4.1. General experimental methods
The computational calculations were performed using Gauss-
ian09, revision B.01 software package12 and the High Performance
Computing Virtual Laboratory (HPCVL) at Queen’s University. The
ground-state geometries were fully optimized at the B3LYP
All reagents were purchased from commercial sources and used
without further purification unless otherwise noted. All solvents

H. Park et al. / Tetrahedron 68 (2012) 9278e9283
9283
exchange-correlation functional13 using 6-31G(d) basis set14 and
visualized by GaussView 5 software.
d 149.3, 147.7, 142.1, 141.3, 140.9, 137.9, 136.4, 135.9, 132.4, 132.0,
131.7,131.0,130.5,129.2,128.8,128.1,127.5,127.3,126.8,125.3,124.8,
124.4, 123.7, 120.9, 120.8, 117.8, 110.7, 110.4. MALDI-TOF MS (m/z):
828.1818. Anal. Calcd for C56H36N2S2Si: C, 81.12; H, 4.38; N, 3.38
Found: C, 81.21; H, 4.32; N, 3.35.
4.4. General preparation of 1e4
The (9,9-dimethylfluoren-3-yl)lithium or (9-phenylcarbazole-3-
yl)lithium was prepared from the 2-bromo-9,9-dimethylfluorene
or 3-iodo-9-phenylcarbazole (0.21 g, 1.05 mmol) by treatment
with n-BuLi (1.05 mmol, 1.6 M in hexane) at ꢁ78 ꢀC for 15 min
followed by equilibration to room temperature. This compound
was used immediately for the preparation of either tri-arylindium,
tris(9-phenylcarbazole-3-yl)indium or tris(9,9-dimethylfluoren-3-
yl)indium. To a solution of InCl3 (0.076 g, 0.35 mmol) in THF
(5 mL) at ꢁ78 ꢀC, (9,9-dimethylfluoren-3-yl)lithium (1.05 mmol in
Et2O) was added under a nitrogen atmosphere and the mixture was
stirred for 30 min. After the cooling bath was removed, the reaction
mixture was warmed to room temperature for 30 min. The solution
of this indium reagent was subsequently added to a mixture of
Pd(dppf)Cl2 (0.031 g, 4 mol %), [1,10-bis(diphenylphosphino)ferro-
cene]dichloropalladium(II), and the corresponding 5,50-diiododi-
thienosiloles (0.5 mmol) in THF under a nitrogen atmosphere. The
reaction mixture was stirred at 80 ꢀC for 10 h or until the starting
material was consumed, as monitored on TLC. After being cooled to
room temperature, the reaction mixture was quenched by water.
The aqueous layer was extracted with CH2Cl2, and the combined
organic layers were sequentially washed with saturated aqueous
NaCl (20 mL), dried with MgSO4, filtered, and concentrated under
reduced pressure. The residue was purified by silica gel column
chromatography using CH2Cl2 and hexane to give titled compounds
(40e60% isolated yield) as a pale-yellow or an orange-red solid.
Acknowledgements
This study is supported by Kangwon National University.
Supplementary data
1H NMR, 13C NMR, mass, DSC, CV data, phosphorescent emission
spectra at 77 K, and emission photos at room temperature. Sup-
plementary data associated with this article can be found in the
online version, at http://dx.doi.org/10.1016/j.tet.2012.08.056.
References and notes
1. (a) Recent review: Ohshita, J. Macromol. Chem. Phys. 2009, 210, 1360e1370; (b)
Recent review: Corey, J. Y. Adv. Organomet. Chem. 2011, 59, 286e324 and ref-
erences cited therein (c) Son, H. J.; Han, W. S.; Chun, J. Y.; Kwon, S. N.; Ko, J.;
Kang, S. O. Organometallics 2008, 27, 2464e2473; (d) Ohshita, J.; Kurushima, Y.;
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Yamashita, K.; Ishikawa, M. Organometallics 1999, 18, 1453e1459.
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4.4.1. The preparation of 5,50-bis(9,9-dimethylfluoren-2-yl)-1-
methyl-1-phenyldithienosilole (1). Yield: 0.18 g (53%). Mp 207 ꢀC;
1H NMR (CDCl3):
d
7.64 (m, 4H), 7.59e7.62 (m, 3H), 7.52 (dd, J¼7.8
1.5 Hz, 2H), 7.31e7.20(m,10H), 7.18 (s, 2H), 1.46 (s, 12H), 0.73 (s, 3H).
13C{1H} NMR (CDCl3):
154.81, 154.18, 149.28, 146.80, 142.87,
5. (a) Zhan, X.; Barlow, S.; Marder, S. R. Chem. Commun. 2009, 1948e1955; (b)
Zhan, X.; Haldi, A.; Risko, C.; Chan, C. K.; Zhao, W.; Timofeeva, T. V.; Korlyukov,
A.; Antipin, M. Y.; Montgomery, S.; Thompson, E.; An, Z.; Domercq, B.; Barlow,
d
139.16, 138.99, 134.87, 133.98, 133.76, 130.63, 128.65, 127.70, 127.49,
125.89, 125.23, 123.02, 120.88, 120.22, 120.39, 47.33, 27.60, ꢁ4.71.
MALDI-TOF MS (m/z): 668.1806. Anal. Calcd for C45H36S2Si: C,
80.79; H, 5.42. Found: C, 80.72; H, 5.48.
ꢀ
S.; Kahn, A.; Kippelen, B.; Bredas, J.-L.; Marder, S. R. J. Mater. Chem. 2008, 18,
3157e3166.
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K.; Kang, Y. Org. Electron. 2009, 10, 1066e1073.
4.4.2. The preparation of 5,50-bis(9,9-dimethylfluoren-2-yl)-1,1-
diphenyldithienosilole (2). Yield: 0.22 g (60%) yield. Mp 250 ꢀC
9. Zhao, X.; Zhan, X. Chem. Soc. Rev. 2011, 40, 3728e3743.
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Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.;
Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.;
Montgomery, J. A.; Peralta, J. E., Jr.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers,
E.; Kudin, K. N.; Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand, J.;
Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.;
Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.;
Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.;
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Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford,
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(dec); 1H NMR (CDCl3):
d
7.68e7.60 (10H, m), 7.55e7.52 (2H, m),
7.46 (2H, s), 7.39e7.24 (12H, m), 1.46 (12H, s). 13C{1H} NMR (CDCl3):
153.4, 152.8, 148.3, 145.7, 139.9, 137.1, 137.6, 134.5, 132.5, 130.5,
d
129.4, 127.3, 126.3, 126.1, 124.5, 123.8, 121.6, 119.5, 118.9, 118.8, 45.9,
26.1. MALDI-TOF MS (m/z): 730.2152. Anal. Calcd for C50H38S2Si: C,
82.15; H, 5.24. Found: C, 82.31; H, 5.17.
4.4.3. The preparation of 5,50-bis(9-phenylcarbazol-3-yl)-1-methyl-
1-phenyldithienosilole (3). Yield: 0.21 g (55%). Mp 170 ꢀC; 1H NMR
(CDCl3):
d
8.30 (d, J¼0.23 Hz, 2H), 8.10 (d, J¼7.64 Hz, 2H), 7.33 (m,
25H), 7.19 (s, 2H), 0.76 (s, 3H). 13C{1H} NMR (CDCl3):
d
148.78,
147.05, 142.42, 141.79, 140.69, 137.91, 134.92, 134.13, 130.53, 130.35,
128.63, 127.99, 127.46, 127.38, 126.69, 125.07, 124.76, 124.29, 123.68,
120.86, 120.60, 117.85, 110.58, 110.39, ꢁ4.55. MALDI-TOF MS (m/z):
766.1932 Anal. Calcd for C51H34N2S2Si: C, 79.86; H, 4.47; N, 3.65
Found: C, 79.93; H, 4.43; N, 3.61.
4.4.4. The preparation of 5,50-bis(9-phenylcarbazol-3-yl)-1,1-diphe-
nyldithienosilole (4). Yield: 0.21 g (51%). Mp 140 ꢀC (dec); 1H NMR
(CDCl3):
d
8.34 (d, J¼1.2 Hz, 2H), 8.11 (d, J¼7.6 Hz, 2H), 7.71e7.69 (m,
4H), 7.65 (dd, J¼8.5, 1.8 Hz, 2H), 7.58e7.50 (m, 10H), 7.44e7.32 (m,
14H), 7.25e7.21 (dd, J¼5.7, 2.2 Hz, 2H). 13C{1H} NMR (CDCl3):