3,6,9,12-tetrasubstituted chrysenes: Synthesis, photophysical properties, and application as blue fluorescent OLED

Article abstract of DOI:10.1021/jo402429q

A short synthesis of unsubstituted chrysene is described to provide a cheap source of this compound. This chrysene was used to prepare 3,6,9,12- tetrabromochrysene, which was subsequently transformed into various 3,6,9,12-tetrasubstituted chrysenes bearing four aryl, alkynyl, or amino groups by means of the Suzuki, Sonogashira, or Buchwald-Hartwig coupling reaction, respectively. These substituents result in large bathochromic shifts in the chrysene absorption and emission spectra. These new chrysene derivatives show blue fluorescent emission (401-471 nm) with high quantum yields (0.44-0.87). DFT calculations on these chrysenes rationalize well the substituent effects on their HOMO and LUMO energy levels. One representative chrysene (6g) was used as a blue fluorescent emitter in an OLED device that showed an outstanding external quantum efficiency (η = 6.31%) with blue emission [CIE (x, y) = (0.13, 0.20)] and a low turn-on voltage (3.0 V).

Full text of DOI:10.1021/jo402429q

Article
pubs.acs.org/joc
3,6,9,12-Tetrasubstituted Chrysenes: Synthesis, Photophysical
Properties, and Application as Blue Fluorescent OLED
Tien-Lin Wu, Ho-Hsiu Chou, Pei-Yun Huang, Chien-Hong Cheng, and Rai-Shung Liu*
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan, ROC
S
* Supporting Information
ABSTRACT: A short synthesis of unsubstituted chrysene is described to provide a cheap source of this compound. This
chrysene was used to prepare 3,6,9,12-tetrabromochrysene, which was subsequently transformed into various 3,6,9,12-
tetrasubstituted chrysenes bearing four aryl, alkynyl, or amino groups by means of the Suzuki, Sonogashira, or Buchwald−
Hartwig coupling reaction, respectively. These substituents result in large bathochromic shifts in the chrysene absorption and
emission spectra. These new chrysene derivatives show blue fluorescent emission (401−471 nm) with high quantum yields
(0.44−0.87). DFT calculations on these chrysenes rationalize well the substituent effects on their HOMO and LUMO energy
levels. One representative chrysene (6g) was used as a blue fluorescent emitter in an OLED device that showed an outstanding
external quantum efficiency (η = 6.31%) with blue emission [CIE (x, y) = (0.13, 0.20)] and a low turn-on voltage (3.0 V).
which the data fail to reflect the potential of the chrysene
family. For instance, the reported OLED device gave a broad
blue emission with CIE (x, y) = (0.23, 0.35) in addition to a
small current efficiency (1.5 cd/A). We report herein a
convenient synthesis of chrysene that enables the subsequent
preparation of tetrasubstituted chrysene derivatives. Notably,
the introduction of suitable substituents significantly alters the
photophysical properties and enhances the quantum yield.
Importantly, one representative chrysene was used as a blue
fluorescent emitter with outstanding OLED performance (7.2
cd/A).
INTRODUCTION
■
Polycyclic aromatic hydrocarbons (PAHs) have found wide-
spread applications in organic light-emitting diodes (OLEDs)
for decades.1−5 Small polyaromatic hydrocarbons serve as
appealing materials because of their high carrier mobility6 and
oxidation resistance.1−6 The energy gaps (3−4 eV) of these
PAHs make these compounds suitable for use as OLED active-
layer materials as either host or blue dopants. Considerable
interest has focused on the elaboration of anthracenes,1
pyrenes,2 fluorenes,3 and perylenes4 as OLED materials.
Among these small PAHs, pyrene derivatives are particularly
notable because of their outstanding OLED performance as
host materials. Examples include 1-(4-(1-pyrenyl)phenyl)-
pyrene (PPP), 1-(2,5-dimethoxy-4-(1-pyrenyl)phenyl)pyrene
(DOPPP), and 1-(2,5-dimethyl-4-(1-pyrenyl)phenyl)pyrene
(DMPPP).2a
Chrysene resembles pyrene in comprising a fused tetracene
core; this structural comparison presages its prospective use in
OLED devices.5 However, its development has been impeded
by both the lack of a convenient synthesis7 and the costly
commercial materials ($306/g, purity >97%).8 Reported
syntheses of chrysene derivatives are based mainly on
naphthalene derivatives bearing special functional groups,
which requires a long procedure.7 There is only one literature
report5 on tetraphenylchrysene used in an OLED device, of
RESULTS AND DISCUSSION
We previously reported regiocontrolled syntheses of ethylene-
bridged p-phenylene oligomers based on platinum-catalyzed
■
Received: October 31, 2013
Published: December 2, 2013
© 2013 American Chemical Society
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Article
Scheme 1. Synthetic Path To Produce Chrysene (4)
Scheme 2. Synthesis of Compounds 6a−g
aromatization of 2-aryl-1-ethynylbenzenes.9 The reported
procedures for chrysene derivatives are tedious, and commercial
chrysene (4) is costly. We employed this platinum-catalyzed
aromatization to develop a short synthesis of 4, as outlined in
Scheme 1. An initial Sonogashira coupling reaction10 of 2-
bromo-1-iodobenzene with (trimethylsilyl)acetylene provided
2-alkynyl-1-bromobenzene 2 in 94% yield, of which a
subsequent Suzuki coupling11 gave the desired product 3 in
82% yield. Species 3 was then desilylated with K2CO3 and
subsequently treated with PtCl2 in hot toluene to give 4 in 85%
yield with high regioselectivity (>20:1). Chrysene 4 was
converted to 3,6,9,12-tetrabromochrysene (5) by direct
bromination (Br2, 6 equiv) in neat trimethyl phosphate at
100 °C (3 days) according to a procedure reported by Ionkin
and co-workers.5
and LUMO energy levels of tetrasubstituted chrysenes with
suitable aryl, alkynyl, and amino groups because these
substituents can significantly alter the energy levels of an
anthracene core.1b,c As shown in Scheme 2, treatment of
tetrabromochrysene 5 with various 2-aryl-1,3,2-dioxaborolanes
(6 equiv, Ar = 3,5-di-tert-butylphenyl, 4-tert-butylnaphthalen-1-
yl, 6-tert-butylphenanthren-2-yl, and 7-tert-butylpyren-1-yl),
Na2CO3 (60 equiv), and Pd(PPh3)4 (15 mmol %) in a
EtOH/toluene/H2O mixed solvent afforded the resulting
Suzuki coupling products 6a−d in 10−27% yield. We also
employed Sonogashira coupling reactions on tetrabromide
species 5 to give tetraalkynyl-substituted chrysene derivatives
6e [R = Si(i-Pr)3] and 6f (R = 3,5-di-tert-butylphenyl) in 22−
29% yield after purification from a silica gel column. The
introduction of four diarylamino groups was achieved also with
the Buchwald−Hartwig coupling reaction,13 providing com-
pound 6g as a yellow solid in 20% yield. The overall yields of
10−29% in such fourfold coupling reactions are acceptable
Among tetrasubstituted chrysenes,5,12 there have been no
reports on the systematic variation of their photophysical
properties with substituents. We sought to vary the HOMO
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Article
because each step corresponds to 56−72% yield. During these
catalytic coupling reactions, we did not attempt to isolate the
mono-, bis-, or trisubstituted products, which existed in minor
proportions as monitored by TLC and NMR.
Single crystals of 6a suitable for X-ray diffraction were grown
in hexane/dichloromethane. The ORTEP drawing of 6a
(Figure 1) shows a symmetrical structure with four di-tert-
substituted chrysenes 6a−6d, the alkynyl- and amino-
substituted analogues 6e−g have three absorption maxima.
The absorption maxima of aryl-substituted chrysenes 6a−d
increase gradually with increasing size of their aryl arrays; this
phenomenon supports our postulated electron delocalization
over the aryl groups and the chrysene core. Compounds 6a−g
are strongly fluorescent with high quantum yields (Φ) of 0.44−
0.87), which are much greater than that of chrysene 4 itself (Φ
= 0.12). The PL emission wavelength of diarylamino-
substituted chrysene 6g is somewhat affected by solvent
polarity (e.g., 456 nm in hexane, 471 nm in CH2Cl2, and 470
nm in acetonitrile), showing a small degree of charge-transfer
character in its excited states.14 The presence of four
substituents is expected to decrease intermolecular π−π
interactions between two chrysene cores, thus inhibiting
intermolecular fluorescence quenching. The increasing quan-
tum yields (Φ = 0.61−0.87) for chrysene derivatives 6a−d are
attributed to the increasing sizes of their aryl substituents.
Compounds 6a−d and 6g showed one-electron quasi-
reversible oxidation in CH2Cl2, as revealed by cyclic
voltammetry (CV) measurements;15 compound 6g bearing
four amino groups undergoes no second oxidation to form a
dicationic species.16 We determined their HOMO energies
ox
1/2
(EHOMO) from the E potentials and the band gaps (ΔE) from
the UV absorption. The LUMO energies were then obtained as
ELUMO = EHOMO + ΔE. Compounds 6e and 6f have excessively
low HOMO energies that were beyond the detection limit of
the CV method. Their HOMO energies were measured by
photoelectron spectroscopy and found to be −6.09 and −5.84
eV, respectively [see the Supporting Information (SI)]. A
summary of the HOMO and LUMO energies is provided in
Figure 3. These data clearly reflect the substituent effects, which
generate small band gaps for aryl-substituted chrysenes 6a−d
(ΔE = 3.08−3.30 eV, ca. 0.47−0.69 eV smaller than that of
unsubstituted chrysene 4). Electron-withdrawing alkynyl
substituents, as in compounds 6e and 6f, lower the energies
of both the HOMO and the LUMO, giving ΔE = 3.04 and 2.81
eV respectively. For compound 6g bearing π-donating
diarylamino groups, the band gap is ΔE = 2.73 eV; this small
value implies that the amino groups raise the HOMO energy to
a larger extent than the LUMO energy.
Figure 1. ORTEP drawing of species 6a.
butylphenyl substituents located on carbons C1, C20, C1′ ,and
C20′. The torsion angles between chrysene and the two phenyl
rings on the C1 and C1′ carbons are 49° and 54°, respectively,
and the planes between chrysene and the phenyl rings on the
C20 and C20′ carbons show smaller torsion angles of ca. 34°.
These angles allow partial electron delocalization within four
phenyl groups and the chrysene core, resulting in variability of
the photophysical parameters (Table 1).
Figure 2 shows the UV/vis and photoluminescence (PL)
spectra of chrysene derivatives 6a−g in CH2Cl2 (Figure 2);
their key photophysical parameters are summarized in Table 1.
Relative to unsubstituted chrysene 4 (entry 1), there are large
bathochromic shifts for the absorption and emission spectra of
the new tetrasubstituted chrysenes 6a−6d; their absorption
maxima are observed within the range 296−433 nm, and their
emission bands are within 401−470 nm. In contrast to aryl-
To understand the electronic structures of such chrysene
derivatives, we performed time-dependent density functional
theory (TD-DFT) calculations at the B3LYP/6-31G* level for
Figure 2. Absorption and emission spectra of compounds 4 and 6a−g in CH2Cl2.
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Table 1. Photophysical Properties of Compounds 4 and 6a−g
a
ab
,
ac
,
d
f
abs
max
PL
max
compound
λ
(nm)
λ
(nm)
Φ (%)
EHOMO/ELUMO (eV)
band gap (eV)
4
309, 322
296, 351
300
366, 383
401
12.2
60.9
72.0
78.1
87.4
74.1
62.6
44.0
−5.29/−1.52
−5.64/−2.45
−5.72/−2.42
−5.66/−2.58
−5.63/−2.55
−6.09/−3.04
−5.84/−3.03
−5.02/−2.29
3.77
3.19
3.30
3.08
3.08
3.05
2.81
2.73
6a
6b
6c
6d
6e
6f
405
303
424
349
443
e
308, 372, 394
329, 396, 416
408, 428
439, 466
471
e
6g
299, 370, 433
b
a
c
d
In CH2Cl2, 1.0 × 10−5 M. Excitation wavelengths are shown in the Experimental Section. Coumarin-1 was used as a standard. EHOMO values
were determined by CV. EHOMO was determined by photoelectron spectroscopy. Band gaps were calculated from UV/vis absorption.
e
f
Figure 3. HOMO and LUMO energies of species 4 and 6a−g.
compound 6a using its crystallographic data (Figure 1). We
found that the distributions of both the HOMO and the
LUMO of compound 6a (Figure 4) were located mainly on the
N,N′-bis[4-(N,N-diphenylamino)phenyl]benzidine (NPNPB),
4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), 1-
[2,5-dimethyl-4-(1-pyrenyl)phenyl]pyrene (DMPPP), and bis-
(2-methyl-8-quinolinato)(4-phenylphenolato)aluminum
(BAlq2) are shown in Scheme 3. The device showed a low
activation voltage of 3.0 V, a large external quantum efficiency
of ηext = 6.31%, a current efficiency of ηc = 7.2 cd A−1, a power
efficiency of ηp = 3.21 lm W−1, and a maximum brightness of up
to 42 325 cd/m2. Figure 5 shows the EL spectrum with a
maximum wavelength 471 nm and no shoulder at an applied
voltage of 8.0 V (Figure 5); this emission pattern was
unaffected by the use of a range of applied voltages (6−10
V). The CIE (x, y) coordinates of (0.13, 0.20) are indicative of
a satisfactory blue color quality. A similar OLED without
compound 6g showed a distinct emission at 450 nm with ηext
=
Figure 4. HOMO and LUMO of 6a obtained from DFT calculations.
4.0%, ηc = 3.4 cd A−1, and ηp = 1.1 lm W−1.18 Accordingly, the
blue dopant 6g really enhances the OLED performance with an
effective energy transfer from the host material.18 Among blue
fluorescent OLEDs, distyrylamine (DSA) derivatives are the
most commonly referred dopants.19 Lee et al.19c reported that a
light-blue EL device using p-bis(p-N,N-diphenylaminostyryl)-
benzene (DSA-Ph) reaches a current efficiency of 9.7 cd A−1
with CIE (x, y) = (0.16, 0.32). Our preliminary data reflect the
prospects of chrysene derivative 6g as a blue fluorescent
material.
central chrysene core, with minor distributions on the four
phenyl rings. For both the HOMO and the LUMO, significant
orbital coefficients were situated at the carbons linked to the
phenyl groups (C1, C20, C1′, and C20′; see Figure 1). This
feature indicates that the energies of both orbitals could be
affected significantly by various electron-donating or -with-
drawing substituents, consistent with our observations in Figure
3.
Chrysene derivative 6g was used as a dopant to fabricate blue
fluorescent OLEDs by thermal evaporation because of its
suitable emission wavelength (471 nm) and satisfactory
quantum yield (Φ = 0.44). Its PL is affected by solvent
polarity but to only a small extent; this property does not result
in undesired electroluminescence (EL) red shifts as for some
monostyrylamine materials.17 The multilayer configuration
consisted of ITO/NPNPB (80 nm)/NPB (10 nm)/DMPPP:6g
(5%) (25 nm)/BAlq2 (20 nm)/LiF (1 nm)/Al (100 nm). The
device components and molecular structures of N,N′-diphenyl-
CONCLUSION
■
Before this work, there was no systematic study on the
photophysical properties of chrysene derivatives to evaluate
their prospects in OLED devices. In this work, a convenient
synthesis of chrysene was developed and further utilized to
prepare 3,6,9,12-tetrasubstituted chrysenes bearing various aryl,
alkynyl, and diarylamino groups. Relative to unsubstituted
chrysene 4, there are large bathochromic shifts in the UV/vis
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Scheme 3. (a) Structure of the 6g-Based Device and Energy Levels of the Materials; (b) Structures of NPNPB, NPB, DMPPP,
and BAlq2
X-ray diffractometer. The compound [(2-bromophenyl)ethynyl]-
trimethylsilane (2) was prepared from 1-bromo-2-iodobenzene
according to a literature procedure.20 3,6,9,12-Tetrabromochrysene
(5) was prepared from chrysene 4 according to the procedure reported
by Ionkin et al.5 Various reagents including (3,5-di-tert-butylphenyl)-
pinacolborane,21 (6-tert-butylphenanthren-2-yl)pinacolborane,22 (7-
tert-butylpyren-1-yl)pinacolborane,23 1,3-di-tert-butyl-5-ethynylben-
zene,24 and bis(4-tert-butylphenyl)amine25 were prepared according
to the cited literature.
Photophysical Properties. UV/vis absorption and PL spectra
were recorded on samples in dichloromethane (1.0 × 10−5 M) using a
fluorescence spectrophotometer. The quantum yield was measured
with reference to coumarin-1 (Φf = 0.99).26 Electrochemical
measurements were undertaken with an electrochemical analyzer
employing Ag/Ag+ (Ag/0.01 M AgNO3) as the reference electrode, a
Pt wire as the counter-electrode, a glassy carbon electrode as the
working electrode, and an internal ferrocene/ferrocenium (Fc/Fc+)
standard. Samples were prepared in dry CH2Cl2 (1.0 × 10−3 M)
containing tetrabutylammonium hexafluorophosphate (0.1 M) as the
Figure 5. EL spectra of compound 6g as a dopant at various voltages.
supporting electrolyte. The energy level of Fc/Fc+ was taken as 4.8 eV;
the HOMO energies were determined using the equation EHOMO = 4.8
ox
and PL spectra of these new chrysene derivatives, and their
quantum yields are greatly enhanced. The HOMOs and
LUMOs of these new chrysenes are easily affected by the
presence of aryl, alkynyl, and amino substituents because
significant orbital coefficients are located on the chrysene
3,6,9,12-carbons linked to these substituents. Diarylamino-
substituted chrysene 6g was tested as a blue fluorescent emitter
in an OLED; this device showed an outstanding external
quantum efficiency (η = 6.31%) with blue emission [CIE (x, y)
= (0.13, 0.20)] and a low turn-on voltage (3.0 V).
eV + E . The HOMO energies of 6e and 6f were measured using a
1/2
photoelectron spectrometer (AC-2) in ambient air with a UV source.
OLED Device Fabrication. The EL devices with the configuration
ITO/NPNPB (80 nm)/NPB (10 nm)/DMPPP:6g (5%) (25 nm)/
BAlq2 (20 nm)/LiF (1 nm)/Al (100 nm) were fabricated by
sequential thermal evaporation onto clean glass precoated with a
layer of indium tin oxide (ITO) having a sheet resistance of 25 Ω/
square. The effective area of the emitting diode was 9.00 mm2.
Current, voltage, and light intensity were recorded simultaneously
using a source meter and an optical meter equipped with a silicon
photodiode. EL spectra were measured on a fluorescence spectropho-
tometer. All of the measurements were performed near 23 °C in air.
Synthesis of Compound 3. A mixed solution of toluene (160
mL), EtOH (40 mL), and water (40 mL) was degassed with nitrogen
for 30 min; to this solution were added compound 220 (1.68 g, 6.63
mmol), Pd(PPh3)4 (390 mg, 0.33 mmol), Na2CO3 (2.11 g, 19.89
mmol), and naphthalen-2-ylboronic acid (1.14 g, 6.63 mmol). The
resulting mixture was heated at 80 °C for 24 h, and the solution was
extracted with hexane and concentrated. The crude material was
purified by silica gel column chromatography (hexane) to afford
compound 3 (1.63 g, 5.44 mmol, 82%) as a yellow oil. 1H NMR (400
MHz, CDCl3): δ 8.06 (d, J = 1.3 Hz, 1H), 7.87−7.84 (m, 3H), 7.75
(dd, J = 1.8, 8.5 Hz, 1H), 7.60 (dd, J = 1.4, 7.5 Hz, 1H), 7.50−7.47 (m,
3H), 7.40 (td, J = 1.4, 7.5 Hz, 1H), 7.29 (td, J = 1.4, 7.5 Hz, 1H), 0.06
EXPERIMENTAL SECTION
■
General Information. All of the experimental operations were
performed under nitrogen; the equipment was dried in an oven at 150
°C for several hours. THF and toluene were distilled over sodium
particles. CH2Cl2 was distilled over calcium hydride. All other specified
chemicals were commercially purchased and used without further
1
purification. H and 13C NMR spectra were determined on either a
400 or 600 MHz NMR spectrometer using CDCl3 or CD2Cl2. HRMS
was performed on double-focusing sector mass spectrometer in EI
mode. MALDI mass determination was performed on a MALDI-TOF
mass spectrometer. Elemental analysis was performed on an element
analyzer. The single-crystal X-ray structure of 6a was collected on an
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Article
(s, 9H). 13C NMR (100 MHz, CDCl3): δ 144.0, 137.7, 133.4, 133.4,
133.0, 132.6, 129.6, 128.7, 128.3, 128.1, 127.6, 127.5, 127.1, 126.9,
125.9, 121.6, 104.9, 97.6, −0.3. HRMS Calcd for C21H20Si: 300.1334.
Found: 300.1335.
Synthesis of 3,6,9,12-Tetrakis(6-tert-butylphenanthren-2-
yl)chrysene (6c). Compound 6c was prepared in a similar manner
as 6a from compound 5 (272 mg, 0.50 mmol) and (6-tert-
butylphenanthren-2-yl)pinacolborane22 (1.08 g, 3.00 mmol) and was
obtained as a light-yellow solid (81 mg, 0.07 mmol, 13%). Mp: >360
Synthesis of Compound 4. Compound 3 (1.63 g, 5.43 mmol)
was dissolved in MeOH/CH2Cl2 (100 mL/100 mL) and then K2CO3
was added (75 mg, 0.54 mmol); the resulting solution was stirred for 3
h. The solution was treated with water and extracted with
dichloromethane (3 × 40 mL). The combined organic phases were
dried over MgSO4 and evaporated to dryness. The crude product was
purified on a flash silica gel column (hexane) to afford a yellow oil.
This oil was treated with dry toluene (300 mL) and PtCl2 (143 mg,
0.54 mmol) under an argon atmosphere at 85 °C for 8 h. The resulting
solution was extracted with dichloromethane. The extract was dried
over MgSO4, concentrated under reduced pressure, and purified on a
silica gel column (dichloromethane/hexane 1/10) to afford chrysene
(4) (1.05 g, 4.62 mmol, 85%) as a light-yellow solid. Mp: 254−255 °C.
1H NMR (400 MHz, CDCl3): δ 8.76 (d, J = 8.4 Hz, 2H), 8.70 (d, J =
1
°C. H NMR (400 MHz, CDCl3): δ 9.29 (s, 2H), 9.01 (s, 2H), 8.97
(d, J = 8.7 Hz, 2H), 8.82 (d, J = 8.7 Hz, 2H), 8.81 (s, 2H), 8.68 (s,
2H), 8.29−8.25 (m, 6H), 8.11 (dd, J = 1.8, 8.6 Hz, 2H), 8.04 (dd, J =
1.8, 8.4 Hz, 2H), 8.01 (dd, J = 1.6, 8.6 Hz, 2H), 7.91 (d, J = 8.4 Hz,
2H), 7.86−7.66 (m, 14H), 1.55 (s, 18H), 1.48 (s, 18H). 13C NMR
(100 MHz, CDCl3): δ 149.7, 149.5, 139.2, 139.2, 139.0, 132.6, 132.4,
131.4, 130.6, 130.2, 130.1, 129.9, 129.9, 129.9, 129.8, 129.8, 128.8,
128.4, 128.3, 128.1, 127.8, 127.3, 127.2, 127.1, 126.5, 126.3, 126.3,
126.3, 126.0, 125.1, 125.0, 123.4, 122.7, 122.6, 122.1, 118.4, 118.3,
35.3, 35.2, 31.6, 31.5. MALDI-TOF-MS Calcd for C90H76: 1156.5947.
Found: 1156.426. Anal. Calcd for C90H76: C, 93.38; H, 6.62. Found: C,
93.29; H, 6.55.
Synthesis of 3,6,9,12-Tetrakis(7-tert-butylpyren-1-yl)-
chrysene (6d). Compound 6d was prepared in a similar manner as
6a from compound 5 (290 mg, 0.52 mmol) and (7-tert-butylpyren-1-
yl)pinacolborane23 (1.20 g, 3.12 mmol) and was obtained as a light-
9.0 Hz, 2 H), 8.01−7.97 (m, 4H), 7.71−7.67 (m, 2H), 7.64−7.60 (m,
2H). 13C NMR (100 MHz, CDCl3): δ 132.2, 130.6, 128.5, 128.2,
127.3, 126.7, 126.4, 123.1, 121.2. HRMS Calcd for C18H12: 228.0939.
Found: 228.0942. The spectral data agree satisfactorily with a literature
report.27
1
yellow solid (63 mg, 0.05 mmol, 10%). Mp: >360 °C. H NMR (400
MHz, CDCl3): δ 9.18 (s, 2H), 9.11 (s, 2H), 8.33 (dd, J = 2.2, 7.8 Hz,
2H), 8.25−8.19 (m, 8H), 8.16−8.06 (m, 12H), 8.01−7.91 (m, 10H),
7.73 (dd, J = 8.7, 12 Hz, 4H), 1.57 (s, 9H), 1.56 (s, 9H), 1.52 (s, 18H).
13C NMR (100 MHz, CDCl3): δ 149.3, 149.1, 139.9, 138.4, 137.4,
135.9, 131.7, 131.3, 131.3, 131.0, 130.9, 130.9, 130.8, 130.6, 130.0,
129.5, 128.4, 128.2, 127.9, 127.9, 127.8, 127.6, 127.5, 127.3, 127.2,
125.8, 125.7, 125.3, 125.0, 124.9, 124.8, 124.5, 124.5, 123.8, 123.1,
123.0, 122.6, 122.5, 122.4, 122.4, 122.1, 35.2, 35.2, 31.9, 31.9. MALDI-
TOF-MS Calcd for C98H76: 1252.5947. Found: 1252.286. Anal. Calcd
for C98H76: C, 93.89; H, 6.11. Found: C, 93.55; H, 6.14.
Synthesis of (4-tert-Butylnaphthalen-1-yl)pinacolborane. To
a 1,4-dioxane solution (50 mL) of Pd(dppf)Cl2 (146 mg, 0.2 mmol)
and KOAc (1.12 g, 12 mmol) were added 1-bromo-4-tert-
butylnaphthalene (1.05 g, 4.0 mmol) and bis(pinacolato)diboron
(1.29 g, 4.8 mmol); the mixture was stirred for 3 h at 80 °C. The
solution was extracted with dichloromethane, and the extract was
washed with water, dried over MgSO4, and concentrated. The residues
were purified by silica gel column chromatography (ethyl acetate/
hexane 1/10) to afford the desired borane compound (1.15 g, 3.73
mmol, 93%) as a white solid. Mp: 140−146 °C. 1H NMR (400 MHz,
CDCl3): δ 8.82 (dd, J = 2.4, 7.6 Hz, 1H), 8.46 (dd, J = 2.0, 7.6 Hz,
1H), 7.99 (d, J = 7.6 Hz, 1H), 7.50−7.45 (m, 3H), 1.61 (s, 9H), 1.39
(s, 12H). 13C NMR (100 MHz, CDCl3): δ 149.6, 138.4, 135.4, 131.3,
129.8, 126.9, 125.0, 124.1, 122.4, 83.5, 36.1, 31.8, 24.9. HRMS Calcd
for C20H27BO2: 310.2104. Found: 310.2109.
Synthesis of 3,6,9,12-Tetrakis((triisopropylsilyl)ethynyl)-
chrysene (6e). Compound 5 (300 mg, 0.55 mmol), Pd(PPh3)4
(130 mg, 0.11 mmol), CuI (42 mg, 0.22 mmol), and PPh3 (58 mg,
0.22 mmol) were dissolved in a solution of piperidine (7.5 mL) and
triethylamine (22.5 mL); the mixture was stirred for 5 min. To this
mixture was added (triisopropylsilyl)acetylene (1.094 g, 6.00 mmol)
dropwise under a nitrogen atmosphere; the resulting solution was
heated to 80 °C for 8 h. After the solution was cooled to room
temperature, the solvent was removed under reduced pressure. The
residues were eluted through a long silica gel column (hexane) to give
compound 6e (151 mg, 0.16 mmol, 29%) as a white solid. Mp: >260
Synthesis of 3,6,9,12-Tetrakis(3,5-di-tert-butylphenyl)-
chrysene (6a). Nitrogen was bubbled through a mixed solution of
toluene (40 mL), EtOH (10 mL), and water (10 mL) for 30 min, and
to this solution were added compound 5 (875 mg, 1.61 mmol),
Pd(PPh3)4 (379 mg, 0.32 mmol), Na2CO3 (10.239 g, 96.60 mmol),
and 3,5-di-tert-butylphenylpinacolborane21 (3.055 g, 9.66 mmol). The
mixture was heated at 80 °C for 24 h. The solution was extracted with
hexane, concentrated, and purified by silica gel column chromatog-
raphy (dichloromethane/hexane 1/10) to afford compound 8a (427
1
°C. H NMR (400 MHz, CDCl3): δ 8.85 (s, 2H), 8.82 (s, 2H), 8.48
(d, J = 8.4 Hz, 2H), 7.78 (dd, J = 1.2, 8.4 Hz, 2H), 1.23−1.18 (m,
42H). 13C NMR (100 MHz, CDCl3): δ 131.4, 130.6, 129.4, 127.5,
127.0, 127.0, 126.8, 122.5, 121.2, 107.4, 104.9, 97.7, 92.5, 18.8, 18.7,
11.5, 11.4. MALDI-TOF-MS Calcd for C62H92Si4: 948.6276. Found:
948.547. Anal. Calcd for C62H92Si4: C, 78.41; H, 9.76. Found: C,
78.32; H, 9.69.
1
mg, 0.43 mmol, 27%) as a white solid. Mp: >350 °C. H NMR (400
MHz, CDCl3): δ 9.04 (d, J = 1.2 Hz, 2H), 8.79 (s, 2H), 8.21 (d, J = 8.6
Hz, 2H), 7.82 (dd, J = 1.6, 8.6 Hz, 2H), 7.60 (d, J = 1.8 Hz, 4H), 7.57
(d, J = 1.8 Hz, 4H), 7.55 (t, J = 1.8 Hz, 2H), 7.47 (t, J = 1.8 Hz, 2H),
1.43 (s, 36 H), 1.40 (s, 36 H). 13C NMR (100 MHz, CDCl3): δ 151.3,
150.8, 141.0, 140.5, 140.4, 139.9, 131.4, 130.2, 127.8, 127.5, 126.4,
124.8, 124.8, 122.2, 122.2, 121.6, 121.3, 35.1, 35.1, 31.7, 31.6. MALDI-
TOF-MS Calcd for C74H92: 980.7199. Found: 980.523. Anal. Calcd for
C74H92: C, 90.55; H, 9.45. Found: C, 90.47; H, 9.50.
Synthesis of 3,6,9,12-Tetrakis(4-tert-butylnaphthalen-1-yl)-
chrysene (6b). Compound 6b was prepared in a similar manner as 6a
from compound 5 (652 mg, 1.20 mmol) and (4-tert-butylnaphthalen-
1-yl)pinacolborane (2.23 g, 7.20 mmol) and was obtained as white
solid (172 mg, 0.18 mmol, 15%). Mp: >355 °C. 1H NMR (400 MHz,
CDCl3): δ 8.87 (s, 2H), 8.80 (s, 2H), 8.58 (d, J = 8.8 Hz, 2H), 8.50 (d,
J = 8.8 Hz, 2H), 7.97 (d, J = 8.4 Hz, 2H), 7.71−7.43 (m, 18H), 7.35−
7.29 (m, 4H), 1.72 (s, 18H), 1.64 (s, 18H). 13C NMR (100 MHz,
CDCl3): δ 146.2, 145.8, 139.6, 139.2, 138.1, 137.6, 134.5, 133.2, 131.7,
131.7, 131.5, 130.6, 128.9, 128.3, 127.9, 127.6, 127.5, 127.5, 127.2,
127.1, 127.1, 126.8, 124.8, 124.8, 124.4, 124.3, 123.2, 122.9, 122.8,
36.1, 36.0, 32.0, 31.9. MALDI-TOF-MS Calcd for C74H68: 956.5321.
Found: 956.497. Anal. Calcd for C74H68: C, 92.84; H, 7.16. Found: C,
92.46; H, 7.20.
Synthesis of 3,6,9,12-Tetrakis((3,5-di-tert-butylphenyl)-
ethynyl)chrysene (6f). Compound 5 (250 mg, 0.46 mmol),
Pd(PPh3)4 (107 mg, 0.09 mmol), CuI (34 mg, 0.18 mmol), and
PPh3 (47 mg, 0.18 mmol) were dissolved in a solution of piperidine (6
mL) and triethylamine (18 mL); the mixture was stirred for 5 min. To
this mixture was added 1,3-di-tert-butyl-5-ethynylbenzene24 (887 mg,
4.14 mmol) dropwise under a nitrogen atmosphere; the resulting
solution was heated to 80 °C for 8 h. The resulting solution was
cooled to room temperature, and the solvent was removed under
reduced pressure. The residues were eluted through an alumina
column (hexane) to give compound 6f (108 mg, 0.10 mmol, 22%) as a
1
yellow solid. Mp: >280 °C. H NMR (400 MHz, CDCl3): δ 9.03 (s,
2H), 9.02 (s, 2H), 8.60 (d, J = 8.4 Hz, 2H), 7.89 (d, J = 8.4 Hz, 2H),
7.58 (d, J = 1.7 Hz, 4H), 7.50 (d, J = 1.7 Hz, 4H), 7.48 (s, 2H), 7.44
(s, 2H), 1.39 (s, 36H), 1.36 (s, 36H). 13C NMR (100 MHz, CDCl3): δ
151.1, 151.0, 131.1, 129.9, 129.7, 127.6, 127.2, 127.0, 126.3, 126.1,
126.1, 123.3, 123.0, 122.6, 122.1, 122.0, 121.2, 96.6, 92.0, 88.7, 86.6,
34.9, 34.9, 31.4, 31.4. MALDI-TOF-MS Calcd for C82H92: 1076.7199.
Found: 1076.755. Anal. Calcd for C82H92: C, 91.39; H, 8.61. Found: C,
91.51; H, 8.32.
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Synthesis of 3,6,9,12-Tetrakis(bis(4-tert-butylphenyl)-
amino)chrysene (6g). Compound 5 (212 mg, 0.39 mmol), bis(4-
tert-butylphenyl)amine25 (545 mg, 1.93 mmol), potassium tert-
butoxide (263 mg, 2.34 mmol), Pd(OAc)2 (2 mg, 0.004 mmol), and
P(tBu)3 (6 mg, 0.02 mmol) in dry toluene (15 mL) were stirred under
an argon atmosphere at 100 °C for 12 h. The resulting solution was
cooled to room temperature and extracted with dichloromethane. The
extract was dried over MgSO4, concentrated under reduced pressure,
and purified on an alumina column to afford 6g (108 mg, 0.08 mmol,
20%) as a yellow solid. Mp: >370 °C. 1H NMR (400 MHz, CD2Cl2): δ
8.10 (d, J = 2.1 Hz, 2H), 7.99 (s, 2H), 7.89 (d, J = 9.0 Hz, 2H), 7.28−
7.25 (m, 8H), 7.20−7.14 (m, 10H), 7.06−7.02 (m, 8H), 6.96−6.92
(m, 8H), 1.29 (s, 36H), 1.27 (s, 36H). 13C NMR (100 MHz, CD2Cl2):
δ 147.4, 146.8, 145.9, 145.2, 144.4, 142.1, 133.7, 128.2, 126.7, 126.6,
126.2, 126.1, 124.7, 123.7, 121.3, 120.9, 115.2, 34.6, 34.4, 31.6, 31.6.
MALDI-TOF-MS Calcd for C98H112N4: 1344.8887. Found: 1344.874.
Anal. Calcd for C98H112N4: C, 87.45; H, 8.39; N, 4.16. Found: C,
87.14; H, 8.41; N 4.09.
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(18) This OLED device without dopant 6g showed a maximum
brightness of 16 399 cd m−2, a turn-on voltage of 3.3 eV, and CIE (x,
y) = (0.16, 0.10), indicative of a deep-blue color.
ASSOCIATED CONTENT
* Supporting Information
■
S
NMR spectra, MALDI-TOF mass spectra, photoelectron
spectra, CV measurements of new compounds, and X-ray
crystallographic data for compound 6a. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: rsliu@mx.nthu.edu.tw.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The Ministry of Economy Affairs and the National Science
Council, Taiwan, provided financial support of this work. The
National Center for High-Performance Computing (u32chc04)
of Taiwan provided computing time.
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