Side substituent dependence of photophysical properties of 9-arylanthracene-based π-conjugates

Article abstract of DOI:10.1246/bcsj.20140178

Three new 9-arylanthracene-based π-conjugated derivatives with different side substituent (methyl, methoxy, and hexyloxy) were synthesized using Heck coupling/ HornerEmmons reaction in good yields (7278%) and their photophysical properties investigated. T

Full text of DOI:10.1246/bcsj.20140178

Side Substituent Dependence of Photophysical Properties
of 9-Arylanthracene-Based π-Conjugates
Debabrata Jana and Binay K. Ghorai*
Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711 103, India
E-mail: binay@chem.becs.ac.in
Received: June 19, 2014; Accepted: August 25, 2014; Web Released: September 8, 2014
Three new 9-arylanthracene-based π-conjugated derivatives with different side substituent (methyl, methoxy,
and hexyloxy) were synthesized using Heck coupling/Horner-Emmons reaction in good yields (72-78%) and their
photophysical properties investigated. The dependence of the photophysical properties on the side substituent methyl,
methoxy, and hexyloxy has been discussed. The absorption maxima of the synthesized compounds in the solution possess
similar absorption bands located at 420-423 nm. They are shown to be thermally stable and emit light in sky blue region
(ca. 490 nm) in solution. Photoluminescence measurements show a 25-28 nm red shift between solution and powdered
states indicated some aggregation in the solid state. The results of cyclic voltammetry measurements of the compounds
show good reversibility, indicating that the compounds have good electrochemical stability.
Anthracene-based π-conjugates have received considerable
interest in both academic research and industrial applications
due to their good electrochemical properties, thermal proper-
ties, and ease of modification at its 9- and 10-positions.
Recently, Yoshizawa and co-workers1 reviewed anthracene-
based assemblies and their intrinsic photophysical, photo-
chemical, and chemical properties. These materials are poten-
tial candidates as active materials for blue OLED,2 fluorescent
biosensors,3 chem-sensors,4 OFET devices,5 solar cell,6 liquid
crystals,7 and supramolecular chemistry.8 The planar structure
of anthracene moiety quenched the fluorescence efficiency in
the solid state due to intermolecular π-π stacking interaction,
which hampers its application in OLEDs. To mitigate these
problems, several deep-blue anthracene derivatives have been
synthesized by introducing aryl groups at the 9- and 10-
positions. For example, Kim and co-workers9 reported the
synthesis of 9,10-diphenylanthracne-based blue-emitting mate-
rials. Kobayashi and co-workers10 prepared alkylene-strapped
diphenylanthracene-based oligomers used as solid-state blue-
emitting material. Kwon and co-workers11 fabricated deep-blue
OLEDs using anthracene derivatives bearing multi-phenyl-
based bulky substituent in 9,10-positions as emitters.
The nonplanar structure of 9,10-aryl-substituted anthracene
can prevent excimer or exciplex formation resulting in high
fluorescence quantum efficiency in dilute solution.12 Partic-
ularly, in 9-, and 10-aryl-substituted anthracene, the benzene
ring is rotated out of the plane of the anthracene moiety because
of the steric interactions between the 1,8-hydrogens of the
anthracene and the 2,6-hydrogens of the aryl group.13 The
nonplanar configuration of 9-, and 10-aryl-substituted anthra-
cene unit decreases conjugation resulting in a low lying highest
occupied molecular orbital (HOMO).14 Therefore, it is neces-
sary to improve electron-donating ability of blue-emitting
materials for display or lighting applications. In our recent
papers, the synthesis and optical properties of a few blue-
emitting materials were reported.15 This manuscript focuses on
the synthesis of 9-aryl-substituted anthracene-based π-conju-
gated derivatives and also their optical and electrochemical
properties.
Results and Discussion
Synthesis. The synthetic procedures for the preparation
of arylanthracene derivatives 7-9 and the core, diethyl [4-
(diethoxyphosphorylmethyl)-2,5-bis(dodecyloxy)benzyl]-
phosphonate (11) used in this study are depicted in Scheme 1.
Arylanthracene derivatives 1-3 were obtained in 79-85% yield
from the reaction of anthrone with arylmagnesium bromide
under refluxing conditions followed by removal of a water
molecule from the resulting tertiary alcohol with formic acid.
Formylation of 1-3 with phosphorus oxychloride and dime-
thylformamide at 90 °C gave aldehyde derivatives 4-6 in good
yield. Wittig reaction of aldehydes 4-6 with methyltriphenyl-
phosphonium bromide and n-BuLi at ¹20 °C afforded vinyl-
arylanthracene derivatives 7-9 in 70-75% yield. Diphos-
phonate 11 can be readily prepared from hydroquinone in a
three-step procedure. Reaction of hydroquinone with 1-bromo-
dodecane in DMSO in the presence of KOH resulted in 1,4-
bis(dodecyloxy)benzene, which on treatment with concen-
trated HBr (48% aq.) and paraformaldehyde to give a benzyl
bromide derivative 10. Reaction of 10 with P(OEt)3 afforded
diphosphonate 11 in good yield.
The synthetic strategy employed for the synthesis of com-
pounds 13-15 was based on the Horner-Wadsworth-Emmons
reaction (HWE)/Heck coupling as outlined in Scheme 2.
Conjugated derivatives 13-15 can be readily synthesized from
1,4-dibromo-2,5-bis(dodecyloxy)benzene (12)16 using double-
fold palladium-catalyzed Heck cross-coupling with vinyl-
arylanthracene derivatives 7-9. However, the double-fold Heck
coupling strategy seemed to be unsuitable for the synthesis of
13-15 because the reaction yield is very poor (12-16%) due to
Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan | 89

R
R
R
O
i
ii
iii
CHO
1, R = CH3, 85%
2, R = OCH3, 82%
3, R = OC6H13, 79%
4, R = CH3, 72%
5, R = OCH3, 75%
6, R = OC6H13, 76%
7, R = CH3, 72%
8, R = OCH3, 70%
9, R = OC6H13, 75%
OC12H25
OC12H25
OC12H25
v
(EtO)2OP
iv
Br
PO(OEt)2
OC12H25
Br
OC12H25
62%
65%
OC12H25
10
11
Scheme 1. Reagents and conditions: (i) ArMgBr, THF, reflux, 1 h; then HCO2H, reflux, 15 min.; (ii) POCl3, DMF, 90 °C, 4 h;
¹
(iii) Ph3P+CH3Br , n-BuLi, THF, ¹20 °C to rt, 6 h; (iv) 48% (aqueous) HBr, HOAc, (CH2O)n, reflux; (v) P(OEt)3, reflux.
H3C
O C12H25
4, i
7, ii
72%
12%
O
C12H25
CH3
13
H3CO
O C12H25
O C12H25
Br
5, i
8, ii
11
15%
Br
O
76%
C12H25
O
C12H25
12
OCH3
14
C6H13
O
6, i
9, ii
O C12H25
78%
16%
O
C12H25
OC6H13
15
t
Scheme 2. Synthesis of 9-arylanthracene-based conjugated compounds 13-15. Reagents and conditions: (i) BuOK, THF, rt, 12 h;
then catalytic I2, toluene, reflux, 48 h; (ii) Pd(OAc)2, P(o-tol)3, n-Bu4NBr, KOAc, DMF, 100 °C, 16 h.
90 | Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan

the insolubility of mono-fold coupled intermediates, which
were observed to precipitate from solution during early reaction
times. The yield of desired conjugates was improved to 70%
with the HWE reaction, in which 11 is treated with aldehyde
derivatives 4, 5, and 6 afforded a mixture of cis- and trans-
isomers of 13, 14, and 15. In order to get all trans product, a
catalytic isomerization of the mixtures was performed in the
presence of iodide in toluene. The newly synthesized 9-
arylanthracene-based conjugates 13-15 were characterized with
1H NMR, MALDI-MS, elemental analysis and found to be in
good agreement with their structures. The dodecyloxy side
chain is attached to the 2- and 5-positions of the central
benzene ring to enhance the solubility in organic solvents as
well as the electron-donating ability of the compounds.
emission band at ca. 490 nm. The broad emission is attributed
to the aggregation formation in the excited state due to the
presence of planar π-conjugated anthracene backbone. The
fluorescence quantum yields (Φfl) of 13, 14, and 15 are 40,
25, and 24% respectively in tetrahydrofuran. Low fluorescent
quantum yield indicates significant aggregation in the excited
state. It has been observed that onset PL emission slightly red
shifted from 13 to 15 indicates minor change in conjugation
effect in the molecular framework. Compound 15 has lower Φfl
value and red-shifted emission, which implies hexyloxy side
chain restricted the rotation of phenyl group resulting in more
1.0x106
8.0x105
Optical Properties. The UV-vis absorption spectra of the
new conjugated 9-arylanthracene compounds 13-15 in THF
are shown in Figure 1 and the data are collected in Table 1.
The absorption band at a shorter wavelength (ca. 292 nm) is
attributed to the localized π-π* transition of the 9-arylanthra-
cene chromophore. The broad absorption band appears at 420-
424 nm and possesses a high extinction coefficient (5.37 © 104
13
14
15
6.0x105
4.0x105
¹1
¹1
¹1 cm for 13, 5.61 © 104 M¹1 cm for 14, and 4.64 © 104
2.0x105
0.0
M
M
¹1 cm¹1 for 15) is due to the more delocalized π-π* transition
originating from 1,4-bis(dodecyloxy)benzenevinylene-bridged
9-arylanthracene unit. The PL spectra for 13-15 in tetra-
hydrofuran are shown in Figure 2a and the data are summa-
rized in Table 1. All compounds in this study are fluorescent
active. The color of fluorescence of 13-15 ranges from blue
to sky blue. The PL spectra of 13-15 (excited at 420 nm) show
a sharp emission band at ca. 450 nm and a shoulder broad
450
500
550
600
650
700
Wavelength/nm
(a)
1.0
0.8
0.6
0.4
0.2
13
14
15
13
1.0x105
14
15
13
14
8.0x104
15
6.0x104
4.0x104
2.0x104
0.0
450
500
550
600
650
Wavelength/nm
(b)
300
350
400
450
500
Figure 2. (a) Photoluminescence spectra of compounds 13-
15 (-ex = 420 nm) in tetrahydrofuran (C = 1.0 © 10¹6 M)
and (b) normalized photoluminescence spectra of com-
pounds 13-15 (-ex = 420 nm) in powdered state.
Wavelength/nm
Figure 1. Absorption spectra of compounds 13-15 in tetra-
hydrofuran (C = 1.0 © 10¹6 M).
Table 1. Photophysical Properties of Compounds 13-15
e)
UV-vis
/nm
PL/nm
THF/powdera)
Eox(onset)
/eV
HOMOc)
/eV
LUMOc)
/eV
¦Ed)
/eV
Td
Compd
Φ%b)
/°C
13
14
15
292, 420
292, 422
294, 423
489/515
492/518
495/523
40
25
24
0.80
0.68
0.49
¹5.46
¹5.34
¹5.15
¹2.51
¹2.41
¹2.22
2.95
2.93
2.93
335
365
320
a) Measured in powdered state. b) Fluorescence quantum yields (Φ), measured in dichloromethane solution using
pyrene (Φfl = 0.32, in CH2Cl2) as standard, excited at 275 nm. c) HOMO = ¹[Eox(onset) + 4.66 eV]; LUMO =
HOMO + ¦E. d) ¦E = HOMO-LUMO gap; Estimated from the onset of the absorption spectra: 1240/-onset
.
e) Decomposition temperature (Td, 5% weight loss) obtained from thermogravimetric analysis (TGA).
Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan | 91

4
3
2
1
0
1.0
0.8
0.6
0.4
0.2
0.0
1.0 x 10-4 M in THF
0.5 x 10-4 M in THF
1.0 x 10-5 M in THF
0.5 x 10-5 M in THF
10-4
10-3
10-2
M
M
M
13
Φ = 13%
Φ = 9.4%
Φ = 1.2%
550
450
500
600
650
300
400
500
600
Wavelength/nm
Wavelength/nm
(a)
Figure 3. Absorption spectra of compound 13 in tetra-
hydrofuran with different concentration.
1.0
0.8
0.6
0.4
0.2
0.0
10-4
10-3
10-2
M
M
M
planar architecture than 14 (methoxy side chain) and 13
(methyl side chain). The planarity of compounds 13-15 have
been attenuated due to the presence of side chain methyl,
methoxy, and hexyloxy group on the 9-arylanthracene moiety.
The more planar structure of 15 induces more aggregation in
excited state. As a result, the Φfl values are arranged in the order
of 13 > 14 > 15. The emission spectra are also measured in
the powdered state of the compounds. The peak values are
presented in Table 1 and displayed in Figure 2b. Compounds
13, 14, and 15 exhibited red-shifted (ca. 30 nm) emission in the
powdered state compared to those observed in THF solutions.
Moreover, these derivatives show a red shifted broad peak
in the powdered state at around 520 nm indicating molecular
aggregation or excimer formation in the solid state.17 For
understanding the aggregation behavior in the ground state,
Φ = 15%
Φ = 6%
Φ = 1%
450
500
550
Wavelength/nm
(b)
600
650
the absorption property of compound 13 was studied in tetra-
¹5
hydrofuran at different concentrations (0.5 © 10
to 1 ©
0.6
0.4
0.2
0.0
10-4
10-3
10-2
M
M
M
10¹4 M) as shown in Figure 3. The spectra show that the
absorbance increases with concentration. When the concen-
tration increased from 0.5 © 10 to 1 © 10¹4 M, the UV
¹5
Φ = 10%
absorption maximum wavelength of 13 red-shifted from 420
to 428 nm (an 8-nm red shift), indicating the formation of J-
aggregates.18 This result indicates that the compound 13 has a
tendency to form aggregates at higher concentration solution.
We also examined the aggregation behavior of 13-15 in excited
state, the PL of their concentrated solutions (10¹4-10¹2 M) was
studied as shown in Figures 4a-4c. When the concentration
Φ = 5%
Φ = 0.82%
500 550
¹4
was increased from 10 to 10¹2 M, the PL intensity and also
450
600
650
quantum yield (Φfl) of oligomers were decreased. For oligomer
13, the Φfl decreases (13% to 1.2%) with increasing concen-
Wavelength/nm
¹4
tration (10 to 10¹2 M) and the maximum emission bands
(c)
showed red shifts from 489 to 507 nm (an 18-nm red shift). The
PL emission spectra of oligomers 14 and 15 also showed red
Figure 4. Normalized photoluminescence spectra of (a)
compound 13 (-ex = 420 nm), (b) 14 (-ex = 420 nm), and
(c) 15 (-ex = 420 nm) in tetrahydrofuran with different
concentration.
¹4
shifts in higher concentrated (10 to 10¹2 M) solution from
492 to 506 nm (a 14-nm red shift) and 495 to 516 nm (a 21 nm
shift) with decrease Φfl value (15% to 1% for 14; 10% to 0.82%
for 15) respectively.
decomposition (Td) temperatures (5% weight loss in nitrogen
atmosphere) were observed in the range of 320 to 365 °C.
These compounds exhibit moderate thermal stabilities. The
decomposition temperatures with 5% weight loss under N2
Thermal Stabilities.
The thermal properties of the 9-
arylanthracene derivatives 13-15 were studied by thermogra-
vimetric analysis (TGA) and presented in Table 1. The thermal
92 | Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan

is located at 0.80, 0.68, and 0.49 V respectively. The HOMO
levels were calculated by using the known equation HOMO =
¹(Eox(onset) + 4.66 eV).19 The calculated HOMO values are
in the range of ¹5.46 to ¹5.15 eV. Calculating the HOMO-
LUMO gap (measured from the absorption maxima), the
LUMO levels are found to be ca. 2.22-2.51 eV. The HOMO-
LUMO gaps (Eg) of 13-15 are 2.95, 2.93, and 2.93 eV,
respectively. From this observation, it is clear that the aryl
substituent at 9-position of anthracene moiety have signifi-
cantly impact on HOMO and LUMO energy level, but little
influence on HOMO-LUMO gaps. 9-Aryl-substituted anthra-
cene is partially conjugated because of sterically unfavorable
nonplanar conformation between the aryl ring and the anthra-
cene skeleton. The electron-donating ability (HOMO energy
level) of 14 and 15 is significantly increased compared to 13
suggesting that the 9-p-tolyl group in 13 significantly rotated
with respect to the anthracene moiety. Interestingly, it was
found that the HOMO value for 15 (OC6H13) is higher than that
of 14 (OCH3) demonstrating that the cation is more stabilized
by the delocalized π-system in 15 (hexyloxy side chain) than 14
(methoxy side chain). This can be explained by the fact that the
aryl substituent at the 9-position of anthracene moiety does not
favor electronic communication probably due to the greater
distortion from planarity in 14 than in 15. The results of CV
measurements of synthesized conjugates show good reversi-
bility, indicating that compounds have good electrochemical
stability. The HOMO levels (5.46-5.15 eV) lying between
those of tris(8-hydroxyquinoline)aluminum (Alq3) (5.80 eV)
and indium tin oxide (ITO) (4.80 eV), suggests these com-
pounds may act as a hole-transporting materials (HTL).
13
14
15
100
80
60
40
20
100
200
Temperature/°C
Figure 5. TGA curves for compounds 13-15 in nitrogen at
300
400
500
¹1
a heating rate of 10 °C min
.
4.0x10-5
13
14
15
2.0x10-5
0.0
-2.0x10-5
0.0
0.4
0.8
Potential/V
1.2
1.6
Experimental
General.
All melting points are uncorrected. Unless
otherwise noted, all reactions were carried out under an inert
atmosphere in flame dried flasks. Solvents obtained from
Spectrochem were dried and purified by distillation before use
as follows: tetrahydrofuran and toluene from sodium benzo-
phenone ketyl; dichloromethane from P2O5; DMF from CaH2;
triethylamine from solid KOH. After drying, organic extracts
were evaporated under reduced pressure and the residue was
column chromatographed on silica gel (Spectrochem, particle
size 100-200 mesh), using an ethyl acetate-petroleum ether
(60-80 °C) mixture as eluent unless specified otherwise.
Hydroquinone, anthrone, 4-bromotoluene, 4-bromoanisole,
methcyltriphenylphosphonium bromide, palladium(II) acetate
[Pd(OAc)2] were purchased from Aldrich and used as received.
9-p-Tolylanthracene (1).13 To a stirred solution of anthrone
(1.0 g, 5.15 mmol) in THF (12 mL) was added dropwise a
solution of p-tolylmagnesium bromide in THF [prepared from
4-bromotoluene (1.40 g, 8.2 mmol) and magnesium (210 mg,
8.7 mmol) in 6 mL THF] at room temperature. The reaction
mixture was stirred at 60-70 °C for 2 h. After cooling to room
temperature, the reaction mixture was quenched with 10%
aqueous sulfuric acid solution (5 mL); the organic layer was
extracted with dichloromethane (2 © 15 mL). The combined
organic layer was washed with brine (10 mL) and dried over
anhydrous Na2SO4. The solvent was removed in a rotary
evaporator. The crude alcohol was treated with formic acid
(5 mL) and the mixture was refluxed for 15 min to complete the
Figure 6. Cyclic voltammetry of compounds 13-15
(ca. 1 mM) measured in 0.1 M n-Bu4NPF6-CH2Cl2, scan
¹1
rate 100 mV s
.
atmosphere (Td) for 13, 14, and 15 were 335, 365, and 320 °C,
respectively (Figure 5). The Td value of 15 exhibited lower
decomposition temperature attributed to the fragile hexyloxy
chains in the compound.
Cyclic Voltammetric Studies. The electrochemical behav-
ior of compounds 13-15 was investigated by cyclic voltam-
metric measurements using a three-electrode cell. The working
electrode was a glassy carbon, the auxiliary electrode was a
Pt wire, and Ag/Ag+ was used as reference electrode. Tetra-
butylammonium hexafluorophosphate (0.1 M) was used as the
supporting electrolyte in dry dichloromethane. The redox
potentials were calibrated by using ferrocene as an internal
standard. The cyclic voltammograms measured for the com-
pounds 13-15 are presented in Figure 6 and the data are listed
in Table 1. Compounds 13, 14, and 15 exhibit three successive
quasi-reversible anodic oxidations (0.94, 1.27, and 1.49 V for
13; 0.80, 1.05, and 1.34 V for 14; 0.62, 1.01, and 1.25 V for
15). The first redox wave may be attributed to the oxidation
of the central 1,4-bis(dodecyloxy)benzene segment, while the
second and third redox waves most likely stem from the
oxidation of the peripheral 9-arylanthracene-conjugated seg-
ment. The onset oxidation potential of the compounds 13-15
Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan | 93

dehydration. After cooling to room temperature, water (15 mL)
was added and extracted with diethyl ether (2 © 10 mL). The
ether solution was washed with water (10 mL) and dried over
anhydrous Na2SO4. Solvent was removed in a rotary evaporator.
Purification by column chromatography using hexane as eluent
afforded compound 1 (1.17 g, 85%) as white solids.
Mp 128 °C; IR (KBr, cm¹1): 2956, 2934, 1675, 1604;
1H NMR (300 MHz, CDCl3): ¤ 11.54 (s, 1H), 8.99 (d, 2H,
J = 9.0 Hz), 7.75 (d, 2H, J = 8.7 Hz), 7.64 (ddd, 2H, J = 9.0,
6.6, 1.2 Hz), 7.45-7.35 (m, 2H), 7.29 (d, 2H, J = 8.7 Hz), 7.12
(d, 2H, J = 8.7 Hz), 3.94 (s, 3H); 13C NMR (75 MHz, CDCl3):
¤ 193.2, 159.3, 145.4, 131.7, 131.6, 130.1, 130.0, 128.5, 128.0,
125.3, 124.7, 123.3, 113.8, 55.3; Anal. Calcd for C22H16O2: C,
84.59; H, 5.16%. Found: C, 84.58; H, 5.18%.
9-(4-Methoxyphenyl)anthracene (2).
The synthetic
procedure used was similar to that described for 1. Starting
from anthrone (1.0 g, 5.15 mmol), 1-bromo-4-methoxybenzene
(1.53 g, 8.2 mmol) and magnesium (210 mg, 8.7 mmol) com-
pound 2 (1.19 g, 82%) was obtained as a white solid.
Mp 126-128 °C; IR (KBr, cm¹1): 3058, 2998, 2964, 1600;
1H NMR (300 MHz, CDCl3): ¤ 8.44 (s, 1H), 8.00 (d, 2H, J =
8.4 Hz), 7.77-7.67 (m, 2H), 7.42 (t, 2H, J = 8.1 Hz), 7.40-7.28
(m, 4H), 7.13-7.03 (m, 2H), 3.90 (s, 3H); 13C NMR (75 MHz,
CDCl3): ¤ 159.0, 136.8, 132.3, 131.4, 130.8, 130.5, 128.3,
126.9, 126.4, 125.2, 125.0, 113.8, 55.3; Anal. Calcd for
C21H16O: C, 88.70; H, 5.67%. Found: C, 88.68; H, 5.68%.
10-(4-Hexyloxyphenyl)anthracene-9-carbaldehyde
(6).
The synthetic procedure used was similar to that described for
4. Starting from 9-(4-hexyloxyphenyl)anthracene (3) (2.88 g,
8.15 mmol), POCl3 (1.6 mL, 16.3 mmol), and DMF (20 mL),
compound 6 (2.36 g, 76%) was obtained as a yellow solid.
Mp 85 °C; IR (KBr, cm¹1): 2926, 2858, 1668, 1604;
1H NMR (300 MHz, CDCl3): ¤ 11.57 (s, 1H), 9.01 (d, 2H,
J = 9.0 Hz), 7.78 (d, 2H, J = 9.0 Hz), 7.65 (t, 2H, J = 7.5 Hz),
7.41 (t, 2H, J = 7.5 Hz), 7.32-7.20 (m, 2H), 7.12 (d, 2H, J =
8.4 Hz), 4.10 (t, 2H, J = 6.6 Hz), 1.89 (quin, 2H, J = 6.6 Hz),
1.55-1.50 (m, 2H), 1.49-1.30 (m, 4H), 0.94 (t, 3H, J = 6.6 Hz);
13C NMR (75 MHz, CDCl3): ¤ 193.3 (d), 159.0 (s), 145.6 (s),
131.7 (d), 130.2 (s), 129.8 (s), 128.5 (d), 128.1 (d), 125.3 (d),
124.7 (s), 123.4 (d), 114.4 (d), 68.1 (t), 31.6 (t), 29.3 (t), 25.8
(t), 22.6 (t), 14.0 (q); Anal. Calcd for C27H26O2: C, 84.78; H,
6.85%. Found: C, 84.75; H, 6.87%.
9-(4-Hexyloxyphenyl)anthracene (3).
The synthetic
procedure used was similar to that described for 1. Starting
from anthrone (1.0 g, 5.15 mmol), 1-bromo-4-hexyloxybenzene
(2.10 g, 8.2 mmol) and magnesium (210 mg, 8.7 mmol), com-
pound 3 (1.44 g, 79%) was obtained as a white solid.
1
Mp 53-55 °C; IR (KBr, cm¹1): 3042, 2934, 1608; H NMR
(300 MHz, CDCl3): ¤ 8.44 (s, 1H), 8.01 (d, 2H, J = 8.4 Hz),
7.72 (d, 2H, J = 8.4 Hz), 7.48-7.28 (m, 6H), 7.08 (d, 2H,
J = 7.2 Hz), 4.06 (t, 2H, J = 6.6 Hz), 1.95-1.80 (m, 2H), 1.55-
1.48 (m, 2H), 1.47-1.30 (m, 4H), 0.95 (t, 3H, J = 6.6 Hz);
13C NMR (75 MHz, CDCl3): ¤ 158.5, 136.9, 132.3, 132.2,
131.3, 130.5, 128.2, 126.9, 126.2, 125.1, 125.0, 114.3, 68.0,
31.6, 29.3, 25.8, 22.6, 14.0; Anal. Calcd for C26H26O: C, 88.09;
H, 7.39%. Found: C, 88.08; H, 7.41%.
9-p-Tolyl-10-vinylanthracene (7). To a stirred solution of
methyltriphenylphosphonium bromide (3.9 g, 10.9 mmol) in
THF (20 mL) was added n-BuLi (1.6 M in hexane) (5 mL, 10
mmol) at ¹20 °C. The reaction mixture was stirred for 0.5 h
at this temperature. A solution of 10-p-tolylanthracene-9-
carbaldehyde (4) (2.16 g, 7.32 mol) in THF (15 mL) was added
dropwise. The reaction mixture was allowed to come to room
temperature within 6 h. The mixture was quenched with
saturated NH4Cl solution (5 mL). The reaction mixture was
extracted with dichloromethane (50 mL) and dried over
anhydrous Na2SO4. The solvent was removed and purified
by column chromatography on silica gel (petroleum ether).
Compound 7 (1.54 g, 72%) was obtained as a white solid.
Mp 73-74 °C; IR (KBr, cm¹1): 3061, 2993, 2914, 2858,
1623; 1H NMR (300 MHz, CDCl3): ¤ 8.37 (d, 2H, J = 8.7 Hz),
7.68 (d, 2H, J = 8.7 Hz), 7.52 (dd, 1H, J = 17.7, 11.4 Hz),
7.48-7.30 (m, 8H), 6.04 (dd, 1H, J = 11.4, 1.8 Hz), 5.65 (dd,
1H, J = 17.7, 1.8 Hz), 2.52 (s, 3H); 13C NMR (75 MHz,
CDCl3): ¤ 136.9 (s), 135.9 (s), 133.8 (d), 133.5 (s), 131.1
(d), 130.0 (s), 129.0 (d), 128.8 (s), 127.2 (d), 126.0 (d), 125.0
(d), 124.9 (d), 122.9 (t), 21.3 (q); Anal. Calcd for C23H18: C,
93.84; H, 6.16%. Found: C, 93.83; H, 6.17%.
10-p-Tolylanthracene-9-carbaldehyde (4).
POCl3 (1.6
mL, 16.3 mmol) was added slowly to dry DMF (20 mL) at 0 °C
with intensive stirring under argon atmosphere. After stirring
for 15 min, the reaction mixture was allowed to come to room
temperature. 9-p-Tolylanthracene (1) (2.18 g, 8.15 mmol) was
added slowly and the reaction mixture was stirred at 90-100 °C
for 3 h. After cooling to room temperature, the mixture was
poured into a mixture of water (100 mL) and ice (50 g), then
neutralized with a 20% aqueous solution of sodium carbonate.
A pale yellow precipitate was collected by filtration, washed
with cold water and 20% aqueous ethanol. The crude product
was purified by column chromatography on silica gel (petro-
leum ether/EtOAC:4/1) to afford 4 (1.73 g, 72%) as a light
yellow solid.
Mp 138 °C; IR (KBr, cm¹1): 2914, 2861, 1679, 1612;
1H NMR (300 MHz, CDCl3): ¤ 11.58 (s, 1H), 9.00 (d, 2H,
J = 9.0 Hz), 7.74 (d, 2H, J = 9.0 Hz), 7.65 (ddd, 2H, J = 9.0,
6.6, 1.3 Hz), 7.44-7.36 (m, 4H), 7.29-7.24 (m, 2H), 2.53
(s, 3H); 13C NMR (75 MHz, CDCl3): ¤ 193.3, 145.8, 137.7,
135.1, 131.7, 130.5, 130.0, 129.1, 128.6, 128.1, 125.4, 124.8,
123.4, 21.4; Anal. Calcd for C22H16O: C, 89.16; H, 5.44%.
Found: C, 89.13; H, 5.47%.
9-(4-Methoxyphenyl)-10-vinylanthracene (8). The syn-
thetic procedure used was similar to that described for the
preparation of 7. Starting from 10-(4-methoxyphenyl)anthra-
cene-9-carbaldehyde (5) (1.0 g, 3.20 mmol), vinyl compound 8
was obtained as a white solid (695 mg, 70%).
Mp 102 °C; IR (KBr, cm¹1): 3065, 3001, 2952, 2835, 1608;
1H NMR (300 MHz, CDCl3): ¤ 8.03 (d, 2H, J = 8.7 Hz), 7.62
(d, 2H, J = 8.7 Hz), 7.48 (dd, 1H, J = 17.6, 11.4 Hz), 7.48-
7.41 (m, 2H), 7.37-7.30 (m, 4H), 7.14-7.08 (m, 2H), 6.04 (dd,
1H, J = 11.4, 2.1 Hz), 5.67 (dd, 1H, J = 17.6, 2.1 Hz), 3.94
(s, 3H); 13C NMR (75 MHz, CDCl3): ¤ 159.0 (s), 136.7 (s),
133.9 (d), 133.6 (s), 132.4 (d), 131.1 (s), 130.3 (s), 129.0 (s),
127.3 (d), 126.1 (d), 125.1 (d), 125.0 (d), 123.1 (t), 113.9 (d),
10-(4-Methoxyphenyl)anthracene-9-carbaldehyde
(5).
The synthetic procedure used was similar to that described
for 4. Starting from 9-(4-methoxyphenyl)anthracene (2) (2.31 g,
8.15 mmol), POCl3 (1.6 mL, 16.3 mmol), and DMF (20 mL),
compound 5 (1.90 g, 75%) was obtained as a yellow solid.
94 | Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan

55.4 (q); Anal. Calcd for C23H18O: C, 89.00; H, 5.85%. Found:
C, 88.97; H, 5.87%.
Route II: To a stirred solution of 11 (100 mg, 0.133 mmol)
in THF (12 mL) under argon atmosphere at 0 °C, BuOK (45
t
9-(4-Hexyloxyphenyl)-10-vinylanthracene (9). The syn-
thetic procedure used was similar to that described for the
preparation of 7. Starting from 10-(4-hexyloxyphenyl)anthra-
cene-9-carbaldehyde (6) (1.0 g, 2.61 mmol), vinyl compound 9
was obtained as a white solid (745 mg, 75%).
Mp 76 °C; IR (KBr, cm¹1): 3073, 2922, 2855, 1608;
1H NMR (300 MHz, CDCl3): ¤ 8.37 (d, 2H, J = 8.7 Hz), 7.71
(d, 2H, J = 8.7 Hz), 7.52 (dd, 1H, J = 17.7, 11.4 Hz), 7.48-
7.27 (m, 6H), 7.10 (d, 2H, J = 8.7 Hz), 6.05 (dd, 1H, J = 11.4,
1.8 Hz), 5.66 (dd, 1H, J = 17.7, 1.8 Hz), 4.09 (t, 2H, J =
6.6 Hz), 1.88 (quin, 2H, J = 6.6 Hz), 1.60-1.50 (m, 2H), 1.48-
1.32 (m, 4H), 0.94 (t, 3H, J = 6.9 Hz); 13C NMR (75 MHz,
CDCl3): ¤ 158.5 (s), 136.7 (s), 133.9 (d), 133.5 (s), 132.3 (d),
130.8 (s), 130.2 (s), 128.9 (s), 127.3 (d), 126.0 (d), 124.9 (d),
124.8 (d), 122.9 (t), 114.3 (d), 68.1 (t), 31.6 (t), 29.3 (t), 25.8
(t), 22.6 (t), 14.0 (q); Anal. Calcd for C28H28O: C, 88.38; H,
7.42%. Found: C, 88.36; H, 7.43%.
1,4-Bis(bromomethyl)-2,5-bis(dodecyloxy)benzene (10).13
A mixture of 1,4-bis(dodecyloxy)benzene (1.0 g, 2.23 mmol),
paraformaldehyde (200 mg, 6.71 mmol), HOAc (6 mL), and
HBr (48% aqueous, 4 mL) was refluxed for 24 h; after cooling,
the precipitate was collected and washed with water. The
compound 10 was obtained as a white solid (917 mg, 65%) and
it was used for the next step without further purification.
Mp 65-67 °C; IR (KBr, cm¹1): 2918, 2851, 1509, 1472;
1H NMR (300 MHz, CDCl3): ¤ 6.85 (s, 2H), 4.52 (s, 4H), 3.98
(t, 4H, J = 6.3 Hz), 1.88-1.74 (m, 4H), 1.56-1.20 (m, 36H),
0.88 (t, 6H, J = 6.3 Hz).
mg, 0.401 mmol) was added at 0 °C. The reaction mixture was
stirred for 0.5 h at this temperature. A solution of 10-p-tolyl-
anthracene-9-carbaldehyde (4) (86 mg, 0.292 mmol) in THF
(15 mL) was added dropwise. The reaction mixture was stirred
at room temperature for 12 h. The mixture was poured into
water (50 mL) and extracted with dichloromethane (50 ml).
Solvent was removed and purified by column chromatography
on silica gel (petroleum ether) to afford yellow solid compound
13 (106 mg, 78%) as a mixture of cis- and trans-isomers.
To a solution of the compound 13 (100 mg, 0.096 mmol)
in toluene (5 mL) catalytic amount I2 (5 mg) was added and then
the mixture was refluxed for 72 h. After completion, the mix-
ture was extracted with dichloromethane (5 mL) and the organic
extracts were washed with sodium thiosulfate solution (5%,
5 mL), water (5 mL), brine (10 mL), and dried over anhydrous
sodium sulfate. Solvent was removed and the crude product was
purified by column chromatography (petroleum ether) affording
trans-isomer of 13 (92 mg, 92%) as a yellow solid.
Mp 132-134 °C; IR (KBr, cm¹1): 2922, 2847, 1604;
1H NMR (300 MHz, CDCl3): ¤ 8.52 (d, 4H, J = 8.7 Hz), 8.08
(d, 2H, J = 16.5 Hz), 7.73 (d, 4H, J = 8.7 Hz), 7.55-7.30 (m,
20H), 4.16 (t, 4H, J = 6.6 Hz), 2.54 (s, 6H), 1.84 (quin, 4H,
J = 6.6 Hz), 1.55-1.42 (m, 4H), 1.40-1.12 (m, 32H), 0.84
(t, 6H, J = 6.6 Hz); 13C NMR spectral data was not recorded
due to poor solubility; MALDI-TOF MS: m/z 1030.3 (M+,
100%). Anal. Calcd for C76H86O2: C, 88.49; H, 8.40%. Found:
C, 88.38; H, 8.41%.
Compound 14. The synthetic procedure used was similar
to that described for the preparation of 13.
For route I: Starting from 1,4-dibromo-2,5-bis(dodecyloxy)-
benzene (12) (120 mg, 0.198 mmol) and 9-(4-methoxyphenyl)-
10-vinylanthracene (8) (153 mg, 0.495 mmol), compound 14
was obtained as a yellow solid (32 mg, 15%).
For route II: Starting from 11 (100 mg, 0.133 mmol) and
10-(4-methoxyphenyl)anthracene-9-carbaldehyde (5) (103 mg,
0.332 mmol), and then isomerization in the presence of iodine,
compound 14 was obtained as a yellow solid (114 mg, 76%).
Mp 152-154 °C; IR (KBr, cm¹1): 3065, 2993, 2851, 1608;
1H NMR (300 MHz, CDCl3): ¤ 8.46 (d, 4H, J = 8.7 Hz), 8.02
(d, 2H, J = 16.8 Hz), 7.69 (d, 4H, J = 8.7 Hz), 7.43 (t, 4H,
J = 7.2 Hz), 7.39 (s, 2H), 7.38-7.24 (m, 10H), 7.09 (d, 4H,
J = 8.7 Hz), 4.11 (t, 4H, J = 6.3 Hz), 3.91 (s, 6H), 1.78 (quin,
4H, J = 6.3 Hz), 1.52-1.36 (m, 4H), 1.32-1.05 (m, 32H), 0.79
(t, 6H, J = 6.9 Hz); 13C NMR spectral data was not recorded
due to poor solubility; MALDI-TOF MS: m/z 1062.2 (M+,
100%); Anal. Calcd for C76H86O4: C, 85.83; H, 8.15%. Found:
C, 85.62; H, 8.17%.
Diethyl [4-(Diethoxyphosphorylmethyl)-2,5-bis(dodecyl-
oxy)benzyl]phosphonate (11). A mixture of compound 10
(1.0 g, 1.58 mmol) and triethyl phosphite (786 mg, 4.74 mmol)
was refluxed for 12 h, and then the excess triethyl phosphite
and volatile materials were removed by high vacuum pump.
The residue diphosphonate 11 (731 mg, 62%) was obtained as a
white solid and it was used directly without further purification.
Mp 43-45 °C; IR (KBr, cm¹1): 2914, 2847, 1521, 1476,
1
1393, 1272; H NMR (300 MHz, CDCl3): ¤ 6.91 (s, 2H), 4.03
(q, 4H, J = 7.2 Hz), 4.00 (q, 4H, J = 7.2 Hz), 3.91 (t, 4H, J =
6.6 Hz), 3.22 (d, 4H, J = 20.0 Hz), 1.85-1.69 (m, 4H), 1.45-
1.20 (m, 48H), 0.87 (t, 6H, J = 6.9 Hz); HRMS (ESI): Calcd
for C40H80NO8P2 [M + NH4]+: 764.5359, found: 764.5352.
Compound 13. Route I: A mixture of dried KOAc (56 mg,
0.576 mmol) and n-Bu4NBr (185 mg, 0.576 mmol) in DMF
(6 mL) was stirred for 15 min in a double necked round-
bottomed flask in argon atmosphere at room temperature. To
this reaction mixture, 1,4-dibromo-2,5-bis(dodecyloxy)benzene
(12)13 (120 mg, 0.198 mmol), P(o-tol)3 (17 mg, 0.057 mmol),
and 9-p-tolyl-10-vinylanthracene (7) (141 mg, 0.48 mmol) were
added simultaneously and stirred for another 15 min. Catalytic
amount of Pd(OAc)2 (10 mg) was added and heated for 48 h
at 100 °C. The mixture was cooled to room temperature and
extracted with dichloromethane (30 mL). The organic layer was
washed with water (3 © 5 mL), brine (5 mL), and dried over
anhydrous Na2SO4. Solvent was removed in a rotary evaporator
and the crude product was purified using column chromatog-
raphy (silica gel/ethyl acetate:petroleum ether: 5/95) to yield
compound 12 (24 mg, 12%) as pale yellow solids.
Compound 15. The synthetic procedure used was similar
to that described for the preparation of 13.
For route I: Starting from 1,4-dibromo-2,5-bis(dodecyloxy)-
benzene (12) (120 mg, 0.198 mmol) and 9-(4-hexyloxyphenyl)-
10-vinylanthracene (9) (188 mg, 0.495 mmol), compound 15
was obtained as a yellow solid (38 mg, 16%).
For route II: Starting from 11 (100 mg, 0.133 mmol) and
10-(4-hexyloxyphenyl)anthracene-9-carbaldehyde (6) (126 mg,
0.332 mmol), and then isomerization in the presence of iodine,
compound 15 was obtained as a yellow solid (134 mg, 78%).
Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan | 95

Mp 134-135 °C; IR (KBr, cm¹1): 3055, 2991, 2885, 1602;
1H NMR (300 MHz, CDCl3): ¤ 8.52 (d, 4H, J = 8.7 Hz), 8.30
(d, 2H, J = 16.8 Hz), 7.76 (d, 4H, J = 8.7 Hz), 7.49 (t, 4H,
J = 7.4 Hz), 7.42 (s, 2H), 7.44-7.32 (m, 10H), 7.13 (d, 4H,
J = 8.4 Hz), 4.16 (t, 4H, J = 6.6 Hz), 4.11 (t, 4H, J = 6.6 Hz),
1.98-1.81 (m, 8H), 1.55-1.32 (m, 8H), 1.30-1.12 (m, 40H),
0.95 (t, 6H, J = 6.9 Hz), 0.84 (t, 6H, J = 6.9 Hz); 13C NMR
spectral data was not recorded due to poor solubility; MALDI-
TOF MS: m/z 1202.3 (M+, 100%); Anal. Calcd for C86H106O4:
C, 85.81; H, 8.88%. Found: C, 85.73; H, 8.89%.
Y.-H. Kim, S.-K. Kwon, Dyes Pigm. 2012, 92, 1075. h) J.-A. Seo,
C.-W. Lee, M.-S. Gong, Dyes Pigm. 2013, 96, 211.
3
8547.
4
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Conclusion
In conclusion, we have reported the synthesis and photo-
physical properties of three new 9-arylanthracene-based π-
conjugates. Heck coupling and HWE olefination reaction are
two key steps in constructing the π-conjugated materials.
However, HWE olefination in the final step has been proven
more effective than the Heck coupling reaction. All materials
emit light in the blue to sky blue region. These compounds
were found to exhibit interesting photophysical properties
which dependent on the nature of the side substituent. Hence,
the long chain (hexyloxy)-substituted derivative 15 displayed
slightly red-shifted emissions and high HOMO values com-
pared to the methoxy- and methyl-substituted compound. The
comparatively low Φfl value of 15 attributed to the greater
aggregation-excimer formation in the excited state. Com-
pounds displayed red-shifted (ca. 30 nm) emission in the pow-
dered state compared to those observed in THF solutions due to
molecular aggregation or excimer formation in the solid state.
The HOMO levels of compounds lying between ITO (4.80 eV)
and Alq3 (5.80 eV) suggest that they can be used as a hole-
transporting material (HTL). All compounds enjoy moderate
thermal stability. Further studies addressing the electrolumi-
nescence of new 9-arylanthracene-based π-conjugated com-
pounds are currently underway in our laboratory.
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Financial support from CSIR [No. 02(0150)/13/EMR-II],
New Delhi is gratefully acknowledged.
Supporting Information
1H NMR spectra of new compounds 2-9, 11, 13-15 and
13C NMR spectra of 2-9. This material is available electroni-
cally on J-STAGE.
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96 | Bull. Chem. Soc. Jpn. 2015, 88, 89–96 | doi:10.1246/bcsj.20140178
© 2014 The Chemical Society of Japan