Synthesis and photophysical properties of conjugated quinolines

Article abstract of DOI:10.3184/030823409X465286

Aryl halides were prepared by condensation of 2-methylquinoline and bromo- or chloro-arylaldehydes in acetic anhydride. Diarylamines reacted with the aryl halides to afford novel triarylamine derivatives using Pd(OAch/P (o-tolylh as catalyst. These compou

Full text of DOI:10.3184/030823409X465286

JOURNAL OF CHEMICAL RESEARCH 2009
JULY, 427-429
RESEARCH PAPER 427
Synthesis and photophysical properties of conjugated quinolines
Voufeng Vue, Mingxin Vu* and Longguan Zhu
Department of Chemistry, Zhejiang University, Hangzhou, 310027, P.R. China
Aryl halides were prepared by condensation of 2-methylquinoline
anhydride. Diarylamines reacted with the aryl halides to afford novel triarylamine
(o-tolylh as catalyst. These compounds have potential as organic light-emitting
and bromo- or chloro-arylaldehydes
in acetic
derivatives using Pd(OAch/P
device materials and were
characterised by FT-IR, 'H NMR and elemental analyses. The UV-vis absorption and photoluminescent
spectra of
the compounds in CH2C12were investigated. The lowest absorption band of the triarylamine derivatives centred at
about 400 nm was assigned to a charge-transfer transition with an emission at 500-515 nm.
Keywords: triarylamine, aryl halides, quinoline, Pd-catalysed, organic light-emitting diodes
Considerable studies have been made on organic light-
emitting diodes (OLEDs) for their potential applications in
next generation full-colour displays as a promising alternative
to the conventional liquid crystal displays.!,2 Among OLED
materials, triarylamine derivatives have been widely
investigated for almost two decades because these compounds
have showed excellent thermal and electrochemical stability,
electron-donating ability, optoelectronic properties,3-s and
they are standard hole transport materials.6-8 Several carbazole
derivatives and diaminoanthracene derivatives are very
efficient both as hole transporters and green emitters.9,!0 There
has been a considerable effort in synthetic chemistry and most
triarylamine derivatives are obtained through palladium-
catalysed cross-coupling reactions involving formation of a
C-N single bond.
Based on our long standing studies in the field of organic
light-emitting devices9,!4 as well as in palladium-catalysed
coupling reactions, we have designed and synthesised
series of triarylamine derivatives with quinoline groups and
their UV-visible spectra (UV) and photoluminescence (PL)
properties have been studied. The reaction steps are outlined
in Scheme 1.
a
The target compounds were obtained by
a two-step
procedure. Aryl bromides or chlorides containing a quinoline
group were prepared by the reaction of 2-methylquinoline
and 4-bromobenzaldehyde or 4-chlorobenzaldehyde in acetic
anhydride at 150°C for 16 h. The yields were in the 60-70%
range. For the second step, diarylamines reacted with the
aryl bromides or chlorides to afford triarylamine derivatives
in the presence of the catalyst Pd(OAc)2!P(o-tolyl)3'
Standard conditions were 1.2 mmol aryl bromide or chloride,
1.0 mmol amine, 1.5 mmol sodium tert-butoxide, 0.05 mmol
palladium(II), and 0.15 mmol P(o-tolyl)3 in toluene at 1l0°C
for 8-24 h.
Novel green compounds combining both hole-transporting
triarylamines and electron-transporting quinoline groups
have attracted great attention. We chose triarylamines as the
building blocks due to their high hole-transporting mobility.!!-!3
I"'"
. 0
3a
0
6]Pd(OAc)2/L
H
r("yN_R
I""''''''
V
2
2a: R=methyl
R
X=CI, Br
x
1b:X=Br
2b: R=Phenyl
6
N-
2c: R=m-Tolyl
:
1
HN:::::::jPd(Ok}"'
2d: R=2-Naphthyl
~
4a
NI
Scheme 1
* Correspondent. E-mail: mingxinyu@css.zju.edu.cn

428
JOURNAL OF CHEMICAL RESEARCH 2009
Table
1
Physical properties of triarylamines
1.0
0.8
0.6
0.4
0.2
0.0
Entry
-0-2a
-o-2b
- 0 - 2 c
-v-2d
-*-3a
-'-4a
2a
2b
2c
2d
3a
4a
294,392
307,403
308,406
321,409
379
500
504
513
516
511
506
: i
~
~
'iii
<:
S
295, 401
.5
...J
"Maximum absorption wavelength in CH2CI2.
bMaximum emission wavelength in CH2CI2.
ll..
In order to investigate the photophysical
triarylamine derivatives, the UV and PL spectra (Table I) in
dilute dichloromethane solution were recorded. All compounds
properties of the
400
450
700
500
550
600
650
yield green emissions in solution at room temperature.
W avelength(nm )
As indicated in the absorption spectra Fig. I, the absorption
behaviours were quite similar to each other, and most of
them displayed two absorption peaks at about 300 nm and
400 nm (except 3a) which were ascribed to the absorption
Fig. 2 Photoluminescence spectra of novel compounds in
CH2CI2·
by the triarylamine moiety in a n-n* transition •. As Table
shows, when R is 2-naphthyl (2d), the absorption maximum
was redshifted by 17nm compared to when R is methyl (2a),
which showed that there was obvious n-n* delocalisation
with the increase in benzene rings present.
I
spectrophotometer. Vibrational transition frequencies are reported
in wave numbers (cm-I). Elemental analysis was performed on
a Perkin-Elmer 240 analyser. UV-vis spectra were recorded on a
Hitachi U-3300 model while PL spectra were taken using a Hitachi
F-4500 fluorescence spectrophotometer.
Figure 2 outlines the emission spectra of the compounds
in CH2CI2• The emission peaks of compounds are located at
about 500 nm in the green region. When R is 2-naphthyl (2d),
the emission peak was red shifted by 16 nm compared to the
compound of 2a.
General procedure for the synthesis of the aryl bromides or chlorides
containing quinoline groups
A solution of 2-methyquinoline 10.5 g (0.0734 mol), 4-bromo- or
4-chloro-benzaldehyde (0.084 mol) and 5 g (0.0375 mol) of acetic
anhydride was heated at 150°C for 16 h in a 50 mL round bottomed
flask fitted with a reflux condenser. The hot solution was poured into
10% sodium hydroxide solution (50 mL). After the oil congealed,
the solid was removed by filtration, washed with water and then with
ice cold ethanol (10 mL) and dried at 60°C. 60-70% yield.
Conclusion
In conclusion, several novel triphenylamine
derivatives have
(E)-2-(4-chlorostyryl)quinoline (Ia): White solid, Yield: 65%. M.p.
143°C. FTIR (KBr pellet, vm,/cm·I): 3045, 1588, 1498, 1395, 1095,
974,824,737. IH NMR (400, CDCI3) OH: 8.11 (d, J= 8.4 Hz, I H),
8.08 (d, J= 8.4, I H), 7.77 (d, J= 8.4 Hz,1 H), 7.71 (dd, J= 7.6 Hz,
J= 7.6 Hz, I H), 7.64 (d, J= lOA Hz, I H), 7.61 (d, J= 2.4 Hz I H);
7.55 (s, I H), 7.53 (s, I H), 7.50 (dd,J= 7.2 Hz,J= 7.2 Hz, I H), 7.35
(m, 3 H). l3C NMR (400 MHz, CDCI3): 0,: 155.5, 148.2, 136.4, 135.0,
134.3, 133.0, 129.8, 129.5, 129.2, 129.0 128.4, 127.5, 127.4, 126.3,
been synthesised.
spectra of these derivatives
These compounds
behaviours and emit strongly in solution, with the emission
maxima in the range of 500-515 nm.
The absorption
in CH2CI2 were investigated.
exhibit similar absorption and emission
and photoluminescent
Experimental
119.3. Anal. Calcd for C17
H12CIN: C, 76.84; H, 4.55; N, 5.27. Found:
The aromatic amines, palladium(II) and tri-o-tolylphosphine were
products of the Aldrich Chemical Co. Sodium tert-butoxide was
purchased from Alfa-Aesar and stored in a Vacuum Atmospheres
glove box under nitrogen. Toluene was distilled under nitrogen from
molten sodium. All chemicals were used as supplied. All melting
points were determined with a WRS-IA melting point apparatus and
were uncorrected. Proton NMR ('H NMR and l3C NMR) spectra
were run on a Bruker AV-400 NMR spectrometer and chemical
shifts expressed as 0 (ppm) values with TMS as an internal standard.
IR spectra were recorded in KBr on a Nicolet NEXUS 470 FT-IR
C, 76.81; H, 4.59; N, 5.21%.
(E)-2-(4-bromostyryl)quinoline (Ib): White solid, Yield: 68%.
M.p. 133-134°C. FTIR (KEr pellet, cm·I): 3045, 1588, 1498, 1395,
1062,1005,965,821, 745.IHNMR(400,CDCI3)OH: 8.11 (d,J= 8.8 Hz,
I H), 8.07 (d, J
= 8.4, I H), 7.77 (d, J = 8.8 Hz, I H), 7.70 (dd,
J= 7.6 Hz,J= 8.0 Hz, I H), 7.63 (d, J= 3.6 Hz, I H), 7.60 (d,J= 4.0 Hz
I H); 7.50 (m, 5 H), 7.37 (d, J= 16 Hz I H). l3C NMR (400 MHz,
CDCI3):0,: 155.5,148.2,136.5,135.5,133.1,131.9,129.9,129.6,129.2,
128.7, 127.5, 127.4, 126.3, 122.5, 119.3. Anal. Calcd for C17
65.83; H, 3.90; N, 4.52. Found: C, 65.84; H, 3.98; N, 4.57%.
H12BrN: C,
1.2
General procedure for the synthesis of conjugated quinolines
To a 25 mL sidearm flask was added the aryl bromide or chloride
containing
a
quinoline group (1.20 mmol), aromatic amine
1.0
- 0 - 2 a
- v - 2 b
- o - 2 c
-0-2d
- 0 - 3 a
- 0 - 4 a
(1.00 mmol), Pd(OACh (0.06 mmol, PdlBr
=
5%), P(o-tolylh
(0.18 mmol) and sodium tert-butoxide (1.50 mmol). Toluene (10 mL)
was injected into the flask from a syringe. The reaction mixture was
heated and stirred at 110 °C under nitrogen for an appropriate time
until the reaction was complete. The reaction mixture was then cooled
to room temperature, filtered through a mixture of celite and silica
gel pad and washed with dichloromethane. The filtrate was washed
with water and then dried by MgS04• Concentration of the filtrate on
a rotary evaporator followed by washing of the solid material with
ethanol afforded the desired crude product. The crude product was
purified by column chromatography on silica gel using ethyl acetate/
hexane (I : 10) as eluent.
=i
0.8
~
<:
i
0.6
0.4
5
••
~
0.2
0.0
(E)-N -methy1-N - (4- (2 -(quino lin- 2 -yl)vinyl)ph enyl) benz enam ine
(2a): Yellow solid, Yield: 60%. M.p. 121-123°C. FTIR (KBr pellet,
cm·I): 3057, 2926,1588,1552,1514,1494,1346,1182,1117,826,
752,697. IH NMR (400, CDCI3) OH: 8.12 (d, J= 8.4 Hz, I H), 8.05
400
300
500
W avelength(nm )
(d, J
= 8.8, I H), 7.64-7.74 (m, 4 H), 7.63 (d, J = 8.4 Hz, 2 H),
7.47 (dd, J= 6.8 Hz, J= 7.6 Hz,1 H), 7.30-7.40 (m, 3 H), 7.13-7.21
Fig. 1 Absorption spectra of novel compounds in CH2CI2.

JOURNAL OF CHEMICAL RESEARCH 2009 429
(m, 3H), 6.96 (d, J= 8.0 Hz, 2H), 3.36 (s, 3H). l3C NMR (400 MHz,
CDCI3): 1\: 156.5, 148.6, 148.4, 147.5, 136.3, 134.3, 130.1, 129.7,
129.0, 127.9, 127.8, 127.3, 127.1, 126.8, 124.7, 119.2, 119.1, 118.7,
118.3,41.5. Anal. Ca1cd for C24H20N2:C, 85.68; H, 5.99; N, 8.33.
Found: C, 85.66; H, 5.92; N, 8.28%.
127.5,127.2,126.9,125.9,124.9,119.1,114.9,52.0,
Ca1cd for C22H22N2:C, 84.04; H, 7.05; N, 8.91. Found: C, 84.39; H,
7.09; N, 8.86%.
25.9, 25.6. Anal.
(E)-N, N-diethyl-4-(2-((4-(quinolin-2-yl)vinyl)benzenamine
(4a):
Yellow solid, Yield 58%. M.p. 101-103°C. FTIR (KBr pellet, em"):
3030, 2973, 2919, 1588, 1519, 1089, 1050, 825, 750, 668.
'H NMR (400, CDCI3) 0H: 8.05 (t, J = 8.4 Hz, J = 9.6 Hz, 2 H), 7.69
(m, 3 H), 7.54 (m, 2 H), 7.23 (m, 3 H), 6.69 (d, J= 8.8 Hz, 2 H), 3.40
(m, 4 H); 1.20 (m, 6 H). l3C NMR (400 MHz, CDCI3): 0,: 156.5,
148.4, 148.2, 136.3, 134.1, 129.3, 129.1, 128.2, 127.5, 127.2, 126.8,
126.0, 124.8, 119.1, 114.8,44.8, 13.2. Anal. Ca1cd for C2,H22N2: C,
83.40; H, 7.33; N, 9.26. Found: C, 83.32; H, 7.39; N, 9.21%.
(E)-N -pheny 1-N -(4- (2- (quinol in-2 -yl)v inyl)p heny l)benzenamin e
(2b): Yellow solid, Yield: 58%. M.p. 150-151 °C. FTIR (KEr pellet,
em"): 3034, 2925, 1588, 1508, 1490, 1330, 1282, 1315, 1176,832,
750,695. 'H NMR (400, CDCI3) OH: 8.09 (d, J= 8.4 Hz, 2 H), 7.77
(d, J= 8.0, 1 H), 7.70 (dd, J= 7.6 Hz, J= 7.2 Hz, 1 H), 7.66 (s, 1 H),
7.63 (d, J= 8.0 Hz, 1 H), 7.53 (s, 1 H); 7.50 (t, J = 8.4 Hz, J = 7.2 Hz
2 H), 7.30 (m, 5 H), 7.16 (d, J= 8.0 Hz 4 H), 7.08 (dd, J= 8.0 Hz,
J= 7.2 Hz,4H). '3CNMR(400 MHz, CDCl3): 0,: 156.4,148.4,148.3,
147.3, 136.2, 134.0, 130.2, 129.7, 129.4, 129.0, 128.2, 127.5, 127.2,
127.0, 125.9, 124.9, 123.4, 122.8, 119.1. Anal. Ca1cd for C29H22N2:
C, 87.41; H, 5.56; N, 7.03. Found: C, 87.32; H, 5.54; N, 7.03%.
(E)- 3-m ethy 1-N-phenyl- N-(4- (2-(quinolin- 2-y I)viny I)phenyl)
benzeneamine (2c): Yellow solid, Yield: 55%. M.p. 149-150°C. FTIR
(KBr pellet, em"): 3032,2925, 1588, 1508, 1489, 1314, 1280, 1180,
The project is sponsored by the Natural Science Foundation
for the Education Ministry of Zhejiang Province.
Received 18 December 2008; accepted 18 May 2009
Paper 08/0346 doi: 10.3184/030823409X465286
Published online: 13 July 2009
691,832,753,701.
'H NMR (400, CDCI3) OH: 8.09 (d, J= 8.4 Hz,
2 H), 7.76 (d, J= 8.0,1 H), 7.70 (dd, J= 7.6 Hz, J= 8.0 Hz,1 H),
7.66 (s, 1 H), 7.63 (d, J= 8.8 Hz, 2 H),7.50 (m, 3 H); 7.30 (m, 3 H),
7.17 (m, 3 H), 7.08 (m, 3 H), 6.95 (m, 3 H), 2.3 (s, 3 H). l3C NMR
(400 MHz, CDCI3): 0,: 156.5, 148.6, 148.3, 147.4, 147.3, 139.3,
136.2, 134.1, 130.0, 129.7, 129.3, 129.2, 129.0, 128.2, 127.5, 127.2,
126.9, 125.9, 125.8, 124.9, 124.5, 123.3, 122.7, 122.3, 119.1,21.4.
Anal. Ca1cd for C30H24N2:C, 87.35; H, 5.86; N, 6.79. Found: C,
87.40; H, 5.78; N, 6.86%.
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(E)-N-pheny 1-N-(4-(2-(quinoli n-2-yl)vi nyl)ph enyl) nap hthalene-
2-amine (2d): Yellow solid, Yield: 50%. M.p. 168-169°C. FTIR
(KBrpellet, em"): 3056, 2927,1591,1506,1491,1315,1294,1279,
1179,817,747,695.
J= 12.0 Hz 2 H), 7.77 (m, 3 H), 7.67 (m, 4 H), 7.52 (m, 4 H), 7.40
(m, 2 H), 7.33 (m, 4 H); 7.19 (d, J 7.6 Hz, 2 H), 7.12 (m, 3 H).
'H NMR (400, CDCI3) OH: 8.10 (t, J = 8.4 Hz,
7
8
M.M. Wienk and R.A.J. Janssen, J Arn. Chern. Soc., 1997, 119,4492.
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=
l3C NMR (400 MHz, CDCI3): 0,: 156.3, 148.3, 147.3, 144.9, 136.2,
134.4, 134.0, 134.0, 130.6, 130.4, 129.7, 129.4, 129.1, 128.3, 127.6,
127.5, 127.2, 127.2, 127.1, 127.0, 126.4, 126.0, 125.1, 124.8, 124.7,
123.6, 123.1, 121.3, 119.1. Anal. Ca1cd for C33H24N2:C, 88.36; H,
5.39; N, 6.25. Found: C, 88.43; H, 5.37; N, 6.20%.
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(E)-2-(4-(piperidin-l-yl)styryl)quinoline
(3a): Yellow solid, Yield:
57%. M.p. 110-111 °C. FTIR (KBr pellet, em"): 3031, 2927, 1594,
1515, 1451, 1426, 1236, 1187, 1128, 825, 753. 'H NMR (400,
CDCI3) OH: 8.06 (t, J = 8.8 Hz, J = 7.6 Hz, 2 H), 7.69 (m, 3 H), 7.54
(m, 2 H), 7.23 (m, 3 H), 6.92 (d, J= 8.8 Hz, 2 H), 3.25 (t, J= 5.2 Hz,
J= 6.0 Hz, 4 H); 1.70 (m, 4 H), 1.61 (m, 2 H). l3C NMR (400 MHz,
CDCI3): 0,: 156.5, 148.5, 148.2, 136.3, 134.1, 129.4, 129.0, 128.2,
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