The solvent was evaporated under reduced pressure to give
3.4 g (88%) of 1 as a brown liquid. 1H-NMR (400 MHz,
CDCl3): d 10.16 (s, 1H), 7.69 (d, J 5 8.9 Hz, 1H), 6.25 (d, J 5
8.9 Hz, 1H), 6.00 (s, 1H), 4.01 (t, J 5 6.6 Hz, 2H), 3.41 (q, J 5
7.1 Hz, 4H) 2.02 (m, 2H), 1.50 (m, 2H), 1.20 (t, J 5 7.1 Hz, 6H),
0.97 (t, J 5 7.4 Hz, 3H). 13C-NMR (100 MHz): d 187.4, 162.8,
153.6, 130.4, 115.3, 104.5, 95.6, 67.9, 44.6, 31.3, 19.4, 13.8, 12.7.
composed of 20 mL toluene and 50 mL of 50 wt% aqueous
NaOH using tetra(n-butyl)ammonium bromide as the phase
transfer catalyst at 100 uC for 3 days. After diluting the
reaction mixture with ethyl acetate, the organic layer was
washed with water several times to remove excess NaOH. The
organic layer was separated and dried over MgSO4. The yellow
liquid 5 (8.1 g, 50%) was obtained after column chromato-
graphy with hexane–ethyl acetate (10 : 1) 1H-NMR (400 MHz,
CDCl3): d 7.03 (t, J 5 7.3 Hz,1H), 6.91 (d, J 5 7.3 Hz, 1H),
6.53 (m, 2H), 3.26 (t, J 5 5.5 Hz, 2H), 3.21 (t, J 5 7.6 Hz, 2H),
2.73 (t, J 5 6.4 Hz, 2H), 1.92 (m, 2H), 1.57 (m, 2H), 1.31 (m,
6H), 0.89 (t, J 5 6.6 Hz, 3H). 13C-NMR (100 MHz): d 145.4,
129.1, 127.0, 122.1, 115.1, 110.4, 51.5, 49.4, 31.8, 28.2. 26.9.
26.2, 22.7, 22.3, 14.0.
4-(Diethylamino)-2-methylbenzaldehyde (2)
Phosphous oxychloride (10 mL, 107 mmol) was slowly added
to dimethylformamide (75 mL) at 0 uC. After 30 minutes,
N,N-diethyl-m-toluidine (14.3 g, 87.6 mmol) was added and
then was heated at 90 uC for 3 h. The reaction mixture was
then cooled, poured in to crushed ice, and neutralized with
sodium acetate. The mixture was extracted with ethyl acetate.
The extract was washed with water, dried over MgSO4, and
then concentrated. The bright brown oil 2 (13.5 g, 81%) was
obtained after column chromatography with hexane–ethyl
1-Hexyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde (6)
Compound 6 was prepared by analogy to 2 using 1-hexyl-
1,2,3,4-hydroquinoline (5) instead of N,N-diethyl-m-toluidine
in 78% yield. 1H-NMR (400 MHz, CDCl3): d 9.62 (s, 1H), 7.52
(d, J 5 8.6 Hz, 1H), 7.50 (s, 1H), 6.53 (d, J 5 8.6 Hz, 1H), 3.36
(t, J 5 5.6 Hz 2H), 3.29 (t, J 5 7.6 Hz, 2H), 2.75 (t, J 5 6.4 Hz,
2H), 1.92 (m, 2H), 1.59 (m, 2H), 1.33 (m, 6H), 0.88 (t, J 5
6.6 Hz, 3H). 13C-NMR (100 MHz): d 190.0, 150.3, 131.2,
130.4, 124.5, 121.6, 109.3, 51.5, 49.8, 31.6, 28.0, 26.7, 26.3,
22.6, 21.5, 14.0.
1
acetate (30 : 1) as an eluent. H-NMR (400 MHz, CDCl3): d
9.91 (s, 1H), 7.61 (d, J 5 8.8 Hz, 1H), 6.52 (dd, J 5 8.8, 2.6 Hz,
1H), 6.37 (s, 1H), 3.40 (q, J 5 7.1 Hz, 4H), 2.59 (s, 3H), 1.19 (t,
J 5 7.1 Hz, 6H). 13C-NMR (100 MHz): d 190.1, 151.4, 143.1,
134.9, 122.9, 112.9, 108.4, 44.5. 20.4, 12.5.
1-(4-Methylphenyl)-1,2,3,4-hydroquinoline (3)
All bis-DCM derivatives (7, 8, 9 and 10) were synthesized
using Knoevenagel condensation between (2,6-dimethyl-
4H-pyran-4-ylidine)propanedinitrile and the corresponding
aldehyde (1, 2, 4 and 6), analogous to previously described
methods.25{
Tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) (1.03 g,
1.12 mmol), 1,19-bis(diphenylphosphino)ferrocene (dppf)
(0.96 g, 1.73 mmol), 4-bromotoluene (12.8 g, 75 mmol) were
dissolved in 500 mL of dry toluene and stirred for 15 min.
Sodium tert-butoxide (10.8 g, 112 mmol) and 1,2,3,4-hydro-
quinoline (10.0 g, 75 mmol) were then added. The reaction
mixture was heated to 100 uC for 24 h, and then was portioned
between ethyl acetate, and the aqueous layer was extracted
with ethyl acetate. The combined organic fractions were dried
over MgSO4, and the solvent was evaporated under reduced
pressure. Column chromatography (hexane) afforded 12.6 g
Device fabrication and characterization
OLEDs were fabricated on glass substrates precoated with a
layer of indium tin oxide (ITO), which were precleaned
by ultrasonic treatment in detergent, de-ionized water,
acetone and methanol, respectively, and were pretreated
with oxygen plasma cleaner before use. Organic layers and
cathode layers (LiF/Al) were deposited by conventional
vacuum vapor deposition below 1 6 1026 Torr. The emit-
ting area was 2 6 2 mm. The doped devices have a struc-
ture of ITO/4,49,40-tris(3-methylphenylamino)triphenylamine
(m-MTDATA) (20 nm)/N,N9-bis(1-naphthyl)-diphenyl-1,19-
biphenyl-4,49-diamine (NPB) (40 nm)/tris(8-quinolinolato)-
aluminium (Alq3) : red dopant (35 nm)/Alq3 (35 nm)/LiF
(1 nm)/Al (100 nm). The electroluminescence (EL) spectrum
and Commission International del’Eclairage (CIE) color
1
(75%) of product 3. H-NMR (400 MHz, CDCl3): d 7.14 (m,
4H), 7.00 (d, J 5 7.3 Hz, 1H), 6.89 (t, J 5 6.6 Hz, 1H), 6.64 (m,
2H), 3.58 (t, J 5 5.6 Hz, 2H), 2.84 (t, J 5 6.4 Hz, 2H), 2.34 (s,
3H), 2.05 (m, 2H). 13C-NMR (100 MHz): d 145.8, 144.9, 133.6,
130.0,129.3,126.3,125.3,123.8,117.7,115.1,55.1,27.8,22.6,20.9.
1-(4-Methylphenyl)-1,2,3,4-tetrahydroquinoline-6-carbaldehyde
(4)
Compound 4 was prepared by analogy to 2 using 1-(4-
methylphenyl)-1,2,3,4-hydroquinoline (3) instead of N,N-
diethyl-m-toluidine in 80% yield. 1H-NMR (400 MHz,
CDCl3): d 9.65 (s, 1H), 7.51 (s, 1H), 7.34 (dd, J 5 8.7,
2.1 Hz, 1H), 7.24 (d, J 5 6.1 Hz, 2H), 7.11 (d, J 5 8.2 Hz, 2H),
6.44 (d, J 5 8.6 Hz, 1H), 3.64 (t, J 5 5.6 Hz, 2H), 2.89
(t, J 5 6.3 Hz, 2H), 2.37 (s, 3H), 2.05 (m, 2H). 13C-NMR
(100 MHz): d 190.2, 150.6, 143.6, 136.2, 131.1, 130.6, 129.8,
126.7, 126.1, 122.0. 112.9, 51.8, 27.7, 21.8, 21.0.
coordinates were measured with
a
spectroradiometer
(Minolta CS-1000). Current–voltage–luminance (I–V–L) mea-
surements were performed with a current/voltage source
(Keithley 238) and a luminescence meter (Minolta LS-100).
Devices were tested in air without further encapsulation.
Results and discussion
Molecular design and synthesis
1-Hexyl-1,2,3,4-hydroquinoline (5)
The structures of the novel red dopants (7–10), widely studied
red dopants (DCM and DCJTB), and other bis-DCM
derivatives (DADB and bis-DCJTB) are shown in Fig. 1. We
1,2,3,4-Hydroquinoline (10.0 g, 7.5 mmol) was reacted with
1-bromohexane (18.6 g, 11 mmol) in a two-phase system
This journal is ß The Royal Society of Chemistry 2005
J. Mater. Chem., 2005, 15, 2470–2475 | 2471