Design and synthesis of 2-substituted-8-hydroxyquinline zinc complexes with hole-transporting ability for highly effective yellow-light emitters

Article abstract of DOI:10.1016/j.jorganchem.2009.06.022

Four multifunctional 8-hydroxyquinoline derivatives were designed and synthesized, their structures were identified by FT-IR, ¹H NMR, MS and elemental analysis. Among them are (E)-2-(2-(9-(4-methoxyphenyl)-9H-carbazol-3-yl)vinyl) quinolato-zinc

Full text of DOI:10.1016/j.jorganchem.2009.06.022

Journal of Organometallic Chemistry 694 (2009) 3511–3517
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Design and synthesis of 2-substituted-8-hydroxyquinline zinc complexes with
hole-transporting ability for highly effective yellow-light emitters
a
a,c,
Xinhua Ouyang a, Guangrong Wang a, Heping Zeng a,b, , Weiming Zhang , Jing Li
*
*
a Institute of Functional Molecule, South China University of Technology, Guangzhou 510641, People’s Republic of China
b School of Chemistry and Environment, South China Normal University, Guangzhou 510631, People’s Republic of China
c Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 May 2009
Received in revised form 15 June 2009
Accepted 18 June 2009
Available online 23 June 2009
Four multifunctional 8-hydroxyquinoline derivatives were designed and synthesized, their structures were
identified by FT-IR, 1H NMR, MS and elemental analysis. Among them are (E)-2-(2-(9-(4-methoxyphenyl)-
9H-carbazol-3-yl)vinyl) quinolato-zinc (1), (E)-2-(2-(9-p-tolyl-9H-carbazol-3-yl)vinyl)quinolato-zinc (2),
(E)-2-(2-(9H-fluoren-2-yl)vinyl)quinolato-zinc (3), and (E)-2-(2-(phenanthren-9-yl)vinyl)quinolato-
zinc (4). The electroluminescence (EL) and hole-transporting characteristics of these materials were
investigated on four configurations: (A) ITO/2-TNATA/NPB/1, 2, 3 or 4/Alq3/LiF/Al; (B) ITO/2-TNATA/
NPB/1, 2, 3 or 4/LiF/Al; (C) ITO/2-TNATA/1, 2, 3 or 4/Alq3/LiF/Al; and (D) ITO/2-TNATA/1 or 2/NPB/Alq3/
LiF/Al. The maximum luminescence and current efficiencies of are 3556 cd mꢀ2 (at 13 V) and
2.17 cd Aꢀ1 (at 9 V) for compound 2, 4624 cd mꢀ2 (at 15 V) and 2.1 cd Aꢀ1 (at 7 V) for compound 3, and
3164 cd mꢀ2 (at 14 V) and 1.83 cd Aꢀ1 (at 13 V) for compound 4 in the configuration D, respectively,
indicating that they are good multifunctional materials with strong hole-transporting abilities and
luminescence properties.
Keywords:
2-Substituted-8-hydroxyquinolate-zinc
Yellow-light emitting material
Multifunctional material
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
feasible approach is to extend the degree of p-conjugation in
8-hydroxyquinoline molecule, which will bring about a huge batho-
chromic effect. Meanwhile, some OLEDs with highly electrolumi-
nescent efficiencies can be also obtained by modifying the
quinoline ring with differently functional groups. Active research
in this area has been conducted over the past twenty years. For
example, Mishra et al. [12] synthesized several 5-alkoxymethyl-
and 5-aminomethy substituted 8-hydroxyquinoline alumina com-
plexes, which were characteristic of strong green-light emissions
with high quantum yields. Cui et al. [13] also reported 2-substit-
ued-8-hydroxyquinoline molecules with large conjugated groups
and tuned their luminescence to yellow-light (kex = 610 nm). Like-
wise, Xie et al. [14] synthesized a new 5-substitued-8-hydroxyl
quinoline exhibiting bi-functional and dipolar behavior. Their re-
sults showed that this molecule can be used as hole and electron
transporter and emitter. Therefore, the incorporation of electron-
donors (chemical structure suitable for capturing hole carriers)
and electron-acceptors (chemical structure suitable for capturing
electron carriers) into one molecule is highly desirable to enhance
performance and improve fabrication technology.
Organic photo- and electronic materials have commanded
increasing attention since the discovery of organic conductors
[1–3], which offer large-area, flexible, and lightweight devices
through simple and low-cost processing. During the past twenty
years, much effort has been paid to the development of highly effi-
cient organic light-emitting diodes (OLEDs) [4–6], especially the
white OLEDs [7–10]. To obtain white emission, various strategies
have been developed. For small-molecule OLEDs, the general ap-
proach is to fabricate multiplayer devices by consecutive evapora-
tion involving three primary colors (blue, green and red) or two
special colors (blue and yellow). However, multiplayer construc-
tion of devices will increase of the cost of fabrication processes.
In order to reduce the cost and obtain white OLEDs with minimal
process of fabrication, it would be necessary to discover multifunc-
tion and highly efficient yellow-light emitting materials.
8-Hydroxyquinoline aluminum (Alq3) has been identified as an
excellent green-light emitting and electronic transporting material
[11]. In order to retain the excellent photoelectron properties of
8-hydroxyquinoline itself and achieve yellow-light emission, a
In this paper, we report the synthesis, device fabrication and elec-
troluminescence measurements of 2-substituted-8-hydroxy-
quinolato-Zn derivatives containing two different carbazole,
fluorine and phenanthrene units owing to their abilities in
luminescence and charge-transfer [15–18]. These four compounds
* Corresponding authors. Address: Institute of Functional Molecule, South China
University of Technology, Guangzhou 510641, People’s Republic of China.
E-mail addresses: hpzeng@scut.edu.cn (H. Zeng), jingli@rutgers.edu (J. Li).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.06.022

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X. Ouyang et al. / Journal of Organometallic Chemistry 694 (2009) 3511–3517
Scheme 1.
are: (E)-2-(2-(9-(4-methoxyphenyl)-9H-carbazol-3-yl)vinyl)quino-
lato-zinc (1), (E)-2-(2-(9-p-tolyl-9H-carbazol-3-yl)vinyl)quinolato-
zinc (2), (E)-2-(2-(9H-fluoren-2-yl)vinyl)quinolato-zinc (3) and
(E)-2-(2-(phenanthren-9-yl)vinyl)quinolato-zinc (4). The synthetic
route of 1, 2, 3 and 4 is shown in Scheme 1. In combination of 8-
hydroxyquinoline with fluorene and carbazole, we anticipate the
formation of new dipolar and multifunctional materials with excel-
lent performance. Optical, thermal properties of these compounds
were investigated, and electroluminescent devices using them as
emission layers (EL), hole-transporting layers (HTL) or EL&HTL were
fabricated and characterized.
around 567–585 nm in solution state and 591–628 nm in solid
state. The spectra obtained for the solid state are red-shifted in
relation to the solution measurements, as can be seen in Table 1,
due to the molecular aggregation. Molecular aggregation leads to
shifts of the state energies depending on the mutual orientation
of the molecules forming a dimer, different transitions in the sys-
tem can be forbidden or allowed. The optical properties associated
with H-aggregates and J-aggregates [20]. It has been shown that H-
type molecular aggregates result in the shift of the luminescence
band. The insertion of p-conjugation bridging moieties also causes
a significant red-shift in the spectra: 1, 2, 3 and 4 exhibit yellow to
PL
orange-red emission at peak wavelengths (k ) at 591, 593, 602
max
and 628 nm, respectively. Thus, the photophysical properties of
2. Results and discussions
these emitters are strongly affected by the
p-conjugation lengths.
Similar to the absorption spectra, the PL spectrum of 4 is red-shifted
The thermal properties of the 8-hydroxyquinoline derivatives,
investigated by differential scanning calorimetry (DSC) and ther-
mo-gravimetric analysis (TGA), are summarized in Table 1. The
glass-transition temperatures (Tgs) of all four compounds are
around 181–187 °C. 3 exhibits the highest Tg (187 °C), due to its ri-
gid fluorene structure segment. Thermal decomposition tempera-
tures (Tds) of all compounds are around 360–480 °C. The results
indicate that the incorporation of
p-conjugated bridges into the
8-hydroxyquninoline system enhances the thermal properties sig-
nificantly, especially with the fluorene derivative comparing with
the publications about 2-methyl-8-hydroxylquinolato-zinc (Tg,
103 °C) [19].
The absorption data for the four compounds are also summa-
rized in Table 1 and Fig. 1a. Among the four compounds, the max-
imal absorptive peaks of 1 and 2 are very similar and centered at
about 380 nm, and the absorption spectra of 3 and 4 are also al-
most identical and at a maximum wavelength of ꢁ350 nm, due
to their similar p-conjugation structures and lengths. In the mean-
while, we also plotted the absorptive spectra of A1–A4 in Fig. 1a, it
can be seen the spectra appeared clear difference between the
samples A1–A4 and samples 1–4, which indicated there were
interactions among them. The phenomena can be attributed to
charge-transfer form metal-to-ligand transitions (MLCT) or li-
gand-to-metal transitions (LMCT). Photoluminescence (PL) data
for these samples in solution and in solid state are recorded in Ta-
ble 1 and Fig. 1b. The PL emissions of the four compounds appear
Table 1
Summary of physical properties of compounds 1, 2, 3 and 4.
abs
em
em
k
(nm)
k
(nm)
k (nm)
max
U
Tg (°C)
Td (°C)
s (ns)
max
max
in DMF
in solid
1
2
3
4
382
383
351
345
576
571
585
567
591
593
602
628
0.096
0.094
0.076
0.08
184
186
187
181
372
381
363
382
3.23
3.34
3.58
3.42
Fig. 1. (a) The absorptive spectra of samples 1, 2, 3 and 4 in DMF; (b) the PL spectra
of samples 1, 2, 3, 4 and Znq in solid states.

X. Ouyang et al. / Journal of Organometallic Chemistry 694 (2009) 3511–3517
3513
to 628 nm, compared with 515 nm for 8-hydroxy-quinolato-Zn
3. Electrochemical properties
(Znq), because of the electron-rich nature of phenanthrene ring
and its lower aromaticity relative to that of a benzene ring.
Cyclic voltammetry (CV) was employed to investigate the elec-
trochemical behaviors of the compounds 1, 2, 3 and 4. The highest
occupied molecular orbital (HOMO) and lowest unoccupied molec-
ular orbital (LUMO) energy levels of the materials were estimated
according to the electrochemical performance and emission spec-
tra. Oxidation behaviors of 1, 2, 3, and 4 have been investigated
in DMF as shown in Fig. 2, and the results are summarized in Table
2. The HOMO energy values for these compounds were calculated
based on the value of ꢀ4.8 eV for ferrocene with respect to zero
vacuum level.
In order to assess their electroluminescence functionality, each
of the four compounds was fabricated into four different device
structures. The device structures and related information are
outlined in Fig. 3. In these configurations of A, B, C and D, ITO
glass is used as transparent anode, N-(naphthalene-2-yl)-N0,N0-
bis(naphthalene-2-yl(phenyl)amino)phenyl)-N-phenylbenzene-
1,4-diamine(2-TNATA) is used as hole-injecting material (HIM),
due to its energy of the highest occupied orbit (HOMO), which is
close to the energy of HOMO of ITO (4.8 eV), tris-8-hydroxyl-
quinolato-aluminum (Alq3) as electron-transporting material
(ETM) and lithium fluoride (LiF) as the buffer layer, due to its en-
ergy of the lowest unoccupied orbit (LUMO), which is close to
the energy of LUMO of Al (3.7 eV). Samples of compounds 1, 2, 3
and 4 acted as emitter in configuration A, emitter and ETM in con-
figuration B, emitter and hole-transporting materials (HTM) in
configuration C, and HTM and ETM in configuration D, respectively,
for which luminescence, HT and ET properties were examined. N,N0-
bis(naphthyl)-N,N0-diphenyl-1,10-biphenyl-4,40-diamine (NPB) was
used as HTM in the configuration A and B, and emitter in the con-
figuration D.
Fig. 2. Cyclic voltammograms of 1, 2, 3, and 4 with the concentration of 0.001 M in
0.1 M Bu4NPF6-DMF, with a glassy carbon electrode at a scan rate of 50 mV sꢀ1. A
platinum wire and an Ag/AgCl were used as the counter and reference electrode,
respectively.
Table 2
Electrochemical parameters of compounds 1, 2, 3 and 4.
red
ox
Compounds
E
(V)
E
(V)
onset
Eg (eV)a
HOMO (eV)
LUMO (eV)
onset
1
2
3
4
ꢀ1.96
ꢀ1.81
ꢀ2.05
ꢀ2.01
0.39
0.56
0.38
0.22
2.16
2.18
2.12
2.19
ꢀ5.19
ꢀ5.36
ꢀ5.18
ꢀ5.02
ꢀ3.03
ꢀ3.18
ꢀ3.06
ꢀ3.01
The normalized EL spectra of compounds 1, 2, 3 and 4 in devices
A, B and C at 14 V are shown in Fig. 4. The EL spectra of 1, 3 and 4
are very similar in these configurations. It is obvious that they
a
Eg estimated from maximal emission peak energy.
Fig. 3. The molecular structures of organic materials and the device structures of the OLEDs.

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X. Ouyang et al. / Journal of Organometallic Chemistry 694 (2009) 3511–3517
exhibit yellow-light emission. Further analysis showed that all
compounds act as the emitter in the devices A–C. The results also
clearly indicate that the observed yellow emission originates from
the compounds 1, 2, 3 and 4 layers by comparing electrolumines-
cence with photoluminescence spectra. Some of important param-
eters of these devices are given in Table 3. CIE coordinates of the
three different devices with compounds 1, 2, 3 and 4 as a function
of applied voltages.
Luminescent brightness–voltage (L–V) and current efficiency–
voltage (E–V) characteristics of devices A–C are shown in Figs. 5
and 6, respectively. In device A, NPB acted as a hole-transporting
(HTL), Alq3 as an electron-transporting layer (ETL), and samples
of 1, 2, 3 and 4 as yellow-light emitting layers. Maximum lumi-
nance brightness of device A for 1, 2, 3 and 4 are 1420 cd mꢀ2 (at
14 V), 3596 cd mꢀ2 (at 14 V), 2782 cd mꢀ2 (at 14 V), and
2654 cd mꢀ2 (at 14 V), respectively, and the maximum lumines-
cent efficiencies for 1, 2, 3 and 4 are 0.67 cd Aꢀ1 (at 10 V),
1.76 cd Aꢀ1 (at 9 V), 1.08 cd Aꢀ1 (at 13 V), and 0.89 cd Aꢀ1 (at
13 V), respectively. In device B, one can easily find that the Alq3
is removed in order to investigate the electron-transporting prop-
erties and luminescent properties of 1, 2, 3 and 4. The maximum
luminescent brightness and maximum current efficiencies of de-
vice B for 1, 2, 3 and 4 are 697 cd mꢀ2 (at 15 V) and 0.31 cd Aꢀ1
(at 14 V), 192 cd mꢀ2 (at 13 V) and 0.15 cd Aꢀ1 (at 13 V),
1222 cd mꢀ2 (at 10 V) and 0.35 cd Aꢀ1 (at 9 V), and 379 cd mꢀ2
(at 15 V) and 0.78 cd Aꢀ1 (at 13 V), respectively. In the device C,
we removed the hole-transporting layer (NPB) in comparison with
the structure of device A, and the maximum luminescent bright-
ness and current efficiencies for samples of 1, 2, 3 and 4 are
1396 cd mꢀ2 (at 14 V) and 0.96 cd Aꢀ1 (at 13 V), 3596 cd mꢀ2 (at
14 V) and 1.76 cd Aꢀ1 (at 9 V), 3384 cd mꢀ2 (at 10 V) and
0.92 cd Aꢀ1 (at 9 V), and 3531 cd mꢀ2 (at 14 V) and 0.79 cd Aꢀ1
(at 12 V). By comparing the maximum luminescence and current
efficiencies in all of the devices, we noted that 1 is not good as yel-
low-light emitter, ELM and HLM materials due to its low lumines-
cence and efficiencies, and compound 3 is a good candidate as
multifunctional material such as emitter, ELM and HLM. Likewise,
the compounds 2 and 4 can be use as dipolar materials such emit-
ters and HLMs. Comparing the results with the publication of liter-
ature [21], we can find the maximum luminescent brightness of
published sample was 1200 cd mꢀ2 using undoped yellow emitter,
which indicated our results improved significantly the yellow
luminescent brightness. It will provide a new method to enhance
the yellow brightness.
In order to investigate in further depth the multifunctional
properties of 2, 3 and 4, we designed another configuration D
(Fig. 3) to test the Hole-transporting and luminescence properties.
The samples of 2, 3 and 4 were used as HTM and yellow-light
emitters and the results are summarized in Fig. 7. By analyzing
Fig. 4. The EL spectra of 1–4 in (a) device A; (b) device B; and (c) device C.
Table 3
The results of compounds 1, 2 and 3 in the devices A, B and C.
Device
(samples)
Luminancemax
(cd mꢀ2
CIE coordinates (x, y)
(luminancemax
EL efficiencymax
(cd Aꢀ1
CIE coordinates (x, y)
(efficiencymax
Turn-on
voltage (V)
Power efficiency
gPmax (lm/w)
)
)
)
)
A (1)
A (2)
A (3)
A (4)
B (1)
B (2)
B (3)
B (4)
C (1)
C (2)
C (3)
C (4)
1420 @ 14 V
3596 @ 14 V
2782 @ 14 V
2654 @ 14 V
697 @ 15 V
192 @ 13 V
1222 @ 10 V
379 @ 15 V
1396 @ 14 V
3596 @ 14 V
3384 @ 10 V
3531 @ 14 V
(0.5283, 0.4642)
(0.4915, 0.4954)
(0.5189, 0.4691)
(0.5253, 0.4483)
(0.518, 0.4701)
(0.5, 0.4924)
(0.5205, 0.4713)
(0.5343, 0.4446)
(0.529, 0.4633)
(0.4915, 0.4954)
(0.5271, 0.459)
(0.5474, 0.4435)
0.67 @ 10 V
1.76 @ 9 V
1.08 @ 13 V
0.89 @ 13 V
0.31 @ 14 V
0.15 @ 13 V
0.35 @ 9 V
0.78 @ 13 V
0.96 @13 V
1.76 @ 9 V
0.92 @ 9 V
0.79 @ 12 V
(0.5351, 0.4593)
(0.4979, 0.4946)
(0.5189, 0.4691)
(0.523, 0.4499)
(0.5259, 0.4657)
(0.5, 0.4924)
(0.5294, 0.4647)
(0.5337, 0.4526)
(0.5311, 0.4622)
(0.4979, 0.4946)
(0.5317, 0.4564)
(0.5353, 0.4435)
8
4
5
6
7
5
6
5
7
6
8
6
1.25
3.3
1.03
1.91
0.6
0.0
0.55
0.0
1.92
4.
1.22
3.1

X. Ouyang et al. / Journal of Organometallic Chemistry 694 (2009) 3511–3517
3515
Fig. 5. The voltage–luminescence curves of samples of 1, 2, 3 and 4 in devices A, B and C.
Fig. 6. The voltage–efficiency curves of samples of 1, 2, 3 and 4 in devices A, B, and C.

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X. Ouyang et al. / Journal of Organometallic Chemistry 694 (2009) 3511–3517
the results of device D, we find the luminescence of these samples
is located at white-light range with two peaks in the EL spectra,
one is from the samples, and another is from NPB. The maximum
luminescence and efficiencies for 2, 3 and 4 are 3556 cd mꢀ2 (at
13 V) and 2.17 cd Aꢀ1 (at 9 V), 4624 cd mꢀ2 (at 15 V) and 2.1 cd Aꢀ1
(at 7 V), and 3164 cd mꢀ2 (at 14 V) and 1.83 cd Aꢀ1 (at 13 V),
respectively. In this configuration, the efficiencies and brightness
of the samples are improved significantly, demonstrating the good
hole-transporting properties of 2, 3 and 4. In addition, they also
show intensive luminescence in such a configuration. Further stud-
ies to optimize their performances by adjusting the thickness of
yellow-light emitting layer (compounds 2, 3 and 4) and blue-light
emitting layer (NPB) are currently under way.
4. Conclusions
We have synthesized four novel multifunctional 2-substituted-
8-hydroxyquinline zinc complexes and their structures have been
analyzed by FT-IR, 1H NMR, MS and element analysis. The electro-
luminescence (EL) and hole-transporting characteristics of these
bi-functional emitting materials have been studied by designing
four device configurations. In device A, the maximum lumines-
cence for 1, 2, 3 and 4 are 1420 cd mꢀ2 (at 14 V), 3596 cd mꢀ2 (at
14 V), 2782 cd mꢀ2 (at 14 V), and 2654 cd mꢀ2 (at 14 V), respec-
tively, and the maximum luminescent efficiencies for 1, 2, 3 and
4 are 0.67 cd Aꢀ1 (at 10 V), 1.76 cd Aꢀ1 (at 9 V), 1.08 cd Aꢀ1 (at
13 V), and 0.89 cd Aꢀ1 (at 13 V), respectively. In device B, the lumi-
nance and efficiencies for samples 1, 2, 3 and 4 are 697 cd mꢀ2 (at
15 V) and 0.31 cd Aꢀ1 (at 14 V), 192 cd mꢀ2 (at 13 V) and
0.15 cd Aꢀ1 (at 13 V), 1222 cd mꢀ2 (at 10 V) and 0.35 cd Aꢀ1 (at
9 V), and 379 cd mꢀ2 (at 15 V) and 0.78 cd Aꢀ1 (at 13 V), respec-
tively. In device C, these are 1396 cd mꢀ2 (at 14 V) and 0.96 cd Aꢀ1
(at 13 V), 3596 cd mꢀ2 (at 14 V) and 1.76 cd Aꢀ1 (at 9 V),
3384 cd mꢀ2 (at 10 V) and 0.92 cd Aꢀ1 (at 9 V), and 3531 cd mꢀ2
(at 14 V) and 0.79 cd Aꢀ1 (at 12 V). Our results show that 2, 3
and 4 are good multifunctional materials with strong hole-trans-
porting abilities and luminescence properties.
5. Experimental
5.1. Materials
8-Hydroxy-2-methylquinoline, phenanthrene-9-carbaldehyde,
and 9H-fluorene-2-carbaldehyde were purchased from Tokyo
Chemical Industry Co., LTD. 9-p-Tolyl-9H-carbazole-3-carbalde-
hyde and 9-(4-methoxyphenyl)-9H-carbazole-3-carbaldehyde
were synthesized according to the literatures [22,23]. Zn(Ac)2, ace-
tic anhydride and all solvents were obtained from Guangzhou
chemical reagent company. The solvents were dried using standard
procedures. All other reagents were used as received from com-
mercial sources, unless otherwise stated.
5.2. Characterization
Melting points were determined using an Electro-thermal IA
900 apparatus and the thermometer was uncorrected. FT-IR spec-
tra were recorded on a Perkin–Elmer Fourier transform infrared
spectrometer and measured using KBr pellet. 1H NMR spectra were
determined in CDCl3 with a Bruker DRX 400 MHz spectrometer.
Chemical shifts (d) were given relative to tetramethylsilane
(TMS). The coupling constants (J) were reported in Hz. Elemental
analyses were recorded with a Perkin–Elmer 2400 analyzer. ESI-
Ms spectra were performed with a FINNIGAN Trace DSQ mass
spectrometer at 70 eV. Fluorescence emission spectra of these
samples were measured with
a FLSP920 spectrophotometer.
Experiment was monitored by TLC. Column chromatography was
carried out on silica gel.
5.3. General procedure for compound A
2-Methyl-8-hydroxyl-quinoline (2.0 mmol) and organic alde-
hydes (2.0 mmol) were dissolved in 10 ml of acetic anhydride.
The mixture was stirred (magnetic stir bar) at 125 °C under a nitro-
gen atmosphere for 40 h and a brown precipitate was obtained.
After cooling, the mixture was subsequently poured into 50 ml of
ice-water and stirred overnight. The yellow solid obtained was fil-
tered off and then purified by column chromatography on silica gel
(200–300 mesh) using ethyl acetate/petroleum ether as eluant to
give the product A.
Fig. 7. The EL spectra, luminescence–voltage curves and efficiency–voltage curves
for samples of 2, 3, and 4 in the device D.

X. Ouyang et al. / Journal of Organometallic Chemistry 694 (2009) 3511–3517
3517
A1: Yield, 61.2%; m.p. 147–148 °C; FT-IR (KBr)
m
(cmꢀ1): 3386,
source organic molecule gas deposition system. There are different
materials in every source, and the temperature of each source can
be controlled independently. Different organic materials were
deposited on the ITO-coated glass substrate according to the
designed structure, LiF buffer layer and Al were deposited as a
co-cathode under a pressure of 5 ꢂ 10ꢀ4 Pa. Electroluminescent
spectra and commission international De L’ Eclairage (CIE) coordi-
nation of these devices were measured by a PR655 spectra scan
spectrometer. The luminescent brightness (L)–current (I)–voltage
(V) characteristics were recorded simultaneously with the mea-
surement of the EL spectra by combining the spectrometer through
a Keithly model 2400 programmable voltage-current source. The
current efficiency (E) was decided by this formula, E = Ls/I, then
3030, 2951, 1624, 1589–1510, 1334, 1240; MS (ESI) m/z: 443
(M+H), 1H NMR (CDCl3, 400 MHz) d: 3.86 (s, 3H), 7.32 (d,
J = 7.6 Hz, 2H), 7.34 (d, J = 7.6 Hz, 1H), 7.37–7.40 (m, 2H), 7.41 (d,
J = 7.4 Hz, 1H), 7.42–7.56 (m, 2H), 7.59 (d, J = 16.0 Hz, 1H) 7.80–
7.82 (m, 2H), 7.83 (d, J = 7.8 Hz, 2H), 7.85 (d, J = 8.2 Hz, 1H),
8.16–8.20 (m, 2H), 7.30 (d, J = 16.0 Hz, 1H), 8.32 (d, J = 8.0 Hz,
1H), 10.40 (s, 1H). Anal. Calc. for C30H22N2O2: C, 81.43; H, 5.01;
N, 6.33. Found: C, 81.52; H, 5.04; N, 6.27%.
A2: Yield, 62.5%; m.p. 149–150 °C; FT-IR (KBr)
m
(cmꢀ1): 3389,
3029, 2954, 1645, 1593–1507, 1335; MS (ESI) m/z: 427 (M+H),
1H NMR (CDCl3, 400 MHz) d: 2.36 (s, 3H), 7.10 (d, J = 7.6 Hz, 1H),
7.12–7.32 (m, 2H), 7.34 (d, J = 8.0 Hz, 2H), 7.38 (d, J = 7.4 Hz, 1H),
7.53–7.54 (m, 2H), 7.66 (d, J = 16.0 Hz, 1H), 7.70–7.79 (m, 2H),
7.93 (d, J = 7.8 Hz, 2H), 7.99 (d, J = 8.2 Hz, 1H), 8.02–8.10 (m, 2H),
8.28 (d, J = 16.0 Hz, 1H), 8.30 (d, J = 8.0 Hz, 1H), 10.02 (s, H). Anal.
Calc. for C30H22N2O: C, 84.48; H, 5.20; N, 6.57. Found: C, 84.61;
H, 5.23; N, 6.51%.
the power efficiency (gP) was calculated by formula of gP = pL/IV,
where L is the luminescent brightness, s is the luminescent area,
I is the current, and V is the voltage. The layer thicknesses of the
deposited materials were monitored in situ using a model FTM-V
oscillating quartz thickness monitor made in Shanghai, China. All
the measurements were carried out at room temperature under
ambient conditions.
A3: Yield, 41%; m.p. 164–166 °C; 1H NMR (CDCl3, 400 MHz) d:
8.13 (d, J = 8.80 Hz, 1H), 7.79–7.85 (m, 4H), 7.67 (d, J = 8.80 Hz,
2H), 7.58 (d, J = 7.2 Hz, 1H), 7.38–7.48 (m, 3H), 7.28–7.36 (m,
2H), 7.18 (d, J = 6.4 Hz, 1H), 3.97 (s, 2H); FT-IR (KBr)
m
(cmꢀ1):
Acknowledgements
3040, 1683, 1633, 1555, 960; MS (ESI) m/z (%): 337.4 (M+H). Anal.
Calc. for C24H17NO: C, 85.94; N, 4.18; H, 5.11. Found: C, 85.90; N,
4.20; H, 5.15%.
Financial support from the National Natural Science Foundation
of China (Nos. 20671036, 2007A010500008 and 2008B010800030)
are gratefully acknowledged. Ouyang X H would like to acknowl-
edge the receipt of the Doctorate Foundation from South China
University of Technology (SCUT), Guangzhou and the China Schol-
arship Council. J.L. is a Cheung Kong Guest Chair Professor associ-
ated with SCUT.
A4: Yield, 0.30 g, 42%. m.p. 169–171 °C; 1H NMR (CDCl3,
400 MHz): d 8.76 (d, J = 9.48 Hz, 1H), 8.68 (d, J = 8.80 Hz, 1H),
8.52 (d, J = 15.92 Hz, 1H), 8.31–8.33 (m, 1H), 7.28–7.36 (m, 2H),
8.17 (d, J = 8.50 Hz, 3H), 8.10 (s, 1H), 7.94 (d, J = 7.35 Hz, 1H),
7.61–7.75 (m, 5H), 7.40–7.50 (m, 2H), 7.32 (d, J = 7.29 Hz, 1H),
7.19 (d, J = 7.62 Hz, 1H); FT-IR (KBr)
m
(cmꢀ1): 3048, 1687, 1630,
1562, 1458, 961; MS (ESI) m/z (%): 348.5 (M+H). Anal. Calc. for
C25H17NO: C, 86.43; N, 4.03; H, 4.93. Found: C, 86.40; N, 4.03; H,
4.91%.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.06.022.
5.4. General Procedure for compounds 1, 2, 3 and 4
References
Zn(II) complexes were prepared from A1 to A4 and zinc acetate
dihydrate in DMF. Zinc acetate dihydrate (2.2 mmol, 0.413 g) was
dissolved in 45 mL anhydrous methanol. The Zn(II) solution was
added dropwise into the DMF (90 mL) solution of 1 mmol of A
and kept stirring for 24 h. The yellow precipitate was filtered off,
washed with methanol and dried in vacuum to afford 1, 2, 3 and 4.
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m
(cmꢀ1): 3025, 2954,
1648, 1592–1514, 1336, 1107, 515, 455; MS (FAB) m/z: 949 (M+H).
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3: Yield, 91%; m.p. >300 °C; IR (KBr)
m
(cmꢀ1): 3050, 2920, 2854,
1622, 1555, 1102, 520, 468; MS (FAB): 732.2 (MꢀH). Anal. Calc. for
ZnC48H32N2O2: C, 78.58; N, 3.82; H, 4.37. Found: C, 78.43; N, 3.80;
H, 4.33%.
4: Yield, 91%; m.p. >300 °C; IR (KBr)
m
(cmꢀ1): 3050, 1622, 1555,
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The ITO-coated glass substrate was first immersed sequentially
in ultrasonic baths of acetone, alcohol and deionized water for
10 min, respectively, and then dried in an oven. The resistance of
a sheet ITO is 50
X/h. The devices were fabricated in a multi-