2-Phenylpyrimidine skeleton-based electron-transport materials for extremely efficient green organic light-emitting devices

Article abstract of DOI:10.1039/b812270a

2-Phenylpyrimidine skeleton-based multifunctional electron-transport materials are designed and synthesized. By using these materials and green phosphorescent emitter, fac-tris(2-phenylpyridine)iridium [Ir(ppy)₃], extremely efficient green organic light-emitting devices are developed. The devices show the efficiencies of 128 lm W^-1 (105 cd A^-1) at 100 cd m^-2 and 96 lm W^-1 (99 cd A^-1) at 1000 cd m^-2. The Royal Society of Chemistry.

Full text of DOI:10.1039/b812270a

Electronic Supplementary Information for:
2-Phenylpyrimidine skeleton-based electron-transport materials for extremely efficient
green organic light-emitting devices
Hisahiro Sasabe, Takayuki Chiba, Shi-Jian Su, Yong-Jin Pu, Ken-ichi Nakayama and Junji Kido
Department of Organic Device Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata
992-8510, Japan.
General Procedures. The optimized structures and single-point energies (HOMO, LUMO
energies) were calculated by Gaussian031 at the RB3LYP 6-31G(d) and 6-311+G(d,p) levels,
respectively. 1H NMR spectra were recorded on JEOL 400 (400 MHz) spectrometer. Mass
spectra were obtained using a JEOL JMS-K9 mass spectrometer. Differential scanning
calorimetry (DSC) was performed using a Perkin-Elmer Diamond DSC Pyris instrument under
nitrogen atmosphere at a heating rate of 10°C min–1. Thermogravimetric analysis (TGA) was
undertaken using a SEIKO EXSTAR 6000 TG/DTA 6200 unit under nitrogen atmosphere at a
heating rate of 10°C min–1. UV-Vis spectra were measured using a Shimadzu UV-3150
UV-vis-NIR spectrophotometer.
Photoluminescence spectra were measured using a
FluroMax-2 (Jobin-Yvon-Spex) luminescence spectrometer. HOMO levels were determined
by photoelectron yield spectroscopy (OPTEL). The phosphorescent spectra were measured by
using a streak camera (C4334 from Hamamatsu Photonics) at 4.2 K. The current
density–luminance–voltage characteristics of the OLEDs were measured by Keithley source
meter 2400 and Konica Minolta CS-200, respectively. Electroluminescence (EL) spectra were
taken by an optical mutichannel analyzer, Hamamatsu PMA 11.
(1) M. J. Frisch et al. Gaussian 03; Gaussian Inc.: Pittsburgh, PA 2003.
Synthesis of 3. 3,5-Dichlorophenyl boronic acid (5.03 g, 26.4 mmol) and 2 (2.70 g, 12.0
mmol) were added to a round bottom flask. Acetonitrile (190 mL) and aqueous Na2CO3 (1 M,
60 mL) were added and nitrogen bubbled through the mixture for 1 hour. Then, PdCl2(PPh3)2
(0.42 g, 0.60 mmol) was added and the resultant mixture was stirred for 9 hours at 70 ˚C under
N2 flow. The precipitate was filtered, and washed with water and methanol. The resulting
off-white solid was dissolved in reflux toluene 450 mL, filtered through silica-gel pad (50 cc)
and washed with toluene 50 mL. After the clear filtrate was concentrated to 50 mL, the
precipitate was collected, washed with hexane, dried in vacuo to afford 3 (3.75 g, 70%) as a
1
white solid: H NMR (400 MHz, CDCl3) δ 8.77–8.64 (m, 2H) 8.15 (d, J=1.4 Hz, 4H), 7.86 (s,
1H), 7.58–7.53 (m, 5H) ppm; MS: m/z 446 [M]+.
1

Synthesis of 1. 3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (16.5 g, 80.4 mmol)
and 3 (3.0 g, 6.7 mmol) were added to a round bottom flask. 1,4-Dioxane (85 mL) and
aqueous K3PO4 (1.35 M, 35 mL) were added and nitrogen bubbled through the mixture for 1
hour. Then, Pd2(dba)3 (0.73 g, 0.80 mmol) and PCy3 (0.54 g, 1.92 mmol) were added and the
resultant mixture was vigorously stirred for 30 hours at reflux temperature under N2 flow. The
precipitate was filtered, and washed with water and methanol. The resulting off-white solid
was purified by chromatography on silica gel (eluent: CHCl3/CH3OH = 100:2, 100:2.5, 100:4 to
100:10 v/v) to afford 1a (3.43 g, 83%) as a white solid: 1H NMR (400 MHz, CDCl3): δ 9.03 (d,
4H, J=2.3 Hz), 8.76–8.69 (m, 6H) 8.51 (d, 4H, J=1.4 Hz), 8.17 (s, 1H), 8.05 (dt, 4H, J=2.3, 7.8
Hz), 7.93 (t, 2H, J=1.4 Hz), 7.61–7.56 (m, 3H), 7.48 (dd, 4H, J=4.8, 7.8 Hz) ppm; MS: m/z 617
[M]+; Anal. Calcd for C42H28N6: C, 81.80; H, 4.58; N, 13.63%. Found: C, 81.54; H, 4.37; N,
13.64%. UV-vis (film): λmax = 260, 323 nm. For 1b: 1H NMR (400 MHz, CDCl3): δ 8.79 (dd,
8H, J=1.8, 4.6 Hz), 8.75 (dd, 2H, J=1.8, 5.0 Hz), 8.57 (d, 4H, J=1.8 Hz), 8.15 (s, 1H), 8.03 (t,
2H, J=1.8 Hz), 7.68 (dd, 8H, J=1.8, 4.6 Hz), 7.60–7.59 (m, 3H) ppm; MS: m/z 617 [M]+. Anal.
Calcd for C42H28N6: C, 81.80; H, 4.58; N, 13.63%. Found: C, 81.90; H, 4.37; N, 13.72%.
UV-vis (film): λmax = 263, 320 nm.
B3PyPPM-uv
B4PyPPM uv
200 250 300 350 400 450 500 550 600
wavelength (nm)
200 250 300 350 400 450 500 550 600
wavelength (nm)
Figure S-1. UV–vis spectra of vacuum deposited film of 1. No emission was observed from
vaccum deposited film of 1 (λex = 250 nm).
2

440 nm
T1 = 2.81 eV
400
450
500
550
600
650
wavelength (nm)
Figure S-2. Phosphorescent spectrum of vacuum-deposited film of 1a at 4.2 K, measured by
streak camera with a N2 gas laser (337 nm) as an excitation light.
50
40
10
30
20
1
0.001
0.01
10
0
Time (sec)
0
0.005
0.01
Time (sec)
0.015
0.02
Figure S-3. Transient photocurrent profile for 1a measured at room temperature. Electric field
(E1/2) was 624 [V/cm]1/2. Sample thickness was 8.8 µm. Inset: Double logarithmic plot.
10-6
Alq3
B3PyPPM
B4PyPPM
10-7
500
550
600
650
700
750
800
Electric Field E1/2 [V/cm]1/2
Figure S-4. Electron mobility of BPyPPM derivatives and Alq3.
3