New Phosphorescent Heteroleptic Iridium (III) Complex
[189]/19
standard. CV measurements were performed with a CHI 600C potentiostat (CH Instru-
ments), which is equipped with a platinum disc as the working electrode, a platinum wire
as the counter electrode, and a Ag/AgCl as the reference electrode, at a scan rate of 100 mV
s−1 using anhydrous MC and 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) as
the solvent and electrolyte, respectively. All electrochemical experiments were carried out
at room temperature. The potentials were referenced to the ferrocene/ferrocenium redox
couple (Fc/Fc+). It was assumed that the redox potential of Fc/Fc+ had an absolute energy
level of -4.8 eV under vacuum.
Synthesis of bis[2,4-diphenylquinoline]iridium(III) [5-(2ꢀ-pyridyl)tetrazolate]
The cyclometalated Ir(III) μ-chloro-bridged dimer (2) (0.50 g, 0.32 mmol) was placed
in a flask and dispersed in dichloromethane and ethanol. 5-(2ꢀ-Pyridyl)tetrazole (0.23 g,
1.60 mmol) was added to the solution, and the mixture was stirred at room temperature for
8 h. After completion of the reaction crude product was washed with deionized water and
extracted with dichloromethane. The solvent was removed under reduced pressure and the
crude product was purified by column chromatography on silica gel using EA/MC/hexane
(2:3:5 v/v) as an eluent to give orange solid (0.28 g, 54%). 1H- NMR (300 MHz, CDCl3):
δ (ppm): 8.11-7.91 (m, 7H), 7.74-7.67 (m, 3H), 7.56 (s, 10H), 7.41-7.39 (d, 1H), 7.26-7.04
(m, 6H), 6.95-6.75 (m, 4H), 6.64-6.62 (d, 1H). 13C-NMR (CDCl3): δ 170.4, 169.3, 163.0,
154.6, 151.4, 151.0, 149.7, 148.5, 147.9, 147.7, 147.5, 146.9, 138.5, 137.4, 136.2, 134.6,
131.5, 130.5, 130.1, 129.9, 129.8, 129.5, 129.3, 129.1, 129.0, 128.9, 127.8, 127.3, 126.9,
126.5, 126.1, 125.8, 125.2, 122.5, 122.4, 117.9, 117.3. HRESI-MS [M+H]+: m/z calcd for
899.05, found 899.05.
PhOLEDs Fabrication and Measurements
The indium tin oxide (ITO) was coated onto the glass substrate (20 ꢀ/squre and
110 nm). The ITO glass was UV-ozone treated for 20 min, the PEDOT:PSS ((poly-
ethylenedioxythiophene)-polystyrenesulfonate (H.C.Starck, ◦Clevios P VP AI4083)) was
spin-cast onto the substrate and immediately baked at 150 C for 20 min on a hot plate
in air condition. The emitting layer solutions composed of dopant and PVK:PBD:SPPO1
(40:40:20 or 50:30:20) blends in chlorobenzene were spin coated on top of the PEDOT:PSS
in a glove box and annealed at 80 ◦C for 30 min. Then, Bphene (20 nm), LiF (1 nm) and
Al (100 nm) were thermally deposited under high vacuum (< 5.0 × 10−6 Torr). The film
thickness was measured with α-Step IQ surface profiler (KLA Tencor, SanJose, CA). To
characterize the performance of PhOLEDs, the current density-voltage-luminance (J-V-L)
characteristic were measured by using a current/voltage source meter (Keithley 236) and
an optical power meter (CS-1000).
Results and Discussion
The target heteroleptic yellow emitting (DPQ)2Ir(PyTz) was synthesized according to the
synthetic route as shown in Scheme 1. The ancillary ligand 5-(2ꢀ-Pyridyl)tetrazole is a
known compound and it can be prepared easily in single step from commercially available
2-cyanopyridine and sodium azide and the compound 2 was synthesized according to the
previous report. The compound 2 can be easily converted to heteroleptic Ir(III) complex
by simple approach rather than sophisticated and high temperature reaction conditions.