Synthesis and luminescence of poly (phenylacetylene) s with ...

Synthesis and Luminescence of Poly(phenylacetylene)s with Pendant 

Iridium Complexes and Carbazole Groups 

JOSÉ VICENTE, 1 JUAN GIL-RUBIO, 1 GUIJIANG ZHOU, 1 * HENK J. BOLINK, 2 JOAQUÍN ARIAS-PARDILLA 3 

1 Grupo de Química Organometálica, Departamento de Química Inorgánica, Facultad de Química, 

Universidad de Murcia, Murcia E–30071, Spain 

2 Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, P.O. Box 22085, 46071 Valencia, Spain 

3 Centre for Electrochemistry and Intelligent Materials (CEMI), Universidad Politécnica de Cartagena, 

ETSII, E-30203, Cartagena, Spain 

Received 29 March 2010; accepted 25 May 2010 

DOI: 10.1002/pola.24159 

Published online in Wiley InterScience (www.interscience.wiley.com). 

ABSTRACT: Poly(phenylacetylene)s containing pendant phosphorescent 

iridium complexes have been synthesized and their 

electrochemical, photo- and electroluminescent properties studied. 

The polymers have been synthesized by rhodium-catalyzed 

copolymerization of 9-(4-ethynylphenyl)carbazole (CzPA) and 

phenylacetylenes (C^N) 2 Ir(j 2 -O,O 0 -MeC(O)CHC(O)C 6 H 4 CBCH-4) 

(C^N ¼ j 2 -N,C 1 -2-(pyridin-2-yl)phenyl (Ir ppy PA) or j 2 -N,C 1 -2-(isoquinolin-1-yl)phenyl 

(Ir piq PA)). In addition, organic poly(phenylacetylene)s 

with pendant carbazole groups have been 

synthesized by rhodium-catalyzed copolymerization of CzPA 

and 1-ethynyl-4-pentylbenzene. Complex (C^N) 2 Ir(j 2 -O,O 0 - 

MeC(O)CHC(O)Ph) (Ir piq Ph; C^N ¼ 2-(isoquinolin-1-yl)phenyl-j 2 - 

N,C 1 ) was prepared and characterized. While the copolymers of 

the Ir ppy series were weakly phosphorescent, those of the Ir piq 

series displayed at room temperature intense emissions from the 

carbazole (fluorescence) and iridium (phosphorescence) emitters, 

being the latter dominant when the spectra were recorded using 

polymer films. Triple layer OLED devices employing copolymers 

of the Ir piq series or the model complex Ir piq Ph yielded electroluminescence 

with an emission spectra originating from the 

iridium complex and maximum external quantum efficiencies of 

0.46% and 2.99%, respectively. VC 2010 Wiley Periodicals, Inc. 

J Polym Sci Part A: Polym Chem 48: 3744–3757, 2010 

KEYWORDS: electrochemistry; iridium complexes; metal-polymer 

complexes; photophysics; polyacetylenes 

INTRODUCTION Transition-metal catalyzed polymerization of 

alkynes has led to a profusion of polymers ranging from 

polyacetylene to sophisticated functional polymers. 1–4 The 

groups attached to the conjugated backbone not only afford 

functionality to the polymer, but also determine the conformation 

and degree of conjugation of the main chain. 3,5–11 In 

consequence, by adequate choice of the substituents of the 

starting alkyne, polyacetylenes can be endowed with interesting 

physico-chemical properties, for example, gas permeability, 

photoconductivity, liquid crystallinity, photo- and 

electroluminescence, optical nonlinearity, chromism or chiral 

recognition. 1–3,12–14 

The attachment of metal complexes to conjugated polymers 

is recognized as a way to produce new materials with 

properties that result of the combination of the redox or 

photophysical activity of the metal complexes with those of 

the unsaturated backbone. 15–18 In particular, polyacetylenes 

containing phosphorescent transition-metal complexes 

attached to the main chain are potential candidates to present 

interesting electrooptical properties. Surprisingly, very 

few polyacetylenes with pendant metal complexes have been 

described. Among them, the most studied are poly(ethynylferrocene) 

or poly(ethynylrutenocene). 19–28 Other metallopolyacetylenes 

reported are poly(phenylacetylene)s bearing 

Zn phorphirine 29 or Ru tris(imine) 30 complexes. We have 

reported polyacetylenes with pendant 2,2 0 -bipyridin-5- 

yl(bpyl) donor groups and their derivatives resulting of coordination 

of the bpyl group to Ru(bpy) 2þ 

2 or Mo(CO) 4 metal 

centers. 31 

Doping conjugated polymers with phosphorescent heavymetal 

complexes is used to improve the electroluminescence 

efficiency of polymer electroluminescent devices (PLEDs). As 

in these systems both singlet and triplet excitons are captured, 

the internal efficiency of the devices can approach a 

theoretical value of 100%. 32–35 Recent studies have demonstrated 

that covalent binding of the heavy-metal complexes 

to the polymer backbone may improve remarkably the electroluminescent 

performance of these materials. 13 Following 

this approach, Ir, 36–57 Pt 52,58,59 or Re 60 complexes have been 

incorporated in polyfluorenes, poly(p-phenylene)s, polycarbazoles 

or polyolefins as part of the main chain or as subsituents 

in side chains. Some of these organometallic polymers 

*Present address: Department of Chemistry, Faculty of Science, Xi’an Jiao Tong University, Xi’an 710049, People’s Republic of China. 

Correspondence to: J. Gil-Rubio (E-mail: jgr@um.es) or G. Zhou (E-mail: zhougj@mail.xjtu.edu.cn) 

Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 3744–3757 (2010) VC 2010 Wiley Periodicals, Inc. 

3744 INTERSCIENCE.WILEY.COM/JOURNAL/JPOLA

ARTICLE 

Materials 

[Ir(piq)(l–Cl)] 2 (piq ¼ j 2 -N,C 1 -2-(isoquinolin-1-yl)phenyl), 92 

Ir ppy PA, 93 Ir piq PA 93 and [Rh(l–OMe)(NBD)] 2 (NBD ¼ norbornadiene), 

94 were prepared using reported methods. Other 

reagents were obtained from commercial sources and used 

without further purification. THF was distilled over sodiumbenzophenone 

ketyl, and CH 2 Cl 2 was distilled over CaH 2 .All 

reactions were carried out under an inert atmosphere of 

nitrogen at room temperature unless otherwise stated. The 

polymeric samples for elemental analysis were purified by 

reprecipitation and dried in a vacuum oven. 

CHART 1 Structures of the organometallic phenylacetylenes. 

exhibit an outstanding performance as the emitting layer in 

PLEDs. 

Polyacetylenes derived from monosubstituted alkynes 

present in general very weak luminescence. 2,61–63 However, 

fluorescent polyacetylenes have been obtained by attaching 

fluorophores such are carbazole, 64–68 fluorene, 61,69 4-ethynylphenyl, 

70 bi- or terphenyl, 71,72 antryl, 73–75 phenantryl, 74 

pyrenyl 76 or silole 77 to the side chains. Some of these 

polymers present electroluminescence. 64,70 In contrast, poly 

(disubstituted alkyne)s present stronger fluoro- and electroluminescence 

than those derived from monosubstituted 

alkynes. 1,2,13,61,63,78–89 Unfortunately, the polymerization of 

disubstituted alkynes is limited to alkynes containing functional 

groups which are compatible with the highly reactive 

early-transition metal catalysts used. 3,90,91 

In this work we describe the synthesis of the first poly(phenylacetylene)s 

containing pendant Ir(III) complexes. These 

polymers have been prepared by (i) polymerization of 

phenylacetylenes Ir ppy PA or Ir piq PA (Chart 1) or (ii) copolymerization 

of these organometallic phenylacetylenes with 

9-(4-ethynylphenyl)carbazole. All the polymers have been 

characterized and their electrochemical, photophysical and 

electroluminescent properties studied as well. These polymers 

are, to the best of our knowledge, the first polyacetylenes 

reported showing metal-based phosphorescence. 

EXPERIMENTAL 

9-(4-Bromophenyl)carbazole 

A mixture of carbazole (500 mg, 2.99 mmol), 4-bromoiodobenzene 

(930 mg, 3.29 mmol), CuI (570 mg, 2.98 mmol), 

1,10-phenanthroline (580 mg, 2.93 mmol) and KOH 

(750 mg, 13.4 mmol) in p-xylene (25 mL) was stirred at ca. 

140 C for two days under nitrogen. The resulting suspension 

was filtered and CH 2 Cl 2 (80 mL) was added to the filtrate. 

The organic solution was washed with water and dried 

over MgSO 4 . After removing the solvent, the crude product 

was purified on a silica gel column with n-hexane/CH 2 Cl 2 

(5:1 v/v) as eluent. Evaporation of the solvent gave colorless 

crystals (620 mg, Yield: 64%). Mp 149–150 C. 

1 H NMR (300 MHz, CDCl 3 , d, ppm): 8.13 (d, J ¼ 7.8 Hz, 2H, 

Ar), 7.72 (d, J ¼ 8.7 Hz, 2H, Ar), 7.44 (d, J ¼ 8.7 Hz, 2H, Ar), 

7.41–7.34 (m, 4H, Ar), 7.31–7.24 (m, 2H, Ar). 

13 C{ 1 H} NMR 

(100 MHz, CDCl 3 , d, ppm): 140.6, 136.8, 133.1, 128.7, 126.1, 

123.5, 120.9, 120.4, 120.2, 109.5 (Ar). Anal. Calcd. for 

C 18 H 12 BrN: C 67.10, H 3.75, N 4.35. Found: C 66.81, H 3.71, 

N 4.42. The spectroscopic data of the compound agree with 

those previously reported. 95,96 

9-(4-(2-trimethylsilylethynyl)Phenyl)carbazole 

9-(4-bromophenyl)carbazole (500 mg, 1.55 mmol), CuI 

(20 mg, 0.11 mmol) and [PdCl 2 (PPh 3 ) 2 ] (20 mg, 0.028 

mmol) were added to Et 3 N (20 mL) under nitrogen. Then 

ethynyltrimethylsilane (0.5 mL, 3.5 mmol) was added to the 

mixture. The reaction mixture was stirred at room temperature 

for 30 min and then heated at 80 C overnight. The 

resulting suspension was filtered and the filtrate was evaporated 

to dryness. The crude was purified on a silica gel 

column with n-hexane/CH 2 Cl 2 (6:1 v/v) as eluent. Evaporation 

of the solvent gave colorless crystals (421 mg, Yield: 

80%). Mp 150–152 C. 

1 H NMR (200 MHz, CDCl 3 , d, ppm): 8.17–8.12 (m, 2H, Ar), 

7.73–7.69 (m, 2H, Ar), 7.56–7.51 (m, 2H, Ar), 7.43–7.40 (m, 

4H, Ar), 7.34–7.28 (m, 2H, Ar), 0.31 (s, 9H, TMS). 

13 C{ 1 H} 

NMR (100 MHz, CDCl 3 , d, ppm): 140.5, 137.7, 133.5, 126.7, 

126.0, 123.5, 122.1, 120.4, 120.2, 109.7 (Ar), 104.2, 95.4 

(CBC), 0.1 (TMS). IR (KBr, cm –1 ): m(CBC) 2159. Anal. Calcd. 

for C 23 H 21 NSi: C 81.37, H 6.23, N 4.13. Found: C 81.14, H 

6.56, N 4.23. 

CzPA 

9-(4-(2-Trimethylsilylethynyl)phenyl)carbazole (420 mg, 1.24 

mmol) was dissolved in MeOH/THF (15 mL, 1:1 v/v) under 

nitrogen. Then 1 N KOH in H 2 O (1.4 mL) was added to the 

mixture. The reaction mixture was stirred at room temperature 

for about 30 min. Then the solvent was removed and 

the residue was extracted with CH 2 Cl 2 (100 mL). The organic 

SYNTHESIS AND LUMINESCENCE OF POLY(PHENYLACETYLENE)s, VICENTE ET AL. 3745

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA 

solution was washed with water (3 100 mL) and dried 

over MgSO 4 . After removing the solvent, the product was 

recrystallized from CH 2 Cl 2 and n-pentane to give colorless 

crystals (298 mg, Yield: 90%). Mp 106–107 C. 

1 H NMR (200 MHz, CDCl 3 , d, ppm): 8.17–8.14 (m, 2H, Ar), 

7.75–7.73 (m, 2H, Ar), 7.57–7.55 (m, 2H, Ar), 7.44–7.42 (m, 

4H, Ar), 7.33–7.29 (m, 2H, Ar), 3.19 (s, 1H, CBCH). 

13 C{ 1 H} 

NMR (100 MHz, CDCl 3 , d, ppm): 140.5, 138.1, 133.7, 126.8, 

126.1, 123.6, 121.0, 120.4, 120.3, 109.7, 82.9 (CBC), 78.1 

(CBC). IR (KBr, cm –1 ): m(BC–H) 3262, m(CBC) 2106. Anal. 

Calcd. for C 20 H 13 N: C 89.86, H 4.90, N 5.24. Found: C 89.56, 

H 4.86, N 5.29. The spectroscopic data of the compound 

agree with those previously reported. 97 

PIr ppy PA 

Under nitrogen atmosphere, Ir ppy PA (100 mg, 0.15 mmol), 

PPh 3 (1 mg, 0.0038 mmol) and DMAP (2 mg, 0.016 mmol) 

were dissolved in THF (10 mL). Then [Rh(l–OMe)(NBD)] 2 

(2 mg, 0.0044 mmol) was added and the reaction mixture 

was stirred overnight at room temperature. Then, the solvent 

was removed under reduced pressure and the residue 

dissolved in CH 2 Cl 2 (ca. 2 mL). The solution was added dropwise 

to vigorously stirred methanol (30 mL), and the resulting 

orange precipitate was collected by centrifugation, 

washed with methanol (3 20 mL) and dried under 

vacuum to give an orange solid (70 mg, Yield: 70%). 

1 H NMR (200 MHz, CD 2 Cl 2 , d, ppm): 8.31 (m, br, Ar), 8.00– 

5.80 (m, br, Ar, and C¼CH), 5.45 (s, br, COCHCO), 2.00–1.30 

(s, br, Me). Anal. Calcd. for [C 34 H 25 IrN 2 O 2 ] n : C 59.55, H 3.67, 

N 4.08. Found: C 58.55, H 3.56, N 3.97. 

PIr ppy CzPA1 

Under nitrogen atmosphere, Ir ppy PA (100 mg, 0.15 mmol), 

CzPA (8 mg, 0.030 mmol), PPh 3 (1 mg, 0.0038 mmol) and 

DMAP (2 mg, 0.016 mmol) were dissolved in THF (10 mL). 

Then [Rh(l–OMe)(NBD)] 2 (2 mg, 0.0044 mmol) was added 

and the reaction mixture was stirred overnight at room temperature. 

Then, the solution was concentrated under reduced 

pressure up to about 2 mL and added dropwise to 

vigorously stirred methanol (30 mL). The orange precipitate 

was collected by centrifugation, washed with methanol (3 

20 mL) and dried under vacuum, to give an orange solid 

(100 mg, Yield: 93%). 

1 H NMR (300 MHz, CD 2 Cl 2 , d, ppm): 8.60–5.00 (m, br, Ar, 

C¼CH and COCHCO), 2.00–1.20 (br, Me). Anal. Calcd. for 

[(C 34 H 25 IrN 2 O 2 ) 0.95 (C 20 H 13 N) 0.05 ] n : C 60.16, H 3.70, N 4.11. 

Found: C 60.47, H 3.79, N 4.08. 

PIr ppy CzPA2 

It was prepared from Ir ppy PA (77 mg, 0.11 mmol), CzPA 

(150 mg, 0.56 mmol), PPh 3 (3 mg, 0.011 mmol), DMAP 

(6 mg, 0.049 mmol) and [Rh(l–OMe)(NBD)] 2 (3 mg, 0.0066 

mmol) in THF (10 mL), following the same procedure as for 

PIr ppy CzPA1. The polymer was obtained as an orange solid 

(210 mg, Yield: 93%). 

1 H NMR (300 MHz, CDCl 3 , d, ppm): 8.60–5.00 (m, br, Ar, 

C¼CH and COCHCO), 2.00–1.10 (s, br, Me). Anal. Calcd. for 


Found: C 78.44, H 4.67, N 4.85. 

PIr ppy CzPA3 

It was prepared from Ir ppy PA (38.5 mg, 0.056 mmol), CzPA 





(172 mg, Yield: 91%). 



[(C 34 H 25 IrN 2 O 2 ) 0.10 (C 20 H 13 N) 0.90 (H 2 O) 0.3 ] n : C 81.71, H 4.74, 

N 4.90. Found: C 81.96, H 4.79, N 4.95. Water could no be 

completely removed by drying in a vacuum oven. 

PIr ppy CzPA4 

It was prepared from Ir ppy PA (19 mg, 0.028 mmol), CzPA 


(6 mg, 0.049 mmol) and [Rh(l–OMe)(NBD)] 2 (3 mg, 

0.0066 mmol) in THF (10 mL), following the same procedure 

as for PIr ppy CzPA1. The polymer was obtained as an orange 

solid (160 mg, Yield: 95%). 


C¼CH and COCHCO), 2.10–1.30 (s, br, Me); Anal. Calcd. for 

[(C 34 H 25 IrN 2 O 2 ) 0.05 (C 20 H 13 N) 0.95 (H 2 O) 0.7 ] n : C 82.64, H 5.03, 

N 4.89. Found: C 82.53, H 4.67, N 4.93. Water could no be 

completely removed by drying in a vacuum oven. 

PIr piq PA 

It was prepared from Ir piq PA (118 mg, 0.15 mmol), PPh 3 (1 

mg, 0.0038 mmol), DMAP (2 mg, 0.016 mmol) and [Rh(l– 

OMe)(NBD)] 2 (2 mg, 0.0044 mmol) in THF (10 mL), following 

the same procedure as for PIr ppy CzPA1. The polymer 

was obtained as an orange red solid (70 mg, Yield: 60%). 

1 H NMR (300 MHz, CDCl 3 , d, ppm): 8.90, 8.50, 8.15, 7.85, 

7.60, 7.35, 6.85, 6.60, 6.35 (several m, br, Ar), 5.80 (m, br, 

COCHCO), 1.85 (s, br, Me); the vinyl H signal could not be 

located due to its broadness. Anal. Calcd. for [C 42 H 29 Ir- 

N 2 O 2 ] n : C 64.19, H 3.72, N 3.56. Found: C 63.53, H 3.82, 

N 3.82. 

PIr piq CzPA1 

It was prepared from Ir piq PA (100 mg, 0.13 mmol), CzPA (7 

mg, 0.026 mmol), PPh 3 (1 mg, 0.0038 mmol), DMAP (2 mg, 

0.0044 mmol) and [Rh(l–OMe)(NBD)] 2 (2 mg, 0.0044 mmol) 

in THF (10 mL), following the same procedure as for PIr p- 

py CzPA1. The polymer was obtained as an orange red solid 

(70 mg, Yield: 65%). 




Found: C 64.60, H 4.05, N 3.75. 

PIr piq CzPA2 

It was prepared from Ir piq PA (100 mg, 0.13 mmol), CzPA 





ARTICLE 

PIr ppy CzPA1. The polymer was obtained as an orange red 

solid (116 mg, Yield: 86%). 


C¼CH and COCHCO), 1.89 (s, br, Me). Anal. Calcd. for 


Found: C 67.14, H 3.66, N 3.73. 

PIr piq CzPA3 






(219 mg, Yield: 92%). 




Found: C 79.76, H 4.51, N 4.58. 

PIr piq CzPA4 


(150 mg, 0.56 mmol), PPh 3 (3 mg, 0.011 mmol), DMAP (6 

mg, 0.049 mmol) and [Rh(l–OMe)(NBD)] 2 (3 mg, 0.0066 



(189 mg, Yield: 97%). 




Found: C 82.39, H 4.63, N 5.06. 

PIr piq CzPA5 





PIr ppy CzPA1. The polymer was obtained as orange solid 

(162 mg, Yield: 94%); 1 H NMR (200 MHz, CDCl 3 , d, ppm): 

8.90–5.00 (m, br, Ar, C¼CH and COCHCO), 2.00–1.20 (s, br, 

Me). Anal. Calcd. for [(C 42 H 29 IrN 2 O 2 ) 0.05 (C 20 H 13 N) 0.95 ] n : 

C 86.42, H 4.74, N 5.02. Found: C 85.52, H 4.74, N 5.30. 

PCzArPA1 

It was prepared from CzPA (130 mg, 0.49 mmol), 1-ethynyl- 

4-n-pentylbenzene (84 mg, 0.49 mmol), PPh 3 (4 mg, 0.011 

mmol), DMAP (8 mg, 0.065 mmol) and [Rh(l–OMe)(NBD)] 2 

(4 mg, 0.0088 mmol) in THF (10 mL), following the same 

procedure as for PIr ppy CzPA1. The polymer was obtained as 

a yellow solid (200 mg, Yield: 93%). 

1 H NMR (400 MHz, CDCl 3 , d, ppm): 7.96 (m, br, Ar), 7.50– 

5.60 (m, br, Ar and C¼CH), 2.60–2.00 (m, br, CH 2 Ar), 1.60– 

0.50 (m, br, (CH 2 ) 3 CH 3 ). Anal. Calcd. for [(C 20 H 13 N) 0.55 - 

(C 13 H 16 ) 0.45 ] n : C 90.13, H 6.44, N 3.43. Found: C 89.28, H 

6.69, N 3.49. The co-monomer ratio estimated from the 

integrals of the 1 H NMR spectrum was 0.5/0.5. 

PCzArPA2 

It was prepared from CzPA (100 mg, 0.37 mmol), 1-ethynyl- 

4-pentylbenzene (322 mg, 1.87 mmol), PPh 3 (8 mg, 0.031 

mmol), DMAP (16 mg, 0.13 mmol) and [Rh(l–OMe)(NBD)] 2 

(8 mg, 0.0177 mmol) in THF (10 mL), following the same 

procedure as for PIr ppy CzPA1. The polymer was obtained as 

a bright yellow solid (200 mg, Yield: 47%). 

1 H NMR (200 MHz, CDCl 3 , d, ppm): 7.99–5.70 (m, br, Ar and 

C¼CH), 2.60–2.00 (m, br, CH 2 Ar), 1.60–0.50 (m, br, 

(CH 2 ) 3 CH 3 ). Anal. Calcd. for [(C 20 H 13 N) 0.29 (C 13 H 16 ) 0.71 ] n : C 

90.34, H 7.63, N 2.03. Found: C 89.89, H 7.92, N 2.06. The 

co-monomer ratio estimated from the integrals of the 1 H 

NMR spectrum was 0.3/0.7. 

PCzPA 

Under a nitrogen atmosphere, CzPA (150 mg, 0.56 mmol), 

PPh 3 (3 mg, 0.011 mmol) and DMAP (6 mg, 0.049 mmol) 

were dissolved in THF (10 mL). Then [Rh(l–OMe)(NBD)] 2 

(3 mg, 0.0066 mmol) was added and the reaction mixture 

was stirred overnight at room temperature. Then, the reaction 

mixture was poured into vigorously stirred methanol 

(40 mL). The suspension was centrifugated and the deep-red 

solid was washed with methanol (3 25 mL) and dried 

under vacuum (140 mg, Yield: 93%). Anal. Calcd. for 

[(C 20 H 13 N)(H 2 O) 0.35 ] n C 87.79, H 5.05, N 5.12. Found: C 87.73, 

H 5.08, N 5.23. The NMR spectra could not be recorded due to 

the poor solubility of the polymer. 

Ir piq Ph 

A suspension of [Ir(piq)(l–Cl)] 2 (100 mg, 0.079 mmol), 

benzoylacetone (19 mg, 0.12 mmol) and Na 2 CO 3 (84 mg, 

0.79 mmol) in 2-ethoxylethanol (10 mL) was stirred at ca. 

110 C overnight under nitrogen. Water (40 mL) was added 

after cooling to room temperature. The red precipitate was 

collected by filtration and extracted with CH 2 Cl 2 (60 mL). 

The extract was dried over MgSO 4 , the solution evaporated 

to dryness and the crude product was purified by column 

chromatography on silica using n-hexane/CH 2 Cl 2 (1:3 v/v) as 

eluent. Evaporation of the resulting solution gave a red solid 

(90 mg, Yield: 75%). Mp 285–288 C. 

1 H NMR (300 MHz, CDCl 3 , d, ppm): 9.01 (m, 2H, piq and piq 0 

H8), 8.52 (d, J ¼ 6.4 Hz, 1H, piq 0 H3), 8.49 (d, J ¼ 6.4 Hz, 

1H, piq H3), 8.23 (d, J ¼ 8.0 Hz, 1H, piq 0 C 6 H 4 H6), 8.22 (d, 

J ¼ 8.0 Hz, 1H, piq C 6 H 4 H6), 7.92–7.88 (m, 2H, piq and piq 0 

H5), 7.72–7.66 (m, 6H, piq and piq 0 H6 and H7, C 6 H 5 H2), 

7.45 (d, J ¼ 6.5 Hz, 1H, piq 0 H4), 7.41 (d, J ¼ 6.4 Hz, 1H, piq 

H4), 7.32 (m, 1H, C 6 H 5 H4), 7.21 (m, 2H, C 6 H 5 H3), 6.95– 

6.89 (m, 2H, piq and piq 0 C 6 H 4 H5), 6.71–6.66 (m, 2H, piq 

and piq 0 C 6 H 4 H4), 6.44 (d, J ¼ 7.6 Hz, 2H, piq and piq 0 C 6 H 4 

H3), 5.89 (s, 1H, COCHCO), 1.89 (s, 3H, Me); 

13 C NMR 

(100 MHz, CDCl 3 , d, ppm): 186.7 (CO), 177.5 (CO), 169.42, 

169.37, 152.21, 152.15, 146.7, 140.9, 140.74, 140.68, 137.3, 

134.9, 133.9, 130.7, 130.1, 129.9, 129.7, 129.2, 128.9, 128.2, 

127.7, 127.4, 127.0, 126.5, 120.6, 120.4, 120.0, 97.7 

(COCHCO), 29.7 (Me). HRMS (EI, m/z): Calcd. for C 40 H 29 - 

IrN 2 O 2 762.1853; found, 762.1885 (M þ , D ¼ 4.2 ppm). 

Anal. Calcd. for C 40 H 29 IrN 2 O 2 : C 63.06, H 3.84, N 3.68. 

Found: C 63.08, H 3.72, N 3.68. 



Measurements 

Infrared spectra were recorded in the range 4000–200 cm –1 

on a Perkin-Elmer Spectrum 100 FTIR spectrometer with 

KBr pellets. C, H and N analyses were carried out with Carlo 

Erba 1108 and LECO CHS-932 microanalyzers. Thermal 

gravimetric analyses (TGA) were carried out in a TA Instruments 

SDT 2960 system at a heating rate of 10 Cmin 1 

under nitrogen. Differential scanning calorimetry (DSC) 

measurements were carried out in a TA Instruments modulated 

DSC 2920 system at a heating rate of 10 C min 1 

under nitrogen. gel permeation chromatography (GPC) measurements 

were carried out in a Waters Breeze system 

equipped with a Waters 2487 UV-visible detector and a set 

of three columns (Styragel HR3, HR4E and HR4) at 30 C. 

CHCl 3 was used as eluent at a flow rate of 1 mL min 1 . Calibration 

was performed by using a set of 11 polystyrene 

standards. NMR spectra were measured on Bruker Avance 

200, 300, and 400 instruments. 

1 H chemical shifts were 

referenced to residual CHCl 3 (7.26 ppm) and CHDCl 2 

(5.29 ppm). 

13 C{ 1 H} spectra were referenced to CDCl 3 (77.1 

ppm). Abreviations used: br ¼ broad; sh ¼ shoulder. 

UV-vis spectra were recorded in a Unicam UV500 spectrometer 

in 1 cm path length quartz cuvettes. Steady state 

emission spectra were measured on a Jobin Yvon Fluorolog 

3-22 spectrofluorimeter with a 450 W Xenon lamp, doublegrating 

monochromators and a Hamamatsu R-928P photomultiplier 

using 1 cm path length quartz fluorescence 

cuvettes. Low-temperature measurements were carried out 

using an Oxford Instruments OptistatDN cryostat and ITC503 

temperature controller. 

Cyclic voltammetry was carried out using an Autolab 

PGSTAT-100 potentiostat/galvanostat and a three electrodes 

cell. The working electrode was a platinum sheet having 

1cm 2 of surface area, the counter electrode was a Pt gauze 

and, as quasi-reference electrode, an Ag wire. The experiments 

were performed under a nitrogen atmosphere and at 

room temperature. The quasi-reference electrode was calibrated 

using the ferrocene/ferrocenium redox couple as an 

internal standard before measurements. Copolymer films 

were drop-casted on the pre-cleaned platinum sheet from a 

chloroform solution (concentration 1 mg/mL). Tetrabutylammonium 

perchlorate (TBAP, 0.1 M), and acetonitrile were 

used as electrolyte and solvent, respectively. Acetonitrile was 

dried using a molecular sieve UOP type 3A. 

RESULTS AND DISCUSSION 

Syntheses 

Phenylacetylenes Ir ppy PA or Ir piq PA (Scheme 1) polymerized 

in the presence of the initiator [Rh(l–OMe)(NBD)] 2 , 98 to give 

poly(phenylacetylene)s PIr ppy PA or PIr piq PA. The copolymerization 

of Ir ppy PA or Ir piq PA and 9-(4-ethynylphenyl)carbazole 

(CzPA) was carried out using the same initiator 

(Scheme 1) and different initial co-monomer molar ratios 

to give two series of random co-poly(phenylacetylene)s 

(PIr ppy CzPA1–4 and PIr piq CzPA1–5). Polymerization of 

CzPA led to the scarcely soluble poly(9-(4-ethynylphenyl)carbazole) 

(PCzPA). 99 Finally, copolymerization of CzPA and 

SCHEME 1 Synthesis of the organometallic poly(phenylacetylene)s. 

1-ethynyl-4-pentylbenzene (Scheme 2) produced soluble 

random co-poly(phenylacetylene)s PCzArPA1 and PCzArPA2. 

The polymers were isolated in 60–95% yields as orange 

(organometallic homopolymers), orange-red (organometallic 

copolymers), red (PCzPA) or yellow solids (organic copolymers). 

The relative amount of each co-monomer in the 

copolymers was approximately estimated from the C, H and 

N analyses. 100 The values (Table 1) are similar to the relative 

amount of each co-monomer in the starting monomer feed 

except for entries 2, 7 and 8, where the content of the carbazole-based 

monomer in the co-polymer is smaller than in the 

monomer feed, and for entries 12 and 13, where the estimated 

carbazole content is higher than in the monomer feed. 

All polymers are soluble in CH 2 Cl 2 and CHCl 3 , but their solubility 

decreased as the carbazole content increased, being 

homopolymer PCzPA only sligthly soluble in these 

solvents. 99 The molecular weight distribution of the new 

polymers was determined by GPC using CHCl 3 as mobile 


ARTICLE 

SCHEME 2 Synthesis of the carbazole-substituted poly(phenylacetylene)s. 

phase. The M n values were in the range 10,600–34,600 

except for PCzPA, which gives a smaller value (8400) corresponding 

to the polymer fraction that is soluble in CHCl 3 . 

The polydispersities were fairly narrow, as reported for 

poly(phenylacetylene)s obtained using the same initiator 

system. 

The model complex Ir piq Ph was obtained in 75% yield as a 

red solid by reacting [Ir(j 2 –piq) 2 (l–Cl)] 2 with benzoylacetone 

and sodium carbonate in 2-ethoxyethanol (Scheme 3). 

Characterization of the Polymers 

In the IR spectra of polymers, the bands corresponding to 

the m(BC–H) and m(CBC) vibrational modes of the corresponding 

alkynes Ir ppy PA, Ir piq PA, and CzPA (m(BCAH): 

3289, 3283, and 3622 cm 1 ; m(CBC): 2105, 2100, and 2106 

cm 1 , respectively) are not present. The copolymers display 

characteristic bands for both the carbazole group and the Ir 

complexes (Fig. 1), whose intensities are qualitatively in 

agreement with the estimated co-monomer proportions in 

the copolymers. 

The NMR spectra of organometallic polymers PIr ppy PA, 

PIr piq PA, PIr ppy CzPA1–4, and PIr piq CzPA1–5 displayed several 

broad multiplets corresponding to the aromatic, diketonate 

methine and methyl protons. The broadness of the signals 

was more pronounced as the content of the carbazole 

monomer increased. The signal of the vinylic proton of the 

main chain could not be located due to the broadness of the 

signals and the overlapping with the diketonate methine proton 

signal. The organic copolymers PCzArPA1 and 

PCzArPA2 displayed broad signals corresponding to the aromatic, 

alkyl, and vinyl protons. The latter appeared partially 

overlapped with the aromatic protons signals around 6 ppm, 

which is typical for a cis-transoidal configuration of the 

poly(phenylacetylene) chain. 101–105 The estimation of the 

degree of stereoregularity of the polyenic chain from the 

integrals of the aromatic and vinylic protons signals 101 was 

not possible due to the broadness of the signals. The 1 H 

NMR spectrum of polymer PCzPA could not be recorded due 

to its low solubility. 

13 C{ 1 H} NMR spectroscopy has been 

applied to the analysis of the microstructure of poly(phenylacetylene)s. 

106–108 However, the assignment of the backbone 

signals in the 13 C{ 1 H} NMR spectra of the prepared iridiumcontaining 

polymers was not possible due to overlapping 

with the resonances of the 2-phenylpyridine or 1-phenylisoquinoline 

moieties. In addition, an analysis of the microstructure 

of the copolymers using the 13 C{ 1 H} NMR spectra was 

hampered by the presence of different types of signals corresponding 

to the different monomer sequences along the 

backbone, which caused a broadening of the signals. 

The TGA traces of the prepared polymers showed that they 

start to appreciably lose weight at T > 300 C. However, a 

complete assessment of the thermal stability of the polymers 

would require spectroscopic and/or GPC measurements on 

thermally treated samples to rule out thermal processes that 

do not produce volatile compounds, that is, intramolecular 

cyclization of the polymer backbone. This process has been 

reported to occur on heating bulk poly(phenylacetylene) at T 

> 100 C, and gives rise to the formation of cyclohexadiene 

sequences along the backbone of the polymer. 101,103,104,109,110 

We could not observe obvious glass transitions from the DSC 

traces, which might be attributed to the rigidity of both the 

backbone and side chain of the polymers. 

Electrochemistry 

The oxidation region of the cyclic voltammograms performed 

to the polymers PIr piq PA and PIr piq CzPA1–5 show two main 

oxidation processes with maximum current around 1.30 V 

and 1.90–2.2 V, respectively (Fig. 2). The decrease of the 

current corresponding to the process centered at 1.30 V 

with decreasing content of Ir-complex in the copolymer suggests 

that this maximum corresponds to the oxidation of the 

Ir complexes attached to the main chain. To confirm this, the 

voltammogram of the pure model complex Ir piq Ph was 

recorded, showing an oxidation maxima at 1.20 V, and the 

reduction process at 0.99 V, with E 1/2 ¼ 1.01 V. In addition, 

an increase of the E ONSET (Ox) values (Table 2) as the Ircomplex 

content diminishes was observed, except for 

PIr piq CzPA2. Using the E ONSET (Ox) values, the HOMO energies 



TABLE 1 Composition, GPC and TGA Data of the New Polymers 

Comonomer Ratio (CzPA mol %) 

Entry 

Polymer 

In the Feed 

Composition 

In the 

Copolymer a 

M n PDI DT 5% b ( C) 

1 PIr ppy PA 0 0 13,300 1.3 394 

2 PIr ppy CzPA1 17 5 14,000 1.2 419 

3 PIr ppy CzPA2 84 82 31,000 1.3 368 

4 PIr ppy CzPA3 91 90 26,600 1.3 373 

5 PIr ppy CzPA4 95 95 29,600 1.3 374 

6 PIr piq PA 0 0 17,300 1.2 387 

7 PIr piq CzPA1 17 9 10,600 1.6 355 

8 PIr piq CzPA2 50 32 12,900 1.2 343 

9 PIr piq CzPA3 84 82 16,900 1.3 358 

10 PIr piq CzPA4 91 91 20,700 1.3 341 

11 PIr piq CzPA5 95 95 24,000 1.5 339 

12 PCzArPA1 50 55 34,600 1.4 398 

13 PCzArPA2 17 29 32,800 1.5 342 

14 PCzPA 100 100 8,400 c 1.1 419 

a Estimated from the C, H, N analysis. 

b DT 5% is the 5% weight-reduction temperature. 

c This value corresponds to the fraction soluble in CHCl 3 . 

for both series of copolymers and model complex (Table 2) 

were estimated. The LUMO energies were estimated using 

two different methods: a) from the HOMO energies and the 

optical gap values obtained from the absorption spectra 111 

and b) from E ONSET (Red) observed on the reduction cyclic 

voltammograms. Similar values were obtained from the two 

methodologies, except in the case of PCzArPA1 (Table 2). 

Photophysical Properties of the Polymers 

The absorption spectra of the organometallic homopolymers 

PIr ppy PA and PIr piq PA (Table 3 and Fig. 3) show intense 

bands in the UV region, which are assigned to aromatic 

p p* transitions of the 2-phenylpyridine and 1-phenylisoquinoline 

ligands, together with weaker lower energy 

absorptions in the visible region (ca. 380–550 nm), which 

are ascribed to 1 MLCT and 3 MLCT transitions of the pendant 

iridium complexes and p p* transitions of the conjugated 

backbone of the polymers. The absorption spectra of copolymers 

with high content of iridium complex PIr ppy CzPA1 and 

PIr piq CzPA1 are similar to those of homopolymers PIr ppy PA 

and PIr piq PA, respectively (Fig. 3). However, on increasing 

the carbazole content of the copolymers, the intense carbazole 

absorption bands increase and the spectra become similar 

to those of the organic polymers PCzArPA1, PCzArPA2 

and PCzPA, except for the presence of a long wavelength 

edge (k > 500 nm), which is due to absorption of the Ir 

chromophores. Polymers containing the Ir piq C 6 H 4 chromophore 

present a longer cut-off wavelength than polymers 

containing the Ir ppy C 6 H 4 chromophore due to the lower 

energy MLCT states of Ir piq C 6 H 4 . The organic polymers show 

strong p p* absorptions in the UV region and a broad band 

in the visible region which was assigned to p p* transitions 

of the conjugated backbone. 

Polymer PIr ppy PA and copolymer PIr ppy CzPA1, which contain 

a 100% and a 95% of Ir monomer, respectively, are 

very weakly emissive in solution at room temperature (Fig. 4 

SCHEME 3 Synthesis of complex Ir piq Ph. 


ARTICLE 

denoted as [Ir(ppy) 2 (acac)]; acac ¼ acetylacetonate) is 

strongly emissive in solution at room temperature, indicating 

that the weakness of the emission in the former complex is 

related to the presence of the phenyl substituent. 112 Theoretical 

studies suggest that the different nature of the LUMO in 

both complexes could be responsible of their different emissive 

behavior, because in Ir ppy –Me the LUMO is mainly 

located in the ppy ligands while in Ir ppy –C 6 H 5 it is mainly 

located in the benzoylacetonate ligand. 112,113 

In contrast to the weak phosphorescence of the Ir ppy -substituted 

polymers, polymers containing the Ir piq group are 

phosphorescent at room temperature in solution (Fig. 5), 

with emission maxima around 620 nm and lifetimes in the 

range 0.35–0.54 ls. These bands are assigned to Ir piq - 

centered, 3 MLCT emissions, being their k max values (Table 3) 

very close to that of model complex Ir piq Ph (619 nm). While 

PIr piq PA and PIr piq CzPA1 display only the 620 nm emission, 

the copolymers with higher carbazole content PIr piq CzPA2– 

5 display also emissions in the range 431–454 nm, being the 

latter dominant for the copolymers with highest carbazole 

content PIr piq CzPA3–5. These shorter-wavelength emissions 

FIGURE 1 Comparison of the IR spectra (region from 1180 to 

1650 cm –1 ) of monomer Ir piq PA and polymers containing different 

amounts of Ir piq PA and CzPA. Representative bands of the 

polymer substituents are marked with dashed (Ir piq ) or gray 

(Cz) rectangles. 

and Table 3). In contrast, copolymers PIr ppy CzPA2–4, which 

contain 82–95% of carbazole monomer, display a stronger 

emission band around 420 nm, which is assigned to carbazole-centered 

transitions. In agreement with this assignment, 

the organic polymers PCzArPA1, PCzArPA2 and PCzPA 

exhibit similar emissions (Fig. 4 and Table 3). At 77 K, polymers 

containing the Ir ppy C 6 H 4 group displayed weak emissions 

around 520 nm (Table 3), which were assigned to 

Ir ppy C 6 H 4 -centered 3 MLCT emissions. 112 

The absence of Ir-centered phosphorescence at room temperature 

is attributed to the weak emissive character of 

the Ir ppy –C 6 H 4 moiety, since previous studies have shown 

that the related complex Ir ppy –C 6 H 5 (also denoted as [Ir 

(ppy) 2 (bza)]; bza ¼ benzoylacetonate) is weakly emissive in 

solution. In contrast, the homologous complex Ir ppy –Me (also 

FIGURE 2 Cyclic voltammograms obtained from films of complex 

Ir piq Ph, organometallic polymers containing the Ir piq group 

and organic polymer PCzArPA1. 



TABLE 2 Electrochemical Data and HOMO and LUMO Energies of Complex Ir piq Ph, Polymers Containing 

the Ir piq Group and Copolymer PCzArPA1 

Compound 

E ONSET 

(Ox) a (V) 

HOMO b 

(eV) 

DE c 

(eV) 

LUMO 

(eV) 

E ONSET 

(Red) a (V) 

LUMO d 

(eV) 

Ir piq Ph 0.90 5.13 2.1 3.03 1.13 3.10 

PIr piq PA 0.75 4.99 2.1 2.89 1.24 2.99 

PIr piq CzPA1 0.81 5.04 2.1 2.94 1.30 2.93 

PIr piq CzPA2 0.77 5.00 2.1 2.90 1.27 2.96 

PIr piq CzPA3 0.84 5.07 2.1 2.97 1.27 2.96 

PIr piq CzPA4 0.94 5.17 2.1 3.07 1.30 2.93 

PIr piq CzPA5 0.96 5.19 2.1 3.09 1.21 3.02 

PCzArPA1 1.34 5.57 2.5 3.07 1.61 2.62 

a Measured by CV vs. Ag þ /Ag in MeCN using a film of the polymer deposited 

on a Pt electrode; E 1/2 (Ox, Ferrocene) ¼ 0.567 V. 

d Value obtained from E ONSET (Red). 

b Calculated using E HOMO ¼ –(E ONSET (Ox) 0.567 þ 4.8) eV. c Optical gap calculated from the absorption spectrum onset. 

45 

are assigned to carbazole-centered transitions because they 

are present when the carbazole monomer content is high 

and their k max values are similar to that of PCzArPA1, 

PCzArPA2, andPCzPA (Fig. 4). The intensity of the phosphorescence 

in PIr piq CzPA1 and PIr piq CzPA2 is stronger than 

that of PIr piq PA, at similar repeating unit concentration, 

which indicates that the organic monomer might act as 

spacer to hinder the quenching effect caused by the interaction 

among the Ir piq C 6 H 4 pendant groups. The weakening of 

the emission from Ir(III) complexes at higher organic monomer 

content is attributed to the lower content of Ir piq C 6 H 4 

phosphor. 

The phosphorescence of polymers containing the Ir piq C 6 H 4 

group and complex Ir piq Ph could be explained by considering 

that owing to the higher degree of conjugation of the piq 

ligand respect to the ppy ligand, the p*(piq) orbital is lower 

in energy than the empty p* orbitals of the bza ligand (k max 

is ca. 100 nm longer for the polymers containing the Ir piq 

TABLE 3 Photophysical Data of the Polymers and Complex Ir piq Ph 

Compound k abs /nm a (293 K) 

(77 K) 

k em /nm (s P /ls) b 

CH 2 Cl 2 

Solution 

Butyronitrile 

Glass 

Film 

(293 K) 

PIr ppy PA 264, 341, 403, 453, 489 406 392, 486, 517 

PIr ppy CzPA1 263, 342, 404, 454, 489 398 395, 485, 518 

PIr ppy CzPA2 240, 294, 329, 343, 372, 455 424 414, 486, 518 

PIr ppy CzPA3 239, 294, 329, 343, 371, 455 419 409, 484, 517 

PIr ppy CzPA4 240, 294, 329, 342, 371, 455 426 406, 484, 517 

Ir piq Ph 231, 293, 341, 355, 380, 477, 540, 596 619, 655 632 c /QY ¼ 0.93 

PIr piq PA 231, 297, 341, 358, 389, 475, 552, 593 618 (0.35), 655 631, 657 

PIr piq CzPA1 231, 295, 342, 359, 387, 475, 552, 592 618 (0.37), 655 629, 656 

PIr piq CzPA2 232, 295, 328, 342, 359, 386, 475, 552, 592 454, 618 (0.38), 655 629, 657, 609 c /QY ¼ 0.43 

PIr piq CzPA3 238, 294, 330, 343, 362, 384, 475 437, 618 (0.47), 655 623, 655, 609 c /QY ¼ 0.30 

PIr piq CzPA4 238, 294, 330, 343, 360, 385, 475 431, 616 (0.44), 655 618, 657 

PIr piq CzPA5 239, 294, 329, 343, 475 441, 616 (0.54), 655 617, 655 

PCzArPA1 240, 294, 330, 343, 430 417 401 

PCzArPA2 240, 294, 331, 343, 425 415 390 

PCzPA d 239, 294, 328, 342 421 409 

a Measured at 293 K in CH 2 Cl 2 . 

b k exc was in the range 340–380 nm. 

c k exc ¼ 296 nm. 

d Partially soluble. 


ARTICLE 

phosphor). In consequence, the LUMO of the Ir piq C 6 H 4 group 

is located mainly on the piq ligand and the long-wavelength 

emissions observed can be assigned to transitions from 

3 MLCT states involving orbitals located on the piq ligand. 

The room temperature photoluminescence spectra of spincoated 

films of polymers PIr piq PA and PIr piq CzPA1–5 

(Fig. 5) displayed maxima in the range 617–631 nm, which 

were assigned to p*(piq) 3 MLCT emissions. In addition, a 

shoulder around 550 nm, observed in copolymers with high 

carbazole monomer content, was assigned to the formation 

of carbazole excimers. No carbazole fluorescence around 

420 nm was observed, even for copolymers with a high 

carbazole content, which indicates that there is an effective 

energy transfer process from the carbazole-centered excited 

FIGURE 3 Absorption spectra (CH 2 Cl 2 ) of the poly(phenylacetylene)s 

containing Ir ppy (top), Ir piq (middle) and Cz (bottom) 

substituents. 

FIGURE 4 Photoluminescence spectra (CH 2 Cl 2 , 298 K) of the 

organometallic polymers containing the Ir ppy group (top) and 

the organic polymers (bottom) 



FIGURE 6 Electroluminescence spectra for the OLED devices 

using as the emitting material: PIr piq CzPA2 (red up-triangles), 

PIr piq CzPA3 (blue, circles), PVK:PBD:Ir piq Ph (green, squares). 

[Color figure can be viewed in the online issue, which is available 

at www.interscience.wiley.com.] 

indium tin oxide (ITO) coated patterned substrate. Previously, 

a 100 nm thick poly(3,4-ethylenedioxythiophene): 

polystyrenesulfonate (PEDOT:PSS) (obtained from HC-Starck) 

was deposited to enhance the hole injection and the device 

stability. A hole and exciton blocking layer (30 nm) consisting 

of 1,3,5-tris(2-N-phenylbenzimidazolyl) benzene (TPBI) 

was deposited via thermal vacuum deposition. Finally, the 

organic layers were covered by a thin (5 nm) layer of barium 

protected by a 80 nm layer of silver that serves as the cathode 

and were deposited via thermal vacuum deposition. 

To analyze the phosphorescent emitter in an OLED configuration, 

model complex Ir piq Ph was dispersed in an 

FIGURE 5 Photoluminescence spectra (298 K) of the organometallic 

polymers containing the Ir piq group measured in 

CH 2 Cl 2 solution (top) or spin-coated films (bottom). [Color 

figure can be viewed in the online issue, which is available at 

www.interscience.wiley.com.] 

states to the Ir piq -centered emissive states in the film. The 

good overlap between the emission spectrum of the carbazole-containing 

poly(phenylacetylene)s and the absorption 

spectrum of Ir piq PA would allow for efficient Förster energy 

transfer from the carbazole to the complexes. 114 This might 

provide an outlet for phosphorescent emitters with selfbearing 

host. 

Electroluminescence 

Simple OLEDs were fabricated utilizing some examples of 

the prepared polymers as light emitting layers (50 nm) by 

spin-coating a toluene solution containing them on an 

FIGURE 7 Current density (solid symbols) and luminance (lines 

plus open symbols) for ITO/PEDOT:PSS/LEP/TPBI/Ba/Ag OLED 

devices containing the polymers; PIr piq CzPA2 (red up-triangles), 

PIr piq CzPA3 (blue, circles), PVK:PBD:Ir piq Ph (green, squares). 

[Color figure can be viewed in the online issue, which is available 

at www.interscience.wiley.com.] 


ARTICLE 

TABLE 4 Electroluminescent Performance of the Devices 

Prepared 

Material 

emissive layer consisting of the hole transporting polymer 

poly(N-vinylcarbazole) (PVK) and the electron transporting 

molecule 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4- 

oxadiazole (PBD). The ratio of the components used was 

PVK:PBD:Ir piq Ph (60:30:10) by weight. 

The electroluminescence spectra of the OLEDs prepared 

using polymers, PIr piq CzPA2 and PIr piq CzPA3 and compound 

Ir piq Ph are depicted in Figure 6. They coincide and 

have a maximum around 620 nm, in line with what is 

observed from photoluminescence of the materials in solution. 

Although the spectra are depicted in arbitrary units, the 

noise level is larger for the polymers due to a lower intensity 

of the emission. When analyzing the current density and 

luminance versus voltage curves (Fig. 7) it is evident that 

these materials yield lower luminance values than the emitting 

blend containing the iridium complex. As a result of the 

lower luminance, also the efficacy is rather low (


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