Iridium Complex Containing Phosphite and Bipyridine Carboxylate Ligands and Their Aggregation Induced Enhanced Emission and Electroluminescent Properties†

doi:10.7503/cjcu20180039

Abstract

Abstract:

A novel iridium(Ⅲ) complex [Ir(tpitH₂)(dcbde)Cl, tpitH₂=triphenylphosphite, dcbde=2,2'-bipyridyl-4,4'-dicarboxylic acid diethyl ester] was synthesized in a high yield via a one-pot reaction. Ir(tht)₃Cl₃, tpitH₂ and dcbde were used as iridium regent, dicyclometalated tridentate ligand, and neutral ligand, respectively. This new iridium(Ⅲ) complex was characterized by the nuclear magnetic resonance, high resolution mass spectroscopies and X-ray structural analysis. The distorted octahedrally coordinated iridium(Ⅲ) center was ligated by neutral dcbde chromophore, and combinated with a facially coordinated dicyclometalated phosphite chelate and a monodentate chloride ancillary. The film was blended with this complex and polymethyl methacrylate(PMMA). The film showed a strong yellow phosphorescent emission at 580 nm. The film with high quantum yield of 0.294 was observed emission lifetime of ca. 1.08 μs. The emission intensity of the complex in H₂O(70%, volume fraction)/tetrahydrofuran(THF) solution was about 17 times higher than in pure THF solvent. This complex had a strong aggregation induced emission enhancement(AIEE) property. The phosphorescent organic light-emitting diode(PhOLED) device architecture comprised a simple single emissive layer, which showed good luminescent efficiency(8.9%, 9.7 cd/A, 5.2 lm/W). The device showed a maximum luminance of 3791 cd/m² at 12.7 V. The results showed that the strong field ligand tpit could improve the luminous efficiency of bipyridine carboxylate based iridium complexes and extend its scope of application.

Key words: Cyclometalated iridium(Ⅲ) complex;, Triphenylphosphite, 2,2'-Bipyridyl-4,4'-dicarboxylic acid diethyl ester, Aggregation induced enhanced emission, Organic electroluminescence

CLC Number:

O614.8

TrendMD:

WEI Liangchen, HU Weikang, ZHOU Shixiong, SHU Jun, ZHOU Huidong, HU Xucheng, JIANG Yi, TONG Bihai, ZHANG Qianfeng. Iridium Complex Containing Phosphite and Bipyridine Carboxylate Ligands and Their Aggregation Induced Enhanced Emission and Electroluminescent Properties^†[J]. Chem. J. Chinese Universities, 2018, 39(7): 1371.

Figures/Tables 6

Scheme 1 Synthetic route of complex 1

Fig.1 Perspective view of the complex 1 with selected displacement ellipsoids drawn at the 5% probability level^Hydrogen atoms were omitted for clarity.^CCDC: 1585397.

Table 1 Crystal data of the complex*

Compound	Iridium complex
Empirical formula	C₃₄H₂₉ClIrN₂O₇P
Formula weight	836.23
T/K	296.15
λ/nm	0.071073
Crystal system	Triclinic
Space group	P $1 ˉ$
a/nm	1.09916(15)
b/nm	1.14270(15)
c/nm	1.40209(18)
α/(°)	78.060(2)
β/(°)	83.685(2)
γ/(°)	81.614(2)
V/nm³	1.6987(4)
Z	2
D_c/(g·cm^-3)	1.635
Absorption coefficient/mm^-1	4.105
F(000)	824
θ range/(°)	2.456—27.503
Index ranges	-14≤h≤12, -14≤k≤14, -18≤l≤17
Reflections collected/unique	10461/7447[R_int=0.0239]
Absorption correction	Semi-empirical from equivalents
Data/restraints/parameters	7447/45/437
GOF on F²	1.018
Final R indices[I>2σ(I)]	R₁=0.0387, wR₂=0.1018
R indices(all data)	R₁=0.0527, wR₂=0.1105

Table 1 Crystal data of the complex*

Compound	Iridium complex
Empirical formula	C₃₄H₂₉ClIrN₂O₇P
Formula weight	836.23
T/K	296.15
λ/nm	0.071073
Crystal system	Triclinic
Space group	P $1 ˉ$
a/nm	1.09916(15)
b/nm	1.14270(15)
c/nm	1.40209(18)
α/(°)	78.060(2)
β/(°)	83.685(2)
γ/(°)	81.614(2)
V/nm³	1.6987(4)
Z	2
D_c/(g·cm^-3)	1.635
Absorption coefficient/mm^-1	4.105
F(000)	824
θ range/(°)	2.456—27.503
Index ranges	-14≤h≤12, -14≤k≤14, -18≤l≤17
Reflections collected/unique	10461/7447[R_int=0.0239]
Absorption correction	Semi-empirical from equivalents
Data/restraints/parameters	7447/45/437
GOF on F²	1.018
Final R indices[I>2σ(I)]	R₁=0.0387, wR₂=0.1018
R indices(all data)	R₁=0.0527, wR₂=0.1105

Fig.2 UV-Vis absorption spectrum of iridium complex in CH2Cl2(a) and PL spectra in CH2Cl2(b) and PMMA(c)^PMMA with mass fraction of 1% picture under the ultraviolet lamp.

Fig.3 Emission spectra of iridium complex in water/THF mixtures with different water fractions

Fig.4 Electroluminescent properties of complex 1^(A) Electroluminescence spectrum; (B) current density-voltage-luminance(J-V-L) characteristics;^(C) power efficiencies/luminance efficiencies vs. luminance; (D) external quantum efficiency vs. luminance.

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