Luminescent Platinum(II) Complexes Containing Isoquinolinyl Indazolate Ligands: Synthetic Reaction Pathway and Photophysical Properties
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- 作者：Sheng-Yuan Chang ; Jakka Kavitha ; Jui-Yi Hung ; Yun Chi ; Yi-Ming Cheng ; Elise Y. Li ; Pi-Tai Chou ; Gene-Hsiang Lee ; Arthur J. Carty
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：August 20, 2007
- 年：2007
- 卷：46
- 期：17
- 页码：7064 - 7074
- 全文大小：350K
- 年卷期：v.46,no.17(August 20, 2007)
- ISSN：1520-510X
文摘
New Pt(II) dichloride complexes [Pt(1-iqdzH)Cl2] (2a) and [Pt(3-iqdzH)Cl2] (2b), in which idqzH = 1- or 3-isoquinolinylindazole, were prepared by treatment of the corresponding indazoles with K2PtCl4 in aqueous HCl solution. Despitetheir nonemissive nature, these complexes could react with excess indazole, sodium picolinate, and 3-trifluoromethyl-5-(2-pyridyl) pyrazole [(fppz)H] to afford the respective a and b series of luminescent complexes [Pt(1-iqdz)(L
X)]and [Pt(3-iqdz)(LX)], where LX = 1-iqdz (1a), 3-iqdz (1b), pic (3a, 3b), and fppz (4a, 4b). Single-crystal X-raydiffraction studies of 1b, 2a, and 3b revealed a planar molecular geometry without notable intermolecular Pt···Ptcontact in the solid crystal, a result of the steric repulsion imposed by the bulky indazole fragments. For coordinationcomplexes 1, 3, and 4, photoluminescence in degassed CH2Cl2 revealed high quantum efficiency and short radiativelifetimes in the range of several microseconds. As supported by the spectral feature, the associated radiationlifetimes, and a computational approach based on time-dependent density function theory (TD-DFT), the origin ofthe emission is attributed to a mixed 3MLCT/3
transition. The TD-DFT approach further confirmed that, exceptfor the series 1 complexes, the HOMO of 3-iqdz complexes 3b and 4b is much less located at the central Pt(II)atom than the HOMO orbitals of the respective 1-iqdz complexes 3a and 4a, leading to a smaller degree of MLCTcontribution. Consequently, there are a blue-shifted emission signal and an inferior emission quantum yield for the3-iqdz derivatives. OLED devices with a multilayer configuration of ITO/NPB/CBP:3a/BCP/Alq3/LiF/Al were fabricatedusing a CBP layer doped with various concentrations of 3a, ranging from 6% to 100%, within the emitting layer.The best device performance was realized using a 6% doping concentration, for which the external quantum yieldof 4.93%, luminous efficiency of 12.19 cd/A, and power efficiency of 6.12 lm W-1 were observed at 20 mA/cm2,while a maximum luminescence as high as 20296 cd/m2 was also realized at 16 V, showing good prospect for thefabrication of Pt(II) based OLEDs.
X)]and [Pt(3-iqdz)(LX)], where LX = 1-iqdz (1a), 3-iqdz (1b), pic (3a, 3b), and fppz (4a, 4b). Single-crystal X-raydiffraction studies of 1b, 2a, and 3b revealed a planar molecular geometry without notable intermolecular Pt···Ptcontact in the solid crystal, a result of the steric repulsion imposed by the bulky indazole fragments. For coordinationcomplexes 1, 3, and 4, photoluminescence in degassed CH2Cl2 revealed high quantum efficiency and short radiativelifetimes in the range of several microseconds. As supported by the spectral feature, the associated radiationlifetimes, and a computational approach based on time-dependent density function theory (TD-DFT), the origin ofthe emission is attributed to a mixed 3MLCT/3 transition. The TD-DFT approach further confirmed that, exceptfor the series 1 complexes, the HOMO of 3-iqdz complexes 3b and 4b is much less located at the central Pt(II)atom than the HOMO orbitals of the respective 1-iqdz complexes 3a and 4a, leading to a smaller degree of MLCTcontribution. Consequently, there are a blue-shifted emission signal and an inferior emission quantum yield for the3-iqdz derivatives. OLED devices with a multilayer configuration of ITO/NPB/CBP:3a/BCP/Alq3/LiF/Al were fabricatedusing a CBP layer doped with various concentrations of 3a, ranging from 6% to 100%, within the emitting layer.The best device performance was realized using a 6% doping concentration, for which the external quantum yieldof 4.93%, luminous efficiency of 12.19 cd/A, and power efficiency of 6.12 lm W-1 were observed at 20 mA/cm2,while a maximum luminescence as high as 20296 cd/m2 was also realized at 16 V, showing good prospect for thefabrication of Pt(II) based OLEDs.