Luminescent platinum(II) complexes containing isoquinolinyl indazolate ligands: Synthetic reaction pathway and photophysical properties

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

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Abstract

New Pt(II) dichloride complexes [Pt(1-iqdzH)Cl2] (2a) and [Pt(3-iqdzH)Cl2] (2b), in which idqzH = 1- or 3-isoquinolinyl indazole, were prepared by treatment of the corresponding indazoles with K 2PtCl4 in aqueous HCl solution. Despite their 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)(L∧X)], where L∧X = 1-iqdz (1a), 3-iqdz (1b), pic (3a, 3b), and fppz (4a, 4b). Single-crystal X-ray diffraction studies of 1b, 2a, and 3b revealed a planar molecular geometry without notable intermolecular Pt⋯Pt contact in the solid crystal, a result of the steric repulsion imposed by the bulky indazole fragments. For coordination complexes 1, 3, and 4, photoluminescence in degassed CH2Cl2 revealed high quantum efficiency and short radiative lifetimes in the range of several microseconds. As supported by the spectral feature, the associated radiation lifetimes, and a computational approach based on time-dependent density function theory (TD-DFT), the origin of the emission is attributed to a mixed 3MLCT/ 3ππ transition. The TD-DFT approach further confirmed that, except for 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 MLCT contribution. Consequently, there are a blue-shifted emission signal and an inferior emission quantum yield for the 3-iqdz derivatives. OLED devices with a multilayer configuration of ITO/NPB/CBP:3a/BCP/Alq3/LiF/Al were fabricated using 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 yield of 4.93%, luminous efficiency of 12.19 cd/A, and power efficiency of 6.12 Im 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 the fabrication of Pt(II) based OLEDs.

Original languageEnglish
Pages (from-to)7064-7074
Number of pages11
JournalInorganic Chemistry
Volume46
Issue number17
DOIs
Publication statusPublished - 2007 Aug 20

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Indazoles
Platinum
platinum
Ligands
ligands
Organic light emitting diodes (OLED)
Quantum yield
Probability density function
dichlorides
power efficiency
radiative lifetime
ITO (semiconductors)
Equipment and Supplies
quantum efficiency
Coordination Complexes
Luminescence
Quantum efficiency
fragments
sodium
X-Ray Diffraction

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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Luminescent platinum(II) complexes containing isoquinolinyl indazolate ligands : Synthetic reaction pathway and photophysical properties. / Chang, Sheng Yuan; Kavitha, Jakka; Hung, Jui Yi; Chi, Yun; Cheng, Yi Ming; Li, Elise Y.; Chou, Pi Tai; Lee, Gene Hsiang; Carty, Arthur J.

In: Inorganic Chemistry, Vol. 46, No. 17, 20.08.2007, p. 7064-7074.

Research output: Contribution to journalArticle

Chang, Sheng Yuan ; Kavitha, Jakka ; Hung, Jui Yi ; Chi, Yun ; Cheng, Yi Ming ; Li, Elise Y. ; Chou, Pi Tai ; Lee, Gene Hsiang ; Carty, Arthur J. / Luminescent platinum(II) complexes containing isoquinolinyl indazolate ligands : Synthetic reaction pathway and photophysical properties. In: Inorganic Chemistry. 2007 ; Vol. 46, No. 17. pp. 7064-7074.
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abstract = "New Pt(II) dichloride complexes [Pt(1-iqdzH)Cl2] (2a) and [Pt(3-iqdzH)Cl2] (2b), in which idqzH = 1- or 3-isoquinolinyl indazole, were prepared by treatment of the corresponding indazoles with K 2PtCl4 in aqueous HCl solution. Despite their 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)(L∧X)], where L∧X = 1-iqdz (1a), 3-iqdz (1b), pic (3a, 3b), and fppz (4a, 4b). Single-crystal X-ray diffraction studies of 1b, 2a, and 3b revealed a planar molecular geometry without notable intermolecular Pt⋯Pt contact in the solid crystal, a result of the steric repulsion imposed by the bulky indazole fragments. For coordination complexes 1, 3, and 4, photoluminescence in degassed CH2Cl2 revealed high quantum efficiency and short radiative lifetimes in the range of several microseconds. As supported by the spectral feature, the associated radiation lifetimes, and a computational approach based on time-dependent density function theory (TD-DFT), the origin of the emission is attributed to a mixed 3MLCT/ 3ππ transition. The TD-DFT approach further confirmed that, except for 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 MLCT contribution. Consequently, there are a blue-shifted emission signal and an inferior emission quantum yield for the 3-iqdz derivatives. OLED devices with a multilayer configuration of ITO/NPB/CBP:3a/BCP/Alq3/LiF/Al were fabricated using 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 yield of 4.93{\%}, luminous efficiency of 12.19 cd/A, and power efficiency of 6.12 Im 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 the fabrication of Pt(II) based OLEDs.",
author = "Chang, {Sheng Yuan} and Jakka Kavitha and Hung, {Jui Yi} and Yun Chi and Cheng, {Yi Ming} and Li, {Elise Y.} and Chou, {Pi Tai} and Lee, {Gene Hsiang} and Carty, {Arthur J.}",
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T1 - Luminescent platinum(II) complexes containing isoquinolinyl indazolate ligands

T2 - Synthetic reaction pathway and photophysical properties

AU - Chang, Sheng Yuan

AU - Kavitha, Jakka

AU - Hung, Jui Yi

AU - Chi, Yun

AU - Cheng, Yi Ming

AU - Li, Elise Y.

AU - Chou, Pi Tai

AU - Lee, Gene Hsiang

AU - Carty, Arthur J.

PY - 2007/8/20

Y1 - 2007/8/20

N2 - New Pt(II) dichloride complexes [Pt(1-iqdzH)Cl2] (2a) and [Pt(3-iqdzH)Cl2] (2b), in which idqzH = 1- or 3-isoquinolinyl indazole, were prepared by treatment of the corresponding indazoles with K 2PtCl4 in aqueous HCl solution. Despite their 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)(L∧X)], where L∧X = 1-iqdz (1a), 3-iqdz (1b), pic (3a, 3b), and fppz (4a, 4b). Single-crystal X-ray diffraction studies of 1b, 2a, and 3b revealed a planar molecular geometry without notable intermolecular Pt⋯Pt contact in the solid crystal, a result of the steric repulsion imposed by the bulky indazole fragments. For coordination complexes 1, 3, and 4, photoluminescence in degassed CH2Cl2 revealed high quantum efficiency and short radiative lifetimes in the range of several microseconds. As supported by the spectral feature, the associated radiation lifetimes, and a computational approach based on time-dependent density function theory (TD-DFT), the origin of the emission is attributed to a mixed 3MLCT/ 3ππ transition. The TD-DFT approach further confirmed that, except for 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 MLCT contribution. Consequently, there are a blue-shifted emission signal and an inferior emission quantum yield for the 3-iqdz derivatives. OLED devices with a multilayer configuration of ITO/NPB/CBP:3a/BCP/Alq3/LiF/Al were fabricated using 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 yield of 4.93%, luminous efficiency of 12.19 cd/A, and power efficiency of 6.12 Im 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 the fabrication of Pt(II) based OLEDs.

AB - New Pt(II) dichloride complexes [Pt(1-iqdzH)Cl2] (2a) and [Pt(3-iqdzH)Cl2] (2b), in which idqzH = 1- or 3-isoquinolinyl indazole, were prepared by treatment of the corresponding indazoles with K 2PtCl4 in aqueous HCl solution. Despite their 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)(L∧X)], where L∧X = 1-iqdz (1a), 3-iqdz (1b), pic (3a, 3b), and fppz (4a, 4b). Single-crystal X-ray diffraction studies of 1b, 2a, and 3b revealed a planar molecular geometry without notable intermolecular Pt⋯Pt contact in the solid crystal, a result of the steric repulsion imposed by the bulky indazole fragments. For coordination complexes 1, 3, and 4, photoluminescence in degassed CH2Cl2 revealed high quantum efficiency and short radiative lifetimes in the range of several microseconds. As supported by the spectral feature, the associated radiation lifetimes, and a computational approach based on time-dependent density function theory (TD-DFT), the origin of the emission is attributed to a mixed 3MLCT/ 3ππ transition. The TD-DFT approach further confirmed that, except for 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 MLCT contribution. Consequently, there are a blue-shifted emission signal and an inferior emission quantum yield for the 3-iqdz derivatives. OLED devices with a multilayer configuration of ITO/NPB/CBP:3a/BCP/Alq3/LiF/Al were fabricated using 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 yield of 4.93%, luminous efficiency of 12.19 cd/A, and power efficiency of 6.12 Im 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 the fabrication of Pt(II) based OLEDs.

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