Strategic design and synthesis of osmium(II) complexes bearing a single pyridyl azolate π-chromophore: Achieving high-efficiency blue phosphorescence by localized excitation

Yi Ming Cheng, Elise Y. Li, Gene Hsiang Lee, Pi Tai Chou, Sue Yi Lin, Ching Fong Shu, Kwun Chi Hwang, Yao Lun Chen, Yi Hwa Song, Yun Chi

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Abstract

We present the strategic design and synthesis of Os(II) complexes bearing a single pyridyl azolate π-chromophore with an aim to attain high efficiency blue phosphorescence by way of localized transition. It turns out that our proposal of localized excitation seems to work well upon anchoring a single π-chromophore on the Os(II) complexes such that the control of MLCT versus ππ* (or even LLCT) transitions is more straightforward. Among the titled complexes, [Os(CO)3(tfa)(fppz)] (1) and [Os(CO) 3(tfa)(fbtz)] (5) (tfa = trifluoroacetate, (fppz)H = 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole, and (fbtz)H = 3-(trifluoromethyl)-5- (4-tert-butyl-2-pyridyl)-1,2,4-triazole) give the anticipated blue phosphorescence with efficiencies of 0.26 (λmax = 460 nm) and 0.27 (λmax = 450 nm), respectively. For their halide analogues [Os(CO)3(X)(fppz)] (2, X = Cl; 3, X = Br; 4, X = I) and phosphine-substituted isomeric derivatives [Os(tfa)(fppz)(PPh 2Me)2(CO)] (6-8), the localization of the excitation energy seems to populate at certain vibrational modes with weak bonding strength and hence an associated shallow potential energy surface to induce a facile radiationless transition. Furthermore, their ancillary ligands play an important role in fine-tuning not only the energy gap but also the emission intensity, i.e., in manifesting the radiationless transition pathways. Our results clearly show that there is always a tradeoff upon varying the parameters in an aim to optimize the hue and efficiency of phosphorescence toward blue.

Original languageEnglish
Pages (from-to)10276-10286
Number of pages11
JournalInorganic Chemistry
Volume46
Issue number24
DOIs
Publication statusPublished - 2007 Nov 26

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phosphine
Bearings (structural)
Osmium
Trifluoroacetic Acid
Phosphorescence
osmium
Chromophores
phosphorescence
chromophores
Ligands
synthesis
excitation
Potential energy surfaces
Excitation energy
Energy gap
tradeoffs
Tuning
phosphines
Derivatives
halides

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Strategic design and synthesis of osmium(II) complexes bearing a single pyridyl azolate π-chromophore : Achieving high-efficiency blue phosphorescence by localized excitation. / Cheng, Yi Ming; Li, Elise Y.; Lee, Gene Hsiang; Chou, Pi Tai; Lin, Sue Yi; Shu, Ching Fong; Hwang, Kwun Chi; Chen, Yao Lun; Song, Yi Hwa; Chi, Yun.

In: Inorganic Chemistry, Vol. 46, No. 24, 26.11.2007, p. 10276-10286.

Research output: Contribution to journalArticle

Cheng, Yi Ming ; Li, Elise Y. ; Lee, Gene Hsiang ; Chou, Pi Tai ; Lin, Sue Yi ; Shu, Ching Fong ; Hwang, Kwun Chi ; Chen, Yao Lun ; Song, Yi Hwa ; Chi, Yun. / Strategic design and synthesis of osmium(II) complexes bearing a single pyridyl azolate π-chromophore : Achieving high-efficiency blue phosphorescence by localized excitation. In: Inorganic Chemistry. 2007 ; Vol. 46, No. 24. pp. 10276-10286.
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abstract = "We present the strategic design and synthesis of Os(II) complexes bearing a single pyridyl azolate π-chromophore with an aim to attain high efficiency blue phosphorescence by way of localized transition. It turns out that our proposal of localized excitation seems to work well upon anchoring a single π-chromophore on the Os(II) complexes such that the control of MLCT versus ππ* (or even LLCT) transitions is more straightforward. Among the titled complexes, [Os(CO)3(tfa)(fppz)] (1) and [Os(CO) 3(tfa)(fbtz)] (5) (tfa = trifluoroacetate, (fppz)H = 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole, and (fbtz)H = 3-(trifluoromethyl)-5- (4-tert-butyl-2-pyridyl)-1,2,4-triazole) give the anticipated blue phosphorescence with efficiencies of 0.26 (λmax = 460 nm) and 0.27 (λmax = 450 nm), respectively. For their halide analogues [Os(CO)3(X)(fppz)] (2, X = Cl; 3, X = Br; 4, X = I) and phosphine-substituted isomeric derivatives [Os(tfa)(fppz)(PPh 2Me)2(CO)] (6-8), the localization of the excitation energy seems to populate at certain vibrational modes with weak bonding strength and hence an associated shallow potential energy surface to induce a facile radiationless transition. Furthermore, their ancillary ligands play an important role in fine-tuning not only the energy gap but also the emission intensity, i.e., in manifesting the radiationless transition pathways. Our results clearly show that there is always a tradeoff upon varying the parameters in an aim to optimize the hue and efficiency of phosphorescence toward blue.",
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AU - Li, Elise Y.

AU - Lee, Gene Hsiang

AU - Chou, Pi Tai

AU - Lin, Sue Yi

AU - Shu, Ching Fong

AU - Hwang, Kwun Chi

AU - Chen, Yao Lun

AU - Song, Yi Hwa

AU - Chi, Yun

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