Synthesis, characterization and electroluminescence properties of new iridium complexes based on cyclic phenylvinylpyridine derivatives: Tuning of emission colour and efficiency by structural control

Shin Ya Takizawa, Yuka Sasaki, Md. Akhtaruzzaman, Hidenori Echizen, Jun Ichi Nishida, Takeshi Iwata, Shizuo Tokito, Yoshiro Yamashita

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

A series of phosphorescent cyclometalated iridium(iii) complexes 4-6 with new ligands of bicyclic phenylvinylpyridines have been synthesized and systematically examined for their photophysical, electrochemical and electroluminescence (EL) properties. All of the bis- and tris-cyclometalated complexes could be characterized by 1H-NMR, elemental analysis and X-ray crystal structure analysis. The phosphorescence colour of the complexes in solution, the solid state and polymer film is unusually changed depending on the structure of the ligand. EL devices using the complexes exhibited external quantum efficiencies (EQE) of 1.2-8.1% at 100 cd m-2, and EL colour tuning in the range of 571-635 nm was achieved analogous to PL properties of the phosphors. X-Ray analyses of complexes 4a-c demonstrated that the degree of steric hindrance increases with an increase of the cycloalkane ring size, leading to hypsochromic shifts of emission by the distortion of the phenyl groups. X-Ray analyses also suggested that long iridium-carbon bonds are unfavorable for efficient electroluminescence. In addition, we have found a unique and important aspect for the study of EL devices: the EL devices based on complexes 4c, 6a show moderate EL efficiencies (EQE = 4.0 and 6.1%) although these complexes have no emission in solution at room temperature, indicating that the PL properties of the complexes in solution are not directly related to the EL efficiencies.

Original languageEnglish
Pages (from-to)841-849
Number of pages9
JournalJournal of Materials Chemistry
Volume17
Issue number9
DOIs
Publication statusPublished - 2007
Externally publishedYes

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Iridium
Electroluminescence
iridium
electroluminescence
Tuning
tuning
Color
Derivatives
color
synthesis
Quantum efficiency
X rays
quantum efficiency
Cycloparaffins
Ligands
Phosphorescence
ligands
x rays
phosphorescence
Polymer films

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Materials Science(all)

Cite this

Synthesis, characterization and electroluminescence properties of new iridium complexes based on cyclic phenylvinylpyridine derivatives : Tuning of emission colour and efficiency by structural control. / Takizawa, Shin Ya; Sasaki, Yuka; Akhtaruzzaman, Md.; Echizen, Hidenori; Nishida, Jun Ichi; Iwata, Takeshi; Tokito, Shizuo; Yamashita, Yoshiro.

In: Journal of Materials Chemistry, Vol. 17, No. 9, 2007, p. 841-849.

Research output: Contribution to journalArticle

Takizawa, Shin Ya ; Sasaki, Yuka ; Akhtaruzzaman, Md. ; Echizen, Hidenori ; Nishida, Jun Ichi ; Iwata, Takeshi ; Tokito, Shizuo ; Yamashita, Yoshiro. / Synthesis, characterization and electroluminescence properties of new iridium complexes based on cyclic phenylvinylpyridine derivatives : Tuning of emission colour and efficiency by structural control. In: Journal of Materials Chemistry. 2007 ; Vol. 17, No. 9. pp. 841-849.
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