TY - JOUR
T1 - Synthesis, characterization and electroluminescence properties of new iridium complexes based on cyclic phenylvinylpyridine derivatives
T2 - Tuning of emission colour and efficiency by structural control
AU - Takizawa, Shin Ya
AU - Sasaki, Yuka
AU - Akhtaruzzaman, Md
AU - Echizen, Hidenori
AU - Nishida, Jun Ichi
AU - Iwata, Takeshi
AU - Tokito, Shizuo
AU - Yamashita, Yoshiro
PY - 2007/2/28
Y1 - 2007/2/28
N2 - 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.
AB - 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.
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U2 - 10.1039/b612633b
DO - 10.1039/b612633b
M3 - Article
AN - SCOPUS:33847235700
VL - 17
SP - 841
EP - 849
JO - Journal of Materials Chemistry
JF - Journal of Materials Chemistry
SN - 0959-9428
IS - 9
ER -