title: Synthesis, characterization, and photophysical properties of Os(II) diimine complexes [Os(N(wedge)N)(CO)(2)I(2)] (N(wedge)N = bipyridine, phenanthroline, and pyridyl benzoxazole).
abstract: A new series of Os(II) diimine complexes with the general formula [Os(N(wedge)N)(CO)(2)I(2)], N(wedge)N = 2,2'-bipyridine (bpy) (1), 4,4'-di-tert-butyl-2,2'-bipyridine (dbubpy) (2), 4,7-diphenyl-1,10-phenanthroline (dpphen) (3), 2-(2'-pyridyl)benzoxazole (pboz) (4), and 5-tert-butyl-2-(2'-pyridyl)benzoxazole (bupboz) (5), were synthesized and characterized by spectroscopic methods and by a single-crystal X-ray diffraction study on the dpphen complex 3. The corresponding photophysical properties were studied using UV-vis and emission spectrometry. The resulting phosphorescence features both in solution and as a solid film, in combination with the MO calculation, lead us to conclude that the emissions originate from mixed halide-to-ligand (XLCT approximately 70%) and metal-to-ligand (MLCT approximately 30%) transitions instead of the typical MLCT transition. Using complexes 4 and 5 as the dopant emitters, we evaluated their potential to serve as a phosphor for organic light emitting diodes by examining their electroluminescent performances. Reddish orange electroluminescence centered around 600 nm was observed for organic light emitting diodes (OLEDs) fabricated using complex 5 as the emitter; the device efficiency was shown to be as high as 2.8% (and 5.0 cd/A or 2.7 lm/W), and the peak luminance was shown to be 5600 cd/m(2) at a driving voltage of approximately 15 V.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Yao-Lun
authors.initials: YL
authors.lastname: Chen
authors.forename: Shih-Wen
authors.initials: SW
authors.lastname: Lee
authors.forename: Yun
authors.initials: Y
authors.lastname: Chi
authors.forename: Kuo-Chu
authors.initials: KC
authors.lastname: Hwang
authors.forename: Sujit Baran
authors.initials: SB
authors.lastname: Kumar
authors.forename: Ya-Hui
authors.initials: YH
authors.lastname: Hu
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Cheng
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
authors.forename: Shie-Ming
authors.initials: SM
authors.lastname: Peng
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Shi-Jay
authors.initials: SJ
authors.lastname: Yeh
authors.forename: Chin-Ti
authors.initials: CT
authors.lastname: Chen