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Paper
Dalton Trans., 2007, 1881 - 1890, DOI: 10.1039/b700998d
Color tuning associated with heteroleptic cyclometalated Ir(III) complexes: influence of the ancillary ligand
Chau-Jiun Chang, Cheng-Han Yang, Kellen Chen, Yun Chi, Ching-Fong Shu, Mei-Lin Ho, Yu-Shan Yeh and Pi-Tai Chou
We report the preparation of a series of new heteroleptic Ir(III) metal complexes chelated by two cyclometalated 1-(2,4-difluorophenyl)pyrazole ligands (dfpz)H and a third ancillary bidentate ligand (L^X). Such an intricate design lies in a core concept that the cyclometalated dfpz ligands always warrant a greater
* gap in these series of iridium complexes. Accordingly, the lowest one-electron excitation would accommodate the * orbital of the ancillary L^X ligands, the functionalization of which is then exploited to fine-tune the phosphorescent emission wavelengths. Amongst the L^X ligands designed, three classes (series 1– 3) can be categorized, and remarkable bathochromic shifts of phosphorescence were observed by (i) replacing the 2-benzoxazol-2-yl substituent ( 1a) with the 2-benzothiazol-2-yl group ( 1b) in the phenolate complexes, (ii) converting the pyridyl group ( 2a) to the pyrazolyl group ( 2b) and even to the isoquinolyl group ( 2c) in the pyrazolate complexes and (iii) extending the -conjugation of the benzimidazolate ligand from 3a to 3b. Single-crystal X-ray diffraction study on complex [(dfpz)Ir(bzpz)] ( 2b) was conducted to confirm their general molecular architectures. Complex 2b was also used as a representative example for fabrication of multilayered, green-emitting phosphorescent OLEDs using the direct thermal evaporation technique.
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