Influence of Different Diimine (N鈭?/sup>N) Ligands on the Photophysics and Reverse Saturable Absorption of Heteroleptic Cationic Iridium(III) Complexes Bearing Cyclometalating 2-{3-[7-(Benzothiaz

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• 作者：Rui Liu ; Naveen Dandu ; Jinquan Chen ; Yuhao Li ; Zhongjing Li ; Shan Liu ; Chengzhe Wang ; Svetlana Kilina ; Bern Kohler ; Wenfang Sun
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：October 9, 2014
• 年：2014
• 卷：118
• 期：40
• 页码：23233-23246
• 全文大小：849K
• ISSN：1932-7455

文摘

Four heteroleptic cationic iridium(III) complexes containing cyclometalating 2-{3-[7-(benzothiazol-2-yl)fluoren-2-yl]phenyl}pyridine ligand and different diimine (N^{鈭?/sup>N) ligands (N鈭?/sup>N = 2-(pyridin-2-yl)quinoline (1), 1,10-phenanthroline (2), 2,2鈥?biquinoline (3), and 1,1鈥?biisoquinoline (4)) and a reference complex bearing 2-(pyridin-2-yl)quinoline and 2-phenylpyridine ligands (5) were synthesized and characterized. The influence of the diimine (N鈭?/sup>N) ligand on the photophysics of these complexes has been systematically investigated via spectroscopic methods and by time-dependent density functional theory (TDDFT). All complexes exhibit N鈭?/sup>N or C鈭?/sup>N ligand localized 1蟺,蟺* transitions below 400 nm, and broad and structureless metal-to-ligand and ligand-to-ligand charge transfer (1MLCT/1LLCT) absorption bands between 400 and 450 nm, and weak 3MLCT/3LLCT absorption above 450 nm. Increasing the 蟺-conjugation of the N鈭?/sup>N ligand causes enhanced molar extinction coefficients of the absorption bands and a bathochromic shift of the 3MLCT/3LLCT band. All complexes show orange to red phosphorescence at room temperature, with the emitting state being predominantly assigned to 3MLCT/3LLCT states for 1鈥?b>5, but with some 3蟺,蟺* contributions for 3 and 5. Extending the 蟺-conjugation of the N鈭?/sup>N ligand induces a pronounced red-shift of the emission band and decreases the emission lifetime and quantum yield. Complexes 1鈥?b>5 exhibit relatively strong singlet and triplet transient absorption from 450 to 800 nm, where the reverse saturable absorption (RSA) could occur. Nonlinear transmission experiments at 532 nm using nanosecond laser pulses demonstrate that complexes 1鈥?b>5 are strong reverse saturable absorbers at 532 nm.}