含苯基-咪唑配位基及吡唑-吡啶輔助配位基銥金屬錯合物之光物理性質研究

我們研究一系列含碳烯配位基及新型N^N輔助配位基銥金屬錯合物之光物理性質與激發態放光機構。藍色錯合物分別為bis(1-(4-fluorophenyl)-3-methylimidazolin-2-ylidene-C,C2’)(2-(pyrazol-5-yl)pyridine) iridium(III), [Ir(fpmi)2(pypz)], B1, bis(1-(4-fluorophenyl)-3-methyl imidazolin-2-ylidene-C,C2’)(4-methyl-2-(pyrazol-5-yl)pyridine) iridium(III), [Ir(fpmi)2(mpypz)], B2, bis(1-(4-fluorophenyl)-3-methylimidazolin-2-ylidene- C,C2’)(3,5-dimethyl-2-(pyrazol-5-yl) pyridine)iridium(III), [Ir(fpmi)2(dmpypz)], B3，綠色錯合物為bis(1-(1-(4-tolyl)-3-methyl-imidazolin2-ylidene-C,C2’) (2-(pyridine-2-yl)benzo[d]imidazole) , [Ir(mpmi)2(pybi)], G。以266 nm光源激發下，錯合物被激發到1+ 1MLCT (fpmi)能態。從奈秒到微秒的測量結果，我們得到這些錯合物的輻射衰減常數大約為1.5×105~5.2×104 s-1，B1與B3主要放光能階為T1/T2，生命期分別為928、2331 ns，B2主要放光能階為T3，生命期為294 ns，G主要放光能階為T2/T3，生命期為8264 ns。從皮秒的測量結果我們觀察到錯合物B3與G的上升時間分別約為34 ps與20 ps，快於B1與B2的上升時間90 ps與 76 ps。上升時間以解析度更佳之瞬態吸收光譜再次確認並得到相似的結果。此快速的上升時間代表能量從碳烯配位基單重激發態迅速轉換到輔助配位基之三重激發態，錯合物B3與G有較快的上升時間可以避免掉一些淬熄及非放光過程，因此會有較好的外部量子效率。我們並利用密度泛函理論(DFT)計算此系列錯合物之電子結構輔助探討實驗結果。

關鍵字

銥金屬碳烯錯合物；有機發光二極體

並列摘要

We investigate the emission property and relaxation mechanism of excited states of Iridium biscarbene complexes with varied ancillary N^N ligands; they are blue complexes bis(1-(4-fluorophenyl)-3-methylimidazolin-2-ylidene-C,C2’)(2-(pyrazol -5-yl)pyridine)iridium(III), Ir(fpmi)2(pypz) B1, bis(1-(4-fluorophenyl) -3-methylimidazolin-2-ylidene-C,C2’)(4-methyl-2-(pyrazol-5-yl)pyridine)iridium(III), Ir(fpmi)2(mpypz) B2, bis(1-(4-fluorophenyl)-3-methylimidazolin-2-ylidene-C,C2’) (3,5-dimethyl-2-(pyrazol-5-yl) pyridine)iridium(III), Ir(fpmi)2(dmpypz) B3, and green complex bis(1-(1-(4-tolyl)-3-methyl-imidazolin2-ylidene-C,C2’)(2-(pyridine-2-yl) benzo[d]imidazole), Ir(mpmi)2(pybi) G. At 266-nm excitation the ancillary + 1MLCT (fpmi) states are accessed. According to the results of nano-microsecond measurements and quantum yields at long wavelengths, we obtained the radiative rate constants kr of these complexes to be 0.5-1.5105 s-1. According to the values of kr, long lifetimes, and the experimental data we then assigned the emitting states to be triplet interligand 3(ancillary)* mixed extensively with triplet metal-to-ligand charge transfer (3MLCT). From picosecond lifetime measurements, we observe that B3 and G have a rise time constant ~34 ps, ~20 ps, faster than the B1 and B2 ~90 ps, ~76 ps, respectively in the emission curves. These fast rises are also confirmed with the results of transient absorption measurements. The fast rise corresponds to rapid conversion from singlet manifold centered at biscarbene ligand to the triplet states centered at the ancillary ligand. More rapid conversion rates in B3 and G may partially explain excellence external quantum efficiency that can avoid quenching and annihilation processes. We employed the quantum chemical calculations-density functional theory (DFT) to obtain their electronic structures and to aid in interpreting the experimental data.

並列關鍵字

Ir(fpmi)2(dmpypz) ； Ir(mpmi)2(pybi) ； iridium carbene complexes ； OLED ； interligand energy transfer

參考文獻

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含苯基-咪唑配位基及吡唑-吡啶輔助配位基銥金屬錯合物之光物理性質研究

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