Metal-Assisted Delayed Fluorescent Pd(II) Complexes and Phosphorescent Pt(II) Complex Based on [1,2,4]Triazolo[4,3-a]pyridine-Containing Ligands: Synthesis, Characterization, Electrochemistry, Photophysical Studies, and Application
Metal-Assisted Delayed Fluorescent Pd(II) Complexes and Phosphorescent Pt(II) Complex Based on [1,2,4]Triazolo[4,3-a]pyridine-Containing Ligands: Synthesis, Characterization, Electrochemistry, Photophysical Studies, and Application
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DOI：
10.1021/acs.inorgchem.9b01617
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发表时间：
2019-11-04
影响因子：
4.6
通讯作者：
She, Yuanbin
中科院分区：
文献类型：
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作者：
Li, Guijie;Chen, Qidong;She, Yuanbin
报道了一系列四齿环金属M(tzpPh-O-chPy-R)及其类似物的合成和光物理表征，其中M为钯或铂，四齿环金属配体含有与氧原子相连的tzpPh(3-苯基-[1，2，4]三唑并[4，3-a]吡啶)和zzPy(咔唑基吡啶)。配体上的西格玛给电子基R的变化对配合物的光物理性质有显著的影响。以强吸电子的TZP部分为受体，咔唑部分为给体，制备了一系列Pd(II)金属辅助延迟荧光(MADF)材料。电化学分析表明，不可逆还原过程发生在TZP环上，不可逆氧化过程主要发生在金属苯环上。这与密度泛函理论计算得到的HOMO和LUMO分布相一致，这也表明铂(II)络合物比Pd(II)络合物具有更多的金属轨道特征。本文报道的大多数Pd(II)配合物在77K时在2-甲基四氢呋喃中都有很高的发光，发光寿命在毫秒范围内(tau=1.96ms-2.36ms)和波长(Max)=488-499 nm，但在室温下发光寿命缩短到微秒范围(tau=26.7-152.9亩S溶液和57-109.9亩S薄膜)。通过在配体上引入Sigma给体基团进行结构修饰，可以使Pd(II)配合物的量子效率提高8倍以上。特别是，Pd(TZP-3)具有0.228 eV的小的E-ST，并且在聚甲基丙烯酸甲酯薄膜中表现出很强的典型的MADF。铂(II)配合物铂(TZP-2)在二氯甲烷溶液中表现出较高的热稳定性(T-0.5%=440℃)和高量子效率(Phi=50.1%)，其中基于铂(TZP-2)的亮绿色有机电致发光器件(TZP-2)在未经优化的器件结构下获得了峰值EQE为8.7%，最大亮度为28280 cd/m(2)。
The synthesis and photophysical characterization of a series of tetradentate cyclometalated M(tzpPh-O-CzPy-R) complexes and their analogues are reported, where M is palladium or platinum and a tetradentate cyclometalating ligand contains tzpPh (3-phenyl-[1,2,4]triazolo[4,3-a]pyridine) and CzPy (carbazolylpyridine) moieties linked with an oxygen atom. Variations of the sigma-electron-donating group R on the ligand significantly affect the photophysical properties of the complexes. By using the strong electron-withdrawing tzp portion as an acceptor and the carbazole portion as a donor, a series of Pd(II)-based metal-assisted delayed fluorescence (MADF) materials was developed. Electrochemical analysis demonstrates the irreversible reduction process occurs on the tzp ring and the irreversible oxidation process mainly occurs on the metal-phenyl moiety. This is in agreement with the HOMO and LUMO distributions by the DFT calculations, which also shows that the Pt(II) complex has more metal orbital character than those of the Pd(II) complexes. Most of the Pd(II) complexes reported here are highly emissive at 77 K in 2-MeTHF with luminescent lifetimes in the millisecond range (tau = 1.96-2.36 ms) and lambda(max) = 488-499 nm; however, the luminescent lifetimes are shortened to the microsecond range (tau = 26.7-152.9 mu s in solution and 57.0-109.9 mu s in thin film respectively) at room temperature. The quantum efficiency of the Pd(II) complexes can be increased by more than 8-fold through structure modification with sigma-donating groups on the ligand. Especially, the Pd(tzp-3) has a small Delta E-ST of 0.228 eV and exhibits strong typical MADF in PMMA film. The Pt(II) complex Pt(tzp-2) exhibits high thermal stability (Delta T-0.5% = 440 degrees C) and high quantum efficiency (Phi = 50.1%) in dichloromethane solution with tau of 15.8 mu s. The Pt(tzp-2) based bright green OLED achieved a peak EQE of 8.7% and a maximum brightness of 28280 cd/m(2) using an unoptimized device structure.