Color Tuning of Efficient Electroluminescence in the Blue and Green Regions Using Heteroleptic Iridium Complexes with 2-Phenoxyoxazole Ancillary Ligands
Color Tuning of Efficient Electroluminescence in the Blue and Green Regions Using Heteroleptic Iridium Complexes with 2-Phenoxyoxazole Ancillary Ligands
复制标题
DOI：
10.1021/acs.organomet.7b00161
复制
发表时间：
2017-05-08
期刊：
影响因子：
2.8
通讯作者：
Bryce, Martin R.
中科院分区：
文献类型：
--
作者：
Benjamin, Helen;Liang, Jie;Bryce, Martin R.
报道了一种通过双(2-苯基吡啶)(2-(2'-氧苯基1)-2-恶唑啉/恶唑)铱(III)框架功能化来调节磷光配合物发射颜色的合理分子设计策略。已经以良好的产率合成了五种新配合物 (2-6)，并通过循环伏安法、吸收和光致发光研究、时间依赖性密度泛函理论 (TD-DFT) 计算以及配合物 2、4 和 6 的单晶 X 射线衍射研究对其进行了表征。这些配合物的一个有趣的特征是 HOMO 位于 Ir d 轨道和“辅助”配体的苯氧基化部分上，而LUMO位于ppy配体的吡啶环上。先前已经报道了一些含有2'-氧苯基-2-恶唑啉/恶唑辅助配体的其他配合物；然而，到目前为止，还没有对操纵这种不寻常的前沿轨道分布来调整发射特性进行系统的研究。结果表明，将苯基吡啶 (ppy) 配体替换为 2,4-二氟-ppy 会产生 21-22 nm 的蓝移（从 1 到 2 和从 4 到 5），并且在 (2'-氧基苯基)-2-恶唑配体的苯氧基化物环上引入吸电子取代基 (SO2Me、CF3) 会导致进一步的 13-20 nm 蓝移。结合这些功能化，在二氯甲烷溶液中对配合物 5 和 6 进行 lambda(pl)(max) 476 和 479 运行，得到天蓝色发射光。所有配合物的溶液量子产率均在 phi(PL) 0.42-0.73 范围内。观察到的寿命（tau(obs) = 1.52-3.01 mu s）和光谱曲线表明配体中心和 MLCT 激发态混合的磷光。 (TD-)DFT 计算与观察到的配合物的光物理和电化学性质非常一致。使用络合物 2、3、5 和 6 作为发射体，掺杂在 4,4' 双（N-咔唑基）联苯主体中，制造了磷光有机发光二极管，在蓝绿色区域提供有效的发射。值得注意的是，配合物 5 的 lambda(EL)(max) 为 480 nm，最大亮度为 26150 cd m(-2)
A rational molecular design strategy for tuning the emission color of phosphorescent complexes by functionalization of the bis(2-phenylpyridine)(2-(2'-oxypheny1)-2-oxazoline/oxazole)iridium(III) framework is reported. Five new complexes (2-6) have been synthesized in good yields and characterized by cyclic voltamrnetry, absorption, and photoluminescence studies, by time-dependent density functional theory (TD-DFT) calculations, and by single-crystal Xray diffraction studies for complexes 2, 4, and 6. An interesting feature of the complexes is that the HOMO is localized on the Ir d-orbitals and the phenoxylate part of the "ancillary" ligand, while the LUMO is located on the pyridyl ring of the ppy ligands. A few other complexes containing 2'-oxyphenyl-2-oxazoline/oxazole ancillary ligands have been reported previously; however, until now there has not been a systematic investigation into manipulating this unusual frontier orbital distribution to tune the emissive properties. It is shown that exchanging the phenylpyridine (ppy) ligand for 2,4-difluoro-ppy gives a blue shift of 21-22 nm (from 1 to 2 and from 4 to 5), and the introduction of electron-withdrawing substituents (SO2Me, CF3) onto the phenoxylate ring of the (2'-oxyphenyl)-2-oxazole ligand results in a further blue shift of 13-20 nm. Combining these functionalizations gives sky-blue emission with lambda(pl)(max) 476 and 479 run for complexes 5 and 6 in dichloromethane solution. The solution quantum yields of all the complexes are within the range phi(PL), 0.42-0.73. The observed lifetimes (tau(obs) = 1.52-3.01 mu s) and spectral profiles are indicative of phosphorescence from a mixture of ligand-centered and MLCT excited states. (TD-)DFT calculations are in close agreement with the observed photophysical and electrochemical properties of the complexes. Phosphorescent organic light-emitting diodes have been fabricated using complexes 2, 3, 5, and 6 as the emitter, doped in a 4,4'bis(N-carbazolyl)biphenyl host, giving efficient emission in the blue-green region. Notably, complex 5 gives lambda(EL)(max) 480 nm with a maximum brightness of 26150 cd m(-2)