Highly Phosphorescent Cyclometalated Iridium(III) Complexes for Optoelectronic Applications: Fine Tuning of the Emission Wavelength through Ancillary Ligands

A series of novel, highly phosphorescent cyclometalated iridium­(III) complexes of type [(X2C^N)2Ir­(Q2bpy)]+PF6– (where X2C^N is 2-phenylpyridine or 2-(2,4-difluorophenyl)­pyridine anion and Q2bpy are 4,4′-bifunctionalized 2,2′-bipyridines) is presented. The complexes were fully characterized by means of NMR spectroscopy, high-resolution mass spectrometry (HRMS), cyclic voltammetry, and UV–vis. For several compounds also the crystallographic structures were obtained. The cyclometalates exhibited efficient photoluminescence at 298 K both in solution and in the solid state with good intensity and color purity. The emission wavelength range covered almost the whole visible spectrum and was strongly correlated with the EWG/ERG character of the Q substituent in the ancillary ligand. For further insight into the electronic structure of the complexes, a comprehensive electrochemical support (CV) was introduced, and finally, it was confronted with theoretical background using a density functional theory approach together with time-dependent calculations of the excited states.

本文报道了一系列新型高磷光环金属化铱(III)配合物，其通式为[(X₂C^N)₂Ir(Q₂bpy)]⁺PF₆⁻（其中X₂C^N为2-苯基吡啶或2-(2,4-二氟苯基)吡啶阴离子，Q₂bpy为4,4′-双官能化2,2′-联吡啶）。该系列配合物通过核磁共振波谱、高分辨质谱（high-resolution mass spectrometry, HRMS）、循环伏安法（cyclic voltammetry, CV）以及紫外-可见光谱（UV–vis）完成了全面表征。针对部分化合物，还解析得到了其晶体结构。此类环金属化配合物在298 K条件下，于溶液及固态中均展现出高效的光致发光特性，发光强度优异且色纯度良好。其发射波长范围覆盖了几乎整个可见光光谱，且与辅助配体中Q取代基的吸电子基团（electron-withdrawing group, EWG）/给电子基团（electron-donating group, ERG）特性存在显著相关性。为进一步深入探究该类配合物的电子结构，本文引入了循环伏安法的综合电化学表征，并结合密度泛函理论（density functional theory）方法与激发态含时计算的理论框架开展了对比验证分析。