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.

本研究报道了一系列新型高效磷光环金属化铱(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′-双取代2,2′-联吡啶）。该系列配合物均通过核磁共振波谱、高分辨质谱（HRMS）、循环伏安法及紫外-可见光谱完成全面表征；部分化合物还解析得到了晶体结构。此类环金属化配合物在298 K下的溶液及固态中均展现出高效光致发光，具备良好发光强度与色纯度。其发射波长覆盖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/给电子基团（EWG/ERG）特性显著相关。为进一步阐明该类配合物的电子结构，本研究引入循环伏安法作为电化学表征支撑，并结合密度泛函理论（density functional theory, DFT）与含时激发态计算的理论方法开展对照验证与分析。